If relays are present, the ground fault relay would be a residually connected overcurrent relay or a 51N device. These relays are typically not set as low as the 51G device due to error currents in the phase relays. Facilities strive for minimum allowable pickup settings, and therefore coordination should still be checked as was done in Figure 2. For utilities that utilize a uni-grounded system or an ungrounded system, the utility should be consulted to determine if the capacitor bank grounding will interfere with their system. Ground relays on Uni-grounded utility distribution system may be set low enough to pickup.
Ungrounded system raise an unrelated concern with overvoltages from uncleared ground faults.
With the forgoing discussion it should be clear that the installation of grounded capacitor banks to industrial and commercial power system can interfere with a facilities ground fault protection system. Proper engineering may be done to overcome these problems, but this adds to the cost and complexity of the installation. Fuse coordination is difficult on smaller banks because a failed capacitor will only draw three times the bank nominal current rating. Overvoltage conditions can occur on the unfaulted capacitors on unbalance banks due to a fuse blowing. The above issues can be engineered out of the design by the manufacturer without any regard to the system for which it is being applied to.