# 1012112100 VFigure 4.20 System diagram for Problem 4.2a1 210 2100 VFigure 4.21System diagram for Problem 4.2b4.3(a) Referring to Figure 4.20, set an instantaneous relay at bus A. Calculate the pickupfor faults on buses A and B and discuss the application of the instantaneous relayfor this configuration. (b) Repeat (a) for Figure 4.214.4 Repeat Problems 4.2 and 4.3 for a system where the two segments are both equal to4.5(a) Referring to the relay characteristics of Appendix D (a)-(c), determine the oper-ating time for each relay with a 5.0A pickup, time dial setting of 3, and a faultcurrent of 15.0 A. (b) Which relay, and what time dial setting, should be used if therelay is set at 5.0 A pickup, with a fault current of 15.0 A, and operating time of1.5 s? (c) Select two different relays, their pickup, and time dial settings when thefault current is 20.0 A and the relay must operate in 2s.4.6 For the radial system shown in Figure 4.22, calculate the instantaneous and time-delay overcurrent relay settings at each bus. Assume that the transformer must not bede-energized and that the relays at bus B are "looking into" a transformer differentialand do not need to coordinate with it. Assume that any pickup tap is available, butuse the relay characteristic of Figure 4.5.2100 Actr 30/150 A ctr-20/1Minimum.fault 3000 AMaximum. fault 9000 A2000 A5000 A1000 A3000 AFigure 4.22System diagram for Problem 4.6

Question
92 views help_outlineImage Transcriptionclose1012 112 100 V Figure 4.20 System diagram for Problem 4.2a 1 2 10 2 100 V Figure 4.21 System diagram for Problem 4.2b 4.3 (a) Referring to Figure 4.20, set an instantaneous relay at bus A. Calculate the pickup for faults on buses A and B and discuss the application of the instantaneous relay for this configuration. (b) Repeat (a) for Figure 4.21 4.4 Repeat Problems 4.2 and 4.3 for a system where the two segments are both equal to 4.5 (a) Referring to the relay characteristics of Appendix D (a)-(c), determine the oper- ating time for each relay with a 5.0A pickup, time dial setting of 3, and a fault current of 15.0 A. (b) Which relay, and what time dial setting, should be used if the relay is set at 5.0 A pickup, with a fault current of 15.0 A, and operating time of 1.5 s? (c) Select two different relays, their pickup, and time dial settings when the fault current is 20.0 A and the relay must operate in 2s. 4.6 For the radial system shown in Figure 4.22, calculate the instantaneous and time- delay overcurrent relay settings at each bus. Assume that the transformer must not be de-energized and that the relays at bus B are "looking into" a transformer differential and do not need to coordinate with it. Assume that any pickup tap is available, but use the relay characteristic of Figure 4.5. 2 100 A ctr 30/1 50 A ctr-20/1 Minimum.fault 3000 A Maximum. fault 9000 A 2000 A 5000 A 1000 A 3000 A Figure 4.22 System diagram for Problem 4.6 fullscreen
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Step 1

a) For calculating the pick up current here we have to calculate the line to line current for bus A and B as the generator voltage is 100V and the impedance between is 10 Ω and 1 Ω

The pick up for A will be calculated as:

Thus, at A the pick up current will be 10A.

Step 2

The pick up for B will be calculated as:

Thus, at B the pick up current will be 9.091A

Step 3

b) For calculating the pick up current here we have to calculate the line to line current for bus A and B as the generator voltage is 100V and the im...

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