DEAD TANK TYPE GAS CIRCUIT BREAKER

Abstract: A dead tank type gas circuit breaker has a deflection member (102a) in a supporting member (10) for a fixed contact is disclosed; and the deflection member (102a) deflects flow of the hot gas, to make a region of non-direct exposure to hot gas in which area an insulator (12) for fixing the supporting member (10) is provided.

Description: FIELD OF THE INVENTION AND RELATED ART STATEMENT 1. FIELD OF THE INVENTION The present invention relates to improvements in dead tank type gas circuit breaker. 2. DESCRIPTION OF THE RELATED ART A typical conventional dead tank type gas circuit breaker is described hereafter with reference to FIG.1. FIG.1 shows a closing state thereof where a moving main contact 4 is connected to a fixed main contact 2. The fixed main contact 2 and the moving main contact 4 are provided in a dead tank 14 filled with an insulating gas, e.g., SF₆ gas. A fixed arc contact 6 and a moving arc contact 8 are provided for preventing arc between the fixed main contact 2 and the moving main contact 4. The fixed arc contact 6 and the fixed main contact 2 are supported by a supporting means 10 for fixed contact. The supporting means 10 is fixed to a dead tank 14 by a cylindrical insulator 12. FIG.2 shows a sectional view taken along line II-II of FIG.1. The supporting means 10 consists of a flange 102 and a bar 104 fixed to the flange 102 by bolts 16. Center part 104a of the bar 104 has female screw 104b in which the fixed main contact 6 is screwed for fixing. A breaking operation of the conventional dead tank type gas circuit breaker is described hereafter with reference to FIG.3. The moving main contact 4 and the moving arc contact 8 are moved in a direction shown by an arrow A. The moving arc contact 8 is disconnected from the fixed arc contact 6 after disconnection of the moving arc contact 4 from the fixed arc contact 2. Thus an arc 20 is produced between the moving arc contact 4 and the fixed arc contact 2. Simultaneously with generation of the arc 20, arc-quenching gas being compressed by movement of a puffer cylinder 18 is blown against the arc 20 by action of a nozzle 24. The blown arc-suppression gas makes highly efficient arc-suppression. Hot gas (arced SF₆ gas) having a high temperature and a degraded dielectric strength is produced by heat-dissociation of the arc-quenching gas. A large quantity of hot gas is led into an inner part 26 of the insulator 12 as shown by arrows B and C, which does not quickly spread by being obstructed the hot gas. The obstructed hot gas causes a deterioration of the dielectric strength of the insulator 12. The deterioration of the dielectric strength increases possibilities of ground fault. Further, slow spreading of the hot gas causes deterioration of recovery-efficiency of insulation, because the hot gas is filled between the fixed arc contact 6 and the moving arc contact 8. The hot gas also flows in a direction shown by an arrow D because the hot gas is filled between the fixed arc contact 6 and the moving arc contact 8. Therefore, the degradation of the dielectric strength between the fixed main contact 2 and moving main contact 4 is caused. Such disadvantage can be prevented by providing a large gap between the fixed main contact 2 and the moving main contact 4, but to provide such large gap causes an increase of size of the circuit breaker. The above mentioned circuit breakers are known from the Japanese Patent Application JP-A-57-174 817 and the Japanese Utility Model Application JP-A-60-115 428. A buffer type gas-blast circuit breaker is disclosed in EP-A-0 088 442. This circuit breaker has a fixed main contact, a fixed art contact, supporting means supporting the fixed contacts having an opening, deflection means to make an area of non-direct exposure to hot gas and an insulator for fixing said supporting means to the dead tank and being positioned in said area of non-direct exposure. SUMMARY OF THE INVENTION A purpose of the present invention is to provide an improved dead tank type gas circuit breaker which is small in size and has an increased dielectric strength. The dead tank type gas circuit breaker in accordance with the present invention comprises: fixed main contact, fixed arc contact, supporting means supporting said fixed contacts having an opening for flow of hot gas therethrough, characterized by the support means comprising a deflection means for deflecting said flow of hot gas to make area of non-direct exposure to hot gas, a rod-shaped insulator fixing said supporting means directly to dead tank and being positioned substantially in said area of non-direct exposure to hot gas. BRIEF DESCRIPTION OF THE DRAWINGS FIG.1 is the cross-sectional side view of the conventional dead tank type gas circuit breaker in the closed state. FIG.2 is the sectional view taken along the line