A system and method for verifying bus differential protection polarity using transformer excitation inrush current

Abstract

The invention discloses a system and method for verifying the polarity of bus differential protection by using transformer excitation inrush current, comprising a high-voltage bus unit, a bus power branch unit, a bus transformer branch unit, a bus differential protection device, a recording unit and a secondary circuit unit; the bus power branch unit and the bus transformer branch unit are connected to the high-voltage bus unit; the bus power branch unit and the bus transformer branch unit are connected to the bus differential protection device via a secondary circuit unit, and the recording unit is connected to the secondary circuit unit. The system and method can verify the polarity of bus differential protection by using transformer excitation inrush current, and are simple and easy to implement.

Description

Technical Field

[0001] The invention belongs to the technical field of power commissioning and power testing, and relates to a system and method for verifying the polarity of bus differential protection by utilizing transformer excitation surge current. Background Art

[0002] Bus differential protection is the main protection of high-voltage busbars. The operation of bus differential protection is related to whether the busbar fault can be correctly removed in the event of an accident. The basic principle of bus differential protection is to calculate the vector sum of the secondary currents of each branch connected to the busbar, and start the action element when the vector sum reaches the set action value. Bus differential protection system often suffers from misoperation of protection due to careless wiring, inaccurate calibration, and multiple grounding of the secondary circuit. Polarity verification is to simulate the load current flowing through each branch of the high-voltage busbar, and check whether the differential current of the bus differential protection is zero at this time, so as to determine whether the secondary current of the branch connected to the bus differential protection is correct. If it is not correct, the wiring of the secondary current and the set value of the bus differential protection should be modified until the differential current is zero. Usually, the polarity verification of each branch of the bus differential protection is completed through a load test. Then, for the branch connected to the transformer, a large amount of load cannot be organized at the initial stage of the transformer, and the rental of a dummy load requires a relatively high cost. Therefore, it is necessary to find a simple and easy new method for polarity verification of the bus differential protection transformer branch. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a system and method for verifying the polarity of bus differential protection by using transformer excitation inrush current. The system and method can verify the polarity of bus differential protection by using transformer excitation inrush current and are simple and easy to implement.

[0004] To achieve the above object, the system for verifying the polarity of bus differential protection by using transformer excitation inrush current of the present invention comprises a high-voltage bus unit, a bus power supply branch unit, a bus transformer branch unit, a bus differential protection device, a wave recording unit and a secondary circuit unit;

[0005] The bus power branch unit and the bus transformer branch unit are connected to the high-voltage bus unit; the bus power branch unit and the bus transformer branch unit are connected to the bus differential protection device through the secondary circuit unit, and the recording unit is connected to the secondary circuit unit.

[0006] The bus power branch unit includes a power supply, a power branch unit circuit breaker and a power branch unit current transformer; wherein the power supply is connected to the high-voltage bus unit via the power branch unit circuit breaker, the power branch unit current transformer is installed on the line between the power supply and the power branch unit circuit breaker, and the power branch unit current transformer is connected to the bus differential protection device via the secondary circuit unit.

[0007] The busbar transformer branch unit includes a transformer branch circuit breaker, a transformer branch current transformer, a transformer, a transformer low-voltage side circuit breaker and a transformer low-voltage side busbar; the transformer low-voltage side busbar is connected to the high-voltage busbar unit via the transformer low-voltage side circuit breaker, the transformer and the transformer branch circuit breaker, the transformer branch current transformer is installed on the line between the transformer and the transformer branch circuit breaker, and the transformer branch current transformer is connected to the bus differential protection device via the secondary circuit unit.

[0008] The secondary circuit unit includes a first secondary circuit and a second secondary circuit, wherein the power branch unit current transformer is connected to the bus differential protection device via the first secondary circuit, and the transformer branch current transformer is connected to the bus differential protection device via the second secondary circuit.

[0009] The recording unit includes a recording device, a first sampling device and a second sampling device, wherein the first sampling device is connected to the first secondary circuit, the second sampling device is connected to the second secondary circuit, the first sampling device and the second sampling device are both connected to the recording device, and the recording device is started by the position node of the transformer branch circuit breaker.

