Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
  • H01H33/02—Details
  • H01H33/04—Means for extinguishing or preventing arc between current-carrying parts
  • H01H33/18—Means for extinguishing or preventing arc between current-carrying parts using blow-out magnet
  • H01H33/187—Means for extinguishing or preventing arc between current-carrying parts using blow-out magnet comprising a hollow annular arc runner and a central contact between which a radially drawn arc rotates

Definitions

• the present invention relates generally to electrical arc interrupter devices and, more particu ⁇ larly, to an arc spinner interrupter having improved r. movable contact structure which is cooperable with a ring electrode to more efficiently extinguish an arc by decreasing the time required to initiate and effect spinning of the arc through a cool interrupt ⁇ ing gas.
• the movable contact is mounted for pivotal movement about an axis extending in a direction perpendicular to and offset from the central longitudinal axis of the ring electrode such that the movable contact is movable between a first engaged position radially inward of , the ring electrode to a second disengaged position radially outward of the ring electrode.
• an arcing ring electrode is provided which is electrically connected in series with a movable con ⁇ tact through a field coil surrounding the ring elec-
• a fixed contact is disposed internally of the ring electrode.
• the movable contact is mounted for pivotal movement about an axis extending in a direction parallel to the central axis of the ring electrode.
• Another object of the invention is to pro ⁇ vide an arc interrupter which is simple to construct and which allows somewhat greater tolerance limits 5 with respect to the spacing of the different parts of the apparatus as opposed to heretofore known devices that require very close tolerances.
• an object of the present in ⁇ vention to provide an arc interrupter in which an arc 0 is managed substantially from the time it forms be ⁇ tween the contacts until it has been extinguished in order to expedite commutation and quenching of the arc. 5 -• It is also an object of t .e invention to provide an arc interrupter in which electrostatic stress experienced in the vicinity of the angled portion of a movable contact of the interrupter is c reduced by grading the field surrounding the angled portion such that the size of the ring electrode may be reduced without adversely affecting the ability of the interrupter to withstand high voltage impulses of the type commonly experienced when lightning strikes
• an arc interrup ⁇ tion apparatus made pursuant to the invention in ⁇ cludes a fixed electrical contact and a movable elec ⁇ trical contact having an arm that may be selectively engaged with the fixed contact.
• ring electrode is associated with the contacts and has opposed ends defining a central longitudinal axis therebetween while a field coil is provided in sur ⁇ rounding relationship to the ring electrode.
• Means are provided for electrically connecting the field
• the arm of the movable contact includes an angled portion which projects from the remaining por ⁇ tion of the arm toward the electrode in a direction
• That arm is movable across the electrode along a path perpendicular to and toward the longi ⁇ tudinal axis thereof when the movable contact is shifted to interrupt current flow through the con-
• __ tacts An arc is generated between the movable con- , tact and the fixed contact when the movable contact in an energized condition is disconnected from the fixed contact.
• the arm cooperates with the remaining portion of the angled portion of the movable contact c to cause first and second electromagnetic forces to be exerted on the arc upon disconnection of the con ⁇ tacts as the arm approaches the electrode and moves across the electrode.
• the first electromagnetic force acts in a direction toward the ring electrode ln so as to encourage commutation of the arc from the fixed contact to the ring with little regard to the distance of the movable contact from the ring elec ⁇ trode.
• the second electromagnetic force acts in a circumferential direction relative to the central
• a means for grading the electrostatic field surrounding the angled portion of the arm section is also provided in the interrupter. Preferably, this
• the 20 means includes a conductor which extends toward the first axial end of the ring interrupter from the second axial end along the central longitudinal axis.
• the conductor includes an inner axial end that is separated slightly from the angled portion when the arm section is moved to a position intersecting the
• Another advantage that is realized from the construction of the present invention resides in the existence of the conductor of the grading means which acts to distribute heat developed during normal arc ⁇ ing when the movable contact is separated from the fixed contact. This distribution of heat occurs when the arc transfers to the conductor during movement of the arm section toward a position intersecting the central longitudinal axis. Once the arc transfers to the conductor, the angled portion of the arm section is permitted to cool and the heat generated by the arc is distributed in the conductor which may have a larger mass than the angled portion of the arm.
