US3271548A

US3271548A - Contact constructions for circuit interrupters

Info

Publication number: US3271548A
Application number: US396905A
Authority: US
Inventors: Kesselring Fritz
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1963-10-11
Filing date: 1964-09-16
Publication date: 1966-09-06
Anticipated expiration: 1983-09-06
Also published as: DE1490475A1; DE1490475B2

Description

p 6, 1966 F. KESSELRING 3,271,548

CONTACT CONSTRUGTIONS FOR CIRCUIT INTERRUPTERS Filed Sept. 16, 1964 5 Sheets-Sheet 1 WITNESSES INVENTOR W 17% Frirz Kesselring W 5 52 A? M ATTORNEY p 6, 1966 F. KESSELRING 3,271,548

CONTACT CONSTRUCTIONS FOR CIRCUIT INTERRUPTERS Filed Sept. 16, 1964 5 Sheets-Sheet 2 LOW-PRESSURE GAS RESERVOIR COMPRESSOR RATCHET DRIVE HIGH-PRESSURE GAS-RESERVOIR RELEASE DIRECTION Sept. 6, 1966 F. KESSELRING 3,271,548

CONTACT CONSTRUCTIONS FOR CIRCUIT INTERRUPTERS 5 Sheets-Sheet 5 Filed Sept. 16, 1964 XD E QCMZOSz PZMKKDO FIG-6.

FIG.8.

United States Patent 8 Claims. 61. 200-148) This invention relates generally to contact constructions for circuit interrupters and, more particularly, to improved contact constructions in which there are provided both main contacts and arcing contacts for maintaining good contacting surfaces between the main contacts in the closed-circuit position of the interrupter.

A general object of the present invention is to provide an improved contact arrangement in which the contact surfaces between the main contacts are maintained free from are erosion, and arcing contacts are provided to assume the arc erosion, or pitting during the opening operation of the interrupter.

Another object of the present invention is to provide an improved contact arrangement for a compressed-gas type :of circuit interrupter in which provision is made for preventing the restriking of the arc, due to clogging elfects or back-pressure conditions in the orifice, from deleteriously effecting the main contact surfaces.

Still a further object of the present invention is the provision of an improved cont-act construction particularly suitable for use in a fluid-blast synchronous type circuit interrupter.

Yet a further object of the present invention is the provision of an improved contact construction involving main and arcing contacts, in which the inertia of rotation of the movable main contacts is reduced during the opening and closing operations thereof.

An ancillary object of the present invention is the provision of an improved contact construction for a fluidblast circuit interrupter of the nozzle type, in which the relatively stationary arcing contacts are disposed at the most constricted portion ofthe nozzle for highly-effective gas-blast action.

In U.S. patent application, filed May 21, 1964, Serial No. 369,208 by Fritz Kesselring entitled, Electric Circuit Breaker, and assigned to the assignee of the instant application, there is illustrated and described a novel type :of fluid-blast synchronous circuit interrupter, in which the energy of a rotating .mass is utilized to effect very fast opening and closing operations of the circuit interrupter. It is yet a further object of the present invention to provide an improved fluid-blast contact construction for the type of synchronous circuit interrupter disclosed in the aforesaid patent application, rendering the same adaptable for the carrying of high current values with a minimum of arc erosion on the movable main contact surfaces.

In accordance With one particular aspect of the present invention, there is provided a nozzle-type stationary contact structure including a constricted orifice opening, adjacent to which is provided circumferentially-disposed arcing contact segments, biased radially inwardly. A main contacting portion depends from the aforesaid stationary nozzle contact, and the exterior outer sides thereof cooperate with a plurality of pivotally-mounted main contact fingers. A movable arcing contact member has a cam portion movable therewith for cam actuating the main movable contact fingers into the open-circuit position prior to the separation of the arcing contact from the segmental stationary arcing contact segments. As a result, pivotal camming action is exerted upon the main contact fingers, :and any restriking of the are between the arcing contacts is prevented from occurring at a location, which would have a deleterious effect upon the contact surfaces of the main contact fingers.

