Title of Invention

"A TWO-STAGE BLAST PROCESS FOR IMPROVING CURRENT INTERRUPTION CAPABILITIES OF HIGH VOLTAGE,HIGH PRESSURE GAS CIRCUIT BREAKERS"

Abstract

Accordingly there is provided a process to improve current interruption capability of high-voltage, high-power gas interrupters which utilizes the arc energy during peak arcing and achieves desired dielectric recovery by delivering cold gas with higher dielectric properties at interruption. An intermediate volume and a gating device are introduced for isolating hot gases from the cold gas. The invention also eliminates high pressure rise in compression / expansion volume of conventional interrupters during arcing phase. The gas vents and geometries are tuned for effective / efficient discharge of hot arc products according to the invention.

Full Text

2 FIELD OF INVENTION The present invention relates to a process for improving current interruption capabilities of high voltage, high pressure gas interrupters. BACKGROUND OF INVENTION A Circuit Breaker (CB) is primarily used to make or break normal or fault currents of high voltage installations. When the CB is in closed condition it allows conduction of electrical charge (current) through a closed electrical system (circuit) depending on the system characteristics and conditions. When current is interrupted by a circuit breaker, such as a common puffer circuit breaker, arc is struck between the arcing contacts and is quenched by a puff or blast generated within a cylinder known as puffer cylinder. The energy content of the arc depends on the current magnitude, length of the arc and similar other parameters. In conventional puffer breakers, the gas flow rate is dependent on the differential pressure between the puffer cylinder and the volume outside the cylinder. Further, it is independent of the fault current level. In self-blast interrupters, the arc energy is utilized to heat the surrounding gas and to generate gas flow for substantial interruption duration. Even though sufficient coolant gas is available in the interrupter, a poor design of gas pockets and flow channels may lead to non-availability of arc quenching medium at the right instant of interruption, which may promote substantial gap conduction and ultimate failure to interrupt. 3 The interruption capability of a gas circuit breaker depends mainly on arc cooling rate (insulation recovery rate) leading to close to interruption (near current zero for alternating current interrupters). In conventional puffer breakers, the gas flow rate is almost independent of the fault current level. In self blast circuit breakers, the gas quantity and flow rates for lower currents are insignificant due to limited arc energy. The flow of coolant , and the gas flow rate in interrupters are considered to be functions of compression volume (in case of puffer interrupters) and expansion volume (in case of self-blast) design neglecting the coupling pockets and channels. In thermally assisted gas interrupters, i.e., combination of self blast and puffer circuit breaker (refer Fig. 1), the gas availability and flow for interruption are improved. However, in most available devices, as the puffer and expansion volumes are open, mixing of high temperature gas and the cold compression volume gas is inevitable. The mixing process elevates average temperature and pressure in the vicinity resulting in slowing down of the compression process (fcr limited operating energies). The consequential reduction in gas delivery affects - recovery and interruption. Further, the gas flow obtained is at a relatively higher temperature (due to mixing) and results in corresponding poor insulation capabilities of the gas. Thus for the cited reasons, available interrupters rarely utilize full capability of the interrupting medium. 4 OBJECTS OF THE INVENTION It is therefore an object of the invention to propose a process to improve current interruption capabilities of high-voltage, high-power gas interrupters. Another object of the invention is to propose a process to improve current interruption capabilities of high-voltage, high-power gas interrupters which adapts a two-stage release of arc quenching coolant gas in a controlled and synchronized manner. A still another object of the invention is to propose a process to improve current interruption capabilities of high-voltage, high-power gas interrupters which reduces coolant requirement per unit arc energy. Yet another object of the invention is to propose a process to improve current interruption capabilities of high-voltage, high-power gas interrupters which enhances utilization efficiency of the interrupting medium. A further object of the invention is to propose a process to improve current interruption capabilities of high-voltage, high-power gas interrupters, whicn improves the current interruption capability of the interrupter. A still further object of the invention is to propose a process to improve current interruption capabilities of high voltage, high-power gas interrupter, which modifies and synchronize the gas delivery process. 5 Yet further object of the invention is to propose a process to improve current interruption capabilities of high voltage, high-power gas interrupter, which utilizes additional pockets and takes into account the response of all the flow elements in the flow-circuit. Another object of the invention is to propose a process to improve current interruption capabilities of high voltage, high-power gas interrupter, which is based on selective availability of cold gas in two stages and isolation of cold and hot zones adapting gating devices. SUMMARY OF THE INVENTION Accordingly there is provided a process to improve current interruption capability of high-voltage, high-power gas interrupters which utilizes the arc energy during peak arcing and achieves desired dielectric recovery by delivering cold gas with higher dielectric properties at interruption. An intermediate volume and a gating device are introduced for isolating hot gases from the cold gas. The invention also eliminates high pressure rise in compression / expansion volume of conventional interrupters during arcing phase. The gas vents and geometries are tuned for effective / efficient discharge of hot arc products according to the invention. BRIEF DESCRIPTION OF THE ACOMPANYING DRAWINGS The invention is described with the help of Figures 1 to 4, where: 6 Fig. 1 shows the conventional SF6 interrupters like puffer, self-blast and thermally assisted interrupter. Fig. 2 Identifies different gas zones / pockets / volumes proposed in the invention like, the Expansion, Intermediate and Compression. Fig. 3 Shows a gating device between compression and intermediate volumes according to the invention. Fig. 4 shows the proposed Two-stage blast interrupter arrangement according to the invention. DETAIL DESCRIPTION OF THE INVENTION Accordingly, there is provided a device which constitutes a two-stage blast interrupter, and operated on the basis of three strategically coupled volumes. The device is capable to achieve efficient mass flow rate at interruption. The first volume is the compression volume (01) where a piston-cylinder arrangement allows storage of cold gas and its compression during interruption by movement of the piston conventionally coupled to the operating mechanism/drive. Fresh gas is collected and retained in this volume (01) during closing operation. The second is an expansion volume (02), where the available gas is directly exposed to arc during contact separation /arcing. The third is an intermediate volume (03), where stored gas is compressed by expansion volume gas and where gas pressure rises during arcing period due to compression by the expansion volume gas and mixing (refer Fig. 2) thereof. 