Circuit breaker current sag test system and detection method

Abstract

The invention relates to a breaker current sag test system and a detection method. The breaker current sag test system comprises a man-machine interaction module, a central processing module, a signal acquisition module, a voltage regulation module, a voltage transformation module and a loop switching module. The man-machine interaction module is in communication connection with the central processing module, the output end of the central processing module is connected with the voltage regulating module and the loop switching module, the voltage regulating module is electrically connected with the loop switching module and the voltage transformation module, and the loop switching module is electrically connected with the voltage transformation module; the output end of the voltage transformation module is connected with the signal acquisition module, the signal acquisition module comprises a current sensor and a voltage sensor, and the output ends of the current sensor and the voltage sensor are connected with the input end of the central processing module; the central processing module is used for collecting sensing signals of the acquisition module and adjusting working parameters and working states of the voltage adjusting module and the loop switching module according to test parameters input by the man-machine interaction module. The special equipment for the current sag test does not need to be additionally equipped with a load and is convenient to use.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of low-voltage switchgear inspection and detection, and particularly relates to a circuit breaker current dip test system and a detection method. BACKGROUND

[0002] As a mechanical switchgear, the circuit breaker can not only connect, carry and break the current under normal circuit conditions, but also connect, carry for a certain time and break the current under specified abnormal circuit conditions (such as short circuit), and plays a vital protective role in the power system.

[0003] To ensure that the performance and quality of the circuit breaker meet the standards, GB / T14048.2-2020 makes clear provisions for the requirements of the circuit breaker in type tests such as temperature rise test and short-circuit breaking capacity test. In addition to the conventional type tests, additional verification tests are required for overcurrent protection circuit breakers with electronic devices. The anti-interference test-current dip is one of the key tests, which requires the test product to be tested under specified current and test time conditions to test the performance stability of the circuit breaker under current dip conditions.

[0004] However, there are few devices on the market that are specifically used to directly carry out the current dip test. In most cases, the related test needs to use the voltage dip test device and additionally match the load system to indirectly complete the current dip test. This indirect test method not only has high cost, but also has redundant system composition and complicated operation, which is not conducive to improving the test efficiency and reducing the test cost, and is difficult to meet the actual needs of the circuit breaker inspection and detection field. SUMMARY

[0005] In order to solve the problems that the existing circuit breaker current dip test does not have a special device, and the voltage dip device system is redundant for current dip test operation, a circuit breaker current dip test system and a detection method are provided, which do not need to additionally match the load system to realize the current dip test through the man-machine interaction module, the central processing module, the signal acquisition module, the voltage regulation module, the voltage transformation module and the loop switching module.

[0006] In order to achieve the above purpose, the first aspect of the present application provides a circuit breaker current dip test system, which comprises a man-machine interaction module, a central processing module, a signal acquisition module, a voltage regulation module, a voltage transformation module and a loop switching module.

[0007] The man-machine interaction module and the central processing module are in communication connection, the output end of the central processing module is connected with the voltage regulation module and the loop switching module respectively, the voltage regulation module is electrically connected with the loop switching module and the voltage transformation module, and the loop switching module is electrically connected with the voltage transformation module.

[0008] The output end of the voltage transformation module is connected with a signal acquisition module, the signal acquisition module comprises a current sensor and a voltage sensor, and the output ends of the current sensor and the voltage sensor are connected with the input end of the central processing module;

[0009] The central processing module is used for collecting the sensing signals of the acquisition module, and adjusting the working parameters and working states of the voltage regulation module and the loop switching module according to the test parameters input by the human-computer interaction module.

[0010] Further, the voltage regulation module comprises a coarse voltage regulator and a fine voltage regulator, the coarse voltage regulator comprises voltage input ends L21 and L22 and output ends L31 and LX1, the voltage input ends L21 and L22 of the coarse voltage regulator are connected with a power supply;

[0011] The fine voltage regulator comprises voltage input ends L41 and L42 and output ends L32 and LX2 and a transformer, the voltage input ends L41 and L42 of the fine voltage regulator are connected with the power supply, the output ends L32 and LX2 of the fine voltage regulator are connected with the primary side of the transformer, the secondary side of the transformer is connected with the output end LX1 of the coarse voltage regulator, and the other end of the secondary side of the transformer is connected with the voltage transformation module;

[0012] The output end L31 of the coarse voltage regulator is connected with the loop switching module;

[0013] The current output by the coarse voltage regulator is directly output through the output ends L31 and LX1, and the current output by the fine voltage regulator is output after primary voltage regulation through the output ends L32 and LX2 and secondary voltage regulation through the transformer.

