From: Robert Berman [mailto:bermaneconomics@gmail.com] 

Sent: Tuesday, December 13, 2011 4:17 PM To: Corkran, Jerry L Cc: Dan Mulkey; Phil Hopkinson; Aris Marantan; Katie Coughlin; Richard Parker; Brenda Edwards; Brian Coffey; Caitlin JohJennifer Tiedeman; John Cymbalsky; Chris Bolduc; Freeman, Jeremiah; Emily Marchetti; Zhimei Luo; Puesh Kumar; Alex H

Delaski; Art Rosenfeld; Bob Saint; Bob Smith; Carlos Gaytan; Caskey, John; Charlie Drexler; Charlie Stevens; Chris Brown; Jim; Daniel Young; David Flaten; Eric Peterson; Gary Fernstrom; Greg Coulter; Greg Rosenquist; Hirsch, Bruce R; James La

Schoen; Jim Raba; Joanna Mauer; John Rossetti; Ken Winder; Mahesh P. Sampat; Matthew Nardotti; Maxine Savitz; Meg W

Hyland; Michael Rivest; Millure, Dave; Pamela Costello; Phil Harter; Polinski, Raymond; Rick Anderson; Rob Greeson; Robe

Buskirk; Robin Roy; Ryan, Paul; Scott Beck; Simmons, Chuck; Steve Nadel; Steve Rosenstock; Ted Johnstone; Thomas Pet

Eckman; Wes Patterson Subject: Re: Distribution Transformer loading 

It appears that the 70% load factor occurs only on the peak day. The annual load factor for 80% of the meters is ris consistent with 38% implied load factor PG&E filed in it's 2007 rate case (A=$7.268, B=$1.063). These resultwith the national distribution of loads used by LBNL. Regards,Robert A. Berman, Principal

Berman Economicswww.BermanEconomics.com

1915 Grand CourtVienna, VA 22182703‐281‐0490

703‐655‐8398 (cell)

BermanEconomics@gmail.com
On Dec 13, 2011, at 3:26 PM, Corkran, Jerry L wrote: 

Dan Mulkey and Phil Hopkinson – the attached loading data and the explanation of how PG&E loads their new transforme

the nameplate rating is very factual and the most accurate explanation I have heard about how the utilities load their new 

have all heard the terms “Smart Grid”. This appears to be an example of a smart customer using the latest technology to 

efficient use of new transformers.

For the 30 year time frame that is being considered for the DOE transformer efficiency rules, it seems logical that most ut

similar smart process as is being used by PG&E to size the transformers and that a loading target similar to the 70% loadin

will be adopted by the utility industry. This is expected to result in load levels much higher than the 25% to 40% loads use

calculate the pay backs for the various loss levels considered. The key question is what loading will be used on new trans

and not what loading exists on some unit installed long before the smart meters existed.Dan – Are you available to answer emails if the DOE WG has additional questions?

Members of the DOE WG who are utility employees: Please comment about the practice that PGE is using to load their ne

does your company currently do to size transformers and what will your company do in the future to efficiently load the 

installed on your systems?

Members of the DOE and Navigant who are involved in the evaluations of the transformer designs: Please comment ‐ Wo

Navigant consider using a higher load factor in the DOE payback calculations? Based on the 70% load factor targeted by 

customers, it seems that the DOE study payback results are not accurate and that they should be revised to some load fa

latest technology that the utilities will routinely be using based on the future 30 year time frame being considered.

Regards,

Jerry Corkran

From: Mulkey, Dan [mailto:DHM3@pge.com] 

Sent: Tuesday, December 13, 2011 1:42 PM To: Phil Hopkinson Cc: Corkran, Jerry L; Meyers, Aaron; Trujillo, Antonio Subject: RE: Distribution Transformer loading
Phil:

It is good to hear from you again as I missed attending the last IEEE Transformers Committee Meetings in Boston.

You have asked about load cycles at Pacific Gas & Electric and in fact we have public information that is readily availab

There are approximately 5.1 million meters on the PG&E system. The average data from test meters for each rate class 

commercial and industrial is displayed on an hourly basis for all 8760 hours in a year. Multiple years of data are availa

website. The attached EXCEL spreadsheet is an extract of the data for 2006. The rate classes are defined in the second 

This data is not organized by transformer type but there are a number of factors that are significant to understanding the 

1. The summary data by rate class is shown at the very bottom of the spreadsheet.

2. A snapshot of the summary data is shown below:

3. <image001.png>

4. The hourly readings are the kWHrs consumed which is also the average kW load during that hour.

5. Rate class E1 is the most abundant class. I estimate that it accounts for approximately 80% of the meters.

6. Rate class E7 is also residential but is Time of Use service, and probably accounts for ~5% of the meters. This class is mos

for homes where people can shift their energy consumption to off‐peak times.

7. The various other rate classes are also defined in attachment 2.

8. The yearly load factor is equal to the average load divided by the max load.

9. For PG&E the average transformer is loaded to approximately 70% of nameplate. While the peak loads are normally with

transformer, the peak loads will often exceed the nameplate rating of the transformer.

10. It is usually the physical location and grouping of the customer service points that determines the needed transformer.

11. For most transformer installations the limiting factor is usually the voltage or flicker drop rather than the kVA size of the t

12. A given transformer can be placed into service for a wide variety of loads. For instance, the same 25 kVA single‐phase pad

to supply everything from a single signal light, to a single isolated residential customer, to fifteen or so residential custom

coastal area.

13. While the average distribution transformer serves 5 customers, the range is from one to several hundred.

14. PG&E attempts to take advantage of the full capability of our transformers to achieve favorable economics for our rate

I hope that this explanation helps.Best regards,
Dan Mulkey

Sr Consulting Electrical Engineer

DHM3@PGE.COM

415‐973‐4699 office415‐264‐9260 cell

<Electric Rate Schedules.xls><2006 Load Profile.xls>