Further objects and advantages will readily become apparent upon reading the following specification, taken in conjunction with the drawings, in which:

FIGURE 1 is a fragmentary vertical sectional view taken through the improved contact structure of the present invention, the contacts being illustrated in the olosed-circuitposition;

FIGURE 2 is a view similar to that of FIG. 1, but illustrating the disposition of the several contact components during the opening operation;

FIG. 3 is :a sectional view taken substantially along the line III-III of FIG. 1;

FIG. 4 is a detailed sectional along the line IV-IV of FIG. 1;

PG. 5 illustrates an application of the contact structure of FIGS. l-4 inclusive, as applied to a fluid-blast synchronous-type of circuit interrupter, the disposition of the parts being indicated in 'a condition corresponding to energization of the tripping coil, and releasing action of the trip rod having taken place, the contacts however having not as yet separated;

FIG. 6 a sectional view taken substantially along the line VIVI of FIG. 5;

FIG. 7 illustrates diagrammatically the main current, control current, and flux conditions for effecting synchronous control; and

FIG. 8 illustrates a modified-type of contact structure of the present invention, which may be substituted for that illustrated in FIGS. 1-4.

The present invention is particularly concerned with a novel contact arrangement particularly adaptable for synchronous-type circuit interrupters, but not limited thereto, being provided with main and arcing contacts and particularly suitable for an axial flow of a compressedgas arc-extinguishing medium. Preferably, although this is not a necessary limitation, the stationary arcing contact segments form the narrow cross-section of a quenching nozzle, which is opened up during the opening operation. In addition, the movable contacts preferably make contacting engagement with the outer sides of the arcquenching nozzle, so that any possible are erosion, or burning action, may occur only on the inner sides of the quenching nozzle, so that the outer surfaces thereof, which are used for making contact, remain undamaged.

In order to completely avoid arc erosion of the main contacts, there has previously been suggested the concept of using main and arcing contacts in such manner that during the opening operation, first the main contacts are opened, and then the current is transferred to the arcing contacts, following which interruption occurs only at the arcing contacts. In some constructions of the prior art, the arc is initiated between the stationary and movable arcing contacts, and then it is blown from the latter to a stationary arcing electrode, after which the arc is extin guished at the next passage of the current through zero. However, in the case of nonsynchronous interruption of a large current, it may frequently occur that a :back pressure, or clogging condition, occurs in the fluid nozzle due to the heating of the interrupting gases, whereby under some conditions, the hot arcing gases can be driven rearwardly, even against the flow of the quenching medium, so that the arc in such case is restruck between the movable main contacts, and the latter are consequently destroyed. To prevent such clogging action, or the production of high back pressure conditions, there have been proposed the use of a larger nozzle diameter, higher gas pressures, and the use of suitable arc-quenching gases which provide a minimum amount of interrupting effort.

view taken substantially In a synchronous-type circuit breaker with high-speed reclosing, in the case of an unsuccessful synchronous interruption, the conditions are fundamentally different. Of course, the are again occurs at the arcing contacts, and it may be blown against a stationary arcing electrode, so that during a normal synchronous interruption no back-pressure conditions take place. But if, as an exception, for example, due to too small contact separation distance at the moment of the passage of the current through zero value, the arc is not extinguished, then the movable contact piece of the movable contact structure is immediately reversed, and'is returned into the closed-circuit position, such action occurring at the latest even when the movable contact structure has reached its fully-open circuit position. But if, during such action, the current increases to a relatively high value, experience has shown that the are, when the current increases, has the tendency to jump from the stationary arcing electrode to the stationary contact surfaces of the main contact, which results in a large amount of arc erosion occurring at the main contact surfaces, which is undesirable.

The back-pressure, which may possibly occur, is in itself harmless, but after a reclosing operation, the hot gases should be blown away from the interrupting gap. However, this process must be completed before the next, or second synchronous interruption can be started shortly before the next current passage through zero, for only then are the most favorable conditions for are extinction during a synchronous interruption present.

More particularly, the present invention is particularly concerned with contact arrangements, particularly adaptable for synchronous-type circuit interrupters with highspeed reclosing, having main and arcing contacts, and preferably provided with an axial flow of arc-extinguishing medium. The invention is particularly distinguished by that the stationary contact pieces of the arcing-contact system form a narrow, or restricted cross-section of the quenching nozzle, which nozzle preferably widens toward the tubular stationary contact piece of the main contact in the direction of the opening movement of the circuit interrupter, so that the movable main contact fingers of the main contact structure surrounds the tubular stationary contact piece of the main contact. As a result, in the closed-circuit position, contact is established between the movable contact fingers and the stationary tubular contact piece formed at the outer surface of the latter.

