Patent ID: 7710693

Claim:
An apparatus for providing protection for a synchronous generator having a capability curve and a steady state stability limit (SSSL) curve associated therewith, said generator capability curve comprising a field winding current limit curve, an armature current limit curve and a stator end region heating limit curve, the apparatus comprising: a microcontroller receiving phase currents and voltages from the synchronous generator, said microcontroller including a P, Q calculator which calculates three-phase active power (P) and three-phase reactive power (Q) values using the phase currents and phase voltages associated with the synchronous generator, said three-phase active power (P) and three-phase reactive power (Q) values defining the P, Q operating point of the synchronous generator on a P, Q plane; and a calculator of a generator protection zone on the P, Q plane, said generator protection zone being defined by two active power elements and a loss-of-field element, said loss-of-field element being defined by the stator end region heating limit curve when the SSSL curve is situated outside the capability curve, said loss-of-field element being defined by the SSSL curve when the SSSL curve is situated inside the capability curve, said calculator of the generator protection zone further determining whether the three-phase active power (P) and the three-phase reactive power (Q) values are within the generator protection zone, wherein if the three-phase active power (P) and the three-phase reactive power (Q) values are within the generator protection zone, said microcontroller asserting a protection signal to remove the synchronous generator from service or trip a field breaker associated with the synchronous generator.