Test method of low-voltage motor microcomputer protection device

Abstract

The invention discloses a test method of a low-voltage motor microcomputer protection device, which utilizes the characteristic that a current transformer configured on the low-voltage motor microcomputer protection device has the same secondary side rated current under the conditions of the same model and different primary side rated current. A method of replacing an original current transformer with a test current transformer with a relatively small rated current at a primary side is adopted, so that a protection function test performed by a three-phase test current I1 needing a large current is changed into a protection function test performed by a three-phase test current I2 after a stable small current is changed, and the effect of small and stable test current is achieved; the problems of unsmooth voltage regulation, unstable output current and unbalanced three-phase current caused by the fact that the three-phase test current is subjected to current rising by an existing current rising transformer method are solved, and the tedious wire winding link of an existing winding method can be omitted or reduced. The device has the advantages of small electric energy loss, good test quality and accuracy, simple test process, high test efficiency and low test cost.

Description

Test Method for Microcomputer Protection Device of Low-Voltage Motor Technical Field

[0001] The present invention relates to a microcomputer protection device for low-voltage motors, and specifically to a test method for a microcomputer protection device of low-voltage motors. Background Art

[0002] The debugging of the microcomputer protection device for low-voltage motors is a crucial link to ensure its normal operation and reliable protection. Currently, there are three traditional test methods for the 380V microcomputer protection device of low-voltage motors in petrochemical plants: the current boosting transformer method, the winding method, and the method of changing set parameters

[0003] Method 1: Current boosting transformer method: Use a three-phase autotransformer to control the output current of three current boosting transformers for testing. The disadvantages are high energy consumption, inability to meet the test current requirements due to the influence of on-site power supply conditions, uneven voltage regulation, unstable output current, slow calibration speed caused by unbalanced three-phase currents, and difficulty in ensuring calibration accuracy

[0004] Method 2: Winding method: Since the three-phase simultaneous output current of the relay protection tester is generally around 30A, for test items with a protection setting current above 30A, it is necessary to increase the number of turns of the primary coil to change the current transformer ratio to reduce the required test current. The disadvantage is that the center aperture of the precision current transformer supporting the microcomputer protection device for low-voltage motors is relatively small, making it difficult to pass the test wire and resulting in low test efficiency

[0005] Method 3: Method of changing set parameters: Similarly, due to the limited three-phase simultaneous output current of the relay protection tester, the setting current value of the microcomputer protection device for low-voltage motors is deliberately reduced to reduce the required test current. After the test, the setting value is changed back to the original value. The disadvantages are that it cannot reflect the protection action characteristics under the true operating current, can only check the functions of the microcomputer protection device, cannot test the accuracy of the true protection setting value, and cannot fill out the test report according to the setting value Summary of the Invention

[0006] The technical problem to be solved by the present invention is: to provide a test method for a microcomputer protection device of low-voltage motors to solve the problems existing in the existing test methods: the current boosting transformer method requires boosting the test current, resulting in high power consumption, slow test speed, and difficulty in ensuring accuracy; the winding method has the problem that when a large test current is required, it is necessary to wind a coil with a large number of turns, and the center aperture of the current transformer may be relatively small and difficult to meet

[0007] To solve the above technical problems, the technical solution adopted by the present invention is as follows

[0008] A test method for a low-voltage motor microprocessor protection device includes: applying a three-phase test current to the primary side of a current transformer using a three-phase test current source, causing the secondary side of the current transformer to output a secondary side current to the three-phase sampling port of the low-voltage motor microprocessor protection device under test, and causing the protection action output port of the low-voltage motor microprocessor protection device under test to generate a corresponding protection action signal based on the secondary side current; and receiving the protection action signal using a switch quantity monitoring device to perform a protection function test on the low-voltage motor microprocessor protection device under test.

[0009] Its features are:

[0010] Referring to Figure 1, when the protection function test requires the three-phase test current I1 applied to the primary side of the current transformer to be below the upper limit of the current that the three-phase test current source can provide, the original current transformer originally configured in the microcomputer protection device of the low-voltage motor under test is used as the current transformer to directly test the microcomputer protection device of the low-voltage motor under test.

[0011] Referring to Figure 2, when the protection function test requires the three-phase test current I1 applied to the primary side of the current transformer to be greater than the upper limit of the current that the three-phase test current source can provide, while keeping other parameters of the microprocessor protection device of the low-voltage motor under test unchanged, a test current transformer with the same model as the original current transformer but with a smaller primary side rated current is used as the current transformer. That is, the original current transformer on the microprocessor protection device of the low-voltage motor under test is removed and replaced with the test current transformer. Furthermore, the three-phase test current source is changed to apply a modified three-phase test current I2=I1÷(CTI1 / CTI2) to the primary side of the test current transformer, where CTI1 is the primary side rated current of the original current transformer and CTI2 is the primary side rated current of the test current transformer.

