Sign in to follow this  
Followers 0
erik_643

3-Phase Bank Help Needed

Rate this topic:

13 posts in this topic

Here's the problem 3-phase bank one pot goes bad... We dont have another pot of the same kva That has 2 high side bushings so we put a single primary bushing can up that was same kva size...BOOM!!!!! cutout blew on single bushing pot... How can i make a single bushing can work with two other, double bushing cans...

Share this post


Link to post
Share on other sites

Do you guys have engineers? Just kidding. The long and short of it is single bushing transformers are typically used for single phase. The double bushing are used for banks. If you have a Delta bank the transformers are hooked up in series. If you have a Wye bank the transformers have a phase hooked to the X1 bushing and the X2 has a floating neutral. I don't know what kind of bank you have hooked up so it is a little hard to answer the question. What kind of secondary hookup do you have on the bank? Is it a Wye or Delta hookup? If it is Delta you can achieve the same result with 2 Transfomers hooked up in a Open Delta configuration. This would only be a temporary fix though due to load. If it is Wye than you will need a new transformer with 2 bushings on the high side. I'm not to sure about making a single bushing transformer work in this situation. Maybe someone else has an idea

Share this post


Link to post
Share on other sites

NEED MORE INFO........

BUT I HAVE PUT SINGLE BUSHING POTS IN BANKS...WHERE 2 OF THE POTS WERE 2 BUSHING PRIMARY (CONNECTED WYE) AND THEN HAD TO REPLACE A BAD ORDER POT, AND ONLY HAD A SINGLE BUSHING............WHEN YOU DO THIS, YOU NEED TO REVERSE THE LEADS ON THE SECONDARY SIDE OF THAT POT...TO KEEP YOUR ROTATION THE SAME.........

I HAVE AN OLD NETWORK (120/208V SECONDARY) SYSTEM IN PART OF THE DOWNTOWN AREA........ALL THE POTS ARE 2 BUSHING 7620/120/240 (CUT 2 WIRE)....ONE BURNT UP, AND WE HAD NO2 BUSHINGS POTS ON HAND, SO WE USED A SINGLE BUSHING, AND THEN SWAPPED THE HOT LEG AND THE NEUTRAL ON THAT POT, TO KEEP OUR ROTATION THE SAME.................THEN IT WAS ABOUT SIX WEKS, AND WE HAD THE SAME PROBLEM ON THE NEXT PLATFORM BANK DOWN THE LINE............THEN ABOUT 8 MONTHS LATER, THE FIRST BANK WE DID, HAD LIGHTNING COME INTO IT, BURNING UP ANOTHER 2 BUSHING............

THIS TIME WE HAD AN OLD 2 BUSHING THAT HAD BEEN REMOVED FROM ANTHER SECTION OF DOWNTOWN, THAT THE NETWORK AND BEEN REMOVED, AND CONVERTED TO INDIVIDUAL BANKS!! I PURPOSELY SAVE SEVERAL OF THOSE 2 BUSHING POTS JUST IN CASE WE HAD THIS COME UP AGAIN..........BUT I STILL HAVE 2 PLATFORM BANKS, ABOUT 2 SPANS FROM EACH OTHER THAT HAVE 2-2 BUSHING HI-SIDE POTS, AND 1-SINGLE BUSHING HI-SIDE POT IN THEM................ IF WE EVER HAVE TO REPLACE ANOTHER 2 BUSHING IN EITHER OF THOSE BANKS WITH A SINGLE BUSHING, THAT WILL MEAN SWAPPING THE SECONDARY AGAIN, AND THAT WILL BE REALLY CONFUSING, SO THEN THE EINTIRE BANK WILL BE REPLACED :pray::pray:

Share this post


Link to post
Share on other sites
NEED MORE INFO........

BUT I HAVE PUT SINGLE BUSHING POTS IN BANKS...WHERE 2 OF THE POTS WERE 2 BUSHING PRIMARY (CONNECTED WYE) AND THEN HAD TO REPLACE A BAD ORDER POT, AND ONLY HAD A SINGLE BUSHING............WHEN YOU DO THIS, YOU NEED TO REVERSE THE LEADS ON THE SECONDARY SIDE OF THAT POT...TO KEEP YOUR ROTATION THE SAME.........

