×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Construction of Transformer

Construction of Transformer

Construction of Transformer

(OP)
Hi,

I'm curently involved in a cogeneration plant project. We have procured few auxiliary transformer. Our technical standards specify the followings:

"Oil-immersed transformers rated 1600 kVA and below shall be hermetically sealed. Transformers rated above 1600 kVA and up to 3150 kVA, may be either hermetically sealed or of the conservator type. However, hermetically sealed transformers above 3150 kVA shall be subject to Principal approval."

However, the supplier requested for deviation and propose to supply the non-hermetically sealed type transformer for 250 kVA. Is this common in industry?

Thanks

norzul

RE: Construction of Transformer

Very small conservator types are not especially common in the UK. Hermetic transformers arguably require a little less maintenance, and this is the reason why they are more popular with the distribution companies. Conservator-type transformers usually have more complex instrumentation requirements than hermetics, but that is largely a factor of size and value; on such a small transformer it may not be considered economical to fit more than the basics.

----------------------------------
  Start each day with a smile. Get it over with.

RE: Construction of Transformer

(OP)
TQ ScottyUK....appreciate if you can further qualify what do yu mean by "factor of size and value".

Just wonder...for this small transformer why the supplier insist to supply the conservator type. From cost point of view I think it is more expansive. From maintenance point of view, looks like we may require more maintenance. It's like loose-loose situation not win-win...??

Fyi..the contract that we have is lump sum type i.e. we are not going to pay for the additional cost incurred by the supplier.

RE: Construction of Transformer

The comment regarding "...size and value..." was really to suggest that although most conservator-type transformers have more instruments and protection functions, this isn't solely because they are of that design. Larger transformers tend to supply larger loads, or multiple small loads, and loss of such a transformer typically causes greater disruption than loss of a small type. They are also major capital assets, and the cost of better protection is a diminishing percentage of total cost as the transformer size increases, so it becomes economical to find sophisticated protection to, say, a GSU transformer whereas that protection might cost more than the total value of a small distribution transformer.

That logic doesn't entirely apply to your excitation transformer because loss of that one small transformer will shut down the generator just as effectively as loss of the GSU transformer, unless you are very lucky and have redundant excitation transformers. It would however be a relatively small task to remove and replace the excitation transformer if it failed, and relatively inexpensive to hold one as a spare for that eventuality.

So far as why so supplier wants to supply a conservator type, I can only guess that they have no experience of hermetic types, or are using a stock design rather than devloping a new one, or they have some stock of the conservator type already available.

----------------------------------
  Start each day with a smile. Get it over with.

RE: Construction of Transformer

Oops - I said 'excitation transformer' when should have said 'auxiliary transformer'. Thoughts from my real job spilling through into my online one!

----------------------------------
  Start each day with a smile. Get it over with.

RE: Construction of Transformer

(OP)
What are the disadvantages of hermetically sealed transformer as compared to that of conservator type?

RE: Construction of Transformer

Norzul,
I am not sure where you are located but in the USA I have not heard of 'hermetically sealed' transformers for normal distribution duty in the size you are specifying.

I would expect either a welded tank or gasketed bolted tank with a pressure relief valve, fill and drain valves, bolt on bushings, bayonet fuse etc; most of which would preclude 'hermetically sealed'.

I suggest you find a brand name you trust and go to their website or catalog and seek how their transformers are constructed, maybe check a couple of them out and write a spec about what you really need after seeing this.

RE: Construction of Transformer

(OP)
Dear Electic/Guys,

Fyi, I'm currently involved in a cogeneration project, 120 MW (4 Gas Turbines + 4 Heat Recovery Steam Generators + 1 Steam Turbine). It is a lump sum turnkey kind of project. Now, the status is towards the end of detailed design/procurement phase. We'd issued POs for the GTs and ST. Our company's technical standards require hermetically sealed transformer for 1600 kVA and below.

The GT supplier complies with our stds. Unfortunately the ST supplier doesn't comply. The problem is, we just realized about this. Contractually we could still force them to comply....but...the schedule most likely will be affected & cause project delay...1st I try to convince myself that the conservator type is perfectly OK and perhaps more technically superior as compared to that of hermetically seal...before I go to my management for explanation...

Thanks

norzul

RE: Construction of Transformer

(OP)
Actually I'm looking for technical justifications to have conservator type transformer...perhaps yu guys can help me...since I'm not an electrical engr by dicipline.

RE: Construction of Transformer

If I understand correctly the conservator type transformer is more appropriate for larger transformers over 10MVA. Even then it is a rarity these days with most manufacturers offering a nitrogen blanket system instead.

Read my previous post about standard specs for the size of transformer you anticipate.  Hermetically sealled and Conservator both sound like oddballs for 1.6MVA.

 

RE: Construction of Transformer

(OP)
TQ Electic....I do agree with yu, however what I don't understand is why conservator type is appropriate for larger transformer over 10MVA i.e. needs for technical explanation

RE: Construction of Transformer

In our case, we accept both type of trxs for our distribution network and there is no preference to any one of them.  Personally, I will think this is the design concept adopted by different manufacturers where they will normally stick to the type that they have sent for type-test(for that particular ranges of trxs).

The hermetically sealed type as mentioned earlier by ScottyUK claims to be "less maintenance" than conservator type. For the latter, one needs to replace the silica gel for the breather more often.

Electric,
Just wonder what is the normal distribution size of transformer used in USA if not as mentioned by norzul (1600kVA and below) ?  FYI, hermetically sealed trx can be either adopted gas cushion (I presume same as nitrogen blanket) or thinner cooling fin system for 'breathing' purposes which are both acceptable in our MV distribution system.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources