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VLF Dead break terminations

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  1. Kalbi_Rob's Avatar
    Kalbi_Rob is offline Experienced Member
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    Quote Originally Posted by tcoupekyle View Post
    Hey! Yeah that's what we decided to do build another and a stress cone to try it.
    That's exactly what we been looking for. Is that how you normally test these?
    I've always just used the half splice and hadn't had issue until now. But maybe in the past it was all lower voltage. In Maintenance situations.
    We found around 37-42 KV (based on weather) open Pass-Thru Bushings start to arc. That was before we learned (like you are now) that we needed to produce a proper rig to test.
    We contracted a MV splicer to create 3 ft t-body cables and put lug terminals at the other end for our cable connections, since we could easily attach corona suppression balls on the end along with our test cable.

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    Quote Originally Posted by Kalbi_Rob View Post
    We found around 37-42 KV (based on weather) open Pass-Thru Bushings start to arc. That was before we learned (like you are now) that we needed to produce a proper rig to test.
    We contracted a MV splicer to create 3 ft t-body cables and put lug terminals at the other end for our cable connections, since we could easily attach corona suppression balls on the end along with our test cable.
    Exactly.

    In addition, its important to keep the various test rigs that you make clean and in good shape. You dont want to remove a customers new clean silicone coated T-Body and plug in a test jig that has been rolling around the back of your van for a month with dirt and sand stuck in the used silicone. It may pass the your VLF test but certainly wont last as long at it should when you plug the now dirty new T-Body into the transformer or switch after your done.

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  5. tcoupekyle is offline Junior Member Pro Subscriber
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    Quote Originally Posted by Kalbi_Rob View Post
    We found around 37-42 KV (based on weather) open Pass-Thru Bushings start to arc. That was before we learned (like you are now) that we needed to produce a proper rig to test.
    We contracted a MV splicer to create 3 ft t-body cables and put lug terminals at the other end for our cable connections, since we could easily attach corona suppression balls on the end along with our test cable.
    Thanks!

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  7. tcoupekyle is offline Junior Member Pro Subscriber
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    Finished

    We built a test rig similar to what you pictured. And testing went ultimately very well.
    Thank you all so much.

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    Quote Originally Posted by tcoupekyle View Post
    So we brought that issue to engineering that the term is only rated for 21.1kv and at first they said test at 26kv. But then (after testing) they said no they wanted to re-test at 44kv and they couldn't find any literature to back up the test voltage one way or the other. So they decided to re-test at 44kv.

    The cables terminate on an inverter so we can't jump through.
    We are using a dead break connecting cap to input the voltage into the cable. And dead end caps screwed together on the other side.

    We have gotten the cable to test in the last hour. We covered the exposed end of the connecting cap with 130c tape. It's also hotter and drier now this morning was 99 percent humidity.
    It's probably 95% humidity now. So somewhere between the tape on the connecting cap and the humidity drop we have been able to get a complete test on 1 single conductor.

    I am still curious about others opinion on the test voltage though.
    Hey bud, I've been doing acceptance testing at 44kV on solar farms in NC (high humidity) and I've found that I can overcome the arcing at 44kV by cutting the end off of a rubber boot from a sectionalizer and fitting it snugly over a deadbreak connecting plug with stud.

    Attaching a photo...

    This also works in mild rain that has occurred in the middle of testing.

    Click image for larger version. 

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    I wouldn't test those terminations (in your case) at 44kV either. We often see 15kV elbows on 25kV cable. Not sure why it's built that way (the drawings usually call for 15kV cable in those cases), but whatever. We treat it like 15kV.

    I'm curious to know what inverter type has MV cable terminations. Are you sure it wasn't a skid with an integrated MV transformer?

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    Quote Originally Posted by ericnessl View Post
    Hey bud, I've been doing acceptance testing at 44kV on solar farms in NC (high humidity) and I've found that I can overcome the arcing at 44kV by cutting the end off of a rubber boot from a sectionalizer and fitting it snugly over a deadbreak connecting plug with stud.

    Attaching a photo...

    This also works in mild rain that has occurred in the middle of testing.

    Click image for larger version. 

Name:	deadbreakcondom.jpg 
Views:	0 
Size:	395.0 KB 
ID:	535

    I wouldn't test those terminations (in your case) at 44kV either. We often see 15kV elbows on 25kV cable. Not sure why it's built that way (the drawings usually call for 15kV cable in those cases), but whatever. We treat it like 15kV.

    I'm curious to know what inverter type has MV cable terminations. Are you sure it wasn't a skid with an integrated MV transformer?
    Actually think he has 35kV connectors.

    It is common to have 15kV terminations placed on Higher rated (35kV or 25kV) cable, as some customers wish to oversize the cable capabilities for future applications, thus only having to replace the terminations versus the entire cable run. You are correct to treat the cable as 15kV since your terminations are the weakest link, and you cannot exceed the voltage specs for the weakest linked component on the cable.

    But the termination he described are 21.1kV to ground standard 35kV rated 600A dead-break terminations as noted in the below link document below. The termination is rated up to factory test voltage of 50kV or 70kV depending on the BIL rating, thus Acceptance test voltages of 44kV are required per IEEE 400.2. See table 1 of the attached document linked below:

    https://www.eaton.com/content/dam/ea...ca650008en.pdf

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