I HAVE AN OLD NETWORK (120/208V SECONDARY) SYSTEM IN PART OF THE DOWNTOWN AREA........ALL THE POTS ARE 2 BUSHING 7620/120/240 (CUT 2 WIRE)....ONE BURNT UP, AND WE HAD NO2 BUSHINGS POTS ON HAND, SO WE USED A SINGLE BUSHING, AND THEN SWAPPED THE HOT LEG AND THE NEUTRAL ON THAT POT, TO KEEP OUR ROTATION THE SAME.................THEN IT WAS ABOUT SIX WEKS, AND WE HAD THE SAME PROBLEM ON THE NEXT PLATFORM BANK DOWN THE LINE............THEN ABOUT 8 MONTHS LATER, THE FIRST BANK WE DID, HAD LIGHTNING COME INTO IT, BURNING UP ANOTHER 2 BUSHING............

THIS TIME WE HAD AN OLD 2 BUSHING THAT HAD BEEN REMOVED FROM ANTHER SECTION OF DOWNTOWN, THAT THE NETWORK AND BEEN REMOVED, AND CONVERTED TO INDIVIDUAL BANKS!! I PURPOSELY SAVE SEVERAL OF THOSE 2 BUSHING POTS JUST IN CASE WE HAD THIS COME UP AGAIN..........BUT I STILL HAVE 2 PLATFORM BANKS, ABOUT 2 SPANS FROM EACH OTHER THAT HAVE 2-2 BUSHING HI-SIDE POTS, AND 1-SINGLE BUSHING HI-SIDE POT IN THEM................ IF WE EVER HAVE TO REPLACE ANOTHER 2 BUSHING IN EITHER OF THOSE BANKS WITH A SINGLE BUSHING, THAT WILL MEAN SWAPPING THE SECONDARY AGAIN, AND THAT WILL BE REALLY CONFUSING, SO THEN THE EINTIRE BANK WILL BE REPLACED :mf_laughbounce::ernaehrung004[1]:

Trouble, i don't know if you been told lately ,but you are the man :mf_w00t2: What you explained that you have done in the past I let my journeyman read and it worked great... Thanks man

Share this post


Link to post
Share on other sites
NEED MORE INFO........

BUT I HAVE PUT SINGLE BUSHING POTS IN BANKS...WHERE 2 OF THE POTS WERE 2 BUSHING PRIMARY (CONNECTED WYE) AND THEN HAD TO REPLACE A BAD ORDER POT, AND ONLY HAD A SINGLE BUSHING............WHEN YOU DO THIS, YOU NEED TO REVERSE THE LEADS ON THE SECONDARY SIDE OF THAT POT...TO KEEP YOUR ROTATION THE SAME.........

I HAVE AN OLD NETWORK (120/208V SECONDARY) SYSTEM IN PART OF THE DOWNTOWN AREA........ALL THE POTS ARE 2 BUSHING 7620/120/240 (CUT 2 WIRE)....ONE BURNT UP, AND WE HAD NO2 BUSHINGS POTS ON HAND, SO WE USED A SINGLE BUSHING, AND THEN SWAPPED THE HOT LEG AND THE NEUTRAL ON THAT POT, TO KEEP OUR ROTATION THE SAME.................THEN IT WAS ABOUT SIX WEKS, AND WE HAD THE SAME PROBLEM ON THE NEXT PLATFORM BANK DOWN THE LINE............THEN ABOUT 8 MONTHS LATER, THE FIRST BANK WE DID, HAD LIGHTNING COME INTO IT, BURNING UP ANOTHER 2 BUSHING............

