WO2021237977A1 - Apparatus and method for monitoring resistance between null line and ground line - Google Patents

Abstract

An apparatus and method for monitoring the resistance between a null line and a ground line. The apparatus comprises: an energy storage element (10), a charging circuit (11), a discharging circuit (12), a sampling circuit (13), a shaping filtering circuit (14) and a control circuit (15). The method comprises: charging an energy storage element (10) by means of a charging circuit (11); using a shaping filtering circuit (14) and a control circuit (15) to monitor, in real time, a zero-crossing moment of a power supply system; when the control circuit (15) monitors that a voltage between a null line and a ground line is zero, using a discharging circuit (12) to make the energy storage element (10) discharge, and measuring voltages at two ends of the energy storage element (10) during the discharging process, and measuring, by means of a sampling circuit (13), a current value in a discharging loop (12) when the energy storage element (10) discharges; and finally, feeding back the measured voltages and current value to the control circuit (15), and the control circuit (15) calculating an equivalent resistance value between the null line and the ground line according to the obtained voltages and current value. In this way, online measurement and monitoring of the grounding resistance of a power distribution system are realized.

Description

Zero-ground resistance monitoring device and method Technical field

The present invention relates to the technical field of electrical safety, in particular to a zero-ground resistance monitoring device and method.

Background technique

Grounding protection is an important technical measure to ensure electrical safety. Generally, when the grounding protection system is normal, accidental electric shock will not occur even if the electrical appliance leaks, because the leaked dangerous voltage will be introduced into the ground by the grounding wire and cause a large enough fault. The current makes the air switch or the leakage switch automatically cut off the power, but an important technical index to achieve this goal is the grounding resistance value.

In practical applications, the grounding resistance of protective grounding may increase its grounding resistance due to changes in the geological environment of the grounding electrode, oxidation of the electrical connection point of the grounding wire, and mechanical failure of the grounding wire, thereby losing its effective protective effect. Causes electric shock and electrical fire accidents. In addition, most of the ground resistance measurement devices in the prior art need to set auxiliary electrodes on the ground or measure closed loops, and cannot realize online measurement and monitoring of the ground resistance of the power distribution system.

Summary of the invention

In view of this, the embodiments of the present invention provide a zero-ground resistance monitoring device and method to solve the problem that in the prior art, the online measurement and monitoring of the ground resistance of the power distribution system cannot be achieved.

According to the first aspect, the present invention provides a zero-ground resistance monitoring device, including:

Energy storage element

The charging circuit is respectively connected with the energy storage element and the neutral and live wires of the power supply system to form a loop for charging the energy storage element by the power supply system;

The discharge circuit is respectively connected with the energy storage element and the neutral and ground wires of the power supply system to form a loop for the energy storage element to discharge the neutral and ground wires of the power supply system;

Sampling circuit, connected with the energy storage element and the discharge circuit; used to measure the current value in the discharge loop when the energy storage element is discharged;

The shaping filter circuit is connected to the control circuit and the neutral, live and ground wires of the power supply system; it is used to filter the interference and clutter of the power supply system so that the control circuit can determine the zero-crossing time of the power supply system;

The control circuit is respectively connected with the shaping filter circuit, sampling circuit, charging circuit, discharging circuit and energy storage element; used to control the charging circuit and the discharging circuit to switch between charging and discharging and to collect the voltage of the energy storage element and the sampling circuit to discharge the energy storage element Calculate the discharge current based on the voltage drop at the time, and calculate the equivalent resistance value between the neutral wire and the ground wire based on the voltage and discharge current of the energy storage element.

The zero-ground resistance monitoring device provided by the embodiment of the present invention charges the energy storage element through a charging circuit, and uses a shaping filter circuit and a control circuit to monitor the zero-crossing moment of the power supply system in real time. When the control circuit monitors that the voltage between the neutral line and the ground line is zero, the discharge circuit is used to discharge the energy storage element, and the voltage at both ends of the energy storage element during the discharge process is detected at the same time; and the sampling circuit discharges when the energy storage element is discharged. The current value in the loop; finally, the detected voltage and current value are fed back to the control circuit, and the control circuit calculates the equivalent resistance value between the neutral wire and the ground wire according to the obtained voltage and current value to achieve Online measurement and monitoring of the grounding resistance of the power distribution system.

With reference to the first aspect, in a first implementation manner of the first aspect, the charging circuit includes:

The voltage divider rectifier circuit is respectively connected with the neutral line and the ground line and the first switching device;

The first end of the first switching device is connected to the output end of the voltage dividing rectifier circuit, the second end of the first switching device is connected to the first end of the energy storage element, and the third and fourth ends of the first switching device are connected to the control circuit connect;

Among them, the voltage divider rectifier circuit also includes:

The first resistor, the first end of the first resistor is connected to the live wire, the second end of the first resistor is connected to the first end of the rectifying device, the second end of the rectifying device is connected to the first end of the second resistor and the first switching device The first end of the resistor is connected, and the second end of the second resistor is connected to the neutral line.

The zero-ground resistance monitoring device provided by the embodiment of the present invention uses a voltage divider rectifier circuit to convert alternating current in the power supply system into direct current, so as to ensure that the zero-ground resistance monitoring device can work normally. The direct current is output to the energy storage element through the first switching device to complete the action of charging the energy storage element, thereby providing initial conditions for subsequent online monitoring, ensuring that subsequent parts of the circuit/component can work normally and implementing online power supply systems Zero-ground resistance monitoring.

