Patent ID: 8369058

Claim:
A Compact Secondary Substation (CSS) comprising a fault protection system, which CSS comprises a Ring Main Unit (RMU) with high voltage power lines, a transformer and a low voltage (LV) switchgear, characterized in that the CSS comprises: detectors that detect the occurrence of an arc fault, which detectors are placed at least in one of the RMU, the transformer or the LV switchgear, a control unit and the detectors are connected to the control unit, and at least one switch for grounding, circuit breakers arranged at a high voltage inlet in the CSS, wherein said control unit, upon arc fault detection by the detectors, activates the switch for grounding, thereby grounding at least one of the high voltage power lines, and said control unit also controls the switch as a working grounding switch, wherein activation of said switch causes said at least one circuit breaker to activate such that the arc fault is cleared selectively.