[0014] The output end LX1 of the coarse voltage regulator and the secondary side of the transformer are connected in series as the output voltage of the voltage regulation module.

[0015] The voltage regulation module is divided into the coarse voltage regulator and the fine voltage regulator, the coarse voltage regulator can quickly approach the target value of the voltage, shorten the time consumption of voltage regulation, and adapt to the demand of quickly establishing a basic voltage in the initial stage of the test; the fine voltage regulator further reduces the voltage deviation through the double regulation of primary voltage regulation and secondary voltage regulation of the transformer, in combination with the series connection design with the output end of the coarse voltage regulator, ensures that the output voltage accurately matches the test demand, and solves the contradiction between low precision and low efficiency when a single voltage regulator is quickly regulated.

[0016] The output ends of the coarse voltage regulator and the fine voltage regulator form the final output voltage through series connection, the voltage regulation actions of the two can be mutually compensated, if there is a slight deviation in the coarse voltage, the fine voltage can be corrected in real time, so that the fluctuation range of the output voltage of the voltage regulation module is extremely small, a foundation is laid for the subsequent voltage transformation module to output stable test current, and the test data deviation caused by voltage fluctuation is reduced.

[0017] Further, the loop switching module comprises a first branch, a second branch and a third branch which are connected in parallel and have the same structure.

[0018] The first branch, the second branch and the third branch each comprise a thyristor and a fuse, the thyristor and the fuse are connected in series, the other side of the thyristor is electrically connected to a voltage regulating module, the other end of the fuse is electrically connected to a voltage transformation module, and the control end of the thyristor is electrically connected to a central processing module.

[0019] The central processing module controls the conduction of the first branch, the second branch and the third branch in pairs, and the output voltage after combination is U1, U2 and U3.

[0020] Through the design of three parallel branches with the same structure, the central processing module can control any two branches to conduct and combine to output U1, U2 and U3, without the need of additional voltage regulating components, so that multi-grade voltage output can be realized, the demand of different voltage corresponding to different temporary drop currents in the test can be met, and the hardware structure of voltage switching is simplified.

[0021] Further, the voltage transformation module comprises a multi-tap transformer, the primary side of the multi-tap transformer is connected to the switching module and the voltage regulating module respectively, and the secondary side of the multi-tap transformer is provided with two pairs of output terminals with different ranges.

[0022] The output voltages of U1, U2 and U3 after the multi-tap transformer are U 01 , U 02 and U 03 respectively.

[0023] The primary side of the tap transformer can be connected to different branches (corresponding to U1, U2 and U3) of the switching module, and in combination with the voltage transformation function of the transformer, multi-grade currents matching U01, U02 and U03 can be output, the test demand of different specifications of circuit breakers can be met, and the universality of the system is improved.

[0024] The voltage transformation module has two pairs of output terminals (HL1, COM and HL2, COM), and is provided with two sensors with different ranges and accuracies, so as to improve the current measurement accuracy in the output range of 50-800A.

[0025] Further, the human-computer interaction module comprises an HMI module, the central processing module comprises a PLC controller, and the PLC controller is in communication connection with the HMI module.

[0026] The second aspect of the present application proposes a detection method of a circuit breaker current temporary drop test system, comprising:

[0027] Step 1: According to the specification parameters of the circuit breaker test product and the test standard requirements, select two-phase series connection, three-phase series connection or three-phase connection, and reliably connect the circuit breaker test product to be tested to the test circuit;

[0028] Step 2: input test parameters through the man-machine interaction module, the test parameters including setting current value Tr, sinusoidal current period T, and temporary drop test current I, temporary drop time Δt and total test time t set according to test requirements D z ;

[0029] Step 3: the central processing module transmits the collected voltage and current data to the central processing module, and the central processing module calculates the fixed resistance R of the test circuit based on Ohm's law, and reversely obtains the required circuit target voltage value according to the expected initial test current and the fixed resistance R;

[0030] Step 4: based on the target voltage value, the central processing module controls the action of the coarse regulator, and adjusts the circuit voltage to the range close to the target voltage by changing the turns ratio of the winding inside the coarse regulator or the position of the carbon brush. After the coarse adjustment is completed, the central processing module switches to the fine adjustment mode, and controls the fine regulator to make the output of the voltage regulation module consistent with the target voltage value through two times of voltage regulation;

