1.0 Introduction
1.1 Background of the Study
The demand for the generation and transmission of large amounts of electric power today, necessitates its transmission at extra-high voltages. In modern times, high voltages are used for a wide variety of applications covering the power systems, Industry and research Laboratories. Such applications have become essential to sustain modern civilization.
The diverse conditions under which a high voltage apparatus is used necessitate careful design of its insulation and the electrostatic field profiles[2]. This entails the analysis of the electrical power system to determine the probability of post insulation flashovers. For instance, analysis must be carried out to determine that the insulation contained within power system components like transformers has the acceptable margin of protection. Since the internal insulation is not self-restoring, a failure is completely unacceptable. An insulation co-ordination study of a substation will present all the probabilities and margins for all transients entering the station.
Over voltages are phenomena which occur in power system networks either externally or internally. The selection of certain level of over voltages which are based on equipment strength for operation is known as Insulation co-ordination[3]. It is essential for electrical power engineers to reduce the number of outages and preserve the continuity of service and electric supply. In another perspective, Insulation co-ordination is a discipline aiming at achieving the best possible techno-economic compromise for protection of persons and equipment against over voltages, whether caused by the network or lightning.
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