[0010] The method for verifying the polarity of bus differential protection by using transformer excitation inrush current of the present invention comprises the following steps:

[0011] 1) Carry out the preparation work for the verification of bus differential protection polarity;

[0012] 2) Close the transformer branch circuit breaker to perform the first impact on the transformer. The location node of the transformer branch circuit breaker starts the recording device to record the wave. After the transformer is normal, go to step 3);

[0013] 3) Observe whether the recording device has recorded the secondary current of the power supply branch on the first secondary circuit and the secondary current of the transformer branch on the second secondary circuit. If the recording device has recorded the secondary current of the power supply branch on the first secondary circuit and the secondary current of the transformer branch on the second secondary circuit, go to step 5); otherwise, go to step 4);

[0014] 4) Disconnect the transformer branch circuit breaker, shut down the transformer, remove the control power supply of the transformer branch circuit breaker, eliminate the recording unit defect, and then go to step 2);

[0015] 5) Calculate and determine whether the vector sum of the power branch secondary current and the transformer branch secondary current recorded by the recording device is zero. When the vector sum of the power branch secondary current and the transformer branch secondary current is zero, go to step 7); otherwise, go to step 6);

[0016] 6) Disconnect the transformer branch circuit breaker, shut down the transformer, remove the control power supply of the transformer branch circuit breaker, find and eliminate abnormal defects, and then go to step 2);

[0017] 7) Considering that the polarity of the transformer branch secondary current is correct, the bus differential protection is activated, and then go to step 8);

[0018] 8) The mother differential protection polarity verification test is completed.

[0019] The specific operations of step 1) are:

[0020] 11) Complete the static check of the busbar differential protection device;

[0021] 12) Set the bus differential protection setting value according to the formal setting value list;

[0022] 13) Check the wiring of the first secondary circuit and the second secondary circuit to ensure that the current transformer of the power branch unit and the current transformer of the transformer branch are in good contact;

[0023] 14) Ensure that the transformer is energized, the transformer insulation is qualified, the transformer low-voltage side circuit breaker is in the open position, and its control power supply has been disconnected;

[0024] 15) Ensure that the secondary current of the bus power branch unit and the bus transformer branch unit is connected to the recording device through the first sampling device and the second sampling device, and ensure that the position node for starting the recording device in the transformer branch circuit breaker is connected to the recording device;

[0025] 16) Make sure the high-voltage busbar unit is energized.

[0026] The specific operations of step 2) are:

[0027] Turn on the control power supply of the transformer branch circuit breaker, close the transformer branch circuit breaker, and wait until there is no abnormality after the transformer is energized. Among them, the position node of the transformer branch circuit breaker starts the recording device at the moment the transformer branch circuit breaker is closed.

[0028] According to the bus differential protection device, the vector sum of the power branch secondary current and the transformer branch secondary current is calculated. When the vector sum of the power branch secondary current and the transformer branch secondary current is zero, it is considered that the polarity of the transformer branch secondary current is correct, otherwise, it is considered that the transformer branch secondary current is incorrect.

[0029] Step 6) also includes:

[0030] 601) disconnect the transformer branch circuit breaker and shut down the transformer;

[0031] 602) Check the secondary current loop of the busbar transformer branch unit, check whether the transformation ratio selected by the transformer branch current transformer is consistent with the given value; check whether the secondary current loop of the busbar transformer branch unit is grounded at two points; check whether the secondary current loop of the busbar transformer branch unit is shunted; check whether the secondary loop connection of the busbar transformer branch unit is secure;

[0032] 603) Eliminate defects.

[0033] The present invention has the following beneficial effects:

[0034] The system and method for using transformer excitation surge current to verify bus differential protection polarity described in the present invention, during specific operation, uses the excitation surge current when the transformer is transmitting power as the load current to verify whether the polarity of the secondary current of the newly connected transformer branch is correct. There is no need to rent a dummy load as a load, thereby reducing rental costs and installation costs. The operation is convenient and simple, and it is easy to implement. The method is simple and easy to operate, ensures that the bus differential protection polarity is correct, prevents the bus differential protection from malfunctioning, can be widely applied to high-voltage buses with different main connection forms, is convenient for promotion and use at the commissioning site, and ensures that the bus differential protection is accurate and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A circuit diagram of the present invention;

[0036] Figure 2 It is a flow chart of the present invention.

