6 Analysis of Unbalanced Faults

6.1  INTRODUCTION

Most of the faults that occur on power systems are not the balanced (i.e., symmetrical) three-phase faults but the unbalanced (i.e., unsymmetrical) faults, specifically the single line-to-ground (SLG) faults. For example, Reference [5] gives the typical frequency of occurrence for the three-phase, SLG, line-to-line, and double line-to-ground (DLG) faults as 5%, 70%, 15%, and 10%, respectively.

In general, the three-phase fault is considered to be the most severe one. However, it is possible that the SLG fault may be more severe than the three-phase fault under two circumstances: (1) the generators ...

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