Application - ABB RELION Series Technical Manual

Section 4
Protection functions
4.3.1.5
4.3.1.6
398
blocked and the timers are reset. In the "Block OPERATE output" mode, the function
operates normally but the OPERATE output is not activated.

Application

Since the negative sequence current quantities are not present during normal, balanced
load conditions, the negative sequence overcurrent protection elements can be set for
faster and more sensitive operation than the normal phase-overcurrent protection for
fault conditions occurring between two phases. The negative sequence overcurrent
protection also provides a back-up protection functionality for the feeder earth-fault
protection in solid and low resistance earthed networks.
The negative sequence overcurrent protection provides the back-up earth-fault
protection on the high voltage side of a delta-wye connected power transformer for
earth faults taking place on the wye-connected low voltage side. If an earth fault
occurs on the wye-connected side of the power transformer, negative sequence current
quantities appear on the delta-connected side of the power transformer.
The most common application for the negative sequence overcurrent protection is
probably rotating machines, where negative sequence current quantities indicate
unbalanced loading conditions (unsymmetrical voltages). Unbalanced loading
normally causes extensive heating of the machine and can result in severe damages
even over a relatively short time period.
Multiple time curves and time multiplier settings are also available for coordinating
with other devices in the system.
Signals
Table 393: NSPTOC Input signals
Name Type
I SIGNAL
2
BLOCK BOOLEAN
ENA_MULT BOOLEAN
Table 394: NSPTOC Output signals
Name Type
OPERATE BOOLEAN
START BOOLEAN
Default Description
0 Negative phase sequence current
0=False Block signal for activating the blocking mode
0=False Enable signal for current multiplier
Description
Operate
Start
1MRS758755 A
REC615 and RER615
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