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Technical description
2 Protection functions
2.12 Line differential protection
LdI> (87L)
VM59.EN001
VAMP 24h support phone +358 (0)20 753 3264
77
dI
module
Phase current amplitude
Trip region
dI> pick-up
Basic setting
Slope
Start of slope (Basic limit)
Figure 2.12-1 Tripping threshold characteristics
Bias current calculation is only used in protection stage
I>.
Bias current describes the average current flow in transformer.
Bias and differential currents are calculated individually for
each phase.
Equation 2.12-1: Bias current
2
2
1
RELAY
RELAY
b
I
I
I
Equation 2.12-2: Differential current
2
1
RELAY
RELAY
d
I
I
I
Figure 2.12-2 Example settings
Содержание VAMP 59
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