Residual current protection test method, device and circuit breaker

Abstract

The present invention discloses a residual current protection test method, which belongs to the field of low-voltage electrical technology. A simulated residual current signal is input to a test coil on a residual current transformer, and the residual current protection function module is verified to be normal based on the response of the residual current protection function module to the simulated residual current signal; the simulated residual current signal is input according to the following method: an identical pulse signal is input at both ends of the test coil according to a time difference Δt, and the time difference Δt satisfies: t w ≤Δt≤T‑t w , t w , T represent the pulse width and pulse period of the pulse signal, respectively. The present invention also discloses a residual current protection test device and a circuit breaker. Compared to existing technologies, the present invention effectively eliminates the effect of residual magnetism on the measurement accuracy of the residual current transformer without requiring demagnetization during the test process. Furthermore, the present invention has a simple circuit structure, low implementation cost, and high reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of low-voltage electrical appliances, and in particular to a residual current protection test method and device. Background Art

[0002] Residual current protection devices (RCDs) are common protective devices in power systems, used to detect residual current or ground fault current. They require regular testing using a simulated test circuit to verify the function of the RCT. This simulates a residual current in the test coil of the RCT. Once the RCT's measuring coil detects this signal, the control circuit identifies a residual current fault and trips the trip unit.

[0003] Currently, there are two common simulation test circuit schemes for residual current protection devices. The first involves connecting a high-power resistor, a test coil, and a test button in series between any two phases of the main circuit. Pressing the test button activates the circuit, simulating a residual current. The residual current protection device identifies a residual current fault and outputs a trip signal to open the circuit breaker. The second method uses an oscillator circuit to generate a low-frequency sinusoidal oscillation to simulate a residual current signal. Pressing the test button activates the oscillator circuit, simulating a residual current fault and causing the circuit breaker to trip.

[0004] Disadvantages of Solution 1: If one phase of the main circuit connected to the test circuit is disconnected, the test circuit loses power supply and the test will not function. At the same time, since a high-power resistor is used as a current-limiting resistor and forms the test current with the AC voltage, the power loss is large and a large heat dissipation area is required. In addition, if the test button is pressed continuously, the trip coil will be energized for a long time and easily burn out when the circuit breaker fails to trip normally or the line is reversed. Its reliability, practicality and safety are not high.

[0005] Disadvantages of Option 2: Generating low-frequency sinusoidal oscillations through an oscillation circuit requires configuring corresponding integrated components and inductors and capacitors. Generating low-frequency signals requires larger inductors and capacitors. Such a circuit will increase production costs. At the same time, since the circuit structure is more complex than Option 1, the probability of failure of the simulation test circuit will increase.

[0006] Chinese patent CN201001022Y discloses a simulation test circuit for a residual current protection device. This circuit is implemented using a single-chip microcomputer (MCU). The MCU's I / O port outputs a PWM signal, which simulates the residual current signal through a test coil. This solution overcomes drawbacks such as the inability to perform tests in the event of a phase failure, the high energy loss and increased size of high-power resistors, and the tendency for the trip coil to burn out due to continuous presses of the test button. However, a problem remains: the PWM signal is a unidirectional pulse signal. Since the residual current transformer (RCT) is a toroidal core made of magnetically conductive material, it generates residual magnetism when excited by a unidirectional current. Once generated, this residual magnetism persists for a long time under normal operating conditions, affecting the accuracy of the RCT and, in severe cases, causing malfunction or failure of the circuit breaker. Research and experiments have shown that a residual magnetism reduction of 10%-20% is optimal to effectively ensure the performance of the RCT. Currently, demagnetization is the only solution to address residual magnetism, but most RCTs lack this function.

[0007] As residual current protection devices develop towards intelligence, there is an urgent need for a simple and reliable method to implement residual current simulation tests that can overcome the above shortcomings. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide a residual current protection test method, which can effectively eliminate the influence of residual magnetism on the measurement accuracy of the residual current transformer without demagnetization during the test process, and has a simple circuit structure, low implementation cost and high reliability.

[0009] The present invention specifically adopts the following technical solutions to solve the above technical problems:

[0010] A residual current protection test method comprises inputting a simulated residual current signal into a test coil on a residual current transformer, and verifying whether the residual current protection function module is normal according to the response of the residual current protection function module to the simulated residual current signal; inputting the simulated residual current signal in accordance with the following method: inputting an identical pulse signal at both ends of the test coil according to a time difference Δt, wherein the time difference Δt satisfies: t w ≤Δt≤Tt w , t w , T represent the pulse width and pulse period of the pulse signal respectively.