With particular attention being directed to FIG. 1 of the drawings, it will be noted that the reference numeral 1 designates the stationary contact support plate having a, tubular contacting depending portion 2 associated therewith. The reference numeral 3 indicates main contact fingers arranged in a circle around the stationary contact member 2, being pivoted at the point 4 on the stationary current stud 5, and being secured against axial movement by a groove 6 formed on the contact stud 5. .As shown, contact pressure is produced by compression springs 7 so that contact pressure is exerted at the points 4, and also at the points of contact 8. During the interruption of large-amperage currents, in addition to the forces exerted by the compression springs 7, there additionally appear elect-rodynamic-type forces, which increase the contact pressure.

The reference numeral 9 indicates a stationary contact housing in which the compression springs 7 and adjustment screws 10 are preferably located. The housing 9 and the screws 10 can be made of metal, or, if desired, of insulating material. The reference numeral 11 indicates guides by means of which the forces of the compression springs 7 are transmitted to the main contact fingers 3. Attached to the main movable arcing contact is a disc-like, or camming slide piece 13 fixedly attached to the operating rod 12. Above it is arranged a star-shaped sliding contact 14, the construction of which is shown in more detail in FIG. 3 of the drawings. As shown, it transfers the current from the main contact fingers 3 to the movable arcing contact 15, which is connected with the sliding contact 14 by means of a connecting tube 16 made of a good conducting material. The reference numeral 17 indicates the stationary arcing contacts, comprising a plurality of circumferentially-disposed arcing contact segments 17a, the construction of which is more apparent from a study of FIG. 4 of the drawings.

Preferably, a stationary arcing electrode 18 is provided, to which the are 19 may terminate on the outlet side 20 of the nozzle 21 during the opening operation. During an opening operation, the are 19 is established, as shown in FIG. 2. The stationary arcing contact pieces 17a of the stationary arcing contact assembly 17 are preferably arranged within a recess 22 provided in the contact support plate 1.

With reference to FIG. 3, it will be noted that the sliding contact 14 comprises a central ring 14a, in which are mounted flexible sheet metal contacts 14b, the outer ends of which bear in sliding contacting engagement with the main pivotal contact fingers 3.

With reference to FIG. 4, it will be noted that the Z-shaped arcing contact segments 17a have their outer ends 17b pressed by compression springs 24 against the inner surface 25 of the retaining groove of the cylindrical recess 22 in the contact support plate 1. The inside ends, 17c or inner surfaces of the contact segments 17a, are preferably made of a suitable arc-resisting material, such as a molybdenum-silver alloy, for example, Preferably, they form collectively the narrowest or most constricted cross-section 26 of the quenching nozzle 21. In the closed-circuit position, as illustrated in FIG. 1, it will be noted that there exists gaps 27 between the individual stationary arcing contacts 17a through which the hot ionized gases may escape, which is particularly desirable in the case of high-speed reclosing.

The contact arrangement functions as follows: The operating rod 12 is moved downwardly by a force acting in the direction of the arrow 28. After a travel of approximately 2 millimeters, the disc-shaped cam actuator 13 comes into contact with the opposite slanted surfaces 29 of the main contact fingers 3, whereafter these main contact fingers 3 are forced radially outwardly about their contact pivot points 4, until the open-circuit positions is reached, illustrated in FIG. 2 of the drawings. Shortly after separation of the main contact fingers 3 from their contact points 8 on the tubular main contact portion 2, there follows a separation between the movable arcing contact 15 and the stationary arcing contacts 17a of the arcing contact assembly 17. The arc 19 (FIG. 2) is initiated, and is very quickly blown toward the stationary arcing electrode 18. At the synchronized opening and successfully synchronized interruption, the are 19 is extinguished .in this position without endangering the

main contacts

2, 3 in any way. However, in the case of an unsuccessful synchronous interruption, the are 19 burns generally at first between the tip of the retractable arcing contact 15 and the arcing electrode 18, as indicated by the arc location 19, but if clogging action occurs, or back-pressure conditions arise, due to a relatively high current being interrupted, then the are 19 can move back into one of the

positions

30, 31, 32 or 33 indicated by the dotted lines in FIG. 2. If the inside surface 35 of the tubular arcing contact 2 were also the contact surface of the main contact, as is generally the case with conventional contact constructions, then a considerable arc-erosion action would occur at the

main contacts

2, 3, which would result in an increase of contact resistance in the closed-circuit position of the interrupter. But according to the present invention, the contact points, or surfaces 8 arelocated on the external surfaces of the tubular main contact member 2, and, therefore, as confirmed by experiments, no arc can restrike at the location 37 (FIG. 2) even during a persistent back-pressure condition, because it finds much more favorable conditions at the locations 30-33. The arcs 30-33 now extinguish as soon as the movable arcing contact 15 again enters into contact with the stationary arcing cont-act 17. As a result, it is seen that the hot gases, which have accumulated inside of the main arcing ring contact 2, can escape through the gaps 27 between the contact pieces 17a of the stationary arcing contact assembly 17 in several milliseconds, so that the contact system is again ready for the next following synchronous interruption, and is cleared of all hot and ionized gases.

