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Subject: Megger Testing of Transformers

Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020

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Effective Date: TBD

Prepared by: Jerry Wayne Date: ____________________

Reviewed by: ___________________________________________________ Date: ____________________

Approved by: ___________________________________________________ Date: ____________________

Required review frequency: TBD

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Table of Contents1. Purpose and Scope........................................................................................................................................ 22. Acceptance Criteria...................................................................................................................................... 23. Special Tools and Materials....................................................................................................................... 2

3.1 Tools............................................................................................................................................................................. 23.2 Materials..................................................................................................................................................................... 2

4. Precautions, Limitations, and Notes.......................................................................................................24.1 Precautions................................................................................................................................................................24.2 Limitations.................................................................................................................................................................24.3 Notes.............................................................................................................................................................................2

5. Prerequisites.................................................................................................................................................. 25.1 Planner........................................................................................................................................................................ 25.2 Electricians................................................................................................................................................................ 2

6. Definitions and Acronyms.......................................................................................................................... 27. Instructions..................................................................................................................................................... 2

7.1 Terminated Transformer Setup.......................................................................................................................27.2 Terminated Primary Winding Insulation Test...........................................................................................27.3 Terminated Secondary Winding Insulation Test......................................................................................27.4 Terminated Transformer Restoration...........................................................................................................27.5 Unterminated Transformer Setup...................................................................................................................27.6 Unterminated Primary Winding Insulation Test......................................................................................27.7 Unterminated Secondary Winding Insulation Test.................................................................................27.8 Unterminated Transformer Restoration......................................................................................................2

8. References....................................................................................................................................................... 28.1 Development.............................................................................................................................................................28.2 Performance..............................................................................................................................................................2

9. Attachments.................................................................................................................................................... 2

Attachment A: Signoff/Data Sheet.....................................................................................................................................2Attachment B: Verification Sheet........................................................................................................................................2

List of FiguresFigure 1: Transformer Jumpers............................................................................................................................................2

Figure 2: Transformer Jumpers............................................................................................................................................2

List of Tables

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Table 1: Signature Box..............................................................................................................................................................2

Table 2: Test Voltages...............................................................................................................................................................2

Table 3: Torque Value Chart..................................................................................................................................................2

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Internal ReviewName Position Date<type name of program owner>

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Gwen Holladay Technical Writer 2/1/11

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1. Purpose and ScopeThe purpose of this procedure is to provide instructions for performing insulation resistance (megger) testing of transformers. This procedure provides minimum guidelines and acceptance criteria necessary to ensure meggering is performed in a safely and consistently manner.

2. Acceptance CriteriaThe following acceptance criteria must be met to complete the procedure.

The minimum acceptable value for insulation resistance (R min.) in megohms between primary to secondary and phase-to-ground should equal or exceed one of the following values:

R min. should be equal to or greater than one megohm per KV of rated voltage of transformer plus one megohm.

Tthe minimum value specified by equipment manufacturer, if different from above.

3. Special Tools and MaterialsUse the following special tools and materials to perform this procedure.

3.1 ToolsThe following special tools are required:

Megger Torque Wrench

3.2 MaterialsThe following materials are required:

Statoascope (hot stick, as required) Ground stick (as required) Ground straps/jumpers Class II Rrubber insulated gloves (600 V or greater) with leather protectors Fire retardant coveralls Voltmeter

DevDocs, 02/01/11,

In LUM-FFA-MNT-0016, these items were listed as Tools.

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4. Precautions, Limitations, and NotesBefore performing the procedure, ensure you understand the following precautions, limitations, and notes.

4.1 Precautions The following precautions shall be followed:

Do not perform insulation test in a flammable or explosive atmosphere. To ensure the safety of personnel and test accuracy, Gground test specimen to discharge

accumulated electrical charges for safety of personnel and for test accuracy. Apply ground for four times the length of time test was you performed the test.

Observe electrical precautions to prevent personnel injuries or component damage. Warn and keep other personnel away from equipment during insulation testing and

capacitance discharge. Establish barriers and flagging to prevent unauthorized entry when testing.

Wear Class II rubber gloves and fire retardant coveralls when meggering at 600 volts or greater, including when connecting and disconnecting meggering equipment.

