Apparatus and method for providing protection for a synchronous electrical generator in a power system

An apparatus for providing protection for a synchronous generator having a capability curve, a steady state stability limit (SSSL) curve, and a rated active power 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, wherein one of the active power elements is adaptable, 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.