A detection method for current limiting protector

Abstract

A detection method for a current limiting protector belongs to the technical field of detection of electrical and electronic emergency protectors, and includes the following steps: sampling a current limiting protector sample; first closing the air switch KS1 and connecting the power supply of the test equipment; closing the air switch KS2, connecting the sampling load network to the test distribution line, and the waveform sampling unit starts to collect the voltage waveform characteristics of the sampling load network; the phase control unit sends the voltage phase of the test distribution line to the host computer, and connects the short-circuit non-inductive power resistor to the distribution line; the current limiting protector sample detects that the current of the distribution line reaches the short-circuit protection setting value and cuts off the test distribution line; the host computer calculates the short-circuit protection time and the current limiting time. The present invention uses a thyristor phase control method, continuous voltage output, and after the short-circuit current is generated, the current limiting protector acts to disconnect the short-circuit current at any time, and the short-circuit protection time and the current limiting time can be measured.

Description

Technical Field

[0001] The invention belongs to the technical field of detection of electrical and electronic emergency protectors, and in particular relates to a detection method for a current limiting protector. Background Art

[0002] Electrical equipment installed in a distribution box on materials such as wood needs to have characteristics that avoid causing fires. If a high-current circuit breaker is installed in the distribution box, a disconnecting arc will be generated during the disconnection process, which will increase the risk of igniting the wood material and causing a fire. The current limiting protector has the characteristic of cutting off the distribution line without current, and is suitable for use in occasions with high fire risks. However, the current limiting protector needs to be tested to ensure its safety during operation. The existing current limiting protector detection method uses an existing thyristor trigger, which can only send a trigger signal at a preset phase angle to generate a short-circuit fault current, and cannot adjust the phase angle at all times. Therefore, the thyristor can only be triggered at a fixed phase in each current half cycle. If the tested current limiting protector does not disconnect the distribution line in the first half cycle, the short-circuit protection time and current limiting time of the current limiting protector cannot be measured.

[0003] like Figure 1A-1B The voltage waveform diagram of the test circuit in the prior art is shown as follows: Figure 1A It is a voltage input and thyristor drive voltage waveform diagram for testing the power distribution circuit in the prior art; Figure 1B The voltage output waveform diagram of the prior art test circuit. The thyristor trigger can only trigger the thyristor output at a fixed phase angle, that is, trigger at t1, t3, and t5. According to the requirements of GB17287.6 "Electrical Fire Monitoring System Part 6: Electrical Fire Current Limiting Protector" (Draft for Approval), the short-circuit current begins to be generated at t1. If the current limiting protector is activated to disconnect the short-circuit current during the time period t1 to t2, the short-circuit protection time and current limiting time can be collected. However, if the current limiting protector is activated to disconnect the short-circuit current during the time period t2 to t3, the short-circuit protection time and current limiting time cannot be collected because there is no output on the distribution line during this time period. Summary of the invention

[0004] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a detection method for a current limiting protector, which adopts a thyristor phase control method and continuous voltage output. After a short-circuit current is generated, the current limiting protector can be activated to disconnect the short-circuit current at any time, and the short-circuit protection time and the current limiting time can be measured.

[0005] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0006] A method for detecting a current limiting protector comprises the following steps:

[0007] 1) Sampling a current limiting protector sample using a driving and sampling device for detecting a current limiting protector, wherein the driving and sampling device for detecting a current limiting protector comprises first and second air switches, a test equipment power supply, a phase control unit, a waveform sampling unit, a sampling load network, an electronic switch and a short-circuit non-inductive power resistor;

[0008] 2) When conducting the short-circuit protection performance test, first close the first air switch, turn on the power of the test equipment, and the waveform sampling unit and phase control unit start to operate;

[0009] 3) Close the second air switch, the current limiting protector sample is in the on state, connect the sampling load network to the test distribution line, and the waveform sampling unit starts to collect the voltage waveform characteristics of the sampling load network;

[0010] 4) The phase control unit sends the voltage zero-crossing signal of the test distribution line to the MCU of the host computer, and the MCU of the host computer performs phase analysis and calculation and sends a control instruction to the phase control unit. The phase control unit controls the electronic switch to turn on at the preset phase of the first current half cycle, and triggers the electronic switch to turn on at the zero-crossing point of the subsequent current half cycle, connects the short-circuit non-inductive power resistor to the distribution line, and generates a current that meets the requirements;

[0011] 5) When the current-limiting protector sample detects that the current of the distribution line reaches the short-circuit protection setting value, it cuts off the test distribution line;

[0012] 6) The MCU of the host computer analyzes the collected waveform characteristics through the waveform sampling unit and calculates the short-circuit protection time and current limiting time.

