Test method suitable for unit wiring system and used for checking protection polarity of plant transformer branch loop

Abstract

According to the test method for checking the protection polarity of the plant transformer branch loop, which is suitable for the unit wiring system, when the load of a plant transformer is very small, the operation mode of an electrical system is changed, and the plant branch current is increased without additionally starting or switching a plant electrical load under the condition of not additionally increasing primary equipment; the protection polarity of the plant transformer branch loop is checked in a high-efficiency and low-cost manner, and the influence on a plant load is avoided. The problems that the auxiliary power load design is small, the current checking requirement cannot be met, and the polarity checking condition does not exist on site can be solved. According to the scheme provided by the invention, the station service branch current does not need to be increased by additionally starting or switching the station service load, so that the influence on the station service load is avoided, the unnecessary operation is reduced, the operation complexity is reduced, and the personnel cost is saved. The current of a station branch can be increased without additionally arranging primary equipment, the verification of the differential protection polarity is completed, and the required personnel and equipment cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of power system protection, and particularly relates to a test method for checking the protection polarity of the factory transformer branch circuit applicable to the unit connection system. Background Art

[0002] In a power plant with unit connection, as Figure 1 shown in the figure, some generator-transformer units (such as 4F and 4B in the figure) are equipped with a station service transformer (such as 22B in the figure). For the main transformer differential protection of 4B, the secondary currents of the current transformers at the generator terminals of 4F (1LH and 2LH in the figure), the high-voltage side of the station service transformer 22B (13LH and 14LH in the figure), and the high-voltage side of 4B (9LH and 10LH in the figure) need to be collected to calculate the differential current of the transformer and achieve the differential protection function of the main transformer 4B.

[0003] According to the requirements of industry specifications, when the transformer protection is renovated or the current transformer is renovated, it is necessary to check the polarity of each branch circuit of the transformer protection through a load test. The test method is to measure the secondary amplitude and phase of the current of each branch with a current clamp meter on the transformer protection panel, and at the same time, view the current sampling amplitude, phase angle, and differential current value displayed by the device on the main transformer differential protection, and analyze and judge the recorded data to check the correctness of the differential protection polarity.

[0004] When selecting the transformation ratio of the current transformer, it is generally selected according to the low-voltage side of the main transformer, that is, the unit capacity. The transformation ratio of the current transformer on the high-voltage side of the station service transformer needs to consider the rated current of the unit, that is, to be consistent with the transformation ratio at the generator terminal. As shown in the figure, the normal rated current of the unit is 8000A, and the transformation ratios of the current transformers 1LH, 2LH, 13LH, and 14LH are selected as 12000 / 5. However, the capacity of the station service transformer is generally relatively small compared to the unit capacity (2%-5%). When conducting a load test, the station service transformer is under normal load or slightly lower load. For example, when the primary current value is 120A, the secondary side of the current transformer is only 5mA. This value is too small to enable the main transformer protection to read the accurate phase angle of the station service transformer branch sampling and the differential current value of the main transformer, so the load test for checking the polarity of the main transformer differential protection cannot be completed. For untested protection equipment, there is a possibility of incorrect polarity in the factory transformer branch. If a fault occurs in the high-voltage side body of the factory transformer during operation, it will cause the main transformer differential protection to malfunction and incorrectly trip the normal main transformer, resulting in abnormal power outage of the equipment. Summary of the Invention

[0005] The present invention provides a test method for checking the protection polarity of the factory transformer branch circuit applicable to the unit connection system. When the load carried by the factory transformer is very small, by changing the operation mode of the electrical system, without adding additional primary equipment and without the need to additionally start or switch the station service power load to increase the factory transformer branch current, the protection polarity of the factory transformer branch circuit can be checked with high efficiency and low cost.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A test method for checking the protection polarity of the factory transformer branch circuit applicable to the unit wiring system requires the main transformer to be verified, the corresponding unit, the factory transformer, the bus bar powered by the factory transformer, the bus bar connected to the bus bar powered by the factory transformer branch, and the corresponding unit and factory transformer in the unit wiring system to participate in the test, including the following steps: Step 1: Check that the unit capacities of two adjacent unit-wired units connected to the same high-voltage bus bar, as well as the transformation ratios, angular connections, and capacities of the main transformers, and the transformation ratios, angular connections, and capacities of the factory transformers are consistent; Step 2: Adjust the load conditions of the test unit and the adjacent non-test unit to be basically the same; Step 3: Check the voltage difference and phase difference of the factory power bus bars on the secondary sides of the two sections of factory power bus bars. When the voltage difference value and the phase difference are both less than the set values, close the bus tie switch between the factory power bus bars; Step 4: Adjust the output of the non-verified unit. Since they are in the same system, part of the power flow flows from the non-verified unit to the factory transformer branch circuit of the main transformer to be verified, increasing the current flowing through this branch, so that the phase angle of the factory transformer branch sampling and the differential current value of the main transformer can be collected by the sampling of the transformer protection device. By comparing the data, the differential protection polarity test of the main transformer can be completed, and the polarity of the differential protection can be checked.

