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#141738 10/16/04 01:45 PM
Joined: Jul 2002
Posts: 8,407
Likes: 2
Trumpy Offline OP
Member
Here's a couple of pics of a Pole-top Transformer that I had to work on last week.

[Linked Image]


[Linked Image]

This is a 50kVA 22kV Primary - 400/230 Delta/Star type.
It's an end of line transformer or Spur Line transformer, as we call them, the HV fuses being at the supplying end of the Spur, about 200 metres away.
In the first pic, just in behind the tranny itself, is the LV connections and the Neutral(Star) point.
The transformer has it's Neutral Earthed at this terminal(along with the Service Line Neutral), via a heavy (16mm) wire running down to a whopping great Earth spike in the ground that is driven with a stake driver.
[Linked Image]

Mike :]

Joined: Jul 2004
Posts: 200
U
Member
Quote
Neutral Earthed at this terminal(along with the Service Line Neutral), via a heavy (16mm) wire running down to a whopping great Earth spike

Do you mean 16mm?

That is now the minimum csa for the of the main earthing ep conductor in PME systems over here, where in a 100A setup the csa of the tails does not exceed 35mm. The min csa for main bonding conductor is 10mm. Pole earthing is done using 50mm into spike arrays; as many as required to bring the reading into line.

16mm seems a bit on the lean side...


If hindsight were foresight, we'd all be millionaires!
Joined: May 2002
Posts: 381
H
Member
I may have got it totally wrong here but when I read Mike's post I took the dimension given as a diameter rather than a cross sectional area - thus giving it a csa of 201mm2.

Joined: Jul 2002
Posts: 8,407
Likes: 2
Trumpy Offline OP
Member
Oops,
Sorry guys, I missed the 2 from the end of the end of the 16mm part. [Linked Image]
This is the csa of the wire, not the diameter.
The reason for the work on this pole was to correct a problem that you can see in the centre-bottom of the first pic, where the Service Line Cable (16mm2 3 Core + Neutral Screen) runs up the pole, but some idiot had installed an anti- rodent band over the cable, which had started to eat into the cable, but don't ask me how.
So it's now sporting a pretty orange 50mm conduit run up the side of the pole. [Linked Image]
I had intended to get a couple of close up shots of the transformer and an "after" shot, but I ran out of time and besides, the people were looking at me taking pictures of the pole when I first got there, through their kitchen window.
At least it was a nice day!. [Linked Image]

Joined: Apr 2002
Posts: 2,527
B
Moderator
Mike, it’s nice to see that 3ø service is available outside of a developed area. Can you say what the typical number of homes/farms{/dairies/irrigation pumps} would be for a rural 50kVA transformer?

Joined: Jul 2002
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Likes: 2
Trumpy Offline OP
Member
Bjarney,
According to the LineCAD software in my Faults truck, as of the last update, there were 327 50kVA transformers in use within our PoCo district. [Linked Image]
There is also a total of 1554 transformers of one sort or another in this area.
One thing you have to remember about this area, it's mainly Rural and with the advent of huge dairy farms, lifestyle blocks and the like, our Network here has had to be seriously upgraded here over the last couple of years.
11kV is on the way out over here, at least in this part of the country, with 22kV upgrades happening as a matter of course.
It wasn't that long ago when 33kV was our highest Network voltage here, now it's 66kV.

Joined: Aug 2001
Posts: 7,520
P
Member
Hey Trumpy,

Could you parcel up some of that lovely blue sky and send it to England? [Linked Image]

Quote
11kV is on the way out over here, at least in this part of the country, with 22kV upgrades happening as a matter of course.
Over here 11kV is the major part of the local distribution network. Feeders into the area are at 33kV, then down to 11kV for all of us out in the sticks.

According to the PoCo there is still a small quantity of 6.6kV local distribution somewhere in the East Anglia region, although I would think it's getting pretty rare now.

Quote
It wasn't that long ago when 33kV was our highest Network voltage here, now it's 66kV.
But you have higher for long-distance transmission, don't you?



[This message has been edited by pauluk (edited 10-18-2004).]

Joined: Jul 2002
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Trumpy Offline OP
Member
Paul,
Quote
But you have higher for long-distance transmission, don't you?
Yes,
We use 110kV and 220kV as our transmission voltages here.
As well as a 500kV DC inter-island link to the North Island.
However, these Transmission voltages could be changed in the future, if and when our Transmission system gets a well overdue upgrade.
There has been talk of the 110kV system being dropped all together and a new 400kV system being installed across most of the South Island. [Linked Image]

Joined: Feb 2003
Posts: 939
F
Member
mike:

I dont know why but what if it make it more easier to put the fuse right next to the transformer to make it more safer then try to go back 200 meter to pop it off ??

in north america system on the end of run lines or spurs we do put fuse on the transformer also for safety reason becase some area the other place for fuse disconnection device can be far as 1 or 2 KM away from the transformer source [Linked Image]

most of time we like to keep it close as we can

merci , marc


Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)

Joined: Jul 2002
Posts: 8,407
Likes: 2
Trumpy Offline OP
Member
Gidday there Marc,
Quote
I dont know why but what if it make it more easier to put the fuse right next to the transformer to make it more safer then try to go back 200 meter to pop it off ??
That's a really good point, for some reason, all of the spur lines we have here are fused in this way, as in the fuses are always at the start of the line.
Mind you, any Faultsman that's attended a Pole-top transformer fire(they do go on fire!) to shut it down for the Fire Brigade, would thank thier lucky stars, that the fusing was well away from the transformer. [Linked Image]


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