Computer-aided on-line detection of partial discharge in power transformer

A computer-aided online detection system of partial discharges (PDs) in power transformers is described. The impulse electrical signals of PD are detected with a current transducing unit and the acoustic emission signals of the PD are detected with acoustic transducing units. Various detected analog signals are transmitted with an optical fiber transmission system to the data-acquisition circuit and microcomputer. The frequency-division multiplexing technique is applied to transmit four channels of analog signals in one optical fiber. The amplitudes of detected electrical and acoustic signals are acquired and transmitted to the microcomputer with DMA. The microcomputer is used to store and to process the acquired signals. Two kinds of online PD calibration methods were developed, i.e. the transformer bushing method and the impulse charge couple method. With these methods various functions of this detection system are realized, such as offline and online PD detection, online PD calibration, recognition of electromagnetic interference, and location of the PD source. Onsite experiments with this system were performed in several power substations, and the test results were satisfactory