SOLO RUN TEST AND MEGGER TEST FOR MV AND LV MOTORS

This article is related to Megger test and following preparations to be done before megger test.

  • All permanent materials (including fabricated and pre-fabricated supports), consumables, construction area and resources shall be prepared and checked prior to installation works.
  • Ensure that all Electrical Equipment and materials, which would suffer damage or deterioration from exposure to the elements has been properly stored indoor, off the ground in suitable warehousing.
  • Special tools shall bear a valid calibration certificates traceable to a national standard indicating calibration validity and periodically (maximum of six months) checked by a third party laboratory testing facility.
  • Electrical materials shall conform to all applicable requirements, standard, and specifications prior to release to be used as part of the work. Refer to Schedule “Q” Att. IV Para 7.1.
  • Review all references such as the latest approved for construction drawings, layout, and Technical Scope of Work.
  • Ensure the manpower, equipment and other resources are prepared prior to start of the activities.

SOLO RUN TEST or Megger test FOR MV AND LV MOTORS

  • All permanent materials (including fabricated and pre-fabricated supports), consumables, construction area and resources shall be prepared and checked prior to installation works.
  • Ensure that all Electrical Equipment and materials, which would suffer damage or deterioration from exposure to the elements has been properly stored indoor, off the ground in suitable warehousing.
  • Special tools shall bear a valid calibration certificates traceable to a national standard indicating calibration validity and periodically (maximum of six months) checked by a third party laboratory testing facility.
  • Electrical materials shall conform to all applicable requirements, standard, and specifications prior to release to be used as part of the work. Refer to Schedule “Q” Att. IV Para 7.1.
  • Review all references such as the latest approved for construction drawings, layout, and Technical Scope of Work.
  • Ensure the manpower, equipment and other resources are prepared prior to start of the activities.

MOTOR (LV/MV) & LOCAL EQUIPMENT

  1. Vendor’s installation instructions shall always be reviewed together with the plans from time to time during the course of the installation activities.
  2. Check the readiness of concrete foundations: anchor bolt, embedded steel bars, etc. The result shall be reported to COMPANY EPC, and a turn over report for concrete foundations shall be provided by Civil Sub contractor, before motor installation takes place.
  3. Check the installed wireways and its access to suit the electrical equipments and devices for the installation ensuring a neat and proper installation as per Technical Scope of work and standards.
  4. The junction box shall be permitted to be separated from the motor by not more than 1.8 m (6ft), provided the leads to the motor are Type AC cable or armored cord or stranded leads enclosed in liquid tight flexible metal conduit. According to NEC 430.245(B).
  5. Sufficient access and working space shall be provided and maintained about enclosure housing electrical to permit ready and safe operation and maintenance of such equipment, NEC Art. 110.26.
  6. Mount the equipment in the position and location as shown on Equipment Location Plan, pertinent Approved for Construction Drawing.
  7. Equipment shall be placed and leveled in proper position.
  8. All threads and plugs, junction boxes and other fittings shall be lightly lubricated with rust preventive grease before assembly. All unused entries to electrical devices shall be plugged to prevent ingress of sand or other foreign matter.
  9. Provide a proper grounding bonding to all equipment and/or devices as approved and shall be connected to grounding bus bar that is to be continuously connected to grounding grid.
  10. All equipment shall be identified by means of stainless steel nameplate affix with stainless screws.
  11. Visual inspection shall include dimensional check and verification of exact location shall be conducted with respect to the latest issued Approved for Construction Drawings that will be recorded using appropriate inspection form.
  12. QC inspection for the completed panels, junction boxes and peripherals installed and its steel supports and stanchion shall be requested while the inspection results shall be filed and recorded using appropriate inspection form during walk through.
  13. Do Pre-Energization walk through.

