DC Systems

Direct current (DC) systems have positive and negative buses. If either bus is grounded, then it is referred to as a grounded system. If neither bus is grounded, then it is referred to as an ungrounded dc system. A ground fault on a dc system may cause damage to the source as well as in the field.

If the system is ungrounded, then it is possible to use a ground-fault relay by installing a ground-reference module between the two buses to establish a neutral point. The ground-fault relay uses this neutral point as a reference to detect low-level ground faults.

FIGURE 3