Handling and Analysis of an abnormal 220kV GIS Power Frequency Withstand Voltage Test

Ge Shaojie, Dong Wanguang, Chen Hu, Zhang Zhonglei
HIMALAYAL - SHANGHAI - CHINA

Abstract: Through an abnormal 220kV GIS power frequency withstand voltage test, main causes for breakdown and flashover of the test are analyzed and corresponding methods to handle and preventive measures are put forward.  

Key words: GIS, power frequency, electrode breakdown, surface flashover

1.Introduction
GIS has many advantages, such as reliable power supply, good safety, adaptive to bad environment and small floor area etc. Therefore, it is increasingly used in the electric power system. In order to ensure safe and reliable operation of GIS, during the installation, expansion and maintenance, withstand voltage test should be conducted according to relevant regulations and standards to check insulation performance of GIS as a whole and all the components, ensuring safe and steady operation of power grid after being put into use.

2.Test Process  
The power frequency voltage test was conducted for some 220kV PT interval GIS in December 2012. The GB 7674-2008 Gas-insulated Metal-enclosed Switchgear for Rated Voltage 72.5kV and above stipulates that standard applied voltage for 220kV GIS delivery AC voltage test is 460kV. During the withstand voltage test process, phase A, B and C discharge. Detailed descriptions are as follows: when the voltage of phase A rises to 416kV, the discharge occurs and withstand voltage discharge repeats; check its appearance and wiring, and there is no abnormal condition; and then conduct rising test of the equipment, the test is normal. As for phase B, 460kV keeps the voltage for 35 seconds and then the discharge occurs and withstand voltage discharge repeats; when the voltage of phase C rises to 440kV, the discharge phenomena occurs and withstand voltage discharge repeats. 

3.Analysis and Handling
Generally, except the influence of external factors such as test equipment and test method, internal structure design, electrode surface condition and conducting particles are main factors which causes the discharge and flashover of GIS.