US3504142A

US3504142A - High voltage electric switch

Info

Publication number: US3504142A
Application number: US673675A
Authority: US
Inventors: John P Mckinnon
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1967-10-09
Filing date: 1967-10-09
Publication date: 1970-03-31
Anticipated expiration: 1987-03-31
Also published as: FR1586291A; GB1177907A; JPS5011079B1

Description

March 31, 1970 J. P. M KINNON HIGH VOLTAGE ELECTRIC SWITCH 1 m 8 MM 8m 9m 8 h Ln RNA 1 m 3 mm t 8 e m m e m 6 M9 2 N9 w Q 5 m E Th E an: v Q Lfi w -o 3 Q. Ma 8 B N QC 8 A 8 7 m g 6 N 9 nkulllllll R c o 7 b1 d -01 m S n u Q J. P. M KI NNON HIGH VOLTAGE ELECTRIC SWITCH March 3 1, 1 970 2 Sheets-Sheet 2 Filed Oct. 9, 11967 United States Patent 3,504,142 HIGH VOLTAGE ELECTRIC SWITCH John P. McKinnon, Monroeville, Pa., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 9, 1967, Ser. No. 673,675 Int. Cl. H01h 31/02; H01b 17/42 US. Cl. 200-48 7 Claims ABSTRACT OF THE DISCLOSURE This invention relates to high voltage electric switches and more specifically to high voltage switches which are particularly suitable for use as grounding switches. A switch blade is supported on a rotatable shaft to move between open and closed positions with respect to an associated stationary contact means which is mounted on and between a pair of corona shielding members which form the only current carrying path between the contact means and a terminal means which extends transversely with respect to the blade. The shielding members are shaped so that when current flows therethrough, magnetic fluxes are produced which interact with the current in the switch blade to assist in retaining the switch blade in the closed position with respect to the contact means.

In electric power systems, high voltage disconnecting switches are employed to isolate transmission lines and high voltage electrical apparatus in order to permit the inspection, maintenance or repair of such apparatus or for other reasons. In order to prevent injury to maintenance or operating personnel in the event that the apparatus should be inadvertently reenergized, it is common practice to provide auxiliary grounding switches to ground the transmission line and thus to drain off any static charge that may remain after anisolating operation of the associated high voltage disconnecting switch. In the construction of grounding switches for use with high voltage disconnecting switches, the grounding switch includes a movable switch blade which may be actuated to engage a relatively stationary contact assembly which is normally mounted at the top of one of the insulator stacks of the associated disconnecting switch with the current carrying path which includes the switch blade and the contact assembly of the grounding switch involving a. generally right-angle bend or turn. A problem arises if the parts of the high voltage disconnecting switch which are grounded after the associated grounding switch has been closed should be inadvertently re-energized to thereby cause short-circuit current to fiow through the switch blade and the contact assembly of such a grounding switch. This is because the currents which flow during such a short circuit condition produce relatively large magnetic forces which act on the switch blade of the grounding switch and tend to blow the switch blade out of engagement with the associated contact assembly. If the swit'chblade of a grounding switch should separate or part from the associated contact assembly during such an operating condition before an associated automatic circuit breaker acts to interrupt the short-circuit current, the arcing which results between the switch blade and the contact assembly of the grounding switch may be sufficient to burn up or destroy at least certain parts of the grounding switch. One possible solution to this problem is to make the switch blade of the grounding switch sufficiently rigid and the operating mechanism of the grounding switch sufficiently strong from the mechanical standpoint to hold the switch blade of the grounding switch in the engaged position by relatively large mechanical forces. Where the grounding switch is to be used with relatively high voltage disconnecting switches, such as those rated 230 kv.

