Leakage protection device and monitoring circuit for floating AC power supply lines

Abstract

This application discloses a leakage current protection device and monitoring circuit for floating AC power supply lines, relating to the field of leakage current protection technology for floating power supply lines. The leakage current protection device includes a monitoring circuit module, a signal processing module, and a circuit breaker. The monitoring circuit module is coupled to the floating AC power supply line, the signal processing module is electrically connected to the monitoring circuit module, and the circuit breaker is electrically connected to the signal processing module. This application monitors the ground leakage current in the AC power supply line through the monitoring circuit module. When leakage occurs, the signal processing module generates a trip command to the circuit breaker, which disconnects the AC power supply line, thereby protecting the floating AC power supply line. This application achieves the technical effect of sensitively monitoring the leakage process of the floating AC power supply line and promptly disconnecting the circuit breaker based on the monitoring results to protect the power supply line.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of leakage protection of floating power supply lines, and in particular to a leakage protection device applied to a floating AC power supply line and a monitoring circuit. BACKGROUND

[0002] The floating AC power supply line refers to a power supply line without direct electrical connection with the ground or a power supply line with high impedance isolation between the entire power supply line and the ground, and is usually applied to scenarios with high requirements for electrical isolation, such as ships, mining equipment or medical equipment. However, the floating AC power supply line may still have a situation of line-to-ground insulation degradation during use, for example, due to aging or mechanical damage of the insulation layer caused by a humid environment, although a short circuit is not immediately formed, there is still a safety hazard, such as the risk of personnel contacting a live shell, therefore, the leakage protection device in the floating AC remote power supply line is still necessary.

[0003] Based on the working principle of the leakage protection device, in the floating AC remote power supply line, since there is no reference ground, the floating AC remote power supply line cannot form a loop with the ground, and the conventional residual current detection method needs to rely on the formation of a loop with the ground to detect the leakage of the power supply line, therefore, the conventional residual current detection method is not applicable to the floating power supply line, and a leakage protection and monitoring device suitable for the floating AC power supply line needs to be designed to ensure the safety of the floating long-distance power supply system in the case of insulation degradation or grounding fault, and prevent electric shock and fire.

[0004] At the same time, the impedance change and signal attenuation caused by the long-distance line will affect the reliability of the leakage protection device. SUMMARY

[0005] The leakage protection device and monitoring circuit applied to the floating AC power supply line provided by the embodiments of the present application solve the technical problems that the conventional residual current detection method in the prior art is not applicable to the leakage protection detection of the floating AC power supply line, and the sensitivity of the detection circuit and the accuracy of the digital signal processing technology are insufficient during the leakage protection detection of the floating AC power supply line, and achieve the technical effect that the leakage process of the floating AC power supply line can be sensitively monitored, and the power supply line can be cut off by the circuit breaker in time when leakage occurs, and the circuit breaker can be cut off in time based on the monitoring result to protect the power supply line.

[0006] In a first aspect, the embodiments of the present application provide a leakage protection device applied to a suspended AC power supply line, comprising a monitoring circuit module, a signal processing module and a circuit breaker; two input ends of the monitoring circuit module are respectively coupled to the AC power supply line, an output end of the monitoring circuit is connected to an input end of the signal processing module, and the monitoring circuit module is configured to collect a ground leakage current of the AC power supply line in real time and output the ground leakage current to the signal processing module; the monitoring circuit module comprises a voltage dividing unit and a power taking coil; an input end of the voltage dividing unit is coupled to the AC power supply line and is configured to perform balanced voltage division based on a voltage of the AC power supply line; an output end of the voltage dividing unit is coupled to an input end of the power taking coil; an output end of the power taking coil is connected to an input end of the signal processing module, and the power taking coil is configured to obtain the ground leakage current based on the voltage dividing unit and transmit the ground leakage current to the signal processing module; the signal processing module is configured to receive the ground leakage current, perform amplification, filtering and buffering processing on the ground leakage current, generate a trip instruction based on a current signal of the buffered ground leakage current, and output the trip instruction to the circuit breaker; an input end of the circuit breaker is connected to an output end of the signal processing module, a control end of the circuit breaker is coupled to the AC power supply line, and the circuit breaker is configured to perform on-off control on the AC power supply line based on the trip instruction.

