WO2016177571A2 - Method and measuring arrangement for measuring voltage, arrangement comprising a sensor and use of a sensor for measuring voltage - Google Patents

Abstract

The invention relates to a method for measuring a voltage that is present in an electrical conductor (10). The object of the invention is that of providing a means for measuring voltage in an electrical conductor which does not require any direct contact with the electrical conductor. To achieve this, according to the invention: a measurable variable is detected by means of a sensor (40), the measurable variable being suitable for characterising the electrical field strength acting in the vicinity of the conductor (10) on a reference electrode (11) and the reference electrode (11) at least partially consisting of an electrically conductive material and being electrically insulated and spaced apart from the conductor (10); and the voltage present in the electrical conductor (10) is determined with the aid of the detected measurable variable using a measuring device (60) that is in contact with the sensor (40). The invention also relates to a measuring arrangement for measuring voltage, to an arrangement comprising a sensor and to the use of a sensor for measuring voltage.

Description

description

Method and measuring arrangement for voltage measurement, arrangement with a sensor and use of a sensor for measuring voltage

The invention relates to a method and a measuring arrangement for measuring a voltage applied to an electrical conductor. The invention also relates to an arrangement with a sensor and a use of a sensor for measuring a voltage applied to an electrical conductor.

In order to measure a voltage applied to an electrical conductor, direct electrical ohmic or capacitive measuring methods are nowadays usually used in which the voltage measurement is carried out, for example. via resistance dividers or capacitive RC dividers. In this case, electrical conductors may for example be part of electrical components, such as, for example, Cables, overhead lines, switches, transformers, of electrical installations. Electrical systems are, for example, electrical transmission and / or distribution networks, electrical switchgear or transformer systems. To perform tasks for monitoring, control and protection of such electrical systems must in many cases, a measurement of voltage applied to an electrical conductor electrical

Tension take place. For example, the measurement of the voltage for performing a directional overcurrent protection algorithm in an electrical ^¬'s distribution in addition to a current measurement is required to an indication of the direction in which a possible error of the measurement loop is seen to make.

In connection with the voltage measurement in electrical systems, it is known, for example, to use ohmic voltage dividers, which enable comparatively accurate voltage measurement, but represent a considerable cost factor, in particular if they are subsequently installed. From the German Offenlegungsschrift DE 23 25 449 AI is too ^¬ described the voltage measurement in high-voltage switchgear, a capacitive voltage converter which is formed of a current-carrying conductor of the high-voltage network and an embedded in a post insulator of the conductor electrode. Usually, such capacitive chip ^¬-DC Converters are, however, only used the displacement current of a high voltage coupling capacitor to detect the presence of a voltage of a certain minimum amount on a line of a power distribution network today, as the get ^¬ ne measurement result is partially relatively inaccurate, so it only finding the presence of the voltage, but can not be used to determine their exact height. Common to all these measuring methods is the need to make a direct electrical contact with the electrical conductor. In particular, when retrofitting existing electrical systems by retrofitting voltage transformers thus a considerable installation and cost.

The invention has for its object to provide a way of measuring voltage on an electrical conductor, in which no direct contact with the electrical conductor must be made.

According to the invention, this object is achieved by a method for measuring a voltage applied to an electrical conductor, in which a measured variable is detected with a sensor which is suitable for characterizing the electric field strength which acts on a reference electrode in the vicinity of the conductor wherein the reference electrode is at least partially made of an electrically conductive material and electrically insulated and spaced from the conductor is arranged, and the voltage applied to the electrical conductor voltage is determined based on the detected measurement with a connected to the sensor measuring device. In this way, a voltage measurement can take place without a direct electrical contact, for example by providing a voltage divider belonging to a further conductor, must be made with the conductor. It is exploited NaEM ^¬ Lich the effect that an electric field is built up in the vicinity of the conductor, acting on the field strength of the reference electrode. The intensity of this effect depends on Einwir ^¬ an existing between the electrical conductor and the reference electrode electric potential difference ^¬, that an electrical voltage that prevails between the electric conductor and the reference electrode. This makes the invention is utilized by a measure which is influenced by the force acting on the Referenzelekt- rode field strength and is thus adapted is determined with the sensor, to characterize the level of the field strength at the location of the Refe ^¬ ence electrode. By suitable evaluation can be concluded by means of the downstream measuring device based on the measured variable to the voltage.

