Evaluation of generator circuit breaker applications
Fourie, Johannes Frederick
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The use of generator circuit breakers in power stations was investigated and evaluated. A feasibility study to determine if the additional capital cost required, when using a generator circuit breaker in a power station could be justified by the advantages it provides. The background to the study is provided through a technology and literature survey. Included in the technology review and the literature study is information on interruption mediums, the historic developments of circuit breakers and generator circuit breaker application theory. This data was used to determine the practicality of using a specific interruption medium within a generator circuit breaker application. The requirements of generator circuit breakers were determined and used to evaluate the interruption mediums in question. To ensure practical results, commonly used layouts were used to determine the effect of using a generator circuit breaker on the reliability, availability and the mean time to repair of a power station electrical distribution layout. Furthermore, the effect of the protection on the generator and generator transformer was evaluated. It was found that increased selectivity of the protection system by using a generator circuit breaker limits the extent of equipment damage in case of failure. Practical layouts were used to determine the effect on reliability. The analysis was conducted using assumed values of operational costs to determine the cost incurred through the change in reliability of the power station. By adding a generator circuit breaker, the station transformer and associated equipment is regarded as back-up or redundant equipment. This increases the reliability of the power station dramatically and limits the risk of income lost due to failures. The full evaluation included the estimation of the capital investment costs and the impact that the additional cost has on the operational requirements of a power station. The study determined that the capital cost required to use a generator circuit breaker results in no additional income for a power station. Through the increased protection, higher availability and the possible omission of power station ancillary equipment, the use of generator circuit breakers will result in more power being delivered and more income generated by a power station. The study proved that the generator circuit breaker is a critical part of a power station layout and is a necessary capital requirement to ensure the sustainability of the power station.
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