RU235318U1 - A device for electrically connecting two or more conductors, made in a dielectric heat-sensitive housing - Google Patents

Abstract

The utility model relates to devices for timely detection of defects and prevention of fires, namely to devices for electrical connection of two or more conductors, implemented in a dielectric heat-sensitive housing, at least part of which irreversibly changes color when heated above at least one threshold temperature. The technical result consists in increasing safety during operation of electrical installations, the conductors of which are connected using a device according to the present utility model due to the arrangement of the device for electrical connection (DEC) inside the dielectric housing with a heat-indicating coating. For this purpose, the DEC of two or more conductors includes at least two electrically connected devices for securing the conductors, located inside the dielectric housing, at least part of which is made with the possibility of irreversible color change when heated above a threshold temperature selected from the range of 50-150 °C. 18 clauses, 9 figs.

Description

The field of technology to which the utility model relates

The utility model relates to devices for the timely detection of defects and the prevention of fires, namely to devices for the electrical connection of two or more conductors, made in a dielectric housing, at least part of which irreversibly changes color when heated above at least one threshold temperature.

State of the art

The installation of electrical contacts of current-carrying parts between themselves can be carried out both by non-separable methods, such as welding, crimping, soldering, and by separable methods, which allow the contact connection to be disassembled and reassembled. When selecting and making contact connections, it is necessary to use technical requirements and standards (GOST 10434-82 "Electrical contact connections. Classification, general technical requirements", GOST R 50571.5.52-2011, GOST 22483-2012). The methods of control and testing of contacts and contact connections of electrical equipment and electrical devices are also regulated by regulatory documents, in particular GOST 17441-84 "Electrical contact connections. Acceptance rules and testing methods".

Detachable contact connections are provided by electrical connectors of various types, such as sockets, cable clamps, terminal blocks, connecting buses, branch clamps, etc.

According to GOST 31195.1 “Connecting devices for low-voltage circuits for household and similar purposes”, 2013, a connecting device is a device for the electrical connection of two or more conductors containing one or more terminals and, if necessary, insulation and/or auxiliary elements.

Electrical connection of two conductors can be provided in two ways. In the first case, the conductors to be connected are directly in contact, and the function of the connection device is to provide reliable contact (pressure) between the contact surfaces of the two conductors to be connected. In the second case, the conductors are electrically connected to each other through an electrical connection device (ECD), which contains two or more devices for fastening the conductors electrically connected to each other using a metal conductive part. In the second type of device, there is no direct contact between the conductors to be connected, and the electric current flows through the conductive base to which the conductors to be connected are separately attached.

Despite the more complex technical design, the second type of devices are most widely used in professional energy due to a number of advantages:

a significantly larger contact area is ensured;

contact of each of the conductors is carried out with a special contact pad prepared in advance;

independent clamping of each conductor is ensured;

This device allows you to connect conductors of different shapes and cross-sections, made of different materials (for example, copper and aluminum).

One example of the second type of UES is terminal blocks. The main components of the terminal block include contact elements (metal conductive part), a locking mechanism (nodes for fastening conductors), and an insulating part. The contact elements are metal clamps or brackets that provide pressure of the connected conductor (wire) to the conductive part of the UES. The locking mechanism is usually represented by a clamp, screw or spring mechanism that provides reliable fastening of the wire throughout the entire service life. The insulating part can be made in the form of a coating of the UES elements, can be presented in the form of a case, a base, and can also contain elements for fastening the UES, in particular, on a DIN rail. The implementation of the insulating part in the form of a case provides more convenient and safe operation of the UES, which makes such devices most often used to solve those problems where it is possible to place the UES with a case.

From RU 180661 U1, publication date 20.06.2018, a terminal block is known that contains a dielectric base made of glass-filled polyamide, in the grooves of which screw clamps are rigidly installed, made in the form of square-section sleeves with axial holes for connecting conductors. The conductors are clamped with bolts. The screw clamps are separated from each other by insulating jumpers, the height of which exceeds the height of the sleeves. A protective strip made of insulating material is fixed on the insulating jumpers.

There are many other types of UES, which have the following common features:

reliability of contact connection;

dielectric properties of the insulating part (if any);

ease of installation in electrical installations;

non-flammability;

compactness;

electrical safety of personnel during repair and scheduled work, etc.

According to the type of conductor fastening, it is necessary to distinguish between screw clamps, in which the wires are fastened with a screw (screw terminal blocks, neutral and grounding buses), and spring clamps (Wago type terminals), in which the wires are fixed using a spring mechanism.

By design, UES can be two-contact, that is, intended for connecting two wires, or multi-contact, that is, allowing several wires and/or devices to be combined into one electrical circuit.

As mentioned above, some types of UES (for example, Wago terminals) have an insulating casing that prevents contact between a person or other conductors and exposed current-carrying parts of the UES. The presence of a casing that covers the metal parts under voltage facilitates work with such devices, increases the electrical safety of their operation, and allows them to be serviced even without disconnecting the installation from the power supply. However, all known UES, both with and without an insulating casing, do not allow detecting defects that occur in the contact connection inside the UES and are accompanied by an increase in temperature. Therefore, to ensure the safety of operation of the UES, it is advisable to combine the insulating casing of the conductor connection device with a device for thermal control.

This problem is solved by using a UES with a dielectric thermoinicator case, at least part of which is designed with the possibility of an irreversible color change when heated above the threshold temperature. The purpose of the dielectric thermoinicator case is reduced not only to the insulation of conductors to prevent electric shock to a person and to reduce the risk of a short circuit when the UES comes into contact with non-insulated current-carrying parts of the electrical installation, but also to a number of other auxiliary functions, such as facilitating installation, securing the UES, marking phases, etc.

At the same time, the state of the art does not contain UESs that have an insulating housing with the function of irreversible color change upon heating. The possibility of irreversible color change upon heating allows visually detecting the fact of fire-hazardous heating of UESs during inspections. Fire-hazardous heating of UESs may be associated with the occurrence of defects in contact connections (for example, an increase in the transition contact resistance), the occurrence of an excess load current in the electrical circuit that exceeds the nominal value.

Thermal control of the state of contact connections is an important task when operating electrical equipment. Timely detection of defects in contact connections allows preventing emergency situations that can lead to equipment damage, fires and conflagrations. Excessive heating of electrical connections in most cases is associated with an increase in transient contact resistance, which can occur during operation under the influence of various factors:

reduction of the contact area of conductors;

oxidation of contact surfaces or formation of carbon deposits on them;

galvanic incompatibility of metals of the conductors being connected;

insufficient compression force during installation of the joint;

weakening of pressure during operation;

destruction of the surface of conductors due to aggressive chemical or electrochemical action;

mechanical impact followed by loosening of the contact connection and/or partial removal of the wire from the terminal.

The use of UES provides a convenient and reliable contact connection, but does not completely eliminate its deterioration during operation. To prevent fires due to defects in electrical connections of two or more conductors during operation, it is advisable to carry out their regular thermal monitoring.

Thermal diagnostics of electrical connections can be carried out using a thermal imager or by using thermal indicator devices.

Thermal imaging inspection of the contact connections of the UES, made in a protective housing, is impossible, since the contact connections of such devices are closed for inspection.

Another method of thermal control of contact connections is thermal indicator control. The method is based on the use of irreversible thermal indicators, which are varnishes, paints, stickers or devices that are fixed on the controlled elements and register the facts of exceeding the threshold temperature by changing the color or appearance.

The use of heat-indicating varnishes or paints, on the one hand, allows applying a heat-sensitive coating to a surface of any shape and size, but, on the other hand, has a number of disadvantages that limit their use. These disadvantages include:

impossibility of specifying the threshold temperature;

paint runs off when the threshold temperature is exceeded;

it is impossible to determine the temperature with high accuracy, since the paint is applied to the surface in an uneven layer;

low adhesion;

difficulty in applying paint to surfaces made of non-adhesive materials;

dependence of paint response temperature on the chemical composition of the surface coating.

From the source WO2023060325A1, 20.04.2023, an electrical contact connection with a temperature indicator made of an alloy with a shape memory effect is known. This solution discloses a contact connection unit in which direct contact of the conductors to be connected with each other is realized. In this solution, the contact of two conductors is carried out using a bolt providing pressure between the contacting surfaces, and the essence of the invention is a special temperature-indicating conductive grease that provides the necessary transition contact resistance even when heated. The use of a temperature-indicating grease made of intermetallic compounds reduces the speed and accuracy of determining the excess of threshold temperatures due to the fact that a long-term exposure to a temperature exceeding the threshold is necessary to change the shape of the temperature indicator when heated. The device according to this invention relates to the first type of UES described at the beginning, and does not relate to the invention according to the present utility model due to a different device and the absence of an insulating housing.

For thermal monitoring of the state of contact connections, thermo-indicating stickers are widely used, in which a hot-melt compound is applied uniformly in a thin layer to the base under factory conditions, ensuring good adhesion to the controlled surface. In addition, the thermo-indicating layer can be additionally covered with a polymer film, which protects it from mechanical or chemical impact and does not allow the thermo-indicating compound to flow down when it melts after operation. An example is a thermo-indicating sticker (RU 221997, 06.07.2023), including an adhesive layer, a flexible base and a heat-sensitive material covered with a protective film.

The presented source uses irreversible heat-sensitive materials that change their appearance (color) after exceeding a specified temperature and retain it after cooling. In addition to irreversible materials, reversible compounds that change their appearance only when heated and return to their original color when cooled are also used in the manufacture of thermal indicators. However, to monitor the condition of contact connections, it is necessary to use irreversible indicators that allow you to detect the fact of reaching the threshold temperature at any time during operation, and not just at the time of inspection. This is due to the fact that the temperature of the contact connection depends not only on the presence of a defect, but also on the load current, which changes over time. The need to use irreversible thermal indicators for diagnostics of electrical equipment is disclosed, in particular, in the work of Lvov M.Yu., Lesiv A.V. Thermal indicator control of contacts and contact connections of electrical equipment and power transmission lines. Moscow: NTF "Energoprogress", "Energetik", 2023. P. 62.

