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1MAC050144-MB C
Section 4
Protection functions
615 series ANSI
321
Technical Manual
4.6.1.2
Function block symbol
Figure 152:
Function Block Symbol
4.6.1.3
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 security 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.
4.6.1.4
Operation Principle
The function can be enabled and disabled with the Operation setting. The corresponding
parameter values are "Enabled" and "Disabled".
The operation of the motor winding failure protection can be described using a module
diagram. All the modules in the diagram are explained in the next sections.
TRIP
OPR _LS
I_A1
87M
I_B1
BLOCK
BLK_OPR_LS
BLK_OPR_HS
OPR_HS
INT_BLKD
I_C1
I_A2
I_B2
I_C2
Содержание 615 Series ANSI
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