Voltage indicator for high voltage switchgear

Claim 2

A voltage indicator system for use with an electrical conductor having electrical insulation disposed thereon comprising a light producing means having a plurality of terminals and adapted to produce light in the presence of a predetermined electric field, first and second capacitive means, said electrical conductor being capable of producing an electric field when a high voltage potential is applied thereto, said electric field being coupled to one said terminal of said light producing means through said first capacitive means, a photosensitive cell with a plurality of terminals, an amplifierindicator connected in circuit relation with said cell, said light from said light producing means energizing said photosensitive cell to produce an output when said field is present, said amplifier-indicator being responsive to the output of said photosensitive cell to produce an indication of the presence of said field, said second capacitive means comprising a first electrically conducting plate which is electrically connected to another said terminal of said light producing means, a metallic enclosure comprising at least one electrically conducting surface, said indicator system being disposed inside said enclosure, said first plate being mounted in proximity with said surface to provide a capacitive coupling between said surface and said first capacitor plate.

Claim 3

A voltage indicator system as claimed in claim 1 wherein said light producing means comprises a gas discharge tube having two terminals, said first terminal being connected to said first capacitive coupling means, said second terminal being connected to said first electrically conducting plate.

Claim 4

A voltage indicator system as claimed in claim 2 wherein saiD first capacitive means comprises a metallic electrically conducting band mounted on and at least partially encircling said insulation, said insulation acting as a capacitor dielectric, the outer surface of said conductor acting as a capacitor plate of said first capacitive means.

Claim 5

A voltage indicator system as claimed in claim 3 wherein said gas discharge tube comprises a neon lamp, said surface of said enclosure comprises a flat side, said first plate is generally flat and mounted generally parallel to said flat side of said surface, said photosensitive cell comprises a cesium cell with anode and cathode terminals, and said cesium cell and said neon lamp are disposed within a light excluding dielectric hollow chamber.

Claim 6

A voltage indicator system as claimed in claim 4 wherein said dielectric material in said chamber comprises porcelain, said chamber being generally cylindrically shaped.

Claim 7

A voltage indicator system as claimed in claim 5 wherein the resistance of said cesium cell varies with the amount of said light from said neon lamp, said amplifier-indicator being adapted to respond to said variation in resistance.

Claim 8

A voltage indicator system as claimed in claim 5 wherein said cesium cell produces electrical energy when exposed to said light, said amplifier-indicator being adapted to respond to said electrical energy.

Claim 9

A voltage-indicator system as claimed in claim 6 wherein said amplifier-indicator includes a plurality of indicator lamps, one of said lamps being connected to indicate the presence of voltage on said conductor, another of said lamps being connected to indicate the absence of said voltage.

Claim 10

A voltage-indicator system as claimed in claim 8 wherein said amplifier-indicator comprises an amplifier-indicator circuit, said circuit comprising first and second controlled, electronic valves each having a control terminal and first and second load terminals, corresponding first and second sets of biasing resistive components connected to said valves, a unidirectional electronic valve connected to each of said controlled valves, each of said unidirectional valves having an anode and cathode, a set of resistive biasing elements with two input terminals and a third terminal connected to said first controlled valve, one of said controlled valves being connected to be normally conducting and the other of said valves being connected to be normally non-conducting in the absence of said voltage and to be actuated to opposite conducting states by said cell in the presence of said cell.

Claim 11

A voltage indicator system as claimed in claim 9 wherein said indicating lamps comprising a first indicating lamp of a first predetermined color to indicate the presence of voltage on said conductor and a second indicating lamp of a second predetermined color to indicate the absence of voltage on said conductor.

Claim 12

A voltage indicator system as claimed in claim 10 wherein positive and negative sources of direct electrical current are provided, said first load terminal of said controlled electronic valve is connected to said second indicating lamp and said second load terminal thereof is connected to ground and to said anode of the associated unidirectional electronic valve, said control terminal of said first controlled electronic valve being connected to said cathode of the associated unidirectional electronic valve and to a junction point between two of said biasing resistive components associated with said first controlled electronic valve, the first of said last-mentioned resistive components being electrically connected to said third terminal of said set of resistive elements, the second of said last-mentioned resistive components being electrically connected to said cathode of said cesium cell, said first load terminal of said second controlled electronic valve being connected to said first indicating lamp and said second load terminal thereof being connected to ground and to said anode of the associated unidirectional electronic valve, said control termiNal of said second controlled valve being connected to the cathode of the associated unidirectional valve and to a junction point between two of said biasing resistive components associated with said second controlled electronic valve, one of said last-mentioned resistive components being connected at its remaining free terminal to first said load terminal of said first controlled electronic valve and to said second indicating lamp, one of said input terminals of said resistive biasing elements being connected to ground and the other of said input terminals and the free terminals of both of said indicating lamps being connected to said positive source of direct electrical current, said remaining free terminal of said second biasing resistive component associated with said second unidirectional electronic valve and said anode of said cesium cell being connected to said negative source of direct electrical current, said third terminal of said set of resistive elements being connected in such a position with respect to said elements that said first controlled electronic valve is normally conducting electrical current from said first load terminal to said second load terminal to energize said second indicating lamp and said second controlled valve is normally nonconducting current between the associated load terminals to deenergize said first indicating lamp when said resistance of said cesium cell is high when substantially no light is being produced by said neon lamp, the effective resistance of said cesium cell being reduced when light is produced from said neon lamp so that current is shunted away from said control terminal of said first controlled electronic valve to substantially prevent conduction between said first and second load terminals of said first controlled electronic valve to thereby deenergize said second indicating lamp and also to divert current into said control terminal of said second controlled electronic valve which, in turn, actuates current to flow between its said first and second load terminals thus energizing said first indicating lamp, said unidirectional electronic valves being connected to protect the associated first and second controlled electronic valves from large reverse voltage spikes.

Claim 13

A voltage indicator system as claimed in claim 11 wherein an additional controlled electronic valve is provided having a control terminal and first and second load terminals, said additional valve being interposed between said first controlled electronic valve and ground in such a manner that said second load terminal of said additional valve is connected to said second load terminal of said first controlled valve, and said first load terminal of said additional valve is connected directly to ground potential voltage, said control terminal of said additional valve being connected to said cathode terminal of said cesium cell, said control terminal of said additional valve being connected to respond to an open circuit of said cesium cell to prevent conduction between said first and second load terminals of said additional valve and also to prevent said second indicating lamp from being energized and to prevent said first indicating lamp from being deenergized regardless of the conducting state of said first controlled electronic valve.

Claim 14

A voltage indicator system as claimed in claim 12 wherein each of said controlled electronic valves comprises a solid state transistor wherein said first load terminal of each valve comprises a collector, said second load terminal of each valve comprises an emitter, said control terminal of each valve comprises a base, each of said unidirectional valves comprises a solid state diode, each of said biasing resistive components comprises resistors, and said set of resistive elements comprises a potentiometer.

Claim 15

A voltage indicator system as claimed in claim 13 wherein said first and second controlled valves comprise NPN transistors and said additional valve comprises a PNP transistor.