THIS TIME WE HAD AN OLD 2 BUSHING THAT HAD BEEN REMOVED FROM ANTHER SECTION OF DOWNTOWN, THAT THE NETWORK AND BEEN REMOVED, AND CONVERTED TO INDIVIDUAL BANKS!! I PURPOSELY SAVE SEVERAL OF THOSE 2 BUSHING POTS JUST IN CASE WE HAD THIS COME UP AGAIN..........BUT I STILL HAVE 2 PLATFORM BANKS, ABOUT 2 SPANS FROM EACH OTHER THAT HAVE 2-2 BUSHING HI-SIDE POTS, AND 1-SINGLE BUSHING HI-SIDE POT IN THEM................ IF WE EVER HAVE TO REPLACE ANOTHER 2 BUSHING IN EITHER OF THOSE BANKS WITH A SINGLE BUSHING, THAT WILL MEAN SWAPPING THE SECONDARY AGAIN, AND THAT WILL BE REALLY CONFUSING, SO THEN THE EINTIRE BANK WILL BE REPLACED :ernaehrung004[1]::mf_w00t2:

Were the single bushing transformers a different polarity? I haven't seen that done. We usually replace a transformer with the same. Match polarity, impedence. We have also been told to watch the tap settings on the newer transformers. The old ones had a 2.5% voltage change and the new ones have 5% only. Someone in standards decided this was the way to go. If we don't have an exact match they usually change the whole bank.

Share this post


Link to post
Share on other sites

The single bushing should have worked. If you have a Delta secondary make sure your X2 is only tied down on one Pot.

Share this post


Link to post
Share on other sites
NEED MORE INFO........

BUT I HAVE PUT SINGLE BUSHING POTS IN BANKS...WHERE 2 OF THE POTS WERE 2 BUSHING PRIMARY (CONNECTED WYE) AND THEN HAD TO REPLACE A BAD ORDER POT, AND ONLY HAD A SINGLE BUSHING............WHEN YOU DO THIS, YOU NEED TO REVERSE THE LEADS ON THE SECONDARY SIDE OF THAT POT...TO KEEP YOUR ROTATION THE SAME.........

I HAVE AN OLD NETWORK (120/208V SECONDARY) SYSTEM IN PART OF THE DOWNTOWN AREA........ALL THE POTS ARE 2 BUSHING 7620/120/240 (CUT 2 WIRE)....ONE BURNT UP, AND WE HAD NO2 BUSHINGS POTS ON HAND, SO WE USED A SINGLE BUSHING, AND THEN SWAPPED THE HOT LEG AND THE NEUTRAL ON THAT POT, TO KEEP OUR ROTATION THE SAME.................THEN IT WAS ABOUT SIX WEKS, AND WE HAD THE SAME PROBLEM ON THE NEXT PLATFORM BANK DOWN THE LINE............THEN ABOUT 8 MONTHS LATER, THE FIRST BANK WE DID, HAD LIGHTNING COME INTO IT, BURNING UP ANOTHER 2 BUSHING............

THIS TIME WE HAD AN OLD 2 BUSHING THAT HAD BEEN REMOVED FROM ANTHER SECTION OF DOWNTOWN, THAT THE NETWORK AND BEEN REMOVED, AND CONVERTED TO INDIVIDUAL BANKS!! I PURPOSELY SAVE SEVERAL OF THOSE 2 BUSHING POTS JUST IN CASE WE HAD THIS COME UP AGAIN..........BUT I STILL HAVE 2 PLATFORM BANKS, ABOUT 2 SPANS FROM EACH OTHER THAT HAVE 2-2 BUSHING HI-SIDE POTS, AND 1-SINGLE BUSHING HI-SIDE POT IN THEM................ IF WE EVER HAVE TO REPLACE ANOTHER 2 BUSHING IN EITHER OF THOSE BANKS WITH A SINGLE BUSHING, THAT WILL MEAN SWAPPING THE SECONDARY AGAIN, AND THAT WILL BE REALLY CONFUSING, SO THEN THE EINTIRE BANK WILL BE REPLACED :Voskl1[1]::Voskl1[1]:

Were the single bushing transformers a different polarity? I haven't seen that done. We usually replace a transformer with the same. Match polarity, impedence. We have also been told to watch the tap settings on the newer transformers. The old ones had a 2.5% voltage change and the new ones have 5% only. Someone in standards decided this was the way to go. If we don't have an exact match they usually change the whole bank.

