An 11 kV feeding power system shown in Figure 1. Data of the system is provided in Table 1. Consider only 3-phase faults with short circult MVA = 12. The overcurrent relay characteristics is given in APPENDIX A. The impedance of the generator to BUS I is jo.10 p.u, BUS I t BUS 2 is j0.03 p.u and BUS 2 to BUS 3 is j0.05 p.u. As the consultant engineer, you were asked to do the following: a. Draw its equivalent in Per Unit circult. b. Calculate fault current at relay 3 and relay 2.

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An 11 kV feeding power system shown in Figure 1. Data of the system is provided in
Table 1. Consider only 3-phase faults with short circult MVA = 12. The overcurrent relay
characteristics is given in APPENDIX A. The impedance of the generator to BUS 1 is
j0.10 p.u, BUS i to BUS 2 is j0.03 p.u and BUS 2 to BUS 3 is j0.05 p.u. As the
consultant engineer, you were asked to do the following:
a. Draw its equivalent in Per Unit circult.
b. Calculate fault current at relay 3 and relay 2.
c. Calculate relay settings of breaker (B3) and breaker (B2).
d. Reason on selecting the value of Current Tap Setting (CTS) and Time Dial
Setting (TDS).
3
S3
BI
B2
B3
11 kV
Figure 1
Table 1
P.F (Lag)
S (power in
MVA)
BUS
Breaker
C.T Ratio
800/5
600/5
1
10
0.85
B1
2
6
0.9
B2
4
0.9
B3
400/5
Transcribed Image Text:An 11 kV feeding power system shown in Figure 1. Data of the system is provided in Table 1. Consider only 3-phase faults with short circult MVA = 12. The overcurrent relay characteristics is given in APPENDIX A. The impedance of the generator to BUS 1 is j0.10 p.u, BUS i to BUS 2 is j0.03 p.u and BUS 2 to BUS 3 is j0.05 p.u. As the consultant engineer, you were asked to do the following: a. Draw its equivalent in Per Unit circult. b. Calculate fault current at relay 3 and relay 2. c. Calculate relay settings of breaker (B3) and breaker (B2). d. Reason on selecting the value of Current Tap Setting (CTS) and Time Dial Setting (TDS). 3 S3 BI B2 B3 11 kV Figure 1 Table 1 P.F (Lag) S (power in MVA) BUS Breaker C.T Ratio 800/5 600/5 1 10 0.85 B1 2 6 0.9 B2 4 0.9 B3 400/5
Relay characteristics
Typical time curves
type CO-7
over current relay
50-60 cycles
Current tap settings:
4,5.0,7,8,10,12 amperes
Time dial setting
2
3
5 6 7 8 9 10 12 14 16 18 20
Current as a multiple of tap setting
spuoses u au bugeado
Transcribed Image Text:Relay characteristics Typical time curves type CO-7 over current relay 50-60 cycles Current tap settings: 4,5.0,7,8,10,12 amperes Time dial setting 2 3 5 6 7 8 9 10 12 14 16 18 20 Current as a multiple of tap setting spuoses u au bugeado
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