sorry but another 3 phase bank question

[kooman]

guys we recently built a wye/delta closed 480 volt power bank, 3-240/480 pots, no center tap on x 2, meter guy said the eletronic meter wouldnt work so a trouble guy went and center tapped one x 2and everything now works on meter, correct me if im wrong, but i dont think it should be done this way because now we dont have a true power bank, shouldnt just a ground to the meter be enough? also it has me thinking of another bank we have, open 2 pot bank, 2-240/480 tanks, normaly the lighting pot would have x2 tap but since this is for a well should the x2 be grounded or not? thanks

[kooman]

forgot to mention that on the closed bank all the h2 bushings are floated

[MI-Lineman]

Guess that's where the expertise of a "Electric Meter Services" person would come in as far as a ground (or neutral) for the meter!:p As for the bank itself I believe if ya got an x2 grounded then you got a 240/480 bank? It's a closed wye/delta so of course the h2's are floated!

I don't understand your question about the open bank and the well?

Don't worry I'm sure Door's fingers are a scramblin right now!;)

[Pootnaigle]

Well with it being delta (and I dont know if a ground is needed or not for metering purposes )what we did was not to tap the center pot but rather ground one phase of the 480. It was very common to do em that way, however most electricians cant comprehend that and when they try and troubleshoot a 480 system they invaribly call with one leg dead( trying to check voltage phase to ground instead of phase to phase).

[kooman]

I don't understand your question about the open bank and the well?

on an open 2 pot bank you ground the x2 on your lighting pot when 120 is needed, my question is if you build an open 2 pot bank using 240/480 pots, do you still need to center tap the one pot even though there is no lighting load?

[lewy]

If all you were after was a 480 volt delta secondary, but in order for the metering to work (which I know nothing about metering 3 phase power) you had to ground 1 x2 so what, the customer is getting his 480 delta & the bank will not know the difference. Excluding the metering, if you do not need the 240 you do not ground 1 x2, if you need 240 you would only ground 1 x2.

[MI-Lineman]

I don't understand your question about the open bank and the well?

on an open 2 pot bank you ground the x2 on your lighting pot when 120 is needed, my question is if you build an open 2 pot bank using 240/480 pots, do you still need to center tap the one pot even though there is no lighting load?

K! Now I understand but I guess that would depend on what all they wanted? If the well only needs 3 phase 480 then I wouldn't see usin an x2 cause if ya do you would get 240/480. I don't believe you're usin the "full potential" of the bank if ya ground the secondary coil? Here we've set SINGLE 480 tubs for field pumps and not used an x2. Can't recall the socket set up but I'm sure EL can answer all that?

As far as a grounded leg not everyone does that and some customers or even narrow backs will be confused cause they'll see odd voltages (yeah especially the 0 volts when they check phase to ground!:rolleyes:)! We got rid of most of our 480 banks because of the lightening issues but when ya got an unintentional power ground the call would usually come in as "blinkin lights" cause it drives computers and sensitive electronics crazy. Then the electricians tellin ya "You lost a leg!" Was taught how to find them but we never get to cause they're almost all gone and they wont spend the money usually on gettin us the capacitor and fancy amp meter for just a few banks left?

Anyways I'm surprised Door or Climbsome haven't jumped all over this yet? That's about all I recall?

[kooman]

guys i realize the bank will work either way, but wont tapping the x2 make the bank less efficent or am i totally off base? i am wondering if this is the only way to make the electronic meter happy.

[MI-Lineman]

guys i realize the bank will work either way, but wont tapping the x2 make the bank less efficent or am i totally off base? i am wondering if this is the only way to make the electronic meter happy.

That's what my thought was! "Less efficient" but I couldn't think of the right words when I said "full potential?" Like I said EL might know? Sorry but we don't get to work our three phase metering sockets! You asked if you still needed to use the x2 on an open 240/480 bank and I don't believe so if ya want just 480 but I don't think "open" 480 banks are used much? I'm wonderin if ya had customers wantin the "bitch leg?" We have some customers that actually use the 416v leg for lighting. It's rare here but maybe thats what the customer wanted?:confused:

Sorry I'll stop cause now your questions drivin me nuts!:D

[lewy]

If you grounded the 1 x2 you would still get the full kva out of that transformer. Usually when you use one for a "lighting load" you increase the kva of that transformer, but only because of the increased load, not because the transformer became less efficient.

[spark and bark]

Grounding an x2 wouldn't make the bank function any differently. The meter probably needed some sort of ground reference to work, due to it probably being a 240/480 meter. I guess i just have never seen a strictly 480v meter, might be wrong though...
I guess the only risk there is if the customer has a seperate ground inside the panel to get some 240 load. {only ground a delta once, right?} I always thought it was easier to ground one just in case you had to come back and get 240 or 120 load, depending on bank configuration.

[MI-Lineman]

If you grounded the 1 x2 you would still get the full kva out of that transformer. Usually when you use one for a "lighting load" you increase the kva of that transformer, but only because of the increased load, not because the transformer became less efficient.

No I guess what I'm sayin is if ya don't need single phase power only three phase why would use a 4 wire service? If ya want single and three then fine. Didn't mean to imply (if I did?) there's any more loss than normal just from usin the x2 but if you're not sure if ya got a customer with a large 3 phase load only I wouldn't just tap the x2 and leave? I would think a well (which I'm not sure what kind of well he's talkin about?) would only use three phase for a motor and that's it?

UNLESS OF COURSE YOU'RE TALKIN ABOUT JUST GROUNDIN THE X2 BUSHING AND STILL RUNNIN WITH A 3 WIRE SERVICE?? Missed that!

[wtdoor67]

I've helped build them all ways I think. Straight 480 and straight 240. The self contained meters I'm familiar with didn't care if they were grounded or not. We grounded one leg, didn't ground anything and sometimes mid tapped.

I remember swapping one from 277/480 to straight 480 Delta with a 2 pot open bank replacing the Wye/Wye. Meter man said it didn't matter about the meter as the customer was only using 3 phase.

With the newer electronic meters it might make a difference, I don't know. Midtapping etc. doesn't effect the KVA as someone previously stated.

Maybe EL will chime in here and give us a clue. Stephen can hide his eyes.

[Pootnaigle]

I aint sure n mabey EL can help us out here but I bleve the coils in a 480 mtr are delta.

[Highplains Drifter]

guys we recently built a wye/delta closed 480 volt power bank, 3-240/480 pots, no center tap on x 2, meter guy said the eletronic meter wouldnt work so a trouble guy went and center tapped one x 2and everything now works on meter, correct me if im wrong, but i dont think it should be done this way because now we dont have a true power bank, shouldnt just a ground to the meter be enough? also it has me thinking of another bank we have, open 2 pot bank, 2-240/480 tanks, normaly the lighting pot would have x2 tap but since this is for a well should the x2 be grounded or not? thanks

kooman, how many wires where at the periscope? Did the meter man want a neutral or a good ground? I have to agree with Poot and Door that you can ground one leg of the delta and it will still work. In all actuality one can run the three wire delta to the meter and by getting a good grd connection on your volt meter you can get the voltage reading of each phase to grd and even get the wild leg reading with out having one of the txs center tapped.

[linemanfrog]

We build a Power 480 (some call it a straight 480) here and do not ground any x2 bushings, however we do ground one of the phases (usually a phase) to the system neutral. We either use triplex with the bare conductor used as a phase or use quad and use the bare conductor as a messenger. The transformers are wired 240/480 and of the same KVA.

Keep in mind all this is done only to give the bank a reference to ground. Much in the same way a corner grounded delta primary is done for safety. Without the ground installed if a conductor becomes grounded due to some unforeseen event then the delta will still work. This can pose a serious safety problem. By installing the corner ground on a delta system you make it safer should a different conductor become grounded by some unforseen event since the protection devices will then see a fault and operate.

Our metering departement installs 480 volt meters rated for a delta connection on these types of services.

As an interesting side note. you will not have voltage on the grounded secondary lead, but you will have the same amperage as the other two leads. This type of service is used strictly for balanced loads such as motor loads.

Hope this helps.

[dogman]

The meter will have trouble reporting in, without the neutral. We have been changing our 3 wire corner grounded banks, to 4 wire.

[climbsomemore]

Adding a grounded wire (4th wire at the "neutral position", so to speak) wont affect the voltage or "efficiency" of the bank. If the bank has a grounded connection on the utility side... and the customer wants motor or power load served.. the customer simply runs 3 phase wires (plus bonding/grounding required by the NEC) to his motors and he's done with it.

The digital meter is the issue here. I am not a meter man... but when mechanical meters ruled the roost... the sockets had a teaser wire you could add to a lug and jumper a ground to make the meter run correctly.
I would assume that a digital meter would work of the teaser also (but I could be wrong) and would anticipate that running a "neutral" in with the service may just be a company policy of some sort.

[kooman]

guys thank you for all the help, our systen doesnt have alot of straight power banks, most have the x2 tapped because of lighting load. for some reason i thought tapping one pot made the bank less efficent, thats what i like about this site i allways learn something new. thanks again

[kooman]

We build a Power 480 (some call it a straight 480) here and do not ground any x2 bushings, however we do ground one of the phases (usually a phase) to the system neutral. We either use triplex with the bare conductor used as a phase or use quad and use the bare conductor as a messenger. The transformers are wired 240/480 and of the same KVA.

Keep in mind all this is done only to give the bank a reference to ground. Much in the same way a corner grounded delta primary is done for safety. Without the ground installed if a conductor becomes grounded due to some unforeseen event then the delta will still work. This can pose a serious safety problem. By installing the corner ground on a delta system you make it safer should a different conductor become grounded by some unforseen event since the protection devices will then see a fault and operate.

Our metering departement installs 480 volt meters rated for a delta connection on these types of services.

As an interesting side note. you will not have voltage on the grounded secondary lead, but you will have the same amperage as the other two leads. This type of service is used strictly for balanced loads such as motor loads.

Hope this helps.

could someone please explain the details on how exactly you ground a delta phase or corner ground? i know the about the concept but i have never learned much about this subject because we dont use anything like this on our system, but i would like to learn about it. thanks

[nsmith@sunflower.net]

Some meters need a referance to ground. It depends on the form of meter, but now days a guy can get a meter to cover many different types of banks.

[climbsomemore]

Seems these newfangled digital meters need a neutral to make the display run,,, and that neutral needs to go back to the source.

[electriklady]

Adding a grounded wire (4th wire at the "neutral position", so to speak) wont affect the voltage or "efficiency" of the bank. If the bank has a grounded connection on the utility side... and the customer wants motor or power load served.. the customer simply runs 3 phase wires (plus bonding/grounding required by the NEC) to his motors and he's done with it.

The digital meter is the issue here. I am not a meter man... but when mechanical meters ruled the roost... the sockets had a teaser wire you could add to a lug and jumper a ground to make the meter run correctly.
I would assume that a digital meter would work of the teaser also (but I could be wrong) and would anticipate that running a "neutral" in with the service may just be a company policy of some sort.

Sorry guys.....laptop took a dive this weekend......off to the "geek Squad"....borrowed my daughters till it is repaired. Climbsomemore is absolutely right.........there is a tickler wire from the bottom number 3 jaw to the neutral......without that connection a digital meter will not display at all......and on the old mechanical meter only 1/3 of the load will be metered. Ran into this problem right after I started working self contained 3 phase. Since installation the tickler was attached to the neutral but the other end was not connected to the jaw......original meter man did not catch it on installation.....I caught it when I went to exchange it with a new GE digital 16S meter......blank display once installed.....pulled it back out and found the tickler was not connected. That whole exchange was one of the biggest pains in the a$$ I have yet to work on and hope not to have to deal with one like it again....Did I mention the bypass/release lever did not work, right off the bat.....and those meters are a bitch when the jaws dont release. I knew I was not gonna have fun on that one from the minute the meter cover popped off like it was shot out of a cannon, once I unlatched it. But yes..... the digitals need a reference to ground....