[0013] Furthermore, the method also includes conducting an overload protection performance test, specifically: closing the second air switch and controlling the electronic switch to be turned on to generate a current of 120% of the rated current value, and the MCU of the host computer collects and analyzes the current signal of the distribution line, analyzes, calculates, and records the breaking time of the current limiting protector, and displays the results.

[0014] Furthermore, the method also includes performing a non-action performance test, specifically: closing the second air switch and controlling the electronic switch to be turned on to generate a current of 90% of the rated current value, and the MCU of the host computer collects and analyzes the current signal of the distribution line to analyze and record the status of the current limiting protector.

[0015] Furthermore, the connection structure of the first and second air switches in the driving and sampling equipment for detecting the current limiting protector, the test equipment power supply, the phase control unit, the waveform sampling unit, the sampling load network, the electronic switch and the short-circuit non-inductive power resistor is as follows: the test equipment power supply is connected to the main power supply through the first air switch; the current limiting protector to be tested is connected to the main power supply through the second air switch; the test equipment power supply supplies power to the waveform sampling unit and the phase control unit; the switching loop of the electronic switch is connected in series with the short-circuit non-inductive power resistor and then in parallel with the sampling load network, and then connected in series with the current limiting protector to be tested to the main power supply; the control end of the electronic switch is connected to the output signal of the phase control unit, and the phase control unit controls the on and off of the electronic switch; the on and off control signal output by the sampling load network to collect the sample is connected to the waveform sampling unit, and the output ends of the waveform sampling unit and the phase control unit are both connected to the host computer; the electronic switch is a fast bidirectional thyristor.

[0016] Furthermore, the method for determining the short-circuit protection time and the current limiting time includes: at time T1, the device generates a preset short-circuit current; at time T2, the current limiting protector starts to act; at time T3, the current limiting protector completes the current limiting protection, the short-circuit protection time is (T3-T1), and the current limiting protection time is (T3-T2);

[0017] Sampling starts from time T1, the sampling interval is Δt, the current conversion rate between two samples is Δi, and the current gradient grad(i) is used as the criterion for the current limiting protector to start operating.

[0018]

[0019] If the absolute value of the current gradient is greater than the limit value I for three consecutive times p , that is, |grad(i)|>I p It is judged that the current limiting protector starts to act, and the current sampling value i is less than the set value Iz, that is, i<I z , it is judged that the current limiting protector completes the current limiting action.

[0020] The beneficial effects of the present invention are as follows: the present invention provides a detection device and method for a current limiting protector, which adopts a thyristor phase control method, a continuous voltage output, and after a short-circuit current is generated, the current limiting protector is actuated to disconnect the short-circuit current at any time, and the short-circuit protection time and the current limiting time can be measured. The present invention makes up for the disadvantage of the prior art that when the current limiting protection action time exceeds half a cycle, it cannot be accurately measured, the measured time is more accurate, and the scope of application is also wider. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1A It is a voltage input and thyristor drive voltage waveform diagram for testing the power distribution circuit in the prior art;

[0022] Figure 1B It is a voltage output waveform diagram of a test circuit in the prior art;

[0023] Figure 2 This is a system block diagram of the drive and sampling equipment used to detect the current limiting protector of the present invention;

[0024] Figure 3 This is the current waveform after the current limiting protector is activated;

[0025] Figure 4 It is the circuit schematic diagram of the phase control unit;

[0026] Figure 5 It is the waveform diagram of the phase sampling control unit;

[0027] Figure 6 It is the circuit schematic diagram of the waveform sampling unit;

