transformer nominal current several times over. It takes some time for the
current to assume its small stationary value. Since the high inrush current flows
on the connected side only, the tripping characteristic of the P634 differential
protection may give rise to a trip unless stabilizing action is taken. The fact that
the inrush current has a high proportion of harmonics having twice the system
frequency offers a possibility of stabilization against tripping by the inrush
current.
The P634 filters the differential current. The fundamental wave I
(
f
0
)
and second
harmonic components I
(
2 ⋅ f
0
)
of the differential current are determined. If the
ratio
I
(
2 ⋅ f
0
)
I
(
f
0
)
exceeds a specific adjustable value in at least one measuring
system, tripping is blocked optionally in one of the following modes:
●
across all three measuring systems
●
selectively for one measuring system (see Fig. 3-95, (p. 3-137)).
There will be no blocking if the differential current exceeds the set threshold
DIFF: Idiff>> PSx.
Operation of any inrush or overfluxing blocking element is signaled by
DIFF: Harm.block. trigg..
DIFF:
Id,1
303 303
f0
I(f0)
I(2⋅f0)
I(2⋅f0)/I(f0)
DIFF:
RushI(2f0)/I(f0) PSx
[ * ]
DIFF:
Meas.system 1 trigg.
[ 041 124 ]
DIFF:
Meas.system 2 trigg.
[ 041 125 ]
DIFF:
Meas.system 3 trigg.
[ 041 126 ]
0 30ms
&
DIFF:
Trip signal
[ 041 075 ]
DIFF:
Inrush blk. 1 trigg.
[ 041 118 ]
I(f0)
I(2⋅f0)
I(2⋅f0)/I(f0)
0 30ms
&
DIFF:
Inrush blk. 2 trigg.
[ 041 119 ]
I(f0)
I(2⋅f0)
I(2⋅f0)/I(f0)
0 30ms
&
DIFF:
Inrush blk. 3 trigg.
[ 041 120 ]
DIFF:
I(2⋅f0),1
303 301
DIFF:
I(2⋅f0),2
303 302
DIFF:
I(2⋅f0),3
303 309
62Z9005A
DIFF:
Id,2
303 304
DIFF:
Id,3
303 307
Parameter
set 1
set 2
set 3
set 4
DIFF:
RushI(2f0)/I(f0) PSx
072 159
073 159
074 159
075 159
f0
f0
2⋅f0
2⋅f0
2⋅f0
&
&
&
>
DIFF:
Id>> triggered
[ 041 221 ]
>
>
DIFF:
Inrush blk. trigg.
[ 019 213 ]
DIFF:
Harm.block. trigg.
[ 019 214 ]
DIFF:
Overflux.bl. trigg.
[ 019 202 ]
1
1
1
Fig. 3-95: Inrush blocking
3 Operation
P634
P634/EN M/R-42-A // P634‑311‑653 3-137
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