Power system protection:
Design the protection for the power system shown below:
28 miles
5 miles
Fdr. 1: ‘fault-max = 9.0 kA ‘fault-min = 6.5 kA ‘load-max = 600 A Fl Lateral: ‘fault-max = 8.5 kA ‘fault-min = 6 kA ‘load-max = 25 A F2 Lateral: ‘fault-max = 4.5 kA ‘fault-min = 2.5 kA ‘load-max = 25 A
55 miles
Sectionalizer Lateral: ‘fault-max = 3.5 kA ‘fault-min = 1.5 kA
‘load-max = 25 A
F3 Lateral: ‘fault-max = 2.0 kA ‘fault-min = 1.0 kA ‘load-max = 25 A
Main Feeder at Recloser: ‘fault-max = 4.0 kA ‘fault-min = 2.0 kA ‘load-max = 300 A
Specifically,
1. Specify distance relays to use on the three 138kV lines, and describe how each relay should be set. State the setting distances in miles instead of the usual ohms or siemens. Diagram the VT and CT connections on a detailed oneline diagram, and show where each VT and CT is located.
2. Tell which relay(s) would detect a fault on the 138kV bus.
3. Draw a detailed oneline diagram (including CTs and relay wiring) of the protection for the 44MVA transformer. Select a relay for this application, and discuss how the settings would be determined.
4. Show the protection scheme for the 24.9kV distribution bus. Select a relay for this application.
5. Design coordinated overcurrent protection for Fdr. 1. Select a relay for 50/51 protection and a line recloser. Construct a TCC showing the relay, recloser, Fl, F2, and F3. Assume that >80% of faults on this circuit are temporary.
GRADUATE STUDENTS: In addition to Requirements 1-5, please also do the following: a. Discuss how the sectionalizer on the first lateral downstream from the recloser on Fdr. 1 will change the reliability as compared to using a fuse at that location. b. How would your protection strategy for Fdr. 1 change if >80% of the faults on that circuit were permanent.