Ground fault device end-of-life self-test system

Abstract

Disclosed in the present invention is a ground fault device end-of-life self-test system. An induction coil and a neutral coil are used for sensing and acquiring a ground fault leakage current signal of a live wire or a neutral wire. A trip device is used for cutting off the power supply to a load in the event of a ground fault by driving a solenoid by means of a thyristor which is triggered by an IC1 to turn on. A manual test button is used for manually testing the function of a ground fault device. A rectifying circuit is used for rectifying an alternating current (AC) and outputting same to a direct current, and providing the direct current to IC1 and IC2 direct current power supplies. A ground fault detection circuit is used for completing ground fault detection, and controlling the drive to trigger the thyristor to turn on or off. A ground fault self-test control circuit is used for controlling the testing of a ground fault detection function without affecting normal ground fault detection and protection functions.

Description

Ground Fault Device End of Life Self-Detection System Technical Field

[0001] The present invention relates to a life-end self-detection system for a grounding fault device, and in particular to a grounding fault device with a life-end self-intelligent detection function and a method thereof. Background Art

[0002] The rapid economic development and advancement of electronic technology have greatly promoted the widespread application and popularization of intelligent electronic and electrical equipment. As electrical equipment gradually becomes more intelligent, integrated, large-scale and complex, electricity demand is increasing day by day, and power grid facilities and their loads are becoming more and more complex. There are a large number of complex non-traditional sinusoidal residual currents and various complex harmonics. Therefore, traditional conventional AC residual current operated circuit breakers are unable to fully detect and identify various leakage conditions, which can easily cause property losses and personal injury accidents.

[0003] Faced with an increasingly complex power environment and evolving demands for safe electricity use, leakage protection devices (LRDs), as key low-voltage electrical protection components directly linked to the safety of electricity, electrical equipment, and human life and property, have been widely promoted and applied. However, with the rapid advancement of modernization in industry, agriculture, national defense, science and technology, existing leakage protection technologies and standards are gradually failing to meet social development and market demands. In AC power supply systems, ground fault protection devices (GFPDs), essential components, play a crucial role in protecting life and property. Therefore, ensuring the proper functioning of GFPDs is crucial. Furthermore, traditional technical standards recommend monthly manual testing of GFPDs for proper operation. However, in practice, users often fail to perform these regular manual tests. Manual testing requires physically triggering the trip device to disconnect the load, disrupting normal production and daily life. Consequently, in most cases, GFPDs remain untested for extended periods, posing significant safety risks.

[0004] Patent publication number CN106932711A, "Self-Testing Ground Fault Circuit Breaker and Bidirectional Ground Fault Simulation Method," describes the principles and methods for implementing ground fault leakage detection and ground fault self-testing. Because this solution utilizes a simulated ground fault circuit to generate simulated leakage currents in both positive and negative directions during the negative half-cycle of the AC phase line to simulate a ground fault, completing the simulated ground fault detection requires at least two consecutive AC cycles (40ms). Since the maximum tripping time of a non-delayed ground fault circuit breaker at five times the rated operating current is generally 40ms according to existing residual current operated devices (RCD) standards, when an actual leakage event and self-test occur simultaneously, there is no guarantee that the ground fault circuit breaker will detect and trip within the required timeframe or accurately complete the self-test process, posing a safety risk. Furthermore, this neutral-to-ground leakage detection method utilizes the commonly used feedback mechanism, typically a bipolar transistor operational amplifier, to form a positive feedback loop between the induction coil and the neutral coil. Due to the imbalance of the operational amplifier circuit and its poor anti-interference performance, this method cannot accurately detect the positive and negative half-cycle leakage current of AC grounding faults and unidirectional A-type pulsating DC and DC leakage. It may even produce large detection errors, affect detection judgment, and pose a safety hazard.

[0005] Summary of the Invention

[0006] The purpose of the present invention is to solve the problems in the above-mentioned prior art and ground fault protection devices that the live wire or neutral wire cannot accurately detect the ground and that the online self-detection may affect the normal ground fault detection and protection functions, and to provide an active excitation ground fault device end-of-life self-detection system.

