Variable-speed drives and pulsing ground-fault location

Variable-frequency drive

and built-in ground-fault protection

Adjustable-speed drives often include a ground-fault protection function. However, in most cases the protection is not compatible with high-resistance-grounded (HRG) systems. The protection is often not adjustable to a value below the neutral-grounding-resistor (NGR) let-through current rating.

When this is the case, and ground-fault detection is a requirement of the system design, a supplemental ground-fault-protection device, typically a residual-current monitor, must be used.