[0012] Therefore, the working principle of this invention is as follows:

[0013] Through long-term research on the current transformers configured in low-voltage motor microprocessor protection devices, the following characteristics have been found: First, the current transformers configured in low-voltage motor microprocessor protection devices of the same brand are semi-electronic devices. They have multiple specifications with different primary-side rated currents within the same model. Furthermore, the secondary side wiring method of current transformers of the same model but different primary-side rated currents is the same as that of the current sampling port of the low-voltage motor microprocessor protection device of the same brand. And when the primary side is input with the primary-side rated current, the current transformers of the same model but different primary-side rated currents supply the same current to the low-voltage motor microprocessor protection device. The secondary rated currents output from the current sampling port of the protection device are all equal and are small currents in the milliampere range. For example, when a current transformer with a primary rated current of 10A inputs a three-phase current of 10A to its primary side, its secondary rated current outputs 5mA. Similarly, when another current transformer of the same model with a primary rated current of 100A inputs a three-phase current of 100A to its primary side, its secondary rated current will also output 5mA. Secondly, when a certain percentage of the primary rated current is input to the primary side of the current transformer, its secondary rated current outputs the same percentage.

[0014] This invention utilizes the unique characteristics of the current transformer configured in the microprocessor-based protection device for low-voltage motors. When the protection function test requires a three-phase test current I1 applied to the primary side of the current transformer that is greater than the upper limit of the current provided by the three-phase test current source, it eliminates the need for a current-increasing transformer to increase the output current of the three-phase test current source, as is done in the prior art. Instead, it replaces the original current transformer with a test current transformer of the same model but with a smaller rated primary current, and changes the three-phase test current source to apply a modified three-phase test current I2 = I1 ÷ (CTI1 / CTI2) to the primary side of the test current transformer. The modified three-phase test current I2 is less than the upper limit of the current that the three-phase test current source can provide, so that the three-phase test current source can meet the implementation conditions of the protection function test. When the modified three-phase test current I2 is input into the primary side of the test current transformer, the secondary side current output is equal to the secondary side current output when the original current transformer is input into the primary side of the three-phase test current I1. As a result, the microprocessor protection device of the low-voltage motor under test makes the same protection judgment and produces the same protection action because the secondary side current input to the current sampling port is the same. Thus, the protection function test of the microprocessor protection device of the low-voltage motor under test can be carried out normally.

[0015] Therefore, this invention utilizes the characteristic that the current transformer configured in the microcomputer protection device for low-voltage motors has the same secondary rated current under the same model but different primary rated currents. By replacing the original current transformer with a test current transformer with a smaller primary rated current, the protection function test, which requires a large three-phase test current I1, is changed to be performed by a stable, small-current modified three-phase test current I2. This achieves the effect of a small and stable test current, avoiding the problems of uneven voltage regulation, unstable output current, and unbalanced three-phase current caused by the existing current-increasing transformer method for increasing the three-phase test current. It can also omit or reduce the cumbersome wire winding process of the existing winding method, and has the advantages of low power loss, good test quality and accuracy, simple test process, high test efficiency, and low test cost.

[0016] The wiring method between the current transformer, the three-phase test current source, the microprocessor protection device for the low-voltage motor under test, and the switch quantity monitoring equipment is as follows:

[0017] The A-phase terminal, B-phase terminal, and C-phase terminal of the three-phase test current source are respectively connected to one end of the primary A-phase current line, the primary B-phase current line, and the primary C-phase current line. The other end of the primary A-phase current line, the primary B-phase current line, and the primary C-phase current line passes through the primary A-phase wire hole, the primary B-phase wire hole, and the primary C-phase wire hole of the current transformer respectively in the direction of current inflow, and is then connected to one end of the primary neutral wire current line. The other end of the primary neutral wire current line is connected to the neutral terminal of the three-phase test current source.

[0018] The secondary side A-phase current line, secondary side B-phase current line, secondary side C-phase current line, and secondary side neutral current line of the current transformer are respectively connected to the A-phase current sampling port, B-phase current sampling port, C-phase current sampling port, and neutral current sampling port of the microprocessor protection device for the low-voltage motor under test, and, ;

[0019] The protection action output port of the microprocessor protection device for the low-voltage motor under test is connected to the switch input port of the switch monitoring device to transmit the protection action signal.

[0020] Preferably, the secondary side A-phase current line, secondary side B-phase current line, secondary side C-phase current line, and secondary side neutral current line belong to the same shielded wire, and the shielding layer of the shielded wire is grounded.