With reference to the first aspect, in a second implementation manner of the first aspect, the discharge circuit includes:

For the first controllable element, the first end of the first controllable element is connected to the sampling circuit, the second end of the first controllable element is connected to the neutral line, and the third end of the first controllable element is connected to the control circuit.

In the zero-ground resistance monitoring device provided by the embodiment of the present invention, the first controllable element is configured to use the conduction characteristic of the controllable element to control the on-off of the circuit. When the energy storage element meets the discharge condition, the first controllable element is turned on to make the energy storage element discharge. So as to ensure real-time monitoring of the power supply system, and further realize real-time online zero-ground resistance monitoring.

With reference to the first aspect, in a third implementation manner of the first aspect, the sampling circuit includes:

The first end of the third resistor is connected to the second end of the energy storage element, and the second end of the third resistor is connected to the discharge circuit.

The zero-ground resistance monitoring device provided by the embodiment of the present invention is provided with a third resistor, and the current value of the energy storage element flowing through the third resistor at the time of discharging is collected by the third resistor, and the obtained current value is sent to the controller. The method set in the controller calculates the collected data to obtain the collected result. In this way, real-time measurement of the zero-ground resistance is further realized, and the electricity user can judge the leakage of the zero-ground resistance according to the collection results, so as to ensure the life safety of the human body in time.

With reference to the first aspect, in the fourth implementation of the first aspect, the first end of the shaping filter circuit is connected to the control circuit, the second end of the shaping filter circuit is connected to the live wire or the neutral wire, and the third end of the shaping filter circuit is connected to the control circuit. Ground connection.

The zero-ground resistance monitoring device provided by the embodiment of the present invention uses a shaping filter circuit to filter out interference signals between power supply systems, which is beneficial to accurately determine the zero-crossing time of the power supply system.

With reference to the first aspect, in a fifth implementation manner of the first aspect, the control circuit includes:

A controller, the controller is respectively connected with the energy storage element, the sampling circuit, the detection circuit, the first driving circuit and the second driving circuit;

The first end of the first drive circuit is connected to the controller, and the second end and the third end of the first drive circuit are respectively connected to the third end and the fourth end of the first switching device;

The first end of the second drive circuit is connected to the controller, and the second end of the second drive circuit is connected to the third end of the first controllable element.

In the zero-ground resistance monitoring device provided by the embodiment of the present invention, a controller is set to control the first drive circuit and the second drive circuit to control the charging and discharging of the energy storage element, so as to realize intelligent monitoring of the state of the power supply system.

With reference to the first aspect, in a sixth implementation manner of the first aspect, the control circuit further includes:

A third drive circuit, the first end of the third drive circuit is connected to the controller, and the second end and the third end of the third drive circuit are respectively connected to the third end and the fourth end of the second switching device;

The zero-ground resistance monitoring device provided by the embodiment of the present invention is formed by setting a third drive circuit so that its control circuit can meet individual charging and discharging, thereby achieving independent control of the zero-ground resistance monitoring device so that the zero-ground resistance monitoring device can be controlled separately. Increased flexibility.

The first end of the second switching device is connected to the ground, and the second end of the second switching device is connected to the first end of the energy storage element;

Wherein, the third driving circuit and the first driving circuit are the same driving circuit; the second switching device and the first switching device are the same switching device.

In the zero-ground resistance monitoring device provided by the embodiment of the present invention, the second switching device and the first switching device are set as the same switching device, and the third drive circuit and the first drive circuit are set as the same drive circuit, so as to simplify the hardware circuit structure , Save the cost of the circuit, while ensuring the stability of the circuit function.

With reference to the first aspect, in a seventh implementation manner of the first aspect, it includes: a controller connected to the first driving circuit, and the first driving circuit is connected to the first switching device; used to switch the charging circuit and the discharging circuit to realize Charge and discharge the energy storage element.

With reference to the first aspect, in the eighth implementation manner of the first aspect, it includes:

Display module, connected with the control circuit, used to display the equivalent resistance value;

The communication module is connected with the control circuit to realize wireless and/or wired data transmission;

The early warning module, connected with the control circuit, is used to send out an alarm when the change in the equivalent resistance value reaches the preset threshold.

In the zero-ground resistance monitoring device provided by the embodiment of the present invention, the drive control module is connected to the display module, which can intuitively and conveniently observe the change in resistance between the neutral wire and the ground wire, and it is convenient for maintenance personnel to intuitively check the difference between the neutral wire and the ground wire. The change in resistance is monitored.

The drive control module is connected with the communication module to ensure a certain distance of data transmission, so as to realize the communication between data.

The drive control module is connected to the early warning module. Connecting the early warning module can ensure that the abnormal resistance value of the zero-ground resistance is detected in the first time when the resistance value is abnormal. At the same time, the early warning module can remind the electrician to pay attention to personal safety.

According to the second aspect, the present invention provides a zero-ground resistance monitoring method, including:

Control the charging circuit to turn on and detect the voltage value at both ends of the energy storage element;

Determine whether the voltage value across the energy storage element reaches the preset threshold;

When the charging voltage reaches the preset threshold, when the charging voltage reaches the preset threshold, controlling the energy storage element to switch from a charged state to a discharged state, and determine whether the voltage value between the neutral line and the ground line is zero;

When the voltage value between the neutral wire and the ground wire is zero, the discharge circuit is controlled to be turned on to discharge the energy storage element;

Detect the voltage across the energy storage element and the current in the discharge circuit during the discharge process;

The equivalent resistance value between the neutral wire and the ground wire is calculated according to the voltage at both ends of the energy storage element and the discharge loop current.

