Residual current detection circuit applied to residual current operated protector

Abstract

A residual current detection circuit applied to a residual current operated protector belongs to the technical field of residual current operated protectors and comprises a voltage detection module and a current detection module. The device also comprises a power conversion circuit, a first signal amplification circuit, a second signal amplification circuit, a waveform detection control circuit, a communication circuit, a state display circuit and a protection tripping circuit. The voltage detection module, the current detection module, the power conversion circuit, the first signal amplification circuit, the second signal amplification circuit, the waveform detection control circuit, the communication circuit, the state display circuit and the protection tripping circuit are installed in the residual current operated protector and are electrically connected. According to the waveform detection control circuit, the waveform of human body electric shock current and the waveform of equipment sudden change electric leakage are distinguished according to the difference between the waveform of the human body electric shock current and the waveform of equipment sudden change electric leakage, safety protection of human body electric shock can be guaranteed, power supply reliability of a power grid can be guaranteed when equipment sudden change electric leakage occurs, and technical support is provided for reliable work of the residual current operated protector.

Description

Technical Field

[0001] This utility model relates to the field of circuit technology for residual current operated protective devices, and in particular to a residual current detection circuit for residual current operated protective devices. Background Technology

[0002] A residual current operated protective device (RCD) is an electrical protection device installed in low-voltage power grids. It is an effective protective device against electric shock, electrical fires, and damage to electrical equipment. Currently, the detection circuit used in RCDs primarily employs a zero-sequence current transformer to detect residual current signals. When there is no residual current, the current flowing into and out of the zero-sequence current transformer is equal, resulting in no induced magnetic field generated in the transformer and thus no residual current. The RCD's trip unit will not be energized and will continue to supply power to the load. When there is residual current, the current flowing out of and into the zero-sequence current transformer is not equal, generating an induced signal on the secondary side of the transformer. When the residual current value reaches the set operating value, the induced signal on the transformer's secondary side is amplified and output through relevant circuits to power the trip unit. Upon energization, the trip unit's switch operates, disconnecting the power supply to the load, thereby achieving residual current protection.

[0003] Although existing residual current circuit breakers (RCCBs) meet operational requirements to a certain extent, they still have the following technical drawbacks due to structural and functional limitations. Firstly, RCCBs rely on detecting leakage signals generated by zero-sequence current transformers to control the tripping action. Zero-sequence current transformers are susceptible to various electromagnetic waves from the surrounding environment. If the zero-sequence current transformer has poor anti-interference capabilities or is aging, electromagnetic waves may still cause it to generate signals, leading to energization of the RCCB's tripping mechanism and preventing normal load operation. Secondly, due to asynchronous disconnection of multiple power switches in the power supply area (asynchronous disconnection refers to the problem caused by time discrepancies during the power outage and startup of different loads), grid-to-ground capacitance, and grid neutral point grounding, the neutral point of the power supply system may momentarily shift. If a zero-sequence current transformer with poor anti-interference performance detects this, it may cause the RCCB to generate an operating signal, resulting in maloperation and significantly impacting normal power supply. Utility Model Content

[0004] To overcome the shortcomings of existing residual current operated protective devices (RCDs), which rely solely on detecting leakage signals generated by zero-sequence current transformers to control the tripping action, as described in the background art, this invention provides a residual current detection circuit for RCD applications. Through the combined action of relevant mechanisms, it distinguishes between the waveform of human electric shock current and the waveform of sudden leakage current in equipment based on their differences. This achieves both safety protection against human electric shock and reliability of power grid supply during sudden leakage current in equipment.

[0005] The technical solution adopted by this utility model to solve its technical problem is:

