Development of an Advanced diagnosis employable to Gas insulated power apparatus

Abstract

Recently, the number of installation using Gas insulated switchgears(GIS) and Gas insulated transformer(GITr) has been increased ascribed to their high reliability in terms of insulation and reduced dimension occupying limited space at the substation. However, unexpected or sudden failures throughout their services at the power grid have been noticeably reported. Therefore, in order to avoid such inconveniences, the detection and analysis of Partial discharges of GIS and GITr has been developed as one of the promising diagnosis techniques at many a research group in the world. But the important parts regarding the noise reduction of PD signals and acquisition of phase information related to the power grid voltage have not been clearly disclosed. In this work, PD signals in UHF band have been detected and analyzed for developing relevant diagnosis technique. For the analysis, our CAPD method, proposed in 2000, is now combined with TF map for the pattern analysis. By applying this method, the nature of vital defects introducible into these type of apparatus could be identified. Besides, regarding the PD location, we have also proposed a new method by merging DWT (Discrete wavelet transform) into Time of flight method in order to eliminate the nosie and then its application to the full scaled 154kV GIS at the KEPCO substation has been investigated.

The summary of our results are as follows. 1. An advanced PD diagnosis method is developed by combining our CAPD in 2000d with TF map in order to improve the reliability of PD recognition. This method enables efficiently to identify the nature of PD sources under consideration. 2. PD Location software including relevant tool for noise discrimination have been developed. The statistically deduced propagation velocity of EM wave in GIS is obtained by experimental investigations to reduce the errors in distance of PD location. These results enable us to realize finding of the PD location within 3.0% for the case of EBG connected with GIS in trouble at KEPCO substation.

Consequently, our work could be used for the commercial purpose of PD location while elaborated field experiences are required for the on-site applicability of "Advanced CAPD".