Provided that also the electric potential is known, on which the reference electrode is located, a voltage bezo ^¬ gen to any electrical potential, preferably to a zero potential, to be specified. For this also can also be provided that the reference electrode is at Nullpo ^¬ potential.

The connection between the sensor and the measuring device can be wired as well as wireless (eg via radio technology). In the latter embodiment can be used as a measuring device, for example, a with a Nahfunktechnik (eg ZigBee, Bluetooth, RFID) Tragba ^¬ res device, such as a portable meter, a laptop, a tablet or a smartphone, which with several sensors with wireless transmission of the measured variable can interact. The invention enables both a technically simple from ^¬ refund of a new plant with voltage measurement points and a cost-effective retrofitting of such monitoring stations on existing facilities.

According to an advantageous embodiment of the method according to the invention it is provided that a force is detected by the sensor as a measurement variable, which is acting through the loading acting on the Re ference ^¬ electrode electric field of the conductor.

In this case acts by the electric field, a force on the reference electrode, which is converted by a suitable force ^¬ sensor in a measured variable. Since this measure is dependent on the magnitude of the electrical field strength, it can be used to provide an electrical voltage to it ^¬ means.

Alternatively, that sors a change of a relative position Zvi ^¬ rule is detected the conductor and the reference electrode by means of the transmitter as a measurement variable, which is caused by a movement of the reference electrode along the elekt ^¬ generic field of the conductor may also be provided. In this embodiment, a change in position of the reference electrode is detected by the sensor, which is caused by the action of a force due to the electric field on the Referenzelekt ^¬ rode force. The size of the change in position provides information about the magnitude of the electric field strength and can thus be converted by the measuring device into an indication of the voltage.

A further advantageous embodiment of the invention ^shown SEN method provides that a sensor is used with a ven of sensitive element, whose electrical conductivity changed by the action of a force. For example, a sensor can be used for this purpose, as described in the article "Ultrasensitive mechanical crack-based sensor inspired by the spider sensory system" by D. Kang et al., In the journal Nature (Volume 516, No. 7530, p. 226, 11 December 2014, ISSN 0028-0836), the content of which is explicitly incorporated by reference as part of the present disclosure. The known sensor comprises a sensitive element which comprises, for example, a platinum layer applied to a visco-elastic layer. The surface of the sensitive element has gaps. The sensitive element he ^¬ moves by the action of a force deformation, which cooperates with the provided in the surface gaps such that thereby a change in the conductivity of the sensitive element is caused. The sensor described is able to detect movements in the nanometer range.

As a result, it is also suitable for detecting the smallest changes in the position of the reference electrode, which are caused due to a changing electrical field of the conductor. In the case of an alternating voltage applied to the conductor, it is thus possible to detect a vibration or oscillation of the reference electrode whose amplitude is dependent on the magnitude of the electric field strength and thus on the voltage applied to the conductor in comparison to the reference electrode.

In this context, it is considered advantageous if the measuring device determines the voltage based on a measurement of the falling across the sensor electrical resistance. In fact, with the conductivity of the sensitive element of the sensor, the electrical resistance dropping across the sensor also changes, so that it is possible to ^deduce from the level of the resistance to the electrical ^voltage applied to the conductor. To implement the signal of the measured resistance into the voltage, for example, a suitable calibration can be carried out. According to a further advantageous embodiment of the method according to the invention can also be provided that a voltage indicative voltage measurement is supplied to a protection or control device, which, using the voltage ^¬ measured variable a function for protection, monitoring, controlling and / or regulating a executes the electrical conductor comprehensive electrical system.

In this way, the measured voltage can be used to perform a protection, monitoring, control and / or regulating function. Since the voltage measuring method according to the invention uses a comparatively inexpensive sensor which, moreover, does not have to be brought into direct electrical contact with the conductor and thus enables simple assembly, electrical systems can be equipped with a large number of voltage measuring points. Even a simple retrofitting of existing systems is possible. This increases the degree of automation of electrical systems ^¬ and thus their reliability and efficiency, as in such electrical installations, the implementation of voltage-based protection, monitoring, control and / or control functions is possible, in which a retrofitting of classical (ohmic or capacitive) voltage converters would be possible only with great effort and high costs.

Finally, according to a further advantageous embodiment of the method according to the invention can also be provided that the electrical conductor is guided in a cable and surrounded by a shield conductor and is used as a reference electrode of the shield conductor.

