Effect of load type on standalone micro grid fault performance

This paper studies the influence of the load type on the fault performance of the standalone Micro Grid (MG). Different load types (static and dynamic) are considered to show their effects on the standalone MG fault behavior. Specifically, the effects of constant power static loads, constant impedance static loads, and constant current static loads are analyzed. Also, effects of dynamic (rotating) loads are highlighted. Results show, that the rotating loads have dominant effects on the fault performance of the MG during the standalone (islanded) mode. Furthermore, rotating loads cause fault currents and touch voltages three times the values associated with the static loads. Consequently, the employed protective devices with the rotating loads MG must be rated three times larger than the employed protective devices with the static loads MG. Also, the time settings of the MG protection devices are highly influenced with the load type. For static load MG, it is equal to 250% of the rotating loads MG protection devices time settings. The three types of static load show different impacts on islanded MG fault performance. Constant power static load has the highest effect compared to the other two static load types (namely, constant impedance and constant current static loads). The results obtained in this study provide a guide for the MG protection designers and planners to consider the effects of load type on the MG protection devices rating and setting.