Another important characteristic of temperature indicators is the number of controlled threshold temperatures. Single-temperature temperature indicators allow recording the fact of exceeding one specific set temperature. Such a temperature may be, for example, the maximum permissible temperature of the controlled element. Such single-temperature temperature indicator stickers allow promptly informing personnel about the occurrence of an emergency or pre-emergency situation, but do not allow determining the degree and dynamics of defect development over time. Irreversible multi-temperature temperature indicator stickers allow determining not only the fact of exceeding the set temperature, but also the numerical value of the maximum surface temperature to which the controlled element was heated during operation. This allows tracking the dynamics of defect development, providing the ability to compare the heating temperatures of identical parts (units) of equipment, determining the excess temperature, the defect coefficient and making a more accurate conclusion about the presence of a defect.

The prior art discloses the use of flexible stickers with color temperature indicators installed near the contacts for fastening the elements of electrical equipment in an electrical installation (RU 74211, 10.01.2007). Such a solution increases the operational reliability of the electrical installation by creating simple means of continuous visual monitoring of the state of bolted and plug-in contact connections of the elements without removing the load. A combination of reversible and non-reversible color temperature indicators is used as heating indicators. The patent does not disclose on which particular element of the electrical equipment the temperature indicator sticker is located. It should be noted that it is impossible to attach commercially available temperature indicator stickers to the UES due to the small size and complex shape of the UES surface. A separate difficulty is ensuring a tight fit of the heat-sensitive element of the sticker to the UES surface, which leads to a decrease in the accuracy, speed and reliability of temperature indicator control.

The UES manufactured by industry are not adapted to the placement of temperature indicator stickers, since they do not contain suitable and sufficient space for mounting stickers. For the most compact organization of electrical connections, UES manufacturers strive to minimize their size, leaving no possibility of installing additional temperature control devices near the electrical connection. At the same time, with distance from the heating point, i.e. the device for fixing the conductor, the temperature decreases significantly due to heat dissipation. The placement of a temperature indicator sticker on the wire outside the UES will be aimed at monitoring the thermal state of the wire, and not the contact connection.

The insulating housing of the UES is designed to increase operational safety by preventing human contact with live parts and the risk of short circuit when the UES comes into contact with non-insulated elements of the electrical installation. The use of the UES with an insulating housing, which allows for the detection of fire-hazardous heating due to irreversible visualization of heating, allows for a significant increase in the operational safety of electrical installations due to the possibility of timely visual detection of defects and their elimination.

Despite the large selection of UES, as well as methods of temperature control of electrical connections, in particular using thermal indicators, different both in the mechanism of action and in the design, there is a need for UES, having the ability to irreversibly register the fact of exceeding the threshold temperature for the timely detection of defects in contact connections, in which the conductive part is covered by a dielectric housing, at least part of which is made with the ability to irreversibly change color when heated above the threshold temperature.

Terms, definitions and abbreviations used in the description of the utility model

The following terms, definitions and abbreviations used in the description of this utility model are intended for a better and more precise understanding of this utility model, but do not limit this utility model to the specified wording.

"Electrical connection device" is a device for electrically connecting two or more conductors, containing a conductive part, devices attached to it for securing two or more conductors, such as buses, wires, cable lugs, etc. The device may be partially covered with insulating materials and/or contain auxiliary elements, in particular, an insulating part. The most common ECDs include, in particular, screw terminal blocks and spring terminal blocks. The claimed utility model relates to ECDs made inside an insulating housing. That is, such ECDs, the non-insulated parts of which are protected from contact by a special housing.

"Conductor" is an element of a cable product (current-carrying core) intended for the passage of electric current (GOST 15845-80 "Cable products. Terms and definitions", 01.07.1981). In preferred embodiments of the utility model, a conductor may be understood as a metal, in particular a wire.

"Wire" is a cable product containing one or more twisted wires or one or more insulated cores, over which, depending on the installation and operating conditions, there may be a light non-metallic sheath, winding and (or) braiding made of fibrous materials or wire, and not intended, as a rule, for laying in the ground (GOST 15845-80 "Cable products. Terms and definitions", 01.07.1981). As applied to this utility model, the concept of "wire" also includes non-insulated metal current-carrying wires (cores), one or more insulated cores twisted together, enclosed in a common sheath (cables).

In accordance with GOST 14312-79 "Electrical contacts. Terms and definitions", a "contact connection" or "electrical connection" is understood to mean a contact of an electrical circuit intended only for conducting electric current and not intended for switching an electrical circuit during a given operation of the device.

“Contact resistance (contact connection)” according to GOST 14312-79 means the electrical resistance of the contact zone, determined by the effective contact area and equal to the ratio of the voltage drop across the contact transition to the current through this transition.

"Device (equipment) for fastening conductors" - a device for connecting (fixing) conductors to the UES, which may be a screw, spring or other clamp to ensure a detachable or non-detachable contact connection. With the help of this device, electrical contact of the conductor with the conductive part of the UES is ensured.

The term "self-diagnostics", in the case of the claimed utility model, means the ability of the UES to diagnose defects in contact connections located inside the UES housing, without using additional devices. In the case of the claimed utility model, at least part of the dielectric thermal indicator housing of the UES changes color when a defect occurs associated with exceeding the threshold heating temperature.

"Thermoelement" includes a material or article made with the ability to change appearance upon reaching a threshold temperature. In the context of the present utility model, a thermoelement is understood to be a part of the housing made with the ability to irreversibly change color upon heating above the threshold temperature. The thermoelement may include one or more substances, as well as one or more different materials. Upon reaching the threshold temperature, the thermoelement may change its color or its transparency. In the latter case, the visual effect of the device's operation may be due to the manifestation of the color of the substrate located under the thermoelement. A change in the color or transparency of the thermoelement upon reaching the threshold temperature may occur due to a chemical reaction, melting of one or more substances, other phase transitions, as well as more complex processes. The thermoelement may also additionally include solid or gaseous inclusions located in the volume of the heat-sensitive component; support elements made in the material of the substrate and/or protective layer; an absorbent material onto which the heat-sensitive component is applied.

In the present utility model, it is preferable to use a thermoelement whose action is based on a change in appearance, in particular, on a change in transparency, when melting one or more substances, preferably distributed in a polymer binder. However, the utility model is not limited to the use of only such components, and thermoelements can be made using a different principle of action.

"Thermal indicator" is a material or device that changes its appearance (in particular, color) when heated above one or more threshold temperatures. In the case of the claimed utility model, the role of the thermal indicator is performed by at least part of the dielectric thermal indicator housing, in particular, due to the presence of a thermoelement. The following terms are disclosed using the concept of thermal indicator, however, in the case of the claimed utility model, the role of the thermal indicator is performed by part of the housing of the UES containing the thermoelement.

Single-temperature thermal indicators include thermal indicators that have one thermal element or several thermal elements that are triggered when one threshold temperature is reached.

Multi-temperature thermal indicators include thermal indicators that have several thermal elements that differ in response temperature (threshold temperature).

The term "irreversible" defines thermal indicators which, after heating to the response temperature, visually change their appearance, in particular their colour, in such a way that after cooling below the response temperature their appearance does not return to a form that is visually indistinguishable from the original.

"Threshold temperature" is the minimum value of the heating temperature of a thermal indicator during the time required to achieve an equilibrium (not changing over time) state, at which the appearance of the thermal element of a given thermal indicator changes.

The "color transition of the thermoelement" is understood to mean the change in color of the thermal indicator when the thermoelement is triggered, and when describing the color transition, the color before the triggering is first indicated, and then after. For example, about a thermoelement that is initially painted white (opaque state), and after triggering goes into a transparent state, revealing the color of the black base located underneath, it is said that its color transition is white-black. In some cases, either on the thermoelement or on the base located underneath the thermoelement, inscriptions may be applied, indicating, for example, the numerical value of the threshold temperature of the thermoelement triggering, or signal symbols.

A change in the appearance of a temperature indicator or thermoelement that occurs solely as a result of heating to any of the possible threshold temperature values is called "operation". In the context of the description of this utility model, the operation of a temperature indicator is preferably associated with an increase in transparency achieved by melting a substance or group of substances that are part of the thermoelement.

A change in the appearance of a temperature indicator, in particular the colour and/or transparency of the thermoelement, which occurs as a result of an external influence other than heating the temperature indicator above the corresponding threshold temperature values, is called a “false triggering of the temperature indicator”.

"Response time" or "response speed" - the maximum time required for the color transition of the temperature indicator (dielectric temperature indicator housing) from the initial to the triggered state after heating to the upper response temperature value, taking into account the specified accuracy of recording the excess of the threshold temperature. As applied to this utility model, the response speed of the dielectric temperature indicator housing is no more than 5 seconds, preferably no more than 2 seconds.

In relation to this utility model, the following method for determining the response time is used.

The product is pre-conditioned in a thermostat at a temperature 5°C below the response temperature and quickly transferred to a tank with an inert liquid medium (e.g. kerosene) pre-heated to the upper value of the product response temperature. The time during which the complete color transition of the heat-sensitive part of the housing occurs is determined. If the product contains several heat-sensitive elements, the test is carried out separately for each temperature.

The term “accuracy of recording the excess of the threshold temperature” refers to the boundaries of the range of temperature values that meet the following conditions (1) - (3):

(1) until the threshold temperature is reached minus the specified accuracy value, the dielectric temperature indicator body does not change its appearance (in particular, the temperature-sensitive component remains opaque to at least part of the visible light);

(2) when the threshold temperature is exceeded, taking into account the specified accuracy, the dielectric temperature indicator body is triggered, in particular, with an increase in transparency, achieved by melting one substance or a group of substances included in the composition of the temperature-sensitive component, and acquires an appearance different from the original;

(3) in the case of using a heat-sensitive component in which the change in appearance upon reaching a threshold temperature is associated with an increase in transparency achieved by melting one substance or a group of substances included in its composition, the exact value of the phase transition temperature of the melting of the substance is within a specified range and is not further established.