The zero-ground resistance monitoring device provided by the embodiment of the present invention judges whether the charging voltage reaches a preset threshold for discharging, and then determines the resistance change of the grounding resistance according to the charging voltage value and the discharge voltage, thereby realizing the monitoring of the zero-ground resistance and passing The threshold information is preset to prevent the voltage from overlapping due to the voltage drop in the power distribution system, and to ensure the accuracy of the monitoring resistance. In order to avoid the failure of the leakage protection caused by the change of the resistance value of the zero-ground resistance; and further ensure the personal safety of the electricity users.

Description of the drawings

In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the specific embodiments or the description of the prior art. Obviously, the appendix in the following description The drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative work, other drawings can be obtained based on these drawings.

Figure 1 is a schematic diagram of the electrical connection of the protective grounding of the TN-S power supply system in the prior art;

Figure 2 is a schematic diagram of the electrical connection of the protective grounding in the existing TT power supply system;

3 is a structural block diagram of a zero-ground resistance monitoring device according to Embodiment 1 of the present invention;

4 is a schematic diagram of the structure of a zero-ground resistance monitoring device according to Embodiment 2 of the present invention;

Fig. 5 is a schematic structural diagram of yet another zero-ground resistance monitoring device according to Embodiment 2 of the present invention;

6 is a flowchart of a zero-ground resistance monitoring method according to Embodiment 3 of the present invention;

Fig. 7 is a schematic structural diagram of a zero-ground resistance monitoring device according to Embodiment 4 of the present invention.

Reference signs:

1-Substation; 2-Electrical device; 10-Energy storage element; 11-Charge circuit; 11(a)-Voltage divider rectifier circuit; 12-Discharge circuit; 13-Sampling circuit; 14-Shaping filter circuit; 14( a)-Shaping filter; 15-control circuit; 15(a)-first drive circuit; 15(b)-second drive circuit; 15(c)-controller; 15(d)-third drive circuit; 16-display module; 17-communication module; 18-warning module; RZ-equivalent resistance; R1-first resistance; R2-second resistance; R3-third resistance; C1-energy storage capacitor; D1-rectifier element; Z1-first switching device; Z2-second switching device; Q1-first controllable element; L-live wire; N-zero wire; PE-ground wire.

Detailed ways

In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work shall fall within the protection scope of the present invention.

In the prior art, the zero-ground resistance can be monitored by using clamp resistance meters, grounding resistance shake meters and other devices to prevent leakage. However, the monitoring of leakage in traditional devices also needs to be operated without power. That is to say, in the existing technology, if the leakage situation needs to be monitored, then the power-consuming equipment needs to be cut off. For industrial equipment, the cut off will undoubtedly affect the production efficiency. In addition, because the zero-to-ground resistance is monitored through power failure, the problem cannot be detected in the first time, which will bring the safety risk of electric shock to the operator of the electrical equipment. Therefore, the zero-ground resistance proposed by the present invention The ground resistance monitoring device can not only perform zero-ground resistance monitoring, but also perform online resistance monitoring to ensure that the resistance value change of the zero-ground resistance can be monitored in the first time, thereby ensuring the personal safety of electrical users.

At the same time, the embodiment of the present invention can also ensure the accuracy of the grounding resistance monitoring data, prevent the leakage protection from failing due to the inaccurate measured resistance value, thereby ensuring the safety of personal electricity use.

As shown in Figure 1, in the TN-S power supply system, between the substation 1 and the electrical device 2, the neutral line N is electrically connected to the protective ground PE at the neutral point of the transformer, and the neutral line N is electrically connected to the ground PE The loop resistance RZ is equal to Rn+Re. (Rn is the resistance of the neutral line and Re is the resistance of the ground line). Since the resistance of the neutral line N in the power distribution system is much smaller than the resistance value of the ground line PE, the measured N- The resistance value of the PE loop can basically reflect the resistance value of the ground wire.

As shown in Figure 2, in the TT power supply system, the protective ground PE between the substation 1 and the electrical device 2 is electrically connected to the earth and the neutral point of the transformer through the ground electrode, and the loop resistance of the neutral line N and the ground line PE is equal to Rs+Ry+Rn+Rd (the loop resistance is the sum of the protective earth wire PE and the resistance of the grounding electrode, Ry is the sum of the neutral point of the transformer and the grounding electrode, Rn is the total resistance of the neutral wire, and Rd is the earth resistance) In the system, since the earth resistance Rd is theoretically infinitely small, and the zero line resistance Rn is actually much smaller than Rs, the actual N-PE loop resistance value is approximately equal to Rs+Ry, which can directly reflect the grounding quality. Therefore, by obtaining the actual resistance value of the N-PE loop in real time, the change of the zero-ground resistance can be reflected.

Example 1

The embodiment of the present invention provides a zero-ground resistance monitoring device, as shown in FIG. 3, including:

Energy storage element 10; the energy storage element 10 can be a capacitor, an inductor, or other elements that store electrical energy.

The charging circuit 11 is respectively connected to the energy storage element 10 and the neutral line N and the live line L of the power supply system, and is used to form a loop for charging the energy storage element 10 by the power supply system.

