PD signal propagation characteristics in GIS and its location system by frequency components comparison

Propagation characteristics of partial discharge signal in GIS were investi gated in a laboratory and at a 300 kV underground substation. The laborator y test indicates that signal damping can be attributed to two major mechani sms; reflection due to irregularity of characteristic impedance such as spa cers, and the mode shift from TEM to TE or TM. Tests at the substation show that the signal damping phenomena are independent of propagation direction , and the mode shift gives rise to a large signal damping. The major higher mode seems to be TE11. Amplitudes of observed waveforms using narrow-band filters that agree well with the corresponding frequency components observe d with a spectrum analyzer, show irregular or random behavior depending upo n their observation point. This indicates that narrow-band filters do not s eem to be suitable for a partial discharge location system by a frequency c omponent comparison, and the realizability of the system using broadband fi lters instead is discussed.