[0021] Preferably, when using the test current transformer with the smallest obtainable primary-side rated current CTI2 as the current transformer, if the calculated modified three-phase test current I2 = I1 ÷ (CTI1 / CTI2) is below the upper limit of the current that the three-phase test current source can provide, then the primary-side A-phase current line, primary-side B-phase current line, and primary-side C-phase current line directly pass through the primary-side A-phase wire hole, primary-side B-phase wire hole, and primary-side C-phase wire hole of the current transformer; otherwise, by adjusting the number of turns of the primary-side A-phase current line, primary-side B-phase current line, and primary-side C-phase current line on the current transformer to N, and adjusting the current value of the modified three-phase test current I2 to I1 ÷ (CTI1 / CTI2) ÷ N, so that it is below the upper limit of the current that the three-phase test current source can provide.

[0022] Preferably, the test current transformer is obtained by removing it from the spare circuit of the microprocessor protection device for the low-voltage motor under test, and is reinstalled back into the spare circuit after the protection function test is completed.

[0023] Preferably, the three-phase test current source and the switch quantity monitoring equipment are integrated into a relay protection tester to reduce the implementation cost of the test method.

[0024] In addition, the present invention is not limited to testing of microprocessor protection devices for low-voltage motors, but can also be used for testing current-related protection functions of microprocessor protection devices for feeder circuits.

[0025] As a preferred embodiment of the present invention, the protection function test includes, but is not limited to, one or more of the following tests: instantaneous overcurrent protection test, thermal overload protection test, zero-sequence overcurrent protection test, residual current protection test, locked rotor protection test, and phase current imbalance protection test.

[0026] Preferably, the protection function test is performed according to the following steps:

[0027] Step S1: Set the target protection function that the microcomputer protection device of the low-voltage motor under test needs to be tested, set the three-phase test current I1 required by the target protection function to be applied to the primary side of the current transformer, and calculate the changed three-phase test current I2.

[0028] Step S2: Exit or disable all functions of the microprocessor protection device for the low-voltage motor under test, except for the target protection function;

[0029] Step S3: Perform a protection action sensitivity test, including:

[0030] Step S3-1: Temporarily set the action time of the microprocessor protection device for the low-voltage motor under test to 0 seconds, that is, the protection action is executed immediately after the corresponding fault is detected.

[0031] Step S3-2: Apply 95% I2 of the three-phase test current to the primary side of the current transformer using a three-phase test current source, and gradually increase the three-phase test current in increments of 0.01A until the switch monitoring device receives the protection action signal, that is, when the microprocessor protection device of the tested low-voltage motor is triggered to perform the protection action, record the three-phase test current at this time as the action current.

[0032] Step S3-3: Repeat step S3-2 at least five times and calculate the average operating current.

[0033] Step S3-4: Determine whether the operating current error exceeds the preset operating current error threshold. If so, determine that the sensitivity of the microcomputer protection device for the tested low-voltage motor is unqualified in performing the protection action; otherwise, determine that it is qualified.

[0034] Wherein, the operating current error = (average operating current - operating current design setpoint) ÷ operating current design setpoint.

[0035] Preferably, the protection function test further includes:

[0036] Step S4: Perform a protection action speed test, including:

[0037] Step S4-1: Set the action time of the microprocessor protection device for the low-voltage motor under test to the design value of the action time.

[0038] Step S4-2: Apply a three-phase test current of 105%I2 to the primary side of the current transformer using a three-phase test current source, and receive the protection action signal through the switch quantity monitoring device to determine the actual action time of the microcomputer protection device of the tested low-voltage motor to perform the protection action.

[0039] Step S4-3: Repeat step S4-2 at least five times and calculate the average actual action time.

[0040] Step S4-4: Determine whether the action time error exceeds the preset action time error threshold. If so, determine that the speed at which the microcomputer protection device of the tested low-voltage motor performs the protection action is unqualified; otherwise, determine that it is qualified.

[0041] Wherein, motion time error = (average actual motion time - motion time design setpoint) ÷ motion time design setpoint.

[0042] Preferably, the protection function test further includes:

[0043] Step S5: Perform a reliability test on the protection action, including:

[0044] Step S5-1: Directly apply 95% of I2 of the three-phase test current to the primary side of the current transformer using a three-phase test current source. Repeat this process three times. If the microprocessor protection device of the low-voltage motor under test does not perform any protection action, then condition one is satisfied.

[0045] Step S5-2: Apply 105%I2 of the three-phase test current directly to the primary side of the current transformer using a three-phase test current source. Repeat this process three times. If the microprocessor protection device of the tested low-voltage motor performs protection actions, then condition two is satisfied.