During the closing operation, first contact is established between the movable arcing contact 15 and the stationary arcing contact 17. Because here a sliding contact is essentially involved, practically no chattering of the contacts is encountered. Shortly before reaching the final closed-circuit position, the main contact fingers 3 strike the contact points 8. As a result, under some circumstances, a slight contact chattering can occur, but it is harmless because the circuit is already closed through the

main arcing contacts

15, 17. It can be seen from an inspection of FIG. 1, that in the closed-circuit position, no additional forces are needed to produce a sufficiently low contact resistance, whereby the operating mechanism is simplified.

FIG. 5 illustrates an application of the improved contact construction of FIGS. 1-4 to a fluid-blast synchronous-type circuit interrupter, generally designated by the reference numeral 70. As shown, the synchronous-type circuit interrupter 70 includes a casing 71 enclosing a high-pressure region 72, which is maintained at high pressure by a conduit 74 supplied from a high-pressure gas reservoir chamber 76', preferably filled with sulfurhexafiuoride (SP gas at a high pressure, say of 250 p.s.1.g.

On the downstream side of the nozzle exhaust 21 there is provided a relatively low-pressure region 82 communicating by a conduit 84 with a relatively low-pressure gas reservoir 86. The low-pressure gas reservoir 86 also communicates by way of a conduit 88 to a passageway 90 extending through the lower terminal stud 92 into a region 94 to one side of a two-way valve 96, the operation of which will become more apparent hereinafter.

To effect opening and closing operations of the separable contact structure, there is provided a connection 100 linking the operating rod 12 to a pair of

doubleended levers

102, 104 pivotally mounted, respectively, on

stationary pivots

106, 108. The ends of the

levers

102, 104 are pivotally connected, as at 110, 112, to ratchet

levers

116, 118 of a synchronous-control device, generally designated by the reference numeral 120.

The synchronous control device 120 includes a pair of pivotally-mounted actuating levers 122, 124 pivotally mounted, respectively on stationary pivots 126, 128.

As shown in FIG. 5, the movable contact 15 is directly connected with a metal cylinder 130 through a plurality of 132 contact fingers 134. The ratchet levers 116, 118 are pressed by springs 140 and 142 against

pins

144 and 146 respectively. A rotating mass 150 is provided at its circumference with a toothed rim 152. The mass 150 is rotated in the direction of the arrow 154 by movement of an insulating rod 156 through a

ratchet drive mechanism

158, 160, 162. The insulating rod 156 can be driven, for example, by a compressed gas mechanism 164 arranged at ground potential.

The synchronizing device 120 includes a cylinder 170, a piston 172, a spring 174, and the two-way valve 96, which is coupled with a movable conductor 176 by means of a rod 178. At the return stroke of the piston 172 a piston rod 180 becomes positively connected with a curved lever 182 in a manner explained hereinafter, whereby the actuating lever 122 rotates in a clockwise direction about its pivot point against a spring 186. A release rod 188 may be operated by hand 190 or from an overcurrent protective OL, as shown.

The movable conductor 176 is connected in the secondary circuit of an air-gap current transformer 194 with air gaps 196. The transformer 194 is energized by current i flowing through the terminal bolt 92. The reference character 200 designates a magnet system which is also energized by the current i and in the air gap 202 of which moves the conductor 176. A secondary winding 206 of the current transformer 194 is connected, by means of

flexible conductors

208 and 210 with the conductor 176 which is movable about its pivotal support 212. The upper end of the conductor 176 is connected with a lever 2 14 by means of a link 216. The conductor 176 and the lever 214 are kept in the position shown by a spring 220.

