Vacuum Bottle integrity test 1

[a10jp]

Is the vacuum bottle test tytpically done as a factory test, or field acceptance test? One of the specification requirement mentions the field tests (including the vacuum bottle test) be done in accordance to manufacturer recommendation. But this particular mfr stated that factory test were conducted but recommends that the field test be waived becasue it is not a standard field testing procedure for the company, and therefore the vacuum bottle test kit is never shipped to the site. Is this acceptable? I like to hear opinions from others.

 

[davidbeach]

Certainly not acceptable. How are you going to find shipping damage if you don't perform the tests on site? I would never allow the tests to be conducted until the breakers were in the room with the switchgear.

 

[a10jp]

Hi, thanks for your response. At first I was not sure if the vacuum bottle integrity test is a factory test or field acceptance test, reading from the descrptive of the test. Thanks for verifying this.

 

[dpmac]

I personally would not feel comfortable energizing the breaker without checking the vacuum bottle and primary insulation integrity.

 

[a10jp]

Now reading the spec again, I realised the importance of this test, along other IR tests, accoridng to the reports, were fully conducted. Unfortunately I am only reviewing the test submittals after the fact, this will be an QA issue I'd discuss with the group.

 

[a10jp]

Another thing I want to mention is that it nothers me why this test would be left to manufacturer's recommendation, especially if the manufacturer elects to opt it out. Obviously I would have to review the manufacturer's brochure. Should this test be a NETA acceptance test procedure? I wonder.

 

[Zogzog]

Yes, vacuum bottle is a required NETA acceptance test on VCB's. When you call someone to get that transformer tested, do the VCB;s too. Be sure to follow precautions for exposure to X-Ray radiation when conducting these tests.

 

[LionelHutz]

They should be checked periodically while on site so not only should they be checked as received but also as part of your PM program.

 

[Gianoli]

The company I work for has stopped all regular PM testing of vacuum interrupters years ago. We have thousands in service and the simple facts are that the number of failures we saw (basically zero) simply did not support continued testing. We still do some other tests but not vacuum bottle integrity. Several manufacturers state testing is not required on a regular basis.

NETA recommends doing it “IF APPLICABLE “, whatever that means, and in “STRICT ACCORDANCE WITH THE MANUFACTUER’S PUBLISHED DATA”. DC testing of vacuum bottle integrity is useless. Manufactures only recommend AC testing and you need a test set that will ignore transient breakdowns which can occur.

So, for those of you who do the vacuum interrupter integrity test I would like to know how you test them? What type of test equipment do you use? Do you check the contact gap prior to testing? Not real easy to do in a lot of breakers. If the bottle insulation breaks down during testing is the interrupter bad?

 

[Zogzog]

"NETA recommends doing it "IF APPLICABLE ", whatever that means"

You are not looking at the same NETA standard that I am, what rev are you looking at?

"So, for those of you who do the vacuum interrupter integrity test I would like to know how you test them?"

AS directed by the manufactures literature

"What type of test equipment do you use? "

AC hipot

"Do you check the contact gap prior to testing? Not real easy to do in a lot of breakers." Yes, and yes it is if you are familiar with all types

"If the bottle insulation breaks down during testing is the interrupter bad?"

Yes, thats the point.

 

[dpmac]

Gianoli:

Some very good points. Most Mfg require AC tests on interrupters and primary circuit. All AC Hipots are not created equal (no matter what they tell you.) Many test techs use a single output AC test to apply the voltage. These testers are typically rated about 2KVA or less, have an oil filled fiberglass or epoxy "bonnet" style tank. After a few months of use the cables get abused or are replaced with longer cables so they don't have to be so close to the test specimen. Some times they are replaced with a shielded cable for ease of use. Depending on the test set, it may not have enough capacity to energize the home made output cable let alone test the bottle. So the bottle is deemed "Failed" only because the test set "tripped" off.

The breaker mfg don't make it easy either. I believe GE Powervac (15kV, metal-clad VCB in US)insteructs you to use AC only, then DC is ok, kind of, but warns you NOT to over voltage the primary circuit insulators and only apply 27kVAC to the primary circuit. Two paragraphs later they require the vacuum bottle integrity test be performed at 36kVAC. If one does not own a center point grounded AC test set this test is impossible without applying 36kV RMS to the primary insulators. Doing so will trip off most, if not all single output AC test sets on a humid day.

I have tested 6-8 "Failed" 15kV interrupters after the they were replaced by well meaning techs. The mfg are VERY proud of their replacement vacuum bottles and will charge you accordingly. Because we are the curious type, we have found they pass all factory tests and meet all specs.

Back to the original question: Does your company perform (or require the installer to perform) vacuum bottle integrity tests on NEW equipment prior to installation?

In response to your questions, we use Hipotronics 7BT60A center point ground AC test sets for doing both bottle integrity and primary circuit integrity tests. Regarding contact gap and wipe, we do the best we can to check correctly. Most of our customers are non utility and TOTAL breaker operations per year may run as high as 10, wear has yet to be an issue.

 

[Gianoli]

Zogzog,


"NETA recommends doing it "IF APPLICABLE ", whatever that means"

You are not looking at the same NETA standard that I am what rev are you looking at?

**I have the 2005 edition of the Maintenance Testing Specifications Guide. I can’t quote the exact section because I don’t have it here at home.**



"So, for those of you who do the vacuum interrupter integrity test I would like to know how you test them?"

