Method for Locating Phase to Ground Faults in DC Distribution Systems

Electrical direct current (DC) distribution systems are operated without any of the phases grounded in order to prevent a phase-to-ground fault, the most common type of faults, to cause interruption of service. While theoretically such an ungrounded DC system can be operated with one phase grounded through a fault for an extended period of time, it is essential to find the fault location quickly in order to prevent any secondary phase to ground fault on the other phase to cause a disruptive phase-to-phase fault.

The present invention describes a method for locating ground faults in an ungrounded or high-resistance grounded power distribution system having a power supply including high-speed switched power electronics (PE). The method includes utilizing wavelet analysis using Multi-Resolution Analysis (MRA) as a signal processing tool for recognition of characteristic features in the voltage signal. The voltage signal contains characteristic information in the high frequency range above the switching frequencies of the PE converters which allows for localization of the fault.

In the future, the Invention can potentially simplify and speed up the phase-to-ground protection on converter dominated ungrounded DC and AC systems significantly. The Invention can be implemented as a computational component within a new version of a digital ground fault protection relay.