External Faults On C-4 - GE B30 UR Series Instruction Manual

Bus differential system
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10.4 SLOPES AND HIGH SET THRESHOLD
Table 10–6: CALCULATIONS FOR THE EXTERNAL FAULTS ON C-3
CT
CT-2
CT-3
CT-4
CT-6
CT-7, CT-8
The following table presents the results of analysis of an external fault on circuit C-4 (C-4 is connected to the North bus; C-
3 and C-5 are connected to the South bus).
By comparing the secondary currents (column 3 in the table below) with the limits of linear operation for the CTs (column 4
in the Limits of Linear Operations of the CTs table shown earlier), it is concluded that none of the CTs saturate due to the
AC currents during this fault.
Columns 6 and 7 of the following table summarize the DC saturation threat for the fault on C-4. CT-4, CT-6, CT-7, and CT-
8 can saturate due to the DC components and can generate a spurious differential signal for both the North and South bus
relays depending on the bus configuration. The saturation does not occur before 10.03 ms and is detected by the Satura-
tion Detector.
Table 10–7: EXTERNAL FAULT CALCULATIONS ON C-4
CT
CT-1
CT-2
CT-3
CT-4
CT-6
CT-7, CT-8
The following table presents the results of analysis of an external fault on circuit C-5 (C-5 is connected to the North bus; C-
3 and C-4 are connected to the South bus).
By comparing the secondary currents (column 3 in the table below) with the limits of linear operation for the CTs (column 4
in the Limits of Linear Operations of the CTs table shown earlier), it is concluded that none of the CTs saturate due to the
AC currents during this fault.
Columns 6 and 7 of the following table summarize the DC saturation threat for the fault on C-5. CT-4, CT-5, CT-7, and CT-
8 can saturate due to the DC components and can generate a spurious differential signal for both the North and South bus
relays depending on the bus configuration. The saturation does not occur before 9.45 ms and is detected by the Saturation
Detector.
Table 10–8: EXTERNAL FAULT CALCULATIONS ON C-5
CT
CT-1
CT-2
CT-3
10
CT-4
CT-5
CT-7, CT-8
10-10
I
(KA)
I
(A SEC)
FAULT
FAULT
0
0.00
8.0
33.33
5.0
25.00
3.0
15.00
8.0
33.33
I
(KA)
I
(A SEC)
FAULT
FAULT
0
0.00
0
0.00
6.0
25.00
9.0
45.00
3.0
15.00
9.0
37.50
I
(KA)
I
(A SEC)
FAULT
FAULT
0
0.00
0
0.00
6.0
25.00
5.0
25.00
11.0
55.00
11.0
45.83
B30 Bus Differential System
T
(MS)
AC
DC
SATURATION
N/A
No
40
No
30
No
40
No
40
No
T
(MS)
AC
DC
SATURATION
N/A
No
N/A
No
5
No
40
No
40
No
40
No
T
(MS)
AC
DC
SATURATION
N/A
No
N/A
No
5
No
30
No
30
No
30
No
10 APPLICATION OF SETTINGS
DC
T
(MS)
SAT
SATURATION
No
N/A
Yes
23.68
Yes
26.37
Yes
61.50
Yes
23.68

10.4.5 EXTERNAL FAULTS ON C-4

DC
T
(MS)
SAT
SATURATION
No
N/A
No
N/A
No
N/A
Yes
10.03
Yes
61.50
Yes
22.23
10.4.6 EXTERNAL FAULTS ON C-5
DC
T
(MS)
SAT
SATURATION
No
N/A
No
N/A
No
N/A
Yes
26.37
Yes
9.45
Yes
11.54
GE Multilin

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