[0007] In combination with the first aspect, in a possible implementation, the leakage protection device further comprises a power supply module; the power supply module is configured to provide a working voltage for the signal processing module; the power supply module comprises a rectifier unit and a voltage conversion unit; an input end of the rectifier unit is coupled to an external AC power supply, an output end of the rectifier unit is electrically connected to an input end of the voltage conversion unit, and the rectifier unit is configured to rectify the external AC power supply; an output end of the voltage conversion unit is electrically connected to the signal processing module, and the voltage conversion unit is configured to convert the rectified external AC power supply into a direct current power supply.

[0008] In combination with the first possible implementation of the first aspect, in a second possible implementation, the power supply module further comprises an overvoltage protection unit; the overvoltage protection unit is connected in parallel to the output end of the voltage conversion unit, and the overvoltage protection unit is configured to trigger short circuit protection when the working voltage abnormally rises.

[0009] In a third possible implementation manner of the first aspect, the signal processing module comprises a signal amplification unit, a signal buffering unit and an optocoupler isolation unit; an input end of the signal amplification unit is electrically connected to the monitoring circuit module; an output end of the signal amplification unit is electrically connected to an input end of the signal buffering unit; an output end of the signal buffering unit is electrically connected to an input end of the optocoupler isolation unit; an output end of the optocoupler isolation unit is electrically connected to the circuit breaker; the signal amplification unit is configured to amplify the ground leakage current; the signal buffering unit is configured to filter and buffer the amplified ground leakage current; the optocoupler isolation unit is configured to output a tripping instruction based on the filtered and buffered ground leakage current.

[0010] In a fourth possible implementation manner of the first aspect, the energy taking coil obtains the ground leakage current through electromagnetic induction and / or capacitive coupling.

[0011] In a second aspect, an embodiment of the present application provides a monitoring circuit applied to a floating AC power supply line, the monitoring circuit comprising the monitoring circuit module in the first aspect and any one of the first aspect, the monitoring circuit comprising a common mode filter circuit, a cement resistance voltage dividing circuit and an energy taking coil circuit; an input end of the common mode filter circuit is coupled to a high voltage phase line of the AC power supply line; an output end of the common mode filter circuit is electrically connected to an input end of the cement resistance voltage dividing circuit; an output end of the cement resistance voltage dividing circuit is grounded; an input end of the energy taking coil circuit is coupled between an output end of the cement resistance voltage dividing circuit and the ground; an output end of the energy taking coil is electrically connected to a signal processing module; the common mode filter circuit is configured to filter out harmonic pulses of a current in the AC power supply line; the cement resistance voltage dividing circuit is configured to balance voltage division of the current in the AC power supply line based on a cement resistance; and the energy taking coil circuit is configured to obtain the ground leakage current between the AC power supply line and the ground.

[0012] In a possible implementation manner of the second aspect, the common mode filter circuit comprises a transformer U7, a transformer U8, a capacitor C15, a capacitor C16 and a capacitor C17; two input ends of the transformer U7 are coupled to two high voltage phase lines of the AC power supply line respectively; two output ends of the transformer U7 are electrically connected to two input ends of the transformer U8 respectively; two output ends of the transformer U8 are electrically connected to the cement resistance voltage dividing circuit; the capacitor C15 is connected in parallel with the two output ends of the transformer U7; the capacitor C16 and the capacitor C17 are connected in series and then connected in parallel with the two output ends of the transformer U8.

[0013] In a second possible implementation manner, the cement resistance voltage dividing circuit comprises a resistance R22 and a resistance R23; one end of the resistance R22 and one end of the resistance R23 are electrically connected to the common mode filter circuit, and the other end of the resistance R22 and the other end of the resistance R23 are grounded; the resistance R22 and the resistance R23 have equal resistance values.

