Comments on the Navigant Engineering Analysis

1. Although it is fully understood that this committee is working to a very tight time line, it is 

suggested that we spend as much of the time prior to and if necessary during the Oct 12 and Oct 

13 meetings, ensuring that the Navigant analyses are correct. The committee cannot propose 

revised standards if the data that we are utilizing is flawed. It appears that many questions 

have been raised concerning the validity of the Navigant analysis since the initial report was 

issued in March of 2011. Until the committee’s transformer design specialists and utility 

engineering experts sign-off on the analysis (basis on which the committee will make our 

recommendation) it is difficult to propose or debate new efficiency standards. 

2. Most of the below items have been or most likely will be brought forward by the transformer 

design engineers and utility engineers on the committee, but some of the concerns related to 

the validity of the Navigant analysis are; 

a. Is the 50% load assumption correct? 

b. What was the basis for selecting the design lines? Do the Navigant selected design lines 

adequately represent of each of the actual market segments? 

c. Is 20 years a more realistic life expectancy for pole-type transformers? 

d. Does the OPS model include stray losses? 

e. Does the OPS model restrict material selections to only commercially available materials 

(for example-based on thicknesses and widths that are commercially available for 

insulating paper)? 

f. How did Navigant factor in transformer size restrictions in their analysis (pole-type 

weights, foot print limitations for network transformers, etc) 

3. Despite the comments in items #1 and #2 concerning the validity of the Navigant Engineering 

Analysis, the committee does need to travel along parallel paths (as we consider corrections to 

the Navigant analysis) due to the current deadlines. Therefore, using the Navigant data from 

their March 2011 report the attached table was constructed. This table is an effort to 

summarize the data as well as meet the objective established by the rule making committee at 

the Sept 15 and 16 meeting that any proposed transformer efficiency standard must be able to 

be cost effectively manufactured by utilizing multiple core steel materials. The attached table 

highlights the maximum CSL for each design line based on the Navigant analysis and the ability 

to produce the transformer core from conventional grain-oriented, domain-refined High B, or 

amorphous. The table suggests that there is not much room for efficiency tightening for the 

liquid-filled units, but some efficiency improvement may be possible for the medium voltage 

dry-type (and possibly the low voltage dry-type which is being handled by a separate 

committee). 
4.

Design

CSL-0

(current) CSL-1 CSL-2 CSL-3 CSL-4 CSL-5 CSL-6 CSL-7

1

50 kVA

1 phase

liquid

pad

Best optionM-3M-3 SA1 SA1 SA1 SA1 SA1

Alternatives

ZDMH M-2 M-5ZDMH M-2ZDMH M-2 M-3

2

25 kVA

1 phase

liquid

pole

Best option ZDMH ZDMH SA1 SA1 SA1 SA1

Alternatives

M-3

M-2

M-4

M-5

M-2

M-3

M-4

ZDMH

3

500 kVA

1 phase

liquid

Best option

ZDMH M-2 M-3ZDMH M-2SA1

ZDMH

SA1 SA1 SA1 SA1 SA1

Alternatives

SA1 M-4 M-5M-3

SA1 M-4

M-2

M-3

4

150 kVA

3 phase

liquid

Best option

ZDMH M-2 M-3ZDMH M-2 M-3SA1 SA1 SA1 SA1 SA1

AlternativesM-5

5

1,500 kVA

3 phase

liquid

Best option

ZDMH M-3 M-2ZDMH SA1 SA1 SA1 SA1 SA1

Alternatives

SA1 M-2 M-4SA1 M-2 M-3ZDMH
Design

CSL-0

(current) CSL-1 CSL-2 CSL-3 CSL-4 CSL-5 CSL-6 CSL-7

6

25 kVA

1 phase

dry

10kV BIL

Best option

M-3

M-4

M-6

M-4M-4 SA1 M-4SA1 M-4SA1 SA1

Alternatives

M-6

M-0H 

laser M-3

SA1 M-0H 

laser M-3

M-0H 

laser M-3

M-0H 

laser

7

75 kVA

3 phase

dry

10kV BIL

Best option

M-6M-6M-6M-6M-3

M-6

M-0H 

laser M-4

M-0H 

laser

SA1 M-3

SA1 SA1

Alternatives

M-12M-12M-3

M-4

M-3

M-4

M-4

8

300 kVA

3 phase

dry

10kV BIL

Best option

M-6

M-5

M-5M-5M-0H 

laser

SA1 SA1

Alternatives

M-6

M-3

M-4

M-3

M-0H 

laser

M-3

M-4

9

300 kVA

3 phase

dry

45kV BIL

Best option

M-5M-5M-0H 

laser

SA1 SA1 SA1

Alternatives

M-3

M-6

M-3

M-0H 

laser M-6

M-3

M-5

SA1

M-0H 

laser

10

1,500 

kVA

3 phase

dry

45kV BIL

Best optionM-5M-5 SA1 SA1 SA1 SA1

Alternatives

M-5

M-0H 

laser

M-0H 

laser M-3

11

300 kVA

3 phase

dry

45kV BIL

Best option

M-3

M-4

M-0H 

laser

M-0H 

laser M-3 M-4

SA1 M-0H 

laser

SA1 SA1 SA1

Alternatives SA1

M-3

M-4

12

1,500 

kVA

3 phase

dry

95kV BIL

Best option

M-5M-5

M-4

M-0H 

laser

M-0H 

laser

SA1

SA1 SA1 SA1 SA1

Alternatives

M-4

M-0H 

M-3M-4

M-3

M-0H 

laser
laser

M-3

SA1 M-5

13

2,000 

kVA

3 phase

dry

125kV 

BIL

Best option M-5 M-5 M-0H 

laser

SA1 SA1 SA1

Alternatives

M-4 M-4

M-3

M-0H 

laser

M-3

SA1

M-4

M-0H 

laser

4. The committee needs to determine the availability of permanently domain-refined high B 

material as a viable core steel selection for the wound core units.