The discharge circuit 12 is respectively connected to the energy storage element 10 and the neutral line N and the ground line PE of the power supply system to form a loop for the energy storage element 10 to discharge the neutral line N and the ground line PE of the power supply system.

By setting the charging circuit 11 and the discharging circuit 12, it can solve the problem of the unstable numerical voltage drop between the neutral wire N and the ground wire PE in the power distribution system, and the voltage drop generated will be generated by the voltage on the electrical equipment. Overlapping causes the problem of inaccurate zero-ground resistance value, and realizes online monitoring of the zero-ground resistance detection device to prevent leakage protection from failing and endangering personal safety.

The sampling circuit 13 is connected to the discharge circuit 12; it is used to measure the current value in the discharge circuit when the energy storage element 10 is discharged.

The shaping filter circuit 14 is respectively connected to the control circuit 15 and the neutral line, the live line L and the ground line PE of the power supply system; it is used to filter the interference and clutter of the power supply system so that the control circuit 15 can determine the zero crossing time of the power supply system. Optionally, the shaping filter circuit 14 can be a separate integrated module or a circuit composed of discrete components, which is mainly used to filter out the clutter caused by the power supply system and to ensure that the control circuit 15 can obtain an accurate zero-crossing signal. It further satisfies the online measurement and monitoring of the grounding resistance of the power distribution system.

The control circuit 15 is respectively connected to the shaping filter circuit 14, the sampling circuit 13, the charging circuit 11, the discharging circuit 12 and the energy storage element 10, and is used to control the charging circuit 11 and the discharging circuit 12 to switch between charge and discharge and collect the energy storage element 10 The voltage and the voltage drop of the sampling circuit 13 when the energy storage element 10 is discharged, and the discharge current is calculated based on the voltage drop. The equivalent resistance value between the neutral wire and the ground wire PE is calculated based on the voltage and discharge current of the energy storage element 10. The control circuit 15 is used to control the controlled circuits (for example, the shaping filter circuit 14, the sampling circuit 13, the charging circuit 11, the discharging circuit 12, etc.), so that the control circuit 15 can meet real-time monitoring of the equivalent resistance RZ.

The advantage of this embodiment is that the energy storage element is charged through a charging circuit, and the zero-crossing moment of the power supply system is monitored in real time by using a shaping filter circuit and a control circuit. When the control circuit monitors that the voltage between the neutral line and the ground line is zero, the discharge circuit is used to discharge the energy storage element, and the voltage at both ends of the energy storage element during the discharge process is detected at the same time; and the sampling circuit discharges when the energy storage element is discharged. The current value in the loop; finally, the detected voltage and current value are fed back to the control circuit, and the control circuit calculates the equivalent resistance value between the neutral wire and the ground wire according to the obtained voltage and current value to achieve Online measurement and monitoring of the grounding resistance of the power distribution system.

Example 2

The embodiment of the present invention provides a zero-ground resistance monitoring device, which is specifically shown in Figures 4-5, except for the energy storage element 10, the charging circuit 11, the discharging circuit 12, the sampling circuit 13, the shaping filter circuit 14, and the control circuit 15. A display module 16, a communication module 17, and an early warning module 18 are also provided.

The display module 16 is connected to the control circuit 15 for displaying the resistance change of the equivalent resistance RZ between the neutral wire N and the ground wire PE. Optionally, the display module 16 may be a display device such as a liquid crystal screen, a nixie tube, etc., and the display module 16 may display equivalent resistance information or a change chart of the equivalent resistance.

The communication module 17 is connected with the control circuit 15 to realize wireless and/or wired data transmission; the specific transmission method may be: WIFI, Bluetooth, serial, etc. for data transmission.

The early warning module 18 is connected to the control circuit 15 and is used to generate an alarm when the resistance value of the equivalent resistance RZ between the neutral wire N and the ground wire PE reaches a preset threshold; optionally, it can be sent by a buzzer Sound alarm. It can also be a text message alert transmitted by SMS or text.

By connecting the control module 15 with the display module 16, the resistance change between the neutral wire N and the ground wire PE can be observed intuitively and conveniently, so as to facilitate the maintenance personnel to troubleshoot the fault based on the equivalent resistance value.

The control module 15 is connected with the communication module 17, and through data transmission, the communication between the data is realized, and the remote monitoring of the zero-ground resistance in the power supply system is realized.

The control module 15 is connected to the early warning module 18 to ensure that the equivalent resistance value can be detected in the first time when the equivalent resistance value is abnormal, and it can also remind the electricity users to pay attention to personal safety.

Specifically, as shown in FIG. 4, in this embodiment, the energy storage element 10, the charging circuit 11, the control circuit 15, the discharging circuit 12, and the sampling circuit 13 further have:

The voltage dividing and rectifying circuit 11(a) is respectively connected to the neutral line N and the live line L and the first switching device Z1; the voltage dividing and rectifying circuit 11(a) includes: a first resistor R1, a rectifying element D1, and a second resistor R2. Among them, the rectifying element D1 may be a rectifying diode.

Specifically, the voltage divider rectifier circuit 11(a) may be that the first end of the first resistor R1 is connected to the live wire L; the cathode end of the rectifying element D1 is connected to the second end of the first resistor R1, and the anode end of the rectifying element D1 is connected to The first switching device Z1 is connected; the anode end of the rectifying element D1 is also connected to the first end of the second resistor R2. The second end of the second resistor R2 is connected to the neutral line N.