II-II of FIG.1. FIG.3 is the cross-sectional side view of the conventional dead tank type gas circuit breaker during interruption. FIG.4 is a cross-sectional side view of an example of a dead tank type gas circuit breaker embodying the present invention during interruption. FIG.5 is a sectional view taken along line V-V of FIG.4. DESCRIPTION OF A PREFERRED EMBODIMENT The structure of a preferred embodiment of a dead tank type gas circuit breaker embodying the present invention is described in detail with reference to FIGs. 4 and 5. As shown in FIG.4, a fixed main contact 2 and a moving main contact 4 are provided in a dead tank 14 filled with an arc-quenching gas, e.g., SF₆ gas. A fixed arc contact 6 and the fixed main contact 2 are supported by a supporting means 10 for fixed contact. The supporting means 10 is fixed to a dead tank 14 by a rod shape insulator 12. FIG 5 shows a sectional view taken along line V-V of FIG.4. The supporting means 10 comprises a flange 102 and a bar 104 fixed to the flange 102 by bolts 16. Center part 104a of the bar 104 has female screw 104b in which the fixed main contact 6 is screwed for fixing. The flange 102 has a projection 102a as deflection means. Breaking operation of the dead tank type gas circuit breaker of the embodiment is described hereafter with reference to FIGs.4 and 5. The moving main contact 4 and the moving arc contact 8 are driven in a direction shown by an arrow A. The moving arc contact 8 is disconnected to the fixed arc contact 6 after disconnection of the moving main contact 4 from the fixed main contact 2. Thus, an arc 20 is produced between the moving arc contact 8 and the fixed arc contact 6. Coinciding with producing of the arc 20, arc-quenching gas compressed by movement of a puffer cylinder 18 is blown against the arc 20 by known piston like action of a nozzle 24. The blown arc-quenching gas makes highly efficient arc-quenching. The hot gas flows as shown by arrows B, C and D through an opening 10a of the supporting means 10. The hot gas quickly spreads because the hot gas is not obstructed by the insulator 12. The degradation of the dielectric strength of the insulator 12 is not caused because the hot gas is not obstructed. Therefore, the hot gas hardly flows in the direction shown by an arrow E. And furthermore, the projection 102a deflects the flow of the hot gas as shown by the arrow D, and the insulator 12 is not directly exposured to the high temperature hot gas which causes the degradation of the dielectric strength of the insulator 12. In other modified embodiments, the deflection means may be constituted with a separate member from the flange 102, or the deflection means may be provided on the bar 104. In further other modified embodiments, the bar 104 may be constituted with an integrated member with the flange 102. As has been described in detail for various embodiments, the dead tank type gas circuit breaker in accordance with the present invention is highly efficient for interruption, as a result of achieving quick spreading of the hot gas. Further, the degradation of the dielectric strength of the insulator 12 is not caused, because the insulator 12 is not directly exposured to the high temperature hot gas which causes the degradation of the dielectric strength of the insulator 12. Furthermore, the degradation of the dielectric strength between the fixed main contact and moving main contact is not caused, because only few hot gas flows through the space between the fixed main contact and the moving main contact. Thus, large distance between the fixed main contact and moving main contact is not necessary any more. Accordingly, according to the present invention, small sized and highly efficient circuit breaker is provided.

Claims: A dead tank type gas circuit breaker comprising: fixed main contact (2), fixed arc contact (6), supporting means (10, 102, 104, 16) supporting said fixed contacts (2, 6) having an opening (10a) for flow of hot gas therethrough, characterized by the support means comprising a deflection means (102a) for deflecting said flow of hot gas to make area of non-direct exposure to hot gas, a rod-shaped insulator (12) fixing said supporting means (10) directly to dead tank (14) and being positioned substantially in said area of non-direct exposure to hot gas. A dead tank type gas circuit breaker in accordance with claim 1, wherein said supporting means (10) for fixed contact has a flange (102) and a bar (104) fixed to said flange by bolts (16). A dead tank type gas circuit breaker in accordance with claim 2, wherein a projection (102a) is provided on said flange (102) as said deflection means.

Inventors: HOSOMI, MAMORU C/O ITAMI SEISAKUSHO, OKUNO, MICHIHARU C/O ITAMI SEISAKUSHO
Applicants: MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1985
Main classification: H02B13
IPC codes: H02B13, H01H33