Title of Invention	AN SF6 PUFFER INTERRUPTER
Abstract	The present invention relates to an SF6 puffer interrupter with an improved profile, comprising: a PTFE nozzle (5) having a throat region (T) surrounding an annular clearance (7) between a fixed arcing contact (3) and said nozzle (5); characterized in that said throat region (T) is provided with gas enamels (8,8*; 9,90 for fester arc-heat dissipation.

Full Text

FIELD OF THE INVENTION The present invention relates to an SF, puffer interrupter. In particular it relates to an SF, puffer interrupter with an improved profile for nozzle and/or arcing electrode for better thermal and dielectric capabilities. BACKGROUND OF THE INVENTION Sulphur hexa-fluoride (SF6,) circuit breakers generally have two pressure systems with a closed gas circuit fo arc quenching. In the single pressure system of a puffer type (SF6,) circuit beaker the compressor of a two presure system is not required and requirement for other components is also reduced substantially. In single pressure puffer (SF6.) interrupter for high voltage circuit breakers of 6.6KV to 400 KV rating, poly tetra fluorb ethylene PTFE nozzles are used. When the moving arcing contact separates from the fixed arcing contact an arc is struck between the two electrodes in the throat region of the nozzle. An annular clearance is maintained in the throat region between the nozzle and the arcing contacts for considerations like interference free movement during opening and closing operations of the circuit breaker. The surfaces of the components, the nozzle and the electrodes are given a smooth finish in order to help reduce the charge concentration and electrical stresses. The tip of the fixed arcing electrode is made from W-Cu matrix for withstanding higher arc temperatures and to result in low contact erosion. The tips of the fixed arcing contacts are given a hemispherical shape for uniformity of electrostatic fields. In the interrupter,as described above,during peak arcing the fully grown arc may block or restrict the flow of gas through the annular space between the fixed arcing electrode and the nozzle. This reduction in gas flow critically affects the arc cooling and the interrupters capability to handle higher arc current. The arc burns in a single block mode with high core temperature signifying intense radiation. Because of this higher arcing temperature during blocking the nozzle wall material gets abnormally heated leading to ablation. The evaporation/ablation of nozzle material may cause contamination. Ablation of the PTFE and nozzle erosion of the arcing contact results in loss of optimum performance and failure of the interrupter. SUMMARY OF THE INVENTION 1. Thus one object of the present invention is to provide an (SF,) puffer interrupter without blockage or restriction to gas flow over the arc during peak arcing. 2. Another object of the present invention is to lower the thermal time constant for the interrupter and better the interrupting performance. 3. One more object of the present invention is to lower the core temperature of the arc and radiation therefrom. 4. Yet another object of the present invention is to specifi- cally improve the arc heat removal rate in a puffer interrupter by splitting the arc into two or more parts with divided arc energy content. 5. A further object of the present invention is modifying the gas flow and lengthening the arc for better and more effective arc cooling. These and other objects of the present invention are achieved by providing arc-heat dissipation means for maintaining the gas flow over the arc during peak arcing without restriction or blockage. The arc-heat dissipation means in the form of channels are provided on the nozzle and/or the arcing electrode in the throat region. Gas flow is induced through the channels for cooling the arc during normal and peak arcing phases. The gas channels provided help in maintaining a finite flow of the cooling gas over the growing arc. The cool gas flow over it pinches the arc at the surfaces of contact or the outer periphery of the arc. The contact surface grows radially towards the arc core with passage of time.When two such channels are provided, the arc is split into two parts. The arc can be divided into a number of smaller arcs by providing two or more number of such flow channels. The arc can thus bum in split mode with divided arc energy content in smaller arcs, lowering the core temperature and radiation. By providing spiral channels on the nozzle or the electrode, the arc can be lengthened for further towering the operating temperature and radiation in the arcing zone. The present Invention thus provides an SF6 puffer interrupter with an improved profile, comprising: a PTFE nozzle having a throat region (T) surrounding an annular clearance between e fixed arcing contact and said nozzle ; characterized in that said throat region (T) is provided with gas channek for faster arc-heat dissipation. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS. The accompanying drawings, Figures l(a) and l(b) show (SF0) puffer interrupter in Closed'and partially open'petitions respectively. Figure 2 (a) shows the conventional nozzle and the fixed arching contact. Figures 2(b) and 2(c) show the nozzle of the present invention respectively with two straight and two spiral channels. Figures 2(d)and 2(e) show the fixed arcing contact of the present invention respectively with two straight and two spiral channels. Figures 3(a) shows the cylindrical arc without any channels. Figures 3(b) to 3(d) show the split arc with 2, 3 and 4 channels respectively. DETAILED DESCRIPTION The invention will now be described in detail with the help of the accompanying drawings. Figures l(a) and l(b) show an (SF6,) puffer interrupter in 'CLOSED1 and 'PARTIALLY OPEN' positions respectively. As shown in figure l(b) when the arcing contacts 3 and 4 are separated an arc is drawn between the contacts in the throat region T of PTFE nozzle 5. The size and shape of the arc is determined by the magnitude of current and the cooling offered by the(SF^) gas flowing over the arc. The flow of (SF6,) gas and the flow pattern is regulated by the nozzle 5 surrounding an annular clearance 7 between the nozzle 5 at the throat region T and the fixed arcing contact 3. During peak arcing condition of the interrupter,the arc is fully grown, the gas flow can be restricted or blocked. The reduction in gas flow affects the arc cooling critically affecting the capability of the interrupter. In order to prevent this restriction/blockage gas flow taking place during peak arcing, an efficient arc-heat dissipation means 8 can be provided as shown in figure 2(b). Figure 2(a) shows the conventional nozzle 5 and the fixed arcing contact 3 without the arc-heat'dissipation means. The arc-heat dissipation means 8 comprises gas channels 8,8' which can be provided on the nozzle 5 at the throat region T as shown in Figures 2(b) and 2(c) . The gas channels 9,9' can also be provided on the fixed arcing contact 3 as shown in Figures 2(d) and 2(e). The arc-heat dissipation means in the form of gas channes help in lowering the thermal time constant of the interrupter resulting in better interrupting performance. The gas channels formed on the surface of the nozzle 5 and the fixed arcing electrode 3 can be of rectangular or semi-circular cross section as shown in Figures 2(b) to 2(e). The gas channels provided on the nozzle 5 and/or the fixed arcing contact can be straight channels 8,9 as shown in Figures 2(b) and 2(d). Gas channels 8' 9' can also be provided in a spiral form as shown in Figures 2(c) and 2(e). The spiral gas channels help in lengthening the arc by modifying the gas flow which results in further lowering of the operating temperatures and radiation in the arcing zone. Figure ,3(a) shows the nozzie wall 10 and the cylindrical arc 11 of the prior art interrupter in cross-section. The present invention provides an arrangement by which the cylindrical arc 11 can be divided into a number of smaller arcs by using two or more number of channels. With the splitting of the arc in this manner the arc can burn in a split mode with divided arc energy content in the smaller arcs. This can further lower the core temperature and radiation. Figure 3(b) shows two gas channels 8 provided on the nozzle wall 10 of the PTFE nozzle 5, splitting the arc in two segments A1 and A2 In a similar way the arc can be split into 3 or more sequents by providing a number of such flow channels 8, as shown in figures 3(c) and 3(d). Thus, the interrupter thermal time constant can be further lowered by profiling the nozzle and/or the fixed arcing contact in such a way that the arc is split in segments and the arc heat is connected effectively during arcing. The above description of the present invention with different embodiments, should be considered as illustrative and not restrictive. It should be understood that the invention may be embodied in other specific forms by one skilled in the art without departing from the spirit and essential characteristics described. WE CLAIM 1. An SF6 puffer interrupter with an improved profile, comprising: a PTFE nozzle (5) having a throat region (T) surrounding an annular clearance (7) between a fixed arcing contact (3) and said nozzle (5); characterized in that said throat region (T) is provided with gas channels (8, 8', 9, 9,) for faster arc-heat dissipation. 2. The puffer interrupter as claimed in claim 1, wherein said gas channels are formed on the nozzle wall (10). 3. The puffer interrupter as claimed in claim 1 or 2 wherein said gas channels are formed on the surface of the nozzle (5) and/or the fixed arcing contact (3). 4. The puffer interrupter as claimed in any of the preceding claims wherein said gas channels are of rectangular or semi-circular cross-section. 5. The puffer interrupter as claimed in any of the preceding claims wherein said gas channels formed on the surfaces of the nozzle (5) and/or the fixed arching contact (3) are straight channels (8, 9). 6. The puffer interrupter as claimed in any of the preceding claims wherein said gas channels formed on the surfaces of the nozzle (5) and/or the fixed arching contact (3) are spiral channels (8'; 9,). 7. The puffer interrupter as claimed in claim 1 wherein between two to four gas channels (8) are provided on the nozzle wall (10) for splitting the arc into two or more segments. 8. An SFe puffer interrupter with an improved profile substantially as herein described and illustrated in the accompanying drawings.

Documents:

0779-del-2003-abstract.pdf

0779-del-2003-claims.pdf

0779-del-2003-correspondence-others.pdf

0779-del-2003-correspondence-po.pdf

0779-del-2003-description (complete).pdf

0779-del-2003-drawings.pdf

0779-del-2003-form-1.pdf

0779-del-2003-form-19.pdf

0779-del-2003-form-2.pdf

0779-del-2003-form-3.pdf

0779-del-2003-gpa.pdf

779-del-2003-Correspondence-Others-(25-04-2011).pdf

779-del-2003-Form-15-(25-04-2011).pdf

779-del-2003-GPA-(25-04-2011).pdf

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