[0014] In a third possible implementation manner, the power taking coil circuit obtains the ground leakage current between the cement resistance voltage dividing circuit and the ground through electromagnetic induction and / or capacitive coupling.

[0015] The one or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0016] In the embodiments of the present application, the input end of the monitoring circuit module is coupled to two high-voltage phase lines of the suspended AC power supply line, and the high-voltage is voltage-divided based on the voltage dividing unit, so that the voltage between the voltage dividing unit and the ground reaches a balanced state, and the current tends to be 0. When the AC power supply line leaks, the voltage balance state is broken, and the current increases to a maximum of 5 mA. The signal processing module processes the ground leakage current in the leakage state and generates a trip instruction, and the circuit breaker controls the air switch of the AC power supply line to trip based on the trip instruction. The technical means is realized. The technical effect of being able to sensitively monitor the leakage process of the suspended AC power supply line and timely cut off the circuit breaker to protect the power supply line. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments of the present application or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0018] Figure 1 is the frame diagram of the suspended AC power supply line leakage protection device provided by the embodiments of the present application;

[0019] Figure 2 is the frame diagram of the power supply module provided by the embodiments of the present application;

[0020] Figure 3 is the frame diagram of the signal processing module provided by the embodiments of the present application;

[0021] Figure 4 is the circuit diagram of the monitoring circuit provided by the embodiments of the present application. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort fall within the protection scope of the present application.

[0023] Unlike traditional power supply lines, the floating AC power supply line does not have a zero line or a neutral line in the traditional sense. There are only two high-voltage phase lines, one of which is connected to a fuse, and the other is connected to a high-voltage lightning protection line. The alternating voltage between the two high-voltage phase lines reaches 600V~1500V, and the current only flows between the two high-voltage phase lines and does not return through the ground. At the same time, the floating AC remote power supply line can also use a three-phase line. When a three-phase line is used, each phase is still floating relative to the ground, and there is no neutral line, and the load works through the phase-to-ground voltage.

[0024] The neutral point of the AC power supply line is not directly grounded or the entire AC power supply line is isolated from the ground with high impedance. In the floating AC power supply line, there is no direct electrical connection point between the line and the ground as a reference point for leakage, and the floating AC power supply line cannot form a loop with the ground. Therefore, the present application provides a leakage protection device and a monitoring circuit capable of realizing leakage monitoring and leakage protection based on the floating AC power supply line (firewire and zero line) to improve the power supply continuity and safety of the floating AC power supply line.

[0025] Figure 1 is a block diagram of the leakage protection device of the floating AC power supply line provided by the present application. As shown in Figure 1 The leakage protection device described in the present application comprises a monitoring circuit module, a signal processing module and a circuit breaker.

[0026] The two input ends of the monitoring circuit module are respectively coupled with the two high-voltage phase lines of the floating AC power supply line. The monitoring circuit module is used to collect the ground leakage current between the AC power supply lines in real time. When the AC power supply line leaks, the current and voltage between the two high-voltage phase lines change relatively, a loop is formed between the high-voltage phase line and the ground, and a ground leakage current is generated. The monitoring circuit module can monitor the ground leakage current in real time. At the same time, the monitoring circuit module is also used to transmit the ground leakage current between the two high-voltage phase lines to the signal processing module.

[0027] In the embodiment of the present application, the monitoring circuit module includes a voltage dividing unit and a power taking coil. The voltage dividing unit is electrically connected with the AC power supply line and is used to balance the voltage in the AC power supply line so that the voltage between the two high-voltage phase lines is in a balanced state. When the balanced state of the voltage is broken, it proves that the AC power supply line has a ground leakage, and a ground leakage current is generated. The power taking coil obtains the ground leakage current based on the electromagnetic induction phenomenon when the balanced state of the voltage is broken, and transmits the ground leakage current to the signal processing module.