[0007] In the above unit wiring system, it includes two sets of generator and transformer combinations using the unit wiring method, namely generator 4F and main transformer 4B, generator 5F and main transformer 5B. There is a factory transformer 22B between generator 4F and main transformer 4B, and a factory transformer 23B between generator 5F and main transformer 5B. The factory transformer 22B and the factory transformer 23B are respectively connected to the factory power bus bars 4LM and 5LM, and the factory power bus bars 4LM and 5LM are connected by a bus tie switch 6540.

[0008] The high-voltage sides of the above main transformer 4B and main transformer 5B are connected to the high-voltage bus bar 1LM.

[0009] The low-voltage side of the above factory transformer 22B is connected to the factory power bus bar 4LM through a circuit breaker 6422, and the low-voltage side of the factory transformer 23B is connected to the factory power bus bar 5LM through a circuit breaker 6523. The method for checking the load polarity of the factory transformer 22B branch of the differential protection of the above main transformer 4B is as follows: Step 1. Check the capacities of the two generator sets of 4F and 5F, as well as the turns ratios, angular connections and capacities of the main transformers 4B and 5B to be consistent. Check the turns ratios, angular connections and capacities of the auxiliary transformers 22B and 23B to be consistent; Step 2. Adjust the power generation conditions of the two generator sets of 4F and 5F to be consistent; Step 3. Check the bus voltage difference and phase difference of the auxiliary power buses 4LM and 5LM. When both the voltage difference and phase difference are less than the set values, synchronously close the bus tie switch 6540 between the auxiliary power buses; Step 4. Adjust the output of the 5F generator set. Part of the power flow will pass through the path of generator 5F → auxiliary transformer 23B → circuit breaker 6523 → bus tie switch 6540 → circuit breaker 6422 → auxiliary transformer 22B → main transformer 4B, so that the current on the plant transformer branch 22B circuit of the main transformer 4B increases, and it is sufficient for the clamp meter and the protection device to sample and read the current amplitude, phase angle and differential current, and complete the load test for verification.

[0010] The present invention provides a test method for checking the polarity of the protection of the plant transformer branch circuit applicable to the unit connection system, and has the following beneficial effects: 1. It can solve the problems that the design of the auxiliary power load is small and cannot meet the requirements of the verification current, and the on-site conditions are not available for checking the polarity.

[0011] 2. The process of manually switching or enabling the auxiliary power load is complex and will affect the in-plant power consumption. The solution of the present invention's patent does not require additional start-up or switching of the auxiliary power load to increase the current of the plant transformer branch, avoids affecting the auxiliary power load, reduces unnecessary operations, reduces the operation complexity, and saves personnel costs.

[0012] 3. It is not necessary to additionally increase primary equipment to increase the current of the plant transformer branch and complete the verification of the differential protection polarity, reducing the required personnel and equipment costs. Description of the Drawings

[0013] The following will further illustrate the present invention in conjunction with the drawings and embodiments: Figure 1 It is the electrical system diagram of the unit connection system of the present invention. Detailed Embodiments

