EFFECTS OF THE POWER CAPACITIRS ON OPTIMAL SETTING OF THE STATOR EARTH FAUIT RELAY

The purpose of generator neutral grounding through an impedance or resistance are to limit transient over voltage , limit the damage at the point of fault and provide sensitive means of detection for insullation deterioration If the neutral grounding resistance to be selected biger then the studied level it may cause undesirably high transient over voltage, and in contrast , the reduction of the mentioned resistance less than the limited level will cause also the damages at the time of happening one earth fault at the protected zone of stator earth fault relay. in this paper an attempt has been made to reduce the voltage appearing across the generator neutral point during capastive transfer of voltage from the high voltage side of the unit generator - transformer without reduction at neutral grounding resistance with considering of using power capacitors at the low voltage side of transformer and at the result it is suggested the sensitive and adequate setting for the stator earth fault relays from the type of %95 which the most generators at power plants have this type of relay .