A proposal for Hybrid PD sensor identifying absolute distance from PD source

In this paper, the authors proposed a Hybrid PD (AE) sensor which could tell us an absolute distance from PD source. The proposed sensor installed at one fixed position of power transformer tank wall could detect HF signal and ultrasonic one simultaneously. Ignoring faster arrival time of HF signal, an approximated absolute distance from PD source could be derived easily. Moreover, applying time series measurement to the scheme, a pair of PD signals could enable us to discriminate true PD signals from noise spectra. This paper also shows the laboratory experimental results from an oil transformer of 6 kV.