[0014] To make the purpose, technical solutions and advantages of the present invention clearer, the following content will systematically and completely describe the specific technical solutions of the present invention in conjunction with the drawings provided according to the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0015] A test method for checking the polarity of the protection of the auxiliary transformer branch circuit applicable to the unit wiring system requires the main transformer to be verified, the corresponding units, the auxiliary transformer, the busbar powered by the auxiliary transformer, the busbar connected to the busbar powered by the auxiliary transformer branch, and the corresponding units and auxiliary transformers in the unit wiring system to participate in the test, including the following steps: Step 1: Check that the unit capacities of two adjacent unit-wired units connected to the same high-voltage busbar, as well as the transformation ratios, angular connections, and capacities of the main transformers, the transformation ratios, angular connections, and capacities of the auxiliary transformers are consistent; Step 2: Adjust the load conditions of the test unit and the adjacent non-test unit to be basically the same; Step 3: Check the voltage difference and phase difference of the auxiliary power busbars on the secondary sides of the two sections of auxiliary power busbars. When both the voltage difference value and the phase difference are less than the set values, close the sectionalizing switch between the auxiliary power busbars; Step 4: Adjust the output of the non-verified unit. Since they are in the same system, part of the power flow flows from the non-verified unit to the auxiliary transformer branch circuit of the main transformer to be verified, increasing the current flowing through this branch, so that the phase angle of the auxiliary transformer branch sampling and the differential current value of the main transformer can be collected by the sampling of the transformer protection device. By comparing the data, the differential protection polarity test of the main transformer can be completed to check the polarity of the differential protection.

[0016] In the above unit wiring system, it includes two sets of generator and transformer combinations using the unit wiring method, namely generator 4F and main transformer 4B, generator 5F and main transformer 5B. There is an auxiliary transformer 22B between generator 4F and main transformer 4B, and an auxiliary transformer 23B between generator 5F and main transformer 5B. The auxiliary transformer 22B and the auxiliary transformer 23B are respectively connected to the auxiliary power busbars 4LM and 5LM, and the auxiliary power busbars 4LM and 5LM are connected by a sectionalizing switch 6540.

[0017] The high-voltage sides of the above main transformer 4B and main transformer 5B are connected to the high-voltage busbar 1LM.

[0018] The low-voltage side of the above auxiliary transformer 22B is connected to the auxiliary power busbar 4LM through a circuit breaker 6422, and the low-voltage side of the auxiliary transformer 23B is connected to the auxiliary power busbar 5LM through a circuit breaker 6523. The method for checking the load polarity of the auxiliary transformer 22B branch of the differential protection of the above main transformer 4B is as follows: Step1: Check that the capacities of the two generator sets 4F and 5F, as well as the transformation ratios, angular connections, and capacities of the main transformers 4B and 5B are consistent, and check that the transformation ratios, angular connections, and capacities of the auxiliary transformers 22B and 23B are consistent; Step2: Adjust the power generation conditions of the two generator sets 4F and 5F to be the same; Step 3. Check the bus voltage difference and phase difference of the auxiliary power busbars 4LM and 5LM. When both the voltage difference and phase difference are less than the set values, synchronously close the bus coupler switch 6540 between the auxiliary power busbars. Step 4. Adjust the output of the 5F generator set. Part of the power flow will pass through the path of generator 5F → auxiliary transformer 23B → circuit breaker 6523 → bus coupler switch 6540 → circuit breaker 6422 → auxiliary transformer 22B → main transformer 4B, so that the current on the 22B circuit of the auxiliary transformer branch of the main transformer 4B increases, and it is sufficient for the clamp meter and protection device to sample and read the current amplitude, phase angle, and differential current to complete the load test.

[0019] Embodiment 1: As Figure 1 shown in the electrical system diagram of the unit connection with an auxiliary transformer, the normal rated current of the unit is 8000A, and the transformation ratios of current transformers 1LH, 2LH, 13LH, and 14LH are selected as 12000 / 5. Both 4FB and 5FB are in the unit connection mode and are connected to 220kV 1LM. 4FB is equipped with auxiliary transformer 22B, and 5FB is equipped with auxiliary transformer 23B. 22B supplies power to the auxiliary power busbar 4LM, and 23B supplies power to the auxiliary power busbar 5LM. The 4LM busbar and the 5LM busbar are connected through the bus coupler switch 6540. If you want to check the load polarity of the 22B branch of the 4B differential protection in 4FB, the following method can be used: 1) Check the capacities of the two generator sets 4F and 5F, and ensure that the transformation ratios, angle connections, and capacities of 4B and 5B are the same, and the transformation ratios, angle connections, and capacities of auxiliary transformers 22B and 23B are the same.

[0020] 2) Adjust the power generation conditions of the 4F and 5F generator sets to be the same.

[0021] 3) Check the bus voltage difference and phase difference of the auxiliary power busbars 4LM and 5LM. When both the voltage difference and phase difference are very small, synchronously close the bus coupler switch 6540DL between the auxiliary power busbars.