3,504,142 Patented Mar. 31, 19 70 or above, this solution may require extremely large and heavy mechanical parts in the design of the grounding switch. Another possible solution which might prevent the separation of the switch blade and the contact assembly of the grounding switch during the described operated condition is to provide an operating mechanism for the grounding switch which actuates some secondary motion of the switch blade of the grounding switch, such as rotation of the switch blade about its own axis, so that a mechanical latch may be provided as part of the operating mechanism. This second solution would result in a more complicated operating mechanism for the grounding switch. It is therefore desirable to provide an improved grounding switch structure for use with high voltage disconnecting switches including means for preventing the separation or parting of the switch blade of the grounding switch from the associated contact assembly due to the magnetic forces which result during shortcircuit conditions and which offers important advantages over the other proposed solutions to this problem which were mentioned above.

It is an object of this invention to provide a new and improved electric switch.

A more specific object of this invention is to provide a new and improved high voltage grounding switch.

A further object of this invention is to provide an improved means for retaining the switch blade of a grounding switch in an engaged position with respect to the associated contact assembly in the event that the contact assembly should be inadvertently energized at a relatively high potential.

A still further object of this invention is to provide corona shielding means for a high voltage grounding switch which also assists in magnetically latching the switch blade of the grounding switch in the engaged position with respect to the associated contact means during certain operating conditions.

Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a top plan view of a grounding switch embodying the principal teachings of the invention with the grounding switch shown in the normally open position along with an associated high voltage disconnecting switch mounted on a common supporting means with the high voltage disconnecting switch shown in the closed position.

FIG. 2 is a view, in front elevation, of the grounding switch shown in FIG. '1 along with the associated high voltage disconnecting switch with the grounding switch shown in the open position and the associated disconnecting switch shown in the closed position.

FIG. 3 is a view in end elevation of the grounding switch and the associated disconnecting switch shown in FIGS. 1 and 2 with the grounding switch shown in an intermediate operating position either approaching a fully closed position or just leaving a fully closed position and with the disconnecting switch shown in phantom in the closed condition.

FIG. 4 is an enlarged pictorial view of a portion of the grounding switch shown in FIGS. 1 through 3 illustrating the stationary contact assembly of the grounding switch and certain adjacent parts of the grounding switch and the associated disconnecting switch.

FIG. 5 is an enlarged view in side elevation of the portion of the grounding switch shown in FIG. 4.

Referring now to the drawings and FIGS. 1 through 3 in particular, the structure shown therein comprises a high voltage disconnecting switch assembly 40 and a grounding switch 20 which as illustrated may be of the manually operated type. The main disconnecting switch 40 may be of the type described in greater detail in US Patent No. 3,079,474 which issued Feb. 26, 1963, to E. F. Beach et a1. and which is assigned to the same assignee as the present application.

As shown in FIGS. 1 through 3, the high voltage disconnecting switch assembly 40 comprises three spaced

insulator stacks

31, 32 and 33 which are mounted upon a common metal base 104 and which, as illustrated, are disposed generally in the same predetermined vertical plane. Each of the insulator stacks 31, 32 and 33 comprises a plurality of insulators which are preferably formed from porcelain or a similar material, the number of insulators per stack being optional depending upon the voltage of the system in which the switch 40 is to be utilized. The insulator stacks 31 and 32 are mounted upon the fixed spacers or supporting

members

35 and 37, respectively, which may, in turn, be secured to the top of the common supporting base 104. The insulator stack 33 is fixedly mounted upon a shaft 78 with the end of the shaft 78 being rotatably mounted in a bearing member 75 which is secured to the base 104.

In order to actuate the rotation of the shaft 78 and, in turn, the rotation of the insulator stack 33 about its own longitudinal axis, a crank arm or lever 76 is secured to the shaft 78 below the insulator stack 33 and is adapted for operative connection to any conventional driving means for operating the crank arm to effect rotation of the shaft 78. A shaft 64 is fixedly attached to and extends upwardly from the top of the insulator stack 33 to form in effect a rigid extension of the shaft 78. A forked crank arm 66 is mounted on the shaft 64 and forms part of the operating mechanism 70 of the main disconnecting switch 40. The crank arm 66 is operatively connected to the forked link member 67 through a ball and socket type slip joint, as described in detail in the previously mentioned patent. The link member 67, in turn, is operatively connected through a tubular blade crank member 69 which is adapted to receive one end of the switch blade 102 of the main disconnecting switch 40. The switch blade 102 is supported for rotation about its own axis by a pair of axially spaced bearings which are supported in a hinge casting 71 which, in turn, is pivotally supported by a hinge support member 73 which spans the insulator stacks 32 and 33. As described in the previously mentioned patent, the switch blade 102 may be actuated in an arcuate path into and out of engagement with the spaced

contact jaws

62A and 62B which form part of the break contact jaw assembly 62 which is mounted at the upper end of the insulator stack 31 by operating the crank arm or lever 76 to thereby rotate the insulator stack 33.