[0007] The present invention discloses a ground fault device life end self-detection system, comprising: an induction coil, a neutral coil, a trip device, a rectifier circuit, a periodic signal drive circuit, a ground fault simulation leakage circuit, a ground fault detection circuit, and a ground fault self-detection control circuit;

[0008] The rectifier circuit is used to rectify AC power and output it into a DC power supply, and to power the ground fault detection circuit and the ground fault self-detection control circuit; the induction coil and the neutral coil are used to sense and obtain the leakage current signal of the live wire or neutral wire ground fault; the periodic signal drive circuit is used to make the ground fault detection circuit output a periodic signal, so that the neutral coil periodically generates current; when a ground fault occurs between the neutral wire and the ground, an induction feedback loop is formed between the neutral wire, the induction coil, and the neutral coil;

[0009] The signal input terminal of the ground fault detection circuit inputs the ground fault leakage current signal, and the signal output terminal is used to output a control signal to drive the release device to cut off the power supply to the load when a ground fault occurs;

[0010] The ground fault self-detection control circuit detects the phase voltage at the output end of the trip device during the self-detection period and compares it with the reference clock signal:

[0011] 1) If the phase voltage value is normal in the positive half cycle, go to step 2; if the phase voltage value is abnormal in the positive half cycle, it is judged that the self-test fails;

[0012] 2) After the phase voltage enters the negative half cycle, the ground fault self-detection control circuit drives the ground fault simulation leakage circuit to generate a simulated ground fault leakage signal. If the phase voltage at the output end of the trip device drops, it is determined that the ground fault detection circuit is normal.

[0013] In a preferred embodiment, when a ground fault occurs, the ground fault detection circuit outputs a control signal to control the thyristor SCR1 to conduct, so as to trip the release device and disconnect the load from power supply.

[0014] In a preferred embodiment: the ground fault detection circuit is IC1: IN+ and IN- of IC1 are connected to capacitors C2, C1, and C3 respectively, and IN+ and IN- are also connected to one end of resistors R4 and R3;

[0015] The other end of the resistor R3 is connected to the anode of the diode D1 and the cathode of D2 respectively, and the other end of the resistor R4 is connected to the cathode of the diode D1 and the anode of D2 respectively; the diodes D1, D2, and the resistor R2 are connected in parallel with the secondary of the induction coil.

[0016] In a preferred embodiment: the ground fault self-detection control circuit is IC2; the PHASE port of IC2 is used to detect the phase voltage; the FT port outputs a drive signal and forms a ground fault simulation leakage circuit with R8, R9 and Q1 to generate a ground fault simulation leakage signal;

[0017] The MS port of IC1 is connected to the FT port of IC2; the MS port is used to select or control the mode of IC1. When the MS port is at a low level, IC1 is in a ground fault detection and protection mode; when the MS port is at a high level, IC1 is in a self-detection mode.

[0018] In a preferred embodiment, the PULSE port of IC1 is connected to the resistor R10; the DRVOUT port of IC2 is connected to the trigger port of the thyristor SCR1, and DRVOUT is also connected to one end of the capacitor C5, and the other end of the capacitor C5 is grounded; the anode end of the thyristor SCR1 is connected to the cathode end of the diode D8, and the cathode end of the thyristor SCR1 is grounded;

[0019] The TRC port of IC1 is connected to one end of capacitor C7, and the other end of capacitor C7 is grounded; the OUT port of IC1 is connected to one end of capacitor C8, and the other end of capacitor C8 is grounded; the VDD terminal of IC1 is connected to capacitors C4 and R5, and the other end of C4 is grounded. Resistor R5 is also connected to the output end of the rectifier circuit.

[0020] In a preferred embodiment: the SCRT port of IC2 is connected to the diode D7 and R6, and the other ends of D7 and R6 are connected to the anode of the thyristor SCR1; the VDD terminal of IC2 is connected to the VDD port of IC1; the FT port of IC2 is connected to one end of the resistor R8; the PHASE port of IC2 is connected to one end of the resistor R7, and the other end of R7 is connected to the Load Hot.

[0021] In a preferred embodiment, one end of the solenoid of the trip device is connected to the anode of diode D8, and the cathode of D8 is connected to the cathode of diode D7; the Load Hot and Load Neutral terminals of the power supply and load terminals are connected to both ends of the trip device switch.

[0022] In a preferred embodiment, the rectifier circuit 300 includes diodes D3, D4, D5, and D6; wherein the anodes of D3 and D5 are grounded, the cathodes of D3 and the anode of D4 are connected to Load Hot, the cathodes of D4 and D6 are connected to one end of R5, and the cathode of D5 and the anode of D6 are connected to Load Neutral.

