QPT’s Acceptance Procedures For Ground Fault Systems

Visual and Mechanical Inspection

  • Inspect physical condition and nameplate compliance to drawings.
  • Inspect neutral main bonding connection to assure proper sizing and that the ground connection is made upstream of the sensor and neutral disconnect link. Ground strap systems are grounded through the sensing device.
  • Inspect ground electrode conductor for proper size and proper connection to ground bus.
  • Check monitor panel trip test, no trip test and manual reset operations (If Applicable).
  • Control Power Transformer is checked for proper sizing (If Applicable).
  • Set pick up and time delay settings in accordance with settings provided by customer.
  • Check tightness of all accessible control connections.

 Electrical Inspection

  • Neutral insulation resistance is measured to ensure no shunt ground paths exist downstream of the sensor.
  • Pick up current is measured by primary injection at the sensor.
  • Pick up current is tested at each pick up tap setting.
  • Verify correct sensor polarities on residual systems single main and double ended substations.
  • Verify correct sensor polarities on zero sequence systems double ended substations.
  • Time delay is tested at two points above pick up current setting by primary injection at the sensor.
  • System operation is tested at 55% reduced voltage level (If Applicable).
  • Multiple source ground fault schemes integrity is tested.
  • Zone interlock system is tested by simultaneous sensor current injection. Zone blocking function is monitored.