Real-time HV OHTL sag monitoring system based on power line carrier signal behaviour

[摘要] ENGLISH ABSTRACT: A new method of measuring the change in the average height of phaseconductors above the ground plane of High Voltage (HV) OverheadTransmission Lines (OHTLs) was discovered in 1999, at StellenboschUniversity. The new method, called Power Line Carrier-Sag (pLC-SAG),measures average overhead conductor height variations in real-time byexploiting high frequency signal propagation characteristics on theexisting PLC system.The novelty of the newly discovered PLC-SAG system naturally led to athorough testing and investigation of the technique. This thesis explainsthe methodology used to produce unique experimental data, which hasindeed proven that the average height of an OHTL can be tracked veryaccurately via the PLC-SAG technique for continuous periods.As the experiments on two live 400 kV transmission lines in South Africawere being undertaken, a serious concern regarding the new techniquearose. Major HV Station impedance variations seemed to influence thePLC system and clouded the interpretation of PLC-SAG recorded data.Such HV Station impedance variations typically occur only a few times peryear.A new Power Line Carrier Impedance (PLC-IMP) technique was thendiscovered, by which these changes could be monitored. No structuralchanges to the existing PLC-SAG system were required for this technique.This was seen as a major breakthrough in the presented study. Not onlydoes this newly established technique make it possible to develop a stablePLC-SAG system, but also a potential real-time condition monitorapplication. Its use on PLC systems has been proposed to the main PowerUtility in South Africa.

[发布机构] Stellenbosch University