Statistical Characteristics of Electromagnetic Interference Signals for High Frequency Current PD Detection in Substations

Abstract

Complex electromagnetic interference is a most important cause for wrong alarming and failing to alarm online high frequency current partial discharge (PD) detection in substation, and also a key bottleneck for the development of online PD detection. Therefore, typical substations in geographical position and voltage level were selected as the objects of research, and high frequency current PD detection method and digital oscilloscope were used to systematically study the characteristics of electromagnetic interference signal in the substation in time-domain, frequency-domain, and statistics by field testing. Moreover, the location of the interference signal source was performed. It is found that the periodic interference signal and the external discharge of HV equipment in substations are the main forms of electromagnetic interferences for PD detection. The large-amplitude electromagnetic interference signal existing at the station will adversely affect the partial discharge detection. Especially the pulse interference signal, whose time-frequency characteristic is similar to the partial discharge signal, it is very easy to cause misjudgment of the detection system.