Although the ac fault current provided by photovoltaic (PV) power plant is limited as a weak power or a electric load, the voltage and current directions are different from convention synchronous source, since the current is controlled by the PV inverters. This paper investigates the measuring impedance and directional element of PV side line protections. The impedance trajectory are drawn and compared with conventional power source. Simulation result shows that the directional comparison teleprotection may miss operate under a line internal fault, since the measuring impedance drops into the negative direction area, even though the control word Weak Power Side is activated.

Directional element,measuring impedance,photovoltaic (PV) power plant,weak power side,teleprotection