The research work conducted and presented forward in this document is the evaluation of real time values obtained using three recording devices at two independent locations and implementing them as recorder devices in Eskom’s power system. The research work conducted was presented at an IEEE International Conference (ICIT2013) and Appendix A shows the accepted paper presented. A derived model within a simulation software package known as DIgSILENT PowerFactory is created and Electromagnetic Transient (EMT) studies are performed and then compared to the real time values obtained using the OMICRON CMC 356’s. Transformers are normally energised via a circuit breaker which is controlled by an auxiliary closing contact. By applying system voltage at a random instant in time on the transformer windings may result in a large transient magnetizing inrush current which causes high orders of 2nd harmonic currents to flow under no load conditions. A philosophy known to mitigate these currents is to energise the transformer by controlling each individual phase 120 degrees apart with the first pole closing at the peak on the voltage waveform. Transients produced due to 500MVA transformers been introduced into the power system at a certain space in time can cause nuisance tripping’s at the particular location where the respective transformer is energised. OMICRON EnerLyzer is the software tool used for the Comtrade recordings at both locations. Four independent case studies are generated within EnerLyzer software and the relevant Comtrade files are extracted for the four independent case studies relative to Transformer1 and Transformer2 switching’s. TOP software, which is a mathematical tool used to analyse Comtrade files, is then used to analyse and investigate the four case studies. Results from DIgSILENT PowerFactory are then generated according to the derived model. The results extracted depict three scenarios, indicating a power system that is weak, strong and specifically a power system that correlates to the actual tripping of a Static VAr Compensator (SVC). The results are all formulated and then evaluated in order to produce a conclusion and bring forward recommendations to Eskom in order to effectively ensure the Dedisa/Grassridge power system is reliable once again.

A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering. / The sudden failure of oil paper-insulated current transformers has become a problem of considerable concern due to the cost of the resulting destruction, and danger to personnel. The aim of the dissertation is. to determine the most suitable method of detecting lncipient faults in current transformers, test this method on an experimental current transformer, and finally implement this technique in a low cost on-line monitor. A literature survey indicated that hydrogen gas-in-oil on-line monitoring would be the most suitable technique.(Abbreviation abstract) / Andrew Chakane 2019

abstract: Optical Instrument Transformers (OIT) have been developed as an alternative to traditional instrument transformers (IT). The question "Can optical instrument transformers substitute for the traditional transformers?" is the main motivation of this study. Finding the answer for this question and developing complete models are the contributions of this work. Dedicated test facilities are developed so that the steady state and transient performances of analog outputs of a magnetic current transformer (CT) and a magnetic voltage transformer (VT) are compared with that of an optical current transformer (OCT) and an optical voltage transformer (OVT) respectively. Frequency response characteristics of OIT outputs are obtained. Comparison results show that OITs have a specified accuracy of 0.3% in all cases. They are linear, and DC offset does not saturate the systems. The OIT output signal has a 40~60 μs time delay, but this is typically less than the equivalent phase difference permitted by the IEEE and IEC standards for protection applications. Analog outputs have significantly higher bandwidths (adjustable to 20 to 40 kHz) than the IT. The digital output signal bandwidth (2.4 kHz) of an OCT is significantly lower than the analog signal bandwidth (20 kHz) due to the sampling rates involved. The OIT analog outputs may have significant white noise of 6%, but the white noise does not affect accuracy or protection performance. Temperatures up to 50oC do not adversely affect the performance of the OITs. Three types of models are developed for analog outputs: analog, digital, and complete models. Well-known mathematical methods, such as network synthesis and Jones calculus methods are applied. The developed models are compared with experiment results and are verified with simulation programs. Results show less than 1.5% for OCT and 2% for OVT difference and that the developed models can be used for power system simulations and the method used for the development can be used to develop models for all other brands of optical systems. The communication and data transfer between the all-digital protection systems is investigated by developing a test facility for all digital protection systems. Test results show that different manufacturers' relays and transformers based on the IEC standard can serve the power system successfully. / Dissertation/Thesis / Ph.D. Electrical Engineering 2010

A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering / The sudden failure of oil paper-insulated current transformers has become a problem of considerable concern due to the cost of the resulting destruction, and danger to personnel. The aim of the dissertation is to determine the most suitable method of detecting incipient faults in current transformers, test this method on an experimental current transformer, and finally implement this technique in a low cost on-line monitor. A literature survey indicated that hydrogen gas-in-oil on-line monitoring would be the most suitable technique.(Abbreviation abstract) / Andrew Chakane 2019

