Transformer replacement

[jim dungar]

In my area, most of the utility transformers are either padmount construction or have top mounted bushings for use in open air. Most of our industrial transformers are arranged with side mount connections for close coupling to switchgear.

Moisture absorption by an un-powered transformer is almost entirely dependent upon the type of the transformer insulation, and if the relative humidity condenses.
I had one customer that kept his dry type transformers under a tarp with an energized 100 watt light bulb to keep it above ambient.

 

[zog]

I had one customer that kept his dry type transformers under a tarp with an energized 100 watt light bulb to keep it above ambient.

I have been recommending that for years

 

[petersonra]

Surely you must be joking Volta & Kwired. Because What I said is an industrial practice to avoid condensation in the transformer.

Can't say i have ever seen that, but most transformers I have seen are oil filled or encapsulated.

 

[petersonra]

In T.M.Tagare's well known book 'Reactive Power Management' published by Tata Mc Graw Hill,the statement that it is an industrial practice to keep standby transformer energized is present.



In India,the power companies are sometimes willing to replace the faulty transformer of the consumer quickly with their own on a chargeable basis.Is such a practice not available in US?

"Quickly" is not something the POCO is very good at many times. Spare parts like big transformers are readily available but may be 500 miles away.

 

[petersonra]

I wasn't taking a stand on it. I was simply telling you what I have seen on the many different industrial sites (including Water and Petrochem) that I've visited.

Your two inks are diametrically opposed. Sydney Water wants the standby transformer and cables to remain energised where practicable.
From the PCRA we have "Stand by transformers should be de-energized to conserve energy wherever possible except for monsoon period to avoid the possibility of moisture contamination."

Two different spellings of "energised" - two different versions of English.

Monsoons are not real common in the US. It may explain at least in part why such things are done in India and not typically done here.

I have run across a very few installations where the utility has provided a redundant feed and a redundant transformer. More often, just a redundant feed.

 

[brian john]

Monsoons are not real common in the US. It may explain at least in part why such things are done in India and not typically done here.

I have run across a very few installations where the utility has provided a redundant feed and a redundant transformer. More often, just a redundant feed.

For a more that redundant price.

 

[kwired]

Well, I guess you either shouldn't believe everything you read, or look should closely at the difference between 'standby' and 'spare'.

I agree with the idea that there is a difference between a standby unit and a spare. I also think it would be better design to have the spare heated from some other source if it is necessary to prevent condensation, otherwise what good is the standby if it is damaged by the same surge or brownout that causes damage to the unit it is backing up? Better yet why not have it installed in a location where condensation is not normally going to be an issue.

 

[T.M.Haja Sahib]

Your two inks are diametrically opposed.

That depends on what you want to see.

 

[Besoeker]

That depends on what you want to see.

Or believe.

 

[T.M.Haja Sahib]

what good is the standby if it is damaged by the same surge or brownout that causes damage to the unit it is backing up?

This is a put down to the Design Engineers all over the world.

 

[Besoeker]

This is a put down to the Design Engineers all over the world.

How so?
Doesn't kwired have a sound point?

 

[iMuse97]

It seems we have a difference of opinion and of experience.

I have seen both ideas implemented, but the more common in my experience is that the spare is kept on hand, but not energized.

The standby idea is implemented at the plant I'm presently working at by having two identical transformers and plant main feeders. These can be run parallel (the most common), or can each individually serve the complete needs of the plant. They run them parallel to reduce the loads and extend the useful life of the equipment.

I have also seen spares (not energized or even terminated on high or low side) as big as a small garage just waiting in the wings, so to speak. In one case, I asked how long it had been there, and they said it was purchased over 20 years ago. They do regular PMs on it, as the thing could cost well over 1M to replace.

 

[T.M.Haja Sahib]

How so?
Doesn't kwired have a sound point?

His point is invalid in electrical installations properly designed electrical engineers.

 

[Volta]

His point is invalid in electrical installations properly designed electrical engineers.

No, it is not. I copied the same text when I visited the links you provided. I didn't bother posting it as Besoeker already had. There is nothing confusing about the two statements, they are in conflict.

...

Your two inks are diametrically opposed. Sydney Water wants the standby transformer and cables to remain energised where practicable.
From the PCRA we have "Stand by transformers should be de-energized to conserve energy wherever possible except for monsoon period to avoid the possibility of moisture contamination."

...

 

[T.M.Haja Sahib]

I have also seen spares (not energized or even terminated on high or low side) as big as a small garage just waiting in the wings, so to speak. In one case, I asked how long it had been there, and they said it was purchased over 20 years ago. They do regular PMs on it, as the thing could cost well over 1M to replace.

Even though the equipment is sitting idle,the cost of PM would steadily increase.Apart from inflation,this is due to aging of components of the equipment due to adverse environmental effects.The cost of PM with standby (spare)energized may be compared to that with standby(spare) de-energized and suitable decision may be taken to reduce the overall cost

 

[T.M.Haja Sahib]

No, it is not. I copied the same text when I visited the links you provided. I didn't bother posting it as Besoeker already had. There is nothing confusing about the two statements, they are in conflict.

Kwired asserted that when main equipment fails due to surge,the energized standby equipment will also fail.I asserted that both main and standby equipments will not fail, as they are usually provided with properly designed surge protection and thus his point is invalid in such installations.

The Sydney water corporation practices keeping standby transformer energized all the time where practicable.

The PCRA recommends keeping standby transformer energized during the monsoon time.They recommend de-energizing the standby during other times because the risk of condensation in the transformer is low.

 

[Besoeker]

Kwired asserted that when main equipment fails due to surge,the energized standby equipment will also fail.I asserted that both main and standby equipments will not fail, as they are usually provided with properly designed surge protection and thus his point is invalid in such installations.

I don't agree. Surge suppression, divertors, and such have a finite capability. A surge with a greater amount of energy than their rating will not be contained and there is then a risk of damaging both main and standby units.

The PCRA recommends keeping standby transformer energized during the monsoon time.They recommend de-energizing the standby during other times because the risk of condensation in the transformer is low.

That's not right or at least a tad misleading. It completely changes the empasis.
The PCRA recommends that stand by transformers should be de-energized to conserve energy wherever possible except for monsoon period.
Many oil producing countries don't have monsoons. Think of the Middle East for example. The PCRA recommendation for them would be to have the stand be transformers de-energized all the time. This rather negates the points you made in posts #8 and #13.

 

[T.M.Haja Sahib]

I don't agree. Surge suppression, divertors, and such have a finite capability. A surge with a greater amount of energy than their rating will not be contained and there is then a risk of damaging both main and standby units.

That means the electrical installation is a poorly designed one.Also please note that now a days U.S courts do not admit damages due to surge as an act of god.

That's not right or at least a tad misleading. It completely changes the empasis.The PCRA recommends that stand by transformers should be de-energized to conserve energy wherever possible except for monsoon period.
Many oil producing countries don't have monsoons. Think of the Middle East for example. The PCRA recommendation for them would be to have the stand be transformers de-energized all the time. This rather negates the points you made in posts #8 and #13.

You should see the rationale behind keeping the standby transformer energized and take suitable action in particular cases accordingly.

 

[Volta]

Good grief.

 

[T.M.Haja Sahib]

Good grief.

Please elaborate.