State Grid Corporation of China

Xj Group Corporation

Xj Electric Co., Ltd

Xuchang Xj Software Technology Co., Ltd.

Jiansong Zhao

Chuankun Ni

Xu Li

Yingying Xi

Baowei Li

Shasha Hu

Feng Xiao

Jidong Huang

Xin Shi

Xintao Dong

Jirui Chen

Yun Gong

Dongxiao Yao

Lijuan Lv

Heke Ma

Maojun Deng

Jingli Zhang

Ziqiang Jiang

Quanxia Ma

Yantao Qiao

Yanmei Tang

Yu Tang

Wenzheng Li

Huizhen Hao

Liping Meng

The present disclosure relates to a method for preventing a maloperation of differential protection of an optical fiber caused by saturation of a single Current Transformer (CT) of 3/2 connection. By applying a combination of the differential judgment and the sub-CT current judgment, reliable identification of internal and external faults is ensured, and the problem of misjudging of the internal fault as the external fault can be prevented as well.

Method for preventing differential protection maloperation of optical fiber caused by saturation of single CT of 3/2 connection

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.

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

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Xuchang, China

Jiansong Zhao