[0006] A residual current detection circuit for a residual current operated protective device includes a voltage detection module, a current detection module, and further comprises a power conversion circuit, a first signal amplification circuit, a second signal amplification circuit, a waveform detection control circuit, a communication circuit, a status display circuit, and a protection tripping circuit. The voltage detection module, current detection module, power conversion circuit, first signal amplification circuit, second signal amplification circuit, waveform detection control circuit, communication circuit, status display circuit, and protection tripping circuit are installed within the residual current operated protective device. The voltage detection module, first signal amplification circuit, current detection module, and second signal amplification circuit each have multiple outputs. The power output terminal of the power conversion circuit connects to the first signal amplification circuit, the second signal amplification circuit, and the second signal amplification circuit... The power input terminals of the amplifier circuit, waveform detection control circuit, communication circuit, status display circuit, and protection trip circuit are electrically connected. The signal input terminals of the multi-channel voltage detection module and current detection module are electrically connected to the phase and neutral lines of the three-phase four-wire power supply, respectively. The signal output terminals of the multi-channel voltage detection module and current detection module are electrically connected to the signal input terminal of the waveform detection control circuit. The signal output terminal of the waveform detection control circuit is electrically connected to the signal input terminals of the communication circuit, status display circuit, and protection trip circuit, respectively. The power output terminal of the protection trip circuit is electrically connected to the power input terminal of the trip unit of the residual current device. The signal output terminal of the communication circuit is connected to the signal input terminal of the PC via RS485 data connection.

[0007] Furthermore, the voltage detection module is a voltage transformer, the current detection module is a current transformer, and the phase wires of the three-phase four-wire power supply output from the power output terminal of the residual current device pass through the central hole of the voltage transformer.

[0008] Furthermore, the power conversion circuit includes an electrically connected fuse, a power switch, an AC-to-DC power module, a DC-to-DC power module, and capacitors. One end of the fuse is connected to the power input terminal of the power switch. The power output terminal of the power switch is connected to one power input terminal of the AC-to-DC power module, and to the positive power input terminals of the two DC-to-DC power modules, one end of the first capacitor, and one end of the second capacitor. The positive power output terminals of the two DC-to-DC power modules are respectively connected to one end of the third capacitor and one end of the fourth capacitor. The negative power output terminals of the two DC-to-DC power modules are respectively connected to the other end of the four capacitors and the negative power output terminal of the AC-to-DC power module.

[0009] Furthermore, the first signal amplification circuit includes an operational amplifier and a resistor and a capacitor that are electrically connected. The Vout pin of the operational amplifier is connected to one end of the resistor, the GND pin of the operational amplifier is connected to one end of the capacitor, and the other end of the capacitor is connected to the other end of the resistor.

[0010] Furthermore, the second signal amplification circuit includes an operational amplifier and resistors and capacitors that are electrically connected. The Vout pin of the operational amplifier is connected to one end of the first resistor. The GND pin of the operational amplifier is connected to one end of the first capacitor, one end of the second resistor, one end of the second capacitor, and the Vin+ pin of the operational amplifier. The other end of the first capacitor is connected to the other end of the first resistor. The other end of the second resistor is connected to one end of the third resistor, the Vin- pin of the operational amplifier, and the other end of the second capacitor.

[0011] Furthermore, the waveform detection and control circuit includes a microcontroller module, a resistor, a crystal oscillator, and a capacitor that are electrically connected. The XTAL1 and XTAL2 ports of the microcontroller module are connected to both ends of the crystal oscillator, and one end of the first capacitor and one end of the second capacitor are respectively connected. The other end of the first capacitor and the other end of the second capacitor are connected.

[0012] Furthermore, the communication circuit includes an electrically connected RS485 module and resistors and capacitors. The two differential signal pins of the RS485 module are respectively connected to one end of the first resistor, one end of the second resistor, and one end of the third resistor. The other end of the third resistor is connected to one end of the first capacitor. The other end of the first resistor is connected to one end of the second capacitor. The other ends of the two capacitors are connected.

[0013] Furthermore, the status display circuit includes resistors and light-emitting diodes that are electrically connected, with one end of each resistor connected to the positive terminal of each of the two light-emitting diodes, and the negative terminals of the two light-emitting diodes connected.

[0014] Furthermore, the protection trip circuit includes an electrically connected resistor, capacitor, field-effect transistor, relay, warning light, buzzer, and diode. The negative terminals of the first and second diodes, the positive terminal of the first capacitor, and the positive terminals of the buzzer and warning light are connected to the power input terminals. The positive terminal of the second diode is connected to one end of the electromagnetic coil of the buzzer, warning light, and relay. The other end of the electromagnetic coil of the relay is connected to the drain of the field-effect transistor. The gate of the field-effect transistor is connected to one end of the first resistor, one end of the second resistor, and one end of the second capacitor. The other end of the second capacitor is connected to the other end of the first resistor and the source of the field-effect transistor.