• the movable contact of the arc interrupter apparatus is mounted for pivotal movement about a pivot axis extending in a direction parallel to the central longitudinal axis of the ring electrode, and
• - includes a portion disposed generally in a plane per ⁇ pendicular to the central longitudinal axis.
• Fig. 1 is a plan view of an arc interrupter made in accordance with the present invention, where ⁇ in the movable contact is connected with the fixed 3 ⁇ contact;
• Fig. 2 is a cross-sectional side view of the interrupter of Fig. 1;
• Fig. 3 is a plan view of the interrupter with the movable contact shown as being disconnected from the fixed contact and moving across the ring electrode;
• Fig. 4 is a cross-sectional side view of the interrupter of Fig. 3;
• Fig. 5 is a plan view of the interrupter with the movable contact shown as being within the circumference of the ring electrode;
• Fig. 6 is a cross-sectional side view of the interrupter of Fig. 5;
• Fig. 7 is a plan view of the interrupter with the movable contact shown as being positioned at the central longitudinal axis;
• Fig. 8 is a cross-sectional side view of the interrupter of Fig. 7;
• Fig. 9 is a schematic view illustrating the electrostatic field in an interrupter constructed without a grading rod in place
• Fig. 10 is a schematic view illustrating the electrostatic field in an interrupter constructed with a grading rod in accordance with the present invention.
• Fig. 11 is a graph illustrating the elec ⁇ trostatic field versus the distance from the movable contact toward the ring electrode when the movable contact is located at the central longitudinal axis for both the interrupter of Fig. 9 and the inter ⁇ rupter of Fig. 10. Detailed Description of the Preferred Embodiment
• arc interrupter apparatus constructed in accordance with the present invention for use in electrical switch gear is illustrated in Fig. 1.
• the apparatus is preferably disposed within a housing filled with an insulating gas having favorable arc extinguishing properties.
• an insulating gas having favorable arc extinguishing properties.
• sulphur hexafluoride may desirably be employed as the insulating gas because of the many advantages offered by a gas of that type.
• Suphur hexafluoride is an inert, non-toxic, non ⁇ flammable gas that is an excellent dielectric.
• the gas is electronegative, it is an excellent arc extinguishing material.
• a pair of bushings preferably extend through the housing in a sealed manner and are adapt ⁇ ed to be connected to the arc interruption apparatus shown in the figures.
• One of the bushings is adapted to be connected to a fixed contact of the apparatus while the other bushing is connected to a movable contact, so that the current path from a distribution line or the like includes the bushing and the fixed contact as well as the movable contact normally ins ⁇ engagement therewith.
• the fixed contact 10 and movable contact 12 are mounted, together with a ring electrode 14, on a support 16 constructed of an insulating material sucho ⁇ as an acetal or epoxy resin.
• the fixed contact 10 includes a generally U-shaped contact element 18 retained on a fixed contact arm 20 by any suitable means such as a bolt and nut arrangement 22.
• a U-shaped contact element 18 retained on a fixed contact arm 20 by any suitable means such as a bolt and nut arrangement 22.
• S shaped biasing element 24 is sandwiched between the contact element 18 and the contact arm 20 and in ⁇ cludes two legs extending along the outer faces of -li ⁇
• the legs of the biasing element 24 press inward against the legs of the contact element 18 in order to bias the legs of the contact element toward one another for retaining ,. the movable contact 12 in engagement with the fixed contact 10 during normal current flow through the apparatus.
• An L-shaped stationary arc tip 26 (Figs. 2 and 4) is provided on the fixed contact 10 which is
• the stationary arc tip 26 is constructed of a resili ⁇ ent conductive metallic material having suitable arc
• the contact arm 20 is mounted on the support 16 by any suitable means such as by a further bolt and nut arrangement extending through the arm 20 and a wall 28 of the support 16.
• a button of ther ⁇ mally resistant material may be secured to the tip at the point at which the movable contact separates from the arc tip during interruption.
