Need for a recloser in a distribution circuit
Need for a recloser in a distribution circuit
(OP)
Two questions in regards to this:
1) At what point (or conditions) do you need a recloser on an overhead line to cover for faults toward the end which may not be picked up by the substation breaker relaying? 556.5 AAC conductor @ 22kv through out the whole feeder.
2) Can an SEL-351 or SEL-551 be configured to do fast and slow curves (ie fuse saving to fuse blowing)? Or do I need a specific relay/pole mount recloser to accomplish this?
1) At what point (or conditions) do you need a recloser on an overhead line to cover for faults toward the end which may not be picked up by the substation breaker relaying? 556.5 AAC conductor @ 22kv through out the whole feeder.
2) Can an SEL-351 or SEL-551 be configured to do fast and slow curves (ie fuse saving to fuse blowing)? Or do I need a specific relay/pole mount recloser to accomplish this?






RE: Need for a recloser in a distribution circuit
You can set multiple 51 elements. The 551 (or is it the 551C?) has two; the 351 has a two for phase if you use both the 3-phase and the three 1-phase elements. To get two 51s for residual you need to wire the residual connection into the relay and then use 51N for one and 51G for the other. Supervise the faster of the two with the shot count wordbits; I'd leave the slower one active at all times.
RE: Need for a recloser in a distribution circuit
RE: Need for a recloser in a distribution circuit
RE: Need for a recloser in a distribution circuit
For those who know- is there a general rule of thumb when a distribution lines gets to long?
RE: Need for a recloser in a distribution circuit
RE: Need for a recloser in a distribution circuit
RE: Need for a recloser in a distribution circuit
As for fuse saving, we've gone the fuse blowing route to reduce the blinks on our system which does result in more truck rolls for temporary faults. Depending on the curves you use for the fast trips, the ground will get most of the operations but you'll still want to check the phase to provide complete coordination. To go along with bacon4life's comment, add the operating time and some delay for your breaker/recloser to the curves and you'll likely see some fuses clearing while the breaker is opening.
RE: Need for a recloser in a distribution circuit
Also, when I calculate minimum current for an end fault on a feeder for the determination of a recloser, I just use the minimum anticipated fault current at the substation plus the line impedance (R and X) components? What drives my question being that while the feeders in question are average length, normally open switches can significantly extend the line length. I'd like to either have the line crews covered, or have warnings in the switching procedure that to much back-feeding creates a "blind spot".
RE: Need for a recloser in a distribution circuit
http://www.pes-psrc.org/Reports/Fault%20Current%20...
RE: Need for a recloser in a distribution circuit
In our experience, we've found faults to be bolted the majority of the time and on the rare occasion high impedance. We'll typically use 30% of maximum available fault current for the minimum fault current at each line segment for coordination review.
RE: Need for a recloser in a distribution circuit
@brain: Thank you for your input, and the 30% number. The systems I deal with are far from radial, even if no recloser or auto loops are present, there are plenty or normally open gang switches. A short line can grow in lenghth for a number of reasons. Your ground pickup is 1/3 the phase value?