A method for testing characteristics of arc fault protection equipment

Abstract

The present invention proposes a method for testing the characteristics of an arc fault protection appliance, which is used to test an AFDD circuit carrying an arc fault protection function. The testing method includes an AFDD circuit and a high-frequency signal generator coupled by a high-frequency magnetic ring; the AFDD circuit passes through the center of the high-frequency magnetic ring, and the signal output end of the high-frequency signal generator is connected to a coil surrounding the high-frequency magnetic ring. After the high-frequency signal output by the high-frequency signal generator is injected into the high-frequency magnetic ring, the arc environment is simulated by the electromagnetic induction effect to test the AFDD circuit; the present invention uses power electronic devices to build a test circuit, simulates the characteristics of the arc fault current appearing in the circuit, and realizes rapid testing of the AFDD. There is a broad market space for the research and development of the AFDD and the research of a portable AFDD test device.

Description

Technical Field

[0001] The invention relates to the technical field of arc fault protection, in particular to a method for testing characteristics of an arc fault protection electrical appliance. Background Art

[0002] According to statistics from the Fire Department of the Ministry of Public Security, the main causes of electrical fires are arc faults, overcurrent, leakage and short circuit faults. There are mature electrical protection devices on the market that can effectively detect overcurrent, leakage and short circuit faults and make corresponding protection strategies, but these products cannot detect arc faults. In order to make up for the "loopholes" in electrical fire protection and strengthen arc fault protection, many scholars at home and abroad have studied arc fault detection and arc fault protection devices (AFDD). Arc fault protection devices are a new type of circuit protection device. When an arc fault is detected, the device reduces the impact of the arc fault by disconnecting the circuit.

[0003] The current technology for testing AFDD has the following disadvantages: the physical device detection method often requires a complete fault arc generating device and a complex set of hardware circuits, which occupies a large area and has a high investment cost. In addition, there are many AFDD test items, and each type of test item is subdivided into many test contents. At the same time, the preparation of cable samples and the preparation of test loads are mixed with many human factors, making the entire AFDD test process time-consuming and greatly increasing the investment in manpower and material resources. It is not suitable as a terminal test equipment for a large number of products leaving the factory.

[0004] The method of using surge suppressors under different spark overvoltages to generate fault arcs with different characteristics to test whether AFDD can correctly detect and trip the time has an average test time of 18.8s, which has poor timeliness. In addition, as the number of tests increases, the surge suppressor itself is damaged, resulting in failure to trigger the arc or premature short circuit, causing the experiment to fail.

[0005] In the test method of selecting a typical fault arc signal through the host computer, the voltage waveform is output to the AFDD after passing through the voltage amplifier circuit, which supplies power to the internal electronic circuit and tripping mechanism of the AFDD; the current waveform is output to the phase line input and output terminals of the AFDD after passing through the transconductance amplifier circuit, which provides the AFDD with a fault arc current signal. Although this method is simple to operate, since the currents flowing through the phase line and the center line of the AFDD are not equal, when the AFDD under test contains a residual current protection function, the test effect is greatly reduced.

[0006] In addition, a method of using an arbitrary waveform generator and a power amplifier to output a fault arc current waveform is used. The arbitrary waveform generator is used to output a typical fault arc current signal, and the current waveform is output through a precision power amplifier to perform a performance test on the AFDD. However, due to the contradiction between the high-frequency response characteristics and the high gain of the power amplifier, the arc current output effect is poor in the high-frequency band of the arc. In addition, high-precision signal generators and high-power power amplifiers are expensive and are not suitable for production line testing of products. Summary of the invention

[0007] The present invention proposes a method for testing the characteristics of arc fault protection appliances, which uses power electronic devices to build a test circuit, simulates the characteristics of arc fault current in the line, and realizes rapid testing of AFDD. It has a broad market space for the research and development of AFDD and the study of portable AFDD testing devices.

[0008] The present invention adopts the following technical solutions.

[0009] A method for testing characteristics of an arc fault protection device is used to test an AFDD circuit that carries an arc fault protection function. The method comprises an AFDD circuit and a high-frequency signal generator coupled by a high-frequency magnetic ring; the AFDD circuit passes through the center of the high-frequency magnetic ring, and the signal output end of the high-frequency signal generator is connected to a coil surrounding the high-frequency magnetic ring. After the high-frequency signal output by the high-frequency signal generator is injected into the high-frequency magnetic ring, the AFDD circuit is tested by simulating an arc environment with an electromagnetic induction effect.

