A zero-to-ground resistance monitoring device and method

Abstract

The present invention relates to the field of electricity safety technology, and specifically to a zero-ground resistance monitoring device and method. It includes: an energy storage element, a charging circuit, a discharging circuit, a sampling circuit, a shaping filter circuit and a control circuit. The energy storage element is charged by the charging circuit, and the zero-crossing moment of the power supply system is monitored in real time by the shaping filter circuit and the control circuit. When the control circuit detects 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; and the sampling circuit measures the current value in the discharge circuit when the energy storage element is discharged; finally, the detected voltage and current values ​​are fed back to the control circuit, and the control circuit calculates the equivalent resistance value between the neutral line and the ground line according to the obtained voltage and current values, so as to realize online measurement and monitoring of the grounding resistance of the distribution system.

Description

Technical Field

[0001] The present invention relates to the technical field of electricity safety, and in particular to a zero-to-ground resistance monitoring device and method. Background Art

[0002] Grounding protection is an important technical measure to ensure electricity safety. Usually, when the grounding protection system is normal, even if the electrical appliance leaks electricity, no accidental electric shock will occur, because the leaked dangerous voltage will be introduced into the earth by the grounding wire and generate a large enough fault current to make the air switch or leakage switch automatically cut off the power supply. However, an important technical indicator to achieve this goal is the grounding resistance value.

[0003] In practical applications, the grounding resistance of protective grounding may increase due to a series of reasons such as changes in the geological environment of the grounding electrode, oxidation of the electrical connection point of the grounding wire, mechanical failure of the grounding wire, etc., thereby losing its effective protection and causing electric shock and electrical fire accidents. In addition, most grounding resistance measurement devices in the prior art require auxiliary electrodes to be set on the ground or to measure a closed loop, and cannot achieve online measurement and monitoring of the grounding resistance of the distribution system. Summary of the invention

[0004] In view of this, an embodiment of the present invention provides a zero-ground resistance monitoring device and method to solve the problem in the prior art that it is impossible to achieve online measurement and monitoring of the grounding resistance of a power distribution system.

[0005] According to a first aspect, the present invention provides a zero-to-ground resistance monitoring device, comprising:

[0006] Energy storage components;

[0007] A charging circuit is connected to the energy storage element and the neutral line and the live line of the power supply system respectively, and is used to form a loop for charging the energy storage element using the power supply system;

[0008] A discharge circuit is connected to the energy storage element and the neutral line and the ground line of the power supply system respectively, and is used to form a loop for the energy storage element to discharge the neutral line and the ground line of the power supply system;

[0009] The sampling circuit is connected to the energy storage element and the discharge circuit; and is used to measure the current value in the discharge circuit when the energy storage element is discharged;

[0010] The shaping filter circuit is connected to the control circuit and the neutral line, live line and ground line of the power supply system respectively; it is used to filter out the interference noise of the power supply system so that the control circuit can judge the zero-crossing moment of the power supply system;

[0011] The control circuit is connected to the shaping filter circuit, the sampling circuit, the charging circuit, the discharging circuit and the energy storage element respectively; it is used to control the charging circuit and the discharging circuit to perform charging and discharging switching and collect the voltage of the energy storage element and the voltage drop of the sampling circuit when the energy storage element is discharged, and calculate the discharge current according to the voltage drop, and calculate the equivalent resistance value between the neutral line and the ground line based on the voltage and discharge current of the energy storage element.

[0012] The zero-to-ground resistance monitoring device provided by the embodiment of the present invention charges the energy storage element through the charging circuit, and uses the shaping filter circuit and the control circuit to monitor the zero-crossing moment of the power supply system in real time. When the control circuit detects 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; and the sampling circuit measures the current value in the discharge loop when the energy storage element is discharged; finally, the detected voltage and current values ​​are fed back to the control circuit, and the control circuit calculates the equivalent resistance value between the neutral line and the ground line based on the obtained voltage and current values, so as to realize online measurement and monitoring of the grounding resistance of the distribution system.

[0013] In combination with the first aspect, in a first implementation of the first aspect, the charging circuit includes:

[0014] A voltage dividing and rectifying circuit is connected to the neutral line, the ground line and the first switch device respectively;

[0015] The first end of the first switch device is connected to the output end of the voltage divider rectifier circuit, the second end of the first switch device is connected to the first end of the energy storage element, and the third end and the fourth end of the first switch device are connected to the control circuit;

[0016] The voltage divider rectifier circuit further includes:

[0017] A first resistor, a first end of the first resistor is connected to the live wire, a second end of the first resistor is connected to the first end of the rectifier device, a second end of the rectifier device is connected to the first end of the second resistor and the first end of the first switch device, and a second end of the second resistor is connected to the neutral wire.

