As shown in the illustrated alternator protection scheme diagram, what device provides input to the reverse power relay "RP", the under voltage/overvoltage relay "UV/OV", and the under frequency/over frequency relay "UF/OF"? See illustration EL-0067.
ā¢ Current transformer (CT) vs potential transformer (PT) functions in generator protection ā¢ Which electrical quantity each relay needs to sense: reverse power, under/overvoltage, under/overfrequency ā¢ How the relays in the diagram are physically connected to the CTs or PTs
ā¢ Look at the wiring in the illustration: from what device do the lines feeding the RP and UV/OV UF/OF relays originate? ā¢ Ask yourself which measurement is required for under/overvoltage and under/overfrequency protection: is it current or voltage? ā¢ For a reverse power relay, which input is normally taken from instrument transformers so the relay can detect power flow direction?
ā¢ Trace the connection lines from RP and UV/OV UF/OF back to the common source; note if they tie into the symbol labeled PT or one of the CTs. ā¢ Confirm which transformer type is used to step down system voltage for metering and protection. ā¢ Eliminate options that do not appear anywhere in the schematic (e.g., strobe sensors) before choosing between CT and PT.
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