[0010] The high-frequency signal is generated by a high-frequency signal generator and is a high-frequency characteristic signal of a fault arc, and is used as a high-frequency characteristic quantity of the arc current in the test method.

[0011] The high-frequency signal generator includes a high-frequency signal source and a power amplifier for amplifying the power of the high-frequency signal of the high-frequency signal source.

[0012] The AFDD circuit is a main circuit for AFDD testing, and includes a bidirectional thyristor, a load resistor and an AFDD tripping detection device.

[0013] In the test method, the current zero-off time and current change rate of the line current of the AFDD test main circuit within the power frequency cycle are changed by controlling the conduction angle of the bidirectional thyristor.

[0014] In the test method, the current of the AFDD test main circuit is adjusted by a load resistor to be used for AFDD tests at different rated current levels.

[0015] In the test method, the AFDD tripping detection device is a tungsten filament lamp, which is used to detect whether the AFDD test main circuit is disconnected, that is, whether the AFDD is tripped.

[0016] The high-frequency magnetic ring is used to couple the AFDD test main circuit and the high-frequency signal generator; when the high-frequency magnetic ring injects the high-frequency signal into the AFDD test main circuit, the AFDD test main circuit has both the fault arc current zero-break phenomenon and the fault arc high-frequency signal, thereby simulating the line fault arc current signal in the time domain and the high-frequency domain to detect the action characteristics of the AFDD line.

[0017] The high-frequency signal generator is coupled with the current restoration device; the current restoration device is connected to the host computer platform via the high-speed data acquisition card to form a current restoration system combined with high-frequency coupling; the host computer platform outputs the waveform signal required for the test project to the high-speed data acquisition card based on the typical fault arc current waveform database; the high-speed data acquisition card performs digital-to-analog conversion on the received waveform signal and outputs it to the current restoration device, and the current restoration module performs current power amplification on the signal output by the high-speed data acquisition card;

[0018] The typical fault arc current waveform database stores data on line current waveform distortion when a fault arc occurs in a distribution system. Typical features of the line current waveform include a flat current shoulder, a large current rise rate, and an increase in high-frequency components.

[0019] In the test method, the host computer controls the high-speed data card with Labview software, and uses different load current data of a typical fault arc current waveform database as a reference as the signal analog input of a current restoration module; the current restoration module performs current power amplification processing on the analog output signal of the high-speed data acquisition card to achieve a 1:1 output of its output current and a given current signal.

[0020] The present invention utilizes power electronic devices to construct a test circuit, can simulate the fault arc current characteristics appearing in the line, and realizes rapid testing of AFDD, which has a broad market space for the research and development of AFDD and the research of portable AFDD testing devices.

[0021] The present invention proposes a current restoration system combined with high-frequency coupling, which is composed of a host computer platform, a high-speed data acquisition card, a current restoration device and a high-frequency signal generator, and can simulate various typical load fault arc currents specified in the national standard GB / T 31143 in test experiments.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. A signal injection fault arc protection device test method is proposed. The high-frequency characteristics of the arc are injected into the AFDD circuit by using a magnetic ring to test the AFDD action characteristics and provide a reference for AFDD testing.

[0024] 2. Design a high-frequency signal injected fault arc protection device test circuit, which includes a main circuit of a bidirectional thyristor and a resistor in series, a broadband high-frequency signal generation circuit and a high-frequency magnetic ring. The test circuit is low-cost and easy to test, especially suitable for production line product testing, laying the foundation for the development of portable AFDD test equipment.

[0025] 3. A new type of current restoration system combined with high-frequency injection method is designed. The upper computer software and current restoration module are combined to realize the restoration of different fault arc current waveforms, and the arc current high-frequency characteristics are injected into the current restoration module to jointly simulate the arc current signal characteristics and test the action characteristics of the AFDD. Compared with the traditional method of testing the AFDD by building a fault arc test platform and using a physical arc starting device, the current restoration system combined with the high-frequency injection method of the present invention has a short test cycle, higher efficiency, small footprint, low investment cost, and repeatable use. It has practical significance for the action characteristic test of AFDD products, the internal fault arc detection and identification algorithm correction, and the hardware circuit modification, and has great significance in the field of fault arc protection electrical testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0027] Attached Figure 1 It is a schematic diagram of the principle of the present invention;

[0028] Attached Figure 2 It is a schematic diagram of the principle of the current restoration system combined with high frequency coupling of the present invention;

[0029] Attached Figure 3 It is a schematic diagram of the current restoration process of the current restoration system. DETAILED DESCRIPTION

[0030] As shown in the figure, a method for testing the characteristics of an arc fault protection appliance is used to test an AFDD circuit that carries an arc fault protection function. The testing method includes an AFDD circuit and a high-frequency signal generator coupled by a high-frequency magnetic ring; the AFDD circuit passes through the center of the high-frequency magnetic ring, and the signal output end of the high-frequency signal generator is connected to a coil surrounding the high-frequency magnetic ring. After the high-frequency signal output by the high-frequency signal generator is injected into the high-frequency magnetic ring, the AFDD circuit is tested by simulating an arc environment with an electromagnetic induction effect.