[0031] Step 5: the central processing module controls the circuit switching module to work, so that the circuit breaker sample works at the set current, and the central processing module monitors the working state of the circuit breaker sample in real time through the signal acquisition module;

[0032] Step 6: when the preset temporary drop trigger time is reached, the central processing module sends a current temporary drop instruction to the circuit switching module, and records the temporary drop time Δt of the circuit breaker sample after the current temporary drop under different conditions;

[0033] When the preset temporary drop time Δt is reached, the central processing module sends a current recovery instruction to the circuit switching module, and records the current application time.

[0034] Step 7: the current temporary drop instruction and the current recovery instruction of step 6 are repeated in a cycle until the total test time t is reached z to terminate the test.

[0035] Further, it further includes step 8: the central processing module records the circuit voltage change curve, the output current change curve and the circuit breaker sample tripping state;

[0036] If the circuit breaker sample does not trip in all test periods, it is determined that the circuit breaker sample passes the current temporary drop test; if the circuit breaker sample trips in any test, it is determined that the circuit breaker sample does not pass the test.

[0037] ​By recording the loop voltage change curve, the output current change curve, the parameter change in the test process can be intuitively restored, and the success or failure of the test can be determined without relying on the single result of "whether tripping"; at the same time, the determination standard of "all cycles are qualified, and any tripping is unqualified" is clear, there is no subjective determination space, and the determination results of different test samples are consistent and fair.

[0038] Further, the total test time t in step 2 z is 3-4 times of the maximum tripping time corresponding to 2 times of the current setting value.

[0039] Further, step 4 specifically comprises:

[0040] The variable ratio relationship between the input voltage and the output voltage is shown in formulas (1)-(2):

[0041]

[0042] U1, U2 and U3 remain unchanged during the test, only the on-off state of the thyristor (601) is controlled by the central processing module (2) to switch the input end, so as to realize the switching of the output current.

[0043] During the test, U1, U2 and U3 remain unchanged, and the output current switching can be realized only by the on-off of the thyristor, so as to reduce the number of actions of the voltage regulating module and reduce the energy loss; at the same time, the millisecond level on-off speed of the thyristor can ensure that the current is switched within 1ms, which meets the time requirement of "fast response to current dip" in the test, and improves the test efficiency.

[0044] Through the above technical solutions, the application has the following beneficial effects:

[0045] The application comprises a man-machine interaction module, a central processing module, a signal acquisition module, a voltage regulating module, a voltage transformation module and a loop switching module. The man-machine interaction module communicates with the central processing module and synchronizes data, and is used for man-machine interaction on site. The central processing module is used for collecting and processing interactive data and sensing signals, and executing instructions. The signal acquisition module is used for acquiring and monitoring loop voltage and current. The voltage regulating module is connected with an input power supply, and adjusts the loop voltage through primary voltage transformation. The voltage transformation module is connected with the loop switching module, and adjusts the output side voltage through secondary voltage transformation, so as to adjust the test current on the output side. The loop switching module is connected with the voltage regulating module, and is used for protecting the test equipment in the case of loop short circuit fault and overcurrent, and changing the output current value by switching the secondary voltage transformation ratio. The test system provided by the application realizes the circuit breaker current dip test through multiple voltage transformation and loop switching, is simple and easy to use, has low cost, and does not need an additional load system and manual operation. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 This is a schematic diagram of the structure of a circuit breaker current sag test system according to the present invention;

[0047] Figure 2 This is a circuit diagram of a circuit breaker current sag test system according to the present invention;

[0048] Figure 3 This is a flowchart of the detection method of the circuit breaker current sag test system of the present invention;

[0049] Figure 4 This is an experimental schematic diagram of a circuit breaker current sag test system according to the present invention.

[0050] The attached diagrams are numbered as follows: 1 is the human-computer interaction module, 2 is the central processing module, 3 is the signal acquisition module, 4 is the voltage regulation module, 5 is the transformer module, 6 is the circuit switching module, 401 is the coarse voltage regulator, 402 is the fine voltage regulator, 403 is the transformer, 501 is the multi-tap transformer, 601 is the thyristor, and 602 is the fuse. Detailed Implementation

[0051] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0052] Example 1

[0053] like Figures 1-4 As shown, a circuit breaker current sag test system includes a human-machine interaction module 1, a central processing module 2, a signal acquisition module 3, a voltage regulation module 4, a transformer module 5, and a circuit switching module 6.

