FIELD OF THE INVENTION:
This invention relates to a multi-point arc trapping arrangement for gas insulate switchgear (GIS). More particularly, the invention relates to a fail-safe bus bar enclosure assembly for gas insulated Switchgear with multi-gear multi-point arc trapping arrangement.
BACKGROUND OF THE INVENTION:
One of the most important features in any industrial setup is to ensure absolutely safety to the operating personnel involved. In typical industrial housing switchgear, the incidence of arc fault inside the GIS Enclosure, though rare, has always endangered the safety of personnel. Due to the expanding gases and the subsequent pressure rise inside the chamber, an arc Fault Safe switchgear enclosure must withstand high internal pressure and temperature. In arc-Fault Safe enclosures, the Enclosure should be able to withstand the thermal heat and arc so that burn through can be avoided. To prevent any such causality, it is imperative to design Enclosure by maintain the thickness, capable of withstanding the stresses.
In the event of an arc fault of 25kAQ for 1 sec on a GIS enclosure, the 90° cross bend is the nearest point at which arc strike first and makes a continuous burn through in the 4mm thick Enclosure for duration 1 sec. As once the arc is initiated and holds any nearest shortest point on the enclosure it will burn it up for 1 sec, which leads to burn through and failure of Internal Arc fault test 25kA for 1 sec. Also, since it is the enclosure that faces towards some operator/personnel, any burn through in the enclosure may be potentially dangerous to the safety of the personnel. Many arcing fault protection systems employing different mechanisms have been used to address this situation.
Patent US5933308 entitled “Arcing fault protection system for an air arc switchgear enclosure” discloses an arcing fault protection system for a

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Switchgear enclosure includes a grounding device for rapidly grounding the source bus of an electrical distribution system in response to the detection of arcing faults in the system. The grounding device, which may comprise a mechanical switch, a solid-state switch or hybrid device, quickly diverts current carried on the source bus to ground to effectively extinguish arcing fault currents present in the distribution system, preventing the generation of gases at hazardous pressure and/or temperatures so as to protect the switchgear equipment from damage and to prevent injury to operating personnel.
Patent Number US141192 entitled, “Arcing fault protection system for a switchgear enclosure” discloses an arcing fault protection system for a switchgear enclosure includes a switching device for rapidly diverting current from the source bus of an electrical distribution system in response to the detection of arcing faults in the system. The switching device, which may comprise a mechanical switch, a solid-state switch or hybrid device, quickly diverts current carried on the source bus to effectively extinguish arcing fault currents present in the distribution system, preventing the generation of gases at high pressure and/or temperatures so as to protect the switchgear equipment from damage.
Patent Number US7499251 entitled “Arcing fault protection system for an air arc switchgear enclosure” discloses an arcing fault protection system for a switchgear enclosure includes an arc diverter for rapidly grounding or crow-barring the electrical distribution system in response to the detection of arcing fault currents in the system. Detection is done through a comparison of current on the main bus against the current through the feeder lines, whereby a difference in current gives a first detection signal. The first detection signal can be used directly, or AND’ed with other detection signals from optical sensors on the feeder lines, to provide the activation signal for operating the arc diverter.
Patent Number US20080170344 (Patent No. 7499251) entitled, “Arcing fault protection system for an air arc switchgear enclosure” relates to an arcing fault

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Protection system for a switchgear enclosure and includes an arc diverter for rapidly grounding or crow-barring the electrical distribution system in response to the detection of arcing fault currents in the system. Detection is done through a comparison of current on the main bus against the current through the feeder lines, whereby a difference in current gives a first detection signal. The first detection signal can be used directly, or AND’ed with other detection signals from optical sensors on the feeder lines, to provide the activation signal for operating the arc diverter.
However, the need exists, to provide an enclosure having the multi arc tapping arrangement without increasing the thickness of enclosure, to withstand the intense arcing. Also, the enclosure must be ergonomic and easy to dismantle.
OBJECTTS OF THE INVENTION:
It is therefore an object of this invention to propose a fail-safe bus bar enclosure assembly for gas insulated switchgear with multi point arc trapping arrangement.
It is further object of this invention to propose a multi-point arc trapping arrangement which can stand intense arcing.
Another object of this invention is to propose a multi-point arc trapping arrangement, which does not require increased thickness of the (GIS) enclosure and is economical.
Yet another object of this invention is to propose a multi-point arc trapping arrangement, which is ergonomic and easy to dismantle.