[0046] Step S5-3: If both conditions one and two are met, the reliability of the microprocessor protection device for the tested low-voltage motor is deemed qualified; otherwise, it is deemed unqualified.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] This invention utilizes the characteristic that current transformers configured in low-voltage motor microprocessor protection devices have the same secondary rated current under the same model but different primary rated currents. By replacing the original current transformer with a test current transformer with a smaller primary rated current, the protection function test, which requires a large three-phase test current I1, is changed to be performed by a stable, small-current modified three-phase test current I2. This achieves the effect of a small and stable test current, avoiding the problems of uneven voltage regulation, unstable output current, and unbalanced three-phase current caused by the existing current-increasing transformer method for increasing the three-phase test current. It also eliminates or reduces the cumbersome wire winding process of the existing winding method, and has the advantages of low power loss, good test quality and accuracy, simple test process, high test efficiency, and low test cost. Attached Figure Description

[0049] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments:

[0050] Figure 1 is a wiring diagram of the original current transformer, the three-phase test current source, the microcomputer protection device for the low-voltage motor under test, and the switch quantity monitoring device in this invention.

[0051] Figure 2 is a wiring diagram of the test current transformer, the three-phase test current source, the microcomputer protection device for the low-voltage motor under test, and the switch quantity monitoring device in this invention. Detailed Implementation

[0052] The present invention will now be described in detail with reference to the embodiments and accompanying drawings to help those skilled in the art better understand the inventive concept of the present invention. However, the scope of protection of the claims of the present invention is not limited to the following embodiments. For those skilled in the art, all other embodiments obtained without creative effort without departing from the inventive concept of the present invention are within the scope of protection of the present invention.

[0053] Example 1

[0054] As shown in Figures 1 and 2, the present invention discloses a test method for a low-voltage motor microprocessor protection device, comprising: applying a three-phase test current to the primary side of a current transformer using a three-phase test current source, causing the secondary side of the current transformer to output a secondary side current to the three-phase sampling port of the low-voltage motor microprocessor protection device under test, and causing the protection action output port of the low-voltage motor microprocessor protection device under test to generate a corresponding protection action signal based on the secondary side current; and receiving the protection action signal using a switch quantity monitoring device to perform a protection function test on the low-voltage motor microprocessor protection device under test.

[0055] Referring to Figure 1, when the protection function test requires the three-phase test current I1 applied to the primary side of the current transformer to be below the upper limit of the current that the three-phase test current source can provide, the original current transformer originally configured in the microcomputer protection device of the low-voltage motor under test is used as the current transformer to directly test the microcomputer protection device of the low-voltage motor under test.

[0056] Referring to Figure 2, when the protection function test requires the three-phase test current I1 applied to the primary side of the current transformer to be greater than the upper limit of the current that the three-phase test current source can provide, while keeping other parameters of the microprocessor protection device of the low-voltage motor under test unchanged, a test current transformer with the same model as the original current transformer but with a smaller primary side rated current is used as the current transformer. That is, the original current transformer on the microprocessor protection device of the low-voltage motor under test is removed and replaced with the test current transformer. Furthermore, the three-phase test current source is changed to apply a modified three-phase test current I2=I1÷(CTI1 / CTI2) to the primary side of the test current transformer, where CTI1 is the primary side rated current of the original current transformer and CTI2 is the primary side rated current of the test current transformer.

[0057] Therefore, the working principle of this invention is as follows:

[0058] Through long-term research on the current transformers configured in low-voltage motor microprocessor protection devices, the following characteristics have been found: First, the current transformers configured in low-voltage motor microprocessor protection devices of the same brand are semi-electronic devices. They have multiple specifications with different primary-side rated currents within the same model. Furthermore, the secondary side wiring method of current transformers of the same model but different primary-side rated currents is the same as that of the current sampling port of the low-voltage motor microprocessor protection device of the same brand. And when the primary side is input with the primary-side rated current, the current transformers of the same model but different primary-side rated currents supply the same current to the low-voltage motor microprocessor protection device. The secondary rated currents output from the current sampling port of the protection device are all equal and are small currents in the milliampere range. For example, when a current transformer with a primary rated current of 10A inputs a three-phase current of 10A to its primary side, its secondary rated current outputs 5mA. Similarly, when another current transformer of the same model with a primary rated current of 100A inputs a three-phase current of 100A to its primary side, its secondary rated current will also output 5mA. Secondly, when a certain percentage of the primary rated current is input to the primary side of the current transformer, its secondary rated current outputs the same percentage.

[0059] This invention utilizes the unique characteristics of the current transformer configured in the microprocessor-based protection device for low-voltage motors. When the protection function test requires a three-phase test current I1 applied to the primary side of the current transformer that is greater than the upper limit of the current provided by the three-phase test current source, it eliminates the need for a current-increasing transformer to increase the output current of the three-phase test current source, as is done in the prior art. Instead, it replaces the original current transformer with a test current transformer of the same model but with a smaller rated primary current, and changes the three-phase test current source to apply a modified three-phase test current I2 = I1 ÷ (CTI1 / CTI2) to the primary side of the test current transformer. The modified three-phase test current I2 is less than the upper limit of the current that the three-phase test current source can provide, so that the three-phase test current source can meet the implementation conditions of the protection function test. When the modified three-phase test current I2 is input into the primary side of the test current transformer, the secondary side current output is equal to the secondary side current output when the original current transformer is input into the primary side of the three-phase test current I1. As a result, the microprocessor protection device of the low-voltage motor under test makes the same protection judgment and produces the same protection action because the secondary side current input to the current sampling port is the same. Thus, the protection function test of the microprocessor protection device of the low-voltage motor under test can be carried out normally.