[0018] The zero-to-ground resistance monitoring device provided in the embodiment of the present invention uses a voltage divider rectifier circuit to convert the AC power in the power supply system into DC power to ensure that the zero-to-ground resistance monitoring device can work normally. The DC power is output to the energy storage element through the first switch device to complete the action of charging the energy storage element, thereby providing initial conditions for subsequent online monitoring, ensuring that the subsequent circuits / elements can work normally and then implement online zero-to-ground resistance monitoring of the power supply system.

[0019] In combination with the first aspect, in a second implementation of the first aspect, the discharge circuit includes:

[0020] A first controllable element, wherein a first end of the first controllable element is connected to the sampling circuit, a second end of the first controllable element is connected to the neutral line, and a third end of the first controllable element is connected to the control circuit.

[0021] The zero-to-ground resistance monitoring device provided by the embodiment of the present invention is provided with a first controllable element to control the on-off of the circuit using the conduction characteristics of the controllable element. When the energy storage element meets the discharge condition, the first controllable element is turned on to discharge the energy storage element. This ensures that the power supply system can be monitored in real time, and further realizes real-time online zero-to-ground resistance monitoring.

[0022] In combination with the first aspect, in a third implementation of the first aspect, the sampling circuit includes:

[0023] A third resistor, wherein a first end of the third resistor is connected to the second end of the energy storage element, and a second end of the third resistor is connected to the discharge circuit.

[0024] The zero-to-ground resistance monitoring device provided by the embodiment of the present invention is provided with a third resistor, and the current value flowing through the third resistor of the energy storage element at the time of discharge is collected by the third resistor, and the obtained current value is sent to the controller, and the collected data is calculated by the method set in the controller to obtain the collection result. Thereby, the zero-to-ground resistance is further measured in real time, and the electricity user can judge the leakage of the zero-to-ground resistance according to the collection result, so as to ensure the life safety of the human body in time.

[0025] In combination with the first aspect, in a 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 ground wire.

[0026] The zero-to-ground resistance monitoring device provided in the embodiment of the present invention utilizes a shaping filter circuit to filter out interference signals between power supply systems, which is conducive to accurately determining the zero-crossing moment of the power supply system.

[0027] In combination with the first aspect, in a fifth implementation of the first aspect, the control circuit includes:

[0028] A controller, the controller is connected to the energy storage element, the sampling circuit, the detection circuit, the first drive circuit and the second drive circuit respectively;

[0029] The first end of the first driving circuit is connected to the controller, and the second end and the third end of the first driving circuit are connected to the third end and the fourth end of the first switching device respectively;

[0030] The first end of the second driving circuit is connected to the controller, and the second end of the second driving circuit is connected to the third end of the first controllable element.

[0031] The zero-to-ground resistance monitoring device provided in the embodiment of the present invention controls the charging and discharging of the energy storage element by setting a controller to control the first drive circuit and the second drive circuit, so as to realize intelligent monitoring of the state of the power supply system.

[0032] In combination with the first aspect, in a sixth implementation of the first aspect, the control circuit further includes:

[0033] a third driving circuit, wherein a first terminal of the third driving circuit is connected to the controller, and a second terminal and a third terminal of the third driving circuit are connected to a third terminal and a fourth terminal of the second switching device respectively;

[0034] The zero-to-ground resistance monitoring device provided in the embodiment of the present invention is formed so that its control circuit can meet the requirements of independent charging and discharging by setting a third driving circuit, thereby realizing independent control of the zero-to-ground resistance monitoring device and improving the flexibility of the zero-to-ground resistance monitoring device.

[0035] A first end of the second switch device is connected to the ground line, and a second end of the second switch device is connected to the first end of the energy storage element;

[0036] 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.

[0037] The zero-to-ground resistance monitoring device provided in an embodiment of the present invention sets the second switching device and the first switching device to be the same switching device, and sets the third driving circuit and the first driving circuit to be the same driving circuit, so as to simplify the hardware circuit structure, save circuit costs, and ensure the stability of the circuit function.

[0038] In combination with the first aspect, in a seventh implementation of the first aspect, it includes: a controller connected to the first drive circuit, the first drive circuit is connected to the first switching device; and is used to switch the charging circuit and the discharging circuit to realize charging and discharging of the energy storage element.

[0039] In combination with the first aspect, in an eighth implementation of the first aspect, the method includes:

[0040] A display module, connected to the control circuit, for displaying an equivalent resistance value;

[0041] A communication module, connected to the control circuit, for realizing wireless and / or wired data transmission;

[0042] The early warning module is connected to the control circuit and is used to issue an alarm when the change of the equivalent resistance value reaches a preset threshold.

