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The method of verifying the ct polarity of the high voltage side of the main transformer by using the excitation inrush current

A technology of excitation inrush current and high voltage side, which is applied in the direction of electric winding test, etc., can solve problems such as low reliability, malfunction or refusal of protection device, and affect the safe and stable operation of power system, so as to improve operation reliability and prevent malfunction or the effect of refusal to move

Active Publication Date: 2021-05-25
YUNNAN POWER GRID +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Due to the large CT transformation ratio on the high-voltage side of the transformer, limited by the capacity of the independent power supply, the current generated by the primary-side flow test on the secondary side is extremely small, even only 2-5mA, and most phase meters cannot meet this accuracy. The reliability of the CT polarity verification results on the high-voltage side of the transformer (main transformer) is low, and there are certain risks when the main transformer is put into operation. In serious cases, it may cause the protection device to malfunction or refuse to operate, affecting the safe and stable operation of the power system

Method used

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  • The method of verifying the ct polarity of the high voltage side of the main transformer by using the excitation inrush current
  • The method of verifying the ct polarity of the high voltage side of the main transformer by using the excitation inrush current
  • The method of verifying the ct polarity of the high voltage side of the main transformer by using the excitation inrush current

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Embodiment 1

[0120] Example 1, using a real-time digital simulator RTDS (Real Time Digital Simulator) to build a simulation model, the parameters are set as follows: a three-volume transformer with a capacity of 180MVA and a voltage of 220kV / 110kV / 35kV, the connection mode is YY△, and the high-voltage side of the transformer is empty. Load closing initial closing angle α 0 =00, residual magnetism

[0121] In the case of correct CT wiring, such as Pic 4-1 As shown, the simulation waveform of the three-phase voltage on the high side of the transformer is a sinusoidal periodic function, the three-phase phase difference is 1200, the period is 20ms, and the amplitude is 81.6V. Such as Figure 4-2 As shown, the simulation waveform of the three-phase current on the high-voltage side of the transformer is a non-sinusoidal periodic function, and contains attenuated DC components and multiple harmonics. 0.06A. Such as Figure 4-3 As shown, the instantaneous reactive power simulation waveform...

Embodiment 2

[0123] Example 2, when the on-site transformer in Han Village, Shouyang County, Jinzhong City, Shanxi Province is charged with no load, and the on-site CT wiring is correct, such as Figure 6-1 As shown, the three-phase voltage waveform on the high-voltage side of the transformer is a sinusoidal periodic function, and the three-phase phase difference is 120 0 , the period is 20ms, and the amplitude is 81.6V. Such as Figure 6-2 As shown, the three-phase current waveform on the high-voltage side of the transformer is a non-sinusoidal periodic function, and contains attenuated DC components and multiple harmonics. a. Such as Figure 6-3 As shown, the instantaneous reactive power waveform on the high-voltage side of the transformer is a non-sinusoidal periodic function, and contains attenuated DC components and multiple harmonics. The period is 20ms, and the waveform is biased above the time axis. Such as Figure 6-4 As shown, the average waveform of the reactive power at th...

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Abstract

The invention discloses a method for checking the polarity of CT on the high-voltage side of the main transformer by using the excitation inrush current, and the technical problem to be solved is to conveniently check whether the polarity of the CT connection on the high-voltage side of the main transformer is correct. The method of the present invention is: collect the three-phase secondary voltage and the three-phase secondary current of the main transformer high-voltage side bus bar, calculate the three-phase instantaneous reactive power, calculate the average value of reactive power of one cycle, and the average value of reactive power>0 , Judging that the CT connection of the current transformer is correct. Compared with the prior art, the present invention uses the excitation inrush current generated by the transformer and the high-voltage side voltage of the main transformer to calculate the instantaneous reactive power, and then calculates the instantaneous reactive power average value in a unit cycle, and the reactive power average value is greater than zero , it is considered that the CT wiring is correct, otherwise, it is considered that the CT wiring is wrong, and the circuit breaker on the high-voltage side of the main transformer is tripped to achieve the purpose of verifying the polarity of the CT on the high-voltage side of the main transformer, and to prevent the protection equipment from malfunctioning or refusing to operate due to incorrect wiring of the CT. , improve the reliability of substation operation.

Description

technical field [0001] The invention relates to a relay protection method of an electric power system, in particular to a method for checking the polarity of a current transformer on the high-voltage side of a main transformer in a substation. Background technique [0002] Current transformer CT is the main equipment in the power system. Its main function is to transform the large current of the primary system into the small current of the secondary system for use in circuit devices such as measurement and protection. It can timely and accurately reflect the operation of the primary system and facilitate operation. The department's protection, control and monitoring of the power system play an important role in preventing the expansion of the fault range and ensuring the reliable operation of the system. If the CT polarity wiring on the high voltage side of the transformer is wrong, it is very easy to cause malfunction or refusal of the transformer protection equipment, whic...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R31/72
CPCG01R31/72
Inventor 李本瑜王冰清赵明刘宏君游昊石磊石恒初张琳波方毅陈剑平杨远航张鑫李源辉
Owner YUNNAN POWER GRID