[0015] Compared with existing technologies, the advantages of this invention are as follows: In conjunction with a residual current device (RCD), the waveform detection and control circuit, under the combined action of related circuits, distinguishes between the waveform of human electric shock current and the waveform of sudden leakage current in equipment. This achieves both safety protection against human electric shock and reliability of power grid supply during sudden leakage current in equipment, providing favorable technical support for the reliable operation of the RCD. In summary, this invention has good application prospects. Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] Figure 1 This is a schematic diagram of the structure of this utility model.

[0018] Figure 2 This is the circuit diagram of this utility model. Detailed Implementation

[0019] Figure 1 , 2 As shown, a residual current detection circuit for a residual current operated device (RCD) includes a voltage detection module A3, a current detection module A2, and further comprises a power conversion circuit 1, a first signal amplification circuit 2, a second signal amplification circuit 3, a waveform detection control circuit 4, a communication circuit 5, a status display circuit 6, and a protection tripping circuit 7. The voltage detection module A3, current detection module A2, power conversion circuit 1, first signal amplification circuit 2, second signal amplification circuit 3, waveform detection control circuit 4, communication circuit 5, status display circuit 6, and protection tripping circuit 7 are mounted on the circuit board of the RCD 8. The voltage detection module A3 and the first signal amplification circuit 2 each have three channels, and the current detection module A2 and the second signal amplification circuit 3 each have four channels.

[0020] Figure 1 , 2As shown, voltage detection module A3 is a voltage transformer, current detection module A2 is a current transformer, and the three phase lines of the three-phase four-wire power supply output from the power output terminal of the residual current device 7 pass through the center holes of the three sets of voltage transformers A3 respectively. The power conversion circuit includes a fuse FUSE1, a power switch JF1, and AC-to-DC power modules A1, U2, and U3, and capacitors C4, C5, and C6, all connected via circuit board wiring. One end of the fuse FUSE1 is connected to the power input terminal of the power switch JF1. The power output terminal of the power switch JF1 is connected to the power input terminal of the AC-to-DC power module A1. The positive power output terminal of the AC-to-DC power module A1 is connected to pin 2 of the positive power input terminals of the two DC-to-DC power modules U2, one end of the first capacitor C4, and one end of the second capacitor C6. Pin 3 of the positive power output terminals of the two DC-to-DC power modules U2 and U3 is connected to one end of the third capacitor C5 and one end of the fourth capacitor C6, respectively. Pin 4 of the negative power output terminals of the two DC-to-DC power modules U2 and U3 is connected to the other ends of the four capacitors C4, C5, C6, and C7, respectively. Pin 4 of the negative power output terminal of the AC-to-DC power module A1 is also connected. The first signal amplification circuit includes an operational amplifier A7, a resistor R4, and a capacitor C1 connected via circuit board wiring. The Vout pin of operational amplifier A7 is connected to one end of resistor R4, the GND pin of operational amplifier A7 is connected to one end of capacitor C1, and the other end of capacitor C1 is connected to the other end of resistor R4. The second signal amplification circuit includes an operational amplifier A8, a resistor R2, R3, and R5, and capacitors C2 and C3 connected via circuit board wiring. The Vout pin of operational amplifier A8 is connected to one end of the first resistor R5. The GND pin of operational amplifier A8 is connected to one end of the first capacitor C2, one end of the second resistor R3, one end of the second capacitor C3, and the Vin+ pin of operational amplifier A8. The other end of the first capacitor C2 is connected to the other end of the first resistor R5. The other end of the second resistor R3 is connected to one end of the third resistor R2, the Vin- pin of operational amplifier A8, and the other end of the second capacitor C3. The waveform detection and control circuit includes a microcontroller module U1, a crystal oscillator XT1, and capacitors C9 and C10 connected via circuit board wiring. The XTAL1 and XTAL2 ports of the microcontroller module U1 are connected to both ends of the crystal oscillator XT1, one end of the first capacitor C9, and one end of the second capacitor C10. The other end of the first capacitor C9 and the other end of the second capacitor C10 are connected together. The communication circuit includes an RS485 module A4 and resistors R10, R11, and R12, and capacitors C12 and C13 connected via circuit board wiring. The two differential signal pins of the RS485 module A4 are connected to one end of the first resistor R12, one end of the second resistor R11, and one end of the third resistor R10. The other end of the third resistor R10 is connected to one end of the first capacitor C12, and the other end of the first resistor R12 is connected to one end of the second capacitor C13. The other ends of the two capacitors C12 and C13 are connected together.The status display circuit includes resistors R7 and R8 and light-emitting diodes LED1 and LED2 connected via circuit board wiring. One end of each resistor R7 and R8 is connected to the positive terminal of each light-emitting diode LED1 and LED2, and the negative terminal of each light-emitting diode LED1 and LED2 is connected. The protection trip circuit includes resistors R6 and R9, capacitor C11, field-effect transistor Q1, relay RJ1, warning light H, buzzer B, and diodes D1 and D2 connected via circuit board wiring. The negative terminals of the first diode D1 and the second diode D2, the positive terminal of the first capacitor C1, the positive terminals of buzzer B and warning light H are connected to the power input terminals. The positive terminal of the second diode D2 is connected to buzzer B, warning light H, and one end of the electromagnetic coil of relay RJ1. The other end of the electromagnetic coil of relay RJ1 is connected to the drain of field-effect transistor Q1. The gate of field-effect transistor Q1 is connected to one end of the first resistor R6, one end of the second resistor R9, and one end of the second capacitor C11. The other end of the second capacitor C11 is connected to the other end of the first resistor R9 and the source of field-effect transistor Q1.