Inspection and testing of Motor With Megger test

  1. Check documentation for the material receiving of motor for any comments.
  2. Terminals of motors and controllers shall be suitably marked or colored where necessary to indicate the proper connection.
  3. Motor shall be located so that adequate ventilation is provided and so that maintenance, such as lubrication of bearings and replacing of brushes, can be readily accomplished.
  4. Open motors that have commutators or collector ring shall be located or protected so that sparks cannot reach combustible material.
  5. The arrangement of the equipment, including number of bearings, terminal housing, conduit, piping, and auxiliaries (including the rotating element of the exciter, the field discharge resistor, and synchronizing controls as applicable) shall be provided with adequate clearance areas and safe access for installation, operation and maintenance.
  6. The motor and all of its auxiliary devices shall be suitable for and in accordance with the area classification system specified based on the data sheets.
  7. The frames and other metal exteriors of motors (except for insulated pedestal bearings) should be grounded to limit their potential to ground in the event of accidental connection or contact between live electrical parts and the metal exteriors.
  8. The connection of the motor to the power supply should be made by qualified personnel in accordance with the diagram or other instructions furnished by the motor manufacturer.
  9. Inspect physical and mechanical condition of motor.
  10. Check the screens, guards and other personnel protective devices are in place.
  11. Check the motor is properly installed and aligned to the load and its coupler is disconnected.
  12. Check proper rotation of motor. (Use proper precaution for vertical motors).
  13. Measure and record the heater and RTD resistance.
  14. Perform megger test or insulation-resistance test for the motor winding.

 

Do PI test: 1 minute & 10 minutes readings

  1. The polarization index test (PI test) is performed to quantitatively measure the ability of the ground wall insulation to polarize. The PI test is the most confusing HVDC test in use due to the subtleties in the interpretation of the results. When an insulator polarizes, the electric dipoles distributed in the insulator align themselves with an applied electric filed. As the molecules polarize, a “polarization current”, also called an absorption current, is developed that adds to the insulation leakage current. The test results become confusing when attempting to attribute variations in the PI value to the polarizability of the insulator or other affects such as humidity, moisture and instrument error.

The PI test is typically performed at the same voltage as the megaohm test and takes 10 minutes to complete. The PI value is calculated by dividing the insulation resistance at 10 minutes by the resistance at 1 minute as shown below:

PI = IR (10 min)/ IR (1 min)

In general, the insulators that are in good condition will show a “high” polarization index while insulators that are damaged will not. IEEE 43 recommends minimum acceptable values for the various thermal classes of motor insulation.

NEMA Class A 1.5
NEMA Class B 2.0
NEMA Class F 2.0
NEMA Class H 2.0

 

  1. Ground the motor leads after the test and discharge motor windings.
  2. Check the motor is correctly connected to the available power supply voltage.
  3. Measure and record initial bearing temperatures and the ambient temperature and record temperatures during testing.
  4. Prior to execute, earthing shall be checked to ensure it is as per the detail drawing and installed in accordance with SAES-P-111. Testing for motor grounding is necessary by using earth resistance teat or equivalent as in SAES-P-111 para 6.1.18.
  5. Prior to test, the winding shall be grounded in order to drain off any static.

PRE COMMISSIONING TEST OF MOTOR

Functional testing of motor control

  1. At substation side – Day before of the Solo Run Test or megger test
    1. Disconnect the power cable of motor in contactor.
    2. Switch on the breaker, measure the voltage output and test the contactor for functional.
    3. Push start button and check contactor if close and red lights on.
    4. Push stop button and check contactor if open and green lights on.

       2. At field side (for LCS with selector switch type)

Note:

  • Remote : On – Not Activate

: Off – Off

  • Remote : On – On

: Off – Off

  • See Attachment of LCS sequence function checklist for LV & MV Motors.
  • Check the power supply to the LCS.
  • Rotate the selector switch to start and release, check contactor if close in substation and green lights on in LCS.
  • Rotate the selector switch to stop and check contactor if open in substation and red lights in contactor.
  • Switch the breaker on, bump motor and check for proper rotation.

At field side (for built-in LCS with push button type for Motor skid)

    • Check the power supply to the LCS.
    • Rotate selector switch to local position.
    • Push start button and check contactor if close.
    • Push stop button and check contactor if open.
    • After function test of LCS are completed, switch off the breaker and connect power supply cable in contactor.

