Stability of a synchronous machine due to an unsymmetrical fault in unbalanced power systems

The authors examine the transient stability of a single synchronous generator connected by an unbalanced network to an infinite bus supply and subjected to a variety of unsymmetrical shunt and series faults. Results of several case studies are used to evaluate the effects of untransposed lines and unbalanced single-phase loads in the presence of grounded and ungrounded generator neutrals. Although line unbalance is shown to have only a minimal effect on generator transient response, the type of shunt fault does not make a significant difference. In particular, under certain network conditions the single-line-to-ground fault followed by temporarily switching out the faulted phase has a more severe effect on system stability than the traditionally accepted three-phase fault.<>