Browsing by Author "De Villiers, Wernich"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- ItemPrediction and measurement of power line carrier signal attenuation and fluctuation(Stellenbosch : Stellenbosch University, 2001-12) De Villiers, Wernich; Cloete, J. H.; Herman, R.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.ENGLISH ABSTRACT: A frequency domain Power Line Carrier (PLC) simulation program, with the ability to simulate signal attenuation including the coupling equipment, was developed. This simulation program was put to the test against the independent program of Professor L.M. Wedepohl and against practical field measurements. The predictions of the two programs were in precise agreement for a wide range of input parameters. Results from the field tests and predictions also showed close agreement. Further investigations, applying the simulation program, explained how ground conductors and soil resistivity influences PLC signal propagation. An experiment, which was developed to monitor PLC signal attenuation, was installed on the PLC system between Koeberg power station and Acacia substation, both near Cape Town. Data logged continuously over 28 days, indicated measurable and deterministic PLC signal attenuation variations with typical time constants of a few hours. Simulations of the PLC system indicated that the signal amplitude variations were influenced by changes in the height above the ground plane of the phase conductor. This significant finding creates the possibility to obtain real time knowledge of the sag of an Over Head Transmission Line (OHTL) by exploiting an operational PLC system. The knowledge about real time sag can be used in economical dynamic ampacity control systems. The practical and financial benefits to the electricity supply and distribution industry can be significant.
- ItemReal-time HV OHTL sag monitoring system based on power line carrier signal behaviour(Stellenbosch : University of Stellenbosch, 2005-12) De Villiers, Wernich; Cloete, J. H.; University of Stellenbosch. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.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.