[0028] Figure 7 is a waveform diagram of a waveform sampling unit;

[0029] Figure 8 This is the schematic diagram of the thyristor drive circuit;

[0030] Fig.9A It is a voltage input and thyristor trigger signal waveform diagram of the test circuit of the present invention;

[0031] Fig. 9B This is a voltage output waveform diagram of the test circuit of the present invention. DETAILED DESCRIPTION

[0032] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0033] The national standard GB 14287.6 "Electrical Fire Monitoring System Part 6: Electrical Fire Limiting Current Protector" (draft for approval) stipulates the technical requirements for the short-circuit protection performance, overload protection performance, and non-operation performance of current limiting protectors.

[0034] Part 3.4 is the alarm performance, as follows:

[0035] 3.4.1 Short circuit protection performance

[0036] When the current I of the protected circuit is the alternating current shown in Formula 1, when the protected circuit is short-circuited at phase angles of 0° and 180°, the absolute value of the difference between the short-circuit protection action value of the protector and the short-circuit protection setting value should not be greater than 10% of the short-circuit protection setting value, the short-circuit protection time should not be greater than 5ms, and the current limiting time should not be greater than 150μs.

[0037] Note: Short-circuit protection time refers to the time from when a short circuit occurs in the protected circuit to when the protector completes the current limiting protection. Current limiting time refers to the time from when the protector starts to limit current to when the protector completes the current limiting protection.

[0038]

[0039] Where:

[0040] I——current of the protected circuit;

[0041] Is——short-circuit protection current setting value;

[0042] t——time interval.

[0043] 3.4.2 Overload protection performance

[0044] When the current value of the protected circuit reaches 120% of the rated current value of the protector, the protector should trigger the current limiting protection action within 3s to 60s.

[0045] 3.5 Non-action performance

[0046] When the current value of the protected circuit is not greater than 90% of the rated current of the protector, the protector should not trigger the current limiting protection action and should not issue an audible or visual alarm signal.

[0047] The invention is a driving and sampling device for detecting a current limiting protector, and is a sampling device developed for short-circuit protection performance, overload protection performance and non-action performance in a standard approval draft.

[0048] like Figure 2 As shown, it is a system block diagram of the current limiting protector sampling device of the present invention, including the first and second air switches KS1-KS2, the test equipment power supply, the phase control unit, the waveform sampling unit, the sampling load network, the electronic switch and the short-circuit non-inductive power resistor R, wherein the test equipment power supply is connected to the main power supply through the first air switch KS1; the current limiting protector to be tested is connected to the main power supply through the second air switch KS2; the test equipment power supply supplies power to the waveform sampling unit and the phase control unit; the switch loop of the electronic switch is connected in series with the short-circuit non-inductive power resistor R and then connected in parallel with the sampling load network, and then connected in series with the current limiting protector to be tested to the main power supply; the control end of the electronic switch is connected to the output signal of the phase control unit, and the phase control unit controls the on and off of the electronic switch; the on and off control signal output by the sampling load network to collect the sample is connected to the waveform sampling unit, and the output ends of the waveform sampling unit and the phase control unit are both connected to the host computer to obtain the short-circuit protection time and current limiting time of the sample; the electronic switch is a fast bidirectional thyristor.

[0049] The first air switch KS1 controls the on and off of the power supply of the test equipment; the second air switch KS2 controls the on and off of the test distribution line and plays a role in short-circuit protection. During the test, when the current-limiting protector sample cannot disconnect the distribution line as required, the second air switch KS2 will disconnect the test distribution line to prevent danger. The test equipment power supply supplies power to the waveform sampling unit and the phase control unit. The sampling load network is used to collect the waveform of the test distribution line and provide it to the waveform sampling unit. The phase control unit is used to collect the phase of the test distribution line, and control the conduction of the electronic switch at the specified phase angle according to the requirements of the standard, connect the short-circuit non-inductive power resistor to the test distribution line, and generate a current that meets the test requirements. The electronic switch uses a fast bidirectional thyristor.

