Reclosers coordination 2

[pajce]

Hi all:
I have hydraulic Cooper reclosers on typical distribution feeder, and need to coordinate them. Question is:
for fault downstream of second one both of them go on the fast curves, second operation both reclosers are on their slow curves, say there wasn't enough oordinating margine, and both of them trips simultaneously again, on third operation upstream one doesn't trip (one downstream trips). So, now downstream one has one more operation and if the fault still exist it will lock-out before upstream one in next (and last one for downstream recloser) operation.
Is criteria A+3B (lock out) before second last A+2B clears valid for coordination? (assumes 4 operations in sequence of the recloser, one fast and three slow)
If it is, then how can I read that? Say if time margin between 2 reclosers on 1000A current is only 4 cycles and the manufacturer recommends 12 cycles for coordination on curves, so it means for my margin of 4 cycles it is possible simultaneous operation of both reclosers, if I use above rule for coordination in second sequence of operation 4 cycles will became 8 cycles, in third 12 cycles time margin. Something doesn't seem right here.

Anybody?

 

[dpc]

If the time separation between the two curves is less than the recommended 12 cycles, then there is the possibility of simultaneous operation of both reclosers. Eventually one or both will lockout or the fault will clear. If both trip, then the next operation has the same 12 cycle separation requirement.

With these reclosers in series, the overall sequence can get pretty long if you can't coordinate at least the slow operations. New electronic controls allow the upstream recloser to count the downstream operations and avoid some of the issues related to reclosers in series.

BTW, three slow operations is pretty unusual. Normally we see (and recommend) only two slow operations.

 

[JensenDrive]

Please reword your last paragraph. I am not following the 4/8/12 cycle story you are describing. However, if you are addressing a lack of coordination by having fewer trips to lockout on the downstream recloser: Well, it seems crude, but it sounds like it would work. In the end, the downstream device locks out as long as they always both trip. The glitches are more wear and tear on the upstream device and more/worse customer blips. Hopefully you have few faults.

Where does the hydraulic recloser get its power from? Does it come from a bushing on the upstream side? If the upstream recloser trips, the downstream recloser looses power. Will that affect the ability of the downstream recloser to close?

 

[pajce]

Thanks Dpc.
Dpc:
again here is my question, little bit reformulated:
I need to examine coordination between Cooper single-phase reclosers L-140 and 4H-100 with sequence on both being B13.

On fast curve they both go instantaneously at 1000A (3 phase fault current at OCR 4H(100), on slow curves they will likely go both again, since TCI@1000A is less then 12 cycles ( it is around 8 cycles).

So, my question is: how can I describe this coordination as good or not? We have some rules (in Utility I work for) that says it's OK coordination as long as the downstream recloser locks-out before the upstream recloser clears on second last operation on slow curve. This means intersection between curves A+3B and A+2B !!! So my 8 cycles margin on slow B curves, will ultimately become (8+8+8=24 cycles margin between A+3B and A+2B curves)

I have a problem understanding if this is actually correct criteria for coordination. Principle is correct, no doubt in my mind, but not plotting of these curves!

This 24 cycles margin would be true if both reclosers are left to go through their sequence independently of each other , and we are measuring their respective (and total) clear times. But in reality downstream recloser will be affected by the upstream recloser behavior. This means if they both simultaneously trip on first fast and first slow curve, they will reclose both twice and now we have exactly the same scenario as the first time, they are "racing" on slow B curves again. On 8 cycle margin, not 16 cycles margin! (Is this correct?) They may or may not trip again simultaneously. But what's important is that what was time margin between their curves before first slow operation will be the same time margin before second (and third) slow operation. Margin is not accumulative. Is this right? So, we can’t say that margin was 8 cycles on slow B curves, and after 1st slow operation margin just increased to 16 cycles. Is this correct?

That being the case, is it fair to say that we are looking for possibility of upstream recloser tripping just one less time (and enough for good coordination) then downstream recloser?

JensenDrive:
Coorer recloser trips on magnetic field throuh the rated current coil. It uses oil for timing as well.

 

[dpc]

Time margin is not cumulative. I'd say coordination was not good if both reclosers are tripping (or could both trip) on their slow curves for the same fault. The downstream recloser should operate before the upstream recloser when both on are their slow curves. If it doesn't, you don't have good coordination.

 

[wfowfo]

Would the rest of your coordination allow you to go to a "C" curve on the down stream device?
Equally sloppy (but I've used it when nothing else would work) is to go 1 & 3 on the downstream unit and 2 & 2 on the upstream.

 

[apowerengr]

Sounds like you're describing operation at 1A3B? If so, 1004H and 140L would not be considered to be "coordinated" as the downstream customers could see multiple operations from both devices. Consider if you need the fast trip on the 140L and whether or not you can slow down the 140L to another curve by giving up one shot on the reclosing. Cumulative time is important when considering upstream coordination (cumulative heating on power fuses, etc.) As mentioned sequence coordination functions on Cooper electronically-controlled reclosers can help with the miscoordination on fast curves but it won't help the 100B-140B issue at higher fault current levels. How fast are you reclosing - standard 2 seconds or optional 4 seconds?

 

[pajce]

Thanks everybody.
I think you proved my point. Thanks Dpc. Thanks apowerengr.

 

[pajce]

It's 2 seconds open time interval apowerengr.
We use 1 fast since our experience says 75% of the faults are cleared on that first operation.