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#124201 - 09/02/06 09:39 PM Overload  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,223
SI,New Zealand
All pictures and information supplied by RODALCO:

Quote
500 kVA, 11 kV / 230 / 400 Volts Transformer at Orbit road Albany TB 2163
Jumpers were 120 mm² Copper

I had to adjust a streetlight timeclock.
When I opened the door I smelled burning and hot plastics.
I took the photo's and closed the door, did not want to disturb anything in case a phase to phase flashover occurred.
Arranged an emergency shutdown to upgrade the jumpers.
New 240 mm² jumpers were put in that evening.
Next day I took a load check and measurements were as listed.

Load on Red phase 600 Amps
Yellow Phase 470 Amps
Blue Phase 440 Amps
Still within the 500 kVA rating which is 696 Amps per phase.

Currently there are another 2 big buildings nearing completion. the transformer will be upgraded to 750 or 1000 kVA.

Regards

Raymond


The pics:

[Linked Image]


[Linked Image]


[Linked Image]


Thank you Ray!. [Linked Image]


Tools for Electricians:

#124202 - 09/03/06 12:16 AM Re: Overload  
mxslick  Offline
Member
Joined: Oct 2004
Posts: 803
Atomic City, ID USA
From the second pic, looks like some sort of fault has already happened in there, notice the blackening of the can to the right of the streetlight block?

Are those factory installed jumpers? If so they should have been adequate for the full rated load. [Linked Image]

But I also see this stirring up the debate on bundling!! [Linked Image]

I would have been wary of disturbing anything too. [Linked Image]


Stupid should be painful.

#124203 - 09/03/06 12:48 AM Re: Overload  
RODALCO  Offline
Member
Joined: Dec 2005
Posts: 854
Titirangi, Akld, New Zealand
No not as far as i'm aware off mxslick.

These cables are NOT factory installed.

These DIN racks are assembled and put in on site by whoever gets the quote for the transformer install.

These cables were obviously under rated and should have been upgraded when other DIN fuses were loaded to accomodate new circuits.

In stead of doing it correctly the first time, Jumpers should be adequate for the maximum continuous load + 20 % from the transformer.
In this case cables rated at 800 Ampères should have been fitted. Better to feed the busbars from two sides as well.

Note the red colour sleeve by the bushing which has split from heat transfer from the copper conductor.

Bundling too, cables close together can't dissipate heat as effective. Better to use insulated spacers in between them.


The product of rotation, excitation and flux produces electricty.

#124204 - 09/03/06 01:00 AM Re: Overload  
Luketrician  Offline
Member
Joined: Jul 2006
Posts: 272
Sale Creek, TN USA
Looks like the ampere readings you took are obviously accurate, one look at those jumpers and you can see that the red phase is definitely the high leg. Way to go on diffusing that ticking timebomb Raymond.


Luke Clarke
Electrical Planner for TVA.


#124205 - 09/03/06 01:36 AM Re: Overload  
stamcon  Offline
Member
Joined: Mar 2001
Posts: 329
So San Francisco CA
What's that small wire that appears to be loosely attached to the black bus(position #4)?

steve


#124206 - 09/03/06 03:53 AM Re: Overload  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,223
SI,New Zealand
Steve,
Quote
What's that small wire that appears to be loosely attached to the black bus(position #4)

That would be a temporary neutral. [Linked Image]


#124207 - 09/03/06 07:55 AM Re: Overload  
RODALCO  Offline
Member
Joined: Dec 2005
Posts: 854
Titirangi, Akld, New Zealand
A temporary Neutral stamcon

That one and the red phase one with the airborne HRC fuse are driving the (temporary) timeclock,
which drives a streetlight contactor below the five 16 amps HRC fuses.


The product of rotation, excitation and flux produces electricty.

#124208 - 09/04/06 04:47 PM Re: Overload  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,223
SI,New Zealand
Our Neutrals are Black here in NZ.
Good skills though Ray, leave the thing to cool down before doing anything with it.
I see the heat-shrink cover has split, it takes a bit to do that.
One of your own time clocks?.
I note the RF label on the clock panel.
One thing I have noticed since leaving the PoCo here in Ashburton, is that sometimes on Monday nights, the Street-lights are out.
Not one block, but most of the town.
Un-real!.


#124209 - 09/05/06 01:46 AM Re: Overload  
RODALCO  Offline
Member
Joined: Dec 2005
Posts: 854
Titirangi, Akld, New Zealand
Well spotted Mike,
I use RF 9xx asset numbers on the clocks and an XL spread sheet to keep track of my clocks, platform numbers, address etc.
That is one of the newer ones. Late 1988 Maxirex BQT from Germany.

A lot of clocks I use are 40 + years old with full clock work motor driven mechanisms. (Landis&Gyr, AEG, Sangamo).

Mike, the POCO obviously needs you back and is lacking qualified staff to deal with the streetlights matter.

edited for typo's RF.

[This message has been edited by RODALCO (edited 09-05-2006).]


The product of rotation, excitation and flux produces electricty.

#124210 - 09/21/06 09:14 PM Re: Overload  
electrictim510  Offline
Member
Joined: Sep 2006
Posts: 23
Richmond, CA, 94804
I know this is minor compared to the problem at hand but i dont like the zipties, too tight. Just makes the heating worse.


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