Title of Invention

AN IMPROVED CIRCUIT BREAKER INTERRUPTER

Abstract

The present invention relates to a circuit breaker interrupter with movable piston and metallic blast cylinder comprising leak tight enclosure filled with insulating gas at a predetermined gas pressure, fixed contact and a movable contact that are supported at the terminal faces of said leak tight enclosure, said fixed contact comprises fixed contact support, normal current carrying contacts, fixed arcing contact and integrated high voltage shield and said movable contact system comprises movable components such as movable piston, insulating nozzle, movable arcing contact, movable contact tube and link rod and a fixed metallic blast cylinder and contact support that are fixed at the bottom terminal face wherein, during the opening operation of said circuit breaker, compression of insulating gas within volume B is achieved by downward sliding movement of said movable piston against the fixed blast cylinder. This compressed gas is utilized for extinction of the arc.

Full Text

The invention relates to an improved circuit breaker interrupter and particularly to an extra high voltage puffer type gas blast circuit breaker with a movable piston and a fixed metallic blast cylinder which is used for interrupting high electric current. The interruption is effected by the use of a dielectric gas, which is compressed by the relative motion between a piston and a cylinder during an opening operation of the circuit breaker. DESCRIPTION OF THE PRIOR ART: The rapid increase in levels of short circuit currents encountered in extra high voltage transmission systems has necessitated the deplyoment of reliable and efficient circuit breakers for system protection. To achieve this end, puffer type gas insulated circuit breakers have been in use for the past few years. In this type of circuit breaker, gas is stored at a predetermined high pressure inside an enclosure. From the initial storage pressure, the insulating gas is further compressed to a higher pressure inside a compression chamber, generally termed as a puffer or blast cylinder. A relative motion between the blast cylinder and a piston effects compression during the opening operation of the circuit breaker. All these breakersdeploy one or more nozzle through which a high pressure blast of insulatinggasis blown over high temperature arc plasma that is struck between apairof contacts. The arc is surrounded by the envelope of high pressure qas and is ultimately quenched. It is observed from the present state of art, that the compression of the insulating gas in extra high voltage gas blast circuit breakers is achieved by the movement of the blast cylinder with respect to a fixed piston, the driving energy to the blast cylinder being provided by linking it with an insulated operating rod coupled to a suitable operating mechanism. The piston itself is supported and held stationary by means of a supporting column. It has been disclosed in US Patent Nos.4516006 & 4236053, wherein such type of interrupter units of the puffer type gas blast circuit breaker of the prior art deploy an enclosure containing an insulating gas, a fixed piston, a movable puffer cylinder, a fixed electrode, a movable electrode, a movable arcing contact, a fixed arcing contact and an insulating nozzle. From the embodiments mentioned in the said patents, it is found that the movable puffer cylinder slides around a fixed puffer piston, which is supported, on a stationary member. The stationary member, in turn, is mounted on a fixed section via a supporting material. The puffer cylinder, insulating nozzle and the movable contacts are connected to a driving rod supplying energy. During an opening operation, after the arc is struck between the fixed and movable arcing contacts, the insulating gas inside the puffer chamber gets compressed by the movement of puffer cylinder against the fixed piston. In order to make the principle of operation of the prior art further clear, a schematic sectional view of the fixed piston and movable blast cylinder type of circuit breaker interrupter has been described later with respect to the prior art drawing under the section "Description of prior art and preferred embodiments". SUMMARY OF THE INVENTION: Therefore the main object of the present invention is to propose a movable piston type puffer gas blast circuit breaker with improvements in both mechanical and electrical performance and with simplicity of construction as well. To achieve the main objective, the proposed gas blast puffer type circuit breaker has the new concept of a movable contact to which is attached a movable piston sliding inside a fixed metallic blast cylinder having an open end on one side, the other end of the cylinder being firmly supported. Another object of the present invention is to propose simplicity of construction, which is achieved by reduction in number of components, elimination