Fault locating system for electric cables and the like

A system for locating a high resistance fault between two conductors in a cable comprising means for applying a voltage across the conductors so as temporarily to produce an arc plasma between the conductors at the high resistance fault, said voltage applying means including a switchable current pulse source, nondissipating means for limiting the current through the arc plasma to limit power so as to avoid damage to the conductors, said nondissipating current limiting means acting to switch said switchable current pulse source, and means for affording detection of the location of the low resistance path through the arc plasma while the arc plasma exists.

A system for locating a high resistance short between a pair of conductors comprising a transformer having a secondary winding coupled across the conductors, a primary winding and a core flux linking the primary and secondary windings, a power source and a series connected primary switch connected in series with the primary winding so as to produce a current flow therethrough when the primary switch is closed, means for periodically closing and opening the primary switch so as to produce pulsating current flow through said primary winding, said transformer tending to fly back in response to opening said primary switch, switching means connected across at least a part of said secondary winding for shorting the same during opening of said primary switch so that upon opening of said switching means said transformer flies back to produce a voltage pulse across said secondary winding, said secondary winding having a tap and feedback means connected from said tap to said power source for limiting the voltage at said tap to that of said power source so that the location of said tap establishes the output voltage of said secondary winding.

A system for locating a high resistance fault between a conductor pair comprising a pulse source for producing a pulse at a voltage sufficient to arc across the fault to form a low resistance current path therethrough, said pulse source including a flyback transformer having a primary winding, a secondary winding, a core flux linking said windings, a current source for supplying current to said primary winding to store energy in said core and means for gating current flow from said current supplying means through said primary winding;

• means for connecting said conductor pair across said secondary winding;
• means for limiting the current through the low resistance path to avoid fusing the conductor, said current limiting means including means in series with said current supplying means for sensing the magnitude of current flow therethrough and means responsive to said current sensing means for disabling said gating means when the current reaches a preselected magnitude;
• and detecting means for affording detection of the location of the low resistance path.

A system for locating a high resistance fault between two conductors in a cable comprising means for applying a voltage across the conductors so as to produce an arc between the conductors at the high resistance fault, said voltage applying means including a transformer having a core, a primary winding flux linked to the core, a secondary winding flux linked to the core, a pulse source for supplying current pulses to said primary winding so that the transformer flies back upon termination of each said current pulse, and means for connecting the conductors across the secondary winding to receive energy when said transformer flies back;

• means for limiting the current through the arc to avoid damage to the conductors, said current limiting means including a switch connected across at least a part of said secondary winding and being controlled by said pulse source so as to short out said secondary winding after termination of current supplied to said primary winding;
• and means for affording detection of the location of the arc.

A system for locating a high resistance fault between a conductor pair comprising a pulse source for producing a pulse at a voltage sufficient to temporarily arc across the fault to form at the fault a temporary arc plasma having a low resistance current path therethrough, said pulse source including an inductor, means for supplying current to said inductor to effect storage of energy therein, means for causing said inductor to fly back and rapidly discharge the stored energy and means connecting said conductor pair across said inductor to receive the energy discharged therefrom, means for limiting the current through the low resistance path to limit the power dissipated in the arc so as to avoid fusing the conductor, and detecting means for affording detection of the location of the low resistance path during the presence of the arc plasma.

A systen for locating a high resistance fault between two conductors in a cable comprising means for applying a voltage across the conductors so as temporarily to produce an arc plasma between the conductors at the high resistance fault, said voltage applying means including an inductor, means for supplyng current to said inductor to effect storage of energy therein, means for causing said inductor to fly back and rapidly discharge the stored energy and means connecting the conductors across said inductor to receive the energy discharged therefrom, means for limiting the current through the arc plasma to limit power so as to avoid damage to the conductors, and means for affording detection of the location of the low resistance path through the arc plasma while the arc plasma exists.