A new wideband transformer partial discharge online monitoring system

This paper introduces a wideband transformer partial discharge (PD) online monitoring system which can be used under the substation environment. It consists of wideband current sensors, amplifiers, filters, a digital oscilloscope and a computer. The wideband current sensors´ measuring ranges from 20kHz to 40MHz; the signal amplifiers´ frequency bandwidth is 0 ~ 100MHz, the signal gain of it can reach 100 times; the digital oscilloscope is used to acquire and display the PD pulse signal, the sampling rate is set to 100Msps, and the data length is 100M; the computer controls the whole data collection process, and the software platform was written using the Labview. Use a power frequency cycle (20 ms) as a unit for data acquisition. The data collected by the oscilloscope gets into the computer through the USB interface, after filtering, pulse extraction, pulse equivalent time-frequency parameter calculation and other processes, and then conducts the next data collection cycle. After the acquisition of data from 50 power frequency cycles, doing pulse clustering analysis based on the pulse of the equivalent time-frequency parameters. After the completing of pulse clustering analysis, conducts the same kind of pulse of statistical analysis, exclusion of pulse disturbance and fault diagnosis. It can effectively reflect the internal PD change rule under the actual working state of the transformer, can judge the severity of the transformer internal discharge to determine whether maintenance or not, then effectively improve the capacity of safe operation and reduce the maintenance costs.