Help me find some CT shorting clips

[bbaumer]

Years ago when replacing some switchboard meters the guy I was working with had some clips you could use to short out the CT's if there was not a shorting block installed.

They looked kind of like test leads only the spring loaded ends would actually pierce the insulation of the CT leads. Made a very small cut/piercing. You clipped one end to the + lead and one to the - or common if it was a wye and shorted the CT out so you could replace the meter or install permanent shorting blocks.

I need a set of these clips but cannot find them anywhere.

Anyone know what I'm talking about and know where to get them or even what they are called?

 

[bbaumer]

Aha! Found it. Sorry.

http://us.fluke.com/usen/products/AccessoryDetail.htm?cs_id=204(FlukeProducts)&catalog_name=FlukeUnitedStates

 

[LarryFine]

Glad we could help! :grin:

 

[djohns6]

I highly recommend that you NOT use that device to short out a current circuit . If you have ever witnessed an open CT , you wouldn't ask why .
Find another , safer way to short out the circuit prior to opening it .

 

[SEO]

I agree with djohns6.

 

[danickstr]

how high is the voltage/current on the primary your CT is on?

If there is a lot of power current going through it, it will act as a transforming channeler of sorts and could shoot a lot of impeded VA's

 

[bbaumer]

First off, yes I have opened the secondary of a CT before a couple of times. Once out of ignorance years ago and once by accident.

Yes, it drew an arc and made me jump. Something about a current source through an infinite resistance creates an infinite voltage. Well, not really but the whole Ohms law thing applies, hence the high voltage arc. Buzzed really loud too as I recall.

Second, the maximum current flowing/circulating through the leads when shorted is 5A due to the CT ratio.

I installed/helped install some 70+ meters at this site years ago and am being called on now to replace one. All the switchboards at this campus have 800:5, 1600:5, 2000:5 etc. CT's depending on the size of the board. Most boards are very lightly loaded as compared to their rated capacity. Ex. 2000A board may have 400-600A on it. With a 2000:5 CT that would only be about 1.2 to 1.5A on the CT secondary. These clips can handle that easily and are rated for it.

 

[djohns6]

I'm not concerned with wether the clip can carry the current , but rather , the method of piercing the insulation and making a secure connection .
There are NO shorting blocks ANYWHERE in the circuit ?

 

[bbaumer]

I'm not concerned with wether the clip can carry the current , but rather , the method of piercing the insulation and making a secure connection .
There are NO shorting blocks ANYWHERE in the circuit ?

No. I could swear we added them everywhere that did not have them on the first go 'round 9 or 10 years ago but lo and behold none on this board. There is a terminal block but it is just that, a terminal block. Not a shorting block.

I have a few of options.

1. Shut the board down and go to work.
2. Short out using the clips and immediately install jumpers on the terminal block to create a safer condition.
3. Attempt to loosen the screws on the terminal block and install jumpers and hope not to open one of the CT secondary circuits. I think this is a slim chance and not as safe as using the clips.

Shutting the board down is possible but would be a major disruption for the Owner. I think they would go without metering before they would do this.

 

[djohns6]

Option two sounds pretty reasonable . Use a wire jumper with forked " sta-kons " . Just loosen the screw and slide it under .

 

[jdsmith]

Option two sounds pretty reasonable . Use a wire jumper with forked " sta-kons " . Just loosen the screw and slide it under .

I would choose option 2a - short out using the clips, install shorting blocks, and re-terminate CT wiring on proper shorting blocks. I just priced the blocks yesterday - $27 is a pretty cheap one-time cost to avoid having to go through that risky maneuver more than once.