Megger Testing of Transformers Effective TBD



Effective Date: TBDPrepared by:Jerry Wayne Date: ____________________Reviewed by: ___________________________________________________ Date: ____________________Approved by: ___________________________________________________ Date: ____________________Required review frequency: TBDTable of Contents TOC \h \z \t "Heading 1,1,Heading 2,2,Attachment,3" 1.Purpose and Scope PAGEREF _Toc283794507 \h 22.Acceptance Criteria PAGEREF _Toc283794508 \h 23.Special Tools and Materials PAGEREF _Toc283794509 \h 23.1Tools PAGEREF _Toc283794510 \h 23.2Materials PAGEREF _Toc283794511 \h 24.Precautions, Limitations, and Notes PAGEREF _Toc283794512 \h 24.1Precautions PAGEREF _Toc283794513 \h 24.2Limitations PAGEREF _Toc283794514 \h 24.3Notes PAGEREF _Toc283794515 \h 25.Prerequisites PAGEREF _Toc283794516 \h 25.1Planner PAGEREF _Toc283794517 \h 25.2Electricians PAGEREF _Toc283794518 \h 26.Definitions and Acronyms PAGEREF _Toc283794519 \h 27.Instructions PAGEREF _Toc283794520 \h 27.1Terminated Transformer Setup PAGEREF _Toc283794521 \h 27.2Terminated Primary Winding Insulation Test PAGEREF _Toc283794522 \h 27.3Terminated Secondary Winding Insulation Test PAGEREF _Toc283794523 \h 27.4Terminated Transformer Restoration PAGEREF _Toc283794524 \h 27.5Unterminated Transformer Setup PAGEREF _Toc283794525 \h 27.6Unterminated Primary Winding Insulation Test PAGEREF _Toc283794526 \h 27.7Unterminated Secondary Winding Insulation Test PAGEREF _Toc283794527 \h 27.8Unterminated Transformer Restoration PAGEREF _Toc283794528 \h 28.References PAGEREF _Toc283794529 \h 28.1Development PAGEREF _Toc283794530 \h 28.2Performance PAGEREF _Toc283794531 \h 29.Attachments PAGEREF _Toc283794532 \h 2Attachment A:Signoff/Data Sheet PAGEREF _Toc283794533 \h 2Attachment B:Verification Sheet PAGEREF _Toc283794534 \h 2List of Figures TOC \h \z \c "Figure" Figure 1: Transformer Jumpers PAGEREF _Toc283732268 \h 2Figure 2: Transformer Jumpers PAGEREF _Toc283732269 \h 2List of Tables TOC \h \z \c "Table" Table 1: Signature Box PAGEREF _Toc283732270 \h 2Table 2: Test Voltages PAGEREF _Toc283732271 \h 2Table 3: Torque Value Chart PAGEREF _Toc283732272 \h 2ReviewsWriter 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 PositionDate<type name of program owner><type title, organization><m/d/yy>Gwen HolladayTechnical Writer2/1/11Stakeholder ReviewName PositionDate<type name of organization manager><type title, organization><x/x/xx><type name of reviewer><type title, organization><x/x/xx>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.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.Special Tools and MaterialsUse the following special tools and materials to perform this procedure.ToolsThe following special tools are required:MeggerTorque WrenchMaterialsThe following materials are required:Statoascope (hot stick, as required)Ground stick (as required)Ground straps/jumpersClass II Rrubber insulated gloves (600 V or greater) with leather protectorsFire retardant coverallsVoltmeterPrecautions, Limitations, and NotesBefore performing the procedure, ensure you understand the following precautions, limitations, and notes.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.LimitationsNoneNotesThe 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 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.PrerequisitesThe following prerequisites must be met before performing this procedure.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)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 REF _Ref283703090 \h 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 NameSign NameInitialsRACF IDTable 1: Signature BoxEnter the following information on REF _Ref283788746 \r \h Attachment A: REF _Ref283788753 \h Signoff/Data Sheet in Section 5.2:M&TE numbers with Calibration Due DateDefinitions and AcronymsIAW - in accordance withKV - Live-Dead-Live (L-D-L)InstructionsThe procedures below contain instructions for the following tasks:Terminated Transformer Setup Terminated Primary Winding Insulation TestTerminated Secondary Winding Insulation TestTerminated Transformer RestorationUnterminated Transformer SetupUnterminated Primary Winding Insulation TestUnterminated Secondary Winding Insulation TestUnterminated Transformer RestorationTerminated Transformer SetupVerify unit, equipment tag number, and LOTOV. Walk clearance down. Know your boundaries.Ensure equipment is de-energized by electrical measurement. Use L-D-L method.Disconnect ground connections on neutral or center tap. Record on Attachment B: REF _Ref283733684 \h Verification Sheet (Attachment B).