As shown in FIGS. 1 and 2, the switch blade 102 is in the closed position and is in engagement with the

contact jaws

62A and 62B. The operating mechanism 70 of the disconnecting switch 40 is so constructed that the switch blade 102 is first rotated about its own axis to disengage the free end of the switch blade 102 from the

contact jaws

62A and 62B and is then pivotally actuated from the substantially horizontal position shown in FIGS. 1 and 2 through an arcuate path to a substantially vertical position which is angularly displaced from the position shown in FIGS. 1 and 2 by an angle of substantially 90. Thus a power conductor (not shown) which may be electrically connected to a terminal means T1 mounted on the insulator stack 31 is disconnected from a power conductor (not shown) which may be electrically connected to a terminal means T2 at the top of the insulator stack 33 and electrically connected to the other end of the switch blade 102 at the hinge end of the disconnecting switch 40.

In order to prevent corona discharge adjacent to the parts of the disconnecting switch 40 at the hinge end of the disconnecting switch 40 which may be energized at a relatively high potential during the operation of the disconnecting switch 40, a pair of loop-shaped corona shielding members or potential grading rings 72 and 74 is mounted at the top of the insulator stacks 32 and 33 on the opposite sides of the parts of the disconnecting switch 40 at the hinge end of the disconnecting switch 40.

In order to prevent corona discharge adjacent to the parts of the disconnecting switch 40 at the break end of the disconnecting switch 40 which may be energized at a relatively high potential during the operation of the disconnecting switch 40, a loop-shaped corona shielding member or potential grading ring 52 is mounted at the top of the insulator stack 31 at one side of the parts of the disconnecting switch 40 at the break end of the disconnecting switch 40 and a generally C-shaped corona shielding member or potential grading ring 54 mounted at the top of the insulator stack 31 at the other side of the parts of the disconnecting switch 40 at the break endof the switch 40, as shown in FIG. 2. It is to be noted that the corona shield 54 at the break end of the disconnecting switch 40 cooperates with a pair of corona shielding members or

potential grading rings

162 and 164 which form part of the grounding switch 20, as will be explained in detail hereinafter. In addition, in order to assist in preventing corona discharge at the free end of the switch blade 102 of the disconnecting switch 40 during opening and closing operations of the disconnecting switch 40, a generally ball-shaped conducting member 102a is mounted at or formed integrally with the free end of the switch blade 102, as shown in FIGS. 1 and 2.

In the operation of the disconnecting switch 40, the switch blade 102 is shown in FIGS. 1 and 2 in the closed position in which the blade 102 engages the

contact jaws

62A and 62B of the break contact jaw assembly 62 with a continuous electrical circuit extending from the terminal T1 at the left end of the disconnecting switch 40, as viewed in FIGS. 1 and 2, through the switch blade 102 to the terminal means T2 at the right end of the disconnecting switch 40. During an opening operation of the disconnecting switch 40, the crank arm or lever 76 is driven in a predetermined direction to rotate the insulator stack 33 to initially rotate the switch blade 102 about its own longitudinal axis which releases the contact pressure between the blade 102 and the contact assembly 62 and disengages the free end of the blade 102 from the

contact jaws

62A and 62B and then to actuate the arcuate movement of the switch blade 102 through the operating mechanism 70 of the disconnecting switch 40, as explained in detail in the patent previously mentioned, During such an opening operation, the switch blade 102 is actuated from the closed position shown in FIGS. 1 and 2 to a substantially vertical open position which is' angularly displaced from the position of the blade 102 shown in FIGS. 1 and 2 by an angle of substantially about the hinge end of the disconnecting switch 40.

