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

Sent: Wednesday, December 14, 2011 11:55 AM To: Phil Hopkinson; Robert Berman Cc: Corkran, Jerry L; Aris Marantan; Katie Coughlin; Richard Parker; Brenda Edwards; Brian Coffey; Caitlin Johnson; Dan CTiedeman; John Cymbalsky; Chris Bolduc; Freeman, Jeremiah; Emily Marchetti; Zhimei Luo; Puesh Kumar; Alex Hofmann; 

Rosenfeld; Bob Saint; Bob Smith; Carlos Gaytan; Caskey, John; Charlie Drexler; Charlie Stevens; Chris Brown; Clark Silcox; 

Young; David Flaten; Eric Peterson; Fernstrom, Gary; Greg Coulter; Greg Rosenquist; Hirsch, Bruce R; James Lass; Jerry HJim Raba; Joanna Mauer; John Rossetti; Ken Winder; Mahesh P. Sampat; Matthew Nardotti; Maxine Savitz; Meg Waltner; 

Rivest; Millure, Dave; Pamela Costello; Phil Harter; Polinski, Raymond; Rick Anderson; Rob Greeson; Robert van Buskirk; R

Scott Beck; Simmons, Chuck; Steve Nadel; Steve Rosenstock; Ted Johnstone; Thomas Petrosino; Tim Ballo; Tom Eckman; 

Subject: RE: Distribution Transformer loading 

Phil & Robert,

It is incorrect to say that we “target” 70% loading. We use the smallest kVA size that:

a) has a capability (which is greater than nameplate) in excess of the expected peak load

b) meets, along with the service and any secondary cables, the voltage and flicker drop limits

The result is that on the average for the whole one million plus transformers, my average peak load is 70% of the namepl

Any individual transformer can have a load of anywhere from 0.01% to 225% of nameplate at peak. (The small pole‐bolt t

come anywhere near the 65C rise at nameplate and I take advantage of that.)

In general, distribution equipment is not quite “run to failure” but rather “run to problem”. There has to be an issue with 

will change an installed one out ‐ customer voltage complaint; customer adding load in excess of transformer capability; p

replacement/relocation; oil leak; etc. Replacements and new installations are sized according to the load and the voltage 

never replace a transformer to get closer to 70% loading.

‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ For transformer losses and efficiencies, I agree and disagree with both of you:

Most of the small transformers will see customers that are on the E1 rate schedule. This is probably 80% of the transform

of the $ value in transformer purchases. Our spend on three‐phase pad‐mounts usually exceeds our spend on single‐phas
The load‐loss component of the transformer losses is going to follow the square of the daily load profile so neither the pe

the yearly‐load factor is the correct number to use for the efficiency evaluation. It should be somewhere between the tw

evaluation may be correct for the small overhead transformers.

Let me call your attention to the other rate classes. I have six rate classes that have annual load factors above 75%. Those 

the larger loads which tend to be single customers on a single large transformer. For the larger transformers, DOE’s evalu

low.Dan MulkeySr Consulting Electrical Engineer

Pacific Gas & Electric Co

DHM3@PGE.COM

415‐973‐4699 office415‐264‐9260 cell

From: Phil Hopkinson [mailto:phopkinson@hvolt.com] 

Sent: Tuesday, December 13, 2011 7:41 PM To: Robert Berman Cc: Corkran, Jerry L; Mulkey, Dan; Aris Marantan; Katie Coughlin; Richard Parker; Brenda Edwards; Brian Coffey; Caitlin JoJennifer 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; Fernstrom, Gary; Greg Coulter; Greg Rosenquist; Hirsch, Bruce R; James LSchoen; Jim Raba; Joanna Mauer; John Rossetti; Ken Winder; Mahesh P. Sampat; Matthew Nardotti; Maxine Savitz; Meg W

Hyland; Michael Rivest; Millure, Dave; Pam Costello; Phil Harter; Polinski, Raymond; Rick Anderson; Rob Greeson; Robert v

Ryan, Paul; Scott Beck; Simmons, Chuck; Steve Nadel; Steve Rosenstock; Ted Johnstone; Thomas Petrosino; Tim Ballo; To

Patterson Subject: RE: Distribution Transformer loading 

Hi Robert and all:

You don’t seem to relate to meter load numbers and seem instead to want to make the numbers apply to transformer loa

you contact Dan Mulkey and speak with him. By copy to Dan, you may wish to make a comment here yourself.
Your arrows are perfect:

1. The Load factor for the meter E1 relates to an RMS equivalent load on the transformer of 70% of nameplate per P

2. The peak daily load on the meter may or may not be in synch with all of the other meters on that transformer but 

peak daily loads of 2 times the average. If all of the meters are seeing the same peak then the transformer carrie

at that time.

