Proficiency Testing FINAL REPORT Transformer Heating Test ... · Proficiency Testing FINAL REPORT Transformer Heating Test ... IEC 61558-1. Due to the similarities in test ... temperature

© IFM Quality Services Pty Ltd Page 1

This report is only for the use of participating laboratories

Proficiency Testing FINAL REPORT Transformer Heating Test

50 HZ 16E32.2

August 2016

Proficiency Testing Provider Certificate Number 3189-02.

Program Coordinator: Ingrid Flemming IFM Quality Services Pty Ltd PO Box 877 Ingleburn NSW 2565 Australia Tel: +61 (0)2 9618 3311 Fax: +61 (0)2 9618 3355 Email: [email protected] Samples Dispatched: 1 July 2016 Results Due: 28 August 2016 Report Issued: 9 November 2016

We gratefully express our thanks to IECEE CTL WG2 for their support. In particular, thanks to Matej Žontar for his assistance.

mailto:[email protected]



Operational Summary

NUMBER OF ROUNDS AND FREQUENCY OF TESTING

Rounds are operated on an on-need basis. This is the third of 3 rounds operated in 2016.

APPLICABLE STANDARDS

IEC 61558-1.

Due to the similarities in test procedures, other product standards may be applicable, including: IEC 60335-

1; IEC 60598-1; IEC 61010-1; IEC 60065; IEC 60950-1, IEC 62368-1 and other standards requiring

temperature rise tests using change in winding resistance method.

SAMPLE MANUFACRURE AND ASSURANCE OF SAMPLE INTERGRITY

Participants received one transformer. The samples were sourced from a single commercial supplier’s

manufacturing batch. Prior to use in this program, each individual sample was screened by IFM’s Support

Division for damage and functionality. The winding resistances were measured for each sample, those

found to be outside the statistically acceptable range were removed from the pool of samples. A selection

of the remaining samples was sent to an ISO/IEC 17025 accredited contract testing laboratory to carry out

homogeneity tests. Samples met the required criteria for homogeneity.

METHOD OF DISPATCH

All samples were sent via express national/international courier.

ASSESSMENT PROCEDURE

Please refer to IFM’s Policies on the assessment of PTP results:

http://www.ifmqs.com.au/proficiency/references/QPL001-02_Assessment_of_Microbiological_PT_Results.pdf

Refer to the discussion for a description of the assessment procedure for relevant tests.

DISPUTE PROCEDURE

Participants wishing to dispute their assessment, or appeal an evaluation on other grounds should submit

their appeal in writing to the program coordinator.

Please refer to http://www.ifmqs.com.au/ifm_terms_and_conditions.htm for the detailed policy.

CONFIDENTIALITY

The identity of participants and any identifying information supplied by participants is treated as confidential.

Appropriate policies and procedures have been put into place to ensure this confidentiality is maintained.

Please refer to http://www.ifmqs.com.au/ifm_policy_on_confidentiality.htm for the detailed policy.

TEST INSTRUCTIONS

Instructions applicable to this testing round may be found at:

http://www.ifmqs.com.au/proficiency/instructions/16e32.2_Instructions.pdf

http://www.ifmqs.com.au/proficiency/references/QPL001-02_Assessment_of_Microbiological_PT_Results.pdf

http://www.ifmqs.com.au/ifm_terms_and_conditions.htm

http://www.ifmqs.com.au/ifm_policy_on_confidentiality.htm

http://www.ifmqs.com.au/proficiency/instructions/16e32.2_Instructions.pdf



Participation Summary

⇒ 97 organisations enrolled

⇒ 87 organisations participated

⇒ 118 sets of results were submitted

⇒ 3362 individual test results were received

⇒ 348 results were assessed

⇒ 3014 results were not assessed

⇒ 51 results were assessed as outliers

Enumerative Tests Assessment Criteria

• Temperature rise of the primary winding at 50 Hz.

• Temperature rise of the secondary 1 winding at 50 Hz

• Temperature rise of the secondary 2 winding at 50 Hz.

Robust statistics are applied in order to determine a Z score for

each result. Acceptable Z scores are |Z|<3. Whenever possible

non-numeric results are assessed by applying simple pass/fail

assessments without issue of Z scores.

To ensure 1 laboratory could not unfairly bias the statistics

whenever multiple participants from a single laboratory submit

results, only the first 2 participants’ results are included in the data

population to be statistically analyzed.

Variations to the normal assessment procedure will be detailed in the discussion.

Available Tests

INDIVIDUAL RESULTS

Should individual test results be required, these will be provided upon request.

