Fault protection device in a transformer

A fault protection device incorporated in a transformer having a primary winding and at least two secondary windings, said secondary windings being defining sides and two ends and being located on either side of said primary winding and being connected to ground, and having a generally closed loop core having a central core portion extending through said primary winding and said secondary windings, and having a further core loop portion extending around one side of said primary and said secondary windings and said closed loop defining loop ends around said secondary windings, and shunt core portions extending across said closed loop core located between said primary winding and respective said secondary windings, said secondary windings generating magnetic fluxes when in use, said fault protection device comprising:

• a flux sensing coil in turn comprising two flux sensing coil portions, each said coil portion being located on a part of said further core loop portion between said shunt core portions and sides of adjacent respective said secondary windings and operable to sense the fluxes generated by respective said secondary windings, said coil portions being connected to one another and generating a zero signal when the fluxes of respective said secondary windings are equal, and generating a flux signal when an imbalance in the fluxes generated by respective said secondary windings is detected by said coil portions;
• and
• switch means connected to respond to said signals in said sensing coil a and connected in series with a power supply and at least one terminal of said primary winding, said switch means being conditioned to an open condition in response to said flux signal to isolate said primary winding from said power supply.

A fault protection device incorporated in a transformer having a primary winding and at least two secondary windings, said secondary windings defining sides and two ends and being located on either side of said primary winding and being connected to ground, and having a central core portion extending through said primary winding and said secondary windings and having a closed loop core portion extending around both sides of said primary winding and said secondary windings, and joining with said central core portion, and having four shunt portions, arranged in pairs, a first pair of shunt portions being located between said primary winding and said secondary windings and extending from one portion of said closed loop core portion to said central core portion, and said second pair of shunt portions being located between the other said closed loop core portions and said primary and said secondary windings and extending from said closed loop portion to said central core portion, said secondary windings generating magnetic fluxes when in use, said fault protection device comprising:

• a flux sensing coil in turn comprising two flux sensing coil portions, each said coil portion being located on a said closed loop core portion adjacent sides of said secondary windings and extending around adjacent ones of said shunt portions between said closed loop core portion and respective said secondary windings and operable to sense the fluxes generated by respective said secondary windings, said coil portions being connected to one another and generating a zero signal when the fluxes of respective said secondary windings are equal, and generating a flux signal when an imbalance in the fluxes generated by respective said secondary windings is detected by said coil portions;
• and
• switch means connected to respond to said signals in said sensing coil a and connected in series with a power supply and at least one terminal of said primary winding, said switch means being conditioned to an open condition in response to said flux signal to isolate said primary winding from said power supply.