[0043] The zero-to-ground resistance monitoring device provided in the embodiment of the present invention has a driving control module connected to a display module, which can intuitively and conveniently observe the change in resistance between the zero line and the ground line, making it convenient for maintenance personnel to intuitively monitor the change in resistance between the zero line and the ground line.

[0044] The drive control module is connected to the communication module to ensure data transmission over a certain distance, thereby realizing communication between data.

[0045] The drive control module is connected to the early warning module. Connecting the early warning module can ensure that in the event of an abnormal resistance value, the abnormal resistance value of the zero-to-ground resistance is detected in the first time. At the same time, the early warning module can remind electricity users to pay attention to personal safety.

[0046] According to a second aspect, the present invention provides a zero-to-ground resistance monitoring method, comprising:

[0047] Control the charging circuit to be turned on and detect the voltage value at both ends of the energy storage element;

[0048] Determine whether the voltage value across the energy storage element reaches a preset threshold;

[0049] When the charging voltage reaches a preset threshold, the energy storage element is controlled to change from a charging state to a discharging state, and it is determined whether the voltage value between the neutral line and the ground line is zero;

[0050] 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;

[0051] Detect the voltage across the energy storage element and the current in the discharge circuit during the discharge process;

[0052] The equivalent resistance value between the neutral line and the ground line is calculated based on the voltage across the energy storage element and the discharge loop current.

[0053] The zero-to-ground resistance monitoring device provided by the embodiment of the present invention determines whether the charging voltage reaches a preset threshold value for discharge, 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-to-ground resistance and preventing the voltage from overlapping due to the voltage drop in the power distribution system through the preset threshold information, thereby ensuring the accuracy of the monitored resistance value. This avoids the failure of leakage protection caused by the change of the zero-to-ground resistance value, and further ensures the personal safety of electricity users. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0055] Figure 1 It is a schematic diagram of electrical connection of protective grounding of TN-S power supply system in the prior art;

[0056] Figure 2 It is a schematic diagram of the electrical connection of protective earthing in the existing TT power supply system;

[0057] Figure 3 is a structural block diagram of a zero-to-ground resistance monitoring device according to Embodiment 1 of the present invention;

[0058] Figure 4 is a schematic structural diagram of a zero-to-ground resistance monitoring device according to Embodiment 2 of the present invention;

[0059] Figure 5 is a structural schematic diagram of another zero-to-ground resistance monitoring device according to Embodiment 2 of the present invention;

[0060] Figure 6 is a flow chart of a method for monitoring zero-to-ground resistance according to Embodiment 3 of the present invention;

[0061] Figure 7 4 is a schematic diagram of the structure of a zero-to-ground resistance monitoring device according to Example 4 of the present invention.

[0062] Reference numerals:

[0063] 1-substation; 2-electrical device; 10-energy storage element; 11-charging circuit; 11(a)-voltage-dividing rectifier circuit; 12-discharging 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-early warning module; RZ-equivalent resistor; R1-first resistor; R2-second resistor; R3-third resistor; C1-energy storage capacitor; D1-rectifier element; Z1-first switch device; Z2-second switch device; Q1-first controllable element; L-live wire; N-neutral wire; PE-ground wire. DETAILED DESCRIPTION

[0064] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, 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 are within the scope of protection of the present invention.

[0065] In the prior art, the zero-to-ground resistance can be monitored by using devices such as clamp ohmmeters and ground resistance megohmmeters to prevent leakage. However, in traditional devices, monitoring leakage also requires operation without power supply. That is to say, in the prior art, if leakage needs to be monitored, the electrical equipment needs to be powered off. For industrial equipment, power outage will undoubtedly affect production efficiency. In addition, since the zero-to-ground resistance is monitored by powering off, the problem cannot be detected in the first time, which will bring safety risks of electric shock to the operators of the electrical equipment. Therefore, the zero-to-ground resistance monitoring device proposed in the present invention can not only monitor the zero-to-ground resistance, but also monitor the resistance online, ensuring that the resistance value change of the zero-to-ground resistance can be monitored in the first time, thereby ensuring the personal safety of the electricity users.

[0066] At the same time, the embodiment of the present invention can also ensure the accuracy of ground resistance monitoring data, prevent leakage protection failure due to inaccurate resistance measurement, and thus ensure personal electricity safety.

[0067] like Figure 1 As shown, 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 line PE at the neutral point of the transformer, and the loop resistance RZ between the neutral line N and the ground line PE is equal to Rn+Re. (Rn is the neutral line resistance, Re is the ground line resistance). Since the resistance of the neutral line N in the distribution system is much smaller than the resistance value of the ground line PE, the measured N-PE loop resistance value can basically reflect the resistance value of the ground line.