[0054] The human-machine interaction module 1 and the central processing module 2 are communicatively connected. The output terminal of the central processing module 2 is connected to the voltage regulation module 4 and the circuit switching module 6 respectively. The voltage regulation module 4 is electrically connected to the circuit switching module 6 and the transformer module 5. The circuit switching module 6 is electrically connected to the transformer module 5.

[0055] The output terminal of the transformer module 5 is connected to the signal acquisition module 3. The signal acquisition module 3 includes a current sensor and a voltage sensor. The output terminals of the current sensor and the voltage sensor are both connected to the input terminal of the central processing module 2.

[0056] The central processing module 2 is used to collect the sensor signals from the acquisition module, and to adjust the working parameters and working status of the voltage regulation module 4 and the loop switching module 6 according to the test parameters input by the human-machine interaction module 1.

[0057] The voltage regulating module 4 comprises a coarse voltage regulator 401 and a fine voltage regulator 402, the coarse voltage regulator 401 comprises voltage input ends L21 and L22 and output ends L31 and LX1, the voltage input ends L21 and L22 of the coarse voltage regulator 401 are connected to a power supply;

[0058] The fine voltage regulator 402 comprises voltage input ends L41 and L42 and output ends L32 and LX2 and a transformer 403, the voltage input ends L41 and L42 of the fine voltage regulator 402 are connected to the power supply, the output ends L32 and LX2 of the fine voltage regulator 402 are connected to a primary side of the transformer 403, a secondary side of the transformer 403 is connected to the output end LX1 of the coarse voltage regulator 401, and the other end of the secondary side of the transformer 403 is connected to a voltage transformation module 5;

[0059] The output end L31 of the coarse voltage regulator 401 is connected to a loop switching module 6;

[0060] The current output by the coarse voltage regulator 401 is directly output through the output ends L31 and LX1, and the current output by the fine voltage regulator 402 is first regulated through the output ends L32 and LX2 and then secondly regulated through the transformer 403;

[0061] The output end LX1 of the coarse voltage regulator 401 and the secondary side of the transformer 403 are connected in series as an output voltage of the voltage regulating module 4.

[0062] The loop switching module 6 comprises a first branch, a second branch and a third branch which are connected in parallel and have the same structure;

[0063] The first branch, the second branch and the third branch each comprise a thyristor 601 and a fuse 602, the thyristor 601 and the fuse 602 are connected in series, the other side of the thyristor 601 is electrically connected to the voltage regulating module 4, the other end of the fuse 602 is electrically connected to the voltage transformation module 5, and the control end of the thyristor 601 is electrically connected to the central processing module 2;

[0064] The central processing module 2 controls the first branch, the second branch and the third branch to be conductive two by two, and the output voltage after combination is U1, U2 and U3.

[0065] The thyristors 601 and the fuses 602 in the three branches are marked as D1-D3 and RF1-RF3, the output of the first branch is marked as L33, the output of the second branch is marked as L34, and the output of the third branch is marked as L35.

[0066] The voltage transformation module 5 comprises a multi-tap transformer 501, a primary side of the multi-tap transformer 501 is connected to the switching module and the voltage regulating module 4 respectively, and a secondary side of the multi-tap transformer 501 is provided with two pairs of output ends with different ranges;

[0067] U1, U2 and U3 are respectively U01, U02 and U03 after the multi-tap transformer 501.

[0068] The current range output by the transformer module back end is 50-800A.

[0069] The human-computer interaction module 1 comprises an HMI module, and the central processing module 2 comprises a PLC controller, which is in communication connection with the HMI module.

