The protection function can detect earth faults in the entire rotor winding andassociated connections.Requires injection unit REX060 and a coupling capacitor unit REX061 for correctoperation.7.8.3 Description of input signalsThe inputs to the sensitive rotor earth-fault protection function block are as shown intable 122.Table 122:Description of various inputsInput signal DescriptionUSU The measured injection voltage. This signal is taken from a pre-processor block, the AIoutput. The analog voltage input AI1 is linked to the phase L1 in the pre-processor blockin the Signal Matrix tool.USI The measured injection current. This signal is taken from a pre-processor block, the AIoutput. In the pre-configured version, the analog voltage input AI2 is linked to the phaseL2 in the pre-processor block in the Signal Matrix tool.BLOCK Input to block the functionZREFSEL The selection of any of the predefined reference impedances. There is a possibility tochange from one set reference impedance to another. Two different referenceimpedances are available.7.8.4 Description of output signalsThe outputs of the sensitive rotor earth-fault protection function block are as shown intable 123.Table 123:Description of various outputsOutput signal DescriptionTRIP Common trip command signalTRIPDC is the trip command signal at DC-side earth faultTRIPAC is the trip command signal at AC-side earth faultSTART is a common signal for both AC and DC side of exciterSTARTDC is the start signal at DC-side earth faultSTARTAC is the start signal at AC-side earth faultALARM Signal activated after a set time delay, if the calculated fault resistance gets lower thanthe set alarm levelERROR Error signal which is boolean with values 0 and 1ERRSTAT Status coded signal giving type of error. See table 124RAVE Measured resistance to earth in Ω at an injected frequency (real part of the compleximpedance)XAVE Measured reactance to earth in Ω at the injected frequency (imaginary part of thecomplex impedance)Table continues on next pageSection 7 1MRK502052-UEN BImpedance protection280Technical manual