• the movable contact 12 includes an elonga ⁇ ted conductive member 30 having a hole 32 located
• the elon- __ gated member 30 includes a first arm section 36 ex- -In ⁇
• First arm section 36 of the member 30 which is pivotal about the pivot axis defined by the central axis of the pivot pin 34, can be selectively engaged with the fixed contact 10 between the legs 18 there ⁇ of.
• First arm section 36 is preferably of L-shaped configuration and includes an angled portion 44 which extends toward the ring electrode 14 from the arm section 36 in a direction generally perpendicular to arm section 36 and parallel to the central longitudi ⁇ nal axis of the ring electrode 14.
• the angled por ⁇ tion 44 may either be formed of the same piece of material as arm section 36 or may be constructed of a separate piece of material.
• the angled portion 44 may be constructed of a first hollow cylindrical piece 46 and an arc-resis ⁇ tant end piece 48, both of which are adapted to be connected to the arm section 36 by a threaded shaft or the like extending axially through the angled portion 44.
• the second arm section 40 serves as a lever through which an actuator 50 may act on the movable contact 12 to move such contact into and out of en ⁇ gagement with the fixed contact 10.
• the actuator 50 pivots the elongated member 30 about its pivot axis along a path extending between the posi ⁇ tion shown in Fig. 1, with the movable and fixed con ⁇ tacts 12, 10 engaged with one another, and the posi ⁇ tion shown in Fig. 7, whereby the movable contact 12 is disposed at the central longitudinal axis of the ring electrode 14.
• the support 16 on which the contacts 10, 12 and the ring electrode 14 are mounted is of generally annular shape including an inner radial surface 52
• the fixed contact 10 which extends axially in a direction parallel to the pivot axis of the movable contact 12.
• the fixed contact 10 is mounted on an outer radial surface 54 of the support 16 at a position circumferentially spaced from the position at which the pivot pin 34 of 5 the movable contact 12 is mounted such that the fixed contact 10 is separated from the pivot pin 34 of the movable contact 12 by a distance equal to the dis ⁇ tance between the pivot pin 34 and the angled portion 44 of the movable contact 12.
• the angled portion 44 is received and retained by the legs of the fixed con ⁇ tact element 18 when the contacts 10, 12 are in en ⁇ gagement with one another.
• the legs of the fixed contact element point in a direction generally tangent to the path of travel of the angled portion 44 of the movable contact 12.
• the arc interrupting ring electrode 14 is 0 disposed within the opening of the support 16 and includes opposed axial ends 56, 58 defining a central longitudinal axis 60 therebetween.
• the arc inter ⁇ rupting ring electrode 14 is formed of a conductive material such as copper and is of generally hollow 5 cylindrical shape.
• One end 56 of the ring is closely surrounded by the insulating material of the support 16 which is flush with one end of the ring electrode 14 and extends radially outward therefrom to a point beneath the stationary arc tip 26 of the fixed con ⁇ tact 10.
• this insulating material disposed between the fixed contact 10 and the ring electrode 14 serves two beneficial functions.
• a field coil 62 surrounds the ring elec ⁇ trode 14 and is formed by a winding of conductive strip material, e.g., copper.
• the strip material is wrapped from the inside out around the ring electrode in a clockwise direction.
• the field coil 62 is in contact with the ring electrode 14 at the inner radial wind ⁇ ing of the coil 62 and is electrically connected with the fixed contact 10 by a lead or busbar 64 extending between the outer winding of the coil 62 and the con ⁇ tact arm 20.
• the ring electrode 14 is con ⁇ nected through the field coil 62 to the fixed contact 10 such that the field coil 62 is maintained in an energized condition while current is flowing between the movable contact 12 and either the fixed contact 10 or the ring electrode 14.
• the direction of the winding of the field coil 62 is important in that the magnetic force created by current flow through the coil acts in the same direction as the direction in which the coil 62 wraps around the ring electrode 14. For example, because the winding extends in a clock ⁇ wise direction in Fig. 1, the magnetic force created by the current flow through the coil 62 also acts in the clockwise direction on any arc extending inward from the ring electrode 14 at a right angle to an inner radial surface 66 thereof.