In this case, a simple voltage measurement can be performed on a shielded cable ladder. The shielding conductor provided primarily for shielding electro-magnetic fields is used here as a reference electrode, since it is exposed to the electric field present around the conductor. In the process, the shielding conductor will become affected by the action of the contract or expand what can be detected by the sensor. In this way, it is very advantageous to perform a voltage measurement in shielded cable networks, since it is not necessary to open the shielding conductor to create a voltage measuring point. On the other hand, the sensor can be applied either directly on the shielding conductor or on a jacket of the cable surrounding the shielding conductor, provided that this does not cause excessive damping of the force on the shielding conductor or movement of the shielding conductor due to the electric field around the conductor.

The above-mentioned object is also achieved by a measuring arrangement for measuring an electrical voltage, the arrangement comprising a sensor and a sensor connected to the measuring device and is adapted to the electrical conductor to which the voltage to be measured, in to be brought into operative connection.

According to the invention, the sensor is designed to detect a measured variable which is suitable for characterizing the electric field strength acting on a reference electrode in the vicinity of the conductor, wherein the reference electrode consists at least partially of an electrically conductive material and electrically isolated and spaced from the conductor is arranged, and the measuring ^{device ¬ is designed} for determining the electrical voltage based on the detected measured variable.

Consequently, the measuring arrangement according to the invention comprises at least the sensor and the measuring device. Sensor and measuring device can communicate with each other in a wired or wireless manner.

In one embodiment of the measuring arrangement, the sensor can be connected, for example, to the reference electrode. In this way, the effect of the electric field on the reference electrode can be continuously detected by the sensor and in the form of the measured variable to the measuring device further gege ben ^¬. The measuring device can be arranged in spatial proximity or remote from the sensor. In another embodiment of the measuring arrangement, the measuring device can form a structural unit with the sensor. In this case, the structural unit, for example, be firmly mounted in the vicinity of the electrical conductor, for example as part of an electrical system comprising the conductor.

In a further embodiment of the measurement arrangement a structural unit may comprise the sensor, the measuring device and the Re ference ^¬ electrode. This structural unit may be formed, for example, as a separate, possibly also portable, measuring device, which is brought to the voltage measurement in the vicinity of the conductor, that the reference electrode is exposed to the effect of the electric field around the conductor. According to an advantageous embodiment of the measuring arrangement according to the invention, it can be provided that the sensor comprises a sensitive element whose electrical conductivity can be changed by the action of a force. By way of example, this sensor can be a sensor of the type already described with regard to the method according to the invention.

In this context, it can also be provided that the measuring device is designed to measure the drop across the sensor electrical resistance.

With regard to the voltage measurement of shielded cables, said Referenzelekt- may be provided according to an advantageous embodiment of the measuring arrangement also erfindungsgemä- SEN that the sensor is attached to a cable, which comprises the conductor and a screen surrounding the Lei ^¬ ter conductor, Rode is at least partially formed by the shield conductor and the sensor with the shield conductor or with a

Shielding conductor surrounding jacket of the cable is connected. In this case, the shield conductor is advantageously used as a reference electrode. The sensor can, for example, be di ^¬ rectly applied to the shield conductor or a surrounding the shield conductor sheath of the cable. Cable ge ^¬ shielded electrical conductors are used for example in electrical systems and supply networks, in particular the medium and low voltage level.

According to another embodiment of the measuring arrangement according to the invention can also be provided that the sensor is connected to a surrounding the conductor cuff, which includes the reference electrode.

In this embodiment, a voltage measurement on unshielded conductors, such as unshielded cables, overhead lines or contacts in switches, can be made. In this case, a sleeve is arranged around the conductor, which comprises the reference electrode. It can be provided either as a closed ring around the conductor and thus to the entire circumference of the sleeve enforcement zen or form only a partial segment of the cuff, the Referenzelekt ^¬ rode. The sensor is in connection with the reference electrode and can thus detect the effect of the electric field of the conductor on the electrode as a measured variable. A further embodiment of the measurement arrangement according to the invention provides that the sensor and the reference electrode are arranged in a portable measuring device that is capable of temporarily being in such proximity to the head Hérange ^¬ resulting in that the reference electrode through the surrounding the conductor electrical Field is affected. In this way, a universal portable Messge ^¬ is quasi advises formed on electrical conductors which is suitable for mobile use for discontinuous measurement for voltage measurement.