of complicated castings and ease of assembly. Yet another object of the proposed invention is to provide an effective guide means to the movable contact assembly of the circuit breaker throughout the closing and opening stroke length. The mechanical guide arrangement allows smooth engagement and disengagement of the fixed and movable electrode system under dynamic conditions. As a result, the contact chattering and erosion there of during the making of short circuit currents are minimized. Reduced contact chattering leads to higher reliability and better electrical and mechanical life of the contact system. Further objects of the present invention is to propose an improved dielectric performance in the movable piston type gas blast circuit breaker by means of the integrated high voltage shield of the fixed contact system and the stationary blast cylinder of the movable contact system, which are shaped into two property contoured electrodes to form the inter-electrode gap. This arrangement provides an improved voltage stress distribution in the contact region. Still another object of the present invention is to provide an improved switching performance during interruption of small capacitive current. The voltage across the fixed and the movable contact systems is very high during the above duty with respect to a very small isolating gap when short arcing durations are encountered. Stresses due to such a high voltage may either cause a dielectric break down of the small isolating gap or result in surface tracking across the insulating nozzle or a combination of both. This limitation, due to constructional and functional features, if overcome by the movable piston type design. According to the present invention there is provided an improved circuit breaker interrupter comprising a leak tight enclosure filled with insulating gas at a predetermined pressure, a fixed contact and a movable contact system that are supported at the terminal faces of said leak tight enclosure, said fixed contact system comprises a fixed contact support, normal current carrying contacts, a fixed arcing contact and an integrated high voltage shield, said movable contact system comprises an insulating nozzle, a movable arcing contact, a contact support of the movable contact system being fixed at the bottom terminal face and a compressed gas volume, characterized in that, a movable piston is provided against a fixed metallic blast cylinder, compression of the insulating gas volume being achieved by a sliding downward movement of said movable piston. The nature of the invention, its objective and further advantages residing in the same will be apparent from the following description made with reference to the non-limiting exemplary embodiments of the invention represented in the accompanying drawings. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Fig. 1 is a schematic sectional view of prior art puffer type gas blast circuit breaker showing its contacts in partly open position. Fig. 2 refers to a schematic sectional view of the embodiment of the circuit breaker of the present invention showing its contacts in fully closed position. Fig. 3 (a) is the schematic sectional view of the circuit breaker of thepresent invention with its contacts in partly open state. Fig.3 (b) same as in Fig.3 (a) but in fully open state. DESCRIPTION OF THE PRIOR ART AND PREFERRED EMBODIMENTS: The schematic view of figure 1 of the prior art consists of a fixed electrode system, movable electrode system and the fixed piston (21). The fixed electrode system consists of the normal current carrying contacts (22) and the fixed arcing contacts (23). The movable electrode system comprises the puffer cylinder head (24) forming the current carrying contacts, the insulating nozzle (25), the movable arcing contact (26) and the movable puffer cylinder (27). In this arrangement, the puffer cylinder (27) slides at the periphery of the fixed piston (21) . During its travel in a closing stroke of the circuit breaker, as the head (24) of the puffer cylinder (27) moves up, its distance from the fixed piston (21) keeps increasing. Consequently, a long overhang results towards the end of the closing stroke due to the peripheral support remaining fixed at one end of the puffer cylinder (27). It may be noted from Fig.l that in these types of designs, the head (24) of the movable puffer cylinder (27) forms a part of the movable electrode system of the circuit breaker. During an opening operation of the circuit breaker while interrupting current, along with the insulated nozzle (25) and the puffer cylinder (27), the puffer cylinder head (24) also moves away from the fixed electrode system. The topmost portion of the movable electrode system and the fixed electrode system together establish the contact gap at any instant during separation of contacts or at the fully open condition of the circuit breaker. It is also observed