expensive solid grounding can be provided, but this feature should be
220.127.116.11 Impedance Grounding. For medium-voltage systems, impedance
grounding is normally provided to limit ground fault current to a value
equal to or below the three-phase fault current. Reactance grounding is
used where ground fault currents of 25 to 100 percent of three-phase
currents allows for satisfactory ground fault relaying. Resistance
grounding is used when even lower values of ground fault current are
necessary for system protection or coordination.
8.4.3 Protective Relaying. Protective relays constantly monitor the power
system to assure maximum continuity of the generation and distribution
system and to minimize the damage to life and property.