The accuracy of recording the excess of the threshold temperature determined by this utility model is preferably no more than 5°C, most preferably no more than 2°C.

The term "gas-filled hot-melt material (GFTM)" defines a heat-sensitive component of a dielectric housing that includes a solid phase or phases, as well as a gas phase located in cavities of the solid phase. At least one of the solid phases of the GFTM, called the "hot-melt phase", is designed to melt when heated to a threshold temperature. The gas phase is predominantly distributed uniformly throughout the GFTM, with most of the pores communicating with each other, providing the ability to freely distribute and exit the gas when the material is heated and/or melted. The gas pressure inside the pores may be less than atmospheric pressure, equal to atmospheric pressure, or greater than atmospheric pressure.

The composition of the thermal-melting composite material in the form of a solid phase may additionally include particles of a solid substance with a melting point above the threshold, the strength of which predominantly exceeds the strength of the thermal-melting phase; polymers that completely or partially cover the thermal-melting phase; as well as other inclusions. Such substances or inclusions are used to increase the mechanical strength of the thermal-melting composite material.

The hot-melt phase contains the "active (main) substance of the thermal melting point" - this is a substance, in particular an organic substance, that determines the melting point of the thermal melting point (the threshold temperature of the thermal indicator). The mass content of the main substance in the structure of the thermal melting point predominantly exceeds the content of other components of the thermal melting point. The term also refers to a mixture of such substances.

The term "organic substances" restricts the class of chemical substances that contain carbon atoms bonded to atoms of other chemical elements, excluding metal carbides, metal and ammonium carbonates, and carbon oxides.

The term "gas phase" by default refers to the pores filled with gas and located inside the gas-filled gas-filled medium. The gas phase may be air, nitrogen, inert gases or other substances that are in the aggregate state of "gas" under the operating conditions of the UES.

The term "share of gas phase in the gas-phase flow module" means the ratio of the volume of pores inside the gas-phase flow module to the total volume of the gas-phase flow module, or the ratio of the area of sections filled with gas to the total area of the gas-phase flow module section in one of the sections. As applied to the present utility model, the share of gas phase can be determined by one of the methods listed below.

The first method involves scanning electron microscopy of the surface of the GTPM section using software that allows calculating the total area of the external surface of solid particles of the sample and their agglomerates in the section. The area of sections filled with gas is calculated by subtracting the total surface area of solid particles and their agglomerates from the area of the analyzed section. To determine the proportion of the gas phase, the obtained value of the area of sections filled with gas is divided by the area of the analyzed section. Measurements are carried out on 5-7 sections of the GTPM and the average value is calculated.

The second method is based on the application of the X-ray microtomography method. Sample preparation is carried out in a manner similar to the first method. A section of the gas-phase microtomography sample of known volume is analyzed using a laboratory digital X-ray tomograph with software that allows calculating the percentage of gas in a given volume of the sample. Measurements are taken of 5-7 sections of the material, obtaining the average value of the proportion of the gas phase, expressed as a percentage.

Any of the methods for determining the gas phase fraction can be applied to finished products containing the GTPSM, such as UES. During sample preparation, it is permissible to cut out a uniform section of the dielectric temperature indicator case and remove the protective layer from it so as to ensure the safety of the GTPSM.

In the context of the description of the GTPM, the term "phase" should be understood as a homogeneous part of the GTPM, separated from the other parts by a visible interface, on which some characteristics of the phase, such as density, composition, optical properties, change abruptly. In this case, the set of individual homogeneous parts of the system, possessing identical properties, is considered a single phase.

The composition of the thermal melting material may additionally include particles of a solid substance with a melting point above the threshold, the strength of which predominantly exceeds the strength of the thermal melting phase, as well as other inclusions.

The term "structure of the gas-phase-filled HTPM" defines the spatial arrangement of solid particles and pores filled with a gas phase in a HTPM sample. The structure of the HTPM defines its physical, optical and mechanical properties. When the threshold temperature is reached, at least one of the solid phases of the HTPM melts. During the melting process, the structure of the HTPM changes, i.e. the spatial arrangement of particles and/or volumes of individual phases of the material, their size and shape. The destruction of the structure may include the following stages: melting of the surface of the HTPM particles, their compaction, reduction of the pore size inside the HTPM and the surface area of the "gas-solid" phase interface, fusion of particles up to their complete fusion and formation of a monolithic layer (melt) or a single phase. The process of destruction of the HTPM structure is accompanied by an irreversible decrease in the volume fraction of the gas phase inside the HTPM. The fraction of the gas phase in the material obtained after the operation of the heat-sensitive component is less than in the initial state of the HTPM.

By "binder", when describing a heat-sensitive component, in particular with a HTPM, is meant a material or substance, preferably a high-molecular organic compound, which provides the ability to fix solid particles relative to each other. A binder of a solid hot-melt phase, in particular, increases the strength of the heat-sensitive component and reduces its abrasion, and can also provide fixation of the hot-melt phase to the dielectric base.

By "hermetic protective layer" is meant a protective layer that is impermeable to air and water at atmospheric pressure and in the absence of mechanical impact, made without gaps or holes, and tightly connected to the base by welding or gluing in such a way that the joint is also impermeable to air and water at atmospheric pressure and in the absence of mechanical impact.

The term "absorbent material" refers to a material capable of accepting and retaining in any way a molten heat-sensitive fusible component, such as a melt of an active substance or a heat-melting phase. Retention may occur due to wetting, adsorption, absorption, penetration of the melt into pores or other internal cavities of the absorbent material. A special case of an absorbent material is a "sorbent material". As an absorbent material within the framework of the present utility model, it is possible to use a "porous material", which is a solid material containing in its volume free space in the form of cavities, channels or pores and characterized by a developed surface. The main parameters of porous materials are porosity, pore size, pore size distribution and specific surface. With regard to the claimed utility model, it is preferable to use dielectric "microporous materials" containing pores with a diameter of less than 2 μm.

The term "sorption" should be understood in the most general sense as the absorption of various substances by a solid body. The substance being absorbed is called a "sorbate", the absorbing solid or liquid is called a "sorbent". Within the framework of this utility model, the sorbate is a melt of a heat-sensitive component, i.e. a liquid, and the sorbent is various solid absorbent materials.

“Absorption” is preferable as a special case of sorption, as a result of which the sorbate is absorbed by the entire volume of the sorbent with an increase in the mass of the sorbent with an insignificant increase in its volume and changes in its physical, especially strength, characteristics.

The term "support element" or "support element (SE)" defines an arbitrary element located in the region of a temperature-sensitive component that has a melting point greater than the response temperature of the given temperature-sensitive component and that can take on a large part of the mechanical stress acting on the temperature-sensitive component in the transverse direction, thereby preventing significant destruction of the structure of the temperature-sensitive component.

The term “defect” indicates the non-compliance of the control object with the requirements established by the documentation, at least for one indicator.

"Defectivity factor" is the ratio of the measured temperature rise of the contact joint to the temperature rise measured on the entire section of the busbar or wire, located at a distance of at least 1 m from the contact joint.

"Excess temperature" is the excess of the measured temperature of the control object over the temperature of similar units of other phases located in the same conditions.

The term "fire-hazardous heating" refers to the heating of an element of an electrical installation to a temperature at which there is a risk of ignition of one or more materials from which the element is made.

The term "flexible" refers to materials that have the ability to change their shape under external influence in such a way that after returning to their original shape, their functional properties remain the same.

The term "elasticity" refers to the ability of a material or product, when bent around a cylindrical surface, to repeat its shape without losing its functional properties.

The term “dielectric” means the property of a material to withstand an electrical voltage applied to it, while the minimum electric field strength at which breakdown of the dielectric material occurs must exceed the electrical strength of air.

The essence of the utility model

The objective of the utility model is to create a device for electrically connecting conductors, made in a dielectric temperature indicator housing, allowing visual registration of the fact of heating of the device above the threshold temperature and warning about the occurrence of a defect, the development of which can lead to combustion and fire.

The technical result of the claimed utility model consists in increasing safety during the operation of electrical installations, the conductors of which are connected using a device according to the present utility model, due to the location of the UES inside a dielectric housing with a thermal indicator coating.

The technical result is achieved by means of a device for electrical connection (DEC) of two or more conductors, including at least two electrically connected devices for securing conductors located inside a dielectric housing, at least part of which is designed with the possibility of changing color when heated above a threshold temperature selected from the range of 50-150°C.

The UES of two or more conductors are widely used in the organization of contact connections. They have proven themselves as reliable and functional means of organizing conductive elements in electrical installations, panels, junction boxes, etc.

The claimed utility model relates to a certain type of UES, in which the conductors are connected through a conductive part, wherein each conductor is connected to the conductive part separately, and there is no direct contact between the conductors being connected. In other words, in the UES according to the present utility model, the first conductor being connected contacts the conductive part of the device using the first device for securing the conductors. And separately, using the second device for securing the conductors, the second conductor being connected contacts the same conductive part. Thus, in the claimed device, the electric current between the conductors being connected flows through the conductive part.

The presence of a dielectric housing ensures increased safety during operation of electrical equipment by reducing the risk of electric shock to personnel when touching the UES, as well as the occurrence of a short circuit when the UES comes into contact with non-insulated parts of the electrical installation. In addition, the dielectric housing allows for installation or repair work to be carried out without removing voltage from the electrical installation.

The use of a dielectric housing, at least part of which is designed with the possibility of an irreversible change in color when heated above the threshold temperature (the function of an irreversible thermal indicator), allows recording the fact of exceeding the threshold temperature. This ensures self-diagnosis of the UES, namely, allows visually detecting the fact of a defect in the contact connection or exceeding the rated load current.

