Power Transformer Specifications 5

[Linspire]

Hi guys,

I would like to ask does a Power Transformer specications with lower rated power eg. 80 MVA applicable for a higher rated power eg 120 MVA but both are same rated voltage eg. 132/36 kV.

 

[waross]

Even two transformers for the same voltages and the same KVA or MVA base may have different specs.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Linspire]

Same voltage and same MVA for two power transformer may not have same specifications ?
Can you give me some justfication or clarification ?

 

[Marmite]

The specification is a written document prepared by the purchaser for the purposes of securing bids for the manufacture of the transformer from prospective manufacturers. The specification may reference other standards and specifications such as IEC. It can be the same specification for both transformers, but there is no guarantee that it will be.

Regards
Marmite

 

[Linspire]

Ok,thank you.

 

[bacon4life]

There could many differences, some of which may be utility specific preferences and some of which are actual electrical differences that could prevent interchangeability. Utility preferences might include: brands of accessories, types of monitoring equipment, conservator vs nitrogen blanket, fall protection methods for top access, type of bushing terminals and color of paint. Electrical differences could include: 50Hz vs. 60 Hz, vector group (i.e. Delta-wye), GSU vs step down, percent impedance, having a DETC, having an LTC, the range of the tap changers, which part of the winding the tap changers are located on, BIL ratings, physical arrangement of surge arrestors & bushings, nonstandard conditions such elevation above 1000 meters or ambients different than 30 C, and the seismic design & anchorage method.

 

[Linspire]

Alright, I get your point,bacon4life.

That's mean manufacturer does have capability to design according Utility's preference specifications.

 

[ScottyUK]

Most manufacturers have the capability, but they don't always have the commercial will. They all want to build a transformer which is somewhere near to one of their standard designs, and any constraint imposed by the specification which requires them to deviate substantially from their standard methods of manufacture may result in either a high bid to cover the extra engineering or, more rarely, a decline-to-bid response.

 

[k0412d]

One can also refer to "IEC 60076-1 Annex A (normative):Information required with enquiry and order"

Giving normal and special information to give for an order.

 

[Linspire]

Nice for everyone input.

 

[prc]

There will be hardly any difference between the spec of a 80 MVA and 100 MVA transformer, unless of course you are stipulating the current rating of tap changer /bushings etc.The best tutorial on Transformer specifications is CIGRE technical Brochure No156 " Guide for customer specifications for transformers 100 MVA and 132 Kv &above", issued in April,2000.This give all aspects to be considered while drawing up specifications , GTP etc,etc.You can have it from e-cigre.org.

 

[Linspire]

Prc, you given the website is not accessible ?

 

[Linspire]

Prc, I manage to enter the website but I did not manage get magazine due to subscription.

 

[prc]

Sorry Lispire. You can get free access only if you become a CIGRE member. Then you can download not only this brochure ,but hundreds of study reports on T &D subjects in addition to CIGRE journal.Otherwise you can buy this document alone from CIGRE.
Attached please see a recent tutorial from Canada on the subject.

 

[Linspire]

Thank you, prc for your sharing this documents.
Hope this document might help someone else too.

 

[ScottyUK]

The excellent J&P Transformer Book has a chapter on specifications. The book overall is worth a read because it will help you understand why and when certain features are desirable and why certain features are not desirable.

If you work for a utility then the operations and maintenance groups will probably have opinions about what is desirable on a new transformer and will certainly have opinions about what is not . They will also be able to identify which brands of accessory they find reliable and which they find troublesome, which they get support for and which ones they don't. Their opinions should be considered and balanced against other requirements.