[Highplains Drifter]

Sorry guys.....laptop took a dive this weekend......off to the "geek Squad"....borrowed my daughters till it is repaired. Climbsomemore is absolutely right.........there is a tickler wire from the bottom number 3 jaw to the neutral......without that connection a digital meter will not display at all......and on the old mechanical meter only 1/3 of the load will be metered. Ran into this problem right after I started working self contained 3 phase. Since installation the tickler was attached to the neutral but the other end was not connected to the jaw......original meter man did not catch it on installation.....I caught it when I went to exchange it with a new GE digital 16S meter......blank display once installed.....pulled it back out and found the tickler was not connected. That whole exchange was one of the biggest pains in the a$$ I have yet to work on and hope not to have to deal with one like it again....Did I mention the bypass/release lever did not work, right off the bat.....and those meters are a bitch when the jaws dont release. I knew I was not gonna have fun on that one from the minute the meter cover popped off like it was shot out of a cannon, once I unlatched it. But yes..... the digitals need a reference to ground....



EL, then how do utilities that only run the three wire delta to the periscope get their digital meters to work? Are you sure it takes a neutral or a good grd for it to operate?

[topgroove]

If you think about it, take a look at a residential 120/240 volt meter. you only have 4 spades and no neutral conection. If you take one apart you'll find a small 240 volt transformer with a bridge rectifier to supply DC voltage for the circuit board and display.

[Highplains Drifter]

If you think about it, take a look at a residential 120/240 volt meter. you only have 4 spades and no neutral conection. If you take one apart you'll find a small 240 volt transformer with a bridge rectifier to supply DC voltage for the circuit board and display.


Yes and when putting a hot service back on a house, if I can pull the meter I heat the hot legs first and then that bare neutral wire. I then reinstall the meter. Saves having to worry about getting your hot connections into that bare neutral.

[topgroove]

Yes and when putting a hot service back on a house, if I can pull the meter I heat the hot legs first and then that bare neutral wire. I then reinstall the meter. Saves having to worry about getting your hot connections into that bare neutral. ;)Carefull with that drifter , remember the customers nuetral is attached to a groundrod and may even have communication grounds bonded to it.

[MI-Lineman]

;)Carefull with that drifter , remember the customers nuetral is attached to a groundrod and may even have communication grounds bonded to it.

:eek:YIKES! Your right Top, those neutrals are bonded in the socket (some run straight through!) and go directly in the house panel where they are usually bonded to customer grounds and like you said communications even bonds their ground to the customers! Still would take care, which I'm sure H.D. does, to not bump the legs!!!

[electriklady]

EL, then how do utilities that only run the three wire delta to the periscope get their digital meters to work? Are you sure it takes a neutral or a good grd for it to operate?


Drifter......for a 3 phase 4 wire.......which is all Penelec offers..... we use a auto ranging 16S digital meter...........3 jaws on top and 4 on bottom......as I said the 3rd jaw is attached to the neutral...........now for a 3 phase, 3 wire......you would use an auto ranging 12S meter.......looks just like a residential meter.....CEPT it has a jaw at either the 9 oclock position(ours are all at 9 oclock) or the 6 oclock position and that jaw is B phase...which may or may not be grounded. Now First Energy in Ohio still offers a 3 wire 3 phase.....but like I said....if you want 3 phase in Penelec land it will be a 4 wire. We use the 12S for our single phase........ run off a 3 phase bank(120/208 network meters)....and they are not auto ranging.....they will only handle 240 volts..........

The metering can get a little confusing if you dont work with it all the time...

[THE KID]

EL, are you putting PT an your 480 banks now? All 480v meter can that don't have PT on them have big stickers that say 480 Volts. We are in the process of putting Pt on all those banks now. What a pain I miss the good ol days when you were able to just put on the rubber gloves and check voltage or work on it.