[0068] And as Figure 2As shown, in the TT power supply system, the protective ground wire 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 grounding electrode, and the loop resistance between the neutral wire N and the ground wire PE is equal to Rs+Ry+Rn+Rd (the loop resistance is the sum of the protective ground wire PE and the grounding electrode resistance, Ry is the sum of the transformer neutral point and the grounding electrode, Rn is the total resistance value of the neutral wire, and Rd is the earth resistance). In the power distribution system, since the earth resistance Rd is infinitely small in theory 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 N-PE loop resistance value in real time, the change of the zero-ground resistance can be reflected.

[0069] Example 1

[0070] The embodiment of the present invention provides a zero-ground resistance monitoring device, such as Figure 3 As shown, including:

[0071] Energy storage element 10; wherein the energy storage element 10 can be a component capable of storing electrical energy, such as a capacitor or an inductor.

[0072] The charging circuit 11 is connected to the energy storage element 10 and the neutral line N and the live line L of the power supply system respectively, and is used to form a loop for charging the energy storage element 10 using the power supply system.

[0073] The discharge circuit 12 is connected to the energy storage element 10 and the neutral line N and the ground line PE of the power supply system respectively, and is used 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.

[0074] By setting up the charging circuit 11 and the discharging circuit 12, it is possible to solve the problem of unstable voltage drop between the neutral line N and the ground line PE in the power distribution system, and the problem that the voltage drop will overlap the voltage on the electrical equipment and cause inaccurate zero-to-ground resistance value, and realize online monitoring of the zero-to-ground resistance detection device to prevent leakage protection from failing and endangering personal safety.

[0075] The sampling circuit 13 is connected to the discharge circuit 12 and is used to measure the current value in the discharge circuit when the energy storage element 10 is discharged.

[0076] The shaping filter circuit 14 is connected to the control circuit 15 and the neutral line, live line L and ground line PE of the power supply system respectively; it is used to filter out the interference clutter of the power supply system so that the control circuit 15 can determine the zero-crossing moment 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, ensure that the control circuit 15 can obtain an accurate zero-crossing signal, and further meet the online measurement and monitoring of the grounding resistance of the distribution system.

[0077] The control circuit 15 is 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 respectively, and is used to control the charging circuit 11 and the discharging circuit 12 to perform charging and discharging switching and collect the voltage of the energy storage element 10 and the voltage drop of the sampling circuit 13 when the energy storage element 10 is discharged, and calculate the discharge current according to the voltage drop. The equivalent resistance value between the neutral line and the ground line 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 circuit (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 the real-time monitoring of the equivalent resistance RZ.

[0078] The advantage of this embodiment is that the energy storage element is charged by the charging circuit, and the zero-crossing moment of the power supply system is monitored in real time by the shaping filter circuit and the control circuit. When the control circuit detects that the voltage between the neutral line and the ground line is zero, the energy storage element is discharged by the discharge circuit, and the voltage at both ends of the energy storage element is detected during the discharge process; and the sampling circuit measures the current value in the discharge circuit when the energy storage element is discharged; finally, the detected voltage and current values ​​are fed back to the control circuit, and the control circuit calculates the equivalent resistance value between the neutral line and the ground line based on the obtained voltage and current values, so as to realize online measurement and monitoring of the grounding resistance of the distribution system.

[0079] Example 2

[0080] The embodiment of the present invention provides a zero-ground resistance monitoring device, specifically Figure 4-5 As shown, in addition to the energy storage element 10 , the charging circuit 11 , the discharging circuit 12 , the sampling circuit 13 , the shaping and filtering circuit 14 , and the control circuit 15 , a display module 16 , a communication module 17 and an early warning module 18 are also provided.

[0081] The display module 16 is connected to the control circuit 15 and is used to display the resistance change of the equivalent resistor RZ between the neutral line N and the ground line PE. Optionally, the display module 16 can be a display device such as an LCD screen or a digital tube, and the display module 16 can display equivalent resistance information or a change chart of equivalent resistance.

[0082] The communication module 17 is connected to the control circuit 15 to realize wireless and / or wired data transmission; the specific transmission mode can be: WIFI, Bluetooth, serial and other modes for data transmission.

[0083] The early warning module 18 is connected to the control circuit 15 and is used to generate an alarm when the resistance change of the equivalent resistor RZ between the neutral line N and the ground line PE reaches a preset threshold value; optionally, an audible alarm can be generated by a buzzer, or a text message alarm can be generated by SMS or text transmission.

[0084] By connecting the control module 15 with the display module 16 , the change of the resistance between the neutral line N and the ground line PE can be observed intuitively and conveniently, so that maintenance personnel can troubleshoot faults according to the equivalent resistance value.

[0085] The control module 15 is connected to the communication module 17 to realize data communication and remote monitoring of the zero-to-ground resistance in the power supply system by performing data transmission.

