Transformers around the area

[RF Lighting]

I know a plasterer who put his hand axe through an LV supply cable as it was in his way

There wasn't much of the axe left, so I'd imagine a HV cable would go well.

I have heard of someone catching HV cable filled with high pressure oil, and it making a real mess, but I'm not sure if they were winding me up, or if they even exist

 

[ColJack]

never heard of HV cables filled with oil.. but then again I'm not an HV linesman..
I know that the transformers are usually oil filled and would be under pressure when warm ( so most of the time )..
maybe they caught the HV cable going into the transformer and pulled it out, with the oil spraying out of the hole?

 

[londonboy]

Very big hv stuff uses a non flammable oil to cool the cable down, with pump stations along the length of the cable to push the oil through.

 

[IJWS15]

One of our contractors recently hit 2 33kv cables with a thrust bore machine, lucky for them only minor damage to the cable which only became apparent when the supply company saw the pressure drop on the cable. Now why were they thrust boring ? ? ? ?

Repair bill expected to be around £250k.

Underground HV cables are generally oil cooled.

 

[stuartsjg]

Was on the scotish power HV saftey and switching training course last week at Cumbernauld and the 11kV stuff was all quite tamper resistant.

All switches and things were padlocked which intelocked with covers etc. Would be easy enough for somebody to cut into thing tho.

All the 11kV stuff there were no re-closers. If the breaker tripped it would need to be reset.

Best way i can see to kill an 11kV supply is to switch off the switch and close the earth switch - there will be allot of buzzing for a short time until the protection trips but once thats happened you should be ok....

Apparently the biggest problem with thoes is kids breaking the sight glass and poking bits into them!

Higher voltage SS's tend to have the copper earth lines which ground the low side of the insulators is a common target for theifs as they are not normally live unless the insulator is wet so conducting a bit to ground.

 

[efiste2]

Older 132KV undeground cables are oil cooled as Londonboy says. and again as Stuartsjg mentions, In the SP network some switchgear (not inc Transformers) has an interlock on all acces covers, That will only allow the covers to be opened when the switch is closed to earth. Howver on withdrawable circuit breakers, access to the fixed contacts is only screened by a tinplate shutter that can be opened easily unless SAFETY LOCKED , this is usually in INDOOR subs. But these days its all to common to see an indoor sub getting broken into. On Multipanel switchboards access to live busbar chambers is only a matter of undoing a few bolts and you have access to the live busbars which in some cases are not even shrouded at the joints!!!! Basically substation security is down to the lock on the sub door. or the condition of the fence. There are rules that must be obeyed though, such as type of fencing, anti-climb stuff, and adequate warning signs. Its been known for the b#stards that get electrocuted or burnt alive to claim of the Supply company, because the danger sign wasnt clearly visible, Never mind the 33kv transformer humming away, etc etc

 

[aptsys]

Got any more/larger pictures efiste2?

 

[ban-all-sheds]

Another question which might make uncomfortable consideration would be how many major substations on the outskirts of London (or other large cities) would you have to take out to leave the city with no power at all for a very long period of time, and how well are those locations protected against attack by well trained, well equipped and utterly determined groups?

 

[efiste2]

some pics of a couple of 11kv secondary s/s that have had their switchgear replaced as part of a project to remove aged ring main units from the system that have been found to be at risk of a failure.
This is a very common LV distribution board fitted with 315A HRC fuses

A Circa 1955 HV unit protection panel used in more urban areas called SOLKOR

Two modern 11kv Ring Main Units

The Ring Main Unit below is the one that is being hurried off the system due to some failures of the switch mechs.

 

[bernardgreen]

Untitled

• bernardgreen
• 9 Jul 2009
• 1

Why does the sign say --- Keep Off --

If is is kept off then what is the point of installing it.

 

[RF Lighting]

I think that is meaning do not touch, rather than do not switch on...

 

[aptsys]

Great pictures efiste2. Thanks

 

[Wooshzz99]

Great photos any more??

 

[efiste2]

heres a pic of an old mechanical overcurrent and earth fault relay that is used to protect HV transformer windings,

this is another type of 11kv oil filled Ring Main Unit with a wihdrawable circuit breaker.

below is what Scot Power term a modern 500kva Secondary sub note NO oil filled switchgear, and the full enclosed and insulated LV distribution board.....