9.13 Accidental energizing protection for synchronousgenerator AEGPVOC9.13.1 IdentificationFunction description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberAccidental energizing protection forsynchronous generatorAEGPVOC U 50AE9.13.2 ApplicationOperating error, breaker head flashovers, control circuit malfunctions or acombination of these causes results in the generator being accidentally energizedwhile offline. Three-phase energizing of a generator that is at standstill or on turninggears causes it to behave and accelerate similarly to an induction motor. Thegenerator, at this point, essentially represent sub-transient reactance to the system andit can draw one to four per unit current depending upon the equivalent systemimpedance. This high current may thermally damage the generator in a few seconds.Accidental energizing protection for synchronous generator AEGPVOC monitorsmaximum phase current and maximum phase-to-phase voltage of the generator. In itsbasis it is “voltage supervised over current protection”. When generator voltage failsbelow preset level for longer than preset time delay an overcurrent protection stage isenabled. This overcurrent stage is intended to trip generator in case of an accidentalenergizing. When the generator voltage is high again this overcurrent stage isautomatically disabled.9.13.3 Setting guidelinesI>: Level of current trip level when the function is armed, that is, at generatorstandstill, given in % of IBase. This setting should be based on evaluation of thelargest current that can occur during the accidental energizing: Ienergisation. This currentcan be calculated as:3''Nenergisationd T networkUI X X Z= + +EQUATION2282 V2 EN (Equation 238)1MRK 502 071-UEN - Section 9Current protectionGenerator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062 393Application manual
