![background image](http://html1.mh-extra.com/html/abb/rec650-ansi/rec650-ansi_applications-manual_3390438062.webp)
system. The neutral point resistor gives a 10 A ground-fault current during a zero
resistance ground-fault. This means that the resistance is
22000
3
1270
10
N
/
R
W
=
=
GUID-4ECDF824-B17E-436D-A668-ACA06BB375F7 V2 EN
(Equation 18)
The total zero sequence impedance of the 22 kV system is:
Z
0
= 3
R
N
//
j
3
X
N
// — jX
C
Ω / phase
As the Petersen coil is tuned the zero sequence impedance is:
Z
0
= 3
R
N
Ω / phase
The residual voltage during a resistive ground-fault in the 22 kV system is:
0
0
0
1
3
3
1
1
Phase
o
f
f
phase
V
V
V
or
R
R
V
Z
Z
=
=
×
×
+
+
GUID-AD49C138-F37B-4690-9E37-BA2BAD678A17-ANSI V1 EN
(Equation 19)
In our case the requirement is that ground-faults with a resistance up to 5 000 Ω shall be
detected. This gives:
0
1
0 20
3 5000
1
3 1270
phase
V
.
V
=
=
×
+
×
GUID-42D376ED-052F-4E9B-B4D9-8D679127BC0C-ANSI V1 EN
(Equation 20)
Step 1 and step 2 is given the same voltage setting but step 2 shall have longer time delay.
The residual ground-fault protection shall have a definite time delay. The time setting is
set longer than the time delay of the ground-fault protection of the outgoing feeders having
maximum 2 s delay. The time delay for step 1 is set to 3 s and the time delay for step 2 is
set to 4 s.
1.
Set
GlobalBaseSel
to
2
The (LV) winding data should be related to Global base 2.
2.
Set
Characterist1
to
Definite time
3.
Set
Pickup1
to
20 %
of
VBase
4.
Set
t1
to
3.0 s
5.
Set
Pickup2
to
20 %
of
VBase
6.
Set
t2
to
4.0 s
Section 3
1MRK 511 286-UUS A
REC650 setting examples
56
Application manual
Содержание REC650 ANSI
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