8-10
B30 BUS DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
SLOPES AND HIGH SET THRESHOLD
CHAPTER 8: APPLICATION OF SETTINGS
8
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 table below summarize the DC saturation threat for the fault on C-3. CT-3, 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 23.68 ms and is detected by the
Saturation Detector.
Table 8-6: Calculations for the external faults on C-3
8.4.5 External faults on C-4
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
Saturation Detector.
Table 8-7: External fault calculations on C-4
8.4.6 External faults on C-5
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.
CT
I
FAULT
(kA)
I
FAULT
(A sec)
T
DC
(ms)
AC saturation
DC saturation
t
SAT
(ms)
CT-1
0
0.00
N/A
No
No
N/A
CT-2
0
0.00
N/A
No
No
N/A
CT-3
8.0
33.33
40
No
Yes
23.68
CT-4
5.0
25.00
30
No
Yes
26.37
CT-6
3.0
15.00
40
No
Yes
61.50
CT-7, CT-8
8.0
33.33
40
No
Yes
23.68
CT
I
FAULT
(kA)
I
FAULT
(A sec)
T
DC
(ms)
AC saturation
DC saturation
t
SAT
(ms)
CT-1
0
0.00
N/A
No
No
N/A
CT-2
0
0.00
N/A
No
No
N/A
CT-3
6.0
25.00
5
No
No
N/A
CT-4
9.0
45.00
40
No
Yes
10.03
CT-6
3.0
15.00
40
No
Yes
61.50
CT-7, CT-8
9.0
37.50
40
No
Yes
22.23
Summary of Contents for b30
Page 10: ...x B30 BUS DIFFERENTIAL SYSTEM INSTRUCTION MANUAL TABLE OF CONTENTS ...
Page 486: ...5 278 B30 BUS DIFFERENTIAL SYSTEM INSTRUCTION MANUAL TESTING CHAPTER 5 SETTINGS 5 ...
Page 616: ...iv B30 BUS DIFFERENTIAL SYSTEM INSTRUCTION MANUAL ABBREVIATIONS ...
Page 632: ...xvi B30 BUS DIFFERENTIAL SYSTEM INSTRUCTION MANUAL INDEX ...