The importance of temperature control in the area of contact connections to improve the safety of electrical equipment operation has already been discussed in the section "State of the art", where existing methods for solving the problem were also covered, including the use of temperature indicators. Timely detection of defects in contact connections allows preventing emergency situations that can lead to equipment damage, fires and conflagrations.

Thus, all the features of the declared utility model are aimed at increasing safety during operation of electrical equipment.

In this device, heat-sensitive components are placed on the housing in factory conditions during its manufacturing process. The UES elements are manufactured taking into account the need for effective placement of both the dielectric housing itself and its heat-sensitive components, to ensure the declared accuracy of heating registration and the visibility of the response, when implementing visual thermal control. Thus, the UES is immediately installed in the electrical network, which contains a dielectric housing made with the possibility of implementing visual thermal control.

It is worth noting that the installation of additional temperature-indicating devices on the UES is impossible in most cases due to the lack of space required for their placement. When applying heat-sensitive paint, its layer will be uneven, and the paint itself can interact with the contacting surface, flow down when triggered and reduce the safety of the UES operation. The installation of additional temperature-indicating stickers is associated with mechanical impact on the electrical connection and its loosening. The listed factors reduce the safety of the operation of electrical equipment, the quality of the electrical connection of conductors and the quality of temperature-indicating control.

The threshold temperatures of the dielectric thermo-indicating body are selected from the range from 50 to 150°C, which is due to the maximum permissible values of heating temperatures established in the regulatory documentation for the operation of electrical installations. The value of 50°C is the minimum heating temperature of contact connections during thermo-indicating control, indicating the onset of defect development. 150°C is the highest value of the fire-hazardous heating temperature of contact connections coated with silver, nickel or other metals.

Thus, the entire set of features characterizing the device of electrical connection of two or more conductors with a dielectric thermal indicator housing ensures the solution of the set task and the achievement of the specified technical result.

In preferred embodiments of the utility model, the minimum distance from the dielectric temperature-indicating housing to the device for fixing the conductors is no more than 3 mm. This is due to the fact that the air located between the devices for fixing the conductors and the housing has low thermal conductivity. For timely and reliable registration of exceeding the threshold temperatures in the UES, especially in the event of short-term heating of the conductive parts caused by peak (emergency) loads, or, for example, short-circuit currents, it is necessary to warm up the air space between the housing and the heating conductive part, as well as the housing itself and its heat-sensitive areas. Therefore, the creation of an air gap of great thickness (more than 3 mm) will lead to heat losses, due to which the thermal control will not be accurate.

When a contact connection defect occurs, heat is released at the point of contact of the conductor with the UES, with subsequent heat transfer to the conductive part, and as it moves away from the heating point, the heat quickly dissipates. At the same time, the accuracy of overheating registration, in accordance with current regulatory documents, should not exceed 10°C. The distance at which the device temperature decreases by 10°C can be roughly estimated based on the Fourier law of thermal conductivity and the Newton-Richman law.

According to Fourier's law of thermal conductivity, the heat flux removed through a unit area per unit time will be proportional to the thermal conductivity coefficient of the material and the temperature gradient:

where X is the specific thermal conductivity coefficient, and ΔT is the change in temperature over a length Δl.

Let us assume that this same heat flow is dissipated into the environment in accordance with the Newton-Richmann law in direct proportion to the difference between the temperature of the device material and the temperature of the surrounding air:

where α is the heat transfer coefficient between the device and the environment (air), T is the temperature of the device, T _ambient is the ambient temperature.

From these relationships, equating the two heat flows, we obtain the following relationship for the length:

As a typical value of the heat transfer coefficient, we take α equal to 3 W/( ^m2 *K). We take the thermal conductivity coefficient for the material of the conductive part of the device equal to 45.4 W/(m*K). We assume the ambient temperature to be 20°C, and the temperature of the device for fastening the conductors to be 70°C. With these parameters, the temperature gradient equal to ΔT=10°C will correspond to a length of Δl≈30 mm.

However, when placing sections that change color when reaching the threshold temperature on the dielectric housing of the UES, it is necessary to take into account the low values of thermal conductivity of the housing material. In this case, the thermal conductivity coefficient of the material of the dielectric part of the UES can be taken equal to 0.2 W/(m*K) (the average value of the thermal conductivity coefficient for polymeric materials, composite materials and ceramics). Then, with the same difference in temperatures of the device for fixing the contact joint and the environment, the value of Δl will be approximately equal to 13 mm.

Based on the averaging of the parameters of the UES, their installation locations, the environments in which they are used, the range of recorded temperatures, etc., known to the authors based on the conducted research and experience in this field of technology, the authors of the present utility model have experimentally established that it is preferable to ensure the accuracy of recording the excess of threshold temperatures by placing at least a part of the dielectric housing, made with the possibility of changing color when heated above the threshold temperature, at a distance of no more than 5 mm from the device for securing the conductors.

Preferably, the components of the dielectric housing part, designed with the possibility of an irreversible color change when heated above the threshold temperature, are dielectrics, preferably have an electric strength of at least 3 kV/mm both before and after heating above the threshold temperature. Increasing the electric strength increases the reliability of operation and reduces the risk of an electric arc during overvoltage and short circuit.

The production of the temperature-indicating dielectric housing can be carried out by any known methods. In particular, the temperature-sensitive pigment can be uniformly mixed into the housing material at the stage of its production and molding. However, in preferred embodiments, the temperature-sensitive properties of at least part of the housing are provided by a thermoelement placed on the housing surface and made with the possibility of changing color when heated above the threshold temperature. Such a thermoelement can be applied to the front surface of the housing. Also, if the housing is transparent, the thermoelement can be applied to the back surface of the housing, and with such an arrangement, the thermoelement is in close proximity to the devices for fixing the conductors. Therefore, when heating the controlled elements, heat transfer to the thermoelement will be more effective than in the case where the thermoelement and the heated unit are separated by a dielectric housing.

It is preferable that the thickness of the thermoelement be 0.1-3.0 mm. Such a thickness of the thermoelement allows achieving a balance between such characteristics as mechanical strength and response speed.

The achievement of the technical result associated with the possibility of servicing and repairing an electrical installation under voltage without using special devices, in preferred embodiments is additionally ensured by using a dielectric housing that covers at least 70% of the area of the devices for securing the conductors. This minimizes the area of open conductive parts, contact with which is unsafe for humans.

In preferred embodiments, the UES is designed with the possibility of electrically connecting wires and using in distribution boards with a voltage of up to 1000 V, which is achieved by using UES designs known from the prior art.

In case of using a thermoelement, it can have a layered structure including a polymer dielectric layer, preferably made of halogen-containing polymers, most preferably of polyvinyl chloride, at least one substance or mixture of substances having a melting point near the threshold temperature and an electric strength of at least 3 kV/mm both before and after melting, a protective layer, at least part of which is transparent. This embodiment is similar to using a sticker, however, since the placement on the thermoelement body is carried out at the manufacturing plant at the stage of manufacturing the UES, this allows for its highest quality and most accurate placement. This also allows for increased speed, accuracy and reliability of response. In addition, with factory application, it is possible to ensure the use of films (substrates) of minimum thickness, which cannot be applied under installation conditions. In addition, factory application of the thermoelement prevents loosening of the electrical connection when installing an additional indicator device on an already mounted UES.

Regardless of the method of manufacturing the thermal indicator dielectric housing of the device, the time of color change of this part of the device according to the present utility model when heating the device, preferably when heating at least one contact connection of the device, above the threshold temperature is no more than 5 seconds. The specified speed is necessary for recording short-term heating caused by peak (emergency) loads, or, for example, short-circuit currents. The response speed of no more than 5 seconds, and preferably no more than 2 seconds, can be ensured, for example, due to the operating principle of thermoelements, in which the action of the heat-sensitive component is based on melting the active substance.

The accuracy of recording the excess of the threshold temperature determined by this utility model is preferably no more than 5°C, most preferably no more than 2°C, which is also ensured, among other things, by the principle of operation of the thermoelements.

In preferred embodiments of the utility model, the dielectric strength of the dielectric temperature indicator housing is at least 3 kV/mm, preferably at least 5 kV/mm.

When using a thermoelement in some variants of the utility model, it can be covered with a protective film or polymer varnish that is transparent to at least part of the visible light, which additionally protects it from external environmental influences, humidity, UV radiation and mechanical damage. The protective film also additionally increases the service life of the device and prevents the thermoelement components from flowing when the threshold temperature is exceeded. Preferably, the material of the protective film contains halogen atoms, mainly chlorine atoms, and is polyvinyl chloride, most preferably cast polyvinyl chloride. The halogen-containing protective film also provides a dielectric strength of at least 5 kV/mm and is resistant to ignition.

In particular embodiments, information elements may be applied to the surface of the dielectric housing and/or transparent protective layer (if any), which include information for marking the elements of electrical equipment or color marking of phases. In particular, information elements applied to the front surface of the polymer film and/or transparent protective layer may include inscriptions containing color, letter, digital or alphanumeric marking information. In one case, information elements may contain information about the end date of the device's service life.

Providing at least part of the dielectric housing with temperature-indicating properties can occur using temperature-sensitive components that differ in the operating principle. When selecting the type of temperature-sensitive component, it is necessary to take into account the features of each of them. The prior art knows temperature-sensitive components based on a chemical reaction of the substances included in their composition, which begins when a certain temperature is reached or when they melt. Long-term exposure of temperature-sensitive components based on a chemical reaction at a temperature slightly lower than the threshold value can lead to their premature operation, since the degree of chemical reaction is determined not only by temperature, but also by time. In this regard, such components can be used in UES with a short service life, for example, for temporarily used UES.

There are temperature-sensitive components based on the mechanical destruction of one of the temperature-sensitive components when a threshold temperature is reached. As a rule, such temperature-sensitive components are large in size and can only be used in large UES.

The most common are heat-sensitive components based on phase transition, mainly melting, due to their high accuracy, response speed and ability to retain their original appearance for an unlimited time at a temperature slightly below the threshold. Known from the prior art, heat-sensitive components based on phase transition can be classified by the operating principle that ensures a change in the appearance of the device: a change in transparency during melting, dissolution of dyes in the melt of the heat-sensitive material or absorption of the melt of the heat-sensitive component into a porous substrate.