Among them, the first resistor R1 and the second resistor R2 can form a voltage divider circuit, and the voltage divider circuit is used to reduce the input current, ensure the normal operation of the subsequent circuit and prevent excessive voltage/current from damaging the subsequent components. The rectifier element D1 is used to ensure that the output meets the design requirements of DC.

The first switching device Z1 is connected between the output terminal of the voltage dividing rectifier circuit 11(a) and the first terminal of the energy storage element 10. The control terminal of the first switching device Z1 is connected to the control circuit; wherein, the energy storage element 10 It can be the energy storage capacitor C1. Optionally, the first switching device may be a relay.

The first controllable element Q1, the first end of the first controllable element Q1 is connected to the sampling circuit 13, the second end of the first controllable element Q1 is connected to the neutral line N, and the third end of the first controllable element Q1 is connected to the The control circuit 15 is connected. Optionally, the first controllable element Q1 may be a switch tube; the first pole of the switch tube is connected to the control port of the control chip, the second pole of the switch tube is connected to the neutral line of the power supply system, and the third pole of the switch tube is connected to the first pole. For the second end of the resistor R1, the switch tube can be a voltage-controlled device or a current-controlled device.

The first end of the third resistor R3 and the third resistor R3 is connected to the second end of the energy storage element 10, and the second end of the third resistor R3 is connected to the discharge circuit 12.

Optionally, the third resistor R3 is a sampling resistor. The sampling resistor is connected to the first controllable element Q1, and is used to provide a sampling voltage to the control circuit 15 and calculate the current value flowing through the sampling resistor. Using its current value and the voltage across the energy storage element 10, according to Ohm’s law and the known resistance value, the resistance value of the equivalent resistance RZ between the neutral wire N and the ground wire PE can be obtained, so that the resistance change can be monitored Prevent the leakage protection from failing due to the change of the equivalent resistance; ensure the personal safety of the electricity users. Among them, the equivalent resistance RZ may also be a grounding resistance.

The shaping filter circuit 14, wherein the first end of the shaping filter circuit 14 is connected to the control circuit 15, the second end of the shaping filter circuit 14 is connected to the live wire L or the neutral line N, and the third end of the shaping filter circuit 14 is connected to the ground wire PE . In the actual safety of electricity use, the neutral and ground lines on the power supply system will generate partial voltage due to external conditions or poor grounding of the power supply system. The existence of the voltage will make the control circuit unable to accurately identify the zero crossing. At the moment, it can also be considered that there is an interference signal between the neutral wire N and the ground wire PE that affects the normal operation of the zero-ground resistance monitoring device, causing the zero-ground resistance monitoring device to fail to operate normally. If the zero-ground resistance monitoring device fails to operate normally, the safety of electric personnel is very likely to be threatened. Therefore, a shaping filter circuit (shaping filter) is added to the line of the control circuit to monitor the neutral wire N and the ground wire PE to filter out the clutter interference on the power supply system to ensure that the control circuit 15 can accurately determine the zero-crossing moment, so that Its zero-ground resistance monitoring device can accurately monitor the change of equivalent resistance RZ to ensure the safety of electrical users, and solve the problem of numerical instability between the neutral wire N and the ground wire PE in the power distribution system due to the actual power consumption. Because the voltage generated by the neutral wire N and the ground wire PE will overlap with the voltage on the electrical equipment, the detection result of the zero-ground resistance monitoring device will produce errors, which endangers the life and safety of electrical users.

The controller 15(c) is connected to the energy storage element, the sampling circuit, the detection circuit, and the first drive circuit 15(a) and the second drive circuit 15(b) respectively. Optionally, the controller 15(c) can be a control chip such as an ARM or a single-chip microcomputer.

Specifically, the first terminal of the first driving circuit 15(a) is connected to the controller 15(c), and the second terminal and the third terminal of the first driving circuit 15(a) are respectively connected to the third terminal of the first switching device Z1. The first end of the second drive circuit 15(b) is connected to the controller 15(c), and the second end of the second drive circuit 15(b) is connected to the third end of the first controllable element Z1.端连接。 End connection.

Optionally, the driving circuit may also include a signal amplifier for amplifying the control signal to ensure that the circuit or the zero-ground resistance monitoring device can work normally.

The controller 15(c) controls the normally closed contact of the first switching device Z1 to be turned on to charge the energy storage element 10. When the controller 15(c) detects that the voltage across the energy storage element 10 reaches the preset value; the controller 15(c) controls the normally open contact of the first switching device Z1 to be turned on, and the first controllable element Q1 conducts Pass. The energy storage element 10 is discharged. Among them, the shaping filter monitors the voltage between the neutral wire N and the ground wire PE during the charging/discharging process; when the controller 15(c) monitors that the voltage is zero, it will be based on the sum of the voltage across the energy storage element 10 The voltage of the third resistor R3 is used to calculate the current value flowing through the third resistor R3 by using the known third resistor value, and the resistance value of the measured equivalent resistor RZ is calculated by Ohm's law. Among them, the measured equivalent resistance is the grounding resistance between the neutral wire and the ground wire. By monitoring the resistance change, the leakage protection failure caused by the change of the resistance value of the grounding resistance can be prevented; and the personal safety of the electrical users can be guaranteed.

