delsol

Will a recloser operate and close the circuit if a phase is open downstream?

Scenario-

100kva padmount from DG system feeds 13.8 to utility.

Phase B fuse opens at cutout on pole. Will the recloser even notice a problem? or did single phase condition occur?

The transformer oil temp pinned the needle. (ferroresonance?)

MDShunk

Short answer.... probably not. The recloser trip point is set high enough for quite a lot of load, and the poletop fuse should be sized just for you. Having said that, if the fault serious enough (hard short) it might have also caused the recloser to trip at least once. You might know that reclosers typically trip and reset three times before they stay tripped.

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-Marc, ABC, XYZ, PhD, 1-2-3

-Someday, I'll wear pajamas in the day time.

delsol

So what you are saying is>>>

Even if the recloser did trip it would probably reset and the transformer (unless it has proper protection) would see single phasing.

Zog

Hard to answer without more info but the point of a recloser is to keep power on the grid and blow faults clear. They care little about your facility transformer.
You have a problem there, take an oil sample an run a DGA on that unit ASAP.

delsol

Already on it...waiting for report

Zog

Good man. Post the results when you get them.

MDShunk

s'zackly right. That's the whole point of a recloser. To keep the maximum amount of people in power and let your fuse blow without bringing down your whole loop section. Your place could be on fire for all the recloser cares.

__________________
-Marc, ABC, XYZ, PhD, 1-2-3

-Someday, I'll wear pajamas in the day time.

TOOL_5150

Does anyone have a graphic of where a recloser tipically sits in a distribution system?

~Matt

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I would rather beg for forgiveness then beg for permission.

MDShunk

I might, but it will be in a book someplace. I'll look. It's more or less at the beginning of each "section", be it a linear section or a loop. Think of it as a circuit breaker that will trip and reset three times, then stay tripped. It lets the fuse on a certain branch blow, or a tree limb to burn off a line, then it resets. Whenever you've seen lights go out for a couple seconds, then come back on, that was very likely a recloser in action.

There are similar devices called "sectionalizers" that are more or less fuses.

__________________
-Marc, ABC, XYZ, PhD, 1-2-3

-Someday, I'll wear pajamas in the day time.

bobelectric

Nothing worse than seeing a recloser doing 3 strikes and you' re out on a clear saturday night.Usually an auto accident.

Zog

Or hot air balloon, those things are attracted to power lines like tornados to trailers.

TOOL_5150

Ok cool. So the reclosers sit on high voltage lines feeding a few neighborhoods. I have seen them in action - my old house, we were fed off of a UG xformer, and every summer the fuse would blow, but one particular time one of the phases melted off. This time I saw it close the circuit 3 times and heard 3 huge bangs. Looked outside, and sure enough smoke was coming out of the pit. They had to replace the transformer it was so badly burnt. I believe this was a summer where we had a week of 115+ degree weather. power was off for 12-15 hours. I was really young then, but still knew the idea of what happened, just didnt know WHY it happened the way it did. Now it all makes sence.

~Matt

__________________
I would rather beg for forgiveness then beg for permission.

MDShunk

Reclosers normally look like little pole top transformers, with a pair of unusually large bushings coming out of the top. Typically found in threes, but sometimes pairs.

__________________
-Marc, ABC, XYZ, PhD, 1-2-3

-Someday, I'll wear pajamas in the day time.

frenchelectrican

The other thing what will affect the life of recloser is the number of cycling of opening and closing espcally on fault current level so that why for so many of X amout of time they will remove it from the source and have them either replace or rebuilt it and recalberated it.

Yeah there is a small CT inside of the recloser it will sense the X amout of current and with locking cam in there now with new recloser they are electronic controlled and it can be able engerised or dengeriszed from remote location. { I am not too crazy with remote control unless you have some means to manually lock that dammed thing }

The recloser verison do come in overhead set up it will look like small transfomer can size or underground verison it will look like small single or triphase transformer.

Here one type of recloser look inside



Keep in your mind there are quite few diffrent verison there.

Merci,Marc

__________________
Pas de problème,il marche n'est-ce pas?"(No problem, it works doesn't it?)

WFO

It can.
Three phase reclosers often perform ground fault tripping by utilizing what is called residual ground relaying.
As noted above, the devices have current transformers around each phase, which each feeding a sensing device (connected in a wye configuration) that will trip the recloser on overcurrent. If the common wire (or neutral if you prefer) of the CT circuit is run through a 4th sensing device before returning to the CT's, that 4th sensor sees the imbalance of the circuit.

As long as the load on the recloser is relatively balanced, this residual current stays below the pick-up point of the sensor. If any phase goes to ground, the imbalance obviously increases and the recloser trips. By the same token, if the recloser is heavily loaded and looses a phase, there is still an imbalance.

Ultimately it depends on how sensitive the ground trip is set.

And yes, it will reclose if it is set to do so, unless it is put in a non-reclose mode in the control cabinet.

Note also that all the trips on a recloser are not the same. The first one or two shots on a relcoser usually follow a much faster time/current curve than the 3rd and 4th. If set correctly, they are faster than the fuse's time/current curve as well. The theory is that the fast trips will "save" the fuse from blowing on a temporary fault (say a snake or bird on the line). The relcoser trips before the fuse does, then recloses after the fault has cleared (hopefully). If the fault remains, on subsequent reclosings, the slower timing of the 3rd and 4th curves allow the fuse to go ahead an blow.