[0011] Preferably, the pulse signal is input to both ends of the test coil respectively through two I / O ports of the single chip microcomputer.

[0012] Preferably, the duty cycle of the pulse signal is less than or equal to 0.5.

[0013] Preferably, the frequency of the pulse signal is 50 Hz.

[0014] Based on the same inventive concept, the following technical solutions can also be obtained:

[0015] A residual current protection test device is used to input a simulated residual current signal to a test coil on a residual current transformer, and verify whether the residual current protection function module is normal based on the response of the residual current protection function module to the simulated residual current signal; the residual current protection test device inputs the simulated residual current signal according to the following method: input an identical pulse signal at both ends of the test coil according to a time difference Δt, and the time difference Δt satisfies: t w ≤Δt≤Tt w , t w , T represent the pulse width and pulse period of the pulse signal respectively.

[0016] Preferably, the pulse signal is input to both ends of the test coil respectively through two I / O ports of the single chip microcomputer.

[0017] Further preferably, the device also includes a test circuit, which includes: a varistor RV1, a capacitor C1, inductors L1 and L2, and resistors R1 and R2; an I / O port of the microcontroller is connected to one end of the resistor R1, the other end of the resistor R1 is connected to one end of the inductor L1, the other end of the inductor L1 is connected to one end of the test coil, the other end of the test coil is connected to one end of the inductor L2, the other end of the inductor L2 is connected to one end of the resistor R2, and the other end of the resistor R2 is connected to another I / O port of the microcontroller, and the varistor RV1 and the capacitor C1 are connected in parallel at both ends of the test coil.

[0018] Preferably, the duty cycle of the pulse signal is less than or equal to 0.5.

[0019] Preferably, the frequency of the pulse signal is 50 Hz.

[0020] A circuit breaker comprises a residual current protection function module and a residual current protection test device as described in any one of the above technical solutions.

[0021] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0022] The present invention injects the same pulse signal with a preset time difference into both ends of the test coil of the residual current transformer, thereby generating pulse signals with symmetrical waveforms and opposite directions in the test coil. The residual magnetism generated by the residual current transformer core after being excited by the signal cancels each other out, effectively eliminating the influence of the residual magnetism while simulating the residual current.

[0023] The circuit structure of the present invention is simple, with few components, and has the advantages of low power consumption, low cost, high reliability, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of the structural principle of a specific embodiment of a residual current protection test device of the present invention;

[0025] Figure 2 A circuit diagram of a single chip microcomputer and a trigger circuit in a specific embodiment;

[0026] Figure 3 Schematic diagram of output waveforms of SY1 and SY2 pins in a specific embodiment;

[0027] Figure 4 4 is a circuit diagram of a test circuit in a specific embodiment. DETAILED DESCRIPTION

[0028] In response to the residual magnetism influence problem existing in Chinese patent CN201001022Y, the solution of the present invention is to specially design the pulse signal input for the residual current protection test based on the patent. The same pulse signal with a preset time difference is injected into both ends of the test coil of the residual current transformer, thereby generating pulse signals with symmetrical waveforms and opposite directions in the test coil. The residual magnetism generated by the residual current transformer core after being excited by the signal cancels each other out, effectively eliminating the influence of residual magnetism while realizing the simulation of residual current.

[0029] The present invention specifically adopts the following technical solutions to solve the above technical problems:

[0030] A residual current protection test method comprises inputting a simulated residual current signal into a test coil on a residual current transformer, and verifying whether the residual current protection function module is normal according to the response of the residual current protection function module to the simulated residual current signal; inputting the simulated residual current signal in accordance with the following method: inputting an identical pulse signal at both ends of the test coil according to a time difference Δt, wherein the duty cycle of the pulse signal is less than or equal to 0.5, and the time difference Δt satisfies: t w ≤Δt≤Tt w , t w , T represent the pulse width and pulse period of the pulse signal respectively.

[0031] A residual current protection test device is used to input a simulated residual current signal to a test coil on a residual current transformer, and verify whether the residual current protection function module is normal based on the response of the residual current protection function module to the simulated residual current signal; the residual current protection test device inputs the simulated residual current signal according to the following method: inputting a same pulse signal at both ends of the test coil according to a time difference Δt, the duty cycle of the pulse signal is less than or equal to 0.5, and the time difference Δt satisfies: t w ≤Δt≤Ttw , t w , T represent the pulse width and pulse period of the pulse signal respectively.