Optionally, as shown in FIG. 5, the zero-ground resistance monitoring device provided in this embodiment may further include:

The third drive circuit 15(d), the first end of the third drive circuit 15(d) is connected to the controller 15(c), and the second and third ends of the third drive circuit 15(d) are connected to the second The third terminal and the fourth terminal of the switching device Z2 are connected. The first end of the second switching device Z2 is connected to the ground PE, and the second end of the second switching device Z2 is connected to the first end of the energy storage element 10. The charging circuit 11 and the discharging circuit 12 are distinguished by setting the third driving circuit 15(d) and the second switching device Z2, so as to realize that the charging and discharging of the energy storage element 10 can be controlled individually. Optionally, the third driving circuit 15(d) and the first driving circuit 15(a) are the same driving circuit; the second switching device Z2 and the first switching device Z1 are the same switching device.

The second switching device Z2 and the first switching device Z1 are arranged as the same switching device, and the third driving circuit 15(d) and the first driving circuit 15(a) are arranged as the same driving circuit, in order to simplify the hardware circuit structure and save circuits Cost, while ensuring the stability of the circuit function.

Example 3

The embodiment of the present invention provides a zero-ground resistance monitoring method, as shown in FIG. 6, including:

S10, controlling the charging circuit to be turned on, and detecting the voltage value at both ends of the energy storage element.

The controller controls the switching device to charge the energy storage element, and the controller also needs to monitor the voltage across the energy storage element.

S11: Determine whether the voltage value at both ends of the energy storage element reaches a preset threshold.

The voltage at both ends of the energy storage element is collected by setting the interval time in the software program, and it is judged whether the threshold in the controller is reached. For example: 40V. If the threshold is reached, execute S12, otherwise return to S10 to continue voltage monitoring.

S12: When the charging voltage reaches a preset threshold, the energy storage element is controlled to switch from the charging state to the discharging state, and it is determined whether the voltage value between the neutral line and the ground line is zero.

S13: When the voltage value between the neutral line and the ground line is zero, the discharge circuit is controlled to be turned on to discharge the energy storage element. Otherwise, return to S11.

S14: Detect the voltage across the energy storage element and the current in the discharge circuit during the discharge process. For example: according to the known resistance value of the third resistor and the detected voltage value of the third resistor, the current value of the third resistor, that is, the current of the discharge loop, can be calculated using Ohm's law.

S15: Calculate the equivalent resistance value between the neutral wire and the ground wire according to the voltage at both ends of the energy storage element and the discharge loop current.

Determine whether the charging voltage reaches the preset threshold value for discharging, and determine the resistance change of the ground resistance according to the charging voltage value and the discharging voltage, so as to realize the monitoring of the zero-ground resistance and solve the problem of voltage overlap through the preset threshold information , To ensure the accuracy of the monitoring data, and then to realize the failure of the leakage protection caused by the change of the zero-ground resistance; to ensure the personal safety of the electrical users.

Optionally, a sampling resistor can also be connected between the neutral wire and the ground wire, and it can also be determined by monitoring the resistance change of the sampling resistor whether it is safe to use electricity in the power distribution system.

Example 4

As shown in FIG. 7, this embodiment provides a zero-ground resistance monitoring device, which can be applied to the method proposed in Embodiment 3.

When the zero-ground resistance monitoring device is powered on, the AC voltage between the live wire L and the neutral wire N passes through a voltage divider circuit composed of a first resistor R1 and a second resistor R2 and a half-wave rectifier circuit composed of a rectifier element D1. At point F, a negative pulsating DC voltage is obtained. After the voltage passes through the normally closed contact of the first switching device Z1 (or a relay), the energy storage capacitor C1 is charged, and the positive terminal of the energy storage capacitor C1 passes through the third The resistor R3 (can be a sampling resistor) and the internal freewheeling diode of the first controllable element Q1 (can be a switching transistor) are connected to the neutral line N to form a charging circuit. When the voltage across the energy storage capacitor C1 reaches the programmed value, The controller 15(c) starts to control the normally open contact of the first switching device Z1 to be closed in preparation for discharge, and then the controller 15(c) monitors _{whether U pen} is zero through the shaping filter 14(a), when U _pen is At zero hour, the controller 15(c) controls the first controllable element Q1 to be turned on, and the voltage stored on the energy storage capacitor C1 passes through the third resistor R3, the first controllable element Q1, the equivalent resistance RZ, and the first The switching device Z1 to point A forms a discharge loop. Since the resistance value of the discharge circuit is fixed, the measured resistance of the neutral wire N and the ground wire PE circuit will directly affect the discharge current of the energy storage capacitor C1. The smaller the equivalent resistance RZ of the energy storage capacitor C1 is The greater the discharge current, the higher the voltage generated on the third resistor R3. The controller 15(c) measures the voltage at points A and B at both ends of the energy storage capacitor C1 and the voltage at both ends of the third resistor R3, and According to the known resistance value of the third resistor R3, and then according to Ohm's law, the equivalent resistance value of the circuit under test can be calculated. After the measurement is completed, the controller 15(c) can display the specific value through the display circuit 16, or The value is sent to the remote server through the communication circuit, so that online real-time monitoring can be realized, thereby reducing the occurrence of safety accidents.

Among them, the display module 16 may be a liquid crystal screen display or a digital tube display; the communication module 17 may realize wired or wireless transmission, such as Bluetooth, WIFI, etc., or a serial port transmission. The early warning module 18 may send an alarm message to give an alarm prompt, or install a buzzer to give an alarm prompt through an alarm sound, so as to remind the user to prevent electric shock accidents caused by a power distribution system protection ground failure.