It is to be noted that the arcuate or rotational movement of the switch blade 102 of the disconnecting switch 40 from the substantially horizontal position which corresponds to the closed position of the disconnecting switch 40 shown in FIGS. 1 and 2 to the substantially vertical position as just described which corresponds to the open position of the disconnecting switch 40 lies in a substantially vertical predetermined plane in which the insulator stacks 31, 32 and 33 and the other operating parts of the disconnecting switch 40 are generally disposed. A closing operation of the disconnecting switch 40 from the substantially vertical open position just described to the closed position shown in FIGS. 1 and 2 would be accomplished by rotating the crank arm or lever 76 from the operating position which corresponds to a substantially vertical open position of the switch blade 102 in a predetermined direction to initially actuate the arcuate movement of the switch blade 102 from the substantially vertical open position just described in a counterclockwise direction about the hinge end of the disconnecting switch 40 back to the substantially horizontal closed position shown in FIGS. 1 and 2 with the generally arcuate path of the switch blade 102 during the closing operation lying in the same predetermined substantially vertical plane just mentioned. During the final rotational movement of the switch blade 102 during a closing operation, the blade 102 is rotated about its own axis to establish adequate contact pressure between the free end of the blade 102 and the

contact jaws

62A and 62B. It is also to be noted that when the switch blade 102 is in a substantially vertical open position as just described, the electrical circuit which otherwise extends between the terminals T1 and T2 when the disconnecting switch 40 is in the closed position shown in FIGS. 1 and 2 is interrupted and an electrically insulating gap is interposed between the parts of the disconnecting switch 40 at the break end which includes the terminal T1 and the parts of the disconnecting switch 40 at the hinge or right end of the disconnecting switch 40 which includes the terminal T2. When the disconnecting switch 40 is in the open position, the parts of the disconnecting switch 40 at either the break end or at the hinge end may be energized at a relatively high potential in a particular application.

As explained previously, it is desirable under certain circumstances to ground the transmission line or apparatus which may be electrically connected to the terminal T1 after the terminal T1 has been isolated by the opening of the main disconnecting switch 40 in order to drain oif any static charge that may remain and to prevent injury to operating or maintenance personnel in the event that the apparatus which is electrically connected to the terminal T1 should he accidentally or inadvertently reenergized. The grounding switch 20 is provided to perform the necessary grounding operation.

As shown in FIGS. 1, 2 and 3, the grounding switch 20 in general comprises a rotatable switch blade or movable contact arm 22 which is disposed to be actuated from a normally open position which is substantially horizontal, as illustrated, to a closed position which is substantially vertical and in which the switch blade 22 of the grounding switch 20 engages a relatively stationary contact assembly 150 which is mounted at the top of the insulator stack 31, as shown in FIGS. 2 and 3. It is to be noted that the parts of the grounding switch 20 may be supported on the same common supporting base 104 as that on which the parts of the disconnecting switch 40 are supported and that the base 104 may be supported, in turn, by a suitable structural frame (not shown).

In order to actuate the switch blade 22 of the grounding switch 20 between the open and closed positions of the grounding switch 20, the operating mechanism 30 may be provided as shown generally in FIGS. 2 and 3 and is described in greater detail in my copending application Ser. No. 673,673, filed concurrently and assigned to the same assignee as the present application. The operating mechanism 30 of grounding switch 20 may be manually operated by a hand crank 42, as shown in FIG. 3, which is operatively connected to a substantially vertical drive shaft 46 through a gear box or assembly 43 which may be of a conventional type that includes a pair of miter gears to change the direction of the driving torque. As illustrated in FIG. 3, the vertical drive shaft 46 may pass through a position and stop indicator 44 and may be operatively connected to the input shaft 48A of a gear assembly 48 having a substantially horizontal output shaft 47. The gear assembly or gear box 48 may be supported on a bracket member 51 which, in turn, may be supported on and secured to the common supporting base 104, as best shown in FIG. 3, and may be of a conventional type which includes a pair of miter gears to change the direction of the driving torque which is transmitted from the substantially vertical drive shaft 46 to the substantially horizontal output shaft 47 of the gear assembly 48. The output shaft 47 of the gear assembly 48, in turn, is operatively connected to the operating mechanism 30 of the grounding switch 20 by suitable coupling means, as

indicated at 49 in FIG. 3. More specifically, the output 6 shaft 47 of the gear assembly 48 is operatively connected by the coupling means 49 to the input shaft 202 which forms part of the gear box assembly 200 of the operating mechanism 30 of the grounding switch 20.