With regard to the measuring arrangement according to the invention, all statements made above and below with regard to the method according to the invention apply and vice versa in a corresponding manner; in particular, the measuring arrangement according to the invention for carrying out the method according to the invention is set up in any desired embodiment or a combination of any desired embodiments. Also with regard to the advantages of the measuring arrangement according to the invention, reference is made to the advantages described for the method according to the invention.

The abovementioned object is also achieved by an arrangement having an electrical conductor and a reference electrode, which consists at least partially of an electrically conductive material and is disposed in an electrically insulated manner and spaced from the conductor.

Such an arrangement is known for example in a special embodiment as a shielded cable. According to the invention, the arrangement comprises a sensor which is designed to detect a measured variable which is suitable for characterizing the electric field strength acting on a reference electrode in the surroundings of the conductor, and the sensor is designed for Determining a voltage applied to the electrical conductor voltage to be brought into operative connection with a measuring device.

The arrangement according to the invention thus comprises both the conductor and the reference electrode as well as the sensor. As a result, quasi arrangements in the form of electrical components can be created, which are as it were a built-in voltage include measuring point. The load detected by the sensor measurement ^¬ size must be passed in this case only to a measuring device which performs the determination of the voltage from the measured variable. In this context, the sensor can, for example, have a device for the wireless transmission of information (for example a near-field radio communication interface) via which the measured variable is transmitted to a measuring device. The measuring device can be formed in this case, for example, by a portable device, such as a laptop, a tablet computer or a smartphone. Alternatively, however, the sensor may also be connected to a stationary measuring device, for example a control center device. It is also possible that there is a cable-bound communication connection between the sensor and the measuring device.

With regard to the arrangement may also be provided that the arrangement is a cable containing the conductor, and the reference electrode is a screen conductor surrounding the conductor.

In this embodiment, virtually a shielded cable can already be equipped by the manufacturer with sensors that detect the effects of the electric field of the conductor on the shielding conductor and pass on corresponding measured variables to measuring devices. In this case, the separate installation of measuring points is largely unnecessary.

With regard to the arrangement according to the invention apply to the method according to the invention above and below made statements and vice versa in a corresponding manner, in particular the arrangement according to the invention for performing ^¬ tion of the method according to the invention in any embodiment or a combination of arbitrary embodiments set up. Also with regard to the advantages of the arrangement according to the invention, reference is made to the advantages described for the method according to the invention. Finally, the invention also relates to the use of a sensor with a sensitive element, whose electrical conductivity is changed by the action of a force ver¬ ^¬ derm, for measuring an electrical voltage applied to a surrounded by a shield conductor electrical conductor of a cable.

By way of example, such a sensor may be a sensor of the type described with regard to the method according to the invention.

The invention will be explained in more detail with reference to Ausführungsbeispie ^¬ len. The specific embodiment of the ^exemplary embodiments is in no way limiting for the general configuration of the method according to the invention, the measuring arrangement according to the invention and the arrangement according to the invention with a sensor and the inventive use of a sensor for measuring voltage; Rather, individual design features of the exemplary embodiment can be freely combined with one another and with the features described above in any desired manner.

For this purpose, 1 shows a schematic view of an electrical ^¬'s conductor and a first embodiment of a reference electrode in cross section; Figure 2 is a schematic view of an electrical ^¬ rule conductor and a second embodiment of a reference electrode in cross section;

Figure 3 is a Schamtische representation of the prinzi ^¬ piellen structure of a cable with an electrical conductor; Figure 4 is a schematic representation of a Ka ^¬ lever with on a jacket of the cable be ^¬ strengthened sensor;

Figure 5 is a schematic representation of a Ka ^¬ lever with attached to a shield conductor of the cable sensor; Figure 6 is a schematic representation of a Ka ^¬ lever and a measuring arrangement for voltage measurement;

Figure 7 is a schematic representation of a Ka bels fixed with a vice on a cable ^¬ reproduced cuff sensor according to a first embodiment;

Figure 8 is a schematic representation of a Ka bels fixed with a vice on a cable ^¬ reproduced cuff sensor according to a second embodiment; and

Figure 9 is a schematic illustration of a lifting ^¬ cash measuring arrangement for voltage measurement,

