ABB REO 517, Applications Manual, Page: 117 / 440

107
Two step definite and inverse time-
delayed residual
overcurrent protection (TEF1 and TEF2)
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Activate the independent time-delay function by setting
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= Def (or inverse
time delay according to the setting table). The tLow timer starts when both the definite/
inverse time characteristic and the tMinInv timer operate. The tMinInv timer starts
when the I
N
current to the relay is equal to or higher than the set operate value for IN
>Low, the content of the second harmonic in I
N
is less than 20% and the directional con-
dition is fulfilled (if selected).
The inverse time calculation starts when I
N
is equal to or higher than the set operate val-
ue for IN>Low, the content of the second harmonic in I
N
is less than 20% and the di-
rectional condition is fulfilled (if selected). The inverse time delay is determined by the
selection of the characteristic (NI, VI etc.) in the Characteristic setting, the setting of the
characteristic IN>Inv current and the setting of the time multiplier k.
The tLow timer is normally set to zero. Use it to add a constant time to the inverse time
delay. Figure 48 shows the effect of the IN>Low and tMinInv settings on the inverse
characteristic.
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Activate the independent time delay function by setting
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=NonDir or Direc-
tional. The tHigh timer starts when the I
N
current to the relay is equal to or higher than
the set operate value for IN >High, the content of the second harmonic in I
N
is less than
20% and the directional condition is fulfilled (if selected).
1
2
3
4
5
1 2 3 5 7
10
20
30 50
Logaritmic
Inverse
Normal
Inverse
(k=0,4)
x IN>
t (s)
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tMinInv
IN>Low