Page 1 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
Use: Reference
Effective Date: TBD
Prepared by: Jerry Wayne Date: ____________________
Reviewed by: ___________________________________________________ Date: ____________________
Approved by: ___________________________________________________ Date: ____________________
Required review frequency: TBD
Page 2 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
Use: Reference
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
Page 3 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
Use: Reference
Table 1: Signature Box..............................................................................................................................................................2
Table 2: Test Voltages...............................................................................................................................................................2
Table 3: Torque Value Chart..................................................................................................................................................2
Page 4 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
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ReviewsWriter completes this section and deletes from final version after approval. Review comments are stored in <type location where comments are stored.>.
< In the Name column, list the names of reviewers you plan to review your document.>
Internal ReviewName Position Date<type name of program owner>
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Gwen Holladay Technical Writer 2/1/11
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Page 5 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
Use: Reference
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
Page 6 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
Use: Reference
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
Page 7 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
Use: Reference
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
Page 8 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
Use: Reference
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.
Page 9 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
Use: Reference
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.
Page 10 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
Use: Reference
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.
Page 11 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
Use: Reference
[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.
Page 12 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
Use: Reference
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.
Page 13 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
Use: Reference
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
Page 14 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
Use: Reference
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.
Page 15 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
Use: Reference
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%.
Page 16 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
Use: Reference
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
Page 17 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
Use: Reference
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.
Page 18 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
Use: Reference
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
Acceptance Criteria: Equal to or greater than one megohm per KV of rated primary voltage plus one megohm, or as specified on Work Order.
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.
Page 19 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
Use: Reference
Attachment Cont'd: Signoff/Data Sheet
7.6 Unterminated Primary Winding Insulation Test N/A _____
7.6.2
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.
7.7 Unterminated Secondary Winding Insulation Test N/A _____
7.7.2
Secondary 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.
Page 20 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
Use: Reference
Attachment Cont'd: Signoff/Data Sheet
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 Page 21 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: ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Page 22 of 22
Subject: Megger Testing of Transformers
Revision Number and Date: R 0 Procedure No.: LUM-FFA-MNT-0020
Use: Reference
Revision HistoryRevision Number Approval Date Name ChangesR 0 TBD Jerry Wayne Initial Draft