QPT’s Maintenance Procedure For Transfer Switches and Schemes – Auto and Manual

Visual and Mechanical Inspection

  • Inspect physical damage, anchorage and grounding.
  • Clean using approved methods.
  • Inspect interior condition, arc chutes and inter-phase barriers.
  • Perform mechanical operator tests. Lubricate as required.
  • Check bypass and isolation functions if possible.
  • Check main blade alignment, setting and arc interrupter operation.
  • Check mechanical interlocks for proper operation.
  • Check tightness of all accessible hardware and control connections.
  • Check all accessible cable and bus connections for tightness by calibrated torque wrench method.
  • Check control and relay contacts.
  • Check control and sensing relays.
  • Check all indicating devices for proper operation.

Electrical Inspection

  • Insulation resistance test voltage is applied phase to phase and phase to ground with switch in both normal and emergency positions.
  • Contact resistance is measured across each switch poles in both normal and emergency positions.
  • Check ATS electrical interlocks.
  • Check bypass and isolation electrical interlocks if possible.
  • Set and calibrate TS coil contacts (A critical check).
  • Set and calibrate timing and sensing circuits (If required).
  • Monitor and verify correct operation of the following:
  1. Normal voltage sensing pickup and dropout.
  2. Emergency voltage sensing pickup and dropout.
  3. Emergency frequency sensing pickup and dropout.
  4. Override momentary outage time.
  5. Transfer to emergency time.
  6. Re-transfer to normal time.
  7. Generator set cool down time.
  8. and any accessory’s as needed.
  9. Measure normal and emergency voltage.
  10. Measure current levels and determine percent of full load when possible.
  11. Measure generator frequency.
  12. Energized functional check is performed on the ATS.