[0023] In a preferred embodiment, the periodic signal driving circuit includes resistors R10, R11, a switch Q2, and a capacitor C6, wherein one end of R11 is connected to VDD of IC1, the other end of resistor R11 is connected to the collector of switch Q2, the base of switch Q2 is connected to one end of R10, the other end of resistor R10 is connected to the PULSE port of IC1, the emitter of switch Q2 is connected to one end of capacitor C6, the emitter of switch Q2 is also connected to one end of the secondary of the neutral coil, and the other end of the neutral coil and C6 are grounded.

[0024] The PULSE port generates a periodic signal, the resistors R10 and R11 limit the output current, the switch tube Q2 amplifies the collector current and periodically charges and discharges the capacitor C6.

[0025] In a preferred embodiment, a manual test button is also included, which includes a current limiting resistor R1 and a test switch RESET. One end of the resistor R1 is connected to the test switch RESET, the other end of the resistor R1 is connected to Load Neutral, and the other end of the test switch RESET is connected to Load Hot.

[0026] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0027] The present invention discloses a self-detection system for the end of life of a ground fault device. Compared with the existing technology and ground fault protection devices, the system solves the problem of being unable to accurately detect the relationship between the live wire or the neutral wire and the ground and the problem that the normal ground fault detection and protection functions may be affected during online self-detection. An active excitation-type self-detection system for the end of life of a ground fault device is provided, which solves the problems of imbalance, low precision, poor consistency and poor anti-interference existing in the existing technology and ground fault protection devices using operational amplifiers. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG1 is a circuit diagram of a ground fault device end-of-life self-detection system according to the present invention;

[0029] FIG2 is a schematic diagram of a neutral grounding fault circuit according to the present invention. DETAILED DESCRIPTION

[0030] The technical solutions 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; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships depicted in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0032] In the description of the present invention, it should be noted that, unless otherwise clearly stipulated and limited, the terms "installed", "provided with", "set / connected", "connected", etc. should be understood in a broad sense. For example, "connection" can be a wall-mounted connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be a direct connection or an indirect connection through an intermediate medium. It can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] 1-2 , this embodiment provides a ground fault device end-of-life self-detection system, as shown in FIG1 , including: an induction coil coil 1, a neutral coil coil 2, a thyristor SCR 1, a trip device 100, a manual test button 200, a rectifier circuit 300, a periodic signal drive circuit 400, a ground fault simulation leakage circuit 500, a ground fault detection circuit IC1, and a ground fault self-detection control circuit IC2.

[0034] The ground fault detection circuit IC1 includes: IN+ and IN- of IC1 are connected to C2, C1, and C3 respectively, IN+ and IN- are also connected to R4 and R3, the other ends of R3 and R4 are connected to the two ends of D1 and D2 respectively, and D1, D2, and R2 are connected in parallel with the secondary of the induction coil; the MS port of IC1 is connected to the FT port of IC2; the PULSE port of IC1 is connected to R10; the DRVOUT port of IC2 is connected to the trigger port of SCR1, DRVOUT is also connected to one end of C5, and the other end of C5 is grounded; the anode terminal of SCR1 is connected to the cathode of D8, and the cathode of SCR1 is grounded; the TRC port of IC1 is connected to one end of C7, and the other end of C7 is grounded; the OUT port of IC1 is connected to one end of C8, and the other end of C8 is grounded; the VDD terminal of IC1 is connected to C4 and R5, the other end of C4 is grounded, and R5 is also connected to the output terminal of the rectifier circuit.

[0035] The ground fault self-detection control circuit IC2 includes: the SCRT port of IC2 is connected to D7 and R6, and the other ends of D7 and R6 are connected to the anode of SCR1; the VDD terminal of IC2 is connected to the VDD port of IC1; the FT port of IC2 is connected to one end of R8; the DRV port of IC2 is connected to the anode of LED, and the cathode of LED is grounded; the PHASE port of IC2 is connected to one end of R7, and the other end of R7 is connected to Load Hot.

[0036] One end of the solenoid of the trip device 100 is connected to D8, and the other end is connected to Load Hot. The trip device 100 is also connected to Load Hot and Load Neutral at the power supply end and the load end respectively at both ends of the trip mechanism.

