Trying to parallel (phase) to different circuits

[jack8210]

2 different circuits,from 2 different subs. From each sub is 13.2 wye. Stepped down to 4800 delta by ratio banks. Can't seem to achieve the 10% tolerance across the tie point. Swapped taps at ratio bank on the 13.2(source side) multiple times, but still 60 degrees off. Could there be other factors like load, impedance from ratio bank, or phase imbalance causing this? Or do I just keep swapping taps?

[Orgnizdlbr]

Have you matched base voltage at each sub, then have you matched secondary voltage on each side of the tie point as close to the tie as you can get?

[Old Line Dog]

"Could there be other factors like load, impedance from ratio bank, or phase imbalance causing this?" Thats what I was thinkin... I'm Old School...Not real smart on the "New" analytical shit of the NEW Linework. I just use to do Linework.:D

[wudwlkr]

Impedance or load imbalances got nothing to do with it. What you are dealing with is phase SHIFTING. Every time you send a circuit through a transformer you are going to get some amount of phase shifting. When you are trying to match phases from two different substations on two different sources themselves this can be a real problem. If you were just dealing with trying to parallel two different transformer banks on the same line you can just change connections on the secondaries till you find a match (see any good transformer connection book). Usually can't do this in a substation cause it can screw alot of things up with regards to being able to match up with other circuits in the same sub, relaying, rotation, etc. If you can't match any closer than 60 degrees you are not going to find any combination of connections that will match up. If these two circuits have to be tied together, the only thing you can do is kill one circuit and then pick it up from the other. Make damn sure you check rotation before killing the one circuit and test it again after you re-energize from the other line but before you put load back on and make sure it is the same.

[Lineman North Florida]

We have this same situation with a neighboring utility that will have us pick up one of their feeders periodically and it is always 60 degrees out, like the above poster said we have never found a way to tie them without dropping one side for a momentary outage, never have had a problem with rotation though. On the other hand we have 11 different distribution substations and I have never had a problem tying 2 different circuits from different substations with 600 amp switches. Charlie.

[jack8210]

Have you matched base voltage at each sub, then have you matched secondary voltage on each side of the tie point as close to the tie as you can get?

yes, tested across solid blades for each circuit. readings are 9.2v, 8.2v, 8.2v. too high need to be around 400v.

[jack8210]

Impedance or load imbalances got nothing to do with it. What you are dealing with is phase SHIFTING. Every time you send a circuit through a transformer you are going to get some amount of phase shifting. When you are trying to match phases from two different substations on two different sources themselves this can be a real problem. If you were just dealing with trying to parallel two different transformer banks on the same line you can just change connections on the secondaries till you find a match (see any good transformer connection book). Usually can't do this in a substation cause it can screw alot of things up with regards to being able to match up with other circuits in the same sub, relaying, rotation, etc. If you can't match any closer than 60 degrees you are not going to find any combination of connections that will match up. If these two circuits have to be tied together, the only thing you can do is kill one circuit and then pick it up from the other. Make damn sure you check rotation before killing the one circuit and test it again after you re-energize from the other line but before you put load back on and make sure it is the same.

thanks, we achieved rotation and did a drop and pick to test for phasing. From 13.2 to 4.8 we have an automatic 30 degree shift. If we go back to the it was at 30 degrees shift, do you think we can close that phase in, test the other two? then keep swapping to get it within 10%.

[THE KID]

They used to tell me on the old 2400 we used to have, when they couldn't phase it they would hook 2 phases together. Said it didn't matter if they were the same or not then you would be able to phase the rest. I never did it and wouldn't want to but work with guys who have. Glad we got rid of all of that crap...

[jack8210]

They used to tell me on the old 2400 we used to have, when they couldn't phase it they would hook 2 phases together. Said it didn't matter if they were the same or not then you would be able to phase the rest. I never did it and wouldn't want to but work with guys who have. Glad we got rid of all of that crap...

Our procedures are to close one phase in(from different circuits) then test the other two. the trick is finding the one phase that's the lowest voltage to close in. We get very high voltage sometimes on the other two.

[rob8210]

Apparently the 2- 13.2kv feeders are feed from different sources. Are you able to arrange for the high voltage source to feed the 2 stations that supplies the 2 different 13.2 feeders?