The synchronized breaker shown in FIGS. 5 and 6 functions as follows: When the current i is increasing (see FIG. 7), the current transformer 194 produces in the conductor 176 a current i which is shifted by approximately with reference to i and which produces together with induction or field strength B in the air gap of the magnet system 200 a force F according to the formula where l is the effective length of the conductor 176. From t to Z (see FIG. 7) this force is negative, and moves the conductor 176 instantaneously to the right against the stop 222 formed by the wall of the cylinder through the bottom 130a of which the conductor 176 extends. In FIG. 7 this movement of the conductor 176 is shown by the line s. At the time t the force F reaches the zero value; but already before this, the conductor 176 has moved back again into the position shown under the effect of the spring 220 and remains there during the time t to because then it is pushed against the stop by the force F.

By means of the rod 178 the movement of the conductor 176 opens the valve 96 on the side of the space which is under high pressure. The compressed gas enters behind the piston 172 which then moves to the right against the spring 174 in proportion to the increasing pressure. When the maximum of the current is reached, the valve 96 is closed on the high-pressure space by the conductor 176, and it is opened on the low pressure side 94. This results in movement of the piston 172 under the force of the spring 174 to the left. The travel of the piston rod 180 solidly connected with piston 172, is shown in FIG. 7 by x. When the distance x is exceeded, the curved lever 182 turns in the counterclockwise direction and, therefore, becomes positively connected at the stop 182a with the piston rod 180 on the return travel of the latter. The lever 122 is rotated clockwise by the lever 182 and thus engages the lever with the toothed rim 152 of the rotating mass 150. The movable contact 15 is brought into the open position at a great speed by the kinetic energy of the mass through the lever 102.

It can be seen from FIG. 7 that the travel x of the piston rod is the longer, the longer is the time 1-. 'If the travel x which corresponds to the lowest value of r at which a release just still takes place, is not reached, then the lever 182 remains in the position shown. As can be seen from FIG. 7, at longer half-waves the release takes place always at the same interval A! from the current zero.

However, the described opening procedure can take place only when the release rod 188 is in the release position as shown. If it is moved to the right until it is in contact with the perpendicular part 182a of the curved lever 182, then also in the case of an overcurrent, releasing is not possible because the curved lever 182 cannot then rotate. Otherwise, the synchronized operation always takes place in orderly manner by the release rod 188 when the release is unblocked. The release is independent of the time instant when the release rod 188 is moved to the left.

In the case of a multipole breaker there occurs a possibility that due to some circumstances the extinguishing does not take place in the intended current zero or that the so-called re-strike occures. Then the breaker must be brought instantly into the closed position, whereby a provision must be made to the effect that the synchronized opening can take place again at the next current zero. With the arrangement shown in FIG. this happens in the following manner: When the current i again increases, the conductor 176 moves, as previously explained, to the right and thus the lever 124 is rotated in a counterclockwise direction. In the open position of the contact member 15, a lug 230 on the lever 118 is located opposite the upper end of the lever 124 so that when the latter is rotated, the lever 118 engages with the toothed rim 152, and the breaker is brought again into the closed position, in which it is held by the frictional engagement of the contact fingers 14b. Such friction also holds the breaker in the open position.

To close the breaker, the closing button 240 may be manually pressed to energize solenoid 240a and rotate bell-crank 24% in a counterclockwise direction about stationary pivot 2400. This will force a closing rod 240d to engage the ratchet lever 118 and so close the

contacts

15, 17.

FIG. 8 illustrates a modified-type of contact construction 234 wherein an umbrella-type operating arrangement is utilized. The levers 250- en-gage with their upper ends 250a in a seat 252 and when in the closed position they are seated with a clearance so that there is guaranteed a positive contact between the contact finger 3 and the tubular contact piece 2 of the main contact.

An important advantage of this contact arrangement, especially in the case of a synchronized circuit breaker, consists of that, that the relatively large mass of the contact fingers 3, due to current-carrying capacity during the course of travel enters into the picture as effective mass of only approximately 5 to 8%, because of the rotating motion in conjunction with the wedging action.

It can be seen that the contact system according to this invention combines the following advantages: small eifective mass, no danger to the contact surface of the main contacts from the are especially in case of backpressure, retractable contact is practically without chatter, additional dynamic pressure being present on the contact fingers of the main contact, no contact force acting in the direction of opening, simple construction and easy replacement of the retractable contact which is subject to erosion.

Although there has been illustrated and described specific contact arrangements, it is to be clearly understood that the same were merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art, without departing from the spirit and scope of the invention.

