Dielectric Tests Subcommittee – Unapproved Meeting Minutes

March 20, 2013, Dolce,Munich, Germany

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11.11Dielectric Tests Subcommittee – Mike Franchek, Chair; Thang Hochanh, Vice-Chair; Dennis Marlow, Secretary

The Dielectric Tests Subcommittee (DISC) met on Wednesday, March 20 at 11:00 am with157persons in attendance. There were 61 of 107members, and 96guests present. Elevenof the returningguestsrequested membership andwill have their participation status reviewed prior to acceptance. Seven (7) were accepted as new members.Mike Franchek is welcomed as the new Chairreplacing long standing Loren Wagenaar.

11.11.1 Chair’s Remarks

  1. The Chair briefly reviewed highlights of the Administrative Subcommittee meeting held on Sunday afternoon. In order to remain an active member in the in the Sub-Committee, participants will need to have attended 1 meeting out of the last 2. Exceptions may be granted for special conditions. The other main points have already been discussed in the Main Committee meeting on Monday and were not repeated.
  2. The following meetings of the TC are:

a)Fall October 20-24, 2013 – St. Louis, MO – hosted by H-J Enterprises at Renaissance Grand Hotel $139 per night plus taxes

b)Spring March 23-27,2014 – Savannah GA – hosted by EFACEC

Additional meeting sites will be listed on the main committee website.

11.11.2 Quorum and Approval of Minutes

  1. The membership list was shown and a show of hands of committee members present showed that a quorum of members were in attendance at the start of the meeting.
  2. The minutes of the fall 2012 meeting in Milwaukee were approved without correction.

11.11.3. Working Group Reports

11.11.3.1 Working Group on External Dielectric Clearances, Eric Davis, Chair; Dennis Marlow, Secretary

The Working Group met on March 18, 2013 at 9:45 am with 35 people attending the meeting; seven members, one corresponding member, and 28 guests. A quorum was achieved. The membership list will be reviewed to include only those members who have attended at least one of the last 2 meetings.

Eduardo Garcia moved that the Fall 2011 meeting minutes be approved as written. Vinay Mehrotra seconded the motion. There was no discussion. The motion passed and the minutes were approved as printed.

David Wallace moved that the Spring 2012 meeting minutes be approved as written. Eduardo Garcia seconded the motion. There was no discussion. The motion passed and the minutes were approved as printed.

David Wallace moved that the Fall 2012 meeting minutes be approved as written. Eduardo Garcia seconded the motion. There was no discussion. The motion passed and the minutes were approved as printed.

The WG reviewed the proposed clearance table for 1.2 through 230 kV with the changes discussed at the last meeting. There were no comments on the revised table. It will be sent out to the Subcommittee for survey.

The WG discussed the minimum clearance between the top sheds of bushings. It was noted that the early bushings had a stud connection and typically had an inch or more of porcelain between the metal stud and the edge of the bushing shed. This is no longer true with the condenser style bushings.

It was also noted that no one had ever seen a flashover from porcelain to porcelain. Mike Franchek indicated that the critical stress on the metal top cap of a bushing is always higher than the shed to shed stress.

Dennis Marlow offered to contactBob Veitch who previously was involved with the existing table around 1980 in order to gain some history regarding the origins of this table..

After some discussion, the majority of the people in attendance felt that:

  • The metal to metal clearance is the critical clearance.
  • The minimum clearance between the top sheds of bushings should be removed from the table.

The WG reviewed the switching surge phase-to-ground clearances. We agreed to use the formula contained in IEEE 1313.2 and IEEE 1427 with a gap factor equal to 1.3. The majority of the people in attendance felt these clearances should be based on a 90% probability of withstand. These values will be calculated and distributed to the WG prior to the next meeting.

Meeting adjourned at 11:00 am

Respectfully submitted, Dennis Marlow

11.11.3.2 Task Force on Dielectric Frequency Response (DFR) – Ali Naderian, Chair; Poorvi Patel, Secretary.Monday, March 18th, 2013 – (3:15 -4:30PM)

The meeting was called to order by the chair at 3:15 PM. There were a total of 42 attendees; 13 members, 5 requested new membership and 24 new guests.

  1. Introduction of members and guests.
  2. The minutes of meeting from Fall 2012 meeting in Milwaukee could not be approved since there was no quorum.
  3. WG C57.161 under Dielectrics was assigned for DFR. The WG was approved by Transformers Administrative Committee. PAR has not been submitted and is waiting for approval of Admin Standard Committee. It is expected that The PAR will be approved by the Fall 2013 meeting in St. Louis MS.

4The approved scope and purpose of the DFR guide from the Milwaukee meeting was presented for new members..