[0070] A detection method of a circuit breaker current dip test system, comprising:

[0071] Step 1: according to the specification parameters of the circuit breaker test product and the test standard requirements, select the two-phase pole series connection, three-phase pole series connection or three-phase pole connection mode, and reliably connect the circuit breaker test product to be tested to the test loop;

[0072] Step 2: input the test parameters through the human-computer interaction module 1, the test parameters including the setting current value Ir, the sinusoidal current period T, and the dip test current I D , the dip time Δt and the total test time t z set according to the test requirements;

[0073] Step 3: the central processing module 2 transmits the collected voltage and current data to the central processing module 2, and the central processing module 2 calculates the fixed resistance R of the test loop based on Ohm's law, and reversely obtains the required loop target voltage value according to the expected initial test current and the fixed resistance R;

[0074] Step 4: based on the target voltage value, the central processing module 2 controls the coarse adjustment regulator 401 to act, and adjusts the loop voltage to the range close to the target voltage by changing the turns ratio of the winding inside the coarse adjustment regulator 401 or the carbon brush position, after the coarse adjustment is completed, the central processing module 2 switches to the fine adjustment mode, and controls the fine adjustment regulator 402 to make the output of the voltage regulation module 4 consistent with the target voltage value through twice voltage regulation;

[0075] Step 5: the central processing module 2 controls the loop switching module 6 to work, so that the circuit breaker test product works under the set current, and the central processing module 2 monitors the working state of the circuit breaker test product in real time through the signal acquisition module 3;

[0076] Step 6: when the preset dip trigger time is reached, the central processing module 2 sends a current dip instruction to the loop switching module 6, and records the dip time Δt of the circuit breaker test product after the current dip under different conditions;

[0077] When the preset dip time Δt is reached, the central processing module 2 sends a current recovery instruction to the loop switching module 6, and records the current application time.

[0078] Step 7: The current dip instruction and the current recovery instruction of step 6 are repeated in a cycle until the total test time t is reached z The test is terminated.

[0079] Step 8: The central processing module 2 records the loop voltage change curve, the output current change curve and the circuit breaker test sample tripping state;

[0080] If the circuit breaker test sample does not trip in all test periods, it is determined that the circuit breaker test sample passes the current dip test; if the circuit breaker test sample trips in any test, it is determined that the circuit breaker test sample does not pass the test.

[0081] The total test time t of step 2 z It is 3-4 times of the maximum tripping time corresponding to 2 times of the current setting value.

[0082] Step 4 specifically comprises:

[0083] The variable ratio relationship between the input voltage and the output voltage is shown in formulas 1-2:

[0084]

[0085] U1, U2 and U3 remain unchanged during the test, and only the central processing module 2 controls the loop switching module 6 to switch the on-off state of the thyristor 601, changes the input end connected, and then realizes the switching of the output current.

[0086] Embodiment 2

[0087] The operation of the circuit breaker current dip test system and the detection method of the application is illustrated by experiments:

[0088] Table 1: Current dip test parameters

[0089]

[0090]

[0091] As shown in Table 1 and the attached Figure 4 , the setting current value I r for the test is set by the man-machine interaction module 1, and the test system will automatically adjust the input test current to 0.9I r (see Figure 4 ). First, the current loop voltage and current are collected by the signal acquisition module 3, and the loop resistance R is calculated. Then, the required voltage is calculated according to the loop resistance and the expected current, and the loop voltage is adjusted to the given value by the voltage regulator.

[0092] In the process of voltage regulation, first by PLC control AC motor through coarse regulator 401 to adjust the loop voltage to close to the expected voltage, and then through the fine regulator 402 to accurately adjust the voltage. (That is, the primary voltage regulation is mainly used after the test sample is connected, the loop voltage is adjusted according to the loop resistance, and the output test current 0.9I r )

[0093] In the test, when the output current is 0.9Ir, only D3 is closed, and D1 and D2 are disconnected. At this time, it is assumed that the output voltage has been adjusted to Uo, that is, the input voltage of L35, L36 is Ui. At this time, When the input voltage is adjusted, it is not adjusted, and only the on-off state of the thyristors D1-D3 is switched to switch the on-off branch to adjust the output current. Therefore, U i = U o1 = U o2 = U o3 .

[0094] Because When only D2 is closed and D1 and D3 are disconnected, the output current When only D1 is closed and D2 and D3 are disconnected, the output current

[0095] During the test, the test system will automatically perform the tests numbered 1-11 in Table 1 in sequence, a total of 11 tests, and the temporary current and temporary time of each test are according to the parameters in Table 1. The total test time of each test is between 3 times and 4 times of the maximum trip time corresponding to 2 times the current setting value or 10 minutes, and the minimum value between the two is taken. And recorded as t z During the test, the circuit breaker test sample should not trip at 0.9I r .