[0086] The control module 15 is connected to the early warning module 18 to ensure that in the event of an abnormal equivalent resistance value, it can be detected in the first place, and at the same time, it can also remind electricity users to pay attention to personal safety.

[0087] Specifically, Figure 4 As shown, in this embodiment, the energy storage element 10, the charging circuit 11, the control circuit 15, the discharge circuit 12 and the sampling circuit 13 also have:

[0088] The voltage-dividing rectifier circuit 11 (a) is connected to the neutral line N, the live line L and the first switch device Z1 respectively; the voltage-dividing rectifier circuit 11 (a) includes: a first resistor R1, a rectifier element D1 and a second resistor R2. The rectifier element D1 can be a rectifier diode.

[0089] Specifically, the voltage divider rectifier circuit 11 (a) can be a first end of a first resistor R1 connected to a live wire L; a cathode end of a rectifier element D1 connected to a second end of the first resistor R1, an anode end of the rectifier element D1 connected to a first switch device Z1; an anode end of the rectifier element D1 also connected to a first end of a second resistor R2. A second end of the second resistor R2 is connected to a neutral wire N.

[0090] The first resistor R1 and the second resistor R2 can form a voltage divider circuit, which 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 the DC.

[0091] The first switch device Z1 is connected between the output end of the voltage divider rectifier circuit 11 (a) and the first end of the energy storage element 10, and the control end of the first switch device Z1 is connected to the control circuit; wherein the energy storage element 10 can be an energy storage capacitor C1. Optionally, the first switch device can be a relay.

[0092] A first controllable element Q1, a first end of the first controllable element Q1 is connected to the sampling circuit 13, a second end of the first controllable element Q1 is connected to the neutral line N, and a third end of the first controllable element Q1 is connected to the control circuit 15. Optionally, the first controllable element Q1 may be a switch tube; a first electrode of the switch tube is connected to a control port of a control chip, a second electrode of the switch tube is connected to a neutral line of a power supply system, and a third electrode of the switch tube is connected to a second end of the first resistor R1, and the switch tube may be a voltage-controlled device or a current-controlled device.

[0093] A third resistor R3 , wherein a first end of the third resistor R3 is connected to a second end of the energy storage element 10 , and a second end of the third resistor R3 is connected to the discharge circuit 12 .

[0094] 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. By using the 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 resistor RZ between the neutral line N and the ground line PE can be obtained, so that the failure of leakage protection caused by the change of the equivalent resistor value can be prevented by monitoring the resistance change; and the personal safety of electricity users can be ensured. Among them, the equivalent resistor RZ can also be a grounding resistor.

[0095] A 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 wire N, and the third end of the shaping filter circuit 14 is connected to the ground wire PE. In actual electricity safety, some voltage will be generated on the neutral wire and the ground wire of the power supply system due to external conditions or poor grounding of the power supply system. The existence of this voltage will make the control circuit unable to accurately identify the zero-crossing 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-to-ground resistance monitoring device, causing the zero-to-ground resistance monitoring device to fail to operate normally. If the zero-to-ground resistance monitoring device cannot operate normally, the safety of the personnel using electricity is likely to be threatened. Therefore, by adding a shaping filter circuit (shaping filter) to the line of the control circuit monitoring the neutral line N and the ground line PE to filter out the clutter interference on the power supply system, it is ensured that the control circuit 15 can accurately determine the zero-crossing moment, so that its zero-to-ground resistance monitoring device can accurately monitor the change of the equivalent resistance RZ to ensure the safety of electricity users, and solve the problem of unstable voltage drop between the neutral line N and the ground line PE due to actual power consumption in the power distribution system, and because the voltage generated by the neutral line N and the ground line PE will overlap with the voltage on the electrical equipment, the detection result of the zero-to-ground resistance monitoring device will produce errors, endangering the life safety of electricity users.

[0096] The controller 15 (c) is connected to the energy storage element, the sampling circuit, the detection circuit, 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 ARM or a single-chip microcomputer.

[0097] Specifically, the first end of the first drive circuit 15(a) is connected to the controller 15(c), and the second and third ends of the first drive circuit 15(a) are respectively connected to the third and fourth ends 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.

[0098] Optionally, the driving circuit may further include: a signal amplifier for amplifying the control signal to ensure that the circuit or the zero-to-ground resistance monitoring device can work normally.

[0099] The controller 15 (c) controls the normally closed contact of the first switch 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 a preset value; the controller 15 (c) controls the normally open contact of the first switch device Z1 to be turned on, and the first controllable element Q1 is turned on. The energy storage element 10 is discharged. In the charging / discharging process, the shaping filter monitors the voltage between the neutral line N and the ground line PE; when the controller 15 (c) detects that the voltage is zero, the current value flowing through the third resistor R3 is calculated based on the voltage across the energy storage element 10 and the voltage of the third resistor R3, and the resistance value of the measured equivalent resistor RZ is calculated by Ohm's law. The measured equivalent resistor is the grounding resistance between the neutral line and the ground line. By monitoring the resistance change, the failure of leakage protection caused by the change of the grounding resistance value can be prevented; and the personal safety of electricity users can be guaranteed.

