ECN Forum
Posted By: trekkie76 CT cabinet with only 2 CT's in it - 02/06/09 09:46 PM
[Linked Image from electrical-photos.com]

I found this photo on the internet and am wondering why 2 things.

1. Why is there only 2 CT's, with the B phase unmetered?
2. If the color code is right, this is a 208Y/120V 4 wire system. Where is the grounded(neutral) conductor? Isn't this a violation of 250.24(C)?
I have never seen a CT cabinet that didnt have a CT for each phase. Maybe someone could steer me in the right direction.
Thanks,
Gary
Edited to add code section
Posted By: HotLine1 Re: CT cabinet with only 2 CT's in it - 02/06/09 10:53 PM
Disregarding the 'color code'.....600 volt fuses in disco, looks like 3 phase, 3 wire (delta) 480 volt service.

I only came accross this twice, a long time ago; industrial
Posted By: LarryC Re: CT cabinet with only 2 CT's in it - 02/06/09 11:24 PM
Corner grounded Delta system?

Larry C
Posted By: Trumpy Re: CT cabinet with only 2 CT's in it - 02/07/09 12:45 AM
Shouldn't that CT enclosure and the meter base enclosure also have a ground wire attached to them and run back to that ground wire in the Disconnect?
Posted By: JoeTestingEngr Re: CT cabinet with only 2 CT's in it - 02/07/09 01:25 AM
Whether corner grounded or not, don't 2 CTs give you all you need on a delta??? Not true with a wye.
Joe
Posted By: ameterguy Re: CT cabinet with only 2 CT's in it - 02/07/09 01:59 AM
A Delta service is metered with two CTs. The service being either corner grounded or not, does not change the metering setup.
The picture also shows a three phase, four wire meter socket. I think either the CT configuration is wrong or the socket is wrong.
The only other possiblty when you see two CT's there it possbilty that is used for electric motor load only { I did see it in few place like that however POCO don't like it much }

Merci,Marc

P.S. look like 60 a 240 or 208 volt otherwise 480 v 30 amp due the conductor size looks pretty small.
Posted By: HotLine1 Re: CT cabinet with only 2 CT's in it - 02/07/09 05:52 PM
Looks like max 30 amp fused disco at 480/600 volt as I look again.

POCO here supplies CT's and meter pan, and installs wiring from CT's to pan.

Posted By: RODALCO Re: CT cabinet with only 2 CT's in it - 02/07/09 09:08 PM
It looks like an overkill to me for CT metering.
That size cable looks like 16 or 25 mm˛ and the power usage could have been metered directly with a whole current meter.

This CT set up adds hugely to the overall installation costs.
© ECN Electrical Forums