[0037] The manual test button 200 includes a current limiting resistor R1 and a test switch RESET, wherein R1 is connected to RESET, the other end of R1 is connected to Load Neutral, and the other end of RESET is connected to Load Hot.

[0038] The rectifier circuit 300 includes four diodes: D3, D4, D5, and D6. The anodes of D3 and D5 are grounded, the cathodes of D3 and D4 are connected to Load Hot, the cathodes of D4 and D6 are connected to one end of R5, and the cathode of D5 and D6 are connected to Load Neutral.

[0039] The periodic signal driving circuit 400 includes: resistors R10, R11, a switch tube Q2 and a capacitor C6, wherein one end of R11 is connected to VDD, the other end of R11 is connected to the collector of Q2, the base of Q2 is connected to one end of R10, the other end of R10 is connected to the PULSE port of IC1, the emitter of Q2 is connected to one end of C6, the emitter of Q2 is also connected to one end of the secondary of the neutral coil, and the other end of the neutral coil and C6 are grounded.

[0040] In the ground fault detection circuit IC1, the MS port is used to select or control the ground fault detection circuit IC1 to switch to different modes: when the MS port is low, IC1 is in normal ground fault detection and protection mode; when the MS port is high, IC1 is in self-detection mode.

[0041] After the above settings, the secondary induced current of induction coil 1 is converted into a voltage difference through R1. D1 and D2 are connected in parallel at both ends of R2 in reverse order, limiting the voltage below 1V. R3, R4 and C1, C2, and C3 form a filtering circuit. The differential voltage value obtained by converting the induced ground fault current is then sent to the IN+ and IN- ports and processed internally by IC1.

[0042] The PULSE port of the ground fault detection circuit IC1 generates a periodic signal. R10 and R11 limit the output current, while Q2 amplifies the collector current and periodically charges and discharges C6, causing a periodic current to flow through the neutral coil secondary. When a neutral-to-ground ground fault occurs, an inductive feedback loop is formed between the neutral line (Load Neutral), inductive coil 1, and neutral coil 2. When the detected ground fault current exceeds the set threshold, the DRVOUT port outputs a drive signal, triggering SCR1 to conduct, causing the trip device to trip and disconnect the load power supply.

[0043] The PHASE port of the ground fault self-detection control circuit IC2 detects phase voltages. The FT port outputs a drive signal and, together with R8, R9, and Q1, forms an amplifier circuit to generate a simulated ground fault leakage signal. The SCRT port, through D7 and R6, detects the connectivity between SCR1 and trip device 100 and the functionality of SCR1. The DRV port issues an alarm signal if the self-detection fails, driving an LED or other alarm device.

[0044] The above-mentioned ground fault device end-of-life self-detection system, after power-on and normal operation, detects the phase line periodic waveform at the PHASE terminal and simultaneously starts timing the internal timer. If a normal phase line periodic waveform signal cannot be detected within a predetermined time period, the system is determined to be faulty, enabling the DRV to output an alarm signal, driving an external LED to flash and issue an alarm message. It can also drive other devices such as speakers, buzzers, and photoelectric conversion devices, which are simple replacements for this embodiment.

[0045] When the system is powered on and operating normally, if the PHASE terminal detects a normal phase line cycle signal within a certain time period, the internal timing will be stopped, and the phase line cycle waveform signal will be used as the internal reference cycle clock signal; after the determined self-detection test cycle starts, the SCRT first detects whether its voltage value in the positive half cycle of the phase voltage is normal. If the SCRT voltage is normal, the next detection content will be entered. If the SCRT voltage is detected to be abnormal in the positive half cycle of the phase voltage, it will be directly determined that the self-detection has failed, and the control circuit drives the DRV to output an alarm signal, and the self-detection cycle ends.

[0046] The next detection content specifically refers to: during the self-test cycle, when the phase voltage enters the negative half cycle, FT drives the output signal to IC1, enabling it to enter the self-test mode. At the same time, since D8 is turned off during the negative half cycle of the phase voltage, the SCRT provides a sufficiently high voltage to the anode end of SCR1 through D7. At the same time, FT also drives the simulated ground fault leakage amplifier circuit composed of Q1 and R9 connected to R8 to generate a simulated ground fault leakage signal:

[0047] If IC1 is working normally, the signal sensed by the induction line coil ciol1 or coil coil2 is processed and judged internally, and the DRVOUT terminal outputs a driving signal, triggering the SCR1 thyristor to turn on. The SCRT terminal voltage drops and is monitored by the internal detection circuit, proving that the ground fault detection circuit is functioning normally. The self-test process ends and waits for the next self-test cycle to start.