Heat-sensitive components, in which the change in appearance occurs due to the dissolution of a solid dye in a melt of a fusible substance, usually have a short service life due to solid-phase diffusion of the dye.

The penetration of the molten component into the porous substrate, on the one hand, provides high contrast of the color transition, since the color of the substrate may differ from the original color of the solid hot-melt component, but on the other hand, the crystallization of the substance in the pores of the substrate during cooling can lead to reversibility (returnability) of the color indication.

The use of heat-sensitive components in the device, the operating principle of which is an irreversible increase in transparency due to melting, has a number of advantages over the operating principles described above:

high response accuracy due to the use of purified stable substances with a narrow melting point range;

ensuring irreversibility of operation (even if the triggered heat-sensitive component is kept at a temperature below the threshold for a long time);

high hiding power of the heat-sensitive layer, allowing the production of heat-sensitive devices of small thickness;

visibility of the triggered device, ensured by the contrast of the color transition (for example, white-black) in the case of using a housing or substrate of a certain color, in particular, black;

the possibility of simplifying the assessment of the condition of equipment during inspections due to the appearance, when a heat-sensitive component is triggered, of a special danger sign or symbol (for example, a flame sign, an exclamation mark, etc.) located on the body or substrate (if used) under a layer of hot-melt material;

ensuring the possibility of registering local overheating due to the fact that only that area of the heat-sensitive component that is heated above the threshold temperature is subject to melting, while the appearance of the remaining areas of the heat-sensitive component is preserved;

high response speed due to the use of a thin layer of heat-sensitive component; - long service life.

Based on this, in the present utility model it is preferable to use a heat-sensitive component whose action is based on a change in color due to melting, in particular, on a change in transparency during melting. However, the utility model is not limited to the use of only such components, and they may have a different principle of action.

When heat-sensitive components, the action of which is based on a change in transparency, are triggered, the color of the part of the housing or film (if any) located underneath them appears. If heat-sensitive components are applied to the film, the same color transition or different color transitions may occur when each of them is triggered, depending on the coloring underneath the corresponding component. It is preferable to paint the housing or film (if any) underneath all components black. In this case, in the initial state, all components are preferably white, thus, upon triggering, a visually observable “white-to-black” transition is ensured.

The use of this type of heat-sensitive components ensures, including in the case of local heating, the possibility of changing the color only in the area where the threshold temperature was exceeded, while maintaining the original appearance of other areas of this TE that were not subjected to heating. In this case, the boundary of the heated area is determined with high accuracy, mainly 1-2 mm. Also, to enhance this feature, it is preferable to use gas-filled hot-melt materials (GFTM), known from the prior art (RU 220377 U1, 20.06.2023 and RU 221997 U1, 06.07.2023).

In case of using a thermoelement in some variants of the utility model, it can be located in a recess made in the housing. The location of the thermoelement in this way has a number of advantages:

protection of the thermal element from mechanical damage and abrasion;

preventing the thermoelement or its components from flowing down during melting (operation);

increasing the response speed of the thermoelement by reducing the thickness of the housing in the area of the thermoelement.

The UES can be designed with the possibility of being mounted on a DIN rail, in particular, it can have additional fastening elements made of insulating material.

In some embodiments, the devices for fastening the conductors may be made in the form of a screw connection, and the UES itself may be a screw terminal block (Fig. 2), a screw terminal, or a screw clamp. In other embodiments, the devices for fastening the conductors are made in the form of a spring connection, and the UES itself may be a spring terminal block (Fig. 1).

When using a thermoelement, it can be located on the housing either at the same distance from at least two devices for fastening the conductors, or on at least two sections of the housing, each of which is located near the corresponding device for fastening the conductors. In the first case, it is possible to control the thermal state in the area of at least two devices for fastening the conductors, using one thermoelement located on one section of the housing, changing color when heated above the threshold temperature (Fig. 1b). In the second case, the housing contains at least two thermoelements, each of which is located on sections not connected to each other, changing color when the threshold temperature is reached, and each of which is located near the corresponding device for fastening the conductors (Fig. 1d). Thus, each of such sections is located with the possibility of monitoring the thermal state in the area of the corresponding device for fastening the conductors.

When placing at least two thermoelements on at least two sections of the housing, each of which is located near the corresponding device for fastening the conductors, it is possible to use thermoelements having different threshold temperatures. In this case, it is preferable that the thermoelements are placed in such a way that at least one group of sections of the housing on which at least two thermoelements are located is located at the same distance from at least two devices for fastening the conductors. Such an arrangement of the thermoelements makes it possible to establish the cause of heating and localize the defect.

In preferred embodiments, different thermoelements have different threshold temperatures (Fig. 1a). Thus, each of the groups of thermoelements is arranged with the possibility of monitoring the thermal state in the area of the corresponding device for fixing the conductors and the possibility of comparing the temperature of the greatest heating of different contact connections, including determining the stage of defect development and the dynamics of its development over time. In this case, it is preferable that the threshold temperatures of the said sections differ by at least 5°C.

Brief description of the drawings

The utility model will be better understood from the description, which is not limiting in nature and is provided with references to the attached drawings, which show:

Fig. 1 - Version of the UES in the form of a spring terminal block: 1a - general view of the device; 1b - bottom view of the UES, with thermoelements placed on the housing, wherein the thermoelements have different threshold temperatures; 1c - bottom view of the UES, with a group of thermoelements placed on the housing, when two thermoelements are triggered in the area of all contact connections; 1g - bottom view of the UES, with thermoelements placed on the housing, wherein the thermoelements have the same threshold temperatures; 1d - bottom view of the UES, with thermoelements placed on the housing, when a thermoelement is triggered in the area of one contact connection.

Fig. 2 - A variant of the implementation of the UES in the form of a screw terminal block, the body of which is completely covered with a thermoelement: 2a - in the initial state, 2b - after heating one of the contact connections above the threshold temperature.

Fig. 3 - Side view of a section of a screw terminal block, closed by a housing, in the area of two devices for securing conductors that form an electrical connection, with a thermoelement made in the form of a single zone, located on the front surface of the housing next to the devices for securing conductors with absorbent material and covered with a protective layer on top.

Fig. 4 - Side view of a section of a screw terminal block, covered by a transparent housing, in the area of two devices for securing conductors that form an electrical connection with a thermoelement located on the rear surface of the housing in a recess using a dielectric material.

Detailed description of the drawings

Fig. 1 shows an embodiment of the UES in the form of a spring terminal block. 1a is a general view of the UES, which shows the insulating housing 1, the lever of the spring mechanism 2, the holes for fastening (clamping) the conductors 3. 1b is a view of the UES from below, with a group of thermoelements 4 located on the housing 1, wherein the thermoelements 4 have different threshold temperatures. In this case, the device is designed with the possibility of multi-temperature thermal indicator monitoring of current-conducting parts 6, namely monitoring the excess of three threshold temperatures. Information elements 5 are also applied in the area of the thermoelements, showing the numerical value of the threshold temperatures. 1c is a view of the UES from below, with a group of thermoelements 4 located on the housing 1, upon operation 14 of two thermoelements 4 in the area of all contact connections. In this case, it is shown that the thermoelements in the initial state are white, and when the corresponding threshold temperature is exceeded, they change color to black. 1g - bottom view of the UES, with thermocouples 4 placed on the housing 1, wherein thermocouples 4 have the same threshold temperatures, indicated on the information elements 5. 1d - bottom view of the UES, with thermocouples 4 placed on the housing 1, when the thermocouple is triggered in the area of one contact connection. In this case, it is shown that the thermocouples in the initial state are white, and when the corresponding threshold temperature is exceeded, they become transparent, revealing the color of the housing. If the housing is transparent, then the color of the conductive part 6, located under the housing in this area, is revealed.

Fig. 2 shows a variant of the implementation of the UES in the form of a screw terminal block in general view, which shows an insulating housing 1, thermoelements 4 placed over the entire area of the housing, holes for fastening (clamping) conductors 3, screws 7 and a protective screen 8. 2a - UES in the initial state. 26 - UES with partial response 14 of the thermoelement in the area of one contact connection.

Fig. 3 shows a side view of a section of a screw terminal block in the area of two devices for fastening conductors forming an electrical connection, located in the housing 1 and covered with a protective screen 8, with thermoelements 4 located on the front surface of the protective screen 8 above the devices for fastening conductors (screws 7) and covered on top with a protective layer 9. In this case, thermoelements 4 include an absorbent material 10 of black color and a heat-sensitive material 11, which in the initial state is white, and when melted penetrates into the absorbent material, revealing its color. The figure also shows: a - the minimum distance from the dielectric housing 1 to the thermoelement 4, c - the thickness of the thermoelement 4, b - the thickness of the dielectric housing 1.

Fig. 4 shows a side view of a section of a screw terminal block in the area of two devices for fastening conductors forming an electrical connection, located in the housing 1 and covered by a protective screen 8, with thermocouples 4 located in a recess 12 on the back surface of the protective screen 8 above the devices for fastening conductors (screws 7). In this case, thermocouples 4 include a dielectric material 13 of black color and a heat-sensitive material 11, which in the initial state is white, and when melted becomes transparent and reveals the color of the dielectric material 13. Also shown in the figure: a - the minimum distance from the dielectric housing 1 to the thermocouple 4, c - the thickness of the thermocouple 4, b - the thickness of the dielectric housing 1.

Implementation of a utility model

General technology of manufacturing the device

Electrical connection devices (ECD) of two or more conductors may have different appearances and structures. In particular, ECD may be a screw terminal block, a screw terminal, a neutral bus, a screw clamp, a terminal block or a feed-through terminal. Due to this, their manufacturing processes and some characteristics will differ.

UES are often used for electrical connection of wires and can be used in distribution boards with voltage up to 1000 V.