[0028] The input end of the signal processing module is connected with the output end of the monitoring circuit module. The signal processing module is used to receive the ground leakage current output by the monitoring circuit module and process the ground leakage current generated by the two high-voltage phase lines. Specifically, the processing process includes amplification, filtering and buffering of the ground leakage current. And a trip instruction is generated based on the current signal of the processed ground leakage current.

[0029] The input end of the circuit breaker is connected with the output end of the signal processing module. At the same time, the control end (i.e. the output end) of the circuit breaker is coupled with the air switch on the two high-voltage phase lines of the AC power supply line. The circuit breaker is used to disconnect the air switch based on the trip instruction output by the signal processing module, thereby realizing the on-off control of the AC power supply line.

[0030] The embodiment of the present application adopts the technical means that the input end of the monitoring circuit module is coupled with the two high-voltage phase lines of the AC power supply line, and the voltage dividing unit divides the high-voltage voltage so that the voltage between the voltage dividing unit and the ground reaches a balanced state and the current tends to 0. When the power supply line has a leakage, the balanced state of the voltage is broken, a ground leakage current is generated, and the current value of the ground leakage current reaches 5mA at most. The signal processing module processes the ground leakage current and generates a trip instruction. The circuit breaker controls the air switch to disconnect the AC power supply line based on the trip instruction. The present application realizes the technical effect that the leakage process of the suspended AC power supply line can be sensitively monitored, and the circuit breaker is timely cut off based on the monitoring result to protect the AC power supply line.

[0031] Figure 2 The framework diagram of the power supply module provided in the embodiment of the present application is shown in FIG. 1. Figure 2 As shown in FIG. 1, in the embodiment of the present application, the suspended AC power supply line leakage protection device further includes a power supply module. The power supply module includes a rectifier unit, a voltage conversion unit and an overvoltage protection unit. The power supply module is used to provide a working voltage for the signal processing module to ensure that the signal processing module can normally operate.

[0032] Specifically, the input end of the rectifier unit is electrically connected with an external power supply (mainly 220V mains, AC), the output end of the rectifier unit is electrically connected with the input end of the voltage conversion unit, the output end of the voltage conversion unit is connected in parallel with the overvoltage protection unit, and meanwhile, the output end of the voltage conversion unit is electrically connected with the signal processing module.

[0033] The rectifier unit rectifies the input 220V AC, and the voltage conversion unit converts the rectified input voltage into AC-DC voltage. Specifically, a +5V DC working voltage is generated based on a voltage stabilizer, and a -5V DC working voltage is generated based on a voltage converter, and the +5V working voltage and the -5V working voltage together provide a working voltage for the signal processing module.

[0034] For example, in the embodiment of the present application, the voltage stabilizer can be a three-terminal voltage stabilizer with a model number of L7805CDT. The voltage converter can be a switched capacitor voltage converter with a model number of TC7660M / TR.

[0035] The overvoltage protection unit is connected in parallel to the output end of the voltage conversion unit, and is used to monitor the working voltage. When the working voltage abnormally rises, a short-circuit protection is triggered to disconnect the connection between the voltage conversion unit and the signal processing module.

[0036] In the embodiment of the present application, the power extraction coil realizes the acquisition of the ground leakage current of the two high-voltage phase lines in the AC power supply line through electromagnetic induction and / or capacitive coupling.

[0037] Figure 3 The framework diagram of the signal processing module provided in the embodiment of the present application is shown in FIG. 2. Figure 3 As shown in FIG. 2, in the embodiment of the present application, the signal processing module includes a signal amplification unit, a signal buffer unit and an optical coupling isolation unit.

[0038] Specifically, the input end of the signal amplification unit is electrically connected with the monitoring circuit module, the output end of the signal amplification unit is electrically connected with the input end of the signal buffer unit, the output end of the signal buffer unit is electrically connected with the optical coupling isolation unit, and the optical coupling isolation unit is electrically connected with the circuit breaker.

