Determining temporary overvoltage levels for application of metal oxide surge arresters on multigrounded distribution systems

Different analytical methods that may be used to calculate values of temporary overvoltage on multigrounded distribution systems as a result of single line-to-ground faults are evaluated in terms of their general accuracy; their ability to account for changes of earth resistivity, ground electrode resistances, and grounding frequency; and the overall impact of such changes on the calculated overvoltage level. Recommendations are provided for the use of these methods under different sets of system conditions. It has been concluded that the commonly used method based on symmetrical components is inadequate for anything but the simplest calculation for a system with near-ideal grounding parameters. For systems where poor grounding conditions are known to prevail, the best method of analysis is to neglect the ground effects altogether. The best overall results are provided by a sophisticated, matrix-algebra-based method which analyzes the ladder network cells of the multigrounded distribution neutral individually.<
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