The differential current protection detects current faults in the protected
zone between the current transformers. The differential current
protection consists of two parts, the stabilised differential current
protection and the high set differential current protection.
The alarm response of the stabilised differential current protection is
dependent on the operating characteristic and the measured restraint
and differential currents (evaluation is made per phase). The operating
characteristic separates the operation area (grey) and the restraint area
(white) in the figure. The restraint current is the highest value of neutral
and consumer side RMS currents. The differential current is the RMS
value of the fundamental frequency part of the sum (or difference) of the
neutral side and consumer side currents.
The alarm response of the high set differential current protection only
depends on the differential current. That is, the RMS value of the
fundamental frequency part of the sum (or difference) of the neutral side
and consumer side currents.
Differential
current
[%]
Restraint current [%]
0
Region 2
Region 3
Region 1
diff min
I
More information
See
AC configuration and nominal settings > AC configuration > [Source] AC configuration
for more information
about changing the reference direction of the current transformer.
Configure the parameters for the
Stabilised differential current
protection under
Configure > Parameters > Generator > Current
protections > Stabilised differential current
.
Table 3.52
Stabilised differential current default parameters
Parameter
Range
Default
I diff. min.
5 to 100 % of I
nom
15 %
Region 1: End
10 to 150 % of I
nom
75 %
Region 2: Slope
10 to 50 % of I
nom
20 %
Region 2: End
100 to 1000 % of I
nom
200 %
Region 3: Slope
30 to 100 % of I
nom
75 %
Delay
0 to 60 s
0.00 s
Enable
Not enabled, Enabled
Enabled
Latch
Not enabled, Enabled
Enabled
Alarm action
Trip generator b AVR + stop engine*
Configure the parameters for the
High set differential current
protection under
Configure > Parameters > Generator > Current
protections > High set differential current
.
Table 3.53
High set differential current default parameters
Parameter
Range
Default
Set point
50 to 1200 % of I
nom
800 %
Delay
0 to 60 s
0.00 s
Enable
Not enabled, Enabled
Enabled
Latch
Not enabled, Enabled
Enabled
Alarm action
Trip generator b AVR + stop engine*
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