[0039] It should be noted that, in order to rectify the ground leakage current output by the signal buffer unit, a rectifier needs to be arranged between the signal buffer unit and the optical coupling isolation unit.

[0040] The signal amplification unit amplifies the ground leakage current output by the monitoring circuit module, and the signal buffering unit filters and buffers the amplified ground leakage current. After filtering and buffering, the ground leakage current is output as a photoelectric signal (equivalent to the current signal of the ground leakage current) after passing through the optocoupler isolation unit. At the same time, the signal processing module generates a trip command based on the photoelectric signal, and then controls the circuit breaker to operate based on the trip command (i.e., controls the air switch in the AC power supply line to trip).

[0041] The operating voltages of the signal amplification unit, signal buffer unit, and rectifier all come from the operating voltage output by the power supply module.

[0042] For example, in the signal amplification unit, an operational amplifier of model AD620ARZ can be selected as the main electronic component for signal amplification. For current filtering and buffering, a low-power dual operational amplifier of model LM358DR can be selected. In the optocoupler isolation unit, an optocoupler of model EL817S1 can be selected to realize the output control signal based on the filtered and buffered current.

[0043] Figure 4 A circuit diagram of the monitoring circuit provided in an embodiment of this application. (See diagram below.) Figure 4 As shown in the embodiments of this application, a monitoring circuit for a floating AC power supply line is also provided. The monitoring circuit mainly includes the monitoring circuit module described in the embodiments of this application. Specifically, the monitoring circuit includes a common-mode filter circuit, a cement resistor voltage divider circuit, and an energy harvesting coil circuit.

[0044] The input terminal of the common-mode filter circuit is connected to the two high-voltage phase lines in the AC power supply line (i.e., Figure 4 The L1 and L2 terminals of the circuit are connected together, and the output terminal is connected to the input terminal of the cement resistor voltage divider circuit. The output terminal of the cement resistor voltage divider circuit is grounded. The input terminal of the energy harvesting coil circuit is coupled between the output terminal of the cement resistor voltage divider circuit and the ground, and the output terminal of the energy harvesting coil is electrically connected to the signal processing module.

[0045] Specifically, the common-mode filter circuit is used to filter out harmonic pulses in the current of the acquired AC power supply line. The cement resistor voltage divider circuit uses the cement resistor in the circuit to achieve balanced voltage division of the filtered voltage. The energy harvesting coil is used to obtain the maximum 5mA leakage current to ground generated by the cement resistor voltage divider circuit when leakage to ground occurs in the AC power supply line.

[0046] For example, such as Figure 4 As shown, the common-mode filter circuit includes transformer U7, transformer U8, capacitor C15, capacitor C16, and capacitor C17.

[0047] Two input terminals of the transformer U7 are coupled to two high-voltage phase lines (i.e., L1 and L2) of an alternating current power supply line, respectively, and two output terminals of the transformer U7 are electrically connected to two input terminals of the transformer U8, respectively; both output terminals of the transformer U8 are electrically connected to the cement resistor voltage dividing circuit. The capacitor C15 is connected in parallel to the two output terminals of the transformer U7; the capacitor C16 and the capacitor C17 are connected in series and then connected in parallel to the two output terminals of the transformer U8.

[0048] In the cement resistor voltage dividing circuit, the resistor R22 and the resistor R23 are included. One end of the resistor R22 and one end of the resistor R23 are both electrically connected to the common mode filter circuit, and the other end of the resistor R22 and the other end of the resistor R23 are both grounded.

[0049] It should be noted that the resistances of the resistor R22 and the resistor R23 are equal, so as to ensure that the cement resistor voltage dividing circuit can achieve balanced voltage division and the current between the cement resistor voltage dividing circuit and the ground approaches 0.

[0050] In the energy-taking coil circuit, the current-type voltage transformer L2, the zero-sequence current transformer L1, the resistor R3, the resistor R4 and the resistor R5 are included.

