High resistance grounding (HRG) is implemented for several reasons; and may not be the recommended method of system grounding for all systems. The specifying engineer should evaluate each individual system to determine the type of system grounding needed. Some of the benefits of HRG are:
  • Control of transient over-voltages during ground fault
  • Minimize arcing damage at the point of ground fault
  • Minimize flash hazard due to ground fault at the point of ground fault
  • Allow continued operation of a system which has a single line to ground fault until system can be shut down to remove the ground fault
  • Give immediate indication of a ground fault present
The following are some (not all) of the considerations when applying HRGs:
  • HRGs are intended to be used on 3-phase, 3-wire systems only; where no phase-neutral loads are being supplied
  • HRGs continuous current should be set above the system’s capacitive charging current
  • HRGs are not intended to allow systems to operate indefinitely with a ground fault.
  • Apparatus using rectifiers attached to the system without isolation transformers, or phase to ground connections may cause issues
  • Most power systems rated 2400V and above typically do not benefit from the use of HRG
HRG units are available as:
  • Wye connected units
  • Phase derived units
  • Stand alone HRG units
  • Integrated into motor control centers, metal-clad switchgear, metal-enclosed switchgear