FR2774212A1 - CUT-OFF CHAMBER FOR A SELF-EXPANDING AND ROTATING ARC CIRCUIT BREAKER - Google Patents

Abstract

An interrupting chamber of a self-expanding circuit breaker in SF6 comprises a fixed contact device 16 cooperating with a moving contact, and a coil 18 for rotating the arc on an annular track 32. The fixed contact device 16 is surrounded coaxially by the cylindrical coil 18, and comprises a plurality of contact fingers 42 distributed circumferentially to delimit a hollow space for receiving the movable contact 14, each contact finger 42 comprising a composite metal structure having: - a main body 52 of copper shaped according to a cylindrical sector for the passage of the permanent current in the closed position of the movable contact 14, - an electrode 54 of refractory conductive material, brazed to the front end of the body 52, to form a contact fixed arc disposed in the vicinity of the arc rotation track 32, - and a segment 58 made of ferromagnetic material brazed to the periphery of the electrode 54 and of a part of the body 52 to obtain optimum guidance of the 'arc on runway 32.

Description

CUTTING CHAMBER FOR A SELF-EXPANSION CIRCUIT BREAKER

AND A TURNING ARC

  The invention relates to a breaking chamber for a high voltage circuit breaker isolated by a gas with high dielectric strength, and equipped with an arc extinguishing device by self-expansion of the gas, said chamber comprising: - a envelope of insulating material containing a fixed contact device cooperating with a movable contact arranged at the end of a conductive tube, which slides to slide through one of the bottoms of the envelope, moving between a closed position and a position opening of the contacts, - an electromagnetic coil for the rotation of the arc on the contact track located on the front face of the coil, said coil being integral with the fixed contact device to form a door-to-door module. - false on the opposite bottom of the envelope, - and means of communication of the chamber with the external volume of

  the envelope during the self-expansion of the gas after separation of the contacts.

  In known breaking chambers of the kind mentioned, the passage of the nominal current generally takes place in a main circuit provided with fixed and movable main contacts which separate before the opening of the arcing contacts, and which close after closing. arcing contacts. The main circuit is produced by a circuit independent of the arc circuit, and is arranged either coaxially around the coil, or offset laterally with respect to the arc circuit. The complex architecture of such a circuit breaker interrupting chamber is not suitable for a position requiring a

small footprint.

  The object of the invention is to provide an improved breaking chamber for

  a self-expanding circuit breaker that can be housed in a compact substation.

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  The interrupting chamber according to the invention is characterized in that the fixed contact device is surrounded coaxially by the cylindrical coil, and comprises a plurality of contact fingers distributed circumferentially to delimit a hollow space for receiving the movable contact, each finger of contact comprising a composite metallic structure having: - a main copper body shaped in a cylindrical sector for the passage of the permanent current in the closed position of the movable contact, - an electrode of refractory conductive material, brazed at the anterior end of the body, to constitute a fixed arcing contact disposed in the vicinity of the arc rotation track, - and a segment of ferromagnetic material brazed on the periphery of the electrode and of a part of the body, said segment being at the inside the coil to get

  optimum arc guidance on the track.

  The combined operation of the composite structure of the fixed contact device in main contact and in arcing contact in the internal dimensions of the coil allows

  to obtain a space-saving cut-off chamber.

  According to a preferred embodiment, the electrode is made from a cupro-tungsten alloy, and the segment is made from steel. The electrode and the segment of each contact finger are separated from the contact track by an axial gap of small thickness, allowing the switching of the arc for the excitation of the coil when the movable contact separates from the electrode. . Each contact finger has a rear flange mounted to hook onto a centralizing member of a stud.

current supply conductor.

  According to a characteristic of the invention, the coil is connected to the stud by copper support arms constituting spacers separated from the contact fingers by insulating plates. A curved leaf spring is inserted between each

  insulating plate and the corresponding contact finger.

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  Other advantages and characteristics will emerge more clearly from the description

  which follows of an embodiment of the invention, given by way of nonlimiting example and shown in the appended drawings in which: FIG. 1 is a sectional view of the breaking chamber according to the invention, shown in closed position of the contacts, - Figure 2 is an identical view to Figure 1, respectively during the separation of the contacts (dotted lines), and in the open position (strong lines); - Figure 3 is a perspective view of the pre-assembled module of the coil and the fixed contact device; - Figure 4 shows an elevational view of Figure 3; - Figure 5 is a sectional view along line 5-5 of Figure 4; - Figure 6 shows a perspective view of an elementary contact finger of the fixed contact device; - Figure 7 is a top view of a contact finger; - Figure 8 shows a sectional view along line 8-8 of Figure 7;

  - Figure 9 is a sectional view along line 9-9 of Figure 7.

