SPARK GAP ASSEMBLY FOR OVERVOLTAGE PROTECTION AND SURGE ARRESTER

1 . A spark gap assembly comprising:

a first spark gap segment including a first spark gap and a first grading circuit electrically connected in parallel with the first spark gap; and

a second spark gap segment electrically connected in series with the first spark gap segment, the second spark gap segment including a second spark gap and a second grading circuit electrically connected in parallel with the second spark gap,

wherein a difference between an impedance of the first grading circuit and an impedance of the second grading circuit is approximately zero at a normal operating frequency, and

wherein the difference increases as a function of frequency.

2 . The spark gap assembly of claim 1 , wherein the spark gap assembly is electrically connected in series with a metal oxide varistor (MOV).

3 . The spark gap assembly of claim 1 , wherein the first grading circuit includes at least one selected from the group consisting of a resistor, a capacitor, and an inductor; and

the second grading circuit includes at least one selected from the group consisting of a resistor, a capacitor, and an inductor.

4 . The spark gap assembly of claim 1 , wherein the spark gap assembly is included in an accessory device that is electrically connected in series with a surge arrester.

5 . The spark gap assembly of claim 1 , wherein the spark gap assembly is included in a surge arrester.

6 . The spark gap assembly of claim 1 , wherein a first ratio of a voltage across the first spark gap to a sparkover voltage of the first spark gap is approximately equal to a second ratio of a voltage across the second spark gap to a sparkover voltage of the second spark gap when the spark gap assembly is operated at the normal operating frequency.

7 . The spark gap assembly of claim 1 , wherein a first ratio of a voltage across the first spark gap to a sparkover voltage of the first spark gap is greater than a second ratio of a voltage across the second spark gap to a sparkover voltage of the second spark gap when the spark gap assembly is operated at a frequency higher than the normal operating frequency.

8 . The spark gap assembly of claim 1 , wherein the difference is a first difference, the spark gap assembly further comprising:

a third spark gap segment electrically connected in series with the first spark gap segment and the second spark gap segment, the third spark gap assembly including a third spark gap and a third grading circuit electrically connected in parallel with the third spark gap,

wherein a second difference of the impedance of the first grading circuit and an impedance of the third grading circuit is approximately equal to zero at a normal operating frequency,

wherein the second difference increases as a function of frequency, and

wherein the second difference increases faster than the first difference as frequency increases.

9 . The spark gap assembly of claim 1 , wherein an initial sparkover voltage of the spark gap assembly is greater than a subsequent sparkover voltage of the spark gap assembly at a frequency greater than the normal operating frequency.

10 . An arrester comprising:

a spark gap assembly including

a first spark gap segment including a first spark gap and a first grading circuit electrically connected in parallel with the first spark gap; and

a second spark gap segment electrically connected in series with the first spark gap segment, the second spark gap segment including a second spark gap and a second grading circuit electrically connected in parallel with the second spark gap,

wherein a difference between an impedance of the first grading circuit and an impedance of the second grading circuit is approximately zero at a normal operating frequency, and,

wherein the difference increases as a function of frequency.

11 . The arrester of claim 10 further comprising a metal oxide varistor (MOV) that is electrically connected in series with the spark gap assembly.

12 . The arrester of claim 10 , wherein the first grading circuit includes at least one selected from the group consisting of a resistor, a capacitor, and an inductor; and

the second grading circuit includes at least one selected from the group consisting of a resistor, a capacitor, and an inductor.

13 . The arrester of claim 10 , wherein a first ratio of a voltage across the first spark gap to a sparkover voltage of the first spark gap is approximately equal to a second ratio of a voltage across the second spark gap to a sparkover voltage of the second spark gap when the spark gap assembly is operated at the normal operating frequency.

14 . The spark gap assembly of claim 10 , wherein a first ratio of a voltage across the first spark gap to a sparkover voltage of the first spark gap is greater than a second ratio of a voltage across the second spark gap to a sparkover voltage of the second spark gap when the spark gap assembly is operated at a frequency higher than the normal operating frequency.

15 . The arrester of claim 10 , wherein the difference is a first difference, wherein spark gap assembly further includes:

a third spark gap segment electrically connected in series with the first spark gap segment and the second spark gap segment, the third spark gap assembly including a third spark gap and a third grading circuit electrically connected in parallel with the third spark gap,

wherein a second difference of the impedance of the first grading circuit and an impedance of the third grading circuit is approximately equal to zero at a normal operating frequency,

wherein the second difference increases as a function of frequency, and

wherein the second difference increases faster than the first difference as frequency increases.

16 . The arrester of claim 10 , wherein an initial sparkover voltage of the spark gap assembly is greater than a subsequent sparkover voltage of the spark gap assembly at a frequency greater than the normal operating frequency.

17 . An accessory device electrically connected in series with an arrester, the accessory device comprising:

a spark gap assembly including

a first spark gap segment including a first spark gap and a first grading circuit electrically connected in parallel with the first spark gap; and

a second spark gap segment electrically connected in series with the first spark gap segment, the second spark gap segment including a second spark gap and a second grading circuit electrically connected in parallel with the second spark gap,

wherein a difference between an impedance of the first grading circuit and an impedance of the second grading circuit is approximately zero at a normal operating frequency, and,

wherein the difference increases as a function of frequency.

18 . The accessory device of claim 17 , wherein the arrester includes a metal oxide varistor (MOV) disc.

19 . The accessory device of claim 17 , wherein the difference is a first difference, wherein spark gap assembly further includes:

a third spark gap segment electrically connected in series with the first spark gap segment and the second spark gap segment, the third spark gap assembly including a third spark gap and a third grading circuit electrically connected in parallel with the third spark gap,

wherein a second difference of the impedance of the first grading circuit and an impedance of the third grading circuit is approximately equal to zero at a normal operating frequency,

wherein the second difference increases as a function of frequency, and

wherein the second difference increases faster than the first difference as frequency increases.

20 . The accessory device of claim 17 , wherein the arrester does not include a spark gap.