HW05 EE6560 Power System Protection 1
For HW05 assume that the ground overcu
ent Device 51N provides adequate and sufficient single line to
ground fault coverage (perhaps you'll do 51N in a future homework.) Concentrate on the phase overcu
ent
Device 51 protection of the primary zone of this feeder for each of the following cases. Line length is from
eaker to recloser,R. This utility uses a minimum Detection Margin of 1.5 and a minimum Load Margin of 1.15
1. What EOL (End Of Line) bolted fault type yields the lowest phase amps?
2. Determine the primary phase amps for
a. bolted EOL fault,
. highest phase overcu
ent Device 51 pickup amps primary that satisfy the Detection Margin,
c. the maximum load amps primary that meet the Load Margin, and
d. the resulting maximum load MVA allowed.
e. Show hand calculations for 4.16kV case then can use EXCEL or ASPEN for the rest of cases.
Note: To simplify your calculations I'm providing reactance only, use 1.0 pu nominal source voltage. If you
think you need Zo assume it's 3Z+. These line reactances are for 954 ACSR Cardinal conductor rated 1009 A for
summer normal conditions.
Read Blackburn Chapter 12 pages XXXXXXXXXXAs a minimum page turn to assure you are familiar with this
material.)
Paul Nauert 2/25/2023