Prevention method of abnormal action protection of UHV regulating compensation transformer with no-load input

Patent metadata

Field	Value
Publication number	US-10090670-B2
Application number	US-201615076664-A
Country	US
Kind code	B2
Filing date	Mar 22, 2016
Priority date	Mar 22, 2016
Publication date	Oct 2, 2018
Grant date	Oct 2, 2018

Abstract

The present invention relates to a prevention method of abnormal action protection of UHV regulating compensation transformer with no-load input, the prevention method includes: first determining a value of differential current of regulating compensation transformer, if the value of differential current is smaller than a pre-setting threshold, then, identifying whether an uninterruptible point of differential current waveform meets an pre-setting regulation according to original value of differential current or sampling value of differential difference current, and determining comprehensively whether the regulating compensation transformer is in no-load input or in fault directly with a value of second harmonic content of logic differential current together; if a value of differential current before pre-setting period is larger than the pre-setting threshold, the regulating compensation transformer is diagnosed to have external CT saturation, determining comprehensively whether the regulating compensation transformer is in no-load input or in fault by using result of the uninterruptible point after delaying and the value of second harmonic content of logic difference together, and corresponding inactivating or activating differential protection. By using the value of differential current before a pre-setting period, characteristics of the original value of differential current and the sampling value of differential difference current, and second harmonic inrush to discriminate an pre-setting regulation, the present invention can avoid the regulating compensation transformer occurring abnormal action when no-load switching transformer of UHV substation is charging, and isolating the fault quickly when the no-load switching transformer is in fault state.

First claim

What is claimed is:

1. A prevention method of abnormal action protection of UHV regulating compensation transformer with no-load input, being characterized in that the prevention method includes the steps of:
1). calculating an effective value of differential current for UHV regulating compensation transformer before a pre-setting period, then determining whether the effective value is larger than a pre-setting threshold, if the effective value is smaller than the pre-setting threshold, the UHV regulating compensation transformer is diagnosed to have internal fault, if the effective value is larger than the pre-setting threshold, the UHV regulating compensation transformer is diagnosed to have external CT saturation;
2). if the UHV regulating compensation transformer being diagnosed to have internal fault, determining whether an uninterruptible point meets an pre-setting regulation according to characteristics of original sampling value of the differential current and/or sampling value of differential difference current directly, if the UHV regulating compensation transformer being diagnosed to have external CT saturation, determining whether the uninterruptible point meets the pre-setting regulation after a pre-setting period;
3). determining whether the UHV regulating compensation transformer is in no-load input state according to the ratio of second harmonic to fundamental wave of the differential current;
4). if the uninterruptible point meets the pre-setting regulation and the UHV regulating compensation transformer being in no-load input state, activating differential protection, otherwise inactivating the differential protection.

2. The prevention method of abnormal action protection of UHV regulating compensation transformer with no-load input of claim 1 , being characterized in that using a discrimination formula to determine the effective value in the step 1), the discrimination formula is:
I dNT >0.2* I e
wherein I dNT is an effective value of differential current before an N*T period, T is a sampling period, N is an natural number, and I e is a base current value of differential protection for the UHV regulating compensation transformer.

3. The prevention method of abnormal action protection of UHV regulating compensation transformer with no-load input of claim 2 , being characterized in that using a discrimination formula to determine the uninterruptible point according to characteristics of original sampling value of the differential current in the step 2), the discrimination formula is:

{

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{

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2
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Assignees

• Xj Group Corp
• Xj Electric Co Ltd
• Xuchang Xj Software Tech Ltd
• State Grid Corp China

Inventors

• Chen Jirui
• Zhao Jiansong
• Gong Yun
• Deng Maojun
• Ni Chuankun
• Yao Dongxiao
• Ma Heke
• Lv Lijuan
• Li Baowei
• Li Xu
• Huang Jidong
• Xiao Feng
• Hu Shasha
• Zhang Jingli
• Xi Yingying

Classifications

• H02H7/045 Primary

  Differential protection of transformers · CPC title