4.3.1
Stabilized and instantaneous differential protection for
machines MPDIF
4.3.1.1
Identification
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Stabilized and instantaneous differ-
ential protection for machines
MPDIF
3dI>M/G
87M/G
4.3.1.2
Function block
Figure 256: Function block
4.3.1.3
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.
4.3.1.4
Operation principle
The function can be enabled and disabled with the
Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of MPDIF can be described using a module diagram. All the modules
in the diagram are explained in the next sections.
Protection functions
1MRS757644 H
502
620 series
Technical Manual
