| Transformer is one of the most important equipment in power system, its reliability directly affects the safe operation of power grid. The on-line monitoring of partial discharge for its insulating properties in real-time can reflect the condition of transformers’internal insulation degradation continuously, is one of the important means to master the insulation condition of transformer. Compared with the conventional pulse current method, the wideband pulse detection current method has the advantages of wider measurement bandwidth, higher sensitivity and contains more information of partial discharge that can reflect the original pulse current characteristics of partial discharge pulse more accurately, it makes the use of pulse current waveform analysis method to separate the signal and noise possible, therefore be studied in this paper.This paper developed a wideband partial discharge on-line monitoring system that can be used in the substation environment, including wideband current sensors,50Hz power frequency phase generator, wideband signal amplifiers, filters, a digital oscilloscope and a computer. The propagation law and coupling mechanism of wideband partial discharge pulse in the real transformer are studied on3three-phase-double-winding real transformers and1three-phase-three-winding transformer model in this paper, which can provide guidance for partial discharge on-line monitoring and positioning of transformers.In this paper, we collected the partial discharge signals from several transformers’core grounding lines within the substation of somewhere using the wideband partial discharge on-line monitoring system, and then analyzed the signals’ frequency spectrum of each substation in order to study the law of partial discharge in frequency domain. Then we also conducted a statistical analysis based on the phase distribution, and identified the types of discharge which is suspected to be real partial discharge based on the equivalent time-frequency method. |
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