I claim as my invention:

1. Separable contact structure for a circuit interrupter including means defining a conducting nozzle portion having an outlet portion and a tubular depending main contact portion on the upstream side thereof, a plurality of circumferentially-disposed pivotally-mounted contact fingers making main contacting engagement with the external portion of said depending contact portion, a movable arcing contact having a cam actuator for engaging the main contact fingers and eifecting opening operation thereof, means providing a relatively stationary arcing contact structure within said nozzle portion, means separating the movable arcing contact from the stationary arcing contact following separation of the main contact fingers from the external sides of the depending main contact portion, whereby restriking of the extinguished arc will take place at a location remote from the main contacting area.

2. The combination according to claim 1, wherein fluid-blast means are provided for directing a blast of radially inwardly-directed fluid past the main ring-shaped contact portion and through the nozzle portion to the outlet side thereof.

3. The combination according to claim 1, wherein a stationary arcing electrode is disposed on the outlet side of the nozzle portion.

4. In combination, a relatively stationary conducting nozzle portion having a relatively stationary arcing contact adjacent the restricted portion thereof, a depending ring-shaped main contacting portion, a plurality of pivotally-mounted main contact fingers making contacting engagement with the external sides of said main ring-shaped contacting portion, a movable arcing contact having a cam actuator for camming the main contact fingers into an opening operation, means effecting separation between the movable arcing contact and the stationary arcing contact following previous separation between the main pivotally-mounted contact fingers and the external sides of the tubular main contact portion, whereby restriking of the established arc will occur at a place remote from the main contact area.

5. The combination according to claim 4, wherein a star-shaped movable sliding contact is affixed to the movable arcing contact and makes sliding contacting engagement with the plurality of main pivotally-mounted contact fingers.

6. A synchronous-type fluid-blast circuit interrupter including relatively stationary nozzle means defining a stationary arcing contact adjacent the restricted portion of the nozzle, a plurality of pivotally-mounted main contact fingers, a movable arcing contact separable from the stationary arcing contact to establish an arc, said nozzle portion having a depending main ring-shaped contact portion, the ends of the pivotally-mounted main contact fingers making contacting engagement with the external sides of the ring-shaped main contact, and cam actuator means movable with the movable arcing contact for camming the pivotally-mounted main contact fingers to their open position.

7. The combination according to claim 6, wherein a stationary arcing electrode is disposed on the downstream side of the nozzle outlet.

8. In combination, a relatively stationary segmentaltype arcing contact structure having a depending ringshaped main contact portion, a plurality of circumferentially-disposed main contact fingers, means pivotally mounted said main contact fingers so that the ends thereof contact the external sides of the ring-shaped main contact portion, a movable arcing contact having a cam actuator for actuating the movable main contact fingers to the open position, and a movable generally star-shaped sliding contact movable with the movable arcing contact and making sliding engagement with the sides of the several main contact fingers.

References Cited by the Examiner UNITED STATES PATENTS 1,898,901 2/1933 Ruppel 200-148 2,679,567 5/ 1964 Kradel 200-146 FOREIGN PATENTS 566,432 12/ 1932 Germany. 514,759 11/ 1939 Great Britain.

ROBERT K. SCHAEFER, Primary Examiner. R. S. MACON, Assistant Examiner.

Claims

1. SEPARABLE CONTACT STRUCTURE FOR A CIRCUIT INTERRUPTER INCLUDING MEANS DEFINING A CONDUCTING NOZZLE PORTION HAVING AN OUTLET PORTION AND A TUBULAR DEPENDING MAIN CONTACT PORTION ON THE UPSTREAM SIDE THEREOF, A PLURALITY OF CIRCUMFERENTIALLY-DISPOSED PIVOTALLY-MOUNTED CONTACT FINGERS MAKING MAIN CONTACTING ENGAGEMENT WITH THE EXTERNAL PORTION OF SAID DEPENDING CONTACT PORTION, A MOVABLE ARCING CONTACT HAVING A CAM ACTUATOR FOR ENGAGING THE MAIN CONTACT FINGERS AND EFFECTING OPENING OPERATION THEREOF, MEANS PROVIDING A RELATIVELY STATIONARY ARCING CONTACT STRUCTURE WITHIN SAID NOZZLE PORTION, MEANS SEPARATING THE MOVABLE ARCING CONTACT FROM THE STATIONARY ARCING CONTACT FOLLOWING SEPARATION OF THE MAIN CONTACT FINGERS FROM THE EXTERNAL SIDES OF THE DEPENDING MAIN CONTACT PORTION, WHEREBY RESTRIKING OF THE EXTINGUISHED ARC WILL TAKE PLACE AT A LOCATION REMOTE FROM THE MAIN CONTACTING AREA.