[0050] When conducting a short-circuit protection performance test, first close the first air switch KS1, turn on the power of the test equipment, and the waveform sampling unit and the phase control unit start to operate; then close the second air switch KS2, at this time the current limiting protector sample is in the on state, connect the sampling load network to the test distribution line, and the waveform sampling unit starts to collect the voltage waveform characteristics of the sampling load network; the phase control unit collects the voltage phase of the test distribution line, and controls the electronic switch to turn on at the set phase angle, connects the short-circuit non-inductive power resistor to the distribution line, and generates a current that meets the requirements of formula (1); when the current limiting protector sample detects that the current of the distribution line reaches the short-circuit protection set value, it cuts off the test distribution line; the waveform sampling unit transmits the collected waveform characteristics of the sampling load network to the MCU of the host computer to obtain the short-circuit protection time and current limiting time of the sample.

[0051] When conducting the overload protection performance test, close the air switch KS2 and control the electronic switch to conduct, generate a current of 120% of the rated current value, and record the breaking time of the current limiting protector.

[0052] Perform the non-action performance, close the air switch KS2, and control the electronic switch to conduct, generate a current of 90% of the rated current value, and record the status of the current limiting protector.

[0053] Criteria for short-circuit protection time and current limiting time

[0054] like Figure 3 The figure shows the current waveform after the current limiting protector is activated. At time T1, the device generates a preset short-circuit current; at time T2, the current limiting protector starts to operate; at time T3, the current limiting protector completes the current limiting protection. The short-circuit protection time is (T3-T1), and the current limiting protection time is (T3-T2).

[0055] Sampling starts from time T1, the sampling interval is Δt, and the current conversion rate between two samplings is Δi. Figure 3In the figure, curve a is the waveform of the current after the current limiting protector is activated, and curve b is the waveform of the sinusoidal current. After the protector is activated, the rate of change of the current is much smaller than the conversion rate of the sinusoidal current. Therefore, the current gradient can be used as the criterion for the current limiting protector to start to operate.

[0056]

[0057] If the absolute value of the current gradient is greater than the limit value I for three consecutive times p , it is judged that the current limiting protector starts to act.

[0058] |grad(i)|>I p

[0059] If the sampling value of the current is less than the set value Iz, it is judged that the current limiting protector completes the current limiting action.

[0060] i<I z

[0061] like Figure 4 As shown in the figure, it is the schematic diagram of the phase control circuit. Diodes D8 and D9 are connected in parallel and then connected in series with resistors R12, R16, R15, and R13. The AC voltage passes through resistors R12 and R16, and then is connected to the non-inverting input terminal 3 and the inverting input terminal 2 of the operational amplifier U8A respectively. The connection point of resistors R13 and R15 is used as the reference ground for DC signals. The power supply pin 8 of the operational amplifier U8A is connected to the +5V power supply, and is connected to the filter capacitor C34 and then grounded. The output pin 1 of the operational amplifier is connected to resistors R14 and R17 and then grounded, and the connection point of resistors R14 and R17 is used as the phase sampling point.

[0062] Resistors R12, R16, R13, R15 and diodes D8, D9 form a square wave conversion circuit. The AC input voltage signal is converted into a square wave signal through the clamping effect of the diode and output to the in-phase input terminal 3 and the reverse input terminal 2 of U8 respectively. The phase of the in-phase input terminal 3 is the same as the phase of the AC input signal, and the phase of the reverse input terminal 2 is opposite to the phase of the AC input signal.

[0063] U8 is an LM358 voltage comparator op amp, powered by a +5V single power supply, forming a zero-crossing comparator. The output of the comparator is pin 1, which outputs a 3.3V square wave signal after being divided by resistors R14 and R17. The waveform of the phase sampling control circuit is shown in the figure below. Figure 5 As shown, a is the AC input signal, b is the 3.3V square wave output signal, c is the in-phase square wave input signal, and d is the reverse square wave input signal. The square wave signal is output to the PWM input pin of the MCU. The MCU uses the rising edge of the square wave as a trigger signal to start the timer, calculate the timing value of the timer according to the set phase, and output a high level to perform phase control.