Often, in places where the UES is installed, there are restrictions on the space for installing the UES, in connection with this, it is preferable that the largest linear dimension of the device does not exceed 10 cm.

It should be noted that the existing UES do not provide space for placing individual additional temperature indicator devices, in connection with this, if necessary, the corresponding areas of the dielectric housing can be increased, preferably for placing a thermoelement with an area of at least 4 mm ² , most preferably 6-25 mm ² , to ensure the necessary visibility of the operation of thermoelements made with the ability to change color upon reaching the threshold temperature. In the case of using a single thermoelement, in which the parts made with the ability to change color upon reaching the threshold temperature are placed with the ability to thermally control several contact connections, the area of the thermoelement can be increased proportionally to the number of conductors. In this case, it is necessary that the place (site) for placing the thermoelement be accessible for visual control of its operation, after the installation of the UES.

In order to ensure electrical safety of the operation of the UES according to the declared utility model, the dielectric temperature indicator housing preferably covers at least 70% of the area of the devices for securing the conductors.

In preferred embodiments, the entire area of the conductive part's surface open to touch is covered with a dielectric thermal indicator housing.

In this case, the minimum distance from the dielectric housing to the device for fixing the conductors is no more than 3 mm. At the same time, the thermoelement is preferably located at a distance of no more than 5 mm from the device for fixing the conductors. Compliance with this requirement is preferable to ensure timely and accurate detection of heating of contact connections.

In order to increase operational reliability and reduce the risk of electric arcing during overvoltage and short circuit, it is preferable that the components of the thermoelement part are dielectrics and, most preferably, have an electrical strength of at least 3 kV/mm both before and after heating above the threshold temperature.

When manufacturing the housing, one or more recesses can be made in the area where the thermoelement will be located. The location of the thermoelement in the recess provides protection of the heat-sensitive component from mechanical damage and abrasion; prevents the heat-sensitive component from flowing down during melting (operation); increases the speed of its operation due to a decrease in the thickness of the housing in the area under the thermoelement.

In other cases, the housing itself may be a thermoelement, due to the fact that a heat-sensitive component is mixed into the housing material during its manufacture.

In general, UES include a conductive part, at least two devices for fixing conductors and an insulating housing. UES may also contain elements for mounting on a DIN rail.

The conductive part must have high thermal and electrical conductivity, in particular, it can be made of copper, aluminum or their alloys to ensure a reliable electrical connection of two or more conductors. In some cases, the conductive part can have a tinned coating to protect against the formation of an oxide film.

The means for fastening the conductors shall ensure electrical connection of the conductors through the conductive part and may preferably be screw (bolt) or spring clamps.

Screw clamps provide a secure connection of conductors using bolts and washers that are secured in a threaded hole in the conductive part and clamp the conductor, providing a contact connection. Spring clamps have a flat leaf spring for securing wires and a conductive busbar common to the conductor line.

When manufacturing the device, it is preferable that the thermoelement includes a protective layer or polymer varnish that is transparent for at least part of the visible light, which protects the dielectric thermal indicator coating and the device itself from external environmental influences, humidity, UV radiation and mechanical damage, and increases the service life of the device. The material of the protective layer is preferably selected from transparent elastic polymers, preferably from halogen-containing polymers, in particular from polyvinyl chloride, most preferably from cast polyvinyl chloride. Flexible elastic polymer films made of polyvinyl chloride, polyurethane, polyurea and other polymers can also preferably be used as materials for the protective layer.

The protective layer (if present) may have reflective or luminescent properties, may be painted in accordance with the requirements for marking the phases of cables, installation wires, harnesses and other elements of electrical equipment, or information may be applied to its surface, including threshold temperature values, the shelf life of the device and other data. In one embodiment, the inner surface of the protective layer may include multiple support elements (SE), between which at least a portion of the temperature-sensitive component of the dielectric temperature-indicating coating is located. It is worth noting that in the case of using a temperature-sensitive component based on melting, the use of a protective layer also prevents it from flowing down during the phase transition.

The thermoelement may have a layered structure. In this case, it is preferable to use a polymer dielectric layer onto which a heat-sensitive component is applied, which is at least one substance or mixture of substances having a melting point near the threshold temperature. In this case, the heat-sensitive component preferably has an electric strength of at least 3 kV/mm both before and after melting.

The dielectric layer material must be elastic and flexible to ensure the possibility of gluing to a surface of complex geometry. Therefore, halogen-containing polymeric materials are predominantly used as the dielectric layer material without limitation, in particular, chlorine-containing polymers, for example, vinyl chloride copolymers, namely: copolymer C-15 (copolymer of vinyl chloride and vinyl acetate), copolymer VHVD-40 (copolymer of vinyl chloride and vinylidene chloride), polyvinyl chloride (PVC), cast PVC, polyvinylidene fluoride PVDF, fluoroplast M-40, as well as polyesters with additives of 6.5% hexabromocyclododecane or polyesters modified with 15% trichloroisopropyl phosphate. Halogen-containing materials have low flammability. When selecting the dielectric layer material, it is necessary to take into account its melting or decomposition temperature, which must be higher than the maximum response temperature of the dielectric thermal indicator housing of the UES.

In preferred embodiments, the dielectric layer of the layered structure of the thermoelement is colored black, and the heat-sensitive component in the initial state is white and irreversibly increases transparency upon reaching the threshold temperature, resulting in a color transition with maximum contrast. In general, regardless of the type of the heat-indicating component and the presence of a dielectric layer to increase the visibility of the triggered device, it is preferable that at least a portion of the dielectric heat-indicating coating, made with the possibility of an irreversible color change upon heating above the threshold temperature, in the initial state is white, and the coloring becomes black after triggering.

The dielectric layer may have reflective or luminescent properties to increase the visibility of both the UES itself and the fact that the thermoelement has been triggered, which further increases the safety of equipment operation.

In a particular case, the dielectric layer or part of it can be painted in accordance with the requirements for marking the phases of cables, installation wires, harnesses and other elements of electrical equipment. The color of the dielectric layer can be selected in accordance with GOST 28763-90, which establishes, in particular, color marking in the field of electrical engineering. Information can also be applied to the surface of the dielectric layer, including threshold temperature values, device expiration date, batch number and other data.

In one embodiment, a dielectric layer may be used that includes multiple support elements (SEs) between which at least a portion of the temperature-sensitive component is located.

The layered structure preferably also includes a protective layer, the choice of material for which is discussed above.

In order to ensure proper response speed, it is preferable to use a thermocouple with a total thickness not exceeding 3.0 mm, preferably the thickness of the thermocouple is 0.1-3.0 mm.

To ensure reliable fastening of the thermoelement to the housing, it is possible to use glue. Permanent adhesives based on acrylic, polyurethane, rubber, silicone, PVC polymers can be used as the adhesive layer. Preferably, the adhesion of the adhesive layer to stainless steel, measured by the FINAT TM1 method after 24 hours, is at least 5 N/25 mm.

The number of threshold temperatures registered by the dielectric temperature indicator housing is not limited by an upper limit and depends on the practical task implemented when using the declared device (type of equipment, required step of the determined overheating temperature, area of the surface checked for heating, etc.).

If the thermoelement has one threshold temperature, then it is preferably located at the same distance from at least two devices for fastening the conductors. In another embodiment, the thermoelements are located in at least two sections, each of which is located near the corresponding device for fastening the conductors and the response temperature of which is the same (Fig. 1g). In particular cases, the thermoelements may have different threshold temperatures. In this case, in preferred embodiments, the thermoelements having different or identical response temperatures are located in such a way as to ensure the possibility of comparing the temperature of the greatest heating of different contact connections (Fig. 1c).

In the case of using thermoelements having different response temperatures, it is preferable that the threshold temperatures of the said sections differ by at least 5°C.

In addition to the irreversible thermoelement, the device may include at least one thermal indicator section, the color transition of which upon reaching the corresponding threshold temperature is reversible. The reversible temperature-sensitive material may be part of the dielectric coating or may be applied separately from it.

Manufacturing of a thermoelement

The claimed utility model may use a thermoelement that includes a heat-sensitive component, the operating principle of which is based on an irreversible change in appearance upon reaching the corresponding threshold temperature.

In the presence of several sections of the thermoelement having different threshold temperatures, it is preferable to use thermosensitive components of the same type, however, if necessary, thermosensitive components of different operating principles can also be used. It is preferable to use a thermosensitive component whose operation is based on a change in appearance upon melting, in particular, on a change in transparency.

In particular cases, the change in the appearance of at least one temperature-sensitive component upon reaching the corresponding threshold temperature is associated with an increase in transparency achieved by melting a substance or a group of substances included in its composition. When such a thermoelement is triggered, the color of a part of the housing or the dielectric layer (if any) located underneath them appears. In the case of using a layered structure of the dielectric coating, as well as a UES in which the thermoelements are applied to at least two sections, each of which has different threshold temperatures, when each of the coating sections is triggered, the same color transition or different color transitions may occur, depending on the coloring of the dielectric layer on the corresponding section of the thermoelement. It is preferable to color the dielectric layer over the entire area of the thermoelement, changing color upon reaching the threshold temperature, in black. In this case, in the initial state, at least part of the thermoelement is preferably white, thereby, upon triggering, a visually observable "white-to-black" transition is ensured.

The heat-sensitive component of the thermoelement may comprise: a gas-filled hot-melt material (GFHM), preferably the proportion of the gas phase of which is at least 10 vol.%; an absorbent material; support elements; at least one solid organic substance with a molecular weight of less than 2 kDa; at least one solid organic substance containing a structural fragment C _n H _(2n+1) , where n is greater than or equal to 5, and is preferably selected from the group consisting of fatty aliphatic acids containing structural fragments C _n H _(2n+1) with n greater than or equal to 12; salts of fatty aliphatic acids containing structural fragments C _n H _(2n+1) with n greater than or equal to 5; alkanes containing at least 20 carbon atoms; dialkylphosphinic acids containing structural fragments C _n H _(2n+1) with n greater than or equal to 5; amides of fatty aliphatic acids containing structural fragments C _n H _(2n+1) with n greater than or equal to 5; anhydrides of fatty aliphatic acids containing structural fragments C _n H _(2n+1) with n greater than or equal to 10; fatty aliphatic alcohols containing structural fragments C _n H _(2n+1) with n greater than or equal to 14; fatty aliphatic amines containing structural fragments C _n H _(2n+1) with n greater than or equal to 17; nitriles of fatty aliphatic acids containing structural fragments C _n H _(2n+1) with n greater than or equal to 19.