  • Scope:This guide is applicable to the methods of Dielectric Frequency Response (DFR) of liquid immersed transformers. The guide includes recommendations for instrumentation, procedures for performing the tests and techniques for analyzing the data. This guide can be used in both field and factory applications.
  • Purpose:The purpose of this guide is to provide the user with information that will assist in performing Dielectric Frequency Response measurements and interpreting the results from these measurements.
  1. Within the given scope and purpose of the TF, the Table of content for the DFR Guide was discussed and revised but not approved since there was no quorum.
  1. The minutes of Fall 2012 meeting and the Table of contents will be circulated to the TF members by email before the Fall 2013 meeting.

7. The Revised Table of Contents:

1. Overview

1.1 Scope

1.2 Purpose

2. Definitions

3. DFR measurement overview

3.1 Use of DFR

3.2 DFR Moisture Application

3.3 Recommended DFR measurement test parameters

4. Making a DFR measurement

4.1 Test procedures

4.2 Test environment preparation

4.3 Test object preparation

4.4 Test connections

4.5 Test Specification

4.6 Test leads

4.7 Measurement methods

5. Test records

6. Measurement analysis, interpretation and report

6.1 Moisture estimation

6.1.1 Introduction

6.1.2 Modeling

6.1.3 Factors influencing moisture estimate

6.1.4 Report

6.2 Examples

Annex A (informative) DFR moisture estimate theory+ Other diagnostics

Annex B DFR Other Application

Annex C (informative) Bibliography

  1. Meeting was adjourned at 4.30 pm.

Respectfully submitted Poorvi Patel, Secretary

11.11.3.3 Working Group for Revision of the Distribution Impulse Test Guide C57.138,

Recommended Practice for Routine Impulse Test of Distribution Transformers;

John Crotty, Chair

WG did not meet .No report submitted

11.11.3.4 Working Group on Revision of Impulse Tests – Pierre Riffon, Chair; Peter Heinzig, Vice-Chair

The WG met on March 19, 2013, from 09:30 am to 10:45 am. Sixteen members (16) members and forty-three (43) guests attended the meeting. Six (6) guests requested membership. The meeting was chaired by Pierre Riffon, chair of the WG.

Required quorum was met.

The agenda has been reviewed and approved as written.

Minutes of the Milwaukee meeting were approved as written.

The first technical subject on the agenda was the review of the proposal regarding revision of clause 5.10.7.2 of IEEE C57.12.00 "Switching impulse tests". The proposal was surveyed within the WG and Dielectric Tests SC and the responses reviewed at the Milwaukee meeting. This proposal did not receive more comments at the Munich meeting and will be sent to Steve Snyder for inclusion in the upcoming draft of C57.12.00 for ballot.

The second technical item of business was related to the Class I and Class II definition regarding impulse testing. As surveyed within the WG and Dielectric Tests SC, the proposal of having transformers with high-voltage windings 69 kV and maximum nameplate rating of 15,000 kVA or above for three-phase transformers or 10,000 kVA or above for single-phase transformers to be routine impulse tested as actual Class II transformers has been largely accepted (90% approval).

Instead of changing piece by piece the applicable parts of C57.12.00 and C57.12.90 for conforming to the decision taken, it will be much more practical and simple to change the definition of Class I and Class II transformers. Nevertheless, this decision is beyond the scope of the WG as well as the Dielectric Tests SC. Some of the tests required for Class I and Class II transformers are not Dielectric Tests and are under the responsibility of PSC. The WG is asking the Dielectric Subcommittee Chair to coordinate this matter with PCS. If PCS disagree with the proposed change of the definition, then applicable parts regarding impulse testing of C57.12.00 and C57.12.90 will be changed piece by piece. This solution is not recommended since the standard will become extremely complex and perhaps confusing.

As old business, the order of impulse tests is not defined in C57.12.90. The actual clause 10.1.5.1 of C57.12.90 lets the choice to the manufacturer of doing either the lightning impulse tests or the switching impulse test as the first impulse test series. The new IEC draft (14/745/FDIS) specifies a mandatory order (which can be changed upon agreement), the lightning impulse test being required first and followed by the switching impulse test series. After discussion, a majority of the people present at the meeting see some merit of such testing order if preferred, but not mandatory. A proposal will be circulated for survey within the WG and the Dielectric Tests SC prior to the next meeting.

The meeting adjourned at 10:30 am on March 19, 2013.

Pierre Riffon P. Eng.

WG Chair

March 19, 2013

11.11.3.5 Working Group on Revision of Low Frequency Tests; BertrandPoulin,Chair; Bill Griesacker, SecretaryMarch 19, 2013, 1:45 pmAmmersee I

The meeting was called to order and introductions were conducted.

A quorum was not immediately present; the meeting proceeded as an informal discussion.

The Chair Thang Hochanh for the Task Force on PD in Bushings and PTs/CTs gave his report. A PAR has been approved for this TF to generate a document PC57.160. The new WG has 4 years to generate and ballot this new document. The document is already progressing well and a first draft is expected next year.