Figure 1 shows a schematically indicated electrical conductor 10 in cross section. At this is related to Erdpoten ^¬ tial voltage U _L on. An electric field around the conductor 10 is indicated in Figure 1 by arrows. In the area of the electric field there is a reference electrode 11, which at least partially consists of an electrically conductive material, eg copper or aluminum, is electrically insulated from the conductor 10 and is arranged at a distance from the conductor 10. At the reference electrode is a reference ^¬ voltage U _R on. Preferably, the reference voltage U _R correspond to the ground potential. Due to the electrical field located around the conductor 10, a force acts on the reference electrode 11, which - depending on potential difference and sign of the voltage applied to the reference electrode 11 potential - is directed to the conductor 10 to or away from this, as in Figure 1 indicated by appropriate arrows. At a higher potential difference, the electric field strength of the electric field increases by the head 10. This increases rificing electric potential of the reference electrode 11 entspre ^¬ accordingly also the force exerted by the electric field to the reference electrode ^¬. 11

If it is at the voltage applied to the conductor 10 voltage to an AC voltage, so that by the electric field to the reference electrode 11 applied (with constant elekt ^¬ step potential) force oscillates at least approximately with the frequency of the AC voltage, which, for example, by vibrating the reference electrode 11 expresses. If it is at the voltage applied to the conductor 10 voltage to a DC voltage, a static force acts on the reference ^¬ electrode 11 changes in accordance only with a change of the DC voltage of the conductor 10th When the electric field or the electric field is detected cha ^¬ rakterisierende measure, for example, a force acting on the reference electric ^¬ de force or a change in position of a reference electrode elastically held, can be due to the interaction between abutting on the conductor 10 of electrical voltage and the Determine the strength of the electric field from this measurement an indication of the voltage acting between the conductor 10 and the reference electrode 11 electrical voltage. If the reference electrode 11 is at ground potential, the measured voltage corresponds to the electrical voltage acting between the conductor 10 and ground. The electrical conductor 10 can be any form of electrical conductor, eg a conductor of a cable, an overhead line or a contact of a switch. FIG. 2 shows a further schematic representation of an electrical conductor 10 in cross section. In contrast to Figure 1, the reference electrode 21 according to figure 2 in cross-section than is ^¬ coaxially around the conductor 10 arranged ring formed. By way of example, the reference electrode 21 may be a shielding conductor surrounding the conductor, which usually extends over the entire length of the conductor 10 or at least a large part thereof. Alternatively, the reference electrode 21 may however also extend only over a portion of the conductor 10 and for example be formed in the manner of the conductor partially surrounding sleeve made ^¬.

Also on the reference electrode 21 acts as a result of the electric ^¬ 's field around the conductor 10, a force that causes the ring cross-section of the reference electrode is slightly stretched outward ^¬ Shen or contracted inwards. This effect is indicated by arrows shown by way of example in FIG. For example, the reference electrode 21 undergo VIB ration at a temperature on the conductor 10 at ^¬ AC voltage. These too from the height of the electric

Field strength-dependent effects can be recorded in the form of a measured variable and used to determine the voltage.

FIGS. 3 to 5, using the example of a shielded cable, show how a voltage measurement for an electrical conductor can take place. For this purpose, in Figure 3, first schematically the general structure of a cable 30 Darge ^¬ represents. The cable 30, shown in sections in FIG. 3, encompasses the electrical conductor 10. This can consist, for example, of copper or aluminum. In addition, the conductor of a cable is usually not in one piece, but in the form of a plurality of interconnected wires. The conductor 10 is coaxial al surrounded by an electrically insulating dielectric 31, which may consist of one or more layers and, for example, consists of polyethylene. The dielectric 31 is coaxially surrounded by a shield conductor 32 having an annular cross-section. The shield conductor 32 is constructed, for example, of copper in the form of a band or a braid. In principle, the shielding conductor serves to reduce electromagnetic couplings between the conductor and other electrical or electronic components. The shielding conductor 32 is finally surrounded coaxially by a jacket 33 insulating the cable to the outside.

The construction of a cable shown in FIG. 3 is only to be understood as an example, depending on the type and intended use of the cable, further layers (for example separating layers, conductive layers) may be added to the illustrated layers. Cables such as that shown in FIG. 3 are used, for example, in electrical medium and low-voltage networks. As explained in connection with FIG. 2, the shield conductor 32 of the cable can be used as a reference electrode for voltage measurement, since it is influenced by the height of the electric field present around the conductor 10.