[0064] like Figure 6 As shown in the figure, it is the schematic diagram of the waveform sampling unit circuit. The waveform sampling unit circuit mainly includes: voltage boost circuit and signal amplification processing circuit. The voltage boost circuit adopts the architecture of resistor voltage division and reverse proportional amplifier circuit. Resistor R19 and adjustable resistor are connected in series and connected to +5V power supply and -5V power supply respectively. The voltage signal after voltage division by resistor R19 and adjustable resistor R22 is connected to resistor R20 and then input to the inverting input terminal 2 of U9 op amp (OP07). The non-inverting input terminal 3 of U9 op amp is connected to resistor R23 and then grounded. The output terminal 6 of U9 op amp is connected to resistor R18 and then connected to the inverting input terminal 2 of op amp. The value of R19 is 510Ω, the adjustment range of R22 is 0~2kΩ, and the variation range of test point TP2 is: -5V~2.96V. U9 adopts the reverse proportional amplifier circuit, the values ​​of resistors R18 and R20 are both 10kΩ, and the amplification factor of op amp is -1. Therefore, the output of the voltage boost circuit (test point TP3) varies within the range U i1 It is: -2.96V~5V.

[0065] The signal amplification processing circuit adopts the architecture of resistor voltage division, voltage follower circuit and reverse proportional amplifier circuit. Input terminal P3 is used as the input terminal of AC220V 50Hz AC signal, resistors R24, R25, R26 and R27 are connected in series, and the connection point of resistors R25 and R26 is used as the voltage reference ground. The connection point of resistors R24 and R25 is connected to resistor R30 and then connected to the inverting input terminal 3 of op amp U10A. The output terminal 1 of the op amp is connected to the inverting input terminal 2. The positive and negative power supply pins 4 and 11 of the op amp are connected to capacitors C37 and C38 respectively and then grounded. After the output terminal 1 of op amp U10A is connected to resistor R31, it is connected to the inverting input terminal 6 of op amp U10B, and the non-inverting input terminal 5 of op amp U10B is connected to resistor R33 and then grounded. The output terminal 7 of op amp U10B is connected to resistor R28 and then connected to the inverting input terminal 6. The output pin 7 of the op amp U10B is connected to the resistor R32 and then to the inverting input pin 9 of the op amp U10C. The output pin 6 of the op amp U9 is connected to the resistor R21 and then to the inverting input pin 9 of the op amp U10C. The output pin 8 of the op amp U10C is connected to the resistor R29 and then to the inverting input pin 9 of the op amp U10C. The output pin 8 of the op amp U10C is connected to the non-inverting input pin 12 of the op amp U10D, and the output pin 14 of the op amp U10D is connected to the inverting input pin 13.

[0066] AC signal U i After input, the AC signal is divided by resistors R24, R25, R26 and R27 to become U i2 , AC signal U i2After passing through the input resistor R30, it enters the non-inverting input terminal of the U10A op amp (TL084). The op amp uses a voltage follower circuit, and the signal at the output point TP4 of the op amp is also U i2 .

[0067]

[0068]

[0069] TP4 signal U i1 After passing through the input resistor R31, it enters the inverting input terminal of the U10B op amp (TL084). The op amp uses a reverse proportional amplification circuit. The value of the resistor R28 is 7.5kΩ, and the value of R31 is 10kΩ. The signal at the output point TP5 of the op amp is U i3 .

[0070]

[0071] The output signal U of the voltage boost circuit i1 The output signal U of the signal amplifier circuit i3 After passing through resistors R21 and R32, they enter the inverting input terminal of the U10C op amp (TL084). The op amp uses an addition circuit, and the output of the op amp is U o .

[0072]

[0073] AC signal U o1 Entering the non-inverting input terminal of the U10D op amp (TL084), the op amp uses a voltage follower circuit, and the signal at the output point TP6 of the op amp is also U o .

[0074] The present invention uses a 3.3V MCU to collect voltage signals, so U i1 The voltage is adjusted to 1.92V, U o The output range is 0.765V~3.075V, and U o with U i The waveform of the waveform sampling unit is as follows: Figure 7 As shown, a is the input signal and b is the output signal.