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A still further object of this invention to propose a multi-point arc trapping arrangement to ensure absolute safety to the operating personnel involved.
These and other objects and advantages of the invention will be apparent from the ensuing description, when read in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS: -Figure 1 is a Busbar Enclosure Assy of GIS Figure 2 is Flange with Stud Needle mounted Figure 3: Complete Assy of Busbar enclosure
DETAIL DESCRIPTION OF THE INVENTION:
Thus, according to this invention is provided a multi-point arc trapping arrangement for gas insulated switchgear (GIS).
In accordance with this invention is provided an enclosure with a multi-point arc trapping arrangement capable of withstanding extreme arching to prevent the burning through of enclosure in case of an internal arc.
By implementing this multi-point arc trapping arrangement, the same enclosure of thickness 4mm which is suitable for 25kA for 0.1 sec can be used for carrying-out the testing the Internal arc fault Test 25kA for 10 sec. A nozzle with sharp pin pointed tip facing towards and encircle the bus bar enclosure has been introduced. By this arrangement the arc will first initiate from the busbar to sharp pin pointed tip of nozzle stud.

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Also, three more earth contacts have been placed at each 90bend.mounting is same as it was done in the first earth contact by fixing M8 hardware on the enclosure. As the 90° bend corner is the only nearest earth point which is exposed to the HT bus bar conductor, this earth contact will be first attacked by arcing before it touches to the enclosure and tries to burn it.
A bus bar enclosure assembly of GIS depicted in Fig. 1. The Bus Bar enclosure (1) is made of Stainless Steel which is welded on Thick flange (2). This enclosure has 4 cross way made by the known pullout method. A stud (3) with size M10 Thread on one side is fixed on the Top flange and the other end of the stud (3) is made Nozzle type with a sharp tip. Length of each of the nozzles is adjusted at equidistance from each of the flange (4). These flanges (4) are mounted on the enclosure flange (2) by Allen Screw hardware.
Concept of using the Tip sharp end stud inside the enclosure is that at sharp point in the enclosure there will be maximum electric field Intensity which first bridges the dielectric strength of the SF6 and denotes the flashover point. Hence, the arc will tend to strike first at this point and start covering the metal Nozzle. As during High temperature, the Dielectric strength of SF6 will further reduce as well as eating up away of 1st nozzle, next flashover will be met by the nearby needle. Similarly, flashover will jump from 1st nozzle to 2nd, subsequently to the 3rd and finally it will strike the 4th nozzle. As the flashover reaches the 4th nozzle, the fault current 25kA for 1 sec will already have been withstood without increasing the thickness of the SS Enclosure. Fault current will start conducting through this Nozzle to every other Nozzles.
There are four earth contacts (5) mounted art each 90° corner of the Enclosure mounted by Allen screw hardware. Earth contact is the nearest point on which the arc will first strike before it goes to the enclosure. Two Earth Contacts are mounted at the top bend corner and two earth contacts are mounted in the two bottom corners.

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The mounting of 4 Needle studs (3) at equidistance in respect of the flanges (4) is shown in Fig. 2. One end is threaded with M10 into the depth of the top flange (2).
Projection of the Needle is perpendicular to the flange (2). Stud length is to be adjusted such that the Nozzle is the first earth tip point on which the arc will strike as it is the nearest and sharpest point and has the highest Electric Field Intensity.
Figure 3 shows the assembly of busbar enclosure (1) with a covering of flange (2) from all four sides in the SS flange (2).
The Multi point nozzle stud is used as for trapping the Arc which will initiate first and get trapped the in all four Nozzles. Arc will be first absorbed this nozzle, and only then will it go further to damage the body of the enclosure. The four-earth contact mounted on the enclosure at four opposite corners, will trap the arc as it is nearest to the HT busbar. By implementing the above, it is possible to sustain SS Enclosure by maintaining a thickness 4mm.

We claim:-

1. A fail-safe bus bar enclosure assembly for gas insulated switchgear with multi
point arc trapping arrangement, comprising:
- a bus bar enclosure (1) welded on a thick flange (2) having four cross-way;
- a stud (3) with a first threaded end, the first end being releasably attached to the thick flange (2) and a second free end configured in a nozzle shape with sharp tips;
- a plurality of flanges (4) detachably attached to the thick flange (2) via Allen screws;
- a plurality of earth contacts (5) corresponding to the number of the flanges (4) disposed at each 90° corner of the enclosure (1), wherein, at least four nozzles (3) are disposed inside the enclosure (1) to distribute the flashover in a staggered sequence from the first to the fourth nozzle (3) and exhaust the time limit of one second for the fault current of 25 kA.
2. The arrangement as claimed in claim 1, wherein the sharp tip of the nozzle (3)
sustains the maximum electric field intensify.