In particular embodiments, the solid organic substance/s of the heat-sensitive component are/are selected without limitation from the group consisting of: yttrium caproate, yttrium behenate, yttrium undecanoate, yttrium laurate, yttrium tridecanelaurate, yttrium tridecanepentadecanate, yttrium tridecanoate, yttrium pentadecanoate, yttrium palmitate, ytterbium caprylate, lanthanum palmitate, lanthanum nonadecynate, lanthanum caproate, erbium undecanoate, zinc nonadecanoate, zinc palmitate, zinc caproate, zinc myristicate, zinc stearate, cadmium laurate, cadmium laurinmyristate, lead caproate, lead stearate, lead laurate, lead laurinmyristate, Copper stearate, calcium stearate, lithium stearate, stearic acid, lauric acid, docosanoic acid, eicosanoic acid, crotonic acid, arachidic acid, myristic acid, palmitic acid, adipic acid, octanoic acid, capric acid, tricosanic acid, tetratriacontanoic acid, 2,3-dimethylnonanoic acid, brassidic acid, 2-methyl-2-dodecenoic acid, eleostearic acid, behenolic acid, behenic acid, oleamide, stearamide, lauramide, erucylamide, capric amide, myristic amide, caprylic amide, palmitic anilide, salicylic anilide, beta-naphthylamide caproic acid, enanthic acid phenylhydrazide, hexylamide, octacosylamide, N-methylheptacosylamide, salicylamide, hexadecanol, ecucamide, 1-docosonol, trilaurin, tricosylamine, dioctadecylamine, N,N-dimethyloctylamine, dioctylphosphinic acid, tritriacontane, tetracosane, stearyl alcohol, cetyl alcohol, stearic chloride, palmitic anhydride, stearic and acetic anhydride, lauric anhydride or mixtures thereof with a melting point that differs from the threshold temperature by no more than 5°C.

When using a gas-temperature-sensitive component in a heat-sensitive component, it is preferable that upon reaching the corresponding threshold temperature, the volume fraction of gas inside the gas-temperature-sensitive component decreases by at least two times. This ensures that the change in transparency of the gas-temperature-sensitive component is irreversible upon exceeding the corresponding threshold temperature.

The use of a heat-sensitive component, including a gas-filled thermocouple with a volumetric gas content of at least 10%, also allows for an increase in the service life of the coating and an increase in the reliability of overheating determination due to the impossibility of aggregation of solid organic matter through the gas phase. Also, the greater the proportion of gas in the gas-filled thermocouple, the higher the initial refractive index, the more contrasting the change in appearance due to a strong decrease in the refractive index when the corresponding threshold temperature is exceeded, and the more significant the separation of the gas and other phases after the gas-filled thermocouple is triggered, which eliminates the possibility of the gas-filled thermocouple returning to its original gas-filled state when the triggered thermocouple is kept at low temperatures and with temperature changes.

When using a heat-sensitive component whose action is based on melting the active substance, and especially the HTPM, the thermoelement changes its appearance only in the area that was heated above the corresponding threshold temperature, while maintaining the original appearance of other areas of the coating whose temperature did not exceed the corresponding threshold temperature. This allows comparing the temperature of contact connections, in the case when the thermoelement is applied to the housing as a single zone and carries out thermal control of several contact connections.

The process of manufacturing temperature-sensitive components, including the GTPM, is described in detail in a number of the authors' patents, in particular, in patent RU 2800396 C1, published on 21.07.2023, and can be used to create a thermoelement for the claimed utility model.

To produce at least one GTPM, the solid organic substance is ground in a ball mill to a size of 2-3 μm, a liquid phase is added, represented by water or an organic solvent with a boiling point of less than 180°C, and the resulting suspension is mixed, while periodic dispersion of the mixture with air access is preferably ensured until a constant density of the mixture is achieved. The liquid phase is preferably water or an organic solvent, the solubility of the solid organic substance of the GTPM in which does not exceed 100 g/kg.

In preferred embodiments of the utility model, the liquid phase is added in an amount of at least 50 wt.%, most preferably from 50 wt.% to 90 wt.%.

The difference in density between the liquid phase and the solid organic substance is preferably less than 0.2 g/cm ³ . For this purpose, the liquid phase can be selected without limitation from the group consisting of isopropanol, water, methanol, 1-propanol, isobutanol, ethylene glycol monomethyl ether, 1-butanol, acetonitrile, acetic acid, hexane, heptane, octane, nonane, 1,1,1-trifluoroethanol, 1,1,1,3,3,3-hexafluoroisopropanol, N,N-dimethylformamide, toluene, xylene, ethanol, butyl acetate, acetone and mixtures thereof. The resulting suspension or paste is applied to the selected part of the body or to the film (if any) and/or the protective layer (if any) and/or to the absorbent material (if any) and dried under the influence of dry air, temperature or vacuum.

This method provides for obtaining a gas-fired thermal power plant (GTPPM) that includes a solid organic substance, preferably in the form of particles with uniformly distributed voids filled with gas. Depending on the nature of the solid organic substance, the type of particles obtained may predominantly be grains, crystals, fibers, flakes or their conglomerates.

In particular cases, at least one HTPM additionally contains a polymer binder that is transparent to at least part of the visible light. In some embodiments, the binder ensures the adhesion of the HTPM to the selected part of the housing or film (if present) or absorbent material (if present). In this case, the crushed solid organic substance is suspended in a solution of a binder that is transparent to at least part of the visible light in a solvent with a boiling point below 150°C. In preferred embodiments of the utility model, to ensure the effect of glazing the solid organic substance, the binder is present in the resulting HTPM in an amount of 1-30 wt.%.

The transparent polymer binder can be selected without limitation from the group consisting of phenol-formaldehyde resin, butyl methacrylic resin, melamine-formaldehyde resin, polyvinyl butyral, polybutyl methacrylate, polyisobutyl methacrylate, polybutyl acrylate, phenoxy resin, polystyrene-acrylic emulsion, polyolefin, polystyrene, polyacrylate, polyethersulfone, polyethylene, polypropylene, polystyrene, polyvinylidene fluoride, polytetrafluoroethylene, polyethersulfone, polyisoprene, polypropylene, polybutadiene, polyisobutylene, polyvinyl acetate, polymethacrylate, ethyl cellulose, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polycaprolactone, polyethylene terephthalate resin, polybutylene terephthalate resin, polyamide resins, polyvinylidene fluoride, polyester, polyester resins, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, nitrocellulose, carboxymethyl cellulose, gelatin, agar-agar, casein, gum arabic, polyvinyl alcohol, polyethylene oxide or mixtures thereof, but not limited to them.

The temperature-sensitive component is selected in such a way that when the device is heated, preferably when at least one contact connection of the device is heated above the corresponding threshold temperature in the range of no more than 5°C, preferably no more than 2°C, the response speed is no more than 5 seconds, preferably no more than 2 seconds.

In various embodiments, the temperature-sensitive component of the dielectric temperature-indicating coating is selected in such a way that the threshold temperatures can be selected from a range of 50 to 150°C. In this case, the numerical values of the threshold temperatures of the thermoelement can be selected, in particular, from the group of 50°C, 55°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C.

For a device containing three sections of a thermoelement, each of which operates at different temperatures (T ₁ , T ₂ , T ₃ ), the threshold temperatures may be 50°C, 55°C, 60°C, or 50°C, 60°C, 70°C, or 50°C, 70°C, 80°C, or 60°C, 70°C, 80°C, or 60°C, 80°C, 100°C, or 60°C, 90°C, 110°C, or 70°C, 80°C, 90°C, or 70°C, 90°C, 110°C, or 70°C, 100°C, 120°C, or 70°C, 110°C, 130°C, or 80°C, 90°C, 100°C, or 80°C, 120°C, 140°C, or 80°C, 120°C, 150°C, or 90°C, 100°C, 110°C, or 90°C, 110°C, 130°C, or 100°C, 120°C, 140°C.

For a device containing four sections of a thermoelement, each of which operates at different temperatures (T ₁ , T ₂ , T ₃ , T ₄ ), the threshold temperatures may be 50°C, 55°C, 60°C, 70°C, or 50°C, 60°C, 70°C, 80°C, or 50°C, 70°C, 90°C, 110°C, or 60°C, 70°C, 80°C, 90°C, or 60°C, 70°C, 80°C, 100°C, or 60°C, 80°C, 90°C, 110°C, or 70°C, 80°C, 90°C, 100°C, or 70°C, 90°C, 100°C, 120°C, or 70°C, 90°C, 110°C, 130°C, or 80°C, 90°C, 100°C, 110°C, or 80°C, 100°C, 120°C, 140°C, or 80°C, 100°C, 120°C, 150°C.

In particular cases of the implementation of the utility model, one or more thermoelements may contain support elements uniformly located in the volume of the heat-sensitive component, which are added to it during its manufacture. Elements made of a material whose melting point is higher than the response temperature of the thermoelement can be used as support elements. Polymeric materials can be selected as materials for support elements, in particular, halogen-containing polymers such as polyvinyl chloride and cast polyvinyl chloride, as well as glass, ceramics, metals, non-metals and products based on them, such as meshes, fibers, microspheres, woven or non-woven materials with the above characteristics.

In particular cases of the implementation of the utility model, the heat-sensitive component may include an absorbent material (AM), which absorbs the melt of the hot-melt component during its operation. The use of AM provides additional enhancement of the technical result due to the irreversibility of the operation of the thermoelement. In addition, AM can perform the function of the supporting elements described above.