DAVE..............

ALL OF OUR 7620 POTS ARE ADDITIVE....THE 14.4 POTS WE GET ARE USUALLY SUBTRACTIVE............................WE NO LONGER BUY ANY TAP TRANSFORMERS, EXCEPT I BELIEVE 167KVA AND HIGHER.............

Share this post


Link to post
Share on other sites

If the bank is a 3 pot wye/delta it can of course be operated as a 2 pot bank temporarily according to the amount of load.

As far as mixing up 2 bushing pots with single bushing pots it can be done temporarily on a wye/delta. This will result in the high side floater being grounded down which will cause the bank to operate in not a desireable way and as soon as feasible the single bushing should be changed to a 2 bushing.

In the case of a wye/wye it doesn't hurt a thing to mix up single bushing pots with 2 bushing. The single bushings are a little bit of a cheaper installation anyway. As far as the rotation, if they are the same polarity etc. and it is realized that using the H1 on the single bushing pot (which of course only has an H1) may cause you to have to change the secondary leads then this should be taken into account. If all the 2 bushing pots are using the H1 for the source voltage then nothing on the secondary should have to be changed.

All 14.4 pots should be substractive according to NEMA rules. All 7620 pots will be additive until 250 KVA or larger, according to NEMA rules. dbrown

Edited by dbrown

Share this post


Link to post
Share on other sites

THE BANK WAS WYE/WYE.............H2 WAS THE HOT BUSHING ON THE 2 BUSHING POTS...IF I REMEMBER RIGHT.HAVE SLEPT SINCE THEN, BUT IT'S STILL WORKING, AND BEEN THAT WAY FOR CLOSE TO 6 YEARS!............

Share this post


Link to post
Share on other sites
THE BANK WAS WYE/WYE.............H2 WAS THE HOT BUSHING ON THE 2 BUSHING POTS...IF I REMEMBER RIGHT.HAVE SLEPT SINCE THEN, BUT IT'S STILL WORKING, AND BEEN THAT WAY FOR CLOSE TO 6 YEARS!............

Was the H2 being used as the hot bushing because of jumper clearances?

Share this post


Link to post
Share on other sites
THE BANK WAS WYE/WYE.............H2 WAS THE HOT BUSHING ON THE 2 BUSHING POTS...IF I REMEMBER RIGHT.HAVE SLEPT SINCE THEN, BUT IT'S STILL WORKING, AND BEEN THAT WAY FOR CLOSE TO 6 YEARS!............

Was the H2 being used as the hot bushing because of jumper clearances?

THAT'S IT JOHN :pissedoff[1]:

Share this post


Link to post
Share on other sites

Alright, just wanted to make sure that I understood why the H2 was the high side hot bushing. Now I see what your saying by reversing the secondary leads when you put a single bushing pot in its place. We aren't allowed to swap the H1 with H2 here. But then again, pretty much everything that we are putting up is single bushing pots.

Share this post


Link to post
Share on other sites
Alright, just wanted to make sure that I understood why the H2 was the high side hot bushing. Now I see what your saying by reversing the secondary leads when you put a single bushing pot in its place. We aren't allowed to swap the H1 with H2 here. But then again, pretty much everything that we are putting up is single bushing pots.

THE ORIGINAL BANK WAS BUILT IN THE 40's...PLATFORM BANK ON 'H-STRUCTURES' DOWNTOWN IN THE ALLEYS............ON SOME OF THESE.......I STILL HAVE 3 THAT HAVE NOT BEEN REBUILT........ON 2 OF THEM...TO RE-FUSE THE POT SWITCHES........YOU DO THIS................

SET THE BUCKET UP..........CARRY YOUR EXTENDO STICK AND FUSE........CLIMB OUT OF BUCKET......AFTER YOU SET IT DOWN ON TOP OF THE BUILDING.........THEN RE-FUSE THE POT :pissedoff[1]:

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0