In general, the gear box assembly 200 is provided to change the direction of the driving torque transmitted from the output shaft 47 of the gear box assembly 48 and received at the input shaft 202 of the gear box assembly 200 and to support the switch blade 22 of the grounding switch 20 on an output shaft 232 of the gear box assembly 200 for rotation about a fixed axis which preferably intersects the longitudinal axis of the switch blade 22 at an angle of substantially 45 In this instance, the gear box assembly 200 also supports the switch blade 22 for rotation about a fixed axis which intersects both a substantially horizontal axis and a substantially vertical axis at an angle of substantially 45.

In order to fixedly support the switch blade 22 of the grounding switch 20 on the output shaft 232 of the gear box assembly 200, as described in my copending application previously mentioned, a generally tubular support member 206 is mounted on the output shaft 232 and is adapted to receive one end of the switch blade 22 of the grounding switch 20. More specifically, the support member 206 includes a flange portion 206A which may be secured to the flange 234 at the upper end of the output shaft 232 of the gear box assembly 200 by suitable means such as bolts (not shown). As best shown in FIG. 2, the left end of the switch blade 22 of the grounding switch 20 is disposed inside the tubular portion of the supporting member 206. The switch blade 22 of the grounding switch 20 may be secured to the supporting member 206 by suitable means, such as bolts (not shown) which pass transversely through both the supporting member 206 and the switch blade 22 or the supporting member 206 may be provided with an axially extending slot (not shown) which may be drawn together at the opposite sides to clamp the switch blade 22 by suitable means, such as bolts (not shown), which pass transversely between the opposite sides of the supporting member 206 adjacent to such a slot where provided. As previously mentioned, the switch blade 22 is supported on the shaft 232 for rotation therewith about a fixed axis which is the axis of rotation of the shaft 232 with the axis of the shaft 232 preferably intersecting the longitudinal axis of the switch blade 22 at an angle of substantially 45. It is to be understood that in a particular application the angle between the longitudinal axis of the switch blade 22 and the axis of rotation of the shaft 232 may be slightly greater or less than 45", such as plus or minus one degree.

In order to provide an electrically conducting path between the end of the switch blade 22 which is pivotally supported on the shaft 232 and a ground terminal (not shown) provided on the supporting base 104, the flexible conducting straps 172 are each secured at one end to the switch blade 22 by suitable means such as bolts (not shown) and at the other end to the ground terminal provided on the supporting base 104. The flexible conducting straps 172 maintain an electrically conducting path between the ground terminal provided on the relatively stationary supporting structure 104 and the switch blade 22 of the grounding switch 20 during all operating conditions of the grounding switch 20.

In order to facilitate the opening and closing operations of the grounding switch 20 and to assist in establishing adequate contact pressure between the switch blade 22 and the contact assembly of the grounding switch 20, an auxiliary blade portion or tip portion 24 is disposed at the free end of the switch blade 22 and is pivotally supported at the free end of the switch blade 22 by the pivot pin 23 for limited rotation with respect to the switch blade 22. As best shown in FIG. 3, a slot or recess 29 is provided at the free end of the switch blade 22 in which a stop pin 27 which is mounted on the auxiliary blade portion 24 is disposed to travel during the operation of the grounding switch 22. In order to frictionally retain the auxiliary blade portion 24 in whatever angular position the auxiliary blade portion 24 is actuated to during the operation of the grounding switch 20, suitable meanS, such as spring washers may be disposed on the pivot pin 23 at the opposite sides of the auxiliary blade portion 24. In order to actuate the rotation of the auxiliary blade portion 24 to the position shown in FIG. 1 in which the auxiliary blade portion 24 is disposed at a predetermined obtuse angle with respect to the longitudinal axis of the switch blade 22, the projecting or biasing member 26 is provided and mounted on the common supporting base 104 to project therefrom and engage the auxiliary blade portion 24 when the switch blade 22 is in the normally open position, as shown in FIGS. 1 and 2. The switch b ade 22 and the auxiliary blade portion 24 together comprise an overall switch blade of the grounding switch 20 and form a toggle means with the pivot pin 23 being disposed at the knee of the toggle means thus formed.

