Pics from the Workshop

[efiste2]

A couple of pics from the Plant Workshop today....

The 11KV cable box of a 33/11KV 7.5 MW Transformer blew up this week buckling the box and firing the the cover studs like bullets.....

And in for a refurb is an everyday 11kv 400A Oil Circuit Breaker, the laminated wooden looking things are arc extinguishers/oil turbulators to try and control arcing of the contacts as the switch makes/breaks....Obviousley these bits are immersed in insulating oil

 

[conny]

How come it doesn't have a blow out panel fitted to prevent this?

 

[efiste2]

Older switchgear doesnt have blow out panels as such its all made of 1/4" steel and have to be sealed to keep either G38 insulating "gunk" in, or Compund (tar), this one has actually contained it well, this was off probably a 30-40 year old 33KV transformer as far as i know. More modern switchgear has blow out covers/vents , which blow out in such a way as to direct the blast away from the operator.......

 

[TonyS]

What make is the OCB?

Looks in good nick, what was it in for? Or is that after you’ve done with it.

 

[conny]

Thats what I had in mind. It doesn't look 30-40 years old though.

 

[efiste2]

The OCB is a South Wales Switchgear D4X circuit breaker and is definately more than 30 years old.......This particular one is in to get the porcelain bushes reset into the head of the breaker......Although its can be done in our shop more than likely, we will send it back to manufacturer to do as we have a lot on at the moment. These breakers spend year after year closed in most cases, and without having to trip out a fault, so they dont see much action, apart from an oil change every 10 -12 years it is nowadays. this particular make is one of the youngest "oil" untis on the network....the big project of Scot Power is to get certain types of older switches off the network, as they have operating bans on them and are being replaced by more modern SF6 units.....

 

[ban-all-sheds]

The 11KV cable box of a 33/11KV 7.5 MW Transformer blew up this week buckling the box and firing the the cover studs like bullets.....

What caused that? What does it look like inside?

 

[ricicle]

HV switching has always scared me after seeing 'the video'. I always used to walk far away when our factory subs were being switched !

 

[wingcoax]

There is a power station(small) in Lincolnshire that uses gas from tips to generate. At one point they got in a boiler fired by waste animal products(yes you got it right) after installation a long(very)piece of string was fastened to the switch and after a brisk walk the engineer in charge pulled the string.Result? NO! the string had come off. repeated it did eventually work. When asked the engineer said "I do not like to take chances" This is a true story, i have worked on this site several times and they always use second hand equipment.

 

[TonyS]

You can’t beat a lanyard for closing if you have the slightest doubt or use any form of remote closing. Unfortunately you have to rack the OCB in to the service position first, no escaping being close then.

 

[westie101]

The 11KV cable box of a 33/11KV 7.5 MW Transformer blew up this week buckling the box and firing the the cover studs like bullets.....

We had the 11kV box of a 11/400V transformer do that some years ago, peppered a house with the fixing studs that snapped.

Trouble was it was a nice warm evening and they were having a BBQ, that took some explaining

 

[efiste2]

As TonyS says these older Circuit breakers have to be "racked" up into the live busbar spouts and the live/not live circuit spouts, some take many many turns of a handle to rack up, and your stood in front of it....If there is anything wrong (such as contacts dropped to the tank bottom) and the tank ruptures your in trouble, hence PPE is a MUST!!!. Slowly but surely we are getting oil insulated switches off the system, but it will take many many years. all circuit breakers are spring assisted in the fact the have powerfull springs helping them close/open fast.....and they do close with a hefty clunk!!!
Below are the contacts from one phase of another 11kv breaker.....on the rose contacts you can see the results of some arcing but not that bad .....but the pokers have either been redressed or replaced

 

[westie101]

Or, having racked one in, close it and a buzzing/bubbling sound starts from the OCB.
Turned out that the contacts were so badly eroded that they were only just making contact on one phase!

Water and OCB's don't mix!

 

[janner10]

I know it's a DIY forum, but I wish all posts were as interesting as this one. Great pics and thanks for posting.

 

[westie101]

A rare fault! This cable got shot with a 12 bore. You can see the indents made by the pellets!