Connect ground lead first, and then HV lead. Disconnect ground lead last. Ensure thatUse a good connection to earth ground is used for both meggering and discharge

of equipment under test. Warn and keep other personnel away from equipment during insulation testing and a

capacitance discharge. Utilize safety barriers and flagging when appropriate.

[4.2] LimitationsNone

4.2[4.3] NotesThe following information may be used while performing the procedure:

Do not record readings within the body of this procedure if you are meggering is being performed to obtain "Information Only" type data, as in case offor example if you are trouble shooting.

Do not record readings here if you are meggering is being performed as part of another approved procedure.

Read the analog megger on the scale that gives thegiving best resolution, and record. Use specific measurements rather than descriptions such as greater than or less than should not

DevDocs, 02/01/11,

Where?

DevDocs, 02/01/11,

Duplicate of 4th bullet point.

DevDocs, 02/01/11,

Is "good" specific enough?

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be used. Do not take Mmegger readings should not be taken while the pointer or display is pegged (unless on the highest available range), erratic, or in transit.

Record the actual value displayed value on the digital megger, except that the word "Infinity", "INF" or the infinity symbol should be used when the display shows the digit "1" in the first (left hand) position with the other positions blank.

Report discrepancies or unsatisfactory results to the Work Group Supervisor for follow-up actions. Document problems found in the "Remarks" section of work package.

5. PrerequisitesThe following prerequisites must be met before performing this procedure.

5.1 PlannerThe planner to must enter the following information on Attachment A: Signoff/Data Sheet:

Work Order No.: __________________________________ Component Tag No.: ______________________________ Unit No.: ____________________________________________ Serial No.: __________________________________________ Equipment Rated Voltages (Primary/Secondary) Megger Test Voltages (Primary/Secondary)

5.2 ElectriciansPersonnel performing this procedure shall review all instructions, precautions, notes, and safety requirements prior to performing this procedure.

Each personAfter using this procedure, is required to record their your name in the following Ssignature Bbox (see Table 1: Signature Box). If you do not have a RACF ID, is unavailable, include your the contact information of the individual.

Print name, sign name, and initials of the individuals performing this procedure in the table below.

Print Name Sign Name Initials RACF ID

DevDocs, 02/01/11,

Is this Attachment A?

DevDocs, 02/01/11,

unless the value displayed is "1" in the first (left-hand) position and the other positions are blank. In this case, record the value as "Infinity," "INF," or the infinity symbol.

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Print Name Sign Name Initials RACF ID

Table 1: Signature Box

Enter the following information on Attachment A: Signoff/Data Sheet in Section 5.2:

M&TE numbers with Calibration Due Date

6. Definitions and AcronymsIAW - in accordance with

KV -

Live-Dead-Live (L-D-L)

7. InstructionsThe procedures below contain instructions for the following tasks:

Terminated Transformer Setup Terminated Primary Winding Insulation Test Terminated Secondary Winding Insulation Test Terminated Transformer Restoration Unterminated Transformer Setup Unterminated Primary Winding Insulation Test Unterminated Secondary Winding Insulation Test Unterminated Transformer Restoration

7.1 Terminated Transformer Setup

1. Verify unit, equipment tag number, and LOTOV. Walk clearance down. Know your boundaries.

2. Ensure equipment is de-energized by electrical measurement. Use L-D-L method.

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3. Disconnect ground connections on neutral or center tap. Record on Attachment B: Attachment B: Verification Sheet.

[Caution] The work group shall walk down both ends of any affected cable(s) to be sure they are connected or isolated at their source to prevent any arcing. Establish barriers at both ends, with signs warning all personnel in the immediate area before any testing is to be performed.

[4.] Disconnect ground resistors from circuit. Document and verify on Attachment B: Attachment B: Verification Sheet).

4.[5.] Remove potential transformer fuses. Document and verify on Attachment B: Attachment B: Verification Sheet.

Caution Transformer may be safety grounded under LOTOV clearance. Removing safety grounds for test may require changes in the LOTOV.

5.[6.] Have operations remove safety grounds, if required.

6.[7.] Measure for continuity between phases on primary side and secondary side of transformer. Ensure there is no continuity to ground.

