Electricity: electrical systems and devices – Safety and protection of systems and devices – High voltage dissipation
Patent
1996-04-03
1999-05-11
Leja, Ronald W.
Electricity: electrical systems and devices
Safety and protection of systems and devices
High voltage dissipation
361117, 174140R, H02H1/00
Patent
active
059034270
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a device which is suitable for use in containing an electrical discharge arc. The device has been developed primarily for use in power generation-transmission-distribution systems, for example in protecting against the consequences of arcing due to overvoltage induced fault and other conditions, and the invention is hereinafter described in this context. However, it will be understood that the invention does have broader application, that is to any situation in which it is desired that an electrical discharge arc be contained for the purpose of sustaining the arc with minimal erosion of electrodes and/or for holding the arc substantially captive until it is extinguished.
BACKGROUND ART
Electrical discharge arcing may occur in a power transmission system as a consequence of an overvoltage condition arising from a switching event or a lightning strike, as a consequence of breakdown or bridging of insulation between conductors at different potentials and as a consequence of thermal destruction of circuit devices. In some cases arcing is accommodated (for example in use of arcing horns) for the purpose of protecting equipment against overvoltage induced fault currents until such time as the current supply is terminated by operation of circuit breakers, whilst in other cases unpredictable or, at least, unwanted flashover-type arcing occurs in or adjacent to electrical equipment. However, in all cases in which arcing is sustained it may provide a starting point for fires and/or may cause major damage to plant and equipment.
DISCLOSURE OF THE INVENTION
The present invention provides a device which is arranged for containing an electrical discharge arc and which comprises two spaced apart conductor systems, means for maintaining the conductor systems in separated relationship and means for connecting the respective conductor systems to points in an electrical circuit at different voltage potentials whereby, in the event of an arc discharge between the conductor systems, current will flow through and between the conductor systems. At least one of the conductor systems comprises at least one conductor element which is in the form of a loop which is exposed to the other conductor system and which provides a predominantly unidirectional current path whereby any arc which extends between the conductor systems will be caused to move substantially unidirectionally around the loop repeatedly in the presence of a force which has a component extending in the direction of the loop and which exists as a consequence of interaction of the arc current with the magnetic field associated with current in the loop.
In use of the arc containing device, when an arc is established between the conductor systems, current flows into the conductor element and creates an encircling magnetic field. The resultant magnetic field in turn has a component intersecting the direction of the arc current flow, and the interaction of the electric and magnetic components results in the creation of an orthogonal force which acts to induce movement of the arc along and in the direction of the loop. Thus, the arc is caused to rotate around the loop whilst extending between the two conductor systems.
High speed rotation of the arc causes adjacent air turbulence and thereby creates a cooling effect on the arc and adjacent hardware. This cooling effect helps significantly to reduce erosion of the conductor elements. Also, when the device is employed in electrical circuits having a low system voltage the thermal conditions induced by arc rotation may be sufficient to cause a self-extinguishing effect, so that the arc may be extinguished relatively quickly and without there being a need independently to break the current supply.
A further advantage flowing from rotation of the arc is that the arc-to-metal contact is over time spread over a relatively large area, thus reducing further the thermal erosion or concentration of erosion of the conductor systems between which the arc extends.
The arc containing device
REFERENCES:
patent: 3471632 (1969-10-01), Cox et al.
patent: 4451813 (1984-05-01), Hirose et al.
patent: 4467387 (1984-08-01), Bergh et al.
patent: 4667070 (1987-05-01), Zuckler
patent: 4839481 (1989-06-01), Nash et al.
Derwent Abstract Accession No. 83-727471/31, SU-A-961015-A, Tomosk Poly, Sep. 23, 1982.
Derwent Soviet Inventions Illustrated, Sec. 2, Electrical, p. 92, Jul., 1971, SU-284129, circulating Electric Arc, Volovik.
ABB Power Transmission Pty Limited
Leja Ronald W.
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