• a reinforcing ring 68 is disposed on the 5 outer circumference of the field coil 62 and is fitted, along with the field coil into an annular stepped portion 70 of the inner radial surface 52 of the support 16.
• the reinforcing ring 68 is prefer ⁇ ably constructed of steel to give mechanical rigidity 0 to the ring electode 14 and field coil 62 and pro ⁇ tect the field coil against damage.
• the steel ring 68 retains the coil winding within a tightly confined area thus enabling the coil winding to be easily fitted on the support once the winding 5 has been assembled.
• the steel ring 68 also serves as a flux path for the magnetic field outside of the coil 62.
• the operation of the arc interruption apparatus is depicted in the serial order of the Q drawing figures and includes the physical procedure of pivoting the movable contact 12 out of engagement with the fixed contact 10.
• the forces Fl and F2 act simultaneously to cause the arc to move in the desired direction.
• the force Fl occurs as a result of the con ⁇ figuration of the first arm section 36 of the movable contact 12 which extends in a direction perpendicular to the direction in which the arc 72 would travel if no outside forces acted on the arc.
• the angle of the first arm section 36, and the known behavior of an arc, which acts as a flexible current- carrying conductor the arc is moved or bent in a direction tending to straighten the angle between the arc and the arm segment 76.
• the arc 72 is angled rela ⁇ tive to the angled portion 44 of the arm 36, the arc wants to straighten out relative to the angled por ⁇ tion 44 under the influence of the force F2 created as a result of * _he interaction of the fields gener ⁇ ated by the current 12 through the two conductors.
• the arc is moved in a direction toward the ring electrode 14.
• this second force F2 also pushes the arc toward the ring electrode 14 in order to force commu ⁇ tation of the arc to the ring electrode at an early time.
• the force F2 is substantially larger than the force Fl because of the separation which exists be- tween the arc and the elongated segment 76 of the arm section 36 as opposed to the direct contact between the arc 72 and the angled portion 44.
• the magnetic field of the coil 62 does not act on the arc during the period of movement of the movable contact 12 between the fixed contact 10 and the ring electrode 14, the arc is advantage ⁇ ously managed from the time it is created, by the forces Fl and F2 exerted on the arc as a result of the magnetic fields acting around the first arm sec- tion 36 of the movable contact 12.
• One benefit of such early management includes elongating the arc in the direction in which the arc will eventually spin once it commutes to the ring electrode 14. By pro ⁇ viding this early elongation of the arc, the length of the arc path is increased and the arc material is dispersed into the insulating gas in the housing, thus resulting in an expedited quenching of the arc.
• the force F2 because the arc is forced against the cool insulating material of the support 16 by the force F2, energy is removed from the arc by the material even before the arc is able to commute to the ring electrode 14, and gases are released by the ablation of the insulating material. These gases further facilitate extinguishment of the arc.
• the force Fl urges the arc into contact with the ring electrode 14 as soon as the movable contact 12 passes across the electrode such that early commutation of the arc is promoted.
• the stationary arc tip 26 of the fixed contact 10 is radially separated from the ring electrode 14 by a relatively short distance.
• the advantage achieved by this construction resides in the presence of insulating material between the ring electrode 14 and the fixed contact 10 which absorbs energy from the arc 72 as the arc is pushed into the insulating material by the force F2.
• the radial spac ⁇ ing between the arc tip 26 and the ring electrode 14 may be varied within a range of spacing distances without detracting from several of the primary advan- tages realized by the present construction.
• the force Fl is strongly supplemented by the force Fc of the field coil 62 which acts within the hollow interior of the ring electrode in the same direction as Fl.
• This force Fc is similar to the forces Fl and F2 in that the force Fc is caused by the interaction between the fields generated around the arc and coil winding dur- ing current flow therethrough.
• the arc acts as a flexible current carrying conductor, the arc, in attempting to straighten out the current path between the arc and the coil at each point along the circum ⁇ ference of the coil, moves circumferentially in the clockwise direction of the coil as shown in Fig. 5.
