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Electric Power Utility Motor Case Study. Diagnostics & Resolution Power utility contracted to perform off-line circuit and insulation testing of critical motors during major planned outage. Tests included MCA, IR & overvoltage hipot and impulse.

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electric power utility motor case study
Electric Power Utility Motor Case Study
  • Diagnostics & Resolution
    • Power utility contracted to perform off-line circuit and insulation testing of critical motors during major planned outage. Tests included MCA, IR & overvoltage hipot and impulse.
    • New 4 kV motors are impulse tested to 11.4 kVpk (IEEE). Recommended maintenance test is 9 kVpk. Impulse test discovered a 4 kV pump motor with phase insulation breakdown voltage of 7.2 kVpk. No indication of problem during MCA, IR and hipot tests.
    • Utility opted to start the motor repeatedly to study failure of weak motor insulation system. Insulation failed catastrophically on fifth startup.
    • Motor was rewound during planned shutdown
  • Cost of Diagnostics to Utility: <$10,000 including travel
  • Savings to Utility
    • No lost production: Potentially $100Ks
    • No emergency repair costs: $10Ks
electric power utility motor case study1
Electric Power Utility Motor Case Study
  • Diagnostics & Resolution
    • Power utility contracted to perform off-line circuit and insulation testing of critical motors during major planned outage. Tests included MCA, IR & overvoltage hipot and impulse.
    • New 4 kV motors are impulse tested to 11.4 kVpk (IEEE). Recommended maintenance test is 9 kVpk. Impulse test discovered a 4 kV pump motor with phase insulation breakdown voltage of 7.2 kVpk. No indication of problem during MCA, IR and hipot tests.
    • Utility opted to start the motor repeatedly to study failure of weak motor insulation system. Insulation failed catastrophically on fifth startup.
    • Motor was rewound during planned shutdown
  • Cost of Diagnostics to Utility: <$10,000 including travel
  • Savings to Utility
    • No lost production: Potentially $100Ks
    • No emergency repair costs: $10Ks
high voltage surge or impulse
High Voltage Surge or Impulse
  • IEEE 522 & EASA
  • Simulates the transients on power lines which can cause insulation failure. Rise time = 0.1 µsec
  • Impulse test of turn and phase insulation where test voltage is incrementally increased in a stepped mode from 0V voltage to target test voltage looking for change in response frequency
  • Final impulse test voltage typically at 2 x line voltage + 1000 V (peak)
  • Only test capable of complete predictive testing of turn and phase insulation
steps of degrading insulation electrical failure
Steps of Degrading Insulation Electrical Failure
  • New insulation has high break down voltage
  • Motor insulation experiences aging
    • Thermal aging
    • Chemical or moisture contamination
    • Mechanical wear
    • Corona/Partial Discharge
  • Turn, phase or ground insulation break down voltage degrades resulting in arcing due to transients, start up coil movement, etc
steps of degrading insulation electrical failure1
Steps of Degrading Insulation Electrical Failure
  • Induced arcs cause insulation to deteriorate much faster
  • Turn to turn or ground insulation breakdown voltage drops below operating voltage effectively causing a short between turns or a short to ground.
      • Shorted turns transformer action causes a large induced current in the short which creates a hot spot
  • Heat causes rapid insulation failure (typically minutes to hours)
electric power utility motor case study2
Electric Power Utility Motor Case Study
  • Diagnostics & Resolution
    • Power utility contracted to perform off-line circuit and insulation testing of critical motors during major planned outage. Tests included MCA, IR & overvoltage hipot and impulse.
    • New 4 kV motors are impulse tested to 11.4 kVpk (IEEE). Recommended maintenance test is 9 kVpk. Impulse test discovered a 4 kV pump motor with phase insulation breakdown voltage of 7.2 kVpk. No indication of problem during MCA, IR and hipot tests.
    • Utility opted to start the motor repeatedly to study failure of weak motor insulation system. Insulation failed catastrophically on fifth startup.
    • Motor was rewound during planned shutdown
  • Cost of Diagnostics to Utility: <$10,000 including travel
  • Savings to Utility
    • No lost production: Potentially $100Ks
    • No emergency repair costs: $10Ks
slide9
Contact Info:Torq EngineeringRandy Keenercell: 970-412-9337randy.keener@teamtorq.comField ServicesTrainingData Analysis