Feeder protection
Feeder protection
(OP)
Utility has some standards and practices they use to set the breaker settings such as using 50% of L-G fault end of the line values for pick up and similar rules.
What criterias are used to set the feeder phase pick up and ground pick up settings. Any good book on this subject. I am not a protection guy ,so excuse my basic question.
What criterias are used to set the feeder phase pick up and ground pick up settings. Any good book on this subject. I am not a protection guy ,so excuse my basic question.






RE: Feeder protection
for feeder protection:
1. instant. element 50-phase: The objective of this element in feeder application is to protect the whole feeder by detecting the minimum phase fault current.
2. time delay element 51- phase: The objective of this element is to protect the feeder or cables against abnormal loading. I> 1.5 I full load
Since there are no relays beyond this relay; a small time delay is normally used taking in consideration "Cold load" which is a short-time increase in load current that occurs when a distribution feeder is reenergized after an outage.
3. instant. 50-earth: The objective of this element in feeder application is to protect the whole feeder by detecting the minimum ground fault current.
4. 51-Earth : The objective of this element is to detect the feeder ground fault. Since the pick-up value is independent of the load, the relay operates only during ground fault. So, the setting is selected to be sensitive.
As stated in section 5.3.2.a:
(For feeder's earth-fault relays, the TAP value is determined taking account of the maximum unbalance which would exist in the system under normal operating conditions. A typical unbalance allowance is 20%.)
To avoid operation on possible unbalances in a normally balanced circuit, a good rule of thumb is to set the ground relays not less than 10% of the maximum load current.
RE: Feeder protection
Thanks
RE: Feeder protection
For distribution feeder protection, you can refer to J. Lewis Blackburn's Protective Relaying book. Also, Cooper has some good technical references for feeder protection that they might give you.
RE: Feeder protection
51 Phase set at or below 67% of end of line phase to phase fault level.
50 Phase set at about same level as 51 phase used for hot line work, and normally not turned on.
50 High set Phase set to pick up for very close in faults, but not always applied.
51 Ground set at 50% of end of line phase to ground level, or 50% of 51 phase set level, which ever is lower.
50 Ground set at about the same level as 51 ground used for hot line work, and normally not turned on.
50 High set ground set to pick up for very close in faults, but not always applied.
Who cares about load, as if it is to close to settings then distribution planning has a problem.
RE: Feeder protection