Partial discharge in light-load 161KV power transformer

The distributed pick-up coils are used to detect the radiating frequency (RF) from partial discharge. The pick-up coils are directly attached to the surface of a 161 KV power transformer to increase the sensitivity of PD signal detection. The partial discharges occur in the oil, then propagate to the metal tank where they induce the eddy current. Then, the PD impulse propagates to the detecting coils which induce the PD signal. It is found the PD effect is weak in light-load conditions. From the time domain measurement, the location and propagation of the individual partial discharge can be decided. However, the degradation of the oil still can not be clearly identified. Using spectrum analysis, there are many partial discharge impulses that occur over 10 MHz in the deficient transformer. But, only the conventional continuous spectrum appears in the good transformer. The results are verified by the oil gas analysis.