Method and apparatus for the protection of electrical equipment from high voltage transients

Claim 2

A high voltage transient protection unit for connection between a power source and a load comprising: a recoverable spark gap electrically connected to the power source, an L-C filter electrically connected to said recoverable spark gap; and a voltage variable resistor electrically connected to said L-C filter and to the load; and a first means for connecting said recoverable spark gap to a first grounding circuit; and a second means for connecting said filter and said voltage variable resistor to a separate and distinct grounding circuit.

Claim 3

A high voltage transient protection unit for connection between a power source and a load comprising a recoverable spark gap means connected to receive power from said power source, said recoverable spark gap means operating to shunt voltage transients above a first predetermined voltage level, a high surge current ground means connected to receive transients shunted by said recoverable spark gap means, L-C filter means connected to said recoverable spark gap means and operative to delay high voltage transients for a delay period sufficient to permit said recoverable spark gap means to operate to shunt transients above said first predetermined voltage level to said high surge current ground means, voltage variable resistance means connected between said L-C filter means and said load, and a low current A.C. ground means connected to said L-C filter means and said voltage variable resistance means, said low current A.C. ground means being separate and distinct from said high surge current ground means, said voltage variable resistance means operating with said L-C filter means to filter to said low current A.C. ground means that portion of a voltage transient between a second predetermined voltage level and said first predetermined voltage level, said second predetermined voltage level being lower than said first predetermined voltage level.

Claim 4

A high voltage transient protection unit for connection between a power source and a load comprising a recoverable spark gap means connected to receive power from said power source, said recoverable spark gap means operating to shunt voltage transients above a first predetermined voltage level, a high surge current ground means connected to receive transients shunted by said recoverable spark gap means, L-C filter means connected to said recoverable spark gap means and operative to delay high voltage transients for a delay period sufficient to permit said recoverable spark gap means to operate to shunt transients above said first predetermined voltage level to said high surge current ground means, voltage variable resistance means connected between said L-C filter means and said load, and a low current A.C. ground means connected to said L-C filter means and said voltage variable resistance means, said low current A.C. ground means being separate and distinct from said high surge current ground means, said voltage variable resistance means operating with said L-C filter means to filter to said low current A.C. ground means that portion of a voltage transient between a second predetermined voltage level and said first predetermined voltage level, said second predetermined voltage level being lower than said first predetermined voltage level.

Claim 5

The unit of claim 2 wherein the recoverable spark gap means includes at least one hermetically enclosed spark gap with a series nonlinear resistance.

Claim 6

The unit of claim 3 wherein said at least one hermetically sealed spark gap is a lightning arrestor.

Claim 7

The unit of claim 2 wherein the total rating of said recoverable spark gap means is about 1000 V RMS.

Claim 8

The unit of claim 2 wherein the L-C filter means includes an L-C filter half section including a high current inductor and a large low loss capacitor.

Claim 9

The unit of claim 6 wherein said inductor has a rating of at least 0.5 mh.

Claim 10

The unit of claim 6 wherein the said inductor has a rating of at least 1 mh.

Claim 11

The unit of claim 6 wherein the said inductor has a rating of 1 mh.

Claim 12

The unit of claim 6 wherein the capacitor has a rating of at least 1 μf.

Claim 13

The unit of claim 6 wherein the capacitor has a rating of at least 10 μf.

Claim 14

The unit of claim 6 wherein the capacitor has a rating of 20 μf.

Claim 15

The unit of claim 6 wherein the said inductor has a very low shunt capacitance.

Claim 16

The unit of claim 6 wherein the said capacitor is ultra-fast.

Claim 17

The unit of claim 6 wherein the said inductor has a rating of 1 mh and said capacitor has a rating of 20 μf.

Claim 18

The unit of claim 6 wherein the low frequency cut-off of the said filter is less than about 2 KHZ.

Claim 19

The unit of the claim 6 wherein the said filter gives at least about 20 db attenuation for lower voltage transients below about 9 KV.

