How to Spec meter for 4000aA total load

[Timona]

I have a 4000A total load. How do I spec CT can meter for this? Project is in Palm beach FL. I have no clue because I have never done this before

 

[zbang]

(4000 amp service size or connected load? voltage?)
Is that Florida Power & Light ("florida flicker and flash")?

Find & read the PoCo's "electric service standards" for metering requirement, that will be a good start. And for a service that size, I'd expect the PoCo engineers to be involved; they should be able to tell you what's needed.

 

[tom baker]

At that size service they may want primary metering.

 

[infinity]

I agree the POCO will tell you what's required. In NYC we use a meter section in front of the switchgear that has the CT's in it with a 10 conductor meter cable to the ten-point meter pan.

 

[electrofelon]

I agree the POCO will tell you what's required. In NYC we use a meter section in from of the switchgear that has the CT's in it with a 10 conductor meter cable to the ten-point meter pan.

Yeah typically I see requirements that customer provide a switchboard with metering section for anything over the 800-1000 amps range. I don't even think I've seen a CT cabinet over a thousand amps but maybe they are used in some places

 

[Timona]

In the past, I involved the utility company. My manager just told me 4000A. I just sent out an email asking for more data. I will update.

Yes, it is Florida Power and Lighting.

 

[infinity]

Here's a 2000 amp CT section. 4000 amp is similar.

 

[tank728]

Here's a 2000 amp CT section. 4000 amp is similar.
View attachment 2565138

Nicely shaped

Also what insulation might those conductors be using?

 

[infinity]

Also what insulation might those conductors be using

I believe XHHW.

 

[tank728]

I believe XHHW.

A pain to strip. How would the inspector see it? I prefer a few wraps down by the termination.

 

[infinity]

Good point. You can read the conductor size on the terminal. I believe the installer was covering the BOY colors.

 

[tom baker]

I have only done a few CT setups, there was specific requirements for roping conductors. Not required here or not done yet? When you post quality pictures expect comments!

 

[roger]

I agree with the earlier posts that said the POCO will (should) tell you what is needed. Duke and Progress had it in their customer manuals.

 

[electrofelon]

I have only done a few CT setups, there was specific requirements for roping conductors. Not required here or not done yet? When you post quality pictures expect comments!

I have always wondered why stand alone CT cabinets seem to be the only equipment that has lashing requirements. Anyone seen it on panelboards or switchboards?

 

[tom baker]

I did a 400 amp MCC that required a wood brace secured with rope on the line side of the service disconnect

 

[infinity]

I have always wondered why stand alone CT cabinets seem to be the only equipment that has lashing requirements. Anyone seen it on panelboards or switchboards?

We never lash anything even 4000 amp services get zero lashing. We often do install some fiberglass strut to support the conductors with cable ties.

 

[electrofelon]

We never lash anything even 4000 amp services get zero lashing. We often do install some fiberglass strut to support the conductors with cable ties.

Yet pretty much every CT can I have seen has that label requiring lashing, any idea why? Maybe one of those things that's been that way forever and no one knows why and no one wants to change?

 

[tom baker]

Lashing is keep the conductors secured during a short circuit. The high current results in magnetizing forces that can can cause conductor damage as the conductors try to straighten out.

 

[electrofelon]

Lashing is keep the conductors secured during a short circuit. The high current results in magnetizing forces that can can cause conductor damage as the conductors try to straighten out.

Yes I understand that, but what I don't understand is why the nearly universal requirement (presumably by the manufacturer?) for lashing in a CT cabinet, regardless of size or available fault current. Yet essentially no such requirement in other equipment.

 

[11Haze29]

Couple of things:
What is the voltage? If its 208, then I ask why. You must have a lot of motor loads if you need this much power. You'd be better at 480 and then just use local transformers where you need 208/120.

See if you can get a utility supplied transformer. If you can, they will install secondary metering and provide all CTs and meters.

If utility won't provide transformer, consider primary metering on utility pole and find out what kind of discount you get from the utility for being high voltage and primary metered. Calc expected savings.

With 4000 amps and a standard 5.75pct impedance you'll be at or near exceeding 65KAIC equipment. Specify a higher impedance to reduce AIC. You pay considerably more for 65K switchgear than you do 42K. Going over 65K you pay big money to go to 200K.

Most applications that need this much power are better served at 480V. Also, don't carry a neutral. Don't use 277 lighting and just drop 208/120 transformers where you need them. Do you cost analysis, higher voltage, lower fault currents, will be dollars ahead in the overall construction.