[0032] In the above technical solution, the pulse signal can be generated by an independent pulse generating circuit. Considering that existing residual current protection devices and circuit breakers are becoming increasingly intelligent and generally use single-chip microcomputers as controllers, it is preferred that the pulse signal be input to the two ends of the test coil through the two I / O ports of the single-chip microcomputer. This allows the single-chip microcomputers in existing residual current protection devices and circuit breakers to be directly utilized, further reducing production costs and simplifying the system structure.

[0033] The amplitude, duty cycle, period and other parameters of the pulse signal can be flexibly designed according to the residual current actually required to be simulated; preferably, the duty cycle of the pulse signal is equal to 0.5; preferably, the frequency of the pulse signal is 50 Hz.

[0034] To facilitate public understanding, the technical solution of the present invention is described in detail below through a specific embodiment with reference to the accompanying drawings:

[0035] like Figure 1 As shown, the residual current protection test device of this embodiment includes a single-chip microcomputer, a three-phase switching power supply, a flux converter, a line break detection circuit, a drive circuit, a residual current transformer, a sampling circuit, a conditioning circuit, a test circuit, a trigger circuit, an indication circuit, a setting circuit, and an alarm circuit. The single-chip microcomputer is connected to the flux converter via the drive circuit, and the flux converter is connected to the single-chip microcomputer via the line break detection circuit; the measuring coil of the residual current transformer is connected to the conditioning circuit via the sampling circuit, and the conditioning circuit is connected to the single-chip microcomputer; the test coil of the residual current transformer is connected to the single-chip microcomputer via the test circuit, and the residual current transformer test coil, the test circuit, and two I / O ports of the single-chip microcomputer form a loop; the trigger circuit, the indication circuit, the setting circuit, and the alarm circuit are connected to the single-chip microcomputer.

[0036] The working principle and process of the residual current protection test device are as follows:

[0037] When the residual current simulation test button is pressed, the trigger circuit provides a trigger signal to the microcontroller. Upon receiving the trigger signal, the microcontroller begins outputting pulse signals through two I / O pins. This pulse signal, transmitted by the microcontroller, passes through the test circuit to generate a simulated residual current signal in the residual current transformer test coil until the button is released. Simultaneously, the microcontroller samples and processes the simulated residual current signal through the residual current transformer measuring coil, sampling circuit, and conditioning circuit. This signal is compared with the internally set action value and a trip signal is sent to the drive circuit, causing the flux converter to operate and trip the circuit breaker. The microcontroller detects a wire break in the flux converter via a wire break detection circuit. An indicator circuit and an alarm circuit indicate and warn of residual current conditions. A setting circuit is used for parameter setting. A three-phase switching power supply provides power to these circuits.

[0038] The number of turns of the test coil is equal to or greater than 1 turn, and the single chip microcomputer can set the corresponding magnification according to the number of turns of the test coil.

[0039] Figure 2 The single chip microcomputer and trigger circuit in this embodiment are shown. Figure 2 As shown, the trigger circuit includes a resistor R12 and a button SW1. One end of the resistor R12 is connected to VDD, and the other end is connected to the single-chip microcomputer N1. One end of the button SW1 is connected to GND, and the other end is connected to the single-chip microcomputer N1. When the button SW1 is pressed, the level of the corresponding pin of the single-chip microcomputer N1 changes from high level to low level, and the single-chip microcomputer N1 recognizes it as a trigger signal. The single-chip microcomputer N1 sends out an analog residual current signal during the period when SW1 is pressed. The SY1 and SY2 pins are the output pins of the pulse signal, among which the SY1 and SY2 pins connected to the test circuit are non-fixed pins and can be any two I / O ports with input and output functions. Through SY1 and SY2, the same pulse signal is input at both ends of the test coil L according to the time difference Δt. The duty cycle of the pulse signal is less than or equal to 0.5, and the time difference Δt satisfies: t w ≤Δt≤Tt w , t w , T represent the pulse width and pulse period of the pulse signal respectively. In this embodiment, the duty cycle of the pulse signal is 0.5, the frequency of the pulse signal is 50Hz, and t w =Δt=Tt w , the output waveforms of SY1 and SY2 pins are as follows Figure 3Specifically, when microcontroller N1 begins stimulating the simulated residual current signal, pin SY1 generates a high level and pin SY2 generates a low level, generating a forward pulse signal of a set pulse width in the loop formed by the test circuit and test coil L. After a time Δt, pin SY1 generates a low level and pin SY2 generates a high level, generating a reverse pulse signal of the same pulse width in the loop formed by the test circuit and test coil L. The positive and reverse pulse signals alternate to simulate the residual current characteristics. The residual current simulation test signal is a pulse signal with symmetrical waveforms and opposite directions. When excited by this signal, the residual magnetism generated in the residual current transformer core cancels each other out, eliminating the effects of residual magnetism.

