ABB RELION 620 Series Technical Manual page 496

Section 4
Protection functions
4.3
4.3.1
4.3.1.1
4.3.1.2
4.3.1.3
4.3.1.4
490
Differential protection
Stabilized and instantaneous differential protection for
machines MPDIF
Identification
Function description
Stabilized and instantaneous differential
protection for machines
Function block
GUID-30DCCB1F-FA35-4315-95AC-323B91D1DD46 V1 EN
Figure 246: Function block
Functionality
The stabilized and instantaneous differential protection for machines function MPDIF
is a unit protection function. The possibility of internal failures of the machine is
relatively low. However, the consequences in terms of cost and production loss are
often serious, which makes the differential protection an important protection
function.
The stability of the differential protection is enhanced by a DC restraint feature. This
feature decreases the sensitivity of the differential protection optionally for a
temporary time period to avoid an unnecessary disconnection of the machine during
the external faults that have a fault current with high DC currents. MPDIF also
includes a CT saturation-based blocking which prevents unnecessary tripping in case
of the detection of the magnetizing inrush currents which can be present at the
switching operations, overvoltages or external faults.
Operation principle
The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
IEC 61850 IEC 60617
identification identification
MPDIF 3dI>M/G
1MRS757644 F
ANSI/IEEE C37.2
device number
87M/G
620 series
Technical Manual