Table 39. Negative phase-sequence overcurrent protection (NSPTOC)
Characteristic Value
Operation accuracy At the frequency f = f
n
±1.5% of the set value or ±0.002 × I
n
Start time
1)2)
I
Fault
= 2 × set Start
value
I
Fault
= 10 × set Start
value
Typical 23 ms (±15 ms)
Typical 16 ms (±15 ms)
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
Operate time accuracy in inverse time mode
±5.0% of the theoretical value or ±20 ms
3)
Suppression of harmonics DFT: -50dB at f = n × f
n
, where n = 2, 3, 4, 5,
…
1)
Operate curve type = IEC definite time, negative sequence current before fault = 0.0, f
n
= 50Hz
2) Includes the delay of the signal output contact
3)
Maximum Start value = 2.5 × I
n
, Start value multiples in range of 1.5 to 20
Table 40. Negative phase-sequence overcurrent protection (NSPTOC) main settings
Parameter
Function Value (Range) Step
Start value NSPTOC 0.01...5.00 pu 0.01
Time multiplier NSPTOC 0.05...15.00 0.05
Operate delay time NSPTOC 0.04...200.00 s 0.01
Operating curve
type
1)
NSPTOC Definite or inverse time
Curve type: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
13, 14, 15, 17, 18, 19
1) For further reference please refer to the Operating characteristics table
Transformer Protection and Control 1MRS756788 A
RET630
Product version: 1.0 Issued: 15.09.2009
34 ABB
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