[0060] Therefore, this invention utilizes the characteristic that the current transformer configured in the microcomputer protection device for low-voltage motors has the same secondary rated current under the same model but different primary rated currents. By replacing the original current transformer with a test current transformer with a smaller primary rated current, the protection function test, which requires a large three-phase test current I1, is changed to be performed by a stable, small-current modified three-phase test current I2. This achieves the effect of a small and stable test current, avoiding the problems of uneven voltage regulation, unstable output current, and unbalanced three-phase current caused by the existing current-increasing transformer method for increasing the three-phase test current. It can also omit or reduce the cumbersome wire winding process of the existing winding method, and has the advantages of low power loss, good test quality and accuracy, simple test process, high test efficiency, and low test cost.

[0061] The above is the basic implementation method of this embodiment one, and further optimizations, improvements and limitations can be made based on this basic implementation method:

[0062] The wiring method between the current transformer, the three-phase test current source, the microprocessor protection device for the low-voltage motor under test, and the switch quantity monitoring equipment is as follows:

[0063] The A-phase terminal IA, B-phase terminal IB, and C-phase terminal IC of the three-phase test current source are respectively connected to the primary A-phase current line L. A Primary side B-phase current line L B Primary side C-phase current line L C One end, primary side A-phase current line L A Primary side B-phase current line L B Primary side C-phase current line L C The other end passes through the primary side A-phase wire hole A, primary side B-phase wire hole B, and primary side C-phase wire hole C of the current transformer in the direction of current inflow, and then connects with the primary side neutral current line L. N One end is connected to the primary side neutral current line L. N The other end is connected to the neutral terminal IN of the three-phase test current source;

[0064] Phase A current line l on the secondary side of the current transformer a Secondary side B-phase current line l b Secondary side C-phase current line l c Secondary side neutral current line l n Connect the A-phase current sampling port Ia, B-phase current sampling port Ib, C-phase current sampling port Ic, and neutral current sampling port In of the microprocessor protection device for the low-voltage motor under test, respectively.

[0065] The protection action output ports C1 and C2 of the microprocessor protection device for the low-voltage motor under test are connected to the switch input ports OA and +KM of the switch monitoring equipment to transmit the protection action signal.

[0066] Preferably: the secondary side A-phase current line l a Secondary side B-phase current line l b Secondary side C-phase current line l c Secondary side neutral current line l n Belonging to the same shielded wire, and the shielding layer of the shielded wire l p Grounding.

[0067] Preferably, when using the test current transformer with the smallest obtainable primary-side rated current CTI2 as the current transformer, if the calculated modified three-phase test current I2 = I1 ÷ (CTI1 / CTI2) is below the upper limit of the current that the three-phase test current source can provide, then the primary-side A-phase current line L... A Primary side B-phase current line L B Primary side C-phase current line L C The wires pass directly through the primary side A-phase wire hole A, primary side B-phase wire hole B, and primary side C-phase wire hole C of the current transformer; otherwise, they pass through the primary side A-phase current line L. A Primary side B-phase current line L B Primary side C-phase current line L C Adjust the number of winding turns on the current transformer to N, and adjust the current value of the changed three-phase test current I2 to I1÷(CTI1 / CTI2)÷N, so that it is below the upper limit of the current that the three-phase test current source can provide.

[0068] Preferably, the test current transformer is obtained by removing it from the spare circuit of the microprocessor protection device for the low-voltage motor under test, and is reinstalled back into the spare circuit after the protection function test is completed.

[0069] Preferably, the three-phase test current source and the switch quantity monitoring equipment are integrated into a relay protection tester to reduce the implementation cost of the test method.

[0070] In addition, the present invention is not limited to testing of microprocessor protection devices for low-voltage motors, but can also be used for testing current-related protection functions of microprocessor protection devices for feeder circuits.

[0071] Example 2

[0072] Based on the above embodiment one, this embodiment two also adopts the following preferred implementation method:

[0073] The protection function test includes, but is not limited to, one or more of the following tests: instantaneous overcurrent protection test, thermal overload protection test, zero-sequence overcurrent protection test, residual current protection test, locked rotor protection test, and phase current imbalance protection test.

[0074] The above is the basic implementation method of this embodiment two, and further optimizations, improvements and limitations can be made based on this basic implementation method:

[0075] Preferably, the protection function test is performed according to the following steps:

[0076] Step S1: Set the target protection function that the microcomputer protection device of the low-voltage motor under test needs to be tested, set the three-phase test current I1 required by the target protection function to be applied to the primary side of the current transformer, and calculate the changed three-phase test current I2.