[0031] The high-frequency signal is generated by a high-frequency signal generator and is a high-frequency characteristic signal of a fault arc with a frequency range of 6-14 MHz, and is used as a high-frequency characteristic quantity of the arc current in the test method.

[0032] The high-frequency signal generator includes a high-frequency signal source and a power amplifier for amplifying the power of the high-frequency signal of the high-frequency signal source.

[0033] The AFDD circuit is a main circuit for AFDD testing, and includes a bidirectional thyristor, a load resistor and an AFDD tripping detection device.

[0034] In the test method, the current zero-off time and current change rate of the line current of the AFDD test main circuit within the power frequency cycle are changed by controlling the conduction angle of the bidirectional thyristor.

[0035] In the test method, the current of the AFDD test main circuit is adjusted by a load resistor to be used for AFDD tests at different rated current levels.

[0036] In the test method, the AFDD tripping detection device is a tungsten filament lamp, which is used to detect whether the AFDD test main circuit is disconnected, that is, whether the AFDD is tripped.

[0037] The high-frequency magnetic ring is used to couple the AFDD test main circuit and the high-frequency signal generator; when the high-frequency magnetic ring injects the high-frequency signal into the AFDD test main circuit, the AFDD test main circuit has both the fault arc current zero-break phenomenon and the fault arc high-frequency signal, thereby simulating the line fault arc current signal in the time domain and the high-frequency domain to detect the action characteristics of the AFDD line.

[0038] The high-frequency signal generator is coupled with the current restoration device; the current restoration device is connected to the host computer platform via the high-speed data acquisition card to form a current restoration system combined with high-frequency coupling; the host computer platform outputs the waveform signal required for the test project to the high-speed data acquisition card based on the typical fault arc current waveform database; the high-speed data acquisition card performs digital-to-analog conversion on the received waveform signal and outputs it to the current restoration device, and the current restoration module performs current power amplification on the signal output by the high-speed data acquisition card;

[0039] The typical fault arc current waveform database stores data on line current waveform distortion when a fault arc occurs in a distribution system. Typical features of the line current waveform include a flat current shoulder, a large current rise rate, and an increase in high-frequency components.

[0040] In the test method, the host computer controls the high-speed data card with Labview software, and uses different load current data of a typical fault arc current waveform database as a reference as the signal analog input of a current restoration module; the current restoration module performs current power amplification processing on the analog output signal of the high-speed data acquisition card to achieve a 1:1 output of its output current and a given current signal.

[0041] Example:

[0042] In this example, the AFDD action characteristic test is achieved by injecting the arc current characteristic signal into the line containing the AFDD. An AFDD test circuit with high-frequency signal injection is designed. By controlling the conduction angle of the bidirectional thyristor in the test circuit, the time domain zero-break phenomenon of the arc current is simulated. The high-frequency signal generator simulates the high-frequency domain characteristic signal of the arc current, and uses a high-frequency magnetic ring to inject the high-frequency characteristic signal into the test circuit. The time domain and high-frequency domain arc current characteristic signals are simulated in the AFDD line to test the action characteristics of the AFDD. In view of the diverse load background stipulated in the national standard, a current restoration system combined with the high-frequency injection method is further proposed. The waveforms of various fault arc currents are restored by the current restoration module, and the high-frequency characteristic signals of the arc current are injected into the current restoration module to achieve the restoration of the characteristics of various fault arc current signals, which can meet the action characteristic test of the AFDD under different test loads. The specific implementation method is as follows:

[0043] A signal generator is used to generate a high-frequency signal of 6-14MHz, and the power is amplified by a power amplifier. The signal is used as the high-frequency characteristic of the arc current. A high-frequency magnetic ring is wrapped around the coil for several turns, and the ends of the coil are connected to the high-frequency signal after power amplification. The circuit containing the AFDD passes through the center of the high-frequency magnetic ring, and the circuit containing the AFDD is coupled to the signal generator through the high-frequency magnetic ring. According to the principle of electromagnetic induction, the high-frequency signal generated by the signal generator is injected into the circuit containing the AFDD through the magnetic ring. Therefore, the test effect of detecting the action characteristics of the AFDD is achieved.

