Transformer Load Loses 1

[joan271273]

Can someone indicate how can I estimate my utility costs if I meter in the primary vs the secondary. Let assume a rate of 0.10 $/KW as a utility rate.
For the transformer I have this data:

Transformer data:

Vprim= 115kV
Vsec= 12.47kV
Rating (kVA) = 20000 55c/OA,26670 55c/FA,33330 55c/FA/FA
= 22400 65c/FA, 29870 65c/FA, 37330 65c/FA/FA

Load Loss 99800 W
No-Load Loss 16823 W
Total Loss 116623
Perecnt Impedance = 9.19%

 

[SooryaShrestha]

joan271273
Do you need to make any correction to your post? Like the utility rate given is in $/kW instead of $/kWH?
calculating the metering on the primary side seems to be unchanged, though there are possibilities of calculating the auxilliary supply cost inclusive.
However if you want to make cost calculation based on the metering on the secondary side, then the capitalised cost of all the load and noload losses need to be incorporated.
Some further data are also required like load pattern or the number of hours of loads, interest rate. All these need to be capitalised for the life of the transformer. Generally you must have the capitalised cost of load and noload losses at the time of procurement of the transformer. Those values can be utilised to determine the charges for the transformer losses. the calculation can be very simple, in which case the probability of being correct is lower compared to the complex calculation. You will have enough information in GE Distribution Data book.
Regarding the data of losses which you have given please indicate the load loss data is on the basis of the OA or FA or FA/FA rating. I have found this always confusing.

 

[GYakle]

I might suggest REA Bulletin 65-2 April 1978 Evaluation of large power transformer losses. This guide steps you through the process in determining cost of ownership of the transformer due to losses. You will have to refer to the transformer test data but typically losses are expresed in terms of the base OA of the unit.

 

[jack6238]

joan271273
Joan you need to create a loss curve for this transformer.If you meter on the primary the losses will be included in the utility bill-secondary metering will not include these losses. The information you have provided for this transformer is sufficient to create this curve. I have been out of the country for two months and do not have the time today to calculate this curve. In any event I will provide something by next Thursday.
Jack6238

 

[joan271273]

Thanks for the offer to develop this curve, do you think the REA document listed in a previous thread a good source for this. I am still trying to locate a copy.

Thanks

 

[jbartos]

Suggestions:
1. Cooling clarifications are needed, e.g. FA/FA (What about FOA?)
2. Clarify the cooling type for normal continuous operation
3. Losses will increase with the increased cooling, e.g. for FOA
4. Transformer worst case manufacturing tolerances
5. Check ANSI/IEEE C57.12.00-1987 or latest and related references for more info.
6. Etc.

 

[jack6238]

joan271273
I will create the curve in an excel spread sheet and either fax or email the file. In the meantime, this transformer has an X/R ratio of 18.3897, a peak efficiency occurring at 41.06 % load on a 20 MVA base,the % iron loss is .084115 and the % copper loss is .499. I will use this data to construct the efficiency curve vs per unit load. From this curve you can determine the losses at any value of load and calculate the operating cost for secondary metering. Please send fax number or email information.
This topic is covered in detail in several transformer books. the one I like the best is
The J&P Transformer Book-11th Edition, A Practical Technology of the Power Transformer, by Franklin and Franklin.

 

[jack6238]

joan271273
I have finished the curves. I have created an efficiency curve and a loss curve. I await your fax or email and I will send. I have created curves for a load power factor of .8 and 1.0. If you will send the operating power factor, I will create a unique curve for the exact operating condition. The unit has an efficiency of 99.4986 % at ~40 % load at a power factor of .8 and an efficiency of 99.5985 % when operated at ~40 % load at a power factor of 1.0. The unit operates above 99 % efficiency at nearly all values of load.

 

[joan271273]

Jack6238, I do not have your fax# or e-mail. I the following Fax # 408 920 9768

Thanks for your help

 

[jack6238]

joan271273
email-jackwoodham@cinci.rr.com
You should have the information I sent.