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.Disconnect ground resistors from circuit. Document and verify on Attachment B: REF _Ref283733684 \h Verification Sheet (Attachment B)).Remove potential transformer fuses. Document and verify on Attachment B: REF _Ref283733684 \h Verification Sheet (Attachment B).Transformer may be safety grounded under LOTOV clearance. Removing safety grounds for test may require changes in the LOTOV.Have operations remove safety grounds, if required.Measure for continuity between phases on primary side and secondary side of transformer. Ensure there is no continuity to ground.Install temporary jumpers from phase to phase on primary side, and on secondary side of transformer. Refer to REF _Ref283623263 \h Figure 1: Transformer Jumpers for typical transformer installation.Install temporary grounding jumpers on both primary and secondary to transformer frame (ground), connecting to jumpers installed in Step 8 above. Figure 1: Transformer JumpersBus VoltageTest Voltage DC4805002500250041605000690050001380010000Table 2: Test VoltagesTerminated Primary Winding Insulation TestRemove temporary grounding jumper from primary windings, leaving temporary phase jumpers in place.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.Megger primary winding phases for approximately one minute at voltage given above in REF _Ref283731926 \h Table 2: Test Voltages. Record reading on REF _Ref283733488 \r \h Attachment A: REF _Ref283733531 \h Signoff/Data Sheet.Re-install temporary grounding jumper on windings tested to discharge windings and ground them.Terminated Secondary Winding Insulation TestRemove temporary grounding jumper from secondary windings, leaving temporary phase jumpers in place.Megger secondary winding phases for approximately one minute at voltage given above in REF _Ref283731926 \h Table 2: Test Voltages. Record reading on REF _Ref283733488 \r \h Attachment A: REF _Ref283789027 \h Signoff/Data Sheet PAGEREF _Ref283789197 \h 2.Re-install temporary grounding jumper on windings tested to discharge windings and ground them.Terminated Transformer RestorationTransformer 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.If you removed safety ground was removed in Sec 7.1 Step 6, have operations re-install safety grounds. Document on Attachment A: REF _Ref283734026 \h Signoff/Data Sheet (Attachment A).Connect neutral or center tap ground connections. Torque connections IAW REF _Ref283717174 \h Table 3: Torque Value Chart. Document torque on Attachment A: REF _Ref283734026 \h Signoff/Data Sheet (Attachment A) and record re-connections on Attachment B: REF _Ref283733684 \h Verification Sheet (Attachment B).Install ground resistors. Torque connections IAW REF _Ref283717174 \h Table 3: Torque Value Chart. Document torque on Attachment A: REF _Ref283734026 \h Signoff/Data Sheet (Attachment A), and record re-connections on Attachment B: REF _Ref283733684 \h Verification Sheet (Attachment B).Install potential transformer fuses. Document and verify on Attachment B: REF _Ref283733684 \h Verification Sheet (Attachment B).Remove all test leads, temporary phase jumpers, and temporary grounding jumpers installed in this procedure. Document and verify on Attachment B: REF _Ref283733684 \h Verification Sheet (Attachment B).Unterminated Transformer SetupThe 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.Perform continuity checks between all phases of the transformer on primary side, and secondary side.Install temporary phase jumpers from phase to phase on both high side, and low side. See REF _Ref283623263 \h Figure 2: Transformer Jumpers for typical transformer installation.Install temporary grounding jumpers to transformer frame, connecting to jumpers installed in Section 7.5 Step 2.Figure 2: Transformer JumpersUnterminated Primary Winding Insulation TestRemove temporary grounding jumper from primary windings, leaving temporary phase jumpers in place.Megger testing will result in readings that include all parallel resistance paths of 3 three phases tested.Megger primary winding phases for approximately one minute at voltage given above in REF _Ref283731926 \h Table 2: Test Voltages. Record reading on Attachment A: REF _Ref283734026 \h Signoff/Data Sheet (Attachment A).Reinstall temporary grounding jumper on windings tested to discharge and re-ground windings.Unterminated Secondary Winding Insulation TestRemove temporary