A substation must be properly protected against lightning and other external effects to the equipment in the station or staff, for that we use relay protection. They should also protect against internal errors which may occur as ground faults. There are different types of protection relays, but most common are overcurrent-, distance-, residual current- and differential protection. The purpose of this thesis was to deepen our knowledge of relay protection and to use the theoretical knowledge we got from the university studies in the work process. In the process we discovered which parameters were the most essential and calculated these for all relay protections on the substation. We also carry out a comparison between two brands of relay protection, ABB and Alstom. During our work we will test and simulate the over-current relays in a program called NEPLAN, the program will also calculate the fault currents. It was also supposed to test the other protection types, but we were limited to over-current protection when the software license didn´t apply to the other. In our work we will include much theoretical material with information about the components around the protections and substation and the calculations that’s included.

MSc (Eng), School of Electrical and Information Engineering, Faculty of Engineering and the Built Environment

Polychlorinated Biphenyls (PCBs) were seen as a significant engineering advance when first commercially produced in 1929. They were used as insulators and cooling fluids in electrical transformers and capacitors. There are 209 PCB congenors that are chemically and thermally stable with low inflammability and reactivity. However,they are also highly toxic, suspected carcinogens and bioaccumulate in the food chain. Due to these characteristics they are listed by the United Nations as one of the sixteen worlds persistent organic pollutants POPs). By international agreement, undertaken by the UN, the production of PCBs has been banned and gradually their use will be phased out. Several tests and procedures are discussed in some detail in this research. / Master of Science (Hons)

A possible lower cost alternative to medium voltage line arresters and parallel-connected surge arresters is the use of parallel-connected spark gaps across a metal oxide surge arrester. The function of the spark gap is to protect the transformer when the surge arrester fails. Clearly the breakdown voltage characteristics of such a gap need to be carefully co-ordinated with the transformer insulation and those of the arrester. Eskom (Electricity Supply Commission of South Africa) is the national electrical utility that provides the generation, transmission and distribution of electricity in South Africa. The majority of Eskom's electricity reticulation is done with either 11 kV or 22 kV electrical overhead networks. An unacceptable number of Eskom's pole mounted power transformers on these networks have failed over the past few years. The high failure rate of Distribution transformers in Eskom, South Africa has previously been highlighted and investigated in an MSc thesis, the most recent being the thesis completed at the University of KwaZulu-Natal by Chatterton [6]. The thesis proposed possible solutions to the problem but experienced high implementation costs and particular technical issues before widespread implementation could prove viable for the Distribution System. The average transformer failure rate for the Distribution Eastern Region for the twelve month period taken as a moving average was calculated to be 5.19 % per annum at the end of November 2005 and 3.84 % at the end of November 2006. (Eskom Eastern Region Plant report, November 2006). International norms seem to indicate that a transformer failure rate of between 0.5% and 1.0% per annum is acceptable, Chatterton [6]. The reason for the increased failure rates during 2005 was attributed to incorrect Ground Lead Disconnect (GLD) specifications by one of the major surge arrester manufacturers. The incorrect GLD specifications have resulted in premature and nuisance operations. These were triggered by low intensity lightning storms as a result of the lower threshold trigger values. These premature operations have left numerous transformers vulnerable for periods as long as six months and have resulted in the transformer failures increasing from 2.4% quoted by Chatterton [6] in 2002 to 5.19% in 2005 and a reduction to 3.84 % in November 2006 once the problem was identified and the GLDs corrected. See annexure A, Figure A1 of the Plant report for November 2006 for performance details. Hence, this manufacturing flaw and the GLD's sensitivity to specification necessitate further investigation into the spark gap as back-up protection. The spark gap therefore becomes more viable than line or double surge arresters due to its cost effectiveness and robustness. This thesis was based on an idea proposed by Eskom's (Industrial Association Resource Centre) IARC. The aim was to investigate the technical feasibility of using a spark gap to grade with a distribution class surge arrester whilst the surge arrester was operational. The purpose of the spark gap was to act as back-up protection when the arrester fails. Experimentation was undertaken via simulation using the FEMLAB software to model the most suitable gap and geometry for a given rod diameter. The breakdown characteristic of the rod was well understood and verified. Thus, the results obtained from the simulation were compared against the laboratory experiments for the same rod diameters and tip shapes used in the simulation. The results have been analyzed to determine whether the spark gap is a feasible solution for use with surge arresters to protect the transformer from induced strikes following arrester failure. / A possible lower cost alternative to medium voltage line arresters and parallel-connected / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2007. / Thesis (M.Sc.)-University of KwaZulu-Natal, 2007.

No description available.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 176-180). Also available via the Internet.