How Old?

Until there is a forced outage of the plant continue to follow the embargo, otherwise follow the maxim, "If it ain't broke don't fix it!". You should use your time to plan the complete replacement of the entire board, reusing any switching/protective equipment 80+ years old is ill-advised because too much may have changed in the grid supplying it, especially the available short circuit current, which has been steadily increasing as the network in the area has grown more dense. You really can't be sure that those OCBs will operate safely/properly/reliably/fast enough under modern fault conditions.

Non of the existing protection will be used, modern MCCB's will take care of that.
Unfortunately one part doesn't work, nothing too important, it's only the O/C trip on OCB K4! That will take 5 minutes to repair during a planed shut down.

Due to the requirement of the insurance companies dependant manual OCB's are no longer acceptable, they can explode as the operation is slow for making load and possible faults. I've been switching OCB's for the last 45 years and I'm still alive (I think).
The problem now is a lack of people with experience of this type of switchgear. I'm supposed to be retired, a job like this comes along and I'm kicked back in to life.

I hope that during switching you will be wearing high cal ppe, rated gloves and flash mask.

We sometimes lend out "bomb suits" for operating old private 11kV switchgear qttached to our network. Just have to find certified operators and somebody to develop the switching instructions.

One of the reasons I've been involved with the job is I'm authorised up to 11KV. I've yet to get access to the MV switchgear to make a decision on switching procedures. If like the LV gear there is a live switching embargo I'll get the PoCo to isolate and earth the 11KV supply before any switching operation is carried out. (Yet more expense!)

The owners of the factory know something has to be done but don't want to part with the cash. "It still works, what's wrong with it?"

Well, if plausible, I would build a new switchgear room with all new equipment and lines going back to a close location that could be completely built for a quick changeover of incoming and outgoing lines....then wait for a good time if possible, for a shutdown....

Replacement would be my first choice if it wasn't for the number of PILC cables involved. Each would have to be spliced or replaced, a time consuming and expensive job.

If I get the go ahead for plug in units with MCCB's the downtime will be about a day including testing. The metering would be retained.
Given the time constraints I can't think of another mode of attack but I'm open to suggestions.

The picture only shows ½ of the board, there's two more 1600A and six 200/400A OCB's on the other side of the wall

I sympathize with you, there is no easy way to go...and I might add you are not alone in facing this type of a decision...It can be a bit like stepping in bubblegum on a hot day, it can become a very untenable situation...I think I would take the same approach as you and hope for the best....

This is another approach. Remove the plug in connections and bolt the MCCB direct to the back section.

I'll get my bid in, it would be a good addition to my collection of vintage switchgear handbooks. I can't say I was expecting to have to use one

I'm waiting for a 1950's Ellison 30A OCB to be delivered, once cleaned up it will be mounted on the lounge wall. The G/F isn't too happy with the idea, I can't understand why?

I am not electrical but I have had to decommission a lot of this sort of plant.

Other that the obvious electrical danger I would be concerned about PCB (Poly Chlorinated Bi-phenols) in the breakers and asbestos in the cables, gaskets, mounting boards and any where else that somebody thought a little heat resistance wouldn't go astray.

Best of luck with the outage and switch over.

BAB.

The firm George Ellison Ltd is still in business:
http://www.ellison.co.uk
Its founder was also the inventor of Tufnol:
http://ahistoryoftufnol.org/companyhistory/index.html

They were the first people I contacted. Their only suggestion was "rip it out". they then tried to sell their new switchgear.

I've switched that type of Metro Vic OCB's many years ago. I can't say I was happy with them back then, 30+ years on and they won't have improved.

I can't help with a technical answer because i have no useful experience of old switchgear. But I do recall once back in the early 50's (an apprentice) I was given the job of re-filling some overload timer dash-pots with oil (different grades of oil and different depths - to give desired time delay control). "...it's in the bottle on the shelf...". It turned out to be Teepol - and not oil! and it worked.

Someone else went back and changed it to the correct oil - but it only came to light because they asked where the detergent had gone.

But to help with the logic of your problem, I ask what is the 'driving' force behind finding a solution. Is it a choice that allows you to take action with a plan in line with time and cash-flow.

Or is there some external force-majeure - when suddenly you will be landed with an instant and costly update or repair imposed by others outside your control.

My approach is to cost out the most effective and desirable solution available to you - then do it at your own pace.

Alternatively, do nothing, and limp along 'fire-fighting' hoping the fateful day will never come!

If the company decide to do nothing then it's no longer my problem. I can get it working as original but it still won't meet current legislation.

" If the company decide to do nothing then it's no longer my problem. I can get it working as original but it still won't meet current legislation."

I think it might be your 'responsibility' so to speak - if doing nothing was based on your 'repair' getting a few more miles out of the old switchgear.

I am not au fait with the finer points of your legislation, but it seems a general principle here (UK) that regulations tend not to be retrospective - ie, hardly any of my 'old' electrical systems (home or factory) comply with today's regulations - but no action is required to upgrade anything.

That is, until additions and modifications are needed and then the new regs kick in.

If your old switchgear must comply with new regs when you service it, and the mods/repairs do not achieve this, it looks as though you must replace it with something that does.

And if you did 'fix' it, are you, as a professional engineer, 'allowed' to carry out work that does not result in compliance with the regs?

Under BS7430 general maintenance won't affect liability unless incompetence could be proved.

Modification would be a different matter. The board would have to meet modern standards for fault clearance time and withstand.

Existing circuits will be tested but we have no obligation to repair/replace. We will issue recommendations for any remedial work. Again it would be up to the client if they act on our recommendations or not.

If we were to test under BS7671 some circuits would fail, BS7430 uses calculated and not "one size fits all" values.
For a 400A 433V feeder:
BS 7671 1MΩ minimum
BS 7430 29KΩ minimum
I've put 50 year old PILC feeders back in to service at less than the calculated value, it was a calculated risk. After a year on load the IR readings were >10MΩ

But it will be the insurance company calling the shots in this case.