[0021] Figure 1 , 2As shown, the power input terminals of the AC-to-DC power module A1 are connected to pins 1 and 2 of the three-phase four-wire power supply via wires (220V). Pins 3 and 4 of the AC-to-DC power module A1 are connected to the positive terminal of diode D1 and the negative terminal of capacitor C1 via wires. Pin 3 of the DC-to-DC power module U2 is connected to pin 1 of the microcontroller module U1 and the other end of capacitor C10, the VCC of operational amplifier A7 and the other end of capacitor C1, and the VCC of operational amplifier A8 and the other end of capacitor C2 via wires. Pin 3 of the DC-to-DC power module U3 is connected to the negative terminal of capacitor C7, the other end of resistor R11, and the other end of capacitor C13 via wires. The signal input terminals of the three-channel voltage detection module A3 are connected to the three phase lines A, B, and C of the three-phase four-wire power supply via wires. The signal input terminals of the four-channel current detection module A2 are connected to the three phase lines A, B, and C of the three-phase four-wire power supply and the neutral line N via wires. The other end of resistor R4 at the signal output terminal of the three-channel first signal amplifier circuit is connected to the ADLV5, ADLV6, and ADLV7 pins of the microcontroller module U1 via wires. The other end of resistor R5 at the signal output terminal of the four-channel second signal amplifier circuit is connected to the ADLV1, ADLV2, ADLV3, and ADLV4 pins of the microcontroller module U1 via wires. The TX, RX, and EN pins of the microcontroller module U1 are connected to the data transmit, data receive, and transmit / receive enable pins of the RS485 module via wires. The Run and AIarm-1 pins of the microcontroller module U1 are also connected via wires. The pins of the microcontroller module U1 and the other ends of resistors R7 and R8 are connected by wires; the AIarm-2 pin of the microcontroller module U1 is connected to the other end of resistor R6; the feedbackb and feedbacka ports of the microcontroller module U1 are connected to the relay control contact and normally open contact by wires; the negative terminal of diode D1 and one end of the electromagnetic coil of relay RJ1 are connected to the power input terminal of the trip coil J0 of the residual current device by wires; the other end of resistor R11 and the other end of capacitor C13 of the communication circuit are connected to the signal input terminal of the PC via RS485 data connection. The signal output terminals (siUa, siUb, siUc pins) of the three-channel voltage detection module A3 are connected to the Vin_ pins of the three op-amps A7 by wires; the signal output terminals (Ia, Ib, Ib, Id pins) of the four-channel current detection module A2 are connected to the Vin_ pins of the four op-amps A8 by wires.