• the force Fc exerted on the arc by the coil 62 is many times greater than either of the forces Fl and F2.
• the force F2 continues to act on the arc 72 after commutation of the arc to the ring electrode 14 as a result of the continued generally perpendicular relationship between the arc 72 and the angled portion 44 of the arm 36.
• This force F2 causes the arc to penetrate the first axial end 56 of the ring electrode 14 in such a way as to facilitate spinning of the arc by the force Fc.
• the current which is an alter ⁇ nating current, passes through the first arm section of the movable contact 12 and through the arc 72 into the ring electrode 14 where it is then conducted through the winding of the field coil 62.
• the phase of the magnetic field passing through the ring is shifted relative to the phase of the current passing through the arc 72.
• the thickness and conductivity of the ring electrode 14 may be varied in order to achieve a desired phase shift of between approximately 30 and 60 degrees, such that when the current in the arc 72 approaches zero during each half cycle, the magnetic field in the ring 14 is near its peak. Because of this phase shift, the arc mate ⁇ rial continues to spin under the influence of the magnetic field in the ring even when the current through the arc approaches current zero such that when the ionized gas created by the arc and making up the arc material is spun into the arc extinguishing gas within the housing and deionized, the electroneg ⁇ ative nature of the insulating gas quickly deionizes the arc and restores its dielectric strength, thus preventing reionization of the gas. The arc is thus precluded from being re-established.
• the angled portion 44 of the arm section 36 is disposed at a distance from the pivot axis of the movable contact 12 that is approxi ⁇ mately equal to the separation distance between the pivot axis and the central longitudinal axis 60 of the ring electrode 14.
• the angled portion 44 of the first arm section 36 is co-linear with the central longitudinal axis 60 when the arm section 36 is in the position shown in Figs. 7 and 8.
• the elongated portion 76 of the arm section 36 is axially displaced from the first axial end 56 of the electrode 14 by a distance Dl which must create a dielectric strength greater than the dielectric strength at D2 between the angled portion 44 and the ring electrode 14 at the central position of the arm shown in Fig. 8. In this manner, the dielectric strength between the ring electrode 14 and the first arm section 36 is greater than between the ring electrode 14 and the angled portion 44.
• grading means are provided on the interrupter, as shown in Fig. 8, for grading the electrostatic field surrounding the angled portion 44 as the arm section 36 approaches the centered posi ⁇ tion shown in Figs. 7 and 8.
• the grading means in- eludes a conductor in the form of a hollow copper grading rod 80 that is positioned within the ring electrode 14 collinear with the central longitudinal axis 60.
• An inner axial end 82 of the grading rod 80 extends preferably to within a quarter inch of the end piece 48 of the angled portion 44 so that the gap between the grading rod 80 and the end piece 48 is minimal when the angled portion 44 is in the position shown. It is noted that although the grading rod 80 is shown as being hollow, it is possible to construct the rod of a solid conductor. Further, although it is preferred to construct the grading rod with a cross-sectional shape corresponding to the shape of the angled portion, it is possible to construct the grading rod with other shapes.
• the grading rod 80 is connected at its opposite end (not shown) to the bus 33 extending between one of the bushings and the movable contact 12 so that as the movable contact 12 separates from the fixed contact 10, the arc 72 sees the angled portion 44 of the movable contact 12 and the grading rod 80 as a single conductor. As a result, once the angled portion of the contact 12 has travelled a sufficient distance toward the position shown in Figs. 7 and 8, the arc 72 transfers to the grading rod 80 rather than dwelling on the end piece 48 of the angled portion.
• a sche ⁇ matic illustration is provided of the electrostatic field surrounding the angled portion 44 of the mov ⁇ able contact 12 when the movable contact is located at the longitudinal axis 60 of the ring electrode 14.
• a number of equ;-._ potential lines 84-110 are shown which indicate regions of common potential in the area between the angled portion 44 and the ring electrode 14.
• a schematic illustra ⁇ tion is again provided of an electrostatic field surrounding the angled portion 44 of the movable contact 12 when in the centered position.