CORRECTIVE ACTIONS

IFM follows up on corrective actions of laboratories for a period of 3 months. Details for the closure

of actions will be at :

http://www.ifmqs.com.au/proficiency/references/QPF086-01_Corrective_Action_Management_for_Electrical_PT.pdf

http://www.ifmqs.com.au/proficiency/references/QPF086-01_Corrective_Action_Management_for_Electrical_PT.pdf



Discussion

CALCULATED AND SUBMITTED TEMPERATURE RISES

Each participant’s reported temperature rise for the primary and secondary windings were plotted against a

calculated temperature rise based on the formula:

Where x = 234.5 for copper ∆t is the temperature rise R1 is the initial resistance, R2 is the final resistance t1 is the initial ambient temperature, t2 is the final ambient temperature

Most participant’s reported temperature rise was in agreement with the calculated rise for the primary and

secondary windings (Figure 1). Participants reporting a result >5K different to the value calculated by IFM

are required to explain why the results are different.

One laboratory used the equation Reported value= measured value– Ambient. The temperature rise

reported by this laboratory did not match that of the value calculated by IFM. It is unclear if this laboratory

is using a different method to determine temperature rise. This program was only for laboratories which

measure temperature rise using the change of resistance method.

NUMBER OF SIGNIFICANT FIGURES

It is a requirement of ISO17025 that laboratories know their measurement uncertainties and that they do

not report misleading results. Laboratories reporting results to more significant figures than is suitable for

their measurement uncertainty are reporting misleading results, the greater number of significant figures

implies greater confidence in the result precision. Similar to 16E32 and 16E32.1, some participants

reported results to 5 decimal places. It is unlikely that laboratories would have a measurement uncertainty

that would allow reporting this many significant figures. Appendix 1 of this report contains information that

laboratories may find useful when calculating their measurement uncertainty.

Members of working group 2 have recommended that laboratories should at most report results to 1

decimal place. However, this does not negate the need for laboratories to determine their measurement

uncertainty.

TEMPERATURE RISE SECONDARY 1 VS SECONDARY 2 WINDING

After investigating participant’s results it was found that their was a correlation between the secondary 1

temperature rise results and the secondary 2. This can be seen in Figure 2.

Standard applied (Figures 3-5), adjustment of the voltage, time taken to reach steady state as well as initial

and final; voltage, current to the temperature rises of the primary and secondary windings were compared

to temperature rise. No factor examined was found to affect the results of this round.

LOW RESISTANCES IN SECONDARY WINDINGS

The resistances of the secondary windings were measured reasonably consistently by participants at 0.2 -

0.3 ohm. However, the resistances of the primary windings were 2 orders of magnitude higher than this at

∆ = ( 2 − 1) 1 ( + 1) − ( 2 − 1)



10

20

30

40

50

60

70

20 25 30 35 40 45 50 55 60 65 70

Tem

pera

ture

Ris

e Se

cond

ary 2

(K)

Temperature Rise Secondary 1 (K)

16e32.2: Secondary Temperature 1 Rise vs Secondary Temperature 2 Rise

FIGURE 2

0

20

40

60

80

100

120

140

0 50 100 150

Subm

itted

tem

pera

ture

rise

(K)

Calculated temperature rise (K)

16E32.2: Submitted vs Calculated Temperature Rise

Primary winding

Secondary 1 winding

Secondary 2 winding

x=y

FIGURE 1

30 - 40 ohm. There are some implications to the choice of equipment with this variation. The relative

ability to accurately measure the lower resistances must be taken into account when considering the

precision with which the results are reported.

Further, when the measured resistances of the windings are small, attention must be paid to other variables

both in the temperature rise equation and the factors that might influence the resistance being measured,

particularly the connections of conductors to the windings and electronic influences. Please refer to the

discussion in Appendix 1.



0

2

4

6

8

10

12

14

16

35.43 38.43 41.43 44.43 47.43 50.43 53.43 56.43 59.43 more

Freq

uenc

y (pa

rticip

ants

)

Primary winding temperature rise (K)

16E38.2: Primary Winding: Temperature Rise by Standard

IEC60065

IEC60598

IEC60950

IEC60335

IEC60601

IEC61010

IEC61558

IEC62368

IEC60947

FIGURE 3

0

2

4

6

8

10

12

27.88 32.76 37.64 42.52 47.4 52.28 57.16 62.04 66.92 more

Freq

uenc

y (pa

rticip

ants

)

Secondary 1 winding temperature rise (K)