[0040] Figure 4 This is the test circuit in this embodiment. This test circuit consists of a varistor RV1, a capacitor C1, inductors L1 and L2, and resistors R1 and R2. Pin SY1 of the microcontroller N1 is connected to one end of resistor R1, the other end of resistor R1 is connected to one end of inductor L1, the other end of inductor L1 is connected to one end of a test coil L, the other end of the test coil L is connected to one end of inductor L2, the other end of inductor L2 is connected to one end of resistor R2, and the other end of resistor R2 is connected to pin SY2 of the microcontroller. The varistor RV1 and capacitor C1 are connected in parallel across the test coil L. The varistor RV1 serves as an overvoltage protector, absorbing the high voltage generated in the test coil L when its subsequent circuit is open. Capacitor C1 and inductors L1 and L2 are used for filtering and anti-interference, enhancing EMC performance. Resistors R1 and R2 provide current limiting protection to prevent current surges. The number of resistors R1 and R2 is equal to or greater than one.

[0041] The residual current protection test device of the present invention can be used for an independent residual current protection device, and can also be used for a residual current protection module in a circuit breaker.

[0042] Due to the adoption of the above technical solution, the residual current simulation test signal in the test coil L is a pulse signal with symmetrical waveforms and opposite directions. After the residual current transformer core is excited by the signal, the residual magnetism generated by it cancels each other out, thereby eliminating the influence of the residual magnetism; the residual current simulation test signal is output by the single-chip microcomputer, using the system power supply VDD, which is powered by a three-phase power supply. Even if a phase of the alternating current is disconnected, the test can still be continued; the circuit structure of the present invention is simple, with few components, and has the advantages of low power consumption, low cost, and high reliability; the residual current simulation test tripping signal is a pulse signal with a fixed pulse width and number emitted by the single-chip microcomputer, which avoids the problem of the tripping coil being easily burned out due to continuous pressing of the test button.

Claims

1. A residual current protection test method, comprising: inputting a simulated residual current signal into a test coil on a residual current transformer, and verifying whether the residual current protection function module is normal based on the response of the residual current protection function module to the simulated residual current signal; characterized in that: Input the simulated residual current signal in the following manner: input the same pulse signal at both ends of the test coil according to the time difference Δt, and the time difference Δt satisfies: t w ≤Δt≤Tt w , t w , T represent the pulse width and pulse period of the pulse signal respectively.

2. The residual current protection test method according to claim 1, characterized in that: The pulse signal is input to both ends of the test coil through the two I / O ports of the single chip microcomputer.

3. The residual current protection test method according to claim 1, characterized in that: The duty cycle of the pulse signal is less than or equal to 0.

5.

4. The residual current protection test method according to claim 1, characterized in that: The frequency of the pulse signal is 50 Hz.

5. A residual current protection test device, for inputting a simulated residual current signal into a test coil on a residual current transformer, and verifying whether the residual current protection function module is normal based on the response of the residual current protection function module to the simulated residual current signal; characterized in that: The residual current protection test device inputs the simulated residual current signal in the following manner: inputting the same pulse signal at both ends of the test coil according to the time difference Δt, wherein the time difference Δt satisfies: w ≤Δt≤Tt w , t w , T represent the pulse width and pulse period of the pulse signal respectively.

6. The residual current protection test device according to claim 5, characterized in that: The pulse signal is input to both ends of the test coil through the two I / O ports of the single chip microcomputer.

7. The residual current protection test device according to claim 6, characterized in that: The device also includes a test circuit, which includes: a varistor RV1, a capacitor C1, inductors L1 and L2, and resistors R1 and R2; an I / O port of the single-chip microcomputer is connected to one end of the resistor R1, the other end of the resistor R1 is connected to one end of the inductor L1, the other end of the inductor L1 is connected to one end of the test coil, the other end of the test coil is connected to one end of the inductor L2, the other end of the inductor L2 is connected to one end of the resistor R2, the other end of the resistor R2 is connected to another I / O port of the single-chip microcomputer, and the varistor RV1 and the capacitor C1 are connected in parallel at both ends of the test coil.

8. The residual current protection test device according to claim 5, characterized in that: The duty cycle of the pulse signal is less than or equal to 0.

5.

9. The residual current protection test device according to claim 5, characterized in that: The frequency of the pulse signal is 50 Hz.

10. A circuit breaker, characterized in that: The invention comprises a residual current protection function module and a residual current protection test device as claimed in any one of claims 5 to 9.

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