Loss Of Load Protection Loflptuc; Phase Reversal Protection Prevptoc; Motor Negative-Sequence Overcurrent Protection Mnsptoc - ABB RELION 630 Series Applications Manual

Section 3
REM630 variants
3.3.6.6
3.3.6.7
3.3.6.8
52

Loss of load protection LOFLPTUC

The loss of load protection is used for detecting sudden load loss which is considered
as a fault condition.
The set of three phase currents, I3P, is connected to the inputs and the function
operates when all the phase currents fall below the set level but stay above the set de-
energization level. It operates with definite time (DT) characteristics. The operate
signal is used to trigger the disturbance recorder.

Phase reversal protection PREVPTOC

The phase reversal protection is used for detecting the reversed connection of the
phases to a three-phase motor by monitoring the negative-phase sequence current of
the motor.
The operation of the function is based on the detection of very high negative-sequence
currents during motor start up due to incorrect phase connections to the motor. The
condition causes the motor to rotate in the reverse direction. The function starts and
operates when the negative-sequence current exceeds the corresponding set limits.
Phase reversal protection is blocked when current circuit supervision detects a failure.
Operate signal is used to trigger the disturbance recorder.

Motor negative-sequence overcurrent protection MNSPTOC

Two instances of negative-sequence overcurrent detection are provided for protection
against single-phasing, unbalance load or unsymmetrical voltage. The set of three
phase currents, I3P, is connected to the inputs.
The function operates in two modes, the definite time mode (DT) and the inverse
definite minimum time (IDMT) mode, for which two instances of the function block
are used. The negative-sequence overcurrent protection is blocked in case of current
circuit supervision failure is activated.
The common operate and start signal from the both MNSPTOC functions are
connected to an OR-gate to form a combined negative-sequence overcurrent operate
and start signal which is used to provide a LED indication on the LHMI. Also a
separate start and operate signal from the both MNSPTOC functions is connected to
the disturbance recorder.
1MRS756785 G
REM630
Application Manual