[0100] Optional, such as Figure 5 As shown, the zero-to-ground resistance monitoring device provided in this embodiment may further include:

[0101] 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 end and the third end of the third drive circuit 15(d) are respectively connected to the third end and the fourth end of the second switch device Z2. The first end of the second switch device Z2 is connected to the ground line PE, and the second end of the second switch device Z2 is connected to the first end of the energy storage element 10. By setting the third drive circuit 15(d) and the second switch device Z2, the charging circuit 11 and the discharging circuit 12 are distinguished to achieve the ability to separately control the charging and discharging of the energy storage element 10. Optionally, the third drive circuit 15(d) and the first drive circuit 15(a) are the same drive circuit; the second switch device Z2 and the first switch device Z1 are the same switch device.

[0102] The second switch device Z2 and the first switch device Z1 are set as the same switch device, and the third drive circuit 15 (d) and the first drive circuit 15 (a) are set as the same drive circuit, so as to simplify the hardware circuit structure, save circuit cost, and ensure the stability of circuit function.

[0103] Example 3

[0104] The embodiment of the present invention provides a method for monitoring zero-ground resistance. Figure 6 Shown include:

[0105] S10, controlling the charging circuit to be turned on, and detecting the voltage value across the energy storage element.

[0106] The controller controls the switch device to charge the energy storage element, and the controller also needs to monitor the voltage across the energy storage element.

[0107] S11, determining whether the voltage value across the energy storage element reaches a preset threshold.

[0108] The voltage across the energy storage element is collected by setting an interval in the software program, and judging 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.

[0109] S12, when the charging voltage reaches a preset threshold, the energy storage element is controlled to change from a charging state to a discharging state, and it is determined whether the voltage value between the neutral line and the ground line is zero.

[0110] 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.

[0111] S14, detecting the voltage across the energy storage element and the current of the discharge circuit during the discharge process. For example, based on 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 circuit, can be calculated using Ohm's law.

[0112] S15, calculating the equivalent resistance value between the neutral line and the ground line according to the voltage across the energy storage element and the discharge loop current.

[0113] Determine whether the charging voltage reaches the preset threshold value for discharge, and determine the change in grounding resistance based on the charging voltage value and the discharge voltage, thereby realizing the monitoring of the zero-to-ground resistance and solving the problem of voltage overlap through the preset threshold information, ensuring the accuracy of the monitoring data, and then realizing the failure of leakage protection caused by the change in zero-to-ground resistance; ensuring the personal safety of electricity users.

[0114] Optionally, a sampling resistor may be connected between the neutral line and the ground line, and whether the power consumption in the power distribution system is safe may be determined by monitoring the resistance change of the sampling resistor.

[0115] Example 4

[0116] like Figure 7 As shown, this embodiment provides a zero-to-ground resistance monitoring device, which can be applied to the method proposed in Example 3.

[0117] When the zero-to-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, and a negative polarity pulsating DC voltage is obtained at point F. After the voltage passes through the normally closed contact of the first switch device Z1 (which can also be a relay), the energy storage capacitor C1 is charged. The positive polarity end of the energy storage capacitor C1 passes through the third resistor R3 (which can be a sampling resistor) and the internal freewheeling diode of the first controllable element Q1 (which can be a switching transistor) and is connected to the neutral wire N to form a charging circuit. When the voltage across the energy storage capacitor C1 reaches the preset value of the program, the controller 15 (c) starts to control the normally open contact of the first switch device Z1 to close to prepare for discharge. Then the controller 15 (c) monitors U through the shaping filter 14 (a). pen Is it zero? pen When the voltage is zero, the controller 15 (c) controls the first controllable element Q1 to conduct, and the voltage stored on the energy storage capacitor C1 passes from point B through the third resistor R3, the first controllable element Q1, the equivalent resistor RZ, and the first switch device Z1 to point A, forming a discharge loop. Since the resistance value of the discharge loop is fixed, the change of the measured zero line N and ground line PE loop resistance will directly affect the discharge current of the energy storage capacitor C1. The smaller the equivalent resistance RZ, the greater the discharge current of the energy storage capacitor C1, and 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, it can calculate the equivalent resistance value of the measured circuit. When the measurement is completed, the controller 15 (c) can display the specific value through the display circuit 16, and can also send the value to the remote server through the communication circuit, so as to achieve online real-time monitoring, thereby reducing the occurrence of safety accidents.