In special cases, the VM is made of porous or sorbent materials, preferably microporous materials. The VM can be selected without limitation from paper, microcellulose, wool, silk, felt, cotton, flax, molecular sieves, zeolites, silica gel, aerosil, microspheres and ceramics. The use of microporous materials with a pore diameter of no more than 2 μm is most preferable. The VM can be colored. In this case, the color of the VM appears when triggered. Alternatively, the VM can become transparent when absorbing a melt (silica gel, aerosil). In this case, when the dielectric thermal indicator coating is triggered, the color of the device element in the area of application of this coating will appear.

Application of the thermoelement

To manufacture the device, the area of the housing where no thermoelements should be located is sealed with a protective polymer film. The thermoelement is applied using a selected method, depending on the type of the heat-sensitive component used, as well as on the presence of a layered structure of the thermoelement. Then the film is removed and the sequence of actions for applying the remaining sections of the thermoelements is repeated (in the case of using more than one section of the thermoelement with different threshold temperatures). The shape and size of the sections of the thermoelements may be the same or different, depending on the requirements for the device. However, they must ensure error-free identification of the threshold temperature being exceeded, as well as the safety of personnel when working with UES connected to the network.

After applying the dielectric thermal indicator coating, in some embodiments of the utility model, it is preferably covered with a protective layer that is transparent to at least part of the visible light.

When using a thermoelement of a layered structure including a dielectric layer (in particular, an absorbent material), at the first stage, it is preferable to apply a heat-sensitive component to the dielectric layer, which is then placed on the surface of the UES housing at the second stage, in particular using an adhesive layer of constant tack. However, the reverse sequence of actions can also be used. The protective layer can be placed either before or after the thermoelement is placed on the surface of the UES housing.

Operating principle of the UES with a dielectric temperature indicator housing

The device according to the declared utility model operates as follows. The wires are installed in the holes for fastening the conductors using a device for fastening the conductors. In the initial state, the thermoelement is predominantly white.

Then, the operating voltage is connected to the contacts of the terminal block. Until the entire surface of the device or individual conductor attachment units are heated to the threshold value of the thermoelement (T), the original appearance of the device is preserved. When one individual conductor attachment unit is heated above the threshold temperature of the thermoelement (T), an irreversible change in the appearance of the thermoelement and the dielectric thermo-indicator body in the area of this contact connection occurs. Upon subsequent cooling, the surfaces of the zone with the triggered thermoelement retain their appearance, as a result of which the appearance of the entire UES does not return to its original state. This ensures the possibility of visually registering the excess of temperature above the threshold temperature, both at the moment of overheating and after a long time.

Thus, the UES according to the claimed utility model can be used to control the temperature of conductor fastening units. During a visual inspection of such UES, it is possible to reliably and with high accuracy register the fact of exceeding the temperature of all or any individual electrical connections, which ensures an increase in the safety of the operation of electrical equipment, due to the use of a dielectric housing, at least part of which is a temperature indicator.

Below are presented preferred embodiments of the claimed utility model, which are illustrative and in no way limit the scope of the requested legal protection.

Example 1

Manufacturing of UES. A spring terminal block is manufactured (similar to Fig. 1a), having 3 devices for securing conductors, an insulating housing and 3 levers of the spring mechanism.

Manufacturing of a thermoelement

Eicosanoic acid with a phase transition temperature of 70°C is used as a heat-sensitive substance for the preparation of the thermoelement; a mixture of methanol with ethylene glycol methyl ether (50/50 vol.%) is used as the liquid phase. A solid organic substance weighing 100 g is ground until the particle size reaches 2-3 μm, 200 g of the liquid phase is added and mixed, ensuring periodic dispersion of the mixture with air access, until the mixture has a constant density. The resulting suspension is used for application immediately after receipt.

To obtain a layered structure of the thermoelement, a black PVC film 0.1 mm thick, coated on the back with permanent adhesive, is used as a dielectric layer. In the area where the temperature-sensitive component will be located, information elements showing the numerical value of the threshold temperature are applied using solvent dyes. The resulting blank is placed below the UES so that the distance between the devices for fixing the conductors and the dielectric layer is 1.5 mm.

A suspension of the heat-sensitive component is applied to the front surface of the dielectric layer using the silk-screen printing method in 5 layers. After applying each layer, drying is carried out for 24 hours at room temperature. The thickness of the resulting layer of the heat-sensitive component is 1.45 mm. Then the heat-sensitive component is covered with a smooth transparent colorless protective layer made of PVC with a thickness of 0.05 mm, the dielectric layer and the protective layer are bonded due to the adhesive properties of the adhesive composition at a reduced pressure of 26.7 kPa (200 mm Hg).

The resulting thermoelement in its initial state is white in color, and its average thickness is 1.6 mm.

Triggering of the UES thermoelement.

The obtained resistivity is checked for the reliability of the conductor fastening. Then the conductive surface is locally heated in a controlled manner in the area of the contact connection of one of the conductors at a rate of 5°C/min to a temperature of 70°C with a given accuracy, the heating is stopped and the fact of the operation of the thermoelement located next to this contact connection is visually recorded by the change in color, namely by the increase in the transparency of the heat-sensitive component with the manifestation of the color of the dielectric layer (similar to Fig. 1d). The time during which the change in the appearance of the thermoelement occurs is 0.9 seconds. After cooling the device to room temperature, it is visually recorded that the return of the original appearance of the thermoelement does not occur.

Example 2

Manufacturing of UES

A screw terminal block is manufactured (similar to Fig. 2), having 4 devices for fastening conductors, an insulating housing and a protective screen. Transparent PVC granules are used to manufacture the housing, in which a heat-sensitive dye with a threshold temperature of 90°C is uniformly distributed. In the initial state, the heat-sensitive dye is white, and when the threshold temperature is reached, it changes color to black. Thus, the entire housing has heat-indicating properties, and the color of the housing corresponds to the color of the heat-sensitive dye.

Activation of the UES

The resulting UES is checked for the reliability of the conductor fastening. Then the conductive surface is locally heated in a controlled manner in the area of the contact connection of one of the conductors at a rate of 5°C/min to a temperature of 90°C with a given accuracy, the heating is stopped and the fact of the operation of the part of the housing located next to this contact connection is visually recorded by a change in color from white to black (similar to Fig. 2b). The time during which the appearance of the part of the housing changes is 2.3 seconds. After the device has cooled to room temperature, it is visually recorded that the original color of the part of the housing that has been operated does not return.

Claims (21)

1. A device for electrical connection (DEC) of two or more conductors, comprising at least two electrically connected devices for securing the conductors located inside a dielectric housing, at least part of which is designed with the possibility of an irreversible color change when heated above a threshold temperature selected from the range of 50-150°C. 2. The device according to item 1, in which the minimum distance from the dielectric housing to the device for securing the conductors is no more than 3 mm. 3. The device according to item 1, in which the part of the housing, designed with the possibility of an irreversible change in color when heated above a threshold temperature, is located at a distance of no more than 5 mm from the device for securing the conductors. 4. The device according to claim 1, in which the part of the housing, designed with the possibility of an irreversible change in color when heated above the threshold temperature, preferably has an electrical strength of at least 3 kV/mm both before and after heating above the threshold temperature. 5. The device according to item 1, in which the housing covers at least 70% of the area of the devices for securing the conductors. 6. The device according to item 1, designed with the possibility of electrically connecting wires. 7. The device according to item 1, designed with the possibility of use in distribution boards with voltage up to 1000 V. 8. The device according to claim 1, wherein the part of the housing, made with the possibility of an irreversible change in color when heated above the threshold temperature, has a layered structure including a polymer dielectric layer, preferably made of halogen-containing polymers, most preferably of polyvinyl chloride, at least one substance or mixture of substances having a melting point near the threshold temperature and an electric strength of at least 3 kV/mm both before and after melting, a protective layer, at least part of which is transparent, and the thickness of the heat-sensitive part is 0.1-3 mm. 9. The device according to claim 1, in which the change in color of at least part of the housing upon heating of the device, preferably upon heating of at least one contact connection of the device, above the threshold temperature occurs in no more than 5 seconds, and the accuracy of recording the excess of the threshold temperature is at least ±5°C, preferably at least ±2°C. 10. The device according to claim 1, wherein the housing has a dielectric strength of at least 3 kV/mm, preferably at least 5 kV/mm. 11. The device according to claim 3, in which the part of the housing, designed with the possibility of an irreversible change in color when heated above a threshold temperature, is covered with a protective layer, which is a polymer varnish or protective film, predominantly transparent to at least part of the visible light, preferably made from halogen-containing polymers, most preferably from polyvinyl chloride. 12. The device according to claim 1, wherein the color of at least a part of the body, designed with the possibility of changing color when heated above a threshold temperature, is predominantly white in the initial state, and the color after operation is predominantly black. 13. The device according to item 3, in which the heat-sensitive part of the housing, designed with the possibility of an irreversible color change when heated above a threshold temperature, is located in a recess made in the housing. 14. The device according to item 1, designed with the possibility of being secured to a DIN rail. 15. The device according to item 1, in which the devices for fastening the conductors are made in the form of a screw connection, and the UES itself is a screw terminal block, a screw terminal, a neutral busbar, or a screw clamp. 16. The device according to item 1, in which the devices for fastening the conductors are made in the form of a spring connection, and the UES itself is a spring terminal block. 17. The device according to item 3, in which the part of the housing, designed with the possibility of an irreversible change in color when heated above a threshold temperature, is located on the housing according to one of the options: at the same distance from at least two conductor securing devices; on at least two sections of the housing, each of which is located near a corresponding device for securing the conductors. 18. The device according to claim 1, which contains at least two different regions, each of which is designed with the possibility of an irreversible color change when heated above a threshold temperature. 19. The device according to claim 18, wherein the threshold temperatures of the thermoelements differ by at least 5°C.