Figure 4 shows an embodiment of a cable 30 with egg ^¬ NEM applied to the shield conductor 32 of the cable (only schematically indicated in Figure 4) sensor 40. The sensor 40 is adapted to a caused by the electric field strength to the shield conductor 32 effect as the measured variable to erfas ^¬ sen. In this case, as explained with reference to FIG. 2, this may be, for example, a force acting on the screen conductor 32 or a change in position of the screen conductor 32 (eg a vibration). The sensor 40 used for detecting the measured variable may for example comprise a sensitive element whose elekt ^¬ generic conductivity by a force exerted on the sensor 40 Power is changed. Such a sensor that can detect a few nanometers by a force resulting movements in the area, is described for example in the already initially he ^¬ mentioned essay "Ultra Sensitive mechanical crack-based sensor inspired by the spider sensory system" This sensor has a viscoelastic layer. on which a platinum layer is applied. the layer of platinum has Spal ^¬ th or cracks, so that upon application of a force, the platinum layer is exposed by narrowing or widening of the columns of a surface deformation on the conductivity of the platinum layer and therefore of the sensor acts from ^¬ a resistance measurement on the voltage between the shield conductor 32 can be generated (as a reference electrode on Erdpoten- TiAl) and conductor 10 characterizing measured value by means of a not shown in Figure 4 measuring device, from the -., for example, via a suitable calibra ^¬ tion - on the voltage applied to the conductor 10 Sp oltage can be CLOSED ^¬ sen. FIG. 5 shows a further embodiment of a shielded cable 30 with sensor 40 for voltage measurement. In contrast to FIG. 4, in the case of the cable 30 according to FIG. 5, the sensor 40 is fastened to the jacket 33 of the cable 30, for example adhesively bonded. In this embodiment, it should be noted that with regard to a force exerted on the shielding conductor 32 or a movement (eg vibration) of the shielding conductor 32 through the jacket, a certain damping takes place. This effect has to be taken into account as part of the calibration of the measuring device.

Since the sensor 40 in the embodiments according to Figures 4 and 5 applied only from the outside on the shield conductor 32 and the jacket 33, eg glued, must be, for the provision of a voltage measuring point no great effort is required. An opening of the shield conductor 32 to make direct electrical contact with the conductor 10 is not required. Also a retrofit of existing cables can be done in this way relatively simple and ^{kostengüns ¬} tig.

Figure 6 shows schematically a cable 30 in cross section. As described above, the cable 30 includes the conductor 10, the ^¬ lektrikum 31, the shield conductor 32 and the jacket 33. In Figure 6 is also mounted on the casing 33 of the sensor 40 for detecting the electric field strength characterizing around the conductor 10 measured variable , By the conductor 10 surrounding electric field, a force is exercised on the shield conductor 32 from ^¬ which generates a movement of the shield conductor, such as a Vibra ^¬ tion with an AC voltage. The force, or caused by the force change in position of the reference electrode in the form of the shield conductor 32, the stronger, the greater the field strength of the conductor 10 surrounding the electric field. In addition, the field strength depends on the voltage applied to the conductor 10 as described above.

The dependent on the field strength measured value (force, movement and expansion or relative position of the reference electrode to the conductor) is detected by means of sensor 40 and vice ^¬ sets in an auxiliary variable. In a sensor of the type described above, the conductivity of the sensitive element of the Sen ^¬ sensor is used as an auxiliary variable, which can be detected by a resistance measurement with a measuring device 60. The measuring device may consist of the determined resistance value, for example by geeigne ^¬ th calibration, an indication of the between the conductor 10 and the reference electrode: determine the present voltage (here, the shield conductor 32). If the reference electrode is at earth potential, the determined voltage corresponds to the electrical voltage between the conductor 10 and ground.

Optionally, for example, can be provided that a voltage is bender measured voltage value U _mess to an evaluation device 61 of an electrical protection device is passed 62, using the voltage measured value U _mess and possibly wide ^¬ rer measured values (eg current) protection algorithm for over- guards the cable or connected to the cable parts of an electrical system for errors, such as short circuits or ground faults. For example, a directional over- can be executed time-overcurrent protection by using a current and a voltage measurement, in addition to the mere presence of a fault (based on the overcurrent) seen the Rich ^¬ processing of the fault from the measuring point from (on the basis of the phase angle between current and voltage ) indicates. The

Protective device 62 can output a corresponding error signal F in the event of an error.

It is possible to already produce cables 30 and sensor 40 as a unit by the manufacturer and thus to provide a cable with integrated voltage measuring points. By connecting suitable measuring devices measurements can be made at the prefabricated voltage measuring points.

