Ground fault detector and locator

Claim 1

An apparatus for the detection of ground faults in a normally ungrounded a-c or d-c multifeeder power distribution system comprising: a d-c power supply, a pulse grounding circuit connected across said power supply, said pulse grounding circuit comprising transistor means connected across a pair of probe receptacle jacks and a multivibrator means for pulsing said transistor means, said jacks being connectable across the distribution system for adding a ground fault to the distribution system being checked for ground faults in a pulsating fashion, whereby the added ground fault in a grounded conduit of the distribution system will create an a-c component of the ground current created thereby for sensing by a sensing circuit, a sensing circuit comprising a clamp-on current probe, said probe comprising a yoke for surrounding said grounded conduit of the distribution system which conduit serves as a single primary turn of a transformer, said yoke being wound with a number of turns of a wire forming a secondary winding of the transformer the terminals forming the ends of said wire being connected across a comparator circuit, and a comparator circuit for receiving signals from said probe, said comparator circuit when receiving a negative voltage of a predetermined value generating a positive pulse for energizing a first light emitting diode indicating a ground fault on the conduit surrounded by said yoke.

Claim 2

An apparatus for the detection of ground faults in a normally ungrounded a-c or d-c multifeeder power distribution system comprising: a d-c power supply, a pulse grounding circuit connected across said power supply, said pulse grounding circuit comprising transistor means connected across a pair of probe receptacle jacks and a multivibrator means for pulsing said transistor means, said jacks being connectable across the distribution system for adding a ground fault to the distribution system being checked for ground faults in a pulsating fashion, whereby the added ground fault in a grounded conduit of the distribution system will create an a-c component of the ground current created thereby for sensing by a sensing circuit, a sensing circuit comprising a clamp-on current probe, said probe comprising a yoke for surrounding said grounded conduit of the distribution system which conduit serves as a single primary turn of a transformer, said yoke being wound with a number of turns of a wire forming a secondary winding of the transformer the terminals forming the ends of said wire being connected across a comparator circuit, and a comparator circuit for receiving signals from said probe, said comparator circuit when receiving a negative voltage of a predetermined value generating a positive pulse for energizing a first light emitting diode indicating a ground fault on the conduit surrounded by said yoke.