External Faults On C-3; External Faults On C-4 - GE B30 Instruction Manual

10 APPLICATION OF SETTINGS
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 will 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 may saturate due to the DC components and may generate a spurious differential signal for both the North and South bus
relays depending on the bus configuration. The saturation will not occur before 5.85 ms and will be detected by the Satura-
tion Detector.
Table 10–7: EXTERNAL FAULT CALCULATIONS ON C-4
CT I (KA)
FAULT
CT-1 0
CT-2 0
CT-3 6.0
CT-4 9.0
CT-6 3.0
CT-7, CT-8 9.0
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 will 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 may saturate due to the DC components and may generate a spurious differential signal for both the North and South bus
relays depending on the bus configuration. The saturation will not occur before 4.83 ms and will be detected by the Satura-
tion Detector.
Table 10–8: EXTERNAL FAULT CALCULATIONS ON C-5
CT I (KA)
FAULT
CT-1 0
CT-2 0
CT-3 6.0
CT-4 5.0
CT-5 11.0
CT-7, CT-8 11.0
GE Multilin
I (A SEC) T (MS)
FAULT DC
0.00 N/A
0.00 N/A
25.00 5
45.00 40
15.00 40
37.50 40
I (A SEC) T (MS)
FAULT DC
0.00 N/A
0.00 N/A
25.00 5
25.00 30
55.00 30
45.83 30
B30 Bus Differential System
10.4 SLOPES AND HIGH SET THRESHOLD

10.4.5 EXTERNAL FAULTS ON C-4

AC DC
SATURATION SATURATION
No No
No No
No No
No Yes
No Yes
No Yes
10.4.6 EXTERNAL FAULTS ON C-5
AC DC
SATURATION SATURATION
No No
No No
No No
No Yes
No Yes
No Yes
T (MS)
SAT
N/A
N/A
N/A
5.85
35.25
9.40
T (MS)
SAT
N/A
N/A
N/A
15.19
4.83
7.16
10
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