that the puffer cylinder head (24) and movable contact system are made out of metallic component especially of smaller diameters, in comparison with the diameter of the puffer cylinder (27) and the fixed electrode system (22). The existence of such profiles in the inter-electrode space results in a constraint with respect to relieving the electric stresses between the fixed and movable electrode system. Further, for a small arcing duration during interruption of capacitive current, the electric field stress in the inter-electrode region tends to be high due to the small electrode gap between the contacts. The effect is further accentuated if field-distorting components, as described above, are present in inter-electrode gap. Fig.2 shows the sectional view of the preferred embodiment in fully closed position. It shows the over all construction of the gas insulated extra high voltage circuit breaker interrupter in which an insulating gas is filled in a leak tight enclosure (1) at a pre-determined gas pressure. The fixed contact (2) and movable contact (3) systems are supported at the two ends of the enclosure (1) with the help of terminal faces (4) and (5) . The fixed contact system consists of fixed contact support (6), normal current carrying contacts (7), fixed arcing contact (8) and integrated High Voltage shield (9) . The movable contact system (3) comprises movable components such as movable piston (12), insulating nozzle (13), movable arcing contact (14), movable contact tube (16) and link rod (15) . The other components of this system such as fixed metallic blast cylinder (11) and contact support (10) are stationary. Fig.2 refers to the fully closed position of the circuit breaker interrupter in which the movable contact system (7) as well as the movable (14) arcing contacts are in closed position. The movable piston (12) is securely attached to the movable contact tube (16) in order to facilitate their simultaneous movement during opening and closing operation of the circuit breaker. However, the fixed metallic blast cylinder (11) is firmly supported at its bottom end on the terminal connection (5) . The top end of the fixed metallic blast cylinder (11) towards the fixed contact system (2) is left open-ended. In Fig.2, the movable piston (12) is positioned at the top-open end of the stationary metallic blast cylinder (11). Compression of the insulating gas during an opening operation of the circuit breaker is achieved by downward sliding movement of the movable piston (12) against the fixed blast cylinder (11) . The volume of gas in the annular region B (Fig.2) is thus compressed and is utilized for extinction of the arc. The higher pressure insulating gas within volume B is passed through inclined multiple injection ports (17) of the movable contact tube (16) into the convergent-divergent portion of the insulating nozzle (13) inside which an arc has been struck during an opening operation of the circuit breaker due to the movable arcing contact (14) disengaging from the fixed arcing contact (8) under a current carrying state. The inclined orientation means of the gas injection ports is such as to ensure a turbulence free passage of the insulating gas into the nozzle. During the opening operation of the circuit breaker, as the movable contact system (3), coupled to the operating mechanism comes axially downwards, the piston (12) being attached to the same also descends along with the movable contact system (3) as shown in Fig.3 (a) . The piston finally comes to rest at the bottom end of the stationary blast cylinder (11) as found in Fig.3 (b) . In the same way, during a closing operation of the circuit breaker, the movable piston (12) ascends along with the movable contact system (3). Thus during both opening and closing operations, the stationary metallic blast cylinder (11) serves as a continuous and steady guide to the movable contact system (3) all through the stroke length, by this means offering a smooth descent or ascent with minimum vibration to the complete contact system under dynamic conditions. Further, the sliding movement of the movable piston (12) inside the fixed metallic blast cylinder (11) is guided around the peripheral zone of the piston (12) . The movable piston (12) acting as the guide, thus, moves along with the movable contact system (3) during a closing stroke of the circuit breaker and there by prevents excessive overhang of the movable contact system (3) during the course of its travel. The containment of the said overhang facilitates easy alignment at the instant of engagement of fixed (2) and movable (3) contact systems of Fig.2. This feature minimizes chatter of contacts and therefore results in their longer electrical and mechanical life. Fig.3 (a) refers to an intermediate position of the movable contact system (3) after a few milliseconds of the initiation of contact openinq with the movable contact system (3) having moved