# 13.8kv Motor Terminations



## Kevhuff26 (Dec 17, 2018)

Hello my fellow electricians,

I have a situation at my work where the B phase in the motor connection box blew up. The amps got extremely high on B phase FLA is around 120amps and current got up to around 4600amps. The motor then faulted on a ground fault at around 100amps. The bottom of the tape job where the lug meets the bus bar is where the fault occurred. The bolt termination points remained intact but the bottom where the lug was attached blew out. The B phase connection point is approximately 10-15 inches away from the Frame of the connection box. During a normal medium voltage motor termination our guys use VC tape, High voltage tape and then super 33. We use many layers. Upon investigation of the tape job it seems like there was no use of the HV tape “the red/orange tape” and they used rubber C130 but a minimum amount and then just a bunch of super 33 and VC “varnish cambric”. People are leaning to believe the tape job is the cause of the fault. I know there are certain clearances for 13.8kv connections. I have seen motors that had enough clearance where they used no tape. I’m just looking for someone’s opinion whether or not they agree it was the connection or another fault that could of caused this? Please let me know and I appreciate any answers!


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## Flyingsod (Jul 11, 2013)

Enough layers of super 33 should equal 14kv. I’d lean more towards some kind of contaminate than inappropriate tape type/ technique. Unless the technique didn’t include proper hygiene. Which may well be the case because if they didn’t use the standard tape they very well might not have known about how important cleanliness is. In any case your going to redo ALL the connections right?


Sent from my iPhone using Tapatalk


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## joe-nwt (Mar 28, 2019)

A picture is worth a thousand words. What kind of cable?


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## joe-nwt (Mar 28, 2019)

Flyingsod said:


> Enough layers of super 33 should equal 14kv.


So should the 10-15" of air. But you are likely right that the fault could have been caused by tracking from contamination.


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## Kevhuff26 (Dec 17, 2018)

Thank you for your replies, I understand what you mean about contamination. This fault however did not track to ground. It shot straight to ground from the bottom of the lug at the term point to the 10-15 inches to the box. I’ll get an actual distance measurement soon. I have never seen this before, I also agree it’s hard to say it was the tape job. Do you guys have any insight why the current spiked to over 4,000 amps on that phase before faulting? I will also post pictures soon. Thanks again.


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## Kevhuff26 (Dec 17, 2018)

Also, yes they will be pulling all new cables from the breaker to the motor.


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## micromind (Aug 11, 2007)

A spinning motor will turn into a generator very quickly and will contribute all it can to a fault. This will drive the current much higher than the power system alone.


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## joe-nwt (Mar 28, 2019)

micromind said:


> A spinning motor will turn into a generator very quickly and will contribute all it can to a fault. This will drive the current much higher than the power system alone.



???? Either the breaker is still closed and it is a motor, or the breaker is open and yes, it generates for a few cycles while being braked because it is feeding a dead short. It can't produce more power than the system.


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## em158 (Jul 7, 2016)

I didn't think they still made varnish cambric. Haven't seen it used years. Scotch 77 silicone for filling voids, 130C, then 33. I've made up hundreds of MV motor terminations with no failures.


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## joe-nwt (Mar 28, 2019)

So what kind of cable are you using?


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## gpop (May 14, 2018)

Interesting. 
Like others have said a picture would help or at least be interesting to look at.

For 13.8kv to jump 10" of air it either needs way more volts or it need something to assist it. Molten cooper (copper vapor) from a arc could help bridge the gap. 

Kinda sounds like a loose connection especially as it went downwards. 

I wonder if the rubber tape could melt and cause a drip closing the gap.


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## micromind (Aug 11, 2007)

joe-nwt said:


> ???? Either the breaker is still closed and it is a motor, or the breaker is open and yes, it generates for a few cycles while being braked because it is feeding a dead short. It can't produce more power than the system.


It doesn't produce more power than the system, it simply adds to it. Often quite a bit. 

If the breaker is still closed during the fault and the fault drags the voltage down (among other factors.....), the motor will attempt to convert its rotational energy into electrical energy.


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## Kevhuff26 (Dec 17, 2018)

Can someone please give me some insight on how to post photos via iPhone? Thank you.


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## Southeast Power (Jan 18, 2009)

Kevhuff26 said:


> Can someone please give me some insight on how to post photos via iPhone? Thank you.


You need a certain number of posts to add photos.
It might be possible to post a link or send them to another member.


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## Kevhuff26 (Dec 17, 2018)

Southeast Power said:


> You need a certain number of posts to add photos.
> It might be possible to post a link or send them to another member.


Thank you for the information, I’ll try the link option.


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## Kevhuff26 (Dec 17, 2018)

I’m working on the photos everyone, thank you for your help and patience.


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## glen1971 (Oct 10, 2012)

I'm leaning towards contamination, but I'm no expert on them and without pictures those that have a ton more experience than myself will struggle by guessing too..


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## Kevhuff26 (Dec 17, 2018)

Thanks, I’m trying to get enough posts so I can post pictures.


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## Bird dog (Oct 27, 2015)

Who terminated this? How much trouble would it be to install a bigger box & use a 3M termination kit if available? Do you know some utility people who could give you some info?


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## Kevhuff26 (Dec 17, 2018)

Bird dog said:


> Who terminated this? How much trouble would it be to install a bigger box & use a 3M termination kit if available? Do you know some utility people who could give you some info?


Three to four high voltage electricians were on the termination. The junction box is already fairly large maybe 4x4 feet. What does a 3M Termination kit consist of?


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## Bird dog (Oct 27, 2015)

Kevhuff26 said:


> Three to four high voltage electricians were on the termination. The junction box is already fairly large maybe 4x4 feet. What does a 3M Termination kit consist of?


 You'd have to look it up for your application.
https://www.google.com/search?client=firefox-b-1-d&q=3M+termination+kit+15kv


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## Kevhuff26 (Dec 17, 2018)

I was finally able to attach the photos. To add some details again the arc went towards the top about 10-15 inches from where the lug is to the top of the junction box frame. The connections are bus bar connections via bolts. Please let me know what you guys think. Thank you!


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## Kevhuff26 (Dec 17, 2018)

Also where the bottom of the lug is, that’s where the motor lead was for B phase but it exploded during the arc.


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## Kevhuff26 (Dec 17, 2018)

How the terminations looked before.


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## micromind (Aug 11, 2007)

Were the terminations made with an actual termination kit designed for the specific cable or was it more like 'strip the semi-con back and tape it up'?

Both will work, I'm just curious.

Also, were the sharp edges filed smooth on all energized parts? I'm wondering if corona might have had an effect.


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## gpop (May 14, 2018)

Why is the hardest one to tape always the one that fails first


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## varmit (Apr 19, 2009)

The radius of the upper wire at the termination point, seems a little abrupt. Maybe a lug cracked or an void formed under the tape. I assume that moisture was not an issue? How long has this been in use. I have seen cable absorb moisture if not kept sealed and last for weeks before giving a problem.


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## joe-nwt (Mar 28, 2019)

To me, it looks like the motor lead lug failed.


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## Kevhuff26 (Dec 17, 2018)

micromind said:


> Were the terminations made with an actual termination kit designed for the specific cable or was it more like 'strip the semi-con back and tape it up'?
> 
> Both will work, I'm just curious.
> 
> Also, were the sharp edges filed smooth on all energized parts? I'm wondering if corona might have had an effect.


The terminations were not made with a kit, we believe they used varnish Cambric, 130C rubber and then super 33. We usually use HV tape instead of 130C.

I do not believe there was any sharp edges, but I can’t confirm either.


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## Kevhuff26 (Dec 17, 2018)

joe-nwt said:


> To me, it looks like the motor lead lug failed.


That’s what a few of us thought as well, this particular lead came back shorter than the other two. We had to install a bus bar extension just to be able to terminate the lead.


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## Kevhuff26 (Dec 17, 2018)

varmit said:


> The radius of the upper wire at the termination point, seems a little abrupt. Maybe a lug cracked or an void formed under the tape. I assume that moisture was not an issue? How long has this been in use. I have seen cable absorb moisture if not kept sealed and last for weeks before giving a problem.


We also thought there may of been an issue with the lug, this particular lead came back shorter as well. This motor has probably been in use for about six months before this event occurred. We don’t believe moisture was an issue because we did not see any signs, but you never know.


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