Alternatively, it is also possible to provide or retrofit a measuring arrangement consisting of sensor 40 and measuring device 60 at arbitrary locations of a cable. This can be done with a shielded cable, for example by attaching (eg sticking) of the sensor on the jacket or the shield conductor of the cable; a direct contacting of the electrical conductor, however, is not necessary, so that the shield conductor advantageously does not have to be opened. A Übertra ^¬ supply the captured by the sensor measured quantity to the measuring device can be done via a wired or a wireless communication link. Figures 7 and 8 show an alternative way to Be ^¬ attachment of a sensor to an electrical conductor. In Figure 7, for this purpose a cable 70 is shown with a step elekt ^¬ conductor 10 in cross section. The cable 70 is an unshielded cable in which the electrical conductor 10 is surrounded directly by an electrically insulating jacket and no shielding conductor is provided. According to the embodiment shown in FIG. 7, a sleeve 71 is laid around the cable as the reference electrode. The collar 71 may, for example with clamping tabs 72 verse ^¬ hen, which can be connected via a clamping screw 73 with each other to aufzupressen the cuff 71 on the sheath of the cable 70th The sleeve 71 consists in this case at least partially of an electrically conductive material, so that it - as in the shielded cable of the shielding conductor - is influenced by the electric field around the conductor 10. By means of the sensor 40 applied to the sleeve 71, a measured variable (force, positional change relative to the conductor, eg in the form of the amplitude of a vibration) can thus be detected, which characterizes the electric field strength around the conductor at the location of the reference electrode. As described above, the measured quantity can be determined via a (not shown in FIG. 7).

Measuring device are converted into an indication of the voltage applied to the conductor 10.

The embodiment with the sleeve 71 advantageously makes it possible to provide or retrofit local measuring points for measuring voltage on cables and other electrical installations in which no element (for example a shielding conductor) can be used as a reference electrode. FIG. 8 shows an alternative embodiment of a cuff for measuring stress. FIG. 8 shows the cable 70 with the electrical conductor 10. The cable 70 is surrounded by a sleeve 81 as in FIG. 7, but the sleeve 81 is made of an electrically non-conductive material (eg plastic) in the embodiment shown in FIG , However, the collar 81 has a recess 82 (e.g., a bore or longitudinal groove) into which to engage

Sensor element 83 is used as a reference electrode. The sensor element 83 consists of an electrically conductive material. This sensor element 83 is in the

Recess 82 of the sleeve 81 arranged radially displaceable, so that it by the action of the electric field of the Ladder can be moved. Partially extending over the recess 82 with the Meßaufnehmerelement 83, the sensor 40 is mounted on the sleeve 81 to detect a change in position ^¬ the Meßaufnehmerelements 83 or acting on this force.

Finally, FIG. 9 shows a measuring arrangement with a reference electrode 11, a sensor 40 and a measuring device 60, which are housed together in a portable measuring device 90. The portable meter 90 includes a sensor portion 92 and a grip portion 93 and can be moved 10 so that the reference electric ^¬ de 11 is exposed to the electric field of the conductor 10 in the vicinity of an electrical conductor. By the sensor 40, a force acting on the reference electrode 11 due to the electric field or a change in the position of the reference electrode 11 can be detected. About the measuring device 60, this force or change in position can be detected, for example by means of a resistance measurement and converted into a voltage measured variable U _m ess. The voltage measured variable L ess can then, for example, a display device 94 (display or the like) supplied to and the user of the instrument 90 is ^¬ shows.

In the exemplary embodiments described above, the voltage measurement on an electrical conductor of a cable has mostly been turned off. However, the invention is not limited by voltage measurements on cables, but can be measured on electrical conductors of any embodiment voltage applied. In addition, although a sensor having a special surface whose conductivity is more variable by force has been described as a means for detecting the quantity characterizing the field strength, any sensor that is suitable for this purpose can in principle be used with the required sensitivity to detect the effects of electric field strength on a reference electrode.

