Protection Functions; Stabilized Three-Phase Differential Protection Mpdif - ABB RELION 630 Series Applications Manual

Motor protection and control

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1MRS756785 G

3.3.6

3.3.6.1

REM630

Application Manual

GUID-02640926-724F-4CFA-B189-F643DA17300B V1 EN

Figure 17:

Apparatus control

Protection functions

Stabilized three-phase differential protection with low stage (biased stage) and high

stage (instantaneous stage) is used for protecting motor against winding failure. Two

sets of three phase currents from the line side, 3I, and neutral side, 3I_N, are connected

to the inputs I3P and I3P_N of MPDIF. Possible uneven current transformer saturation

creates a challenge for the differential protection. MPDIF includes AC current

transformer saturation detection-based blocking which prevents unnecessary tripping

in case of magnetizing inrush currents which may be present at switching operations,

at overvoltages or during external faults. MPDIF includes also a user-selectable DC

restraint feature. The feature decreases the sensitivity of the differential protection for

a temporary time period to avoid the motor to be unnecessarily disconnected due to

high DC currents during external faults.

The operate signal from the low and high stages are used to provide a LED indication

on the LHMI. Low stage and high stage operate outputs are connected to the

Section 3

REM630 variants

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Relion rem630