[0077] Step S2: Exit or disable all functions of the microprocessor protection device for the low-voltage motor under test, except for the target protection function;

[0078] Step S3: Perform a protection action sensitivity test, including:

[0079] Step S3-1: Temporarily set the action time of the microprocessor protection device for the low-voltage motor under test to 0 seconds, that is, the protection action is executed immediately after the corresponding fault is detected.

[0080] Step S3-2: Apply 95% I2 of the three-phase test current to the primary side of the current transformer using a three-phase test current source, and gradually increase the three-phase test current in increments of 0.01A until the switch monitoring device receives the protection action signal, that is, when the microprocessor protection device of the tested low-voltage motor is triggered to perform the protection action, record the three-phase test current at this time as the action current.

[0081] Step S3-3: Repeat step S3-2 at least five times and calculate the average operating current.

[0082] Step S3-4: Determine whether the operating current error exceeds the preset operating current error threshold. If so, determine that the sensitivity of the microcomputer protection device for the tested low-voltage motor is unqualified in performing the protection action; otherwise, determine that it is qualified.

[0083] Wherein, the operating current error = (average operating current - operating current design setpoint) ÷ operating current design setpoint.

[0084] Preferably, the protection function test further includes:

[0085] Step S4: Perform a protection action speed test, including:

[0086] Step S4-1: Set the action time of the microprocessor protection device for the low-voltage motor under test to the design value of the action time.

[0087] Step S4-2: Apply a three-phase test current of 105%I2 to the primary side of the current transformer using a three-phase test current source, and receive the protection action signal through the switch quantity monitoring device to determine the actual action time of the microcomputer protection device of the tested low-voltage motor to perform the protection action.

[0088] Step S4-3: Repeat step S4-2 at least five times and calculate the average actual action time.

[0089] Step S4-4: Determine whether the action time error exceeds the preset action time error threshold. If so, determine that the speed at which the microcomputer protection device of the tested low-voltage motor performs the protection action is unqualified; otherwise, determine that it is qualified.

[0090] Wherein, motion time error = (average actual motion time - motion time design setpoint) ÷ motion time design setpoint.

[0091] Preferably, the protection function test further includes:

[0092] Step S5: Perform a reliability test on the protection action, including:

[0093] Step S5-1: Directly apply 95% of I2 of the three-phase test current to the primary side of the current transformer using a three-phase test current source. Repeat this process three times. If the microprocessor protection device of the low-voltage motor under test does not perform any protection action, then condition one is satisfied.

[0094] Step S5-2: Apply 105%I2 of the three-phase test current directly to the primary side of the current transformer using a three-phase test current source. Repeat this process three times. If the microprocessor protection device of the tested low-voltage motor performs protection actions, then condition two is satisfied.

[0095] Step S5-3: If both conditions one and two are met, the reliability of the microprocessor protection device for the tested low-voltage motor is deemed qualified; otherwise, it is deemed unqualified.

[0096] The following is an example of the test method of the present invention:

[0097] Load parameters of a product purification fan motor circuit in a substation of a petrochemical plant

[0098] Rated power: 132KW

[0099] Rated voltage: 380V

[0100] Rated current Irm: 250.7A

[0101] Motor microcomputer protection device: BDM100-M+ERAOC-300

[0102] Precision current transformer rated current: 300A

[0103] Protection settings:

[0104] 1) Thermal overload protection I eq / I e =5, action time t=8.5S;

[0105] 2) Instantaneous overcurrent protection setting Id2 = 10 × I rm =10×250.7=2507A, instantaneous delay t=0.3S, (According to the product manual: setpoint error ≤±5%, delay error: ≤±40ms);

[0106] 3) Zero-sequence overcurrent protection Id3 = 1 × Irm = 1 × 250.7 = 250.7A, action time t = 0.5S;

[0107] 4) Residual current protection Id4 = 0.3A, operating time t = 2S;

[0108] 5) Stall protection Ir = 1.5 × Irm = 1.5 × 250.7 = 376.05A, action time t = 3S;

[0109] 6) Phase current imbalance protection Iop=20%×Irm=20%×250.7=50.14A, action time t=10S.

[0110] Taking the instantaneous overcurrent protection test as an example: the rated current of the original current transformer is 300A, and a relay protection tester with a maximum three-phase output current of 30A is used as the test tool. After passing the visual inspection, insulation inspection, and power-on inspection.

