41A060577Fig. 5.1.4.7.-1 Inverse-time curves of element 465.1.4.8. Phase reversal protectionThe phase reversal protection is based on the calculated negative-phase-sequencecurrent and detects too high NPS current values during motor start up, caused byincorrectly connected phases, which in turn will cause the motor to rotate in theopposite direction.When the calculated NPS current value exceeds 75 per cent of the maximum phasecurrent value, the phase reversal element (46R) will generate a trip signal after afixed 200 ms’ operate time.The element will be reset in 200 ms after the calculated NPS current value has fallenbelow 75 per cent of the maximum phase current value.The phase reversal element can be set out of operation in SGF3.The unbalance element will be blocked during the tripping of the phasereversal element.5.1.4.9. Cumulative start-up time counterThe cumulative start-up time counter detects too frequent start-up attempts, whichcause overheating of the motor.The start-up time of every motor start up is added to a register, 66 value. When theregister’s value exceeds the set restart disable value, 66, any attempt to restart themotor will be disabled.Motor Protection RelayTechnical Reference Manual - ANSI VersionREM 610REM 6101MRS755537
