Impact of protection coordination on sizes of several distributed generation sources

Distributed generation (DG) is expected for several applications in distribution system. Such advantages can be achieved if the relevant concerns are deliberately taken into account. In practice, the introduction of DG may lead to problems of protection coordination. In addition, the operating ranges of protective devices should also be considered. The degree of the problem tends to increase when several DG sources are installed in the system. This paper has analyzed and derived a set of equations to represent such protection coordination and operating range constraints. The result can be used to determine the sizes of DG sources while the existing protection scheme can be maintained. Numerical example shows that system authorities can select one of the feasible solutions to satisfy their purposes, e.g. economics and the existing conditions