Real-time HV OHTL sag monitoring system based on power line carrier signal behaviour
De Villiers, Wernich (2005-12)
Thesis (PhD))--University of Stellenbosch, 2005.
ENGLISH ABSTRACT: A new method of measuring the change in the average height of phase conductors above the ground plane of High Voltage (HV) Overhead Transmission Lines (OHTLs) was discovered in 1999, at Stellenbosch University. The new method, called Power Line Carrier-Sag (pLC-SAG), measures average overhead conductor height variations in real-time by exploiting high frequency signal propagation characteristics on the existing PLC system. The novelty of the newly discovered PLC-SAG system naturally led to a thorough testing and investigation of the technique. This thesis explains the methodology used to produce unique experimental data, which has indeed proven that the average height of an OHTL can be tracked very accurately via the PLC-SAG technique for continuous periods. As the experiments on two live 400 kV transmission lines in South Africa were being undertaken, a serious concern regarding the new technique arose. Major HV Station impedance variations seemed to influence the PLC system and clouded the interpretation of PLC-SAG recorded data. Such HV Station impedance variations typically occur only a few times per year. A new Power Line Carrier Impedance (PLC-IMP) technique was then discovered, by which these changes could be monitored. No structural changes to the existing PLC-SAG system were required for this technique. This was seen as a major breakthrough in the presented study. Not only does this newly established technique make it possible to develop a stable PLC-SAG system, but also a potential real-time condition monitor application. Its use on PLC systems has been proposed to the main Power Utility in South Africa.
AFRIKAANSE OPSOMMING: Nuwe metode om die veranderinge in die gemiddelde hoogte bo grondvlak van die fasegeleiers van hoogspanning oorhoofse transmissielyne te meet is in 1999 by die Universiteit Stellenbosch ontdek. Hierdie uitvindsel staan bekend as die Power Line Carrier Sag (pLC-SAG) metode en dit meet veranderinge in oorhoofse geleier hoogte intyds deur benutting van die eienskappe van hoëfrekwensie sein voortplanting op die bestaande hoogspanning oorhoofse transmissielyne. Die nuutuitgevonde PLC-SAG stelsel is natuurlik onderworpe aan deeglike toetsing en ondersoek van die tegniek. Hierdie proefskrif verduidelik die metodiek gebruik, waarvolgens unieke eksperimentele data verkry is wat bewys dat die gemiddelde hoogte van 'n hoogspannings oorhoofse transmissielyn inderdaad baie akkuraat gemeet kan word, oor lang ononderbroke tydperke. Tydens die eksperimente en ondersoek op twee lewendige 400kV transmissielyne in Suid-Afrika is 'n ernstige probleem gewaar wat die vatbaarheid van die tegniek in gevaar gestel het. Groot verskille in impedansie by hoogspanningstasies beinvloed die hoogspanning oorhoofse transmissielyn stelsel en versteur die interpretasie van die PLC-SAG data wat opgeneem is. Sulke groot impedansie verskille kom tipies slegs 'n paar keer per jaar by 'n stasie voor. 'n Tweede nuwe tegniek, die sogenoemde Powerline Carrier Impedance (PLC-IMP) tegniek, is toe ontdek wat hierdie veranderinge kan monitor en dus die intydse hoogspannings oorhoofse transmissielyne impedansie metings moontlik maak. Geen struktuurverandering van die bestaande PLC-SAG stelsel is nodig vir gebruik van die PLC-IMP tegniek nie, en dit word beskou as 'n groot deurbraak in die studie wat hier aangebied word. Hierdie tegniek het teweeggebring nie slegs 'n stabiele PLC-SAG stelsel nie, maar 'n potensiele intydse monitor vir gebruik op hoogspannings oorhoofse transmissielyn stelsels. Die tegniek is voorgestel aan die grootste kragvoorsiener in Suid-Afrika vir gebruik op hul stelsels.
Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/4872
Doctoral Degrees (Electrical and Electronic Engineering)