Claim 20

The unit of claim 2 wherein the said voltage variable resistor means includes at least one high voltage metal oxide variable voltage resistor.

Claim 21

The unit of claim 18 wherein said variable voltage resistor is connected in shunt across the filter means output.

Claim 22

The unit of claim 18 wherein the unit includes at least one bleeder resistor connected across said voltage variable resistor.

Claim 23

The unit of claim 18 wherein said voltage variable resistor means includes two high voltage metal oxide varistors connected in series.

Claim 24

The unit of claim 21 in which each of said varistors has a rating of about 480 volts.

Claim 25

The unit of claim 21 wherein a bleeder resistor is connected across each of said varistors.

Claim 26

The unit of claim 2 wherein each said high surge current ground means and low current A.C. ground means includes at least one grounding rod.

Claim 27

The unit of claim 24 wherein said at least one grounding rod of said first circuit is spaced from said at least one grounding rod of said second circuit.

Claim 28

The unit of claim 25 wherein said rods are separated by a distance of at least 4 feet.

Claim 29

The unit of claim 24 wherein said at least one grounding rod of said low current AC ground means lies out of the ground return path of said high surge current ground means.

Claim 32

The method of claim 28 wherein said minimum level is about 9 KV.

Claim 33

The method of claim 28 wherein said minimum level is the minimum level at which said spark gap will fire.

Claim 34

The method of claim 28 wherein said predetermined maximum level is below the voltage level at which damage to said electrical equipment would result.

Claim 35

The method of claim 28 wherein said predetermined minimum voltage level is established by the operational firing voltage of said spark gap.

Claim 36

The method of claim 28 wherein said predetermined maximum voltage level is established by the starting transient level of the said equipment.

Claim 37

The method of claim 28 wherein said delaying is for a period of at least about 10 μs.

Claim 38

A high voltage transient protection unit for connection between the power source of a power distribution system having a distribution system ground and a variable impedance load having a maximum starting transient voltage level comprising a recoverable spark gap means connected to receive power from said power source, said recoverable spark gap means operating to shunt transients above a first predetermined voltage level greater than the maximum starting transient voltage level of said variable impedance load, a high surge current ground means connected to receive transients shunted by said recoverable spark gap means, a high Q L-C filter means connected to said recoverable spark gap means and operative to delay high voltage transients from said power supply for a delay period sufficient to permit said recoverable spark gap means to operate to shunt transients above said first predetermined voltage level to said high surge current ground means, voltage variable resistance means connected between said high Q L-C filter means and said variable impedance load, said voltage variable resistance means operating to clip voltage transients from said high Q L-C filter means at a voltage level which is no higher than the maximum starting transient voltage level of said variable impedance load, and a low current A.C. ground means connected to said high Q L-C filter means and to said voltage variable resistance means, said low current A.C. ground means being separate and distinct from said high surge current ground means.

Claim 39

A high voltage transient protection unit for connection between the power source of a power distribution system having a distribution system ground and a variable impedance load having a maximum starting transient voltage level comprising a recoverable spark gap means connected to receive power from said power source, said recoverable spark gap means operating to shunt transients above a first predetermined voltage level greater than the maximum starting transient voltage level of said variable impedance load, a high surge current ground means connected to receive transients shunted by said recoverable spark gap means, a high Q L-C filter means connected to said recoverable spark gap means and operative to delay high voltage transients from said power supply for a delay period sufficient to permit said recoverable spark gap means to operate to shunt transients above said first predetermined voltage level to said high surge current ground means, voltage variable resistance means connected between said high Q L-C filter means and said variable impedance load, said voltage variable resistance means operating to clip voltage transients from said high Q L-C filter means at a voltage level which is no higher than the maximum starting transient voltage level of said variable impedance load, and a low current A.C. ground means connected to said high Q L-C filter means and to said voltage variable resistance means, said low current A.C. ground means being separate and distinct from said high surge current ground means.

Claim 40

The high voltage transient protection unit of claim 35 wherein said low current A.C. ground means is located so as not to be between said distribution system ground and said high surge current ground means.