ABB RELION 650 SERIES, Руководство по применению

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Basic data:
Rated knee
point Ek
300 V
Cable loop
resistance:
Note! Only one way as the system grounding is limiting the
ground-fault current. If high ground-fault current exists use two
way cable.
One way as the system earthing is limiting the
earth-fault current. If the neutral solidly
grounded, then a high-earth- fault current
exists, and a two way cable is considered for
the loop
Loop lenght: <50 m; cross section of the cable: 2.5 mm2 (one
way)
2
0, 021 75 C
Cu
mm
at
m
r
W ×
= °
sec
50
0, 021 =0,42 75 C
2, 5
R at
l
A
r × = × W °
=
sec
0,42
loop
R R
W
= =
Max fault
current:
The maximum through fault current given by the transformer
reactance for example, 28 kA.
Calculation:
Select a setting of TripPickup=60
V.
The rated knee point Ek of the current transformer shall fulfill the following conditions:
0, 8 2 1, 6 82, 9 132, 64
k R
E U V
> × × = × =
( )
2 2 100 200
E
k
U TripPickup V
> × > = × =
The requested conditions are fulfilled because Ek = 300 V.
Check from the table of selected resistances the required series stabilizing resistor value to use.
Since this application it is not required to be so sensitive, select
R series=150 ohm, which gives an
IED current of 400 mA.
To calculate the sensitivity at operating voltage, refer to equation 10 which gives an acceptable
value; in fact in this example the sensitivity is about 13% of the nominal current of the CT:
1MRK 505 287-UUS B Section 6
Differential protection
Busbar protection REB650 67
Application manual
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