[0051] One end of the current-type voltage transformer L2 is provided with a hole, and the hole is sleeved on a wire between the cement resistor voltage dividing circuit and the ground. The output terminal of the current-type voltage transformer L2 is electrically connected to the signal processing module.

[0052] At the same time, the zero-sequence current transformer L1 also has a ring structure, and the ring of the zero-sequence current transformer L1 is sleeved on the wire between the cement resistor voltage dividing circuit and the ground. One end of the zero-sequence current transformer L1 is connected in series with the resistor R5 and the resistor R3 and then electrically connected to the signal processing module, and the other end is connected in series with the resistor R4 and then electrically connected to the signal processing module.

[0053] Exemplarily, the model of the zero-sequence current transformer L1 can be ZCT101, and the model of the current-type voltage transformer L2 is ZHT102.

[0054] The zero-sequence current transformer L1 and the current-type voltage transformer L2 both monitor the ground leakage current between the cement resistor voltage dividing circuit and the ground through electromagnetic induction and / or capacitive coupling.

[0055] The leakage protection device provided by the embodiments of the present application is mainly used for an AC remote power supply station. The core function thereof is to monitor the vector difference of the inflow and outflow currents in the loop of the suspended AC power supply line. When the power supply line is in a normal power supply state, the current change monitored by the monitoring circuit module approaches 0, and the voltage between the two cement resistors in the voltage dividing unit is in a balanced state. When the leakage phenomenon occurs between the loops of the power supply line, the balanced state of the voltage is broken, the current produces a vector difference, and the current output by the voltage dividing unit reaches 5 mA, which is the ground leakage current. When the ground leakage current passes through the monitoring circuit module, it is transmitted to the signal processing module through the power taking coil. The signal processing module processes the ground leakage current and outputs a tripping instruction to the circuit breaker based on the processed ground leakage current. The circuit breaker controls the air switch between the lines of the power supply line to trip, thereby realizing the protection of the suspended AC power supply line with leakage.

[0056] The device or module described in the above embodiments can be implemented by a computer chip or an entity, or by a product with certain functions. For the convenience of description, the above device is described as various modules with functions. In the implementation of the embodiments of the present application, the functions of the modules can be implemented in the same or multiple software and / or hardware. Of course, the modules implementing certain functions can also be combined to implement the modules.

[0057] In addition, each functional module in each embodiment of the present application can be integrated in one processing module, or each module can exist independently, or two or more modules can be integrated in one module.

[0058] Each embodiment in the specification is described in a progressive manner, and the same or similar parts of each embodiment can be referred to each other. Each embodiment mainly describes the differences from other embodiments. The whole or part of the present application can be used in many general or special computer system environments or configurations. For example: personal computers, server computers, handheld devices or portable devices, tablet devices, mobile communication terminals, multi-processor systems, microprocessor-based systems, programmable electronic devices, network PCs, small computers, large computers, distributed computing environments including any of the above systems or devices, etc.

[0059] The above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the present application.

Claims

1. A leakage protection device for a suspended AC power line, characterized in that, The monitoring circuit module, the signal processing module and the circuit breaker are included. Two input terminals of the monitoring circuit module are coupled to the AC power supply line respectively, and an output terminal of the monitoring circuit is connected to an input terminal of the signal processing module. The monitoring circuit module includes a voltage dividing unit and a power taking coil. An input terminal of the voltage dividing unit is coupled to the AC power supply line and is configured to balance voltage dividing based on the voltage of the AC power supply line. An output terminal of the voltage dividing unit is coupled to an input terminal of the power taking coil. An output terminal of the power taking coil is connected to an input terminal of the signal processing module. The signal processing module is configured to receive the ground leakage current, amplify, filter and buffer process the ground leakage current. Based on the current signal of the buffered ground leakage current, a trip command is generated and output to the circuit breaker. An input terminal of the circuit breaker is connected to an output terminal of the signal processing module. A control terminal of the circuit breaker is coupled to the AC power supply line. The circuit breaker is configured to perform on-off control of the AC power supply line based on the trip command. The monitoring circuit module further includes a common mode filter circuit. The voltage dividing unit includes a cement resistance voltage dividing circuit.

