What is ground-fault protection?

Ground-Fault Protection of equipment is a system intended to provide protection of equipment from damaging line-to-ground fault currents by operating to cause a disconnecting means to open all ungrounded conductors of the faulted circuit. This protection is provided at current levels less than those required to protect conductors from damage through the operation of a supply circuit overcurrent device.

The importance of ground-fault protection

Ground fault protection is vital to ensure the safety of personnel and equipment. Grounding, bonding and ground fault protection are vital to decrease shock hazards to personnel during a ground fault such as when a current-carrying conductor's insulation fails or inadvertently faults to ground.

Ground-fault protection of ungrounded system

The absence of an equipment grounding conductor does not mean that ground fault protection cannot be used. The zero-sequence impedance of a set of conductors is impacted by several factors including conductor arrangement, presence of grounding paths and the surrounding environment. Ground fault protection on ungrounded systems are normally voltage-based, as no ground-fault current will flow if only one conductor is faulted to ground. If a second conductor were to fault to ground, the fault would be phase-to-phase and would not introduce significant ground-fault current. As the line-to-ground voltage on the unfaulted phases of an ungrounded system experiencing a fault will increase to match the line-to-line voltage, an overvoltage relay must be used to protect these systems.

Philippine Electrical Code requirement for ground-fault protection

The Philippine Electrical Code 2017 edition have mentioned Ground-Fault Protection or sometimes Ground-Fault Circuit Interrupter Protection in the following articles:

  1. Article 2.10 Branch Circuits
    • Ground-Fault Circuit-Interrupter Protection for Personnel.
  2. Article 2.15 Feeders
    • Ground-Fault Circuit-Interrupter Protection for Personnel.
    • Ground-Fault Protection of Equipment.
  3. Article 2.30 Services
    • Ground-Fault Protection of Equipment.
  4. Article 2.40 Overcurrent Protection
    • Ground-Fault Protection of Equipment.
  5. Article 5.13 Aircraft Hangars
    • Ground-Fault Circuit-Interrupter Protection for Personnel.

These requirements of PEC for GFCI protected circuits is very limited compared to the IEC which requires all lighting and socket outlets to be protected by RCD or ELCBs.


Comments are closed