[0048] In the end-of-life self-detection system for the ground fault device, IC2 is in a non-operating state during a non-self-detection cycle. If a live wire-to-ground leakage ground fault occurs, the induction coil coil 1 detects the ground fault signal, which is converted and filtered before entering IC1. IC1 processes and amplifies the ground fault signal and determines whether it is greater than a preset threshold. If so, the ground fault signal is considered valid, and DRVOUT is driven to trigger the thyristor SCR1 to conduct. Since the trigger signal cycle is greater than one AC signal cycle, the trip device can be ensured to trip within the positive half cycle, promptly cutting off the load power supply and achieving the protection purpose.

[0049] During the non-self-test period, if the ground fault signal is less than the set threshold, the signal is deemed invalid, DRVOUT remains low, and SCR1 and the trip unit remain inactive. If a neutral-to-ground leakage ground fault occurs, the neutral line creates a feedback loop between induction coil 1 and neutral coil 2, as shown in Figure 2. As the ground fault current signal enters IC1, the continuously cyclic PULSE excitation signal causes the amplified signal from Q2 to be fed back through the neutral line to induction coil 1. This signal then acts as the primary signal of induction coil 1 and is then fed to its secondary. This repeated feedback loop oscillates. When the ground fault current exceeds the set threshold, IC1 ultimately determines it as a valid neutral ground fault signal. The DRVOUT output triggers SCR1 and the trip unit circuit to conduct, shutting off power to the load and providing protection.

[0050] The above is only a preferred specific embodiment of the present invention, but the design concept of the present invention is not limited to this. Any technician familiar with this technical field who uses this concept to make non-substantial changes to the present invention within the technical scope disclosed by the present invention shall be deemed to infringe the scope of protection of the present invention. Industrial Applicability

[0051] The present invention discloses a ground fault device end-of-life self-detection system. Compared with existing technologies and ground fault protection devices, this system solves the problems of being unable to accurately detect the live or neutral line to ground and the potential impact of online self-detection on normal ground fault detection and protection functions. This system provides an active excitation ground fault device end-of-life self-detection system, resolving the problems of offset, low precision, poor consistency, and poor anti-interference performance that exist in existing technologies and ground fault protection devices using operational amplifiers. The system has excellent industrial applicability.

Claims

1. A self-detection system for the end-of-life of a ground fault device, characterized in that Including: Induction coil, neutral coil, tripping device, rectifier circuit, periodic signal drive circuit, ground fault simulation leakage circuit, ground fault detection circuit, ground fault self-detection control circuit; The rectifier circuit is used to rectify and output AC alternating current into a DC power supply, and supply power to the ground fault detection circuit and the ground fault self-detection control circuit; the induction coil and the neutral coil are used to inductively obtain the ground fault leakage current signal of the live wire or the neutral wire; the periodic signal drive circuit is used to make the ground fault detection circuit output a periodic signal, so that the neutral coil generates current periodically; When a ground fault occurs between the neutral wire and the ground, an inductive feedback loop is formed among the neutral wire, the induction coil, and the neutral coil; The signal input end of the ground fault detection circuit inputs the ground fault leakage current signal, and the signal output end is used to output a control signal to drive the tripping device to cut off the load power supply when a ground fault occurs; The ground fault self-detection control circuit detects the phase voltage at the output end of the tripping device within the self-test period and compares it with the reference clock signal: 1) If the voltage value of the phase voltage is normal in the positive half cycle, go to step 2; if the voltage value of the phase voltage is abnormal in the positive half cycle, it is judged that the self-test fails; 2) After the phase voltage enters the negative half cycle, the ground fault self-detection control circuit drives the ground fault simulation leakage circuit to generate a simulated ground fault leakage signal. If the phase voltage at the output end of the tripping device drops, it is judged that the ground fault detection circuit is normal.

2. The self-detection system for the end-of-life of a ground fault device according to claim 1, characterized in that: The ground fault detection circuit outputs a control signal to control the thyristor SCR1 to conduct when a ground fault occurs, so as to trip the tripping device and cut off the load power supply.

