New DEC museum entry :D

Roger Holmes roger.holmes at microspot.co.uk
Thu Feb 22 13:26:55 CST 2007


On 22 Feb, 2007, at 18:03, cctalk-request at classiccmp.org wrote:

>
> Message: 14
> Date: Thu, 22 Feb 2007 08:22:15 -0600
> From: Jules Richardson <julesrichardsonuk at yahoo.co.uk>
> Subject: Re: New DEC museum entry :D
> To: General Discussion: On-Topic and Off-Topic Posts
> 	<cctalk at classiccmp.org>
> Message-ID: <45DDA717.80406 at yahoo.co.uk>
> Content-Type: text/plain; charset=ISO-8859-15; format=flowed
>
> Tony Duell wrote:
>> (there are no 'pole pigs' over here)
>
> Is that always true? Sometimes on rural roads with just one or two  
> houses (and
> also individually on farms) I've seen pole-mounted transformers and  
> wondered
> what their function is - I'd assumed they were step-down  
> transformers from
> overhead line voltage (several KV I'd guess) to 240VAC. Or do they  
> do some
> completely different job?
>

I live on a farm, we have a three phase step down transformer on a  
pole in our field.
It steps down from 11,000 volts to 240/440 volts. I guess the 11,000v  
is across
phases as there is no neutral conductor. We used to have a two wire  
supply to the
pole with a 240-0-240 transformer. Then the incoming cloth covered  
wiring from the
pole caught fire. Couldn't do much - it was before it reached any of  
our fuse boxes
or even the meters, even pulling out the 'company' fuses would not  
have isolated
it. We put it out but ran out of powder extinguishers. The fire  
brigade took over
half an hour to arrive (it was in January and it was snowing). They  
went into the
house with breathing apparatus and just saved the house. Everything  
was covered
in congealed PVC, some decorative candles had completely melted and  
they said
another couple of minutes and we would have lost the house. They sat  
on the stairs
for four hours, putting out each new fire in the distribution board  
until the electricity
company turned up and pulled the 1000 Amp fuses on the pole above the  
barbed
wire. The fire brigade were about to leave when my mother pointed out  
some smoke
coming from the wall. The upper storey is timber framed and the  
woodwork behind
the distribution board was alight. They ripped off the Kent peg tiles  
and we finished
the day with a big hole in both inner and outside surfaces of the  
wall. Next day the
electricity company turned up to read the meters, I said hold your  
hand out, and I
dropped a few loose brass wheels which had had numbers painted on  
them into
his hand and pointed out that was all that was left of the meters.

The best guess we could get from anyone was that it was a mis-matched  
load over
the two 'phases' (actually 180 degrees apart), and that the neutral  
wire could not
cope. Later on we got the company apparatus moved into a redundant  
chimney
where it could catch light without doing much damage and I paid 400  
pounds
to have an extra wire put on the overhead supply to the pole and the  
transformer
upgraded to a three phase unit, so I could power my lathe, mill,  
shaper, surface
grinder, pillar drill and my mainframe computer from the mains  
instead of using
a generator.

Roger Holmes.








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