[8.] Install temporary jumpers from phase to phase on primary side, and on secondary side of transformer. Refer to Figure 1: Transformer Jumpers for typical transformer installation.

7.[9.] Install temporary grounding jumpers on both primary and secondary to transformer frame (ground), connecting to jumpers installed in Step 8 above.

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Figure 1: Transformer Jumpers

Bus Voltage Test Voltage DC480 500

2500 2500

4160 5000

6900 5000

13800 10000

Table 2: Test Voltages

7.2 Terminated Primary Winding Insulation Test

1. Remove temporary grounding jumper from primary windings, leaving temporary phase jumpers in place.

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[Note 1] Megger testing will result in readings that include all parallel resistance paths of 3 three phases tested as well as any busswork or cabling connected.

2. Megger primary winding phases for approximately one minute at voltage given above in Table 2: Test Voltages. Record reading on Attachment A: Signoff/Data Sheet.

3. Re-install temporary grounding jumper on windings tested to discharge windings and ground them.

7.3 Terminated Secondary Winding Insulation Test

1. Remove temporary grounding jumper from secondary windings, leaving temporary phase jumpers in place.

[2.] Megger secondary winding phases for approximately one minute at voltage given above in Table 2: Test Voltages. Record reading on Attachment A: Signoff/Data Sheet 16.

2.[3.] Re-install temporary grounding jumper on windings tested to discharge windings and ground them.

7.4 Terminated Transformer Restoration

Caution Transformer may be safely grounded under the LOTOV clearance. Removing safety grounds for testing may require changes to the clearance in accordance with (IAW) the LOTOV procedure.

[1.] If you removed safety ground was removed in Sec 7.1 Step 6, have operations re-install safety grounds. Document on Attachment A: Attachment A: Signoff/Data Sheet.

3.[2.] Connect neutral or center tap ground connections. Torque connections IAW Table 3: Torque Value Chart. Document torque on Attachment A: Attachment A: Signoff/Data Sheet and record re-connections on Attachment B: Attachment B: Verification Sheet.

[3.] Install ground resistors. Torque connections IAW Table 3: Torque Value Chart. Document torque on Attachment A: Attachment A: Signoff/Data Sheet, and record re-connections on Attachment B: Attachment B: Verification Sheet.

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4. Install potential transformer fuses. Document and verify on Attachment B: Attachment B: Verification Sheet.

5. Remove all test leads, temporary phase jumpers, and temporary grounding jumpers installed in this procedure. Document and verify on Attachment B: Attachment B: Verification Sheet.

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7.5 Unterminated Transformer Setup

[Caution] The work group shall walk down both ends of any affected cable(s) to be sure they are connected or isolated at their sources to prevent any arcing. Establish Bbarriers are to be established at both ends, with warning signs attached to alert all people personnel in the area before any testing starts.

[1.] Perform continuity checks between all phases of the transformer on primary side, and secondary side.

[2.] Install temporary phase jumpers from phase to phase on both high side, and low side. See Figure 1: Transformer Jumpers for typical transformer installation.

[3.] Install temporary grounding jumpers to transformer frame, connecting to jumpers installed in Section 7.5 Step 2.

Figure 2: Transformer Jumpers

DevDocs, 02/01/11,

Would they have only one source, or multiple sources?

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7.6 Unterminated Primary Winding Insulation Test

1. Remove temporary grounding jumper from primary windings, leaving temporary phase jumpers in place.

[Note 2] Megger testing will result in readings that include all parallel resistance paths of 3 three phases tested.

2. Megger primary winding phases for approximately one minute at voltage given above in Table 2: Test Voltages. Record reading on Attachment A: Attachment A: Signoff/Data Sheet.

3. Reinstall temporary grounding jumper on windings tested to discharge and re-ground windings.

7.7 Unterminated Secondary Winding Insulation Test

1. Remove temporary grounding jumper from secondary windings, leaving temporary phase jumpers in place.

2. Megger secondary winding phases for approximately one minute at voltage given above in Table 2: Test Voltages. Record reading on Attachment A: Attachment A: Signoff/Data Sheet.

