This research aims to analyze transient processes during loop closing and opening operations in distribution grids with DGs. The realization of load transfer without blackouts can improve the reliability of a power supply, reducing economic loss. Hence, we summarize the problems appearing during loop closing and opening processes. Based on this analysis, a loop closing operation was executed at one 110 kV substation, and the voltage and current waveform were recorded. A theoretical analysis of field experiments results yielded the spectral characteristics of the system. A loop closing operation was simulated using EMTP-ATP software. The simulation and the field experiment results matched closely, thus validating the simulation model. We conclude that closing and opening operation are influenced by voltage difference, including the amplitude and phase angle difference. The system capacitance and inductance have impact not only on the transient over-voltage, but also on the frequency characteristics of the system.

electromagnetic loop network, influencing factors, loop-closing-and-opening experiment, transient process, spectrum analysis