4.4
Unbalance protection
4.4.1
Negative-sequence overcurrent protection NSPTOC
4.4.1.1
Identification
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Negative-sequence overcurrent
protection
NSPTOC
I2>
46
4.4.1.2
Function block
A070758 V1 EN
Figure 108:
Function block
4.4.1.3
Functionality
The negative-sequence overcurrent protection function NSPTOC is used for
increasing sensitivity to detect single-phase and phase-to-phase faults or unbalanced
loads due to, for example, broken conductors or unsymmetrical feeder voltages.
NSPTOC can also be used for detecting broken conductors.
The function is based on the measurement of the negative sequence current. In a fault
situation, the function starts when the negative sequence current exceeds the set limit.
The operate time characteristics can be selected to be either definite time (DT) or
inverse definite minimum time (IDMT). In the DT mode, the function operates after
a predefined operate time and resets when the fault current disappears. The IDMT
mode provides current-dependent timer characteristics.
The function contains a blocking functionality. It is possible to block function outputs,
timers or the function itself, if desired.
4.4.1.4
Operation principle
The function can be enabled and disabled with the
Operation
setting. The
corresponding parameter values are "On" and "Off".
Section 4
1MRS757454 D
Protection functions
228
611 series
Technical Manual
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