3. I do not see why that is so unusual to you because it is general practice to have cold load pickup reach as high as 2

The IEEE Loading guide allows up to 200% of nameplate load for up to 30 minutes.

4. Liquid filled distribution transformers have very high thermal ridethrough. The time constant of the core and oil 

minutes and is the reason for the excellent thermal ridethrough. The winding over oil time constant is faster but 

tremendous capability to sustain overloads without significant insulation loss of life.

5. My contacts with Ameren UE and Empire District Electric Company shows that all are taking advantage of the loa

offset some of the cost increases of new transformers. This is likely to become quite widespread.

Best regards,

Phil

Philip J Hopkinson, PE President & CEO HVOLT Inc. 3704 High Ridge Rd. Charlotte, NC 28270 phopkinson@hvolt.com

Ph 704-846-3290 Fx 704-845-2520 Cell 704-236-3320 www.hvolt.com

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

Sent: Tuesday, December 13, 2011 10:20 PM To: Phil Hopkinson Cc: Robert Berman; Corkran, Jerry L; Dan Mulkey; Aris Marantan; Katie Coughlin; Richard Parker; Brenda Edwards; Brian 

Dan Cohen; Jennifer Tiedeman; John Cymbalsky; Chris Bolduc; Freeman, Jeremiah; Emily Marchetti; Zhimei Luo; Puesh KuAndrew Delaski; Art Rosenfeld; Bob Saint; Bob Smith; Carlos Gaytan; Caskey, John; Charlie Drexler; Charlie Stevens; Chris 

Creevy, Jim; Daniel Young; David Flaten; Eric Peterson; Gary Fernstrom; Greg Coulter; Greg Rosenquist; Hirsch, Bruce R; J
Hodge; Jerry Schoen; Jim Raba; Joanna Mauer; John Rossetti; Ken Winder; Mahesh P. Sampat; Matthew Nardotti; Maxine 

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

Robin Roy; Ryan, Paul; Scott Beck; Simmons, Chuck; Steve Nadel; Steve Rosenstock; Ted Johnstone; Thomas Petrosino; TWes Patterson Subject: Re: Distribution Transformer loading 

You appear to have a knack for ignoring hard data in favor of calculated possibilities, no matter how unlikely or Possible "could" and "can" possibilities are not relevant when actual experience is reported. PG&E peak loads ar

below. Moreover, because utilities value reliability very highly, prudence would obviate against planning to oper

133% of nameplate rating. Indeed, any sort of load growth would likely necessitate frequent replacement in addi

outage risk. Regards, Robert A. Berman, Principal Berman Economics www.BermanEconomics.com

1915 Grand Court Vienna, VA 22182 703-281-0490 
703-655-8398 (cell) 

BermanEconomics@gmail.com

On Dec 13, 2011, at 6:13 PM, Phil Hopkinson wrote: 

Hello Robert and all:No, his peak loads go well past the nameplate rating of the transformers. He is quite emphatic that his RMS equivalent lo

is 70% of the nameplate rating.

<image002.png> Look closely at the summary chart for the E1 rate class and I will guide you through the numbers:

1. His average meter draws 0.785 kW RMS over a 365 day, 8760 hour year.2. At his daily peak, the average meter draws about 2 times the average and hits 0.785 * 0.74/0.39 or 1.489 kW RMS.3. At maximum the loading on any given meter can hit 1.99 kW RMS.4. Over a longer period like a month the average peak load per meter is 0.785 * 0.51/0.39 or 1.03 kW RMS.5. Since he achieves 70% RMS equivalent load on average, his daily peak could actually be 70% * .74/.39 or 133% of namep

occur on all meters on the same transformer at the same time.