[0022] 4) Adjust the output of the 5F generator set. Part of the power flow will pass through the path of 5F → 23B → 6523 → 6540 → 6422 → 22B → 4B, so that the current on the 22B circuit of the 4B auxiliary transformer branch increases to 480A, that is, 20mA on the secondary side, which is sufficient for the clamp meter and protection device to sample and read the current amplitude, phase angle, and differential current to complete the load test.

Claims

1. A test method for checking the protection polarity of the factory transformer branch circuit applicable to the unit wiring system, characterized in that, In the unit connection system, the main transformer to be verified, the corresponding units, the auxiliary transformer, the busbar connected to the auxiliary transformer, the busbar connected to the branch of the auxiliary transformer, and the corresponding units and auxiliary transformers need to participate in the test, including the following steps: Step 1: Check that the unit capacities of two adjacent unit-connected units connected to the same high-voltage busbar are the same, and the transformation ratios, angular connections, and capacities of the main transformers are the same, as well as the transformation ratios, angular connections, and capacities of the auxiliary transformers; Step 2: Adjust the load conditions of the test unit and the adjacent non-test units to be basically the same; Step 3: Check the voltage difference and phase difference of the auxiliary power busbars on the secondary sides of the two sections of auxiliary power busbars. When the voltage difference value and the phase difference are both less than the set values, close the sectionalizing switch between the auxiliary power busbars; Step 4: Adjust the output of the non-verified units. Since they are in the same system, part of the power flow flows from the non-verified units to the branch circuit of the auxiliary transformer protected by the main transformer to be verified, increasing the current flowing through this branch, so that the phase angle sampled by the auxiliary transformer branch and the differential current value of the main transformer can be collected by the sampling of the transformer protection device. By comparing the data, the polarity test of the main transformer differential protection can be completed, and the polarity of the differential protection can be verified.

2. The test method for checking the protection polarity of the plant transformer branch circuit applicable to the unit wiring system according to claim 1, characterized in that, In the unit connection system described above, it includes two sets of generator and transformer combinations using the unit connection method, namely generator 4F and main transformer 4B, generator 5F and main transformer 5B. There is an auxiliary transformer 22B between generator 4F and main transformer 4B, and an auxiliary transformer 23B between generator 5F and main transformer 5B. The auxiliary transformer 22B and the auxiliary transformer 23B are respectively connected to the auxiliary power busbars 4LM and 5LM, and the auxiliary power busbars 4LM and 5LM are connected by a sectionalizing switch 6540.

3. The test method for checking the protection polarity of the factory transformer branch circuit applicable to the unit wiring system according to claim 2, wherein The high-voltage sides of the main transformer 4B and the main transformer 5B are connected to the high-voltage busbar 1LM.

4. The test method for checking the protection polarity of the factory transformer branch circuit applicable to the unit wiring system according to claim 3, characterized in that, The low-voltage side of the auxiliary transformer 22B is connected to the auxiliary power busbar 4LM through a circuit breaker 6422, and the low-voltage side of the auxiliary transformer 23B is connected to the auxiliary power busbar 5LM through a circuit breaker 6523.

5. The test method for checking the protection polarity of the factory transformer branch circuit applicable to the unit wiring system according to claim 4, characterized in that, The method for verifying the load polarity of the branch of the auxiliary transformer 22B of the differential protection of the main transformer 4B is as follows: Step1: Check that the capacities of the two generator sets 4F and 5F are the same, and the transformation ratios, angular connections, and capacities of the main transformers 4B and 5B are the same. Check that the transformation ratios, angular connections, and capacities of the auxiliary transformers 22B and 23B are the same; Step2: Adjust the power generation conditions of the two generator sets 4F and 5F to be the same; Step3: Check the voltage difference and phase difference of the auxiliary power busbars 4LM and 5LM. When the voltage difference and the phase difference are both less than the set values, synchronously close the sectionalizing switch 6540 between the auxiliary power busbars; Step4: Adjust the output of the generator set 5F. Part of the power flow will flow through the path of generator 5F → auxiliary transformer 23B → circuit breaker 6523 → sectionalizing switch 6540 → circuit breaker 6422 → auxiliary transformer 22B → main transformer 4B, increasing the current on the branch 22B of the auxiliary transformer of the main transformer 4B, so that the current amplitude, phase angle, and differential current can be read by the clamp meter and the sampling of the protection device, and the load verification test can be completed.

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