16E32.2: Secondary 1 Winding Temperature Rise by Standard

IEC60065

IEC60598

IEC60950

IEC60335

IEC60601

IEC61010

IEC61558

IEC62368

IEC60947

FIGURE 4

READING AND FOLLOWING INSTRUCTIONS GIVEN FOR TESTING

The instructions require an input voltage to be applied to the primary winding while a resistive load is

attached to both of the secondary outputs. Point 4 of the instructions states the test should be conducted at

50Hz. One of the participating laboratories tested their transformer at 40Hz. This participant reported

outlying results and consequently received fail assessments. It was also noted that a participant tested the

9 V winding when at point 9b in the instructions it specifies that the load must be placed between the

terminals marked 0 V and 12 V. While these laboratories may not have received outliers they are still

advised to perform corrective action to ensure that understanding customer instructions is part of their

contract review process.



0

2

4

6

8

10

12

14

30.15 34.53 38.91 43.28 47.66 52.04 56.41 60.79 65.17 more

Freq

uenc

y (pa

rticip

ants

)

Secondary 2 winding temperature rise (K)

16E32.2: Secondary 2 Winding Temperature Rise by Standard

IEC60065

IEC60598

IEC60950

IEC60335

IEC60601

IEC61010

IEC61558

IEC62368

IEC60947

FIGURE 5



16e32.2 Temp Rise Transformer 50HzQ20 Temp rise primary

(K)Number of Results Received 115Number of Results Analysed 115Quartile 1 44.4650Quartile 3 50.4670IQR 6.0020NIQR 4.4493Median 47.4300Acceptable High:Median + (3*NIQR) 60.7778Acceptable Low:Median - (3*NIQR) 34.0822Statistically Acceptable Range 26.6957

16e32.2 Temp Rise Transformer 50HzQ21a Temp rise secondary 1


Results

TEMPERATURE RISE 50HZ FOR PRIMARY AND SECONDARY WINDINGS

16e32.2 Temp Rise Transformer 50HzQ21b Temp rise secondary 2


0

5

10

15

20

25

30

35

35 38 41 44 47 50 53 56 59

Mor

e

Result (K)

Freq

uenc

y

16e32.2 Temp Rise Transformer 50HzQ20 Temp rise primary

Excluded

Included

0

5

10

15

20

25

30

35

28 33 38 43 47 52 57 62 67

Mor

e

Result (K)

Freq

uenc

y

16e32.2 Temp Rise Transformer 50HzQ21a Temp rise secondary 1

Excluded

Included

0

5

10

15

20

25

30

35

30 35 39 43 48 52 56 61 65

Mor

e

Result (K)

Freq

uenc

y

16e32.2 Temp Rise Transformer 50HzQ21b Temp rise secondary 2

Excluded

Included



Appendix 1

Estimating measurement uncertainty is a requirement of ISO17025. Laboratories should have their own

procedure in place to determine their measurement uncertainty. An explanation of how to determine

measurement uncertainty is outside of the scope of this report. Laboratories that have not calculated their

measurement uncertainty may find ISO/IEC Guide 98-3:2008 useful.

To aid laboratories in estimating their measurement uncertainty, IFM has calculated the change in

temperature rise of the primary and secondary windings with changes in the initial and final ambient

temperature and resistance. As base values IFM used the median values from participants reporting

results for 50 Hz. These values were R1 primary = 37.01, R2 primary = 43.95, R1 secondary1 = 0.26, R2 secondary1 =

0.311, t1 = 23 and t2 = 23.68. The temperature rise for the primary and secondary windings were then

calculated for these values. Each variable was then increased by the value indicated in Tables A.1 to A.6

and the absolute change in the temperature rise was calculated.

TABLE A.1

TABLE A.2

TABLE A.3

TABLE A.4

TABLE A.5

TABLE A.6

While IFM did not ask participants for their measurement uncertainty, it should be inferred by the number of

significant figures reported. As the majority of participants reported ambient temperature to 1 decimal

place, it should be possible to assume their measurement uncertainty for ambient temperature is between

approximately 0.9 and 0.1 °C. Assuming the measurement uncertainty of the ambient temperature is 0.1 °

C, there could be a 0.1 °C variation between the real ambient temperature and the measured ambient

temperature.

Based on tables A.5 and A.6 there could therefore be a difference of 0.2 °C (0.118+0.1) between the real

temperature rise and the measured temperature rise. This would mean that the majority of laboratories

should at most be reporting temperature rise to 1 decimal place. However, the above is based on

assumptions, simplified calculations of measurement uncertainty and only considers the uncertainty of the

ambient temperature. Laboratories need to ensure that they calculate their own measurement uncertainty

using a valid method, considering all variables.

