Fault prediction relay for cables and overhead lines

This research outlines in detail adding a new dimension to the alreadyexisting protection techniques, this of predicting single line to ground faults onoverhead transmission lines and underground cables. This new concept of faultprediction ,considered to be unprecedented ,adds a fonn of ArtificialIntelligence to the already existing traditional protection schemes for overheadtransmission lines and underground cables. The prediction system is a threestage integrated system comprising a fault prediction relay, an optical fibercommunication link to transmit the alarm signal to the main station and amicroprocessor based identification system to identify the faulty region. Theprediction theory is based on the continuous monitoring and analysis of theleakage currents on transmission line insulators, and of internal discharges inair voids found in underground cable junctions. The level and frequency ofleakage currents and internal discharges are considered the back bone of thedecision making process by which the insulating properties of transmissiontower insulators and cable junctions may be assessed.The present thesis discusses in detail the following topics:1- Performance of overhead transmission line insulators under pollutionconditions.2- The performance and operation of an integrated fault prediction system.3- Flashover mechanism on overhead transmission line insulators.4- The different criteria for assessing the degree of pollution of overheadline insulators .5- Leakage current criterion for assessing the condition of overhead lineinsulators .6- Leakage current wave form and characteristics.7- Analog and Digital electronics building blocks for static relays.8- Design details of a fault prediction relay .9- Laboratory realisation ,complete wiring scheme and testing of the faultprediction relay.