  In FIGS. 1 and 2, a breaking chamber 10 for a pole of a high voltage circuit breaker of the self-expanding type, comprises a casing 12 made of insulating material, and filled with a gas with high dielectric strength, in particular hexafluoride sulfur SF6. The internal volume of the breaking chamber 10 contains a movable tubular contact 14 cooperating with a fixed contact device 16 associated with an electromagnetic coil 18 for rotating the arc. The movable contact 14 is disposed at the end of an elongated tube 20 of conductive material, which is capable of sliding in leaktightness through one of the bottoms 22 of the insulating casing 12. The outer end of the tube 20 is coupled to a control mechanism (not shown) intended to move the movable contact 14 between a

  closed position (Figure 1) and an open position (Figure 2).

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  The fixed contact device 16 is extended by a conductive stud 24 of cylindrical shape crossing the opposite bottom 26 in the longitudinal direction of the envelope 12, and connected to the outside to a connection pad 28 of the pole. The hollow tube 20 allows the switching chamber 10 to communicate with the external volume of the casing 12 as soon as the contacts 14, 16 are separated for

authorize gas self-expansion.

  The insulating envelope 12 is formed by the abutment of two half-shells 12A, 12B each produced by molding from a polymer resin, having good

  mechanical and thermal resistance.

  With reference to FIGS. 3 to 5, the electronic coil 18 used for extinguishing the arc comprises an axial stack of conductive turns 18A made of copper joined against each other, and electrically connected in series by means of screws. fixing 30 with interposition of inserts 18B in insulating material. The front face 31 of the coil 18 is provided with a track 32 for migration of the arc, said track 32 of annular shape having an internal diameter slightly greater than the diameter of the movable contact 14. The posterior coil 33 opposite to the front face 31 is connected to the conductive stud 24 by support arms 34 constituting copper spacers, which

  are separated from the internal fixed contact device 16 by insulating plates 36.

  Two steel washers 38, 40 are fixed by screws 30 on the rear face of the

  coil 18, after interposition of insulating washers 41.

  The fixed contact device 16 of the autoexpansion circuit breaker comprises three contact fingers 42 in the form of circular sectors, distributed circumferentially to form a hollow cylindrical contact. The internal diameter of this hollow contact corresponds substantially to the external diameter of the movable contact 14, so as to allow telescopic sliding, respectively at the start of the stroke

  opening, and at the end of closing stroke of the movable contact 14.

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  Each contact finger 42 is associated with a spring 44 in the form of a curved blade, the curved face of which bears on the insulating plate of the corresponding support arm 34. The centering of the three contact fingers 42 with respect to the longitudinal axis of the fixed contact device 16 is effected by means of flanges 46 provided at the rear of the contact fingers 42, and mounted for hooking on a shoulder

centralizer 48 of pad 24.

  The coil 18 coaxially surrounds the fixed contact device 16 with a slight annular clearance, the pre-assembled assembly forming a cantilevered module fixed to the bottom 26

  by means of a nut 50 accessible from the outside of the envelope 12.

  The structure of the fixed contact device 16 inside the coil 18 is arranged to give it a double function of fixed main contact for the passage of permanent current, and of fixed arcing contact during the separation and switching of the current in the coil 18. In FIGS. 6 to 9, each contact finger 42 is made of a composite metal structure formed by different materials assembled by brazing. The main body 52 of the contact finger 42 is made of copper, and is shaped in a cylindrical sector for the passage of permanent current when the movable contact 14 is in the closed position. A cupro-tungsten electrode 54 is soldered to the front part of the body 52 located opposite the hooking flange 46. This notch 54 fulfills the contact function

  of fixed arc for the protection of the fixed contact device 16 against the effects of the arc.

  The internal cylindrical part of the body 52 is connected to the electrode 54 by. a curved intermediate portion 56 facilitating the introduction of the movable contact 14 during the closing phase of the circuit breaker. A segment 58 of steel, or other ferromagnetic material, is brazed on the periphery of the electrode 54 and of the body 52 to ensure the guidance of the arc and a good distribution of the magnetic field generated by the coil 18 during the switching of the arc on track 32. The axial length of segment 58 is greater than that of electrode 54, and extends to the vicinity

  of the cylindrical part of the body 52.

