Effects of Common In-Service Defects of Different Insulators on Radio Frequency Interference Emission from 765 kV Insulators String

Abstract

Worldwide utilities are preferring Ultra-High Voltage (UHV) transmission lines for transmitting electric power from generating stations to load centres. This long-distance UHV transmission line uses porcelain, glass and composite insulators. Fault-free operation of these insulators is vital to provide reliable service to consumers. Any defects on these insulators may lead to outages and affect the reliability of the supply system. To ensure reliability, utilities are continuously monitoring the condition of transmission line insulators. Nowadays in addition to providing reliable and quality power to the consumers, the utilities are keen on measuring and reducing The Radio Frequency Interference (RFI) from transmission lines. Under normal operating conditions, the RFI of the insulator string may be less than the specified limit. However, evolving inservice defects and deposition of pollutants on the surface of the insulator may increase the RFI level, sometimes it may exceed the specified limit also. This higher emission may affect the operation of nearby other electronic equipment. In this present work, an attempt is made to measure and compare RFI from healthy and defective 765 kV single I suspension string in the shielded indoor laboratory. It was observed that defects and pollutants deposited on insulators have induced corona/spark or gap discharges at the operating voltage level, which in turn increases the intensity of RFI.