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NUMERICAL MOTOR PROTECTION AND MOTOR CONDITION MONITORING

COURSE DESCRIPTION :

       HT MOTORS

• Fundamentals of Induction Motor

  • Speed-Torque Characteristics, Equivalent Circuit, Transient Model, V/F Control

• Major Protection Elements

  • Thermal : Motor curves and over load protection, RTD / thermistor for over load protection, practical way to set over load relay when thermal curves are not available

  • Negative Sequence : Setting criteria, DMT and IDMT characteristics.

  • Locked Rotor : Setting criteria for stalling protection. How to set when starting and stalling data are not known.

  • Short Circuit : Extra features available in numerical protection relays.

  • Earth Fault : Application check for solidly grounded and resistance grounded systems; CBCT applications - problems at site during adopting settings; options to set earth fault element depending on magnitudes of starting current and ground fault current.

  • Other Protections : Differential, under voltage, under current, start up (for hot and cold restarts) and rotor open circuit.

  • Typical calculation for numerical motor protection relay settings (SPAM 150C to 7SJ 600).

       LT MOTORS

• Recommended protections for LT motors: emerging trends.

• Why MCC incomer trips before motor fuse blows? Problems of relay - fuse co-ordination-Remedial measures-case study.

• Voltage dip and re-acceleration schemes.

• Variable Frequency Drives

  • Selection of motor insulation-design aspects.

  • Shaft voltage, Bearing current-problem and mitigation.

  • Applicable Standards.

• CONDITION MONITORING

  • IR & PI values : Do they adequately characterise insulation healthiness?

  • New techniques in monitoring motor insulation condition:

    • Dielectric absorption test

    • Capacitance and tan delta measurement

    • Partial discharge testing

    • High pot test: DC vs AC

  • Life of motor insulation.