Claims

claims 1. A method for measuring a voltage applied to an electrical conductor (10), in which the following steps are carried out: - Detecting a measured variable by means of a sensor (40), wherein the measured variable is adapted to characterize the electric field strength, which acts in the environment of the conductor (10) on a Referenzelekt ^¬ rode (11), and wherein the reference electrode (11) at least partially made of an electrically conductive material ^¬ and electrically isolated and spaced from the conductor (10); and  Determining the voltage applied to the electrical conductor (10) on the basis of the detected measured variable with a measuring device (60) in communication with the sensor (40). 2. The method according to claim 1, d a d u r c h e c e n c i n e s that - By means of the sensor (40) as a measured variable, a force is detected, which is effected by acting on the reference electrode (11) ^¬ de electric field of the conductor (10). 3. The method according to claim 1, d a d u r c h e c e n c i n e s that - by means of the sensor (40) is detected as a measure of a change in egg ^¬ ner relative position between the conductor (10) and the reference electrode (11) (by moving the Re ^¬ ferenz electrode (11) along the electric field of the Lei ^¬ ters 10) is caused. 4. The method according to any one of the preceding claims, d a d u r c h e c e n c i n e s that  - A sensor (40) is used with a sensitive element whose electrical conductivity changes by the action of a force. 5. The method according to claim 4, characterized in that - The measuring device (60) determines the voltage based on a measurement of the across the sensor (40) falling electrical resistance. 6. The method according to any one of the preceding claims, d a d u r c h e c e n c i n e s that  a voltage indicative voltage measure Protective or Leitgerät (62) is supplied, which, using the Spannungsmessgröße a function of protection, for Monitoring, for controlling and / or for regulating an electrical system comprising the electrical conductor (10) performs. 7. The method according to any one of the preceding claims, d a d u r c h e c e n c i n e s that  - The electrical conductor (10) is guided in a cable (30) and surrounded by a shield conductor (32); and  - As the reference electrode (11) of the shield conductor (32) is used. 8. measuring arrangement for measuring an electrical voltage, wherein the arrangement comprises a sensor (40) and a sensor (40) in communication with the measuring device (60) and is adapted to the electrical conductor (10) to which the measuring voltage is applied to be brought into an operative connection ^¬ ; d a d u r c h e c e n c i n e s that - The sensor (40) is designed to detect a measured variable which is adapted to characterize the electric field strength, which acts in the vicinity of the conductor (10) on a reference electrode (11), wherein the reference electrode (11) at least partially consists of an electrically conductive Ma ^¬ material and electrically isolated and spaced from the conductor (10) is arranged; and - The measuring device (60) is designed for determining the electrical voltage based on the detected measured variable. 9. Measuring arrangement according to claim 8, d a d u r c h e c e n c i n e s that  - The sensor (40) comprises a sensitive element whose electrical conductivity is changed by the action of a force. 10. Measuring arrangement according to claim 9, d a d u r c h e c e n c i n e s that  - The measuring device (60) is designed for measuring the across the sensor (40) falling electrical resistance. 11. Measuring arrangement according to one of claims 8 to 10, d a d u r c h e c e n c i n e s that  - The sensor (40) is attached to a cable (30), the conductor (10) and a conductor (10) surrounding the screen conductor (32), wherein the reference electrode (11) is at least partially formed by the shield conductor (32) and the sensor (40) with the shield conductor (32) or with a jacket (33) of the cable (30) surrounding the shield conductor (32) ) connected is. 12. Measuring arrangement according to one of claims 8 to 10, d a d u r c h e c e n c i n e s that  - The sensor (40) with a conductor (10) surrounding cuff (71, 81), which comprises the reference electrode (11) is connected. 13. Measuring arrangement according to one of claims 8 to 10, d a d u r c h e c e n c i n e s that - The sensor (40) and the reference electrode (11) are arranged in a portable measuring device (90) which is adapted to temporarily be in such a proximity to the conductor (10) forth here ^{¬ be} led, that the reference electrode (11) is influenced by the electric field surrounding the conductor (10). 14. An arrangement comprising an electrical conductor (10) and a reference electrode (11) at least partially made of an electrically conductive material and electrically isolated and spaced from the conductor (10) is arranged; d a d u r c h e c e n c i n e s that  - The arrangement comprises a sensor (40) which is adapted to detect a measured variable which is adapted to characterize the electric field strength, which acts in the vicinity of the conductor (10) on a reference electrode (11), and  - The sensor (40) is adapted to be brought to determine a voltage applied to the electrical conductor (10) voltage with a measuring device (60) in operative connection. 15. Arrangement according to claim 14, d a d u r c h e c e n c i n e s that - The arrangement is a cable (30), the ent ^¬ holds the conductor (10); and - The reference electrode (11) is a conductor (10) surrounding the shield conductor (32). 16. The use of a sensor (40) having a sensitive Ele ^¬ element whose electrical conductivity can be varied by application of a force, for measuring an electric voltage, which is surrounded at one of a shield conductor (32) electrical conductors (10) of a cable (32 ) is present.