The health status of the potential transformer(PT)secondary circuit in a substation is crucial for the reliability of relay protection actions,making it difficult to identify grounding faults in PT secondary circuit cables and select the grounding branch cable.To address this challenge,this article introduces a line selection scheme for identifying grounding faults and PT cable grounding branches using transient information of branch cable grounding current.The Hilbert transform to is employed to obtain the transient information that filters out the fundamental frequency component,and the estimated values of three random variables-decaying DC component,high-frequency energy,and branch cable current similarity-are calculated.The Copula function is used to calculate the joint probability distribution density function of the three indicators,and the risk of grounding faults in each branch cable is calculated to select the grounding branch.Finally,a simulation model is built to verify the secondary circuit cable branch grounding selection scheme.The results show that the fusion fault criterion based on the Copula proposed in this paper is not affected by fault types,and can accurately identify multiple cable fault branches,verifying the effectiveness and adaptability of the scheme.
关键词
PT二次回路/故障选线/基频移位/联合概率分布/Copula函数
Key words
PT secondary circuit/fault line selection/fundamental frequency shift/joint probability distribution/Copula function
维普
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