[0037] Among them, 1 is a high-voltage bus unit, 2 is a bus power branch unit, 3 is a bus transformer branch unit, 4 is a recording unit, 5 is a recording device, 6 is a bus differential protection device, 7 is a secondary circuit unit, 8 is a power supply, 9 is a power supply branch unit current transformer, 10 is a power supply branch unit circuit breaker, 11 is a transformer branch circuit breaker, 12 is a transformer branch current transformer, 13 is a transformer, 14 is a transformer low-voltage side circuit breaker, 15 is a transformer low-voltage side bus, 16 is a node, 171 is a first sampling device, and 172 is a second sampling device. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0039] refer to Figure 1The system for verifying the polarity of bus differential protection by using transformer excitation inrush current of the present invention comprises a high-voltage bus unit 1, a bus power branch unit 2, a bus transformer branch unit 3, a bus differential protection device 6, a recording unit 4 and a secondary circuit unit 7; the bus power branch unit 2 and the bus transformer branch unit 3 are connected to the high-voltage bus unit 1; the bus power branch unit 2 and the bus transformer branch unit 3 are connected to the bus differential protection device 6 through the secondary circuit unit 7, and the recording unit 4 is connected to the secondary circuit unit 7.

[0040] The bus power supply branch unit 2 includes a power supply 8, a power supply branch unit circuit breaker 10 and a power supply branch unit current transformer 9; wherein the power supply 8 is connected to the high-voltage bus unit 1 via the power supply branch unit circuit breaker 10, the power supply branch unit current transformer 9 is installed on the line between the power supply 8 and the power supply branch unit circuit breaker 10, and the power supply branch unit current transformer 9 is connected to the bus differential protection device 6 via the secondary circuit unit 7.

[0041] The bus transformer branch unit 3 includes a transformer branch circuit breaker 11, a transformer branch current transformer 12, a transformer 13, a transformer low-voltage side circuit breaker 14 and a transformer low-voltage side bus 15; the transformer low-voltage side bus 15 is connected to the high-voltage bus unit 1 via the transformer low-voltage side circuit breaker 14, the transformer 13 and the transformer branch circuit breaker 11, the transformer branch current transformer 12 is installed on the line between the transformer 13 and the transformer branch circuit breaker 11, and the transformer branch current transformer 12 is connected to the bus differential protection device 6 via the secondary circuit unit 7.

[0042] The secondary circuit unit 7 includes a first secondary circuit and a second secondary circuit, wherein the power branch unit current transformer 9 is connected to the bus differential protection device 6 via the first secondary circuit, and the transformer branch current transformer 12 is connected to the bus differential protection device 6 via the second secondary circuit.

[0043] The recording unit 4 includes a recording device 5, a first sampling device 171 and a second sampling device 172, wherein the first sampling device 171 is connected to the first secondary circuit, the second sampling device 172 is connected to the second secondary circuit, the first sampling device 171 and the second sampling device 172 are both connected to the recording device 5, and the recording device 5 is started by the position node 16 of the transformer branch circuit breaker 11.

[0044] refer to Figure 2 The method for verifying the polarity of bus differential protection by using transformer excitation inrush current of the present invention comprises the following steps:

[0045] 1) Carry out the preparation work for the verification of bus differential protection polarity;

[0046] 2) Close the transformer branch circuit breaker 11 to perform the first impact on the transformer 13. The position node 16 of the transformer branch circuit breaker 11 starts the recording device 5 to record the wave. After the transformer 13 is normal, go to step 3);

[0047] 3) Observe whether the recording device 5 has recorded the power supply branch secondary current on the first secondary circuit and the transformer branch secondary current on the second secondary circuit. When the recording device 5 has recorded the power supply branch secondary current on the first secondary circuit and the transformer branch secondary current on the second secondary circuit, go to step 5); otherwise, go to step 4);

[0048] 4) Disconnect the transformer branch circuit breaker 11, shut down the transformer 13, exit the control power supply of the transformer branch circuit breaker 11, eliminate the defect of the recording unit 4, and then go to step 2);

[0049] 5) Calculate and determine whether the vector sum of the power branch secondary current and the transformer branch secondary current recorded by the recording device 5 is zero. When the vector sum of the power branch secondary current and the transformer branch secondary current is zero, go to step 7); otherwise, go to step 6);

[0050] 6) Disconnect the transformer branch circuit breaker 11, shut down the transformer 13, exit the control power supply of the transformer branch circuit breaker 11, find and eliminate abnormal defects, and then go to step 2);

[0051] 7) Considering that the polarity of the transformer branch secondary current is correct, the bus differential protection is activated, and then go to step 8);

[0052] 8) The mother differential protection polarity verification test is completed.