[0022] Figure 1 , 2As shown, this new type of power supply is mainly used in conjunction with a residual current device (RCD) for protection. The working process is as follows: In the figure, the AC-to-DC power supply module A1 (AC 220V to DC 12V switching power supply module) is connected to a 220VAC power supply via fuse FUSE1 (overcurrent protection) and power switch JF1. After turning on the power switch JF1, the AC-to-DC power supply module A1 outputs a 12V DC power supply. The 12V voltage supplies the DC-to-DC power supply module U2 (DC 12V to DC 3.3V power supply module, model ME6203A33PG), the DC-to-DC power supply module U3 (DC 12V to DC 5V power supply module, model AMS1117-5.0), and their trip protection circuits. The DC-to-DC power supply module U2 reduces the 12V DC power supply to 3.3V DC power to supply operational amplifiers A7 and A8 and the microcontroller module U1. Capacitor C4 is used to filter out high-frequency noise or unstable voltage fluctuations at the power input terminal to stabilize the voltage input to the DC-to-DC power supply module U2. Capacitor C5 is the output capacitor of the DC-to-DC power supply module U2, used to stabilize the output voltage of the DC-to-DC power supply module U2 and reduce output voltage ripple and noise. The DC-to-DC power supply module U3 reduces the 12V power supply to 5V DC power to supply the communication module A4 (RS485 module). The function of capacitor C6 is the same as that of capacitor C4, and the function of capacitor C7 is the same as that of capacitor C5. After the three-channel voltage detection module A3 (model XRGW220 / 2LOAD) is connected to the power grid, its internal circuitry steps down and rectifies the AC power supply, then outputs it to operational amplifier A7 via the siUa terminal (or siUb, siUc pins). Operational amplifier A7 amplifies the received voltage signal. The amplified voltage signal output by operational amplifier A7 passes through a low-pass filter composed of resistor R4 and capacitor C1 to filter out interference signals, and is finally output to the ADLV5 or ADLV6, ADLV7 pins of the microcontroller module U1 as a signal acquisition. The four-channel current detection module A2 (model MB6S) is connected to the power grid at its input terminal. After rectification, the power is output from terminal Ia (or terminals Ib, Ib, Id) to resistor R2. The power signal passes through a low-pass filter composed of resistor R2 and capacitor C3 and enters the signal input terminal of operational amplifier A8 (used to amplify the current signal output from terminal Ia or terminals Ib, Ib, Id). R3 is a sampling resistor used to convert the current signal into a voltage signal and output it to the ADLV1 or ADLV2, ADLV3, ADLV4 pins of microcontroller module U1 for signal acquisition. Specifically, the signal output by operational amplifier A8 passes through a low-pass filter composed of resistor R5 and capacitor C2 and is finally output to the ADLV1 or ADLV2, ADLV3, ADLV4 pins of microcontroller module U1.

[0023] Figure 1 , 2In this system, the microcontroller module U1 (model AT32F413RCT7) performs waveform sampling and filtering of the mains voltage and current data acquired via pins 2-8. Simultaneously, it controls the outputs of the first-level alarm Alarm_1 and the second-level alarm Alarm_2 pins, outputs the device's operating status, receives the trip feedback signals feedbacka and feedbackb, and communicates with the host computer via pins 15, 16, and 17 through pins 25, 26, 27, 28, and 29. In specific applications, the waveform of the current from human contact is constrained by the resistance characteristics of the human body, resulting in a complex electrical network. Under normal conditions, this primarily depends on the skin impedance. After an electric shock, the skin impedance is a time-varying network for a very short time (approximately 2-3 current wave cycles), decreasing in resistance, and then transitions to a non-time-varying network. This characteristic of skin impedance... The current flowing through the human body exhibits a periodic function characteristic, increasing initially and then stabilizing. The microcontroller module U1 is used to detect this waveform in real time. The data acquired by the microcontroller module U1 can also be sent to the communication module A4 (RS485 module, model MAX485) via serial port pins 15 and 16. The RS485 module's data transmission and reception are switched via pin 1 of the microcontroller module controlled by pin 16 of the microcontroller module. The differential signal output by the RS485 module is sent to the terminal device (PC) via cable for remote observation and event querying. The external components of the RS485 module A4 include resistors R11 and R12, which are voltage divider resistors, allowing the voltage at point A of the RS485 module to be obtained from the voltage divider. Resistor R10 is also a voltage divider resistor, allowing the voltage at point B of the RS485 module to be obtained from it. Capacitors C12 and C13 are two isolation capacitors, primarily preventing external signals from interfering with the output differential signal.