AS directed by the manufactures literature

** And what is one to do if the manufacturer does not recommend testing on a regular basis or has no specific procedure?**

"What type of test equipment do you use? "

AC hipot

** That’s good provided one is aware of issues surrounding AC hipot testing of vacuum interrupters some of which dpmac mentions.**

"Do you check the contact gap prior to testing? Not real easy to do in a lot of breakers." Yes, and yes it is if you are familiar with all types

** You may well be more experienced than we were when I look after the department in my company. There were many breakers (34.5 kV Toshiba comes to mind) that we had a hard time determining the contact gap prior to testing**

"If the bottle insulation breaks down during testing is the interrupter bad?"

Yes, thats the point.

** Not according to some manufacturers. I was told on more than one occasion that even if the interrupter failed the AC hipot test the results were not considered definitive and the interrupter should be returned to the manufacturer for further evaluation.

Dpmac,

“Does your company perform (or require the installer to perform) vacuum bottle integrity tests on NEW equipment prior to installation? “

**Not any more. We do several other tests but not a vacuum bottle integrity test**

The bottom line for us was this. We had been testing thousands of these things ever year. To find what? That one out of 10,000 tested bad and then the manufacturer tells us that the tests we were doing is not considered definitive and we should return it to them for further evaluation.

As I said before the rate of failure on these things is so ridiculously low we simply cannot justify testing on a regular basis. Statistical analysis simply does not support regular testing of vacuum interrupters. Spend your maintenance budget money some were else.

 

[oldfieldguy]

Gianoli--

I take Zog's side in this discussion. I was a field service engineer for years down here on the US Gulf Coast. Every one of my clients who used vacuum circuit breakers and contactors wanted them tested.

While I agree with you that the number of failures is small, the application of a high voltage circuit breaker is usually such that failure is very costly in repair costs and loss of production. I have found failed and failing (gasing) vaccum bottles. I have also cleaned up the mess when a vacuum bottle failed.

Even where the manufacturer states that failure of the hipot test does not mean vacuum bottle failure, they still don't recommend putting the breaker back in service. I would think that it would be a very strident conversation if I put a breaker back in service and had it fail catastrophically while I had a test report with a failed vacuum test.

Why would they tell you to send the bottle in for "evaluation"?

I'd hate to cut this testing out of my PM program. As the (former) manager of a field testing service, I can tell you that taking vacuum bottle testing out of your PM program isn't going to be a really significant cost savings, since you still need to do contact resistance, timing, trip testing, mechanical checks, etc. on the breakers anyway.

old field guy

 

[dpmac]

A blown bottle and resulting damage to equipment may mean different things to different people. Gianoli may work for an entity where it makes sense in his environment and situation. After all, its always about the money isn't it?.

If it was an (insert expensive Hi Tech Company name here) that would lose gazillions of dollars a day or a plant where lives were at stake should the plant be plunged into darkness should a bottle fail (No bodily injury will be discussed here) this would be a moot conversation for many reasons.

But no matter the above, I believe certain NEW equipment should be completely tested because $hit really does happen. It happens at the suppliers, the factory and in the field. There is a huge difference in my little world between a 15kV, 1000MVA VCB and a 600V MCCB. A difference in potential injury and damage and of course money.

I understand Gianolis position, I even agree with it. I guess I am just not happy about it.

 

[Gianoli]

Perhaps I need to clarify my position somewhat. The failure rate on these things is not low it's almost none existent.

Do we have breakers/contactors/reclosers blow up? All the time. Probably a couple a month. Some have rodents enter the enclosure. Some get wet and blow up. Some get dirty then wet then blow up. The last one had tin foil insulation glued on the inside walls of the enclosure to keep it warm inside in the winter. The glue dried up and the tin foil insulation fell into the energized bus.It blew up. The cells gone. When you have thousands of breakers/contactors/reclosers stuff happens all the time.

Now, how many have blown up because a vacuum bottle failed. Seen a few I guess, hard to tell for sure most of the time. Now, of the few I have seen blown up because maybe a vacuum bottle failed how many would have been identified by testing them as part of a PM program? How many of the ones that blew up had a slow vacuum leak that would have been captured in a PM program? I tend to think that the ones that had a vacuum leak probably failed quickly. Once the vacuums gone so is the breaker the next time it opens. So what exactly are we looking for doing a vacuum interrupter integrity test? A vacuum interrupter that has a slow leak and we happen to catch it before it fails by doing a yearly PM? A yearly PM that requires special equipment and that the analysis of the
results in anything but straight forward.

Sorry, I am not buying it. If you guys think your doing these vacuum interrupter integrity tests and catching bad bottles before they blow up all the power to you. Keep doing it. In my humble opinion you are hunting for a needle in a haystack.

Thanks.

 

[a10jp]

I am meeting with installation team tomorrow to ask them these very questions, why does the manufacturer opt this test out, and why hte test bottle was not shipped with the breaker to allow a field test. And if there is any cost saving that is intended, I will find out how much we talking about.

 

[Zogzog]

dpmc,

Great point about not all AC hipots being created equal, very true.

Ofg,

You hit the nail on the head, would I schedule a shut down only to to VB integrity tests? No, however, you still have other testing to do on VBC's and the few minutes extra it takes to test the bottles really dosent add any costs to the testing.

I havent failed a lot of bottles, but I have found a few bad ones over the years, enough to justify this test, and the NETA standards review council has reviewed the failure data and considers this test worthwhile, then so do I.