[0075] Thyristor drive circuit such as Figure 8As shown, after the PWM control signal PWR_SCR_CTL is connected to the resistor R18, it is connected to the base of the NPN transistor Q6, and the emitter of the transistor Q6 is grounded. The 24V power supply is connected to the resistors R15 and R17 and then connected to the collector of the transistor Q6. The 24V power supply is connected to the source of the N-channel field effect transistor Q5, and the connection point of the resistors R15 and R17 is connected to the gate of Q5. The drain of Q5 is connected to the resistor R14 and then used as the power supply input 24V_SCR of the thyristor. The 24V_SCR is connected to the resistor R16 and then connected to the light-emitting diode LED2.

[0076] The control signal SCR_CTL of the thyristor is connected to the base of the NPN transistor Q2 and the PNP transistor Q4 after connecting to the resistor R11. 24V_SCR is connected to the collector of the transistor Q2, and the collector of the transistor Q2 is connected to the emitter of the transistor Q4, and the collector of the transistor Q4 is grounded. The connection point between the emitter of the transistor Q2 and the collector of the transistor Q4 is connected to the resistor R12, and then connected to the cathode of the voltage regulator tube DZ4, one end of the resistor R13, and the gate of the N-channel field effect transistor Q3. The anode of the voltage regulator tube DZ4 is grounded, and the other end of the resistor R13 is grounded. 24V_SCR is connected to the drain of Q3 after connecting to the resistor R10. The drain of Q3 leads to the 24VPWM control signal PWM_24V_OUT-.

[0077] 24V_SCR is connected to capacitors C2 and C3 and then grounded. 24V_SCR is connected to the cathode of the voltage regulator tube DZ2, and the anode of DZ2 is connected to capacitor C4 and then connected to the drain of the N-channel field effect tube Q1. The source of Q1 is grounded, and the gate is connected to resistor R8 and then connected to PWM_24V_OUT-. PWM_24V_OUT- is connected to resistor R9 and then connected to the light-emitting diode LED1. Resistors R4 and R7 are connected in series and then connected in parallel with capacitor C4. 24V_SCR is connected to capacitor C1 and then connected to resistor R5, and then connected to the drain of Q1. Pin 1 of the primary coil of the high-frequency transformer T1 is connected to 24V_SCR, and pin 2 is connected to the drain of Q1. Pin 3 of the secondary coil of the high-frequency transformer is connected to the anode of the diode VD1, and the cathode of VD1 is connected to the cathode of the voltage regulator tube DZ1. The anode of DZ1 is connected to pin 4 of the secondary coil of the transformer T1, and is also connected to resistor R2 and then connected to pin 2 of terminal P1. The cathode of the diode VD1 is connected to the resistor R1 and then connected to the pin 2 of the terminal P1, and the cathode of VD1 is connected to the pin 1 of the terminal P1.

[0078] The present invention uses a high-frequency pulse transformer to trigger the thyristor and also has a power control function. When the thyristor needs to be triggered, the power control port PWR_SCR_CTL sends a high-level trigger signal, the transistor Q6 is turned on, the trigger MOS tube Q5 is turned on, and the 24V power supply provides a 24V voltage for the high-frequency pulse transformer.

[0079] At this time, the PWM signal is applied to drive transistors Q2 and Q4 through the SCR_CTL port to generate a 24V PWM output pulse. This pulse signal drives the MOS tube Q1 through the resistor R8 to generate a pulse signal that is output through the high-frequency pulse transformer T1 to drive the thyristor.

[0080] Fig.9A To test the voltage input of the power distribution circuit and the thyristor drive voltage waveform; Fig. 9B The voltage output waveform diagram of the test circuit of the present invention. The thyristor is triggered at t1, t2, and t3, and the voltage output is continuous. After the short-circuit current is generated at t1, the current-limiting protector can be operated to disconnect the short-circuit current at any time, and the short-circuit protection time and current-limiting time can be measured. The thyristor phase control method is adopted, and the voltage is continuously output. After the short-circuit current is generated, the current-limiting protector can be operated to disconnect the short-circuit current at any time, and the short-circuit protection time and current-limiting time can be measured.

