Method for testing and distinguishing polarity of current transformer of differential protection of inner bridge connection main transformer

Abstract

The application discloses a method for testing and distinguishing polarity of a current transformer of a main transformer differential protection in an inner bridge connection, and comprises the following steps: S1, first, determining the position of the main transformer, setting an analog bus outside each current transformer (on the side far from the main transformer) according to the position of each current transformer on the side of the main transformer, ignoring the position of the actual bus, and taking the bus as a reference; the testing and distinguishing method of the application does not need to explicitly indicate that the primary polarity end of the current transformer is directed to the bus or to the line, does not need to explicitly indicate whether the secondary winding lead-out mode is s1 lead-out or s2 lead-out, does not need each current transformer to judge the secondary winding waveform and polarity through the minus polarity characteristic, and does not need to judge whether the differential current is zero, so that the problem of whether the winding polarity test result of the current transformer of the main transformer differential protection in the inner bridge connection is correct can be solved, the method is time-saving and labor-saving, is not prone to errors, and can uniformly and quickly judge the secondary winding lead-out mode.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of current transformer polarity testing, in particular to a method for testing and discriminating the polarity of a current transformer for main transformer differential protection in an inner bridge connection. BACKGROUND

[0002] At present, there are many old 110kV load substations in city power supply companies. As the main protection for transformers, main transformer differential protection is the most critical part. In order to ensure the correct polarity of the current loop, polarity testing, commonly known as "polarity beating", must be carried out when the main transformer differential protection is replaced. However, the polarity control end standards are not uniform during the assembly of the current transformer in the 110kV inner bridge connection substation. The polarity of the current transformer on each side is different. Moreover, the current transformer is exposed to the outdoor environment for a long time, and the polarity end mark of the device is difficult to identify. There is no simple and unified method for polarity testing. Therefore, there is an urgent need for a simple method to help us quickly determine whether the polarity of the secondary winding of the current transformer connected to the main transformer differential protection is correct.

[0003] In the existing method, the polarity of each side current transformer needs to be tested first. Then, after the test is completed, the test results of each side current transformer are comprehensively analyzed and judged in combination with the polarity end direction of each side current transformer and the condition that the primary current flows into and out of the main transformer. Finally, a conclusion whether correct or not can be drawn.

[0004] However, due to the different standards of the primary polarity end and secondary outgoing line of each switch, it takes time and effort to analyze and judge on the job site, which affects the progress of the operation. At the same time, the method of measuring the polarity of the current transformer after the device is loaded requires verification after the device is powered on. This method is time-consuming and labor-intensive, and has a certain degree of danger. SUMMARY

[0005] The purpose of the present application is to provide a method for testing and discriminating the polarity of a current transformer for main transformer differential protection in an inner bridge connection, so as to solve the problem that the standards of the primary polarity end and secondary outgoing line of each switch are different, which takes time and effort to analyze and judge on the job site, and affects the progress of the operation.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solution: a method for testing and discriminating the polarity of a current transformer for main transformer differential protection in an inner bridge connection, comprising the following steps:

[0007] S1, first, determine the position of the main transformer, and set a simulated busbar outside each current transformer (on the side away from the main transformer) according to the position of the current transformer on each side of the determined main transformer, ignoring the position of the actual busbar, and taking the busbar as the reference;

[0008] S2, after the completion of the setting simulation bus, according to the above step S1 polarity test method, by the direct current of the battery in primary side, the polarity test is carried out by the pointer table in the secondary side of the current transformer.

[0009] Preferably, in step S1, during the polarity test, the positive electrode of the battery is connected to the simulation bus side of the current transformer, the negative electrode is connected to the main transformer side of the current transformer, and the positive electrode of the pointer table in the protection screen is connected to the A, B and C three-phase of the inflow protection device, and the negative electrode of the pointer table is connected to the neutral line N.

[0010] Preferably, in step S2, the correct result of the test has only two kinds: (1) the polarity test pointer table of the current transformer on each side of the main transformer is all positive bias first and negative bias later; (2) the polarity test instrument of the current transformer on each side of the main transformer is all negative bias first and positive bias later.

[0011] Preferably, in step S2, if the correct result of the test is inconsistent, the inconsistent winding needs to be adjusted to the secondary winding lead-out mode to make it consistent finally.

[0012] Compared with the prior art, the beneficial effects of the present application are:

[0013] The test and discrimination method of the present application does not need to determine whether the primary polarity end of the current transformer points to the bus or the line, does not need to determine whether the secondary winding lead-out mode is s1 lead-out or s2 lead-out, does not need to determine whether the differential current is zero, and can solve the problem of whether the winding polarity test result of the current transformer of the main transformer differential protection is correct under the inner bridge connection form. The method saves time and effort, is not easy to make mistakes, can uniformly and quickly determine the secondary winding lead-out mode, the corresponding polarity test method and test result, greatly improves the on-site work efficiency under the condition of ensuring the correctness of the result. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The test method diagram of the test and discrimination method of the inner bridge connection main transformer differential protection current transformer polarity of the present application. DETAILED DESCRIPTION

[0015] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0016] Embodiment 1:

[0017] Please refer to Figure 1The application provides a technical scheme: a polarity test and discrimination method for a main transformer differential protection current transformer of an inner bridge connection, which comprises the following steps:

[0018] S1, first, the position of the main transformer is determined, an analog bus is set outside each current transformer (the side far from the main transformer) according to the position of each side of the current transformer of the determined main transformer, as shown in the position of the dashed line in Figure 1 the middle, the position of the actual bus is ignored, the bus is used as a reference, at this time, each side of the switch current transformer is located between the analog bus and the main transformer, if the direction of each side of the switch current transformer polarity end can be distinguished, only the positive electrode of the battery is connected to the analog bus side of the current transformer, the negative electrode is connected to the main transformer side of the current transformer, the positive electrode of the pointer table in the protection screen is connected to the A, B and C three-phase current flowing into the protection device, and the negative electrode of the pointer table is connected to the neutral line N during the polarity test;

[0019] S2, after the setting of the analog bus is completed, the polarity test is performed on the secondary side of the current transformer by using the direct current of the battery on the primary side according to the polarity test method in the above step S1, after the test result is obtained, there are only two correct results: (1) the polarity test pointer table of each side of the current transformer of the main transformer is all first positive and then reverse; (2) the polarity test instrument of each side of the current transformer of the main transformer is all first reverse and then positive; if the inconsistent situation occurs, the inconsistent winding needs to be adjusted to make the secondary winding lead mode consistent finally, and the correct polarity test result is shown in Table 1.

[0020]

[0021] Correct polarity test result table Table 1

[0022] Embodiment 2

[0023] Please refer to Figure 1 The application provides a technical scheme: a polarity test and discrimination method for a main transformer differential protection current transformer of an inner bridge connection, which comprises the following steps:

[0024] S1, first, the position of the main transformer is determined, an analog bus is set outside each current transformer (the side far from the main transformer) according to the position of each side of the current transformer of the determined main transformer, the position of the actual bus is ignored, and the bus is used as a reference;

[0025] S2, after the setting of the analog bus is completed, the polarity test is performed on the secondary side of the current transformer by using the direct current of the battery on the primary side according to the polarity test method in the above step S1.

[0026] In the preferred technical scheme of the embodiment, an analog bus is set outside each current transformer (the side far from the main transformer), as shown in the position of the dashed line in Figure 1 the middle; forFigure 1 For transformer A with a bridge connection, using conventional methods, in order to ensure the accuracy of the differential current calculation for differential protection, ... Figure 1 When the middle arrow indicates the power flow direction, a comprehensive analysis of the polarity test results, the direction of the primary polarity terminal of the current transformer, and the lead-out method of the secondary winding are used to determine whether the differential current is 0 under normal operating conditions based on the reduced polarity characteristics. There is no simple and easy way to analyze each polarity terminal direction and secondary winding lead-out method of the current transformer, which is quite difficult and prone to errors.

[0027] In a preferred embodiment of this method, a simulated busbar is set on the outside of each current transformer (the side furthest from the main transformer), such as... Figure 1 As shown by the dashed line; with the set simulated busbar as a reference, the polarities of current transformers A and B both point towards the main transformer, and the polarity of current transformer C points towards the set simulated busbar; to determine whether the polarity test results are correct, it is not necessary to consider the secondary winding lead-out method of the current transformer and the polarity direction of the current transformer. Simply connect the positive terminal of the battery to the set simulated busbar side and the negative terminal to the main transformer side during the polarity test. After completing the set simulated busbar settings, following the above polarity test method, there are two correct polarity test results for each side: one is that the polarity test results of all current transformers on each side of the main transformer are all first forward deflected and then reverse deflected, and the other is that they are all first reverse deflected and then forward deflected. If inconsistencies occur, the secondary winding lead-out method needs to be adjusted to make them consistent.

[0028] In the preferred embodiment of this technical solution, the polarity method of the differential protection current transformer of the main transformer with internal bridge connection is used based on the set simulated bus. In the substation with internal bridge connection, no matter how the polarity of the current transformer on each side changes, the correct lead-out method of the secondary winding on each side of the main transformer can be determined very quickly.

[0029] In summary, the testing and discrimination method of the present invention does not require specifying whether the primary polarity terminal of the current transformer points to the bus or the line, nor does it require specifying whether the secondary winding lead-out method is S1 or S2. It also does not require determining the secondary winding waveform and polarity of each current transformer through its subtraction polarity characteristic, nor does it require determining whether the differential current is zero. This method solves the problem of determining the correctness of the polarity test results of the main transformer differential protection current transformer winding under an internal bridge connection configuration. This method is time-saving, labor-saving, and less prone to errors. It can uniformly and quickly determine the secondary winding lead-out method, as well as the corresponding polarity test method and test results, greatly improving on-site work efficiency while ensuring the accuracy of the results.

[0030] The above merely describes the embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent process transformation made by using the content of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for testing and distinguishing the polarity of a current transformer for differential protection of a main transformer with internal bridging, characterized in that, It comprises the following steps: S1, first, determine the location of the main transformer, according to the determined current transformer position on each side of the main transformer, set a simulation bus on the side of each current transformer away from the main transformer, ignore the actual bus position, take the simulation bus as the reference; In the step S1, during the polarity test, the positive electrode of the battery is connected to the simulation bus side of the current transformer, the negative electrode is connected to the main transformer side of the current transformer, and the positive electrode of the pointer table in the protection screen is connected to the A, B and C three-phase of the inflow protection device respectively, and the negative electrode of the pointer table is connected to the neutral line N; S2, after setting the simulation bus, according to the polarity test method of step S1, the direct current added to the primary side battery is used to test the polarity on the secondary side of the current transformer by the pointer table; In the step S2, the correct results of the test are as follows: (1) the polarity test pointer table of the current transformer on each side of the main transformer is all positive bias first and negative bias later; (2) the polarity test pointer table of the current transformer on each side of the main transformer is all negative bias first and positive bias later; In the step S2, if the correct results of the test are inconsistent, the inconsistent winding needs to adjust the secondary winding lead mode to make it consistent finally.

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