Transformer Loss Evaluation Prices 2

[111R]

Are there any documents or tech papers that explain the basic criteria for determining dollar amounts assigned for loss evaluations?

I know the no load loss dollars/kW is typically twice the load loss. Is this simply due to it existing at all times even when the transformer is serving no loads or small loads?

Are there any requirements on the maximum losses or minimum efficiency of a power transformer? For example, what is the motivation to a transmission provider to spend additional money for a very efficient transformer?

Thanks

 

[dpc]

Google is your friend:

http://www.abb.us/product/ap/db0003db004283/f4a2f36855184744c125772700291244.aspx

Determination of the "cost" of transformer losses is a present worth analysis of future discounted cash flows (energy costs). As such, it is sensitive to your assumptions regarding the future, including:

Life expectancy of the transformer
Future cost of electricity
Inflation rate
Interest rate

The motivation is strictly financial. Pay more up front to save money over time.

There are standards for transformer efficiency - for certain types of transformers.

 

[racookpe1978]

Another is "replacement time" ...

You will need 3x transformers to deliver 3 phase power, right? So buying a fourth (spare) transformer is "wasted" money, until one of those 3x on-line transformers blows out, burns, or fails. Then your entire plant is out-of-service until a new properly-sized transformer is either located and shipped to site and installed, or can be built from scratch to the right spec's. So, the "wasted" price of the spare adds to the purchase price, but has to be done as "insurance" against possible complete failure. Buying 4x good-quality, more-reliable, better efficiency transformers is necessary, because if 1 fails, the replacement needs to be equal to the other two still in service.

But, If you have 4 identical generators in a row in one power plant, or 8 identical generators in the same local area - each generator with 3x on-line transformers, do you need a fourth spare transformer at each of the stations?

If you have 8x (smaller) generators (each of 250 MegaWatt) available so the short-term loss of one transformer is not "too critical", do you need every transformer behind every generator to be as reliable as you do when you only have one power plant of 1200 MegaWatt capacity generating all of your revenue?

 

[dpc]

The reliability and replacement time issue relates to buying three or four single-phase transformers versus a single three-phase transformer as well as the quality and reliability of the components. Once that decision is made, the cost of transformer losses would still need to be evaluated. I don't think that transformer efficiency and long-term reliability can be directly correlated - either positive or negative.

 

[prc]

The standard for transformer loss evaluation is IEEE C57.120 -1991 Loss evaluation Guide for Transformers and Reactors. There was much simpler USBR guide which is unfortunately missing from their site.You will get all theory and logic for this life cost of losses from above document.

 

[jkristinn]

111R: Your assumption regarding the reason for the price difference between no-load losses and load losses is correct, but the price ratio can be anywhere between 0 and 1, depending on the expected loading of the unit.

 

[prc]

Sorry. I made a mistake. The tutorial is not by USBR,but RUS bulletin 1724E-301.

http://www.rurdev.usda.gov/supportdocuments/uep_bulletin_1724e-301.pdf

-US Department of Agriculture _Rural Utilities service –Guide for the evaluation of Transformer losses.

You can get it from google too.This is the best tutorial on the subject.The ratio between no-load loss to load loss is not always 2,it can vary from 1 to 4 depending on the load factor on the transformer.

 

[111R]

Thanks all. I appreciate the link, prc. That is very helpful.

 

[squeeky]

Great Link. Will have to look at it in detail. Thanks.

 

[waross]

For example, what is the motivation to a transmission provider to spend additional money for a very efficient transformer?

I worked in one jurisdiction where the utility tariffs imposed a surcharge on the monthly billing if the transformer efficiency was below a benchmark.

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