[0044] Since the zero-break phenomenon waveform of the arc current simulated by the bidirectional thyristor and the resistor series branch is single, but the national standard GB / T 31143 stipulates a variety of AFDD test loads, a current restoration system combined with high-frequency coupling is designed. The system consists of a host computer platform, a high-speed data acquisition card, a current restoration device and a high-frequency signal generator. The host computer platform outputs the waveform based on the typical fault arc current waveform database, and can select the signal type, amplitude, time length, etc. according to the test items. The high-speed data acquisition card realizes the digital-to-analog conversion and output functions. The current restoration module amplifies the current power of the signal output by the high-speed data acquisition card to achieve a 1:1 output of the output current and the given current signal. The current restoration flow chart is as follows Figure 3 As shown. The high-frequency signal generator is used to generate a high-frequency signal of the fault arc current, and the high-frequency signal is injected into the current restoration module using a high-frequency magnetic ring to simulate the fault arc current characteristics in the circuit. A variety of fault arc current restorations are achieved, and the current can be used for AFDD action characteristic testing.

Claims

1. A method for testing the characteristics of an arc fault protection device, used to test an AFDD circuit carrying an arc fault protection function, characterized in that: The test method comprises an AFDD circuit and a high-frequency signal generator coupled by a high-frequency magnetic ring; the AFDD circuit passes through the center of the high-frequency magnetic ring, the signal output end of the high-frequency signal generator is connected to a coil surrounding the high-frequency magnetic ring, and after the high-frequency signal outputted by the generator is injected into the high-frequency magnetic ring, the AFDD circuit is tested by simulating an arc environment by electromagnetic induction effect; The high-frequency magnetic ring is used to couple the AFDD test main circuit with the high-frequency signal generator; when the high-frequency magnetic ring injects the high-frequency signal into the AFDD test main circuit, the AFDD test main circuit has both the fault arc current zero-break phenomenon and the fault arc high-frequency signal, thereby simulating the line fault arc current signal in the time domain and the high-frequency domain to detect the action characteristics of the AFDD line; The high-frequency signal generator is coupled with the current restoration device for signal coupling; the current restoration device is connected to the host computer platform via a high-speed data acquisition card to form a current restoration system combined with high-frequency coupling; The host computer platform outputs the waveform signal required for the test project to the high-speed data acquisition card based on the typical fault arc current waveform database; the high-speed data acquisition card performs digital-to-analog conversion on the received waveform signal and outputs it to the current restoration device, and the current restoration module performs current power amplification on the signal output by the high-speed data acquisition card; The typical fault arc current waveform database stores data on the distortion of the line current waveform when a fault arc occurs in the distribution system. The typical characteristics of the line current waveform include a flat current shoulder, a large current rise rate, and an increase in high-frequency components. In the test method, the host computer controls the high-speed data card with Labview software, and uses different load current data of a typical fault arc current waveform database as a reference as the signal analog input of a current restoration module; the current restoration module performs current power amplification processing on the analog output signal of the high-speed data acquisition card to achieve a 1:1 output of its output current and a given current signal.

2. A method for testing characteristics of an arc fault protection device according to claim 1, characterized in that: The high-frequency signal is generated by a high-frequency signal generator and is a high-frequency characteristic signal of a fault arc, and is used as a high-frequency characteristic quantity of the arc current in the test method.

3. A method for testing characteristics of an arc fault protection device according to claim 2, characterized in that: The high-frequency signal generator includes a high-frequency signal source and a power amplifier for amplifying the power of the high-frequency signal of the high-frequency signal source.

4. A method for testing characteristics of an arc fault protection device according to claim 1, characterized in that: The AFDD circuit is a main circuit for AFDD testing, and includes a bidirectional thyristor, a load resistor and an AFDD tripping detection device.

5. A method for testing characteristics of an arc fault protection device according to claim 4, characterized in that: In the test method, the current zero-off time and current change rate of the line current of the AFDD test main circuit within the power frequency cycle are changed by controlling the conduction angle of the bidirectional thyristor.

6. A method for testing characteristics of an arc fault protection device according to claim 4, characterized in that: In the test method, the current of the AFDD test main circuit is adjusted by a load resistor to be used for AFDD tests at different rated current levels.

7. A method for testing characteristics of an arc fault protection device according to claim 4, characterized in that: In the test method, the AFDD tripping detection device is a tungsten filament lamp, which is used to detect whether the AFDD test main circuit is disconnected, that is, whether the AFDD is tripped.

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