Old Business:

There was an extension of the Class 1 / Class 2 power transformer discussion as previously discussed in the WG on impulse test revisions. The recommendation is to take this issue up at the Dielectric Test Sub Committee meeting with regard to changing the definitions of Class 1 & Class 2 power transformers. The previously conducted survey in this WG is strongly in support of this change.

The previously requested survey of the Tap Changer position during induced testing will be conducted in the coming weeks.

A quorum was established with 19 of 37 members at 2:00 PM. Following this, the meeting minutes from Fall 2012 in Milwaukee were reviewed and approved without objection.

The T/C position during induced testing had additional discussion. Some members present indicated that they conducted induced testing with the Load Tap Changer set in the maximum position.

New Business:

There was a query about the allowable frequency for the applied test. The reason for this request is that for resonant test set testing, it is typically easier with a variable frequency power supply to tune the frequency to the circuit than it is to tune the circuit to the frequency. The standard was consulted and the maximum permitted frequency was confirmed at 500 Hz. This value was suitable so discussion was suspended.

There were no objections to adjourning the meeting at 2:15PM.

Checking the membership rosters there was a total of 20 members present.

Respectfully submitted,

Dan Sauer

3/19/13

11.11.4Liaison Reports

11.11.4.1High Voltage Test Techniques (HVTT), IEEE Standard 4 - Arthur Molden

The newly revised edition of IEEE Standard 4, “High Voltage Testing Techniques” has completed the balloting process and was approved by the IEEE-SA Standards Board on March 6th. The new revision will be published shortly, and will replace IEEE Standard 4, 1995.

Report prepared by Jeff Britton, Secretary, IEEE HVTT Subcommittee

11.11.5 Old Business

11.11.5.1Comments from C57.12.00 Ballot on Dielectric Test Tables Table 5

Phil Hopkinsonagain reported that Columns 12 and 13 of Table 5 were incorrectly labeled as “Impedance grounded wye.” Column 12 should be labeled “Grounded wye” and Column 13 “Impedance grounded wye.”

At the previous meeting, Jin Sim pointed out that the applied test values in Table 5, Column 4 do not match the Neutral BIL values listed in Table 5, Column 13 for 36-kV, 48-kV and 73-kVwhen compared to the values contained in C57.12.00-2006, Table 6.

Col 1 (kV)Col 13(kV Crest) Col 13 (Proposed)

36125150

48150200

73200250

The following comments were also received from Steve Antosz following the meeting and are included in these minutes.

“I call your attention to columns 4 and 12 in Table 5. (I recognize that the heading of column 12 should be “grounded wye”. Phil already recognized this transcription error.)

Basically my question is, “What is the Applied Test level for a grounded wye winding with a neutral greater than 110 kV BIL?” The 2010 Table 5 doesn’t have this anymore, since it assumes that all neutrals are 110 kV BIL, which would get a 34 kV Applied Test. Well, I rarely see 110 BIL grounded wye neutrals on large and medium transformers. Usually are 150 BIL, and sometimes higher.

I feel that the table should be revised somehow to designate higher applied test levels for ‘grounded wye windings with neutrals greater than 110 BIL’. The 2006 tables were OK in this regard.”

There are several corrections and modifications that need to be made to this table. These must be made and approved by the SC prior to the next meeting so that they can included in the next revision of C57.12.00. If not possible then as agreed at the prior meeting, the WG on the Continuous Revision of C57.12.00 shall immediately prepare a Corrigenda correcting Table 5

Bertrand Poulin also indicated that for 550 kV classtransformer that there actually exists both 500 and 550 kV class transformers. Thus the enhanced 550 kV and 1 hour 475 kV levels for induced tests are not consistent with respect to the system operating voltages.

Phil Hopkinson reported that for repair of old transformers built to previous versions of C57.12.00 that the values in those standards should be used for test references with the appropriate factor for rebuilt transformers.

11.11.5.2Class I/Class II Classification for Transformers

There is adequate response now for this issue to be resolved by the DI Test SC. Proposed wording will be prepared and circulated to the membership prior to the next meeting. The PCS SC will also need to approve the proposal for some non dielectric issues.

11.11.6 New Business

11.11.6.1 C57.127 New Working Group on the Revision of Partial Discharge Acoustic Detection starting next meeting – Jack Harley – Detlev Gross Co-Chairs, .

A new Working Group will revise C57.127 Guide for the Detection and Location of Acoustic Emissions from Partial Discharges in Oil-Immersed Power Transformers and Reactors. The first meeting of the WG will be in St. Louis at the fall TC meeting.

The WG will address technology changes and diagnostic method improvements that have occurred since the last guide was published in 2007. The revision date will be 2018

Jack Harley and Detlev Gross are Co-chairs of the WG

. 11.11.7 Meeting adjourned 12.15 PM. Minutesrespectfully submitted by Dennis Marlow

REVISED OCT11,2013..ADDED LIASON REPORT 11.11.4.1

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