Abstract: A gapped low voltage bushing (10) comprising a controlled spark gap (1), a metallic arc strap (18), a resistive material (46) and a metallic tank ground pad. Surges entering the transformer on any of the secondary bushings of sufficient magnitude to induce gap sparkover, result in a shunting of otherwise damaging currents safely outside the transformer.

Abstract: A two-stage gapped low voltage surge arrester for dissipating transformer secondary side current surges includes an arc strap in series with a resistive grommet. The combination is mounted on the grounded transformer housing adjacent a line potential bushing such that a first spark gap is formed between the bushing stud and arc strap. The resistive grommet is grounded to the transformer ground pad by metallic fasteners such that a second spark gap is formed in parallel with the resistive grommet. Surges entering the transformer secondary winding of sufficient magnitude induce the first spark gap to flash over, shunting potentially damaging currents outside the transformer through the arc strap and resistive grommet. At even higher currents, the voltage across the resistive grommet exceeds the flash over voltage of the second spark gap and shunts the surge around the resistive grommet.