2. The ground fault protection device of claim 1, wherein, The power taking coil includes a power taking coil circuit. An input terminal of the common mode filter circuit is coupled to the high voltage phase line of the AC power supply line. An output terminal of the common mode filter circuit is electrically connected to an input terminal of the cement resistance voltage dividing circuit. An output terminal of the cement resistance voltage dividing circuit is grounded. An input terminal of the power taking coil circuit is coupled between the output terminal of the cement resistance voltage dividing circuit and the ground. An output terminal of the power taking coil circuit is electrically connected to the signal processing module. The common mode filter circuit is configured to filter out the harmonic pulse of the current in the AC power supply line. The cement resistance voltage dividing circuit is configured to balance voltage dividing based on the cement resistance voltage of the current in the AC power supply line. The power taking coil circuit is configured to obtain the ground leakage current between the AC power supply line and the ground. The power taking coil circuit obtains the ground leakage current between the cement resistance voltage dividing circuit and the ground through electromagnetic induction and / or capacitive coupling. The leakage protection device further includes a power supply module. The power supply module is configured to provide working voltage for the signal processing module. The power supply module includes a rectifier unit and a voltage conversion unit. An input terminal of the rectifier unit is coupled to an external AC power source. An output terminal of the rectifier unit is electrically connected to an input terminal of the voltage conversion unit. The rectifier unit is configured to rectify the external AC power source. An output terminal of the voltage conversion unit is electrically connected to the signal processing module. The voltage conversion unit is configured to convert the rectified external AC power source into a DC power source.

3. The ground fault protection device of claim 2, wherein, The power supply module further comprises an overvoltage protection unit; the overvoltage protection unit is connected in parallel to the output end of the voltage conversion unit, and the overvoltage protection unit is configured to trigger short-circuit protection when the working voltage abnormally rises.

4. The ground fault protection device of claim 1, wherein, The signal processing module comprises a signal amplification unit, a signal buffering unit and an optical coupling isolation unit; The input end of the signal amplification unit is electrically connected to the monitoring circuit module, the output end of the signal amplification unit is electrically connected to the input end of the signal buffering unit, the output end of the signal buffering unit is electrically connected to the input end of the optical coupling isolation unit, and the output end of the optical coupling isolation unit is electrically connected to the circuit breaker. The signal amplification unit is configured to amplify the ground leakage current, the signal buffering unit is configured to filter and buffer the amplified ground leakage current, and the optical coupling isolation unit is configured to output a tripping instruction based on the filtered and buffered ground leakage current.

5. A monitoring circuit applied to a suspended AC power supply line, the monitoring circuit being included in the leakage protection device according to any one of claims 1-4, characterized in that, The common-mode filter circuit comprises a transformer U7, a transformer U8, a capacitor C15, a capacitor C16 and a capacitor C17. Two input ends of the transformer U7 are respectively coupled to two high-voltage phase lines of the AC power supply line, and two output ends of the transformer U7 are respectively electrically connected to two input ends of the transformer U8; two output ends of the transformer U8 are both electrically connected to the cement resistance voltage dividing circuit. The capacitor C15 is connected in parallel to the two output ends of the transformer U7, and the capacitor C16 and the capacitor C17 are connected in series and then connected in parallel to the two output ends of the transformer U8. The cement resistance voltage dividing circuit comprises a resistor R22 and a resistor R23.

6. The monitoring circuit of claim 5, wherein, One end of the resistor R22 and one end of the resistor R23 are both electrically connected to the common-mode filter circuit, and the other end of the resistor R22 and the other end of the resistor R23 are grounded. The resistor R22 and the resistor R23 have equal resistance values. ​

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