[0081] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may alter, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A detection method for a current limiting protector, characterized in that: The steps include: 1) Sampling a current limiting protector sample using a driving and sampling device for detecting a current limiting protector, wherein the driving and sampling device for detecting a current limiting protector comprises first and second air switches (KS1-KS2), a test equipment power supply, a phase control unit, a waveform sampling unit, a sampling load network, an electronic switch and a short-circuit non-inductive power resistor (R); 2) When conducting the short-circuit protection performance test, first close the first air switch (KS1), turn on the power of the test equipment, and the waveform sampling unit and phase control unit start to operate; 3) Close the second air switch (KS2), the current limiting protector sample is in the on state, the sampling load network is connected to the test distribution line, and the waveform sampling unit starts to collect the voltage waveform characteristics of the sampling load network; 4) The phase control unit sends the voltage phase of the test distribution line to the MCU of the host computer, and the MCU of the host computer sends a control instruction to the phase control unit, and the phase control unit controls the electronic switch to turn on at the preset phase of the first current half cycle, and triggers the electronic switch to turn on at the zero crossing point of the subsequent current half cycle, connects the short-circuit non-inductive power resistor to the distribution line, and generates a current that meets the requirements; 5) When the current-limiting protector sample detects that the current of the distribution line reaches the short-circuit protection setting value, it cuts off the test distribution line; 6) The MCU of the host computer analyzes the collected waveform characteristics through the waveform sampling unit and calculates the short-circuit protection time and current limiting time.

2. A detection method for a current limiting protector according to claim 1, characterized in that: The method also includes conducting an overload protection performance test, specifically: closing the second air switch (KS2) and controlling the electronic switch to conduct when the voltage of the distribution line passes through zero, generating a current of 120% of the rated current value, and the MCU of the host computer collects and analyzes the current signal of the distribution line, analyzes, calculates, and records the breaking time of the current limiting protector, and displays the results.

3. A detection method for a current limiting protector according to claim 1, characterized in that: The method also includes performing a non-action performance test, specifically: closing the second air switch (KS2) and controlling the electronic switch to conduct when the voltage of the distribution line passes through zero, generating a current of 90% of the rated current value, and the MCU of the host computer collects and analyzes the current signal of the distribution line to analyze and record the status of the current limiting protector.

4. A detection method for a current limiting protector according to claim 1, characterized in that: The connection structure of the first and second air switches (KS1-KS2) in the driving and sampling equipment for detecting the current limiting protector, the power supply of the test equipment, the phase control unit, the waveform sampling unit, the sampling load network, the electronic switch and the short-circuit non-inductive power resistor (R) is as follows: the power supply of the test equipment is connected to the main power supply through the first air switch (KS1); the current limiting protector to be tested is connected to the main power supply through the second air switch (KS2); the power supply of the test equipment supplies power to the waveform sampling unit and the phase control unit; the switch loop of the electronic switch is connected in series with the short-circuit non-inductive power resistor (R) and then connected in parallel with the sampling load network, and then connected in series with the current limiting protector to be tested to the main power supply; the control end of the electronic switch is connected to the output signal of the phase control unit, and the phase control unit controls the on and off of the electronic switch; the on and off control signal output by the sampling load network to collect the sample is connected to the waveform sampling unit, and the output ends of the waveform sampling unit and the phase control unit are both connected to the host computer; the electronic switch is a fast bidirectional thyristor.

5. The detection method of a current limiting protector according to claim 1, characterized in that: The method for determining the short-circuit protection time and the current limiting time includes: at time T1, the device generates a preset short-circuit current; at time T2, the current limiting protector starts to act; at time T3, the current limiting protector completes the current limiting protection, the short-circuit protection time is (T3-T1), and the current limiting protection time is (T3-T2); Sampling starts from time T1, the sampling interval is Δt, the current conversion rate between two samples is Δi, and the current gradient grad(i) is used as the criterion for the current limiting protector to start operating. If the absolute value of the current gradient is greater than the limit value I for three consecutive times p , that is, |grad(i)|>I p , it is judged that the current limiting protector starts to act, and the current sampling value i is less than the set value Iz, that is, i<I z , it is judged that the current limiting protector completes the current limiting action.

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