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

Sent: Wednesday, December 14, 2011 12:17 PM To: Mulkey, Dan; Robert Berman Cc: Corkran, Jerry L; Aris Marantan; Katie Coughlin; Richard Parker; Brenda Edwards; Brian Coffey; Caitlin Johnson; Dan Cohen; J

Cymbalsky; Chris Bolduc; Freeman, Jeremiah; Emily Marchetti; Zhimei Luo; Puesh Kumar; Alex Hofmann; Andrew Delaski; Art RoseCarlos Gaytan; Caskey, John; Charlie Drexler; Charlie Stevens; Chris Brown; Clark Silcox; Creevy, Jim; Daniel Young; David Flaten; 

Greg Coulter; Greg Rosenquist; Hirsch, Bruce R; James Lass; Jerry Hodge; Jerry Schoen; Jim Raba; Joanna Mauer; John Rossetti; 

Matthew Nardotti; Maxine Savitz; Meg Waltner; Michael Hyland; Michael Rivest; Millure, Dave; Pamela Costello; Phil Harter; PolinskRob Greeson; Robert van Buskirk; Robin Roy; Ryan, Paul; Scott Beck; Simmons, Chuck; Steve Nadel; Steve Rosenstock; Ted Johns

Ballo; Tom Eckman; Wes Patterson Subject: RE: Distribution Transformer loading 

Good input Dan and thank you for adding your valuable insight.

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: 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 Cohen; J

Cymbalsky; Chris Bolduc; Freeman, Jeremiah; Emily Marchetti; Zhimei Luo; Puesh Kumar; Alex Hofmann; Andrew Delaski; Art RoseCarlos Gaytan; Caskey, John; Charlie Drexler; Charlie Stevens; Chris Brown; Clark Silcox; Creevy, Jim; Daniel Young; David Flaten; 

Greg Coulter; Greg Rosenquist; Hirsch, Bruce R; James Lass; Jerry Hodge; Jerry Schoen; Jim Raba; Joanna Mauer; John Rossetti; 

Matthew Nardotti; Maxine Savitz; Meg Waltner; Michael Hyland; Michael Rivest; Millure, Dave; Pam Costello; Phil Harter; Polinski, R

Greeson; Robert van Buskirk; Robin Roy; Ryan, Paul; Scott Beck; Simmons, Chuck; Steve Nadel; Steve Rosenstock; Ted JohnstoneTom Eckman; Wes Patterson 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 nameplate

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

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 a transf

installed one out ‐ customer voltage complaint; customer adding load in excess of transformer capability; pole replacement/reloc

Replacements and new installations are sized according to the load and the voltage drops, but I would never replace a transforme

‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 

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 transformers but in transformer purchases. Our spend on three‐phase pad‐mounts usually exceeds our spend on single‐phase pole‐bolts.

The load‐loss component of the transformer losses is going to follow the square of the daily load profile so neither the peak‐day l

factor is the correct number to use for the efficiency evaluation. It should be somewhere between the two, so DOE’s 50% evaluat

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 rate cla

which tend to be single customers on a single large transformer. For the larger transformers, DOE’s evaluation at 50% is way too 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 Johnson; 

John Cymbalsky; Chris Bolduc; Freeman, Jeremiah; Emily Marchetti; Zhimei Luo; Puesh Kumar; Alex Hofmann; Andrew Delaski; ArSmith; Carlos Gaytan; Caskey, John; Charlie Drexler; Charlie Stevens; Chris Brown; Clark Silcox; Creevy, Jim; Daniel Young; David Fernstrom, Gary; Greg Coulter; Greg Rosenquist; Hirsch, Bruce R; James Lass; Jerry Hodge; Jerry Schoen; Jim Raba; Joanna Maue

Mahesh P. Sampat; Matthew Nardotti; Maxine Savitz; Meg Waltner; Michael Hyland; Michael Rivest; Millure, Dave; Pam Costello; PRick Anderson; Rob Greeson; Robert van Buskirk; Robin Roy; Ryan, Paul; Scott Beck; Simmons, Chuck; Steve Nadel; Steve Rosens
Petrosino; Tim Ballo; Tom Eckman; Wes 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 loading. I 

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 PG&E Lo

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 the typ

of 2 times the average. If all of the meters are seeing the same peak then the transformer carries more than rated load a

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 200% of 

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 is typica

reason for the excellent thermal ridethrough. The winding over oil time constant is faster but the net result is a tremendo

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 loading cap

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 Coffey; C

Jennifer Tiedeman; John Cymbalsky; Chris Bolduc; Freeman, Jeremiah; Emily Marchetti; Zhimei Luo; Puesh Kumar; Alex Hofmann; Bob Saint; Bob Smith; Carlos Gaytan; Caskey, John; Charlie Drexler; Charlie Stevens; Chris Brown; Clark Silcox; Creevy, Jim; DaniePeterson; Gary Fernstrom; Greg Coulter; Greg Rosenquist; Hirsch, Bruce R; James Lass; Jerry Hodge; Jerry Schoen; Jim Raba; Joa
Winder; Mahesh P. Sampat; Matthew Nardotti; Maxine Savitz; Meg Waltner; Michael Hyland; Michael Rivest; Millure, Dave; Pam Co