6. Since he achieves 70% RMS equivalent load on average, we can see that his average monthly peak can be as high as 70% 

nameplate if all of the meters see the same peak conditions.

7. If the cause of peak load is weather related then it is indeed likely that the transformer will see more than 100% load suc

heat wave or during a cold spell.

I will soon send out loading patterns for other utilities. The point is that there has been a change in loading practice and w

the same if transformer selling prices get pushed up by higher efficiency requirements being imposed.

Best regards,Phil
Philip J Hopkinson, PE 

President & CEO HVOLT Inc. 3704 High Ridge Rd. Charlotte, NC 28270 phopkinson@hvolt.com

Ph 704-846-3290 Fx 704-845-2520 Cell 704-236-3320 www.hvolt.com

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

Sent: Tuesday, December 13, 2011 5:27 PM To: Phil Hopkinson Cc: Robert Berman; Corkran, Jerry L; Dan Mulkey; Aris Marantan; Katie Coughlin; Richard Parker; Brenda Edwards; Brian 

Dan Cohen; Jennifer Tiedeman; John Cymbalsky; Chris Bolduc; Freeman, Jeremiah; Emily Marchetti; Zhimei Luo; Puesh KuAndrew Delaski; Art Rosenfeld; Bob Saint; Bob Smith; Carlos Gaytan; Caskey, John; Charlie Drexler; Charlie Stevens; Chris 

Creevy, Jim; Daniel Young; David Flaten; Eric Peterson; Gary Fernstrom; Greg Coulter; Greg Rosenquist; Hirsch, Bruce R; JHodge; Jerry Schoen; Jim Raba; Joanna Mauer; John Rossetti; Ken Winder; Mahesh P. Sampat; Matthew Nardotti; Maxine 

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

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

Wes Patterson Subject: Re: Distribution Transformer loading

Sorry, the average load factor is what it is -- striving notwithstanding. All the striving in the world is not going to factors of a rural electric, for example, regardless of what they want or how much they want it. That's why Dan r

average load at 39% and the peak day load at 70%. I suspect that his guidance is to make the average load of the 

peak day equal to 70% of the nameplate rating. That would make sense as opposed to larger, historical oversizin

also lower transformer purchase costs. Dan does, indeed, buy a very large number of 15 kVa transformers for his E1 rate class (not load class). This is fcustomers in rural mountainous areas. PG&E buys so many in large part because the casualty rate due to lighteni

Regards,Robert A. Berman, Principal
Berman Economics

www.BermanEconomics.com

1915 Grand CourtVienna, VA 22182703‐281‐0490

703‐655‐8398 (cell)

BermanEconomics@gmail.com

On Dec 13, 2011, at 5:07 PM, Phil Hopkinson wrote: Good afternoon Robert and all:

1. No that is not the correct interpretation. I spoke extensively with Dan Mulkey, the PG&E Transformer Engineer. The 39% 

meter basis and is the average load for that meter divided by the maximum load for that meter. Since all meters of the sa

it is the average load divided by the maximum load for all of the meters of that class.

2. The transformer loading is a different calculation. Effectively, PG&E under Dan Mulkey’s guidance strives to make the av

transformer equal to 70% of the Nameplate rating of the transformer.

3. Transformers are chosen for the application based on achieving 70% RMS equivalent load on the transformer and on rem

acceptable flicker and load regulation. He often times chooses a 15 kVA transformer for 10‐15 meters of load class E1.

I have spoken with Ameren UE this afternoon as well and they have within the last 5 years modified their transformer sizi

heavier loading so as to minimize their transformer purchase budget.

Best regards,PhilPhilip J Hopkinson, PE President & CEO HVOLT Inc. 
3704 High Ridge Rd. 

Charlotte, NC 28270 phopkinson@hvolt.com

Ph 704-846-3290 Fx 704-845-2520 Cell 704-236-3320 www.hvolt.com

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; Pam Costello; Phil Harter; Polinski, Raymond; Rick Anderson; Rob Greeson; Robert B

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 r

is 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 t12. 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 MulkeySr Consulting Electrical EngineerDHM3@PGE.COM415‐973‐4699 office415‐264‐9260 cell<Electric Rate Schedules.xls><2006 Load Profile.xls>