Study of microgap discharges and television interference

Disturbing discharges are observed on power lines with inadequate design and maintenance standards. The nature of these discharges is different from that of conductor corona and is more frequently observed on distribution lines than on transmission lines. Electromagnetic noise causing not only Radio Interference (RI) but also Television Interference (TVI) is the consequence of such discharges.;On the basis of laboratory measurements, the properties of microgap discharges were investigated for a typical point-to-plate electrode geometry in the time domain and in the frequency domain. In particular, the statistical characteristics of microgap discharges were studied in this thesis. A microcomputer-based measurement system was set up. For the sake of getting new parameters to assess television interference caused by microgap discharge, the analog rectified intermediate frequency (IF) signal was taken from the R & S ESVP Test Receiver, and recorded by a digitizer-controller system. Amplitude Probability Distribution (APD) and Noise Amplitude Distribution (NAD) measurement results were obtained from the recorded data. Television interference caused by microgap discharge was investigated in the laboratory. The collected results clearly show that the applied voltage, the voltage source, the gap geometry and gap size affect the interference observed on the television screen. NAD is shown to be a better measure to assess television interference caused by microgap discharge.;A microgap discharge equivalent circuit is proposed and developed. The simulation results show that the proposed equivalent circuit gives better results than existing equivalent circuits.;Finally, the engineering significance of these findings with respect to characteristics of electromagnetic noise and design and maintenance of power lines is commented upon.