grounding jumper from secondary windings, leaving temporary phase jumpers in place.Megger secondary winding phases for approximately one minute at voltage given above in REF _Ref283731926 \h Table 2: Test Voltages. Record reading on Attachment A: REF _Ref283734026 \h Signoff/Data Sheet (Attachment A).Reinstall temporary grounding jumper on winding tested to discharge and reground windings.Unterminated Transformer RestorationRemove all test leads, temporary phase jumpers and temporary grounding jumpers installed in this procedure. Document on Attachment A: REF _Ref283734026 \h Signoff/Data Sheet (Attachment A).ReferencesDevelopment references are documents used to develop the procedure. Performance references are documents referenced within the procedure.8.1 DevelopmentMSE-G0-6201 Megger Testing of Transformers (from Comanche Peak NPP)8.2 PerformanceGeneration Safety HandbookLUM-FFA-REL-0014 Standard of Human Performance ImprovementAttachmentsAttachment A: REF _Ref283733927 \h Signoff/Data Sheet (Attachment A)Attachment B: REF _Ref283733849 \h Verification Sheet (Attachment B)Bolt Material Torque in Foot / Pounds for Bolt Size? - 205/16 - 183/8 - 16? - 135/8 - 11Silicone Bronze510154055Stainless Steel3.57133060Aluminum---2540All Other Material3.57133540Torque tolerance is plus or minus 10%.Connections utilizing hardware smaller than ? 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 ChartSignoff/Data Sheet5.1PlannerWork Order Number: __________________________Component Tag Number: ______________________Rated Voltage _______________ (Primary)___________________ (Secondary)Test Voltage _________________ (Primary)___________________ (Secondary)5.2ElectriciansM&TE NumberCalibration Due Date7.2Terminated Primary Winding Insulation TestN/A _____7.2.2Primary Phase ConnectionInsulation Resistance Reading 3 Phases to Ground MegohmsAcceptance Criteria: Equal to or greater than one megohm per KV of rated primary voltage plus one megohm, or as specified on Work Order.Signoff/Data Sheet7.3Terminated Secondary Winding Insulation TestN/A _____7.3.2Secondary Phase ConnectionInsulation Resistance Reading 3 Phases to Ground MegohmsAcceptance Criteria: Equal to or greater than one megohm per KV of rated primary voltage plus one megohm, or as specified on Work Order.7.4Terminated Transformer RestorationN/A _____7.4.1__________/___________________ Safety Grounds reinstalled, if applicable.7.4.2 / 7.4.3Component IDTorque Values Ft/Lbs Ft/Lbs Ft/Lbs Ft/Lbs Ft/LbsAcceptance Criteria: Use REF _Ref283717190 \h Table 3: Torque Value Chart XE "Table 2\: Torque Value Chart" 7.4.5__________/____________________ All leads and temporary jumpers removed.Signoff/Data Sheet7.6Unterminated Primary Winding Insulation TestN/A _____7.6.2Primary Phase ConnectionInsulation Resistance Reading 3 Phases to Ground MegohmsAcceptance Criteria: Equal to or greater than one megohm per KV of rated primary voltage plus one megohm, or as specified on Work Order.7.7Unterminated Secondary Winding Insulation TestN/A _____7.7.2Secondary Phase ConnectionInsulation Resistance Reading 3 Phases to Ground MegohmsAcceptance Criteria: Equal to or greater than one megohm per KV of rated primary voltage plus one megohm, or as specified on Work Order.Signoff/Data Sheet7.8Unterminated Transformer RestorationN/A _____7.8.1__________/____________________ All leads and temporary jumpers removed.Remarks:______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________Test completed by: ______________________________________________________Date ______________________Data reviewed and approved by: _______________________________________Date ______________________Responsible Maintenance SupervisorVerification SheetUse this sheet to maintain plant configuration “as found” and “as left.”.Page _____ of ______Equipment / Module /Device Term / Wire Unique ID Term / Wire Unique IDAction Code Performer DateVerifier DateAction CodesDL = Determ Lead IF = Install JumperRD = Remove DeviceRO = Remove OldRC = Remove CardO = other(explain)RL = Reland Lead RJ = Remove Jumper ID = Install Device IN = Install New IC = Install CardOB = Open BreakerOV = Open ValveOS = Open SwitchRF = Remove Fuse IT = Install TubingCB = Close BreakerCV = Close valveCS = Close Switch IF = Install FuseRT = Remove TubingRemarks: ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________Revision HistoryRevision NumberApproval DateNameChangesR 0TBDJerry WayneInitial Draft ................
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