ABB REC650 - Page 59

0,
0
0, 0
0, 0
1,
0, 0
3 15 3 145
3 3.7
15 42
15 42
2 3.5
2
15 42
net
T
net T
net T
net
net T
Z
V j
I kA
Z Z j j
Z Z j j
j
Z
j j
Z Z
× ×
= × = × =
× ×
+ +
× +
× +
+
+
GUID-CC2E2412-4939-4285-A491-FCCC0AE0F939-ANSI V1 EN (Equation 14)
The residual current from the transformer during a single phase-ground-fault and
with minimum short circuit power is:
0,
0
0, 0
0, 0
1,
0, 0
3 20 3 145
3 2.4
20 42
20 42
2 10
2
20 42
net
T
net T
net T
net
net T
Z
V j
I kA
Z Z j j
Z Z j j
j
Z
j j
Z Z
× ×
= × = × =
× ×
+ +
× +
× +
+
+
GUID-991D27BC-4413-4A9B-BF49-F25986545C73-ANSI V1 EN (Equation 15)
The residual current from the transformer during a phase-to-phase to ground-fault
and with maximum short circuit power is:
0,
0
0, 0
0, 0
1,
0, 0
3 15 3 145
3 2.6
15 42
15 42
3.5 2
2
15 42
net
T
net T
net T
net
net T
Z
V j
I kA
Z Z j j
Z Z j j
j
Z
j j
Z Z
× ×
= × = × =
× ×
+ +
+ ×
+ ×
+
+
GUID-CA17A1A5-E141-4F0B-B7C0-74683F9F9AD1-ANSI V1 EN (Equation 16)
The residual current from the transformer during a phase-to-phase to ground-fault
and with minimum short circuit power is:
0,
0
0, 0
0, 0
1,
0, 0
3 20 3 145
3 2.2
20 42
20 42
10 2
2
20 42
net
T
net T
net T
net
net T
Z
V j
I kA
Z Z j j
Z Z j j
j
Z
j j
Z Z
× ×
= × = × =
× ×
+ +
+ ×
+ ×
+
+
GUID-933BE756-31CD-45BA-B3EB-5DC00CA25DC0-ANSI V1 EN (Equation 17)
To assure that the protection detects all ground-faults on the 145 kV busbar the
protection should be set as follows:
Pickup1 ≤ 0.75 · 2.2 = 1.65 kA = 687 % IBase
1
1
1
3
3
Ph-Ph
145
kV 22 kV
ANSI11000128-1-en.vsd
REC650
Y
Y
Y
51N_67N
85%
ANSI11000128 V1 EN
Figure 11: Fault calculation for 145 kV residual overcurrent protection
selectivity
1MRK 511 286-UUS A Section 3
REC650 setting examples
53
Application manual