In order to prevent adverse weather conditions such as ice and snow from interfering with the operation of the auxiliary blade portion 24 at the free end of the switch blade 22, the shield member or hood 28 may be provided adjacent to the free end of the switch blade 22 when the switch blade 22 is in the normally open position and secured to the common supporting base 24 to cover and protect the free end of the switch blade 22 and the associated auxiliary blade portion 24 as shown in FIGS. 1 and 2.

In order to prevent corona discharge adjacent to the upper break end of the grounding switch 20 which includes the relatively stationary contact assembly 150 for another important purpose which will be explained hereinafter, the grounding switch 20 includes a pair of laterally spaced corona shielding members or potential grading rings 162 and 164 which are generally C-shaped in configuration and which project transversely from the top of the insulator stack 31 in which the shielding

members

162 and 164 are mounted. More specifically, the lower portions 162C and 164C of the shielding

members

162 and 164, respectively, as shown in FIG. 4 may be secured to the opposite sides of an electrically conducting bar or member 350 by suitable means, such as the bolts 352. The conducting bar 350 may be secured to and mounted on or formed integrally with the terminal means T1 and forms an electrically conducting path which extends generally transversely with respect to the axis of the switch blade 22 when the switch blade 22 is in the closed position, as indicated in phantom at 22 in FIG. 2. The shielding

members

162 and 164 include the generally upwardly extending

intermediate portions

162B and 164B, respectively, and the

upper portions

162A and 164A, respectively, which extend or project back toward the terminal means T1 at the top of the insulator stack 31. It is to be noted that both of the

corona shielding members

52 and 54 of the main disconnecting switch 40 which are mounted at the top of the insulator 31 are disposed substantially parallel to the generally vertical plane in which the switch blade 102 travels, as best shown in FIG. 3, and that the shielding

members

162 and 164 of the grounding switch 20 project generally transversely with respect to the plane in which the adjacent corona shielding member 54 of the main disconnecting switch 40 lies, as shown in FIG. 3.

The stationary contact assembly 150 of the grounding switch 20 includes a generally T-shaped electrically conducting member 310 which is mounted on and supported by the

upper portions

162A and 164A of the shielding

members

162 and 164, respectively, with the T-shaped conducting member 310 spanning the distance between the

upper portions

162A and 164A of said shielding members. As shown in FIG. 5, the T-shaped conducting member 310 may be secured at the opposite sides thereof to the

upper portions

162A and 164A of the shielding

members

162 and 164, respectively, by suitable means, such.

as the bolts 322 which pass through aligned openings in the conducting member 310 and the

upper portions

162A and 164A. The conducting member 310 includes a downwardly extending portion 310A, as best shown in FIG. 5, on 'which are mounted a plurality of pairs of

opposed contact fingers

332 and 334 by suitable means, such as the bolts 312. In order to assist in providing adequate contact pressure between the

closed contact fingers

332 and 334, suitable biasing

members

333 and 335 may be disposed in back of each of the

contact fingers

332 and 334, respectively, and mounted on the intermediate portion 310A of the conducting member 310 by the same fastening or securing means, such as the bolts 312. The

contact fingers

332 and 334 may include the contact inserts at the lower end thereof as indicated at 332A and 334A, respectively. As mentioned previously, the shielding

members

162 and 164 are disposed at the opposite sides of the relatively stationary contact assembly in order to prevent corona discharge and for another purpose which will be described hereinafter. It is important to note that the shielding

members

162 and 164 provide the sole support for the relatively stationary contact assembly 150 of the grounding switch 20 and that the shielding

members

162 and 164 are formed from an electrically conducting material to provide the only electrically conducting current carrying path between the contact assembly 150 and the conducting bar 350 which leads to the terminal means T1.

