Voltage surge arrester device

Claim 2

An overvoltage surge arrester comprising: at least one high-exponent varistor having an exponent greater than 10 for electrical connection between a voltage line and ground; at least one low-exponent varistor having an exponent less than 10 in series with said high-exponent varistor for providing a more rapid voltage increase than for the high-exponent varistor; and at least one shunt gap shunting said low-exponent varistor and a portion of said high-exponent varistor for reducing the arrester voltage during a condition of electrical overvoltage.

Claim 3

The overvoltage surge arrester in claim 1 including at least one further high exponent varistor in series with said low exponent varistor for increasing said varistor voltage rating.

Claim 4

The overvoltage surge arrester of claim 2 wherein the ratio of the exponent of the high exponent varistor to the exponent of the low exponent varistor comprises at least 2 to 1.

Claim 5

The voltage arrester of claim 1 wherein the high exponent varistor comprises zinc oxide and the low exponent varistor comprises silicon carbide.

Claim 6

The voltage surge arrester of claim 1 wherein the high exponent material comprises zinc oxide and the low exponent material comprises zinc oxide doped with an exponent modifying additive.

Claim 7

An electrical overvoltage surge arrester comprising: at least one first varistor having a first exponent for electrical coupling between a voltage line and ground for causing surge current to flow from said line to ground upon the condition of a voltage surge; at least one second varistor having a second exponent and electrically connected in series with said first varistor, the exponent of said second varistor being lower than the exponent of said first varistor for causing a faster voltage increase across said second varistor; and at least one shunt gap having a predetermined sparkover voltage across said first and second varistors for shunting current from said first and second varistors when said predetermined voltage appears across said shunt gap.

Claim 8

An electrical overvoltage surge arrester comprising: at least one first varistor having a first exponent for electrical coupling between a voltage line and ground for causing surge current to flow from said line to ground upon the condition of a voltage surge; at least one second varistor having a second exponent and electrically connected in series with said first varistor, the exponent of said second varistor being lower than the exponent of said first varistor for causing a faster voltage increase across said second varistor; and at least one shunt gap having a predetermined sparkover voltage across said first and second varistors for shunting current from said first and second varistors when said predetermined voltage appears across said shunt gap.

Claim 9

The voltage surge arrester of claim 6 wherein the predetermined shunt gap voltage occurs within a surge current range from 10 to 1000 amperes.

Claim 10

The voltage surge arrester of claim 6 wherein the predetermined shunt gap voltage comprises at least 5% of the arrester voltage.

Claim 11

The voltage surge arrester of claim 6 wherein the exponent of the first varistor is at least two times larger than the exponent of the second varistor.