Raymond; Rick Anderson; Rob Greeson; Robert van Buskirk; Robin Roy; Ryan, Paul; Scott Beck; Simmons, Chuck; Steve Nadel; StThomas Petrosino; Tim Ballo; Tom Eckman; Wes 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 unreaso"can" possibilities are not relevant when actual experience is reported. PG&E peak loads are as reported. See below. Mo

value reliability very highly, prudence would obviate against planning to operate daily peaks at 133% of nameplate ratin

growth would likely necessitate frequent replacement in addition to the heightened 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 load on th

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 nameplate if th

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% * 0.51/0

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 such as dur

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 we can e

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

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 5:27 PM To: Phil Hopkinson Cc: Robert Berman; Corkran, Jerry L; Dan Mulkey; Aris Marantan; Katie Coughlin; Richard Parker; Brenda Edwards; Brian Coffey; C

Jennifer Tiedeman; John Cymbalsky; Chris Bolduc; Freeman, Jeremiah; Emily Marchetti; Zhimei Luo; Puesh Kumar; Alex Hofmann; Bob Saint; Bob Smith; Carlos Gaytan; Caskey, John; Charlie Drexler; Charlie Stevens; Chris Brown; Clark Silcox; Creevy, Jim; Danie
Peterson; Gary Fernstrom; Greg Coulter; Greg Rosenquist; Hirsch, Bruce R; James Lass; Jerry Hodge; Jerry Schoen; Jim Raba; Joa

Winder; Mahesh P. Sampat; Matthew Nardotti; Maxine Savitz; Meg Waltner; Michael Hyland; Michael Rivest; Millure, Dave; Pam Co

Raymond; Rick Anderson; Rob Greeson; Robert van Buskirk; Robin Roy; Ryan, Paul; Scott Beck; Simmons, Chuck; Steve Nadel; St

Thomas Petrosino; Tim Ballo; Tom Eckman; 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 boost telectric, for example, regardless of what they want or how much they want it. That's why Dan reports the annual average 

day load at 70%. I suspect that his guidance is to make the average load of the transformer on the peak day equal to 70% 

That would make sense as opposed to larger, historical oversizing factors, and would also lower transformer purchase coDan does, indeed, buy a very large number of 15 kVa transformers for his E1 rate class (not load class). This is for residmountainous areas. PG&E buys so many in large part because the casualty rate due to lightening is quite high. 

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 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% load fac

is the average load for that meter divided by the maximum load for that meter. Since all meters of the same class are averaged it 

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 average lo

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 remaining w

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 sizing policy 

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 Johnson; DJohn Cymbalsky; Chris Bolduc; Freeman, Jeremiah; Emily Marchetti; Zhimei Luo; Puesh Kumar; Alex Hofmann; Andrew Delaski; Ar

Smith; Carlos Gaytan; Caskey, John; Charlie Drexler; Charlie Stevens; Chris Brown; Clark Silcox; Creevy, Jim; Daniel Young; David Fernstrom; Greg Coulter; Greg Rosenquist; Hirsch, Bruce R; James Lass; Jerry Hodge; Jerry Schoen; Jim Raba; Joanna Mauer; Joh

P. Sampat; Matthew Nardotti; Maxine Savitz; Meg Waltner; Michael Hyland; Michael Rivest; Millure, Dave; Pam Costello; Phil Harte

Anderson; Rob Greeson; Robert Berman; Robert van Buskirk; Robin Roy; Ryan, Paul; Scott Beck; Simmons, Chuck; Steve Nadel; S

Johnstone; Thomas Petrosino; Tim Ballo; Tom 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 reported 

with 38% implied load factor PG&E filed in it's 2007 rate case (A=$7.268, B=$1.063). These results are not inconsistendistribution of loads used by LBNL. 

Regards,Robert A. Berman, Principal

Berman Economicswww.BermanEconomics.com
1915 Grand Court

Vienna, VA 22182

703‐281‐0490

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 transformers at a t

rating is very factual and the most accurate explanation I have heard about how the utilities load their new transformers. We hav

Grid”. This appears to be an example of a smart customer using the latest technology to lead the way on efficient use of new tran

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

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

industry. This is expected to result in load levels much higher than the 25% to 40% loads used by the DOE to calculate the pay ba

considered. The key question is what loading will be used on new transformers to be installed and not what loading exists on som

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 new trans

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

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

using a higher load factor in the DOE payback calculations? Based on the 70% load factor targeted by PG&E for 6 million custome

study payback results are not accurate and that they should be revised to some load factor that reflects the latest technology tha

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 loadingPhil: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 available on ou

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

displayed on an hourly basis for all 8760 hours in a year. Multiple years of data are available on the public website. The attach

extract of the data for 2006. The rate classes are defined in the second attachment.

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

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 most often a

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 within the ca

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 transform12. A given transformer can be placed into service for a wide variety of loads. For instance, the same 25 kVA single‐phase pad‐mount 

everything from a single signal light, to a single isolated residential customer, to fifteen or so residential customers in a subdivisio

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 ratepayers.

I hope that this explanation helps.Best regards,Dan MulkeySr Consulting Electrical EngineerDHM3@PGE.COM415‐973‐4699 office
415‐264‐9260 cell

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