[0111] 1) Set the parameters and protection settings;

[0112] 2) First, disable other protections and only enable instantaneous overcurrent protection;

[0113] 3) Instantaneous overcurrent protection setting: Id2=2507A, operating time t=0.3S;

[0114] 4) Borrow a current transformer of the same model with a rated current of 2A from the spare drawer. Temporarily set the operating time t to 0 seconds;

[0115] 5) Calculation of test current: I2 = I1 ÷ KK = (CTI1 / CTI2); K = 300 / 2 = 150; I2 = 2507 ÷ 150 = 16.71A;

[0116] 6) Operate the relay protection tester to output three-phase 16.71×95%=15.87A simultaneously, with a step size of 0.01A. Gradually increase the test current until the protection device operates. At this time, the test current is the instantaneous trip current of the protection device.

[0117] 7) At the same time, the motor microcomputer protection device displays 2508A, instantly issues a trip command and displays the instantaneous overcurrent protection action character.

[0118] 8) Repeat the test five times and calculate the average value;

[0119]

[0120] 9) The five-fold average = (I1+I2+I3+I4+I5)÷5 = (2508+2508+2508+2506.5+2508)÷5 = 2507.7A;

[0121] 10) Error = 0.048%.

[0122] Error less than ±5% is acceptable;

[0123] 11) Action time test: Set the action time t to the design value of 0.3 seconds, operate the relay protection tester to output a three-phase current of 16.72A, the motor microcomputer protection device displays 2508A, and after a delay of 0.3S, issue a trip command and display the instantaneous overcurrent protection action character.

[0124] 12) Measure the action time, repeat five times, and calculate the average value;

[0125]

[0126] 13) Delay error = average of five tests - design setpoint = 0.3232 - 0.3 = 0.0232S = 23.2ms;

[0127] The error is less than ±40ms, which is acceptable.

[0128] This invention is not limited to the specific embodiments described above. Based on the above content and in accordance with common technical knowledge and conventional methods in the field, without departing from the basic technical concept of this invention, this invention can also make other equivalent modifications, substitutions or alterations, all of which fall within the protection scope of this invention.

Claims

1. A test method for a low-voltage motor microprocessor protection device, comprising: A three-phase test current is applied to the primary side of a current transformer using a three-phase test current source, causing the secondary side of the current transformer to output a secondary side current to the three-phase sampling port of the microprocessor-based protection device for the low-voltage motor under test. This causes the protection action output port of the microprocessor-based protection device to generate a corresponding protection action signal based on the secondary side current. Furthermore, a switch quantity monitoring device receives the protection action signal to perform a protection function test on the microprocessor-based protection device for the low-voltage motor under test. The characteristic feature is that when the protection function test requires the three-phase test current I1 applied to the primary side of the current transformer to be below the upper limit of the current that the three-phase test current source can provide, the original configuration of the microprocessor-based protection device for the low-voltage motor under test is changed. A current transformer is used to directly test the microprocessor protection device of the low-voltage motor under test. When the protection function test requires the three-phase test current I1 applied to the primary side of the current transformer to be greater than the upper limit of the current that the three-phase test current source can provide, a test current transformer with the same model as the original current transformer but with a smaller primary side rated current is used as the current transformer. Furthermore, the three-phase test current source is changed to apply a modified three-phase test current I2=I1÷(CTI1 / CTI2) to the primary side of the test current transformer, where CTI1 is the primary side rated current of the original current transformer and CTI2 is the primary side rated current of the test current transformer.

2. The test method for the low-voltage motor microprocessor protection device according to claim 1, characterized in that: The wiring method between the current transformer, the three-phase test current source, the microprocessor protection device for the low-voltage motor under test, and the switch quantity monitoring equipment is as follows: the A-phase terminal (IA), B-phase terminal (IB), and C-phase terminal (IC) of the three-phase test current source are respectively connected to the primary side A-phase current line (L... A ), primary side B-phase current line (L) B ), primary side C-phase current line (L) C One end of the primary side A-phase current line (L) A ), primary side B-phase current line (L) B ), primary side C-phase current line (L) C The other end of the current transformer passes through the primary side A-phase wire hole (A), primary side B-phase wire hole (B), and primary side C-phase wire hole (C) respectively, in the direction of current inflow, and then connects with the primary side neutral current line (L). N Connect one end of the primary side neutral current line (L) N The other end is connected to the neutral terminal (IN) of the three-phase test current source; the secondary side A-phase current line (l) of the current transformer a ), secondary side B-phase current line (l b ), secondary side C-phase current line (l c ), secondary side neutral current line (l n Connect the A-phase current sampling port (Ia), B-phase current sampling port (Ib), C-phase current sampling port (Ic), and neutral current sampling port (In) of the microprocessor protection device for the low-voltage motor under test, respectively; connect the protection action output port of the microprocessor protection device for the low-voltage motor under test to the switch input port of the switch monitoring equipment.

3. The test method for the low-voltage motor microprocessor protection device according to claim 2, characterized in that: The secondary side A-phase current line (l) a ), secondary side B-phase current line (l b ), secondary side C-phase current line (l c ), secondary side neutral current line (l n ) belong to the same shielded wire, and the shielding layer of the shielded wire (l p Grounding.

