From: Kenneth Winder [mailto:kwinder@mleainc.com] 

Sent: Tuesday, November 01, 2011 9:30 PM 

To: Richard Parker 

Cc: Corkran, Jerry L; Caitlin Johnson; rick.anderson@faypwc.com; tballo@earthjustice.org; 

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Brian Coffey; gjrosenquist@lbl.gov; Rosenstock, Steven; Michael Rivest; Jerry Hodge; 

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Subject: Re: Transformer Loading Examples 

Mr. Parker and Committee: 

 Attached are two spreadsheets showing a sampling of transformer loading on Cooperative 

systems. 

 The first spreadsheet is information from a North Carolina Cooperative showing 20 residential 

transformers, each serving one residential customer. Annual Peak Load is provided for each of 

those transformers. As a group, on the annual non-coincidental peak basis, the average peak 

transformer load is about 70% of the transformer rated capacity. 

 The second spreadsheet is information from a Kentucky Cooperative showing the Annual 

System Peak load served through distribution transformers. The total kVA capacity of the 

distribution transformers is only 29% utilized at the time of the Annual System Peak. 

 

 The information attached for these Cooperatives is not significantly different than other such 

information that is being provided to the Committee and LBL. I think this information 

represents normal utility operation for LFMV transformers. 

 The information attached shows that these Cooperatives do not load their transformers heavily 

at the time of the distribution transformer peak load, and that there is a considerable amount of 

diversity between the distribution transformer peak loads and the System peak load. 

 Modeling the above type of transformer loading will produce results that differ from the 

original LBL model because the loading in the original model was much different. How much 

the results change may or may not be significant, but it is important to have confidence that the 

model represents acceptable operation of these LFMV transformers. 

 An improved model should provide a more correct picture of the operating efficiency, loss 

costs, and payback period. Hopefully, the sensitivity analysis will also be more meaningful. 

 

Ken 

 
-- 

Kenneth A. Winder, P.E.

Manager-Engineering

Moon Lake Electric Association 

800 W Hwy 40 

PO Box 278 

Roosevelt UT 84066

435.722.5406 Office

435.724.1539 Cell 

435.722.5466 Fax

E-Mail: kwinder@mleainc.com

Web Site: www.mleainc.com