PT/VT Repair/Removal in Mobile GIS (Gas Insulated Substation) of ABB

[proelect8717]

Dear Respected engineers,

Referring to the attached photographs, we have a mobile GIS (Gas Insulated Substation), made in 1992 by ABB Lodi, Italy. The mobile GIS primary voltages if 132kV at 50Hz.

The problem we are facing is that past few months, is that PT drops its pressure of SF6 gas, since the pressure drops in only PT/VT and does not drops in other compartments (like isolator and breaker), so we suspect we have a leakage at PT/VT Chamber. Now, we think in order to attend the leakage of SF6 from PT, we have two options.

1. Either we shall remove the PT from GIS (as we are using it only for monitoring voltages and not using in protection circuit) and place the end plate at the bottom and close the GIS. Problems in this option: There is very little space between bottom of PT and we don't know how to remove PT by using this little space,

2. Or we shall dismantle the PT from GIS and replace the O rings or attend any more leakage, but for replacing internal O ring (Most probable leakage from there) will require PT to be open to atmosphere. But, as far as I know, PT of GIS should never be allowed to open atmosphere as moisture penetrates into insulation, ultimately leading to failure of PT/VT. Again, little space between PT bottom and floor.

Any one, done this before, please suggest, which option is better and how to do it? Also, if you have any better option, please suggest that also.

 

[proelect8717]

name plate data photo

 

[proelect8717]

close up of pt/vt

 

[proelect8717]

pt/vt nameplate

 

[proelect8717]

pt/vt photo

 

[proelect8717]

space between Pt bottom and floor photo

 

[submonkey]

Hi,

Given that the sub is a mobile unit, have you considered taking
it back to ABB for repair?

Thanks,
Alan

 

[FPelec]

I agree with Submonkey;
I do not know where the substation is located; if the cost of bringing the mobile substation to Lodi is too high, probably it could also be possible to repair the VT by changing the o-ring on site, but being it quite a critical task, it should be performed by the manufacturer.

Si duri puer ingeni videtur,
preconem facias vel architectum.

 

[ScottyUK]

You will need an indoor facility with fairly clean conditions, or at least reasonably dust-free. The outdoor environment in the photo looks fairly dusty, certainly not the kind of place to open GIS without protection. As a minimum you need to understand how the equipment is designed to come apart (or how it was put together) and that's not always apparent from simple inspection. Do you have detail drawings / shop drawings?

England's National Grid Company injected wax into the inter-seal space between the inner and outer O-rings in an attempt to avoid dismantling large runs of SF[sub]6[/sub] IPB after the inner ring failed. I'm not sure if that was their own undertaking or whether it was supported by either ABB Hosag at Baden or ABB Westboro in the US. Baden is still ABB, Westboro is now AZZ CGIT Westboro. Maybe worth considering.

 

[proelect8717]

Dear submonkey and FPelec,

Thanks for advice, for the first time we also thought same, but due to some economical reasons and other management problems, we are provided the task to attempt it in house. So, kindly guide how to do it.

Dear Scotty UK,

Thanks for comments. Yes, we shall create a tent around the mobile GIS and then do the work. But please guide how to do it??

Don't have any drawings or manuals. got it from some other department. so, nothing came except its control wiring drawing.

Kindly help and guide how to attempt it. Its ELK 04 model.

 

[davidbeach]

I think you've gotten your answer, even if it's not what you what to hear. It's not going to be a do it yourself job with a successful outcome. And learning that you weren't successful could be quite exciting; if you're still around to tell the tale. If you can't/won't work with ABB, at least find someone else who's done that kind of work before.

 

[ScottyUK]

I have sufficient experience of the ELK series to know it easy would be to go down the wrong path when trying to dismantle it. Part of ours was stripped down by ABB's engineers, and it certainly didn't come apart the way we thought it did. We had the shop drawings for most of it and still guessed wrong.

Get factory help, it's going to be a lot cheaper than trying to put it right after you make a mistake.

And 'tent' is almost certainly the wrong idea. Get it indoors into a clean workshop, and seal the building up as much as you can before you crack the seals.

 

[scottf]

I work for Ritz (manufacturer of the VT) and I'm somewhat familiar with that design. Best advice is to not attempt a repair yourself, but to get with ABB or GE Grid Solutions (current owner of the old Ritz high voltage operation AREVA -> Alstom -> GE).

 

[DTR2011]

As a former ABB German and Swiss certified GIS field engineer, I have to echo the suggestions of others. I have performed repairs / modifications in the field, however all efforts to make a "clean room" were made prior to any work performed. Additionally, I would completely wash the exterior and blow dry. You will also need an SF6 cart, commonly available from DILO, with the appropriate fittings.

Hire a certified expert and have your crew support him. The GIS expert will have all of the necessary tools and gas handling equipment. It's more than you think.