[0118] The display module 16 can be a liquid crystal display or a digital tube display; the communication module 17 can realize wired or wireless transmission, such as Bluetooth, WIFI, etc., or serial port transmission. The early warning module 18 can send an alarm message to give an alarm prompt, or it can install a buzzer to give an alarm prompt through an alarm sound, so as to remind the user to prevent the occurrence of electric shock accidents caused by the failure of the protection ground wire of the power distribution system.

[0119] 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 online when the alternating current passes through zero. In addition, this embodiment will not cause dangerous voltage on the protective ground line of the distribution system during the monitoring process, nor will it trigger residual current to cause the circuit breaker to malfunction. If the resistance value of the protective ground line is abnormal, the early warning module 18 in this embodiment will issue an early warning to remind the user to prevent electric shock accidents caused by failure of the protective ground line of the distribution system.

[0120] 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 a negative polarity DC pulsating voltage U is obtained between point F and the neutral line N. F , the voltage passes through the normally closed contact of the first switch device Z1 to point A and charges the energy storage capacitor C1. At this time, point B where the energy storage capacitor C1 is connected to the third resistor R1 is a positive 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 a forward cut-off state and reversely conductive through the internal freewheeling diode) and the neutral line N to form a charging circuit. After multiple cycles of charging, the voltage of the energy storage capacitor C1 is U AB ≈U F The voltage peak value of the negative half cycle.

[0121] The controller 14(c) is always measuring the voltage between point A and point B during the charging process. When the voltage reaches the program setting value (generally between 30-40 volts), the controller 14(c) controls the first switch device Z1 to be attracted through the first drive circuit 15(a), and connects the distribution line PE to point A through the normally open contact of the first switch device Z1, preparing for the discharge of the energy storage capacitor C1. After that, the controller 15(c) monitors the voltage U between the neutral line N and the ground line PE through the shaping filter 14(a). pen Whether it is zero, when U PEN=0, the controller 15(c) controls the first controllable element Q1 to conduct through the second drive circuit 15(b). At this time, the current on the energy storage capacitor C1 starts from point B, passes through the third resistor R1, the energy storage capacitor Q1, the neutral line N and the ground line PE and the neutral line-ground line loop equivalent resistance RZ, and then passes through point C, the normally open contact of the first switch device Z1, and returns to the negative electrode A of the energy storage capacitor C1 to form a discharge loop. Since in the discharge loop of the energy storage capacitor C1, the resistance values ​​of the third resistor R1 and the first controllable element Q1 are both fixed values, it can be known that the size of the equivalent resistance RZ of the measured neutral line N and ground line PE loop determines the size of the instantaneous discharge current of the energy storage capacitor C1. The smaller the equivalent resistance RZ, the greater the instantaneous discharge current of the energy storage capacitor C1, and the higher the voltage generated on the third resistor R3. Therefore, according to Ohm's law:

[0122] U A =U C =I*RZ;

[0123] U B =I*(R3+R Q1 );

[0124] Eliminate I from the two formulas above and combine them to get: A / RZ=U B / (R3+R Q1 );

[0125] It is deduced that RZ=U A / U B *(R3+R Q1 );

[0126] 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 line 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 line N and the ground line PE loop through the display module 16, and can also send it to the network server through the communication module 17. When the controller 15 (c) can detect that the equivalent resistance of the neutral line N and the ground line PE loop exceeds the program setting 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 charging and discharging through a 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 discharge process of the energy storage capacitor C1, the size of 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 in the discharge loop of the energy storage capacitor C1 directly converts the discharge current of the energy storage capacitor C1 into a voltage signal and transmits it to the controller 15 (c) for analysis. A first controllable element Q1 is arranged between the energy storage capacitor C1 and the discharge circuit of the neutral line N. When the energy storage capacitor C1 is charged, the first controllable element Q1 is subjected to a negative voltage and its internal freewheeling diode is turned on to provide a path for the charging current of the energy storage capacitor C1; when the energy storage capacitor C1 is discharged, the relay Z3 connects the negative polarity end of the energy storage capacitor C1 with the ground line PE. At this time, the first controllable element Q1 is subjected to a positive voltage and is cut off. When the controller 15(c) Q1 is turned on, the current of the energy storage capacitor C1 passes through the first controllable element Q1 and the ground line PE to form a discharge circuit.

[0127] In addition, voltage dividing resistors R1, R2 and a rectifier diode D1 are provided between the live wire L and the neutral wire N. The voltage U L-N After voltage division by R3 and R4 and rectification by the rectifying element D1, a DC pulsating low voltage is obtained, and the voltage drop is used to charge the energy storage capacitor C1 through the first switching device Z1. A zero-crossing signal shaping filter 14 (a) is provided between the neutral line N and the ground line PE, and cooperates with the controller 15 (c) to complete the zero-crossing detection, so that the controller 15 (c) can trigger the energy storage capacitor C1 to discharge when the AC voltage passes through zero, and measure the equivalent resistance of the neutral line and the ground line loop.

