1994 Volume 114 Issue 7-8 Pages 715-722
When a grid fails to be supplied with electric power, a photovoltaic generation system connected to the grid may possibly start islanding. Therefore, the photovoltaic generation system needs to have a protective equipment for detecting not only fault of the grid and the system but also islanding of the system. This paper describes the protective equipment that prevents the photovoltaic generation system connected to the grid from starting islanding. It does so by detecting (1) a periodical frequency variation of voltage caused at the connection by output of a reactive power variation of a photovoltaic inverter and (2) a rapid change of harmonic voltage caused by exciting characteristics of a pole transformer.