This embodiment uses the method of instantaneous discharge of capacitors to monitor the loop resistance between the neutral line and the ground line of the distribution line when the alternating current crosses zero, and this embodiment can not cause the protection ground line of the distribution system during the monitoring With dangerous voltage, it will not trigger the residual current to cause the circuit breaker to malfunction. If the resistance value of the protective ground wire is abnormal, the early warning module 18 in this embodiment will issue an early warning to remind the user to prevent the power distribution system from protecting the ground. Line faults cause electric shock accidents.

In addition, when the energy storage capacitor C1 is charged, the AC voltage on the live line L and the neutral line N is divided by the first resistor R1 and the second resistor R2, and rectified by the rectifier element D1, and then obtained directly between the point F and the neutral line N A negative-polarity DC pulsating voltage U _F , which is charged to point A through the normally closed contact of the first switching device Z1, and charges the energy storage capacitor C1. At this time, the point B where the energy storage capacitor C1 and the third resistor R1 are connected is positive The voltage, point B passes through the third resistor R1 and the first controllable element Q1 (at this time, the first controllable element Q1 is in the state of forward blocking and reverse through the internal freewheeling diode) and the neutral line N forms a charging circuit, which is stored After the voltage of the capacitor C1 has been charged for multiple cycles, the voltage U _AB ≈ the peak voltage of the negative half cycle of _{U F.}

The controller 14(c) always measures the voltage of point A and point B during the charging process. When the voltage reaches the programmed value (usually between 30-40 volts), it will pass through the first drive circuit 15(a) , Control the first switching device Z1 to pull in, and make the distribution line PE connected to point A through the normally open contact of the first switching device Z1 to prepare for the discharge of the energy storage capacitor C1, and then the controller 15(c) passes _{The shaping filter 14(a) monitors whether the voltage U pen} between the neutral line N and the ground line PE crosses zero. When U _PEN =0, the controller 15(c) controls via the second drive circuit 15(b) The first controllable element Q1 is turned on. At this time, the current on the energy storage capacitor C1 starts at point B, passes through the third resistor R1, the energy storage capacitor Q1, the neutral line N and the ground PE, and the neutral-ground loop is equivalent Resistor RZ, through point C, the normally open contact of the first switching device Z1, returns to the negative electrode A of the energy storage capacitor C1 to form a discharge circuit. Because in the discharge circuit of the energy storage capacitor C1, the third resistor R1 and the first can The resistance value of the control element Q1 is a fixed value, so it can be seen that the equivalent resistance RZ of the measured zero line N and the ground PE loop determines the size of the instantaneous discharge current of the energy storage capacitor C1. The smaller the equivalent resistance RZ, the storage The greater the instantaneous discharge current of the energy capacitor C1, the higher the voltage generated on the third resistor R3. Therefore, according to Ohm's law:

U _A ＝U _C ＝I*RZ;

U _B ＝I*(R3+R _Q1 );

Eliminate and merge the I of the two formulas above to obtain: U _A /RZ = U _B /(R3+R _Q1 );

Derive RZ=U _A /U _B *(R3+R _Q1 );

It can be seen from the above formula that when measuring the voltage at point A and point B during discharge, the resistance value of the equivalent resistance RZ of the neutral line N and the ground PE loop can be calculated using the controller 15(c). Among them, the controller 15(c) can directly display the value of the monitored equivalent resistance of the neutral wire N and the ground wire PE loop through the display module 16, or it can be sent to the network server through the communication module 17. When the controller 15(c ) When the monitored equivalent resistance of the neutral wire N and the ground wire PE loop exceeds the programmed value, the controller 15(c) can issue a local warning through the warning circuit 18. Among them, an energy storage capacitor C1 that can switch between charging and discharging through the first switching device Z1 is provided between the neutral line N and the ground line PE, and a third resistor R3 is provided between the energy storage capacitor C1 and the neutral line N. During the discharging process of the energy storage capacitor C1, the equivalent resistance RZ of the measured circuit will be directly related to the size of the discharge current of the energy storage capacitor C1. The third resistor R3 connected in series to the discharge circuit of the energy storage capacitor C1 will connect the energy storage capacitor C1. The discharge current is directly converted into a voltage signal and sent to the controller 15(c) for analysis. A first controllable element Q1 is provided between the discharge circuit of the energy storage capacitor C1 and the neutral line N. When the energy storage capacitor C1 is charged, the first controllable element Q1 bears the negative direction voltage and its internal freewheeling diode is turned on as a storage capacitor. The charging current of the energy capacitor C1 provides a path; when the energy storage capacitor C1 is discharged, the relay Z3 connects the negative terminal of the energy storage capacitor C1 with the ground PE, and the first controllable element Q1 bears the positive voltage and stops. When the device 15(c) Q1 is turned on, the current of the energy storage capacitor C1 passes through the first controllable element Q1 and the ground wire PE to form a discharge circuit.

In addition, voltage divider resistors R1, R2 and rectifier diode D1 are set between the live line L and the neutral line N. The voltage U _LN between the live line L and the neutral line N is divided by R3, R4 and rectified by the rectifier element D1 to obtain a The DC pulsating low voltage, the voltage drop charges the energy storage capacitor C1 through the first switching device Z1. A zero-crossing signal shaping filter 14(a) is set between the neutral wire N and the ground wire PE, and the controller 15(c) completes the zero-crossing detection, so that the controller 15(c) can perform the zero-crossing detection when the AC voltage crosses zero. Trigger the energy storage capacitor C1 to discharge, and measure the equivalent resistance of the neutral and ground loops.