7 During the opening operation of the device, reduction in compression volume (01), is utilized to increase pressure (Pc) of the contained gas. The pressure (Pi) of the intermediate volume (03) at this stage is elevated by the reaction from the v gas at the expansion volume (02) which expands and compresses the intermediate volume (03) gas due to absorbed arc energy. The invention provides a conditional gating device, a non-returnable flap valve (04), between the compression volume (01) and the intermediate volume (03). The valve (04) allows gas flow from the compression volume (01) to the intermediate volume (03) only when Pc is greater than Pi. The gating device (4) is positioned between the intermediate and compression volumes (03, 01) (refer Fig. 3). The response time of the flap (4) is selected corresponding to specific rating of the interrupter / application. During non-arcing/ low energy arcs, the intermediate chamber pressure follows compression chamber pressure as the condition is satisfied and v the valve (4) permits gas flow to the intermediate volume (03). The concept and advantage of an intermediate volume (03) is introduced in the (two-blast) interrupter of the invention to facilitate isolation of cold compression volume gas from high temperature gasses present in the expansion volume (02). Two-fold advantages are drawn by the invention; first, the intermediate volume (03) is added to the expansion volume (02) improving favorably the arc energy distribution and second, the interrupter is operated in arc-assisted mode during the arcing phase. In the first stage of operation of the invented two-stage blast interrupter, pressure differential between the intermediate volume pressure and the base pressure (main volume (05)) is utilized to push the majority of arc and the arc products out of inter-electrode space. The process is largely controlled by arc 8 current and the characteristics of the intermediate volume (03). In the second stage, cold gas blast from the compression volume (01) supplements the first- stage blast until the pressure Pc and Pi equalize and activate the gating device. Timely availability of cold gas from the compression volume (01) in the inter- electrode space improves its dielectric strength and provides desired insulation recovery rate for intended interruption. Fig. 4 shows the invented two-stage blast interrupter. The present invention is unique in the sense that the interrupting medium available to the interrupter, especially the cold gas contained in the compression is selectively used. The process enables release of compressed gas only during requirement of higher dielectric recovery. It saves important cold gas resource from use during initial cleaning of the inter-electrode space. For cyclic and pulsed arcing the gating device (4) responds favorably and conserves the cold gas for better utilization later. The operation / ON time of the gating device increases with the increase of arcing period as the gas pressure in compression volume increases. 9 WE CLAIM 1. A two-stage process for improving current interruption capabilities of high voltage, high pressure gas interrupters comprising the steps of: - introducing a compression volume in which storage of cold gas and its compression during the interruption stage takes place; - introducing an expansion volume where the available gas being directly exposed to the arc during the contact separation; - identifying and introducing an intermediate volume and a strategic coupling with the compressed volume such that a stored gas being compressed by the expansion volume gas to allow gas pressure rising during the arcing stage; - providing a gating device between the compression volume and the intermediate volume such that mixing of the hot gas to the cold gas is eliminated in the compressed volume; - building-up an effective and controlled high-pressure during the arcing phase in the components of the interrupter; and - applying logic for controlling and operating the gas flow rate. 10 2. The process as claimed in claim 1, wherein the logic to be applied comprises allowing gas flow from the compression volume to the intermediate volume when PoPi, wherein Pc = pressure of the contained gas in the compression volume, and Pi = pressure of the intermediate volume. 3. The process as claimed in claim 1, wherein the pressure differential between the intermediate volume pressure and the main volume pressure is utilized at the first stage to push the arc and the arc products out of the inter-electrode space. 4. The process as claimed in claim 1 or 3, wherein the cold gas blast from the compression volume supplements in the second stage the first stage blast until the pressure Pc & Pi equalize to actuate the gating device. 5. The process as claimed in claim 1, wherein the gating device is a non- return flap valve. 6. The process as claimed in claim 1 or 5, wherein the response time of the flap is selected corresponding to the application and rating of the interrupter. 7. The process as claimed in claim 1, wherein the interrupter is enabled to operate in arc-assited mode during the arcing phase. 11 8. The process as claimed in any of the preceding claims, wherein the compressed gas is allowed to be released only during the requirement to higher dielectric recovery, and wherein the cold gas resource is reserved for use during initial cleaning of the inter-electrode space. 9. The process as claimed in any of the preceding claims, wherein the operational period of the gating device increased corresponding to the increase of the arcing period. 10. A two-stage process for improving current interruption capabilities of high voltage, high pressure gas interrupters as substantially described and illustrated in the accompanying drawings. Dated this 17th day of DECEMBER 2007 Accordingly there is provided a process to improve current interruption capability of high-voltage, high-power gas interrupters which utilizes the arc energy during peak arcing and achieves desired dielectric recovery by delivering cold gas with higher dielectric properties at interruption. An intermediate volume and a gating device are introduced for isolating hot gases from the cold gas. The invention also eliminates high pressure rise in compression / expansion volume of conventional interrupters during arcing phase. The gas vents and geometries are tuned for effective / efficient discharge of hot arc products according to the invention.