In order to guide the final portion of the movement of the switch blade 22 and the associated auxiliary blade portion 24 into engagement with the contact assembly 150, a first guide member 152 is mounted on and supported by the shielding

members

162 and 164, as best shown in FIGS. 4 and 5. More specifically, the guide member 152 is secured at the opposite sides thereof to the lower portions 162C and 164C of the shielding

members

162 and 164, respectively, by suitable means, such as the bolts 372, which pass generally transversely through aligned openings in the lower portions 162C and 164C and the guide member 152. The guide member 152 includes a generally V-shaped recess or notch, as indicated at 151, which guides the movement of the auxiliary blade portion 24 at the upper end of the switch blade 22 toward engagement with the contact assembly 150.

The second guide means or member 153 includes a pair of spaced supporting leg members 349 which are generally triangular in shape and which are secured to and supported on the first guide member 152, as best shown in FIGS. 1 and 4 with the supporting leg members 349 being disposed generally between the first guide member 152 and the contact assembly 150. The leg members 349 may be formed from a suitable electrically insulating material having sufficient mechanical strength, such as material of the glass-polyester type. The second guide means 153 also includes a base plate 348 which spans the supporting legs 349 and is secured to the supporting legs 349 by suitable means, such as a plurality of bolts 346.

The second guide means or member 153 also includes a pair of laterally spaced tapered guide plates 342 and .344 which may be mounted on or formed integrally with the base plate 348 and secured thereto by suitable means, such as the bolts 346, which also secure the base plate 348 to the supporting legs 349. The

guide plates

342 and 344 are disposed on the base plate 348 to form a generally V-shaped guide passage, as indicated at 362, which assists in guiding the final portion of the travel of the auxiliary blade portion 24 toward an engaged position with respect to the contact assembly 150 which is mounted above the second guide means 153, as best shown in FIG. 5. It is to be noted that the second guide means 153 and, more specifically, the base plate 348 also acts as a stop which limits the rotational travel of the switch blade 22 of the grounding switch 20 when the auxiliary blade portion 24 engages the base plate 348 and the auxiliary blade portion 24 is gradually rotated with respect to the switch blade 22 about the pivot pin 23 until the stop pin 27 on the auxiliary blade portion 24 engages one side of the slot 29 provided in the upper end of the switch blade 22. It is to be noted that the base plate 348 and the associated

guide plates

342 and 344 may also be formed from an electrically insulating material having sufiicient mechanical strength, such as a material of the glass-polyester type.

In considering the operation of the grounding switch 20, it will be assumed that initially the switch blade 102 of the disconnecting switch 40 is in a substantially vertical open position, as previously described, and that the terminal means T1 at the break end of the disconnecting switch 40 is deenergized. In a particular application, the terminal means T2 at the other or hinge end of the dis connecting switch 40 may or may not remain energized at a relatively high potential during the operationof the grounding switch 20. It will also be assumed that initially the switch blade 22 of the grounding switch 20 is in the normally open position which is substantially horizontal, as illustrated in FIGS. 1 and 2, with the auxiliary blade portion 24 being disposed at a predetermined obtuse angle with respect to the longitudinal axis of the switch blade 22, as shown in FIG. 1, to which the auxiliary blade portion 24 is actuated by the biasing or projecting member 26. It is important to note that in the open position the switch blade 22 of the grounding switch 20 lies generally in the same vertical plane as that in which the insulator stacks 31, 32 and 33 lie and in which the arcuate travel of the switch blade 102 of the disconnecting switch 40 occurs between the open and closed positions. It is to be understood that in certain applications, the normally open position of the switch blade 22 as illustrated may be slightly spaced from the vertical plane in which the switch blade 102 of the disconnecting switch 40 travels but substantially parallel to the vertical plane, as indicatedinFIG. 1.

