Abstract
Abstract : With the recent purchase of Transnet Locomotives, for every batch of Locomotives that are delivered to Transnet before any deployment they have to undergo through acceptance tests by Locomotive technology department. The locomotive technology department tested these locomotives in different regions of the country in different power networks and it was reported that unacceptable frequencies (harmonics) were experienced which interfered with operation of the locomotives on both AC and DC network systems. The research to investigate the cause of these frequencies was launched to find where these frequencies were emanating from as they were purportedly claimed to be from the traction substations during the conversion of high voltage to low voltage. The approached used in resolving this problem was to understand the fundamentals behind the harmonics, as to what influence them and the mitigation methods. And to understand what the standards (IEEE 519 and NRS 048) stipulate with regards to limits on harmonics. The focus was narrowed on the conversion of high voltage equipment to low voltage equipment (main transformers, rectifiers, auxiliary transformers) on substations and the maintenance if this contributed to the harmonic effects on locomotives. The outcomes on the investigation conducted on both AC and DC were: on 3kV DC traction substations, the harmonics on signalling power supplies that runs parallel with the 3kV DC line were found to be very high. This was due to the failure of spark gaps on the mast-poles and switching structures. On the 25kV AC traction substations, the harmonics were found to be within limits and the cause was found to be the locomotives.
M.Ing. (Engineering Management)