[0053] The specific operations of step 1) are:

[0054] 11) Complete the static check of the busbar differential protection device 6;

[0055] 12) Set the bus differential protection setting value according to the formal setting value list;

[0056] 13) Check the wiring of the first secondary circuit and the second secondary circuit to ensure that the power branch unit current transformer 9 and the transformer branch current transformer 12 are in good contact;

[0057] 14) Ensure that the transformer 13 is energized, the insulation of the transformer 13 is qualified, the circuit breaker 14 on the low-voltage side of the transformer is in the open position, and its control power supply has been disconnected;

[0058] 15) ensuring that the secondary currents of the bus power branch unit 2 and the bus transformer branch unit 3 are connected to the recording device 5 through the first sampling device 171 and the second sampling device 172, and ensuring that the position node 16 for starting the recording device 5 in the transformer branch circuit breaker 11 is connected to the recording device 5;

[0059] 16) Ensure that the high-voltage busbar unit 1 is energized.

[0060] The specific operations of step 2) are:

[0061] The control power supply of the transformer branch circuit breaker 11 is turned on, the transformer branch circuit breaker 11 is closed, and the transformer 13 is waited for to be energized without abnormality. The position node 16 of the transformer branch circuit breaker 11 starts the recording device 5 at the moment when the transformer branch circuit breaker 11 is closed.

[0062] According to the mother differential protection device 6, the vector sum of the power supply branch secondary current and the transformer branch secondary current is calculated. When the vector sum of the power supply branch secondary current and the transformer branch secondary current is zero, it is considered that the polarity of the transformer branch secondary current is correct, otherwise, it is considered that the transformer branch secondary current is incorrect.

[0063] Step 6) also includes:

[0064] 601) disconnect the transformer branch circuit breaker 11, and the transformer 13 is powered off;

[0065] 602) Check the secondary current loop of the busbar transformer branch unit 3, check whether the transformation ratio selected by the transformer branch current transformer 12 is consistent with the given value; check whether there is two-point grounding in the secondary current loop of the busbar transformer branch unit 3; check whether there is shunting phenomenon in the secondary current loop of the busbar transformer branch unit 3; check whether the secondary loop connection of the busbar transformer branch unit 3 is reliable;

[0066] 603) Eliminate defects.

[0067] When the present invention performs the polarity check of the bus differential protection, the excitation surge current when the transformer 13 is powered on is used as the load current to check whether the polarity of the secondary current of the newly connected transformer branch is correct. The recording device 5 records the waveform and performs vector calculation on the currents of the two branches according to the bus differential protection principle. It can accurately determine whether the polarity of the bus differential protection is correct, thereby eliminating defects and ensuring that the bus differential protection does not malfunction.

[0068] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for checking the polarity of bus differential protection using transformer excitation inrush current, characterized in that: A system for verifying the polarity of bus differential protection by using transformer excitation inrush current, the system comprising a high-voltage bus unit (1), a bus power supply branch unit (2), a bus transformer branch unit (3), a bus differential protection device (6), a wave recording unit (4) and a secondary circuit unit (7); The bus power branch unit (2) and the bus transformer branch unit (3) are connected to the high-voltage bus unit (1); the bus power branch unit (2) and the bus transformer branch unit (3) are connected to the bus differential protection device (6) via the secondary circuit unit (7); and the wave recording unit (4) is connected to the secondary circuit unit (7); The bus power branch unit (2) comprises a power source (8), a power source branch unit circuit breaker (10) and a power source branch unit current transformer (9); wherein the power source (8) is connected to the high-voltage bus unit (1) via the power source branch unit circuit breaker (10); the power source branch unit current transformer (9) is installed on the line between the power source (8) and the power source branch unit circuit breaker (10); and the power source branch unit current transformer (9) is connected to the bus differential protection device (6) via the secondary circuit unit (7); The busbar transformer branch unit (3) comprises a transformer branch circuit breaker (11), a transformer branch current transformer (12), a transformer (13), a transformer low-voltage side circuit breaker (14) and a transformer low-voltage side busbar (15); the transformer low-voltage side busbar (15) is connected to the high-voltage busbar unit (1) via the transformer low-voltage side circuit breaker (14), the transformer (13) and the transformer branch circuit breaker (11); the transformer branch current transformer (12) is installed on the line between the transformer (13) and the transformer branch circuit breaker (11); the transformer branch current transformer (12) is connected to the busbar differential protection device (6) via the secondary circuit unit (7); The following steps are involved: 1) Carry out the preparation work for the verification of bus differential protection polarity; 2) Closing the transformer branch circuit breaker (11) to perform the first impact on the transformer (13), the position node (16) of the transformer branch circuit breaker (11) starts the recording device (5) to record the wave, and after the transformer (13) is free of abnormality, proceed to step 3); 3) Observe whether the recording device (5) has recorded the power supply branch secondary current on the first secondary circuit and the transformer branch secondary current on the second secondary circuit. When the recording device (5) has recorded the power supply branch secondary current on the first secondary circuit and the transformer branch secondary current on the second secondary circuit, go to step 5); otherwise, go to step 4); 4) disconnect the transformer branch circuit breaker (11), shut down the transformer (13), remove the control power supply of the transformer branch circuit breaker (11), eliminate the defect of the recording unit (4), and then go to step 2); 5) Calculate and determine whether the vector sum of the power branch secondary current and the transformer branch secondary current recorded by the recording device (5) is zero. When the vector sum of the power branch secondary current and the transformer branch secondary current is zero, go to step 7); otherwise, go to step 6); 6) Disconnect the transformer branch circuit breaker (11), shut down the transformer (13), remove the control power supply of the transformer branch circuit breaker (11), find and eliminate the abnormal defect, and then go to step 2); 7) Considering that the polarity of the transformer branch secondary current is correct, activate the bus differential protection and go to step 8); 8) The mother differential protection polarity verification test is completed.