[0096] When the first test is performed, see Figure 4 and Table 1, the normal working current is 0.9I r , the temporary current I D = 0, that is, the circuit breaker test sample works at 0.9I r current, and then all the loops are disconnected through the loop switching module 6, the output current is 0 (that is, the temporary current I D = 0) within 1ms, and the circuit breaker test sample works at I D = 0 current for Δt time; After that, the loop state is restored through the loop switching module, the test output current is restored to 0.9I r , and the circuit breaker test sample works at 0.9I r current for 4Δt time;

[0097] Then the circuit breaker test piece in 0.9I r And 0 current switching work until the total test time meets t z Requirements, determine whether the circuit breaker test piece is qualified. The second to fifth tests are similar, but Δt is different.

[0098] When performing the sixth to eighth tests, the circuit will be switched by the circuit switching module 6, and the circuit breaker test piece will be switched between 0.9I r Current and 0.4I r Current switching work, if the output test current is adjusted repeatedly by adjusting the circuit voltage through the voltage regulator, it is not only energy-consuming and time-consuming, but also difficult to meet the condition of completing current switching within 1ms, therefore, on the one hand, the thyristor 601 is used in the circuit switching module 6 to quickly respond to the on-off of the circuit, and on the other hand, the input winding of the multi-tap transformer 501 is switched by controlling the circuit on-off, the output voltage ratio is changed, so that the secondary output voltage is changed, and the output current is changed under the condition that the voltage on the primary side of the variable voltage module 5 is unchanged.

[0099] When performing the ninth to eleventh tests, the circuit will be switched by the circuit switching module 6, and the circuit breaker test piece will be switched between 0.9I r Current and 0.7I r Current switching work. Since the test current of the circuit breaker test piece is 0.9I r , 0.7I r And 0.4I r , there is a relationship of 9:7:4, so for the multi-tap transformer 501, the multi-path voltage ratio should also have a relationship of 9:7:4.

[0100] In summary, if the circuit breaker test piece does not trip during all test periods, it is determined that the circuit breaker test piece passes the current transient test; if the circuit breaker test piece trips in any test, it is determined that the circuit breaker test piece does not pass the test.

[0101] The above-described embodiments are only preferred embodiments of the present application and do not limit the scope of the application, so equivalent changes or modifications made in accordance with the structure, features and principles described in the scope of the present application are included in the scope of the application.

Claims

1. A circuit breaker current sag test system, characterized in that, It includes a human-computer interaction module (1), a central processing module (2), a signal acquisition module (3), a voltage regulation module (4), a transformer module (5), and a circuit switching module (6); The human-computer interaction module (1) and the central processing module (2) are connected in communication. The output of the central processing module (2) is connected to the voltage regulation module (4) and the circuit switching module (6) respectively. The voltage regulation module (4) is electrically connected to the circuit switching module (6) and the transformer module (5). The circuit switching module (6) is electrically connected to the transformer module (5). The output terminal of the transformer module (5) is connected to the signal acquisition module (3). The signal acquisition module (3) includes a current sensor and a voltage sensor. The output terminals of the current sensor and the voltage sensor are both connected to the input terminal of the central processing module (2). The central processing module (2) is used to collect the sensor signals from the acquisition module, and to adjust the working parameters and working status of the voltage regulation module (4) and the loop switching module (6) according to the test parameters input by the human-machine interaction module (1).

2. The circuit breaker current sag test system according to claim 1, characterized in that, The voltage regulating module (4) includes a coarse voltage regulator (401) and a fine voltage regulator (402). The coarse voltage regulator (401) includes voltage input terminals L21 and L22 and output terminals L31 and LX1. The voltage input terminals L21 and L22 of the coarse voltage regulator (401) are connected to the power supply. The fine-tuning voltage regulator (402) includes voltage input terminals L41 and L42, output terminals L32 and LX2, and a transformer (403). The voltage input terminals L41 and L42 of the fine-tuning voltage regulator (402) are connected to a power supply. The output terminals L32 and LX2 of the fine-tuning voltage regulator (402) are connected to the primary side of the transformer (403). The secondary side of the transformer (403) is connected to the output terminal LX1 of the coarse voltage regulator (401). The other end of the secondary side of the transformer (403) is connected to the transformer module (5). The output terminal L31 of the coarse voltage regulator (401) is connected to the loop switching module (6); The current output by the coarse voltage regulator (401) after voltage regulation is directly output through the output terminals L31 and LX1. The current output by the fine voltage regulator (402) after voltage regulation is first regulated through the output terminals L32 and LX2 and then regulated secondly through the transformer (403). The output terminal LX1 of the coarse voltage regulator (401) is connected in series with the secondary side of the transformer (403) as the output voltage of the voltage regulating module (4).