Change in initial resistance of primary winding (Ohms) R1 primary + 1 R1 primary + 0.1 Change in temperature rise (K) 8.04 0.82

Change in final resistance of primary winding (Ohms) R2 primary +1 R2 primary +0.1

Change in temperature rise (K) 6.95 0.69

Change in initial resistance of secondary 1 winding (Ohms) R1 secondary + 0.001 R1 secondary + 0.0001 Change in temperature rise (K) 1.18 0.1184

Change in final resistance of secondary 1 winding (Ohms) R2 secondary + 0.01 R2 secondary + 0.001 Change in temperature rise (K) 0.99 0.099

Change in initial ambient temperature (°C) t1 + 1 t1 + 0.1 Change in temperature rise 1.187 0.118

Change in final ambient temperature (°C) t2 + 1 t2 + 0.1 Change in temperature rise 1 0.1



Even though an instrument may be calibrated to a high level of accuracy the measurements it makes may

not be as accurate as the calibration. For example a thermocouple probe may be calibrated to within 0.2 °

C. However, if there are warm and cool areas within a room and, depending on the manner of air flow and

other environmental influences, it may only be able to determine the true ambient temperature to within 2 °

C.

Some factors that may affect temperature determinations are:

• Hot and cold areas in a room

• Distance of the temperature measuring probe from the sample and / or possible influence of radiated

heat from the sample

• Sudden changes in temperature from air-conditioners/heaters or opening doors

Some factors that may affect resistance measurements

• Resistance of the probes

• Connection of the probes to the sample

• Sources of noise (e.g. EMF)

Figures A1 and A2 compare how the uncertainty in resistance and ambient temperature affect the

uncertainty in temperature rise for different winding resistances. From these charts it can be seen that;

• a 1% uncertainty in resistance leads to leads to an approximate 4 K uncertainty in temperature rise

0

1

2

3

4

5

6

0 0.2 0.4 0.6 0.8 1

Unc

erta

inty

in te

mpe

ratu

re ri

se (K

)

Winding resistance (ohm)

Uncertainty in temperature rise of a 50 K temperature rise for different winding resistances for a 1 K uncertainty in ambient

temperature

Uncertainty in R = 0.01



FIGURE A1



0

1

2

3

4

5

6

0 0.2 0.4 0.6 0.8 1

Unc

erta

inty

in te

mpe

ratu

re ri

se (K

)

Winding resistance (ohm)

Uncertainty in temperature rise of a 50 K temperature rise for different winding resistances for a 0.0001 ohm uncertainty in

resistance

Uncertainty in temperature = 1

Uncertainty in temperature = 0.5

Uncertainty in temperature = 0.1

FIGURE A2



�End of Report�

Lab Code Reason Withdrawn / Comment Due DateAction Alert

Heating Test - Transformers - 16e32.2 (201607)

Electrical Program Status Report

1 CBTL - Certification Body Testing Laboratory









Y Y10 10 Feb 2017CTF - Customer’s Testing Facility

O 7/11/2016 Part01: 2 results assessed as outlying







17 Private


19 Private



25 CTF - Customer’s Testing Facility


O 7/11/2016 Part01: 2 results assessed as outlyingO 7/11/2016 Part02: 2 results assessed as outlying



30 Private




Y Y35 10 Feb 2017CBTL - Certification Body Testing Laboratory

O 7/11/2016 Part01: 1 result assessed as outlyingO 7/11/2016 Part02: 2 results assessed as outlying



O 7/11/2016 Part02: 1 result assessed as outlyingO 7/11/2016 Part01: 1 result assessed as outlying



O 7/11/2016 Part01: 1 result assessed as outlying

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49 Private

Y Y50 10 Feb 2017Private







































78 Private

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83 Private


85 Private







90 Private

91 Private

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Program Results NOT submitted

99 Private



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103 Private







>> Report Indicator Columns and Action History Codes

- "Y" when a submitted result was determined to be an outlier requiring corrective action(s) or additional information is required to clarify a result. Action history will then follow.- "Y" when corrective or other action(s) have not been completed- Date by which corrective or other action(s) are required to be completed. This date is not set until the FINAL report has been issued.

X - Reminder sent to laboratoryC - Action Closed (Completed)F - Overdue action referred to IEC-EE

Action History Codes:

O - Action Opened by IFMN - Notification of action sent to laboratoryA - Acknowledgement received from laboratoryR - Response received from laboratory

Column:

Action

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Proficiency Testing FINAL REPORT Transformer Heating Test ... · Proficiency Testing FINAL REPORT Transformer Heating Test ... IEC 61558-1. Due to the similarities in test ... temperature