[0128] By detecting the equivalent resistance in real time, it is possible to prevent the failure of leakage protection caused by the change of grounding resistance, ensure the personal safety of electricity users, and ensure the measurement accuracy.

[0129] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A zero-to-ground resistance monitoring device, characterized in that: include: Energy storage components; A charging circuit, connected to the energy storage element and the neutral line and the live line of the power supply system respectively, for forming a loop for charging the energy storage element using the power supply system; A discharge circuit, connected to the energy storage element and the neutral line and the ground line of the power supply system respectively, for forming a loop 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 circuit when the energy storage element is discharged; A shaping filter circuit is connected to the control circuit and the neutral line, live line and ground line of the power supply system respectively; it is used to filter out interference noise of the power supply system so that the control circuit can determine the zero-crossing moment of the power supply system; A control circuit, connected to the shaping filter circuit, the sampling circuit, the charging circuit, the discharging circuit and the energy storage element respectively; Used to control the charging circuit and the discharging circuit to switch between charging and discharging at the zero-crossing moment, collect the voltage across the energy storage element during the discharge process and the voltage drop of the sampling circuit when the energy storage element is discharged, and calculate the discharge current based on the voltage drop, and calculate the equivalent resistance value between the neutral line and the ground line based on the voltage across the energy storage element and the discharge current.

2. The device according to claim 1, characterized in that The charging circuit comprises: A voltage dividing and rectifying circuit is connected to the neutral line, the live line and the first switch device respectively; The first end of the first switch device is connected to the output end of the voltage divider rectifier circuit, the second end of the first switch device is connected to the first end of the energy storage element, and the third end and the fourth end of the first switch device are connected to the control circuit; Wherein, the voltage dividing and rectifying circuit further includes: A first resistor, wherein a first end of the first resistor is connected to the live wire, a second end of the first resistor is connected to a first end of a rectifier device, a second end of the rectifier device is connected to a first end of a second resistor and a first end of the first switch device, and a second end of the second resistor is connected to a neutral wire.

3. The device according to claim 2, characterized in that The discharge circuit comprises: A first controllable element, wherein a first end of the first controllable element is connected to the sampling circuit, a second end of the first controllable element is connected to the neutral line, and a third end of the first controllable element is connected to the control circuit.

4. The device according to claim 3, characterized in that The sampling circuit comprises: A third resistor, wherein a first end of the third resistor is connected to the second end of the energy storage element, and a second end of the third resistor is connected to the discharge circuit.

5. The device according to claim 1, characterized in that 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 and the neutral wire, and the third end of the shaping filter circuit is connected to the ground wire.

6. The device according to claim 3, characterized in that The control circuit comprises: A controller, wherein the controller is respectively connected to the energy storage element, the sampling circuit, the shaping filter circuit, the first drive circuit and the second drive circuit; The first end of the first driving circuit is connected to the controller, and the second end and the third end of the first driving circuit are connected to the third end and the fourth end of the first switching device respectively; A first end of the second driving circuit is connected to the controller, and a second end of the second driving circuit is connected to a third end of the first controllable element.

7. The device according to claim 6, characterized in that The control circuit further comprises: a third driving circuit, wherein a first terminal of the third driving circuit is connected to the controller, and a second terminal and a third terminal of the third driving circuit are connected to a third terminal and a fourth terminal of the second switching device, respectively; A first end of the second switch device is connected to the ground line, and a second end of the second switch device is connected to the first end of the energy storage element; 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.

8. The device according to claim 7, characterized in that include: The controller is connected to the first drive circuit, and the first drive circuit is connected to the first switch device; Used to switch the charging circuit and the discharging circuit to realize charging and discharging of the energy storage element.

9. The device according to claim 1, characterized in that Also includes: A display module, connected to the control circuit, and used to display the equivalent resistance value; A communication module, connected to the control circuit, for realizing wireless and / or wired data transmission; The early warning module is connected to the control circuit and is used to issue an alarm when the change of the equivalent resistance value reaches a preset threshold.

10. A method for monitoring zero-to-ground resistance, characterized in that: For the zero-to-ground resistance monitoring device according to any one of claims 1 to 9, 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, the energy storage element is controlled to change from a charging state to a discharging state, and it is determined whether the voltage value between the neutral line and the ground line is zero; When the voltage value between the neutral line and the ground line is zero, controlling the discharge circuit to be turned on to discharge the energy storage element; Detecting the voltage across the energy storage element during the discharge process and calculating the current of the discharge circuit; The equivalent resistance value between the neutral line and the ground line is calculated according to the voltage across the energy storage element and the discharge loop current.

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