3. The self-detection system for the end-of-life of a ground fault device according to claim 2, characterized in that: The ground fault detection circuit is IC1: IN+ and IN- of IC1 are respectively connected to capacitors C2, C1, and C3, and IN+ and IN- are also connected to one ends of resistors R4 and R3; The other end of resistor R3 is respectively connected to the anode of diode D1 and the cathode of D2, and the other end of resistor R4 is respectively connected to the cathode of diode D1 and the anode of D2; diodes D1, D2, and resistor R2 are connected in parallel with the secondary of the induction coil.

4. The self-detection system for the end-of-life of a ground fault device according to claim 3, characterized in that: The ground fault self-detection control circuit is IC2; the PHASE port of IC2 is used to detect the phase voltage; the FT port outputs a drive signal and forms a ground fault simulation leakage circuit with R8, R9, and Q1 to generate a ground fault simulation leakage signal; The MS port of IC1 is connected to the FT port of IC2; the MS port is used to select or control the mode of IC1. When the MS port is at a low level, IC1 is in the ground fault detection and protection mode; when the MS port is at a high level, IC1 is in the self-detection mode.

5. The self-detection system for the end-of-life of a ground fault device according to claim 4, characterized in that: The PULSE port of IC1 is connected to resistor R10; the DRVOUT port of IC2 is connected to the trigger port of thyristor SCR1, and DRVOUT is also connected to one end of capacitor C5, and the other end of capacitor C5 is grounded; the anode of thyristor SCR1 is connected to the cathode of diode D8, and the cathode of thyristor SCR1 is grounded; The TRC port of IC1 is connected to one end of capacitor C7, and the other end of capacitor C7 is grounded; the OUT port of IC1 is connected to one end of capacitor C8, and the other end of capacitor C8 is grounded; the VDD terminal of IC1 is connected to capacitor C4 and resistor R5. The other end of C4 is grounded, and resistor R5 is also connected to the output terminal of the rectifier circuit.

6. The self-detection system for the end-of-life of a ground fault device according to claim 5, characterized in that: The SCRT port of the said IC2 is connected to diode D7 and resistor R6, and the other ends of D7 and R6 are connected to the anode of thyristor SCR1; the VDD terminal of IC2 is connected to the VDD port of IC1; the FT port of IC2 is connected to one end of resistor R8; the PHASE port of IC2 is connected to one end of resistor R7, and the other end of R7 is connected to Load Hot.

7. The self-detection system for the end-of-life of a ground fault device according to claim 6, characterized in that: One end of the solenoid of the said release device is connected to the anode of diode D8, and the cathode of D8 is connected to the cathode of diode D7; Load Hot and Load Neutral at the power supply end and the load end are connected to both ends of the switch of the release device.

8. The self-detection system for the end-of-life of a ground fault device according to claim 1, characterized in that: The said rectifier circuit 300 includes diodes D3, D4, D5, D6; Among them, the anodes of D3 and D5 are grounded, the cathode of D3 is connected to the anode of D4 and to Load Hot, the cathodes of D4 and D6 are connected to one end of R5, and the cathode of D5 is connected to the anode of D6 and to Load Neutral.

9. The self-detection system for the end-of-life of a ground fault device as described in claim 3, characterized in that: The said periodic signal driving circuit includes: resistors R10, R11, switching transistor Q2 and capacitor C6. One end of R11 is connected to the VDD of IC1, the other end of resistor R11 is connected to the collector of switching transistor Q2, the base of switching transistor Q2 is connected to one end of R10, the other end of resistor R10 is connected to the PULSE port of IC1, the emitter of switching transistor Q2 is connected to one end of capacitor C6, and the emitter of switching transistor Q2 is also connected to one end of the secondary of the neutral coil. The other ends of the neutral coil and C6 are grounded; The said PULSE port generates a periodic signal. Resistors R10 and R11 limit the output current, and switching transistor Q2 amplifies the collector current and periodically charges and discharges capacitor C6.

10. The self-detection system for the end-of-life of a ground fault device according to claim 1, characterized in that: It also includes a manual test button. The said manual test button includes current-limiting resistor R1 and test switch RESET. One end of resistor R1 is connected to test switch RESET, the other end of resistor R1 is connected to Load Neutral, and the other end of test switch RESET is connected to Load Hot.

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