By detecting the equivalent resistance in real time, not only can it be ensured that the leakage protection failure caused by the change of the resistance value of the grounding resistance can be prevented; it can also ensure the personal safety of the electrical users and ensure the measurement accuracy.

Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations fall within the scope of the appended claims. Within the limited range.

Claims (10)

A zero-ground resistance monitoring device, which is characterized in that it comprises: Energy storage element A charging circuit, respectively connected to the energy storage element and the neutral line and the live line of the power supply system, and is used to form a loop for charging the energy storage element by the power supply system; A discharge circuit, respectively connected to the energy storage element and the neutral line and the ground line of the power supply system, and is used to form a circuit for the energy storage element to discharge the neutral line and the ground line of the power supply system; A sampling circuit, connected to the discharge circuit; used to measure the current value in the discharge loop when the energy storage element is discharged; The shaping filter circuit is respectively connected to the control circuit and the neutral wire, live wire and ground wire of the power supply system; used to filter out the interference and clutter of the power supply system, so that the control circuit can determine the zero-crossing time of the power supply system; The control circuit is respectively connected to the shaping filter circuit, sampling circuit, charging circuit, discharging circuit and energy storage element; used to control the charging circuit and the discharging circuit to switch between charging and discharging and to collect the voltage of the energy storage element and the sampling The voltage drop of the circuit when the energy storage element is discharged and the discharge current is calculated based on the voltage drop, and the equivalent resistance value between the neutral wire and the ground wire is calculated based on the voltage of the energy storage element and the discharge current . The device according to claim 1, wherein the charging circuit comprises: A voltage divider rectifier circuit, which is respectively connected to the neutral wire, the live wire, and the first switching device; The first end of the first switching device is connected to the output end of the voltage dividing rectifier circuit, the second end of the first switching device is connected to the first end of the energy storage element, and the The third end and the fourth end are connected to the control circuit; Wherein, the voltage dividing rectifier circuit further includes: The first resistor, the first end of the first resistor is connected to the live wire, the second end of the first resistor is connected to the first end of the rectifier device, and the second end of the rectifier device is connected to the second resistor The first end is connected to the first end of the first switching device, and the second end of the second resistor is connected to the neutral line. The device according to claim 2, wherein the discharge circuit comprises: The first controllable element, the first end of the first controllable element is connected to the sampling circuit, the second end of the first controllable element is connected to the neutral line, and the first end of the first controllable element is connected to the neutral line. The third terminal is connected with the control circuit. The device according to claim 3, wherein the sampling circuit comprises: A third resistor, the first end of the third resistor is connected to the second end of the energy storage element, and the second end of the third resistor is connected to the discharge circuit. The device according to claim 1, wherein the first end of the shaping filter circuit is connected to the control circuit, the second end of the shaping filter circuit is connected to the live wire or the neutral wire, and the shaping filter circuit The third end of is connected to the ground wire. The device according to claim 3, wherein the control circuit comprises: A controller, the controller is respectively connected with the energy storage element, the sampling circuit, the shaping filter circuit, the first driving circuit and the second driving circuit; The first terminal of the first driving circuit is connected to the controller, and the second terminal and the third terminal of the first driving circuit are respectively connected to the third terminal and the fourth terminal of the first switching device; The first end of the second drive circuit is connected to the controller, and the second end of the second drive circuit is connected to the third end of the first controllable element. The device according to claim 6, wherein the control circuit further comprises: A third driving circuit, the first terminal of the third driving circuit is connected to the controller, and the second terminal and the third terminal of the third driving circuit are respectively connected to the third terminal and the fourth terminal of the second switching device connect; The first end of the second switching device is connected to the ground wire, and the second end of the second switching device is connected to the first end of the energy storage element; Wherein, the third driving circuit and the first driving circuit are the same driving circuit; the second switching device and the first switching device are the same switching device. 7. The device according to claim 7, comprising: the controller, connected to the first driving circuit, and the first driving circuit connected to the first switching device; for switching the charging The circuit and the discharge circuit are used to charge and discharge the energy storage element. The device according to claim 1, further comprising: A display module, connected to the control circuit, for displaying the equivalent resistance value; A communication module, connected to the control circuit, for realizing wireless and/or wired data transmission; An early warning module, connected to the control circuit, is used to send an alarm when the change in the equivalent resistance value reaches a preset threshold. A zero-ground resistance monitoring method, characterized in that it is used in the zero-ground resistance monitoring device according to any one of claims 1 to 9, and the method comprises: Controlling the charging circuit to be turned on, and detecting the voltage value at both ends of the energy storage element; Determining whether the voltage value across the energy storage element reaches a preset threshold; When the charging voltage reaches a preset threshold, controlling the energy storage element to switch from a charging state to a discharging state, and judging whether the voltage value between the neutral line and the ground line is zero; When the voltage value between the neutral wire and the ground wire is zero, controlling the discharging circuit to turn on to discharge the energy storage element; Detecting the voltage across the energy storage element and the current of the discharge loop during the discharge; The equivalent resistance value between the neutral wire and the ground wire is calculated according to the voltage at both ends of the energy storage element and the discharge loop current.

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