Switch the breaker on, bump motor and check for Proper rotation.

4 Hour Motor Solo Run Test

Preparation

  1. Secure approved work permit prior to start of work.
  2. Ensure that the approved lock-out/tag-out permit is applied.
  3. Conduct tool box meeting to discuss possible hazard for the activities.
  4. Barricade the working area (testing).
  5. Make sure that the personnel in substation and field side have a clear communication (i.e. Two way radio)

Ensure that the motor to be tested is uncoupled.

Note:

  • Check if power cable is meggered (megger test) prior to start of the motor – Continuity check on cables.
  • Check the rotation by instant energize – Bump Start.

Start The Motor

Measure and record the temperature, vibration, voltage, current and winding resistance using the following document.

  1.  Low Voltage Squirrel Cage Induction Motors (SCIM).
  2.  Medium Voltage Induction and Synchronous Motors (Up to Nameplate Voltage).
  3. PCP-071 –  (LV Motor 4 Hour Run Test) Variable Frequency Drives for NEMA Frame Motors (Pre-commissioning form).
  4. PCP-072 –  (MV Motor 4 Hour Run Test) NEMA Frame, Form Wound Induction and Synchronous Motors (Pre-commissioning form).

After the completion of solo run motor testing, re-install loto, ensure that the lock-out/tag-out permit was signed off.

Ensure that the lock-out/tag-out isolator will put back the padlock @ MCC and LCS.

 

Industry Codes For Megger Test

NFPA                                     National Electrical Code

IEC 60840                             International Standard

TOOLS AND EQUIPMENT IN SOLO RUN TEST OR MEGGER TEST

Tools and equipment needed should be in good condition and must be checked by Supervisor / Safety Engineer prior to use in the construction area.  These includes but not limited to:

  • Welding Machine
  • Electric Power Tools (i.e. drill etc.)
  • Boom Truck
  • Insulation Tester
  • Multi-meter (VOM) – Rated up to 1kV
  • Vibration Meter
  • Temperature Detector Meter
  • Hi-pot Tester
  • Termination Tools
  • Common Hand Tools
  • Ladder
  • Protective Relay Calibration Test Set – (Substation)
  • Current Injector
  • Earth Resistance Test
  • Low Resistance Tester / Ductor Resistance Ohmmeter
  • Phase Sequence
  • LCR Meter
  • Torque Wrench
  • Power Supply

All tools utilized in megger test a classified area should be intrinsically safe and suitable for hazardous areas.

All test equipment to be used for megger test shall be calibrated in accordance with schedule Q requirements shall not exceed six (6) months. Contractor shall provide backup equipment when the primary equipment is being calibrated or tested.

SAFETY PRECAUTION FOR MOTOR MEGGER TEST

  • Secure the approved work permit from the concerned  Representative before starting any work.
  • Conduct proper preparation to include required safety equipment and tools for the commencement of the work.
  • Activities shall be executed in accordance with this procedure and related standards and specifications
  1. Provide warning sign and sufficient barricade on working area. Only assigned personnel will be allowed in the area to maintain a safe work environment.
  2. Conduct safety briefing to all working crew to remind them of all the basic safety requirements on the job to ensure safe work flow.
  3. Continuous monitoring and inspection shall be implemented by the site supervisor/foreman together with the assigned safety supervisor in the area. Any unsafe practices while performing the work activities shall be corrected immediately to avoid stoppage of the work.
  • Good housekeeping shall be maintained throughout the work activity. The work site shall be kept clean and safe before start up of solo runs.
  • Safety Supervisor shall monitor the work activities to help and protect all assigned workers against exposure to safety hazards. He shall ensure that Personal Protective Equipments (PPE’s) are supplied and worn at all times.
  1. MV (PPE’s) to be available at substations.
    1. MV Rated Protective Cover
    2. Face shield
  2. Job Hazard and Risk Assessment of this procedure shall be disseminated and explained to workers for safety awareness.

Read also: Electrical Heat Tracing Testing Procedure

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