3. Reinstall temporary grounding jumper on winding tested to discharge and reground windings.

7.8 Unterminated Transformer Restoration

1. Remove all test leads, temporary phase jumpers and temporary grounding jumpers installed in this procedure. Document on Attachment A: Attachment A: Signoff/Data Sheet.

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8. ReferencesDevelopment references are documents used to develop the procedure. Performance references are documents referenced within the procedure.

8.1 Development[[1]] MSE-G0-6201 Megger Testing of Transformers (from Comanche Peak NPP)

8.2 Performance[1] Generation Safety Handbook[2] LUM-FFA-REL-0014 Standard of Human Performance Improvement

9. Attachments[[1]] Attachment A: Signoff/Data Sheet (Attachment A)[[2]] Attachment B: Verification Sheet (Attachment B)

Bolt Material Torque in Foot / Pounds for Bolt Size

¼ - 20 5/16 - 18 3/8 - 16 ½ - 13 5/8 - 11

Silicone Bronze 5 10 15 40 55

Stainless Steel 3.5 7 13 30 60

Aluminum - - - 25 40

All Other Material 3.5 7 13 35 40

Torque tolerance is plus or minus 10%.

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Bolt Material Torque in Foot / Pounds for Bolt Size

Connections utilizing hardware smaller than ¼ inch shall be term tight. Terminations made by compressing a wire/cable strand with a bolt/screw shall be

term tight.

Table 3: Torque Value Chart

Attachment A: Signoff/Data Sheet5.1 Planner

Work Order Number: __________________________ Component Tag Number: ______________________ Rated Voltage _______________ (Primary) ___________________ (Secondary) Test Voltage _________________ (Primary) ___________________ (Secondary)

5.2 Electricians

M&TE Number Calibration Due Date

7.2 Terminated Primary Winding Insulation Test N/A _____

7.2.2

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Primary Phase Connection Insulation Resistance Reading 3 Phases to Ground Megohms

Acceptance Criteria: Equal to or greater than one megohm per KV of rated primary voltage plus one megohm, or as specified on Work Order.

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Attachment Cont'd: Signoff/Data Sheet

7.3 Terminated Secondary Winding Insulation Test N/A _____

7.3.2

Secondary Phase Connection Insulation Resistance Reading 3 Phases to Ground Megohms


7.4 Terminated Transformer Restoration N/A _____

7.4.1 __________/___________________ Safety Grounds reinstalled, if applicable.

7.4.2 / 7.4.3

Component ID Torque Values Ft/Lbs

Ft/Lbs

Ft/Lbs

Ft/Lbs

Ft/Lbs

Acceptance Criteria: Use Table 3: Torque Value Chart

7.4.5 __________/____________________ All leads and temporary jumpers removed.

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7.6 Unterminated Primary Winding Insulation Test N/A _____

7.6.2

Primary Phase Connection Insulation Resistance Reading 3 Phases to Ground Megohms


7.7 Unterminated Secondary Winding Insulation Test N/A _____

7.7.2

Secondary Phase Connection Insulation Resistance Reading 3 Phases to Ground Megohms


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7.8 Unterminated Transformer Restoration N/A _____

7.8.1 __________/____________________ All leads and temporary jumpers removed.

Remarks:

______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Test completed by: ______________________________________________________ Date ______________________

Data reviewed and approved by: _______________________________________ Date ______________________

Responsible Maintenance Supervisor

LUM-FFA-MNT-0020 Megger Testing of Transformers R0 of 22

Attachment B: Verification SheetUse this sheet to maintain plant configuration “as found” and “as left.”. Page _____ of ______Equipment / Module /Device

Term / Wire Unique ID

Term / Wire Unique ID

Action Code

Performer Date Verifier Date

Action CodesDL = Determ Lead IF = Install Jumper RD = Remove Device RO = Remove Old RC = Remove Card O = other

(explain)RL = Reland Lead RJ = Remove Jumper ID = Install Device IN = Install New IC = Install CardOB = Open Breaker OV = Open Valve OS = Open Switch RF = Remove Fuse IT = Install TubingCB = Close Breaker CV = Close valve CS = Close Switch IF = Install Fuse RT = Remove TubingRemarks: ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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Revision HistoryRevision Number Approval Date Name ChangesR 0 TBD Jerry Wayne Initial Draft

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