# How to increase the working voltage of a cable?



## Anthony666 (Aug 22, 2016)

I am going to be installing some current transformers to measure the current flow on conductors in an electrical panel. The cable connected to the current transformers has a rated voltage of 300V so according to code I can install these current transformers in a panel that distributes single phase 120V/240V power.

If I want to measure the current in conductors in a 3 phase, 600V panel then NEC 300.3 (C)(1) says that those same current transformers need to have cable rated for 600V.

My question is can I use the current transformers with the 300V cable if I install an insulating sleeve over the 300V cable? I was thinking of sliding some heat shrink tubing over the current transformer wire to provide an extra thickness of insulation thus increasing the working voltage to 600V.


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## MechanicalDVR (Dec 29, 2007)

I would highly doubt the only difference in a 300v rating and 600v rating is the wire insulation. So I would say if a device needs to be rated for 600v you can't make a field upgrade like this to a lesser rated device.


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## splatz (May 23, 2015)

I know there is heat shrink available that has a UL listing and a 600V insulation rating printed on the tubing. I do not however know whether that satisfies all the relevant rules.


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## Majewski (Jan 8, 2016)

Are you doing this by nec or cec?


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## Anthony666 (Aug 22, 2016)

These installations will be for North America so it will have to comply with both NEC and CEC.

I am an electronics engineer but am by no means an expert in electrical codes so for clarification I know the NEC is the National Electrical Code. Is CEC the Canadian Electrical Code? I thought that because the electrical systems in the US and Canada are so similar that there would be an electrical code that would apply to both countries.


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## macmikeman (Jan 23, 2007)

Are the transformers themselves rated for the higher voltage is the question that needs to be asked here, not the conductors sleeved with shrink tube.
Stuff is known to start smoking and smells funny when you hook it up to higher voltage than designed for.......


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## MechanicalDVR (Dec 29, 2007)

Keep this on hand just incase of emergency!


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## Anthony666 (Aug 22, 2016)

Yes, the transformer itself is has a working voltage of 0.66 kV and a dielectric with stand voltage of 2 kV. The existing transformer with it's 300V cable is UL certified.

I just need to get a 600V rating on the secondary side cable.


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## emtnut (Mar 1, 2015)

Anthony666 said:


> Yes, the transformer itself is has a working voltage of 0.66 kV and a dielectric with stand voltage of 2 kV. The existing transformer with it's 300V cable is UL certified.
> 
> I just need to get a 600V rating on the secondary side cable.


As a manufacturer ... you can't just shrink wrap wire, and hope it will do :no:
You would have to get it UL listed.

Why don't you do it right, and get a CT with UL1015 wire to begin with :blink:


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## Anthony666 (Aug 22, 2016)

Yes, doing it right and getting 600V cable on the transformer is the right way to go. However, I work at at start up company so we are sensitive to part costs so we are using a Chinese supplier. Further, our volumes are not large enough yet to drive the volumes that would make it cost effective for a Chinese supplier, or any supplier, to certify a new part. Etc, etc, etc.

The quick solution is to be able to slide some tubing over top of the existing cable, and Bob's your uncle. However, the uncle Bob solution still needs to be to code.


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## macmikeman (Jan 23, 2007)

Anthony666 said:


> Yes, doing it right and getting 600V cable on the transformer is the right way to go. However, I work at at start up company so we are sensitive to part costs so we are using a Chinese supplier. Further, our volumes are not large enough yet to drive the volumes that would make it cost effective for a Chinese supplier, or any supplier, to certify a new part. Etc, etc, etc.
> 
> The quick solution is to be able to slide some tubing over top of the existing cable, and Bob's your uncle. However, the uncle Bob solution still needs to be to code.



I've made bob my uncle by sliding heat shrink tubes over old crumbling light fixture wires about two hundred fifty times now.


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## emtnut (Mar 1, 2015)

macmikeman said:


> I've made bob my uncle by sliding heat shrink tubes over old crumbling light fixture wires about two hundred fifty times now.


I take it that was Acme Electric thou .... Not MacMikeman Manufacturing Co. Ltd. :shifty:


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## HackWork (Oct 2, 2009)

He didn't have it in him to even start Acme Electric.

It takes a special kind of man to be a real hack.


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## Big John (May 23, 2010)

It's my opinion that 300.3(C)(1) doesn't apply here. It's extremely common for CTs to not be rated at the insulation of the system they are monitoring, and in many applications that would be impossible. 

I'm not sure whar article more clearly addresses it, but if this is a piece of manufactured equipment it's not under the perview of the NEC regardless.


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## emtnut (Mar 1, 2015)

Big John said:


> It's my opinion that 300.3(C)(1) doesn't apply here. It's extremely common for CTs to not be rated at the insulation of the system they are monitoring, and in many applications that would be impossible.
> 
> I'm not sure whar article more clearly addresses it, but if this is a piece of manufactured equipment it's not under the perview of the NEC regardless.


In that situation, would the CTs be in a cabinet/conduit with the HV cables ?

I think in this case the mfr would have to state that the equipment is suitable for 600V installations .... but couldn't with 300V leads.


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## Big John (May 23, 2010)

emtnut said:


> In that situation, would the CTs be in a cabinet/conduit with the HV cables ?


 Very often not. Very common to see regular 600V wiring in MV compartments just zip-tied to insulators.


> I think in this case the mfr would have to state that the equipment is suitable for 600V installations .... but couldn't with 300V leads.


 I'm sure there's a regulation somewhere. Honestly, it's not something that would worry me, and if it did, I think the 600V sleeve idea is fine. But I don't make the rules.


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## macmikeman (Jan 23, 2007)

HackWork said:


> He didn't have it in him to even start Acme Electric.
> 
> It takes a special kind of man to be a real hack.



Quiet, I haven't finished my commercial job yet, no time for fooling around at the moment.


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## HackWork (Oct 2, 2009)

macmikeman said:


> Quiet, I haven't finished my commercial job yet, *no time for fooling around* at the moment.


Exactly. It's all a joke to you, while to the real hacks it's a way of life.


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## PlugsAndLights (Jan 19, 2016)

Anthony666 said:


> These installations will be for North America so it will have to comply with both NEC and CEC.
> 
> I am an electronics engineer but am by no means an expert in electrical codes so for clarification I know the NEC is the National Electrical Code. Is CEC the Canadian Electrical Code? I thought that because the electrical systems in the US and Canada are so similar that there would be an electrical code that would apply to both countries.


There's the NEC (National Electrical Code), the CEC (Canadian Electrical 
Code) and several more as many jurisdictions within Canada and the US
have their own codes. Ontario for instance uses the OESC (ont elect 
safety code). 
None of this matters. As a manufacturer, low budget or not, your products
will need to meet a different, though related, set of requirements. Your
products will also need to be tested by an accredited testing facility to 
ensure the design meets these requirements. If you want to distribute
throughout NA, UL/ULc would be the most widely recognised safety
standards and testing body. 
Unfortunately, I have no idea how you go about finding the requirements
of the standards bodies or how to submit products for testing. Perhaps 
a web search for some of the terms above then scanning the results
for one in your area. 
Good Luck,
P&L


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