[0024] Figure 1 , 2In the microcontroller module U1, pin 25 is used for alarm signals output via the alarm_1 pin; pin 27 is used for human body electric shock alarm and protection signals output via the alarm_2 pin; pin 26 is used for equipment operation indication output via the RUN pin; and pins 28 and 29 are used to provide feedback on the tripping status of the residual current device (RCD). When the microcontroller module U1 detects a leakage current waveform that is not a human body electric shock waveform, pin 25 (alarm_1) is set high to drive LED2 indicator light to illuminate as a warning (level 2 alarm). Simultaneously, the signal output from the alarm_1 pin is transmitted to a remote PC via serial communication pins 15, 16, and 17 of the microcontroller module U1 to indicate that the level 2 alarm has been activated. When the equipment is in operation, pin 26 (RUN) is set high to illuminate LED1 for equipment operation indication. When the microcontroller module U1 detects a human electric shock waveform, pin 27 (Alarm_2) goes high. At this time, the gate of the field-effect transistor Q1 reaches the turn-on voltage, and Q1 conducts. When Q1 conducts, the coil of relay RJ1 conducts, and the warning light H (a 1W red LED), buzzer B (an FM12V active continuous-sound alarm), and the external trip coil all work simultaneously (the residual current device trips). Simultaneously, the normally open contact and control contact of relay RJ1 close, sending a closing signal to pins 28 and 29 of the microcontroller module U1. Pins 28 and 29 are used to feedback to the microcontroller module U1 that the first-level alarm protection has been activated. This feedback signal is transmitted to a remote PC via the serial port of the microcontroller module U1 to inform the monitoring personnel that the first-level alarm protection has been activated. Pins 13 and 14 of the microcontroller module U1 are used to input crystal oscillator signals from an external source for the module's use. Capacitors C9 and C10, along with the crystal oscillator, form an oscillation circuit. During operation, pin 26 of the microcontroller module U1 outputs a high level (3.3V), which is then stepped down and current-limited by resistor R7 before entering the positive power input terminal of LED1, energizing LED1 and causing it to light up. Similarly, pin 25 of the microcontroller module U1 outputs a high level (3.3V), which is then stepped down and current-limited by resistor R8 before entering the positive power input terminal of LED2, energizing LED2 and causing it to light up. When pin 27 of the microcontroller module U1 outputs a high level, it enters the gate of the field-effect transistor Q1 through a low-pass filter circuit composed of R6 and C11. Resistor R9 provides the required bias voltage for the input. Since the microcontroller module input is high, the voltage across resistor R9 reaches the turn-on voltage of the field-effect transistor Q1, turning it on. The 12V DC power passes through diode D1 (to prevent reverse polarity) to the trip unit (connected to the trip unit coil). Diode D2 is a reverse-voltage withstand diode to prevent overvoltage. Electrolytic capacitor C8 mainly serves as an energy storage device, simultaneously driving the buzzer warning light and energizing the trip unit coil.After the relay RJ1 coil is turned on, the trip unit, buzzer, and warning light can operate simultaneously. After the relay coil RJ1 is turned on, its normally open contact closes, and the microcontroller module K1 can detect that the trip unit has tripped and that the warning light has been turned on.

[0025] Figure 1 , 2 As shown above, through the application of this novel synergistic residual current operated protector, under the joint action of related circuits, the waveform detection and control circuit distinguishes between the waveform of human electric shock current and the waveform of sudden leakage current in equipment based on their differences. This achieves both safety protection against human electric shock and reliability of power grid supply in the event of sudden leakage current in equipment, providing favorable technical support for the reliable operation of the residual current operated protector.

[0026] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. It will be apparent to those skilled in the art that this utility model is limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or basic characteristics of this utility model. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of this utility model is defined by the appended claims rather than the foregoing description, and thus all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this utility model.

[0027] Furthermore, it should be understood that although this specification describes the embodiments, the embodiments do not necessarily contain only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in the embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A residual current detection circuit for use in a residual current operated protective device, characterized in that, The circuit includes a voltage detection module, a current detection module, a power conversion circuit, a first signal amplification circuit, a second signal amplification circuit, a waveform detection control circuit, a communication circuit, a status display circuit, and a protection tripping circuit. These components are installed within the residual current device. The voltage detection module, first signal amplification circuit, current detection module, and second signal amplification circuit each have multiple outputs. The power output terminal of the power conversion circuit connects to the first signal amplification circuit, second signal amplification circuit, and waveform detection control circuit. The power input terminals of the control circuit, communication circuit, status display circuit, and protection trip circuit are electrically connected. The signal input terminals of the multi-channel voltage detection module and current detection module are electrically connected to the phase and neutral lines of the three-phase four-wire power supply, respectively. The signal output terminals of the multi-channel voltage detection module and current detection module are electrically connected to the signal input terminal of the waveform detection control circuit. The signal output terminal of the waveform detection control circuit is electrically connected to the signal input terminals of the communication circuit, status display circuit, and protection trip circuit, respectively. The power output terminal of the protection trip circuit is electrically connected to the power input terminal of the trip unit of the residual current device. The signal output terminal of the communication circuit is connected to the signal input terminal of the PC via RS485 data connection.