Documents:

01694-kol-2007-abstract.pdf

01694-kol-2007-claims.pdf

01694-kol-2007-correspondence others.pdf

01694-kol-2007-description complete.pdf

01694-kol-2007-drawings.pdf

01694-kol-2007-form 1.pdf

01694-kol-2007-form 2.pdf

01694-kol-2007-form 3.pdf

01694-kol-2007-gpa.pdf

1694-KOL-2007-(15-10-2012)-ABSTRACT.pdf

1694-KOL-2007-(15-10-2012)-AMANDED CLAIMS.pdf

1694-KOL-2007-(15-10-2012)-CLAIMS.pdf

1694-KOL-2007-(15-10-2012)-CORRESPONDENCE.pdf

1694-KOL-2007-(15-10-2012)-DRAWINGS.pdf

1694-KOL-2007-(15-10-2012)-FORM-1.pdf

1694-KOL-2007-(15-10-2012)-FORM-2.pdf

1694-KOL-2007-(15-10-2012)-FORM-3.pdf

1694-KOL-2007-(15-10-2012)-OTHERS.pdf

1694-KOL-2007-(15-10-2012)-PA.pdf

1694-KOL-2007-(19-07-2013)-CORRESPONDENCE.pdf

1694-KOL-2007-(19-07-2013)-FORM-1.pdf

1694-KOL-2007-(19-07-2013)-FORM-13.pdf

1694-KOL-2007-(19-07-2013)-PA.pdf

1694-KOL-2007-CORRESPONDENCE 1.1.pdf

1694-kol-2007-form 18.pdf

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