3. The circuit breaker current sag test system according to claim 1, characterized in that, The loop switching module (6) includes a first branch, a second branch, and a third branch that are connected in parallel and have the same structure; The first branch, the second branch and the third branch each include a thyristor (601) and a fuse (602). The thyristor (601) and the fuse (602) are connected in series. The other side of the thyristor (601) is electrically connected to the voltage regulating module (4), the other end of the fuse (602) is electrically connected to the transformer module (5), and the control end of the thyristor (601) is electrically connected to the central processing module (2). The central processing module (2) controls the first branch, the second branch and the third branch to be connected in pairs, and the combined output voltages are U1, U2 and U3.

4. The circuit breaker current sag test system according to claim 3, characterized in that, The transformer module (5) includes a multi-tap transformer (501). The primary side of the multi-tap transformer (501) is connected to the switching module and the voltage regulating module (4) respectively. The secondary side of the multi-tap transformer (501) is provided with two pairs of output terminals with different ranges. The output voltages of U1, U2, and U3 after passing through the multi-tap transformer (501) are respectively U 01 U 02 and U 03 .

5. The circuit breaker current sag test system according to claim 1, characterized in that, The human-machine interaction module (1) includes an HMI module, and the central processing module (2) includes a PLC controller, which is communicatively connected to the HMI module.

6. A testing method for a circuit breaker current sag test system according to any one of claims 1-5, characterized in that, include: Step 1: Based on the specifications and test standard requirements of the circuit breaker test specimen, select the two-phase series, three-phase series, or three-phase connection method to reliably connect the circuit breaker test specimen to the test circuit. Step 2: Input the test parameters through the human-computer interaction module (1). The test parameters include the set current value Ir, the sinusoidal current period T, and the sag test current ID, sag time Δt, and total test time t set according to the test requirements. z ; Step 3: The central processing module (2) transmits the collected voltage and current data to the central processing module (2). The central processing module (2) calculates the fixed resistance R of the test circuit based on Ohm's law. Based on the expected initial test current and the fixed resistance R, the required target voltage value of the circuit is obtained by reverse calculation. Step 4: Based on the target voltage value, the central processing module (2) controls the operation of the coarse voltage regulator (401). By changing the winding turns ratio or carbon brush position inside the coarse voltage regulator (401), the circuit voltage is quickly adjusted to a range close to the target voltage. After the coarse adjustment is completed, the central processing module (2) switches to the fine adjustment mode and controls the fine voltage regulator (402) to adjust the voltage twice to make the output of the voltage regulating module (4) consistent with the target voltage value. Step 5: The central processing module (2) controls the circuit switching module (6) to work, so that the circuit breaker test object works under the set current. The central processing module (2) monitors the working status of the circuit breaker test object in real time through the signal acquisition module (3). Step 6: When the preset sag trigger time is reached, the central processing module (2) sends a current sag command to the loop switching module (6) and records the sag time Δt of the circuit breaker test sample after the current sag under different conditions; When the preset sag time Δt is reached, the central processing module (2) sends a current recovery command to the loop switching module (6) and records the current application time. Step 7: Repeat the current sag command and current recovery command from step 6 until the total test time t is reached. z The experiment was terminated.

7. The detection method of the circuit breaker current sag test system according to claim 1, characterized in that, It also includes step 8: the central processing module (2) records the circuit voltage change curve, the output current change curve and the tripping status of the circuit breaker test sample; If the circuit breaker test specimen does not trip during all test cycles, it is determined that the circuit breaker test specimen has passed the current sag test; if the circuit breaker test specimen trips during any test, it is determined that the circuit breaker test specimen has failed the test.

8. The detection method of the circuit breaker current sag test system according to claim 1, characterized in that, The total test time t mentioned in step 2 z This is 3 to 4 times the maximum tripping time corresponding to 2 times the current setting value.

9. The detection method of the circuit breaker current sag test system according to claim 1, characterized in that, Step 4 specifically includes: The transformation ratio between the input voltage and the output voltage is shown in formulas (1)-(2): U1, U2, and U3 remain unchanged during the test. The on / off state of the thyristor (601) is switched by the control loop switching module (6) through the central processing module (2), thereby changing the input terminal and thus realizing the switching of the output current.

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