partly away from the fixed contact system (2). In Fig.3 (b), the movable contact system has reached the fully opened position of the circuit breaker. In contrast to the fixed piston arrangement of prior art, where the field distribution is less uniform as mentioned earlier, the constraint on diameter is alleviated as the open end of the metallic blast cylinder can be made of any required large diameters; in addition the top end of the metallic blast cylinder (11) can also be suitably profiled so that the metallic blast cylinder (11) together with fixed contact shield (9) forms an inter-electrode gap (A) with improved electric field. In effect, the movable piston arrangement offers the inherent advantage of using the fixed blast cylinder (11) itself as an effective means against over voltage stresses occurring in the contact gap region. Therefore, in both these positions, the field distribution across the open contacts of the circuit breaker is independent of the movable portion of the circuit breaker interrupter, but is governed jointly by the shape and size of the integrated high voltage shield (9) and the contoured end of stationary metallic blast cylinder (11). For this reason, the movable piston extra high voltage interrupter offers flexibility of design. This aspect is of particular benefit during interruption of small capacitive currents. Under this condition, when the arcing time encountered is very small, the contact separation achieved within that time may be insufficient to withstand the voltage across the contacts with power frequency rise; a zone of possible restrikes, therefore, exists under these conditions. The reason for these restrikes being the presence of high electrical stresses in the vicinity of the inter-electrode space, as the movable contact system (3) shifts away from the fixed contact system (2). In the preferred embodiment, the movable contac system (3) would have shifted to such a region, as shown in Fig.3 (a), that electric field stresses in the region are reduced by the time the power frequency voltage across the contacts would reach a sufficient value to cause a breakdown. Subsequent to this shifting, the field distribution in the neighborhood is influenced by contact gap (A) and therefore reduced electric field stress in the contact region is achievable. WE CLAIM : 1. An improved circuit breaker interrupter comprising a leak tight enclosure (1) filled with insulating gas at a predetermined pressure, a fixed contact (2) and a movable contact system (3) that are supported at the terminal faces (4,5,) of said leak tight enclosure (1), said fixed contact system comprises a fixed contact support (6), normal current carrying contacts (7), a fixed arcing contact (8) and an integrated high voltage shield (9); said movable contact system (3) comprises an insulating nozzle (13), a movable arcing contact (14), a contact support (10) of the movable contact system (3) being fixed at the bottom terminal face (5) and a compressed gas volume (B); characterized in that, a movable piston (12) is provided against a fixed metallic blast cylinder (11), compression of the insulating gas volume (B) being achieved by a sliding downward movement of said movable piston (12). 2. The circuit breaker interrupter as claimed in claim 1, wherein said movable contact tube (16) is provided with plurality of inclined gas injection ports (17) for the compressed insulating gas within volume B to pass through said injection ports (17) into the convergent divergent portion of the insulating nozzle (13) for extinction of an arc struck during said movable arcing contact (14) disengaging from said fixed arcing contact (8) under a current carrying state. 3. The circuit breaker interrupter as claimed in claims 1 and 2, wherein said piston (12) is movable inside said blast stationary cylinder (11). 4. The circuit breaker interrupter as claimed in claims 1 and 2, wherein said stationary blast cylinder (11) is adapted for providing guidance to said movable piston (12) during both closing and opening operations of the circuit breaker. 5. The circuit breaker interrupter as claimed in claim 1, wherein said (metallic) blast cylinder (11) along with fixed contact shield (9) forms an inter-electrode gap (A) with improved electric field, which is governed jointly by the shape and size of the integrated high voltage shield (9) and the contoured free end of said stationary blast cylinder (11). 6. A circuit breaker interrupter with movable piston and metallic blast cylinder as herein above described and illustrated with the accompanying drawings.

Documents:

1022-del-2001-abstract.pdf

1022-del-2001-claims.pdf

1022-del-2001-correspondence-others.pdf

1022-del-2001-correspondence-po.pdf

1022-del-2001-description (complete).pdf

1022-del-2001-drawings.pdf

1022-del-2001-form-1.pdf

1022-del-2001-form-19.pdf

1022-del-2001-form-2.pdf

1022-del-2001-form-3.pdf

1022-del-2001-gpa.pdf