Function Block; Functionality; Operation Principle - ABB RELION 620 Series Technical Manual

1MAC504801-IB E
4.6.1.2
4.6.1.3
4.6.1.4
620 series ANSI
Technical Manual

Function block

GUID-9B1141EE-E666-4185-A3EF-F77F265D8F15 V1 EN
Figure 184: Function block

Functionality

Motor winding failure protection 87M is a unit protection function. The possibility of
internal failures of the motor 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 motor during the external faults
that have a fault current with high DC currents. 87M 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 "Enable" and "Disable".
The operation of the motor differential protection can be described using a module
diagram. All the modules in the diagram are explained in the next sections.
Section 4
Protection functions
405