ABB RELION 620 Series Technical Manual page 608

Section 4
Protection functions
4.4
4.4.1
4.4.1.1
4.4.1.2
4.4.1.3
4.4.1.4
602
Unbalance protection
Negative-sequence overcurrent protection NSPTOC
Identification
Function description
Negative-sequence overcurrent
protection
Function block
A070758 V1 EN
Figure 309: Function block
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.
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
NSPTOC I2>
1MRS757644 F
ANSI/IEEE C37.2
device number
46
620 series
Technical Manual