7.8.9 Operation principleThe protection principle is based on injection of voltage to the exciter point of the fieldcircuit.UinjRshunt~Step-upTransformerROTOR EFREX060/RIM moduleREG670456317IUGeneratorRN2REX061Generator Protection PanelR CIEC11000014-4-en.vsdU>8IEC11000014 V1 ENFigure 125: Example installation for rotor injection1 Generator unit consisting of a synchronous generator and a step-up transformer2 Generator field winding3 Capacitor coupling unit which is used to provide insulation barrier between rotor circuit and injectionequipment4 Cable used to inject the square-wave signal into the rotor circuit5 Connection for measurement of injected current. This signal is amplified in REX060 before it ispassed on to IED for evaluation.6 Connection for measurement of injected voltage. This signal is amplified in REX060 before it ispassed on to IED for evaluation.7 Two VT inputs into IED which are used to measure injected current and voltage8 Protection for excessive over-voltages posed by generator. REX060 can withstand without damagemaximum voltage of 120V and when used together with REX062 up to 240V.The injection signals are generated in a separate unit, REX060. The signals havesquare wave form and are injected to the generator via the coupling capacitor unitREX061 to the excitation circuit.In the REX060 unit the injection voltage and current signals are amplified to a leveladapted to the analogue voltage inputs of IED. In IED the measured signals evaluatedto detect rotor earth faults.1MRK502052-UEN B Section 7Impedance protection285Technical manual