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  The operation of the switching chamber 10 according to the invention is as follows: In the closed position (FIG. 1), the movable contact 14 is inserted inside the fixed contact device 16, and is in engagement with the body 52 made of copper for the passage of permanent current, which may have a nominal current of 630 A. The contact pressure is exerted by the springs 44 on the contact fingers 42, and the coil 18 is out of service, since all current flows through the pad 24, the contact fingers 42, and the movable contact 14 of the tube 20. The necking forces make it possible to obtain a compensation effect on the contacts for the

keep closed.

  In the event of a short-circuit current appearing, the control mechanism causes the tube 20 to slide upwards, and the movable contact 14 to withdraw towards the electrode 32. An arc arises as soon as the movable contact 14 separates from electrode 54, which is separated from track 32 by a small axial gap. The migration of the arc on the track 32 then causes the current to flow through the coil 18 and the support arms 34, with the formation of a magnetic field causing the arc to rotate rapidly around the track 32. The fingers of

  contacts 42 are then out of current.

  The heating of the arc causes the pressure increase of the SF6 gas inside the envelope 12, followed by a gas flow through the tube 20 towards the expansion volume of the tank (not shown). Arc extinction occurs as soon as

  the arc is sufficiently cooled by the gas flow (Figure 2).

  The combined operation of the fixed contact device 16 in main contact and in arcing contact, in the internal dimensions of the coil 18, makes it possible to obtain a

  very compact breaking chamber 10, and with a reduced manufacturing cost.

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Claims (9)

  1. Cut-off chamber for a high-voltage circuit breaker isolated by a gas with high dielectric strength, and equipped with an arc extinguishing device by self-expansion of the gas, said chamber comprising: - a casing (12) made of insulating material containing a fixed contact device (16) cooperating with a movable contact 14 arranged at the end of a conductive tube (20), which slides to slide through one of the bottoms (22) of the envelope (12) while being moving between a closed position and an open position of the contacts, - an electromagnetic coil (18) for rotating the arc on the contact track (32) located on the front face of the coil (18) , said coil being secured to the fixed contact device (16) to constitute a cantilevered module on the opposite bottom (26) of the casing (12), and means of communication of the chamber (10) with the external volume of the envelope (12) during the self-expansion of the gas after s contact covering, characterized in that the fixed contact device (16) is surrounded coaxially by the cylindrical coil (18), and comprises a plurality of contact fingers (42) distributed circumferentially to delimit a hollow space for receiving the movable contact (14), each contact finger (42) comprising a composite metallic structure having: - a main body (52) of copper shaped in a cylindrical sector for the passage of the permanent current in the closed position of the movable contact (14), a electrode (54) of refractory conductive material, brazed at the anterior end of the body (52), to form a fixed arcing contact disposed in the vicinity of the arc rotation track (32), - and a segment ( 58) of ferromagnetic material brazed on the periphery of the electrode (54) and of a part of the body (52), said segment being inside   the coil (18) to obtain optimum guidance of the arc on the track (32).   2. Cut-off chamber according to claim 1, characterized in that the electrode   (54) is made from a cupro-tungsten alloy. 8 2774212   3. breaking chamber according to claim 1 or 2, characterized in that the   segment (58) is made of steel.   4. Cut-off chamber according to claim 1, characterized in that the electrode (54) and the segment (58) of each contact finger (42) are separated from the contact track (32) by an axial interval of small thickness, allowing the switching of the arc for the excitation of the coil (18) when the movable contact (14) separates from the electrode (54).   5. Cutting chamber according to claim 1, characterized in that each contact finger (42) is provided with a rear flange (46) mounted for hooking on a member   centralizer (48) of a conductive pad (24) for supplying current.   6. Cut-off chamber according to claim 5, characterized in that the coil (18) is connected to the stud (24) by support arms (34) made of copper constituting   spacers separated from the contact fingers (42) by insulating plates (36).   7. Cutting chamber according to claim 6, characterized in that a spring (44) in the form of a curved blade, is inserted between each insulating plate (36) and the finger contact (42) corresponding.   8. Cut-off chamber according to claim 6, characterized in that the coil (18) is formed by the axial stack of conductive turns (18A) isolated from one another by insulating inserts (18B), and that the rear face of the coil (18) opposite the track (32) is fitted with steel washers (38, 40), the assembly   being held in place by fixing screws (30).   9. Cut-off chamber according to claim 1, characterized in that the means for   communication are formed by the hollow tube (20) of the movable contact (14).