• the grading rod 80 is included in the apparatus and the effect of the presence of the grading rod on the equal potential lines within the region between the angled portion and the ring elec ⁇ trode is also shown.
• electrostatic stress is a force which acts on the electrons of atoms within an electrostatic field and which encour ⁇ ages the electrons to separate from the atoms causing ionization.
• the electrostatic field is such that, upon the interrupter experiencing a high voltage impulse having a magnitude of, e.g. 110 kV or greater, a breakdown of the dielectric strength between the movable contact 12 and the ring electrode 14 occurs and a momentary arc forms there ⁇ between.
• a breakdown in the dielectric strength it is necessary to reduce the stress in the region surrounding the angled portion of the movable contact and such a reduction is achieved by the provision of the grading rod 80 within the ring electrode 14.
• the stress in the field surrounding the angled portion 44 of the mov ⁇ able contact 12 is represented by the amount of crowding of the equal potential lines 84-110.
• the stress is higher than in regions where the lines are more spread out.
• the stress level between any two of the equal potential lines 84-110 may be expressed as being equal to the voltage potential per unit length between those two lines in any given direction.
• the equal potential lines 100-110 adjacent the angled portion of the movable contact are relatively widely spaced from one another indicating that less stress exists in the region adjacent the angled portion 44 where the grading rod 80 is provided.
• FIG. 11 A comparison between the stress of the field existing in the construction of Fig. 9 and the construction of Fig. 10 is provided in Fig. 11.
• the stress is indicated for a specific exemplary embodi ⁇ ment of an interrupter constructed in accordance with the present invention having a ring electrode with an inside diameter of 3 inches.
• the vertical axis of Fig. 11 is labeled "FIELD” and is indicated in kV/mm, and the horizontal axis is labelled "DISTANCE" and is indicated in inches from the outer surface of the end piece 48 toward the closest point on the ring elec ⁇ trode 14.
• the stress surrounding the angled portion 44 of the movable con ⁇ tact is substantially greater immediately adjacent the angled portion in the embodiment of Fig.
• the dielectric strength between the angled portion and the ring electrode may be substantially increased by the inclusion of the grading rod in the location shown in Fig. 10. Further, such an increase in the dielectric strength is achieved without in ⁇ creasing the distance between the angled portion of the contact 12 and the ring electrode and, thus, it is not necessary to increase the diameter of the ring electrode.
• the line 116 in Fig. 11 is provided to illustrate the negative impulse limit above which breakdown of the dielectric strength occurs upon experiencing a high voltage impulse of 110 kV in the exemplary embodiment illustrated. As can be seen, the stress adjacent the angled portion exceeds this limit where no grading rod is present.
• an arc interrupter apparatus in the manner described above and set forth in the claims. For example, by providing a construction as des ⁇ cribed, wherein an arc is managed and directed in a specific manner as set forth commencing with the instant of formation thereof, it is possible to extinguish arcs consistently within a shorter time period than heretofore possible. When such consist ⁇ ent operation can be assured, it is then possible to more easily design other switch gear components which rely on the timing of the arc interrupter in their own operation. Thus, the reliability of not only the arc interrupter, but also of the entire distribution or switching system is improved by employing an arc interrupter in accordance with the invention.
• the movable contact is shown as being pivot- ally connected to the support in the figures, it is possible to move the movable contact between engaged and disengaged positions along any linear or arcuate path which extends in a direction perpendicular to the central longitudinal axis of the ring electrode so long as the orientation of the arm 36 relative to the arc remains substantially the same as that illus ⁇ trated in the preferred embodiment, such that two forces act simultaneously on the arc in two direc- tions.

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• Arc-Extinguishing Devices That Are Switches (AREA)

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Citations (12)

• 1990
  • 1990-03-06 CA CA 2070652 patent/CA2070652A1/en not_active Abandoned
  • 1990-03-06 MX MX1980590A patent/MX169041B/es unknown
  • 1990-03-06 WO PCT/US1990/001220 patent/WO1991008579A1/en active Application Filing
  • 1990-03-06 AU AU52677/90A patent/AU5267790A/en not_active Abandoned

Patent Citations (13)

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