4. The test method for the low-voltage motor microprocessor protection device according to claim 2, characterized in that: When using the test current transformer with the smallest obtainable primary-side rated current CTI2 as the current transformer, if the calculated modified three-phase test current I2 = I1 ÷ (CTI1 / CTI2) is below the upper limit of the current that the three-phase test current source can provide, then the primary-side A-phase current line (L A ), primary side B-phase current line (L) B ), primary side C-phase current line (L) C ) Directly pass through the primary side A-phase wire hole (A), primary side B-phase wire hole (B), and primary side C-phase wire hole (C) of the current transformer; otherwise, pass through the primary side A-phase current line (L A ), primary side B-phase current line (L) B ), primary side C-phase current line (L) C Adjust the number of winding turns on the current transformer to N, and adjust the current value of the changed three-phase test current I2 to I1÷(CTI1 / CTI2)÷N, so that it is below the upper limit of the current that the three-phase test current source can provide.

5. The test method for the low-voltage motor microprocessor protection device according to any one of claims 1 to 4, characterized in that: The test current transformer was obtained by removing it from the spare circuit of the microcomputer protection device of the low-voltage motor under test.

6. The test method for the low-voltage motor microprocessor protection device according to any one of claims 1 to 4, characterized in that: The three-phase test current source and the switch quantity monitoring equipment are integrated into a relay protection tester.

7. The test method for the low-voltage motor microprocessor protection device according to any one of claims 1 to 4, characterized in that: The protection function test includes one or more of the following tests: instantaneous overcurrent protection test, thermal overload protection test, zero-sequence overcurrent protection test, residual current protection test, locked rotor protection test, and phase current imbalance protection test.

8. The test method for the low-voltage motor microprocessor protection device according to claim 7, characterized in that: The protection function test is performed according to the following steps: Step S1, set the target protection function to be tested for the microprocessor protection device of the low-voltage motor under test, set the three-phase test current I1 required by the target protection function to be applied to the primary side of the current transformer, and calculate the changed three-phase test current I2; Step S2, exit or turn off other functions of the microprocessor protection device of the low-voltage motor under test except for the target protection function; Step S3, perform a protection action sensitivity test, including: Step S3-1, temporarily set the action time of the microprocessor protection device of the low-voltage motor under test to 0 seconds; Step S3-2, use a three-phase test current source to apply 95% of I2 to the three-phase test current. Current is applied to the primary side of the current transformer, and the three-phase test current is gradually increased in steps of 0.01A until the switch monitoring device receives the protection action signal, that is, when the microprocessor protection device of the tested low-voltage motor is triggered to perform the protection action, the three-phase test current at this time is recorded as the operating current; Step S3-3: Repeat step S3-2 at least five times and calculate the average value of the operating current; Step S3-4: Determine whether the operating current error exceeds the preset operating current error threshold. If so, it is determined that the sensitivity of the microprocessor protection device of the tested low-voltage motor to perform the protection action is unqualified; otherwise, it is determined to be qualified; Wherein, operating current error = (average operating current - operating current design value) ÷ operating current design value.

9. The test method for the low-voltage motor microprocessor protection device according to claim 8, characterized in that: The protection function test further includes: Step S4, performing a protection action speed test, including: Step S4-1, setting the action time of the microprocessor protection device for the tested low-voltage motor to the design setpoint; Step S4-2, applying a three-phase test current of 105%I2 to the primary side of the current transformer using a three-phase test current source, and receiving the protection action signal through the switch monitoring device to determine the actual action time of the microprocessor protection device for the tested low-voltage motor; Step S4-3, repeating Step S4-2 at least five times and calculating the average actual action time; Step S4-4, determining whether the action time error exceeds the preset action time error threshold. If so, the speed at which the microprocessor protection device for the tested low-voltage motor performs the protection action is deemed unqualified; otherwise, it is deemed qualified. Wherein, action time error = (average actual action time - design setpoint) ÷ design setpoint.

10. The test method for the low-voltage motor microprocessor protection device according to claim 8, characterized in that: The protection function test also includes: Step S5, performing a protection action reliability test, including: Step S5-1, directly applying a three-phase test current of 95% I2 to the primary side of the current transformer using a three-phase test current source, repeating the process three times. If the microprocessor protection device of the tested low-voltage motor does not perform any protection action, then condition one is satisfied; Step S5-2, directly applying a three-phase test current of 105% I2 to the primary side of the current transformer using a three-phase test current source, repeating the process three times. If the microprocessor protection device of the tested low-voltage motor performs any protection action, then condition two is satisfied; Step S5-3, if both condition one and condition two are satisfied, then the reliability of the microprocessor protection device of the tested low-voltage motor is qualified; otherwise, it is deemed unqualified.

Images