2. The method for verifying the polarity of bus differential protection by using transformer excitation inrush current according to claim 1 is characterized in that: The secondary circuit unit (7) comprises a first secondary circuit and a second secondary circuit, wherein the power branch unit current transformer (9) is connected to the bus differential protection device (6) via the first secondary circuit, and the transformer branch current transformer (12) is connected to the bus differential protection device (6) via the second secondary circuit.

3. The method for verifying the polarity of bus differential protection by using transformer excitation inrush current according to claim 1 is characterized in that: The recording unit (4) comprises a recording device (5), a first sampling device (171) and a second sampling device (172), wherein the first sampling device (171) is connected to the first secondary circuit, the second sampling device (172) is connected to the second secondary circuit, the first sampling device (171) and the second sampling device (172) are both connected to the recording device (5), and the recording device (5) is started using a position node (16) of a transformer branch circuit breaker (11).

4. The method for verifying the polarity of bus differential protection by using transformer excitation inrush current according to claim 1 is characterized in that: The specific operations of step 1) are: 11) Complete the static check of the busbar differential protection device (6); 12) Set the bus differential protection setting value according to the official setting value list; 13) Check the wiring of the first secondary circuit and the second secondary circuit to ensure that the power branch unit current transformer (9) and the transformer branch current transformer (12) are in good contact; 14) Ensure that the transformer (13) is energized, the insulation of the transformer (13) is qualified, the circuit breaker (14) on the low-voltage side of the transformer is in the open position, and its control power supply has been disconnected; 15) ensuring that the secondary currents of the bus power supply branch unit (2) and the bus transformer branch unit (3) are connected to the recording device (5) through the first sampling device (171) and the second sampling device (172), and ensuring that the position node (16) for starting the recording device (5) in the transformer branch circuit breaker (11) is connected to the recording device (5); 16) Ensure that the high-voltage busbar unit (1) is energized.

5. The method for verifying the polarity of bus differential protection by using transformer excitation inrush current according to claim 1 is characterized in that: The specific operations of step 2) are: The control power supply of the transformer branch circuit breaker (11) is turned on, the transformer branch circuit breaker (11) is closed, and the transformer (13) is waited for to be energized without abnormality, wherein the position node (16) of the transformer branch circuit breaker (11) starts the recording device (5) at the moment when the transformer branch circuit breaker (11) is closed.

6. The method for verifying bus differential protection polarity by using transformer excitation inrush current according to claim 1 is characterized in that: According to the mother differential protection device (6), the vector sum of the power branch secondary current and the transformer branch secondary current is calculated. When the vector sum of the power branch secondary current and the transformer branch secondary current is zero, it is considered that the polarity of the transformer branch secondary current is correct. Otherwise, it is considered that the transformer branch secondary current is incorrect.

7. The method for verifying bus differential protection polarity by using transformer excitation inrush current according to claim 1 is characterized in that: Step 6) also includes: 601) disconnect the transformer branch circuit breaker (11), and shut down the transformer (13); 602) Check the secondary current circuit of the busbar transformer branch unit (3), check whether the transformation ratio selected by the transformer branch current transformer (12) is consistent with the given value; check whether the secondary current circuit of the busbar transformer branch unit (3) has two-point grounding; check whether the secondary current circuit of the busbar transformer branch unit (3) has shunting phenomenon; check whether the secondary circuit wiring of the busbar transformer branch unit (3) is secure; 603) Eliminate defects.

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