Characteristic Value
Reset time < 40 ms
Reset ratio Typical 0.96
Retardation time < 35 ms
Operate time accuracy in definite time mode ±1.0% of the set value or ±20 ms
1) Current before fault = 0.0, f
n
= 50 Hz, results based on statistical distribution of 1000 measurements
2) Includes the delay of the signal output contact
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 238: Function block
4.4.1.3 Functionality
The negative-sequence overcurrent protection 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
Section 4 1YHT530004D05 D
Protection functions
446 615 series
Technical Manual
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