2. The residual current detection circuit for a residual current operated protective device according to claim 1, characterized in that, The voltage detection module is a voltage transformer, the current detection module is a current transformer, and the phase wires of the three-phase four-wire power supply output from the power output terminal of the residual current device pass through the center hole of the voltage transformer.

3. The residual current detection circuit for a residual current operated protective device according to claim 1, characterized in that, The power conversion circuit includes an electrically connected fuse, a power switch, an AC-to-DC power module, a DC-to-DC power module, and capacitors. One end of the fuse is connected to the power input terminal of the power switch. The power output terminal of the power switch is connected to one power input terminal of the AC-to-DC power module. The positive power output terminal of the AC-to-DC power module is connected to the positive power input terminals of the two DC-to-DC power modules, one end of the first capacitor, and one end of the second capacitor. The positive power output terminals of the two DC-to-DC power modules are respectively connected to one end of the third capacitor and one end of the fourth capacitor. The negative power output terminals of the two DC-to-DC power modules are respectively connected to the other end of the four capacitors and the negative power output terminal of the AC-to-DC power module.

4. The residual current detection circuit for a residual current operated protective device according to claim 1, characterized in that, The first signal amplification circuit includes an operational amplifier and resistors and capacitors that are electrically connected. The Vout pin of the operational amplifier is connected to one end of the resistor, the GND pin of the operational amplifier is connected to one end of the capacitor, and the other end of the capacitor is connected to the other end of the resistor.

5. The residual current detection circuit for a residual current operated protective device according to claim 1, characterized in that, The second signal amplification circuit includes an operational amplifier and resistors and capacitors that are electrically connected. The Vout pin of the operational amplifier is connected to one end of the first resistor. The GND pin of the operational amplifier is connected to one end of the first capacitor, one end of the second resistor, one end of the second capacitor, and the Vin+ pin of the operational amplifier. The other end of the first capacitor is connected to the other end of the first resistor. The other end of the second resistor is connected to one end of the third resistor, the Vin- pin of the operational amplifier, and the other end of the second capacitor.

6. The residual current detection circuit for a residual current operated protective device according to claim 1, characterized in that, The waveform detection and control circuit includes a microcontroller module, resistors, crystal oscillators, and capacitors that are electrically connected. The XTAL1 and XTAL2 ports of the microcontroller module are connected to both ends of the crystal oscillator, and one end of the first capacitor and one end of the second capacitor are connected respectively. The other end of the first capacitor and the other end of the second capacitor are connected.

7. The residual current detection circuit for a residual current operated protective device according to claim 1, characterized in that, The communication circuit includes an electrically connected RS485 module and resistors and capacitors. The two differential signal pins of the RS485 module are connected to one end of the first resistor, one end of the second resistor, and one end of the third resistor, respectively. The other end of the third resistor is connected to one end of the first capacitor. The other end of the first resistor is connected to one end of the second capacitor. The other ends of the two capacitors are connected together.

8. The residual current detection circuit for a residual current operated protective device according to claim 1, characterized in that, The status display circuit includes electrically connected resistors and light-emitting diodes (LEDs). One end of each of the two resistors is connected to the positive terminal of each of the two LEDs, and the negative terminals of the two LEDs are connected to each other.

9. The residual current detection circuit for a residual current operated protective device according to claim 1, characterized in that, The protection trip circuit includes electrically connected resistors, capacitors, field-effect transistors, relays, warning lights, buzzers, and diodes. The negative terminals of the first and second diodes, the positive terminal of the first capacitor, and the positive terminals of the buzzer and warning light are connected to the power input terminals. The positive terminal of the second diode is connected to one end of the buzzer, warning light, and relay electromagnetic coil. The other end of the relay electromagnetic coil is connected to the drain of the field-effect transistor. The gate of the field-effect transistor is connected to one end of the first resistor, one end of the second resistor, and one end of the second capacitor. The other end of the second capacitor is connected to the other end of the first resistor and the source of the field-effect transistor.

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