During a closing operation of the grounding switch 20, the hand crank 42 shown in FIG. 3 may be manually turned or rotated to apply a driving torque through the gear assembly 43 to the substantially vertical drive shaft switch blade 22 of the grounding switch 20 is supported.

The switch blade 22 of the grounding switch 20 then starts to rotate out of or away from the substantially vertical plane in which the switch blade 102 of the disconnecting switch 40 travels from the position shown in FIG. 1 in a generally clockwise direction about the left end of the switch blade 22, as viewed in FIG. 1. Because of the angular mounting of the switch blade 22 on the shaft 232, as explained in detail in my copending application previously mentioned, the switch blade 22 rotates with the shaft 232 along a generally conical surface or path which is defined by the movement of the switch blade 22 from a substantially horizontal normally open position, as shown in FIG. 1, to a substantially vertical position, as indicated in phantom at 22" in FIG. 2 in which the auxiliary blade portion 24 at the upper or free end of the switch blade 22 engages the relatively stationary contact assembly 150. It is important to note that as soon as the switch blade 22 starts to rotate from the position shown in FIG. 1, the switch blade 22 moves out of or away from the substantially vertical plane in which the switch blade 102 of the disconnecting switch 40 rotates and travels in a generally conical path, as just mentioned, which is indicated by the intermediate position of the switch blade at 22' in phantom in FIG. 1 and finally reaches the position shown in FIG. 3 just prior to the engagement of the auxiliary blade portion 24 with the

contact fingers

332 and 334 of the contact assembly 150. It is important to note in FIG. 3 that because of the angular position of the auxiliary blade portion 24 with respect to the longitudinal axis of the switch blade 22, the upper end of the auxiliary blade portion 24, as viewed in FIG. 3, is underneath the contact assembly to facilitate the entrance of the auxiliary blade portion 24 between the

contact fingers

332 and 334 of the contact assembly 150 which are biased toward one another by the biasing

members

333 and 335, which may be of the leaf spring type, to insure adequate contact pressure between the auxiliary blade portion 24 and the

contact fingers

332 and 334 of the contact assembly .150. As the switch blade 22 is further rotated in a counterclockwise direction as viewed in FIG. 3, the stop pin 27 on the auxiliary blade portion 24 will engage one side of the slot provided at the upper end of the switch blade 22 to prevent further rotation of the auxiliary blade portion 24 with respect to the switch blade 22. The auxiliary blade portion 24 will then be forced upwardly between the

contact fingers

332 and 334 of the contact assembly 150 against the biasing forces exerted on the

contact fingers

332 and 334 by the associated biasing

members

333 and 335, respectively, to establish adequate contact pressure ligtoween the switch blade 22 and the contact assembly When the switch blade 22 of the grounding switch 20 reaches a fully-closed position, the switch blade 22 will be disposed in a substantially vertical position as indicated in phantom at 22" in FIG. 2 with the auxiliary blade portion 24 substantially aligned axially with the switch blade 22.

It is to be noted that during a closing operation of the grounding switch 20, the final portion of the closing movement of the switch blade 22 and the associated auxillary blade portion 24 will be guided by the

blade guide members

152 and 153 each of which includes a generally V-shaped slot Or passage to guide the movement of the upper end of the switch blade 22 and the associated auxiliary blade portion 24 toward the contact assembly 50. As previously mentioned, the guide-means or member 153 also functions as a stop when the upper end of the auxiliary blade portion 24 engages the base plate 348 of the guide means 153 to initiate the rotation of the auxiliary blade portion 24 from the angular position indicated in FIG. 3 to a substantially aligned position with respect to the switch blade 22 until the stop pin 27 on the auxiliary blade portion 24 engages the outer side of the slot 29 provided in the upper end of the switch blade 22. Considering the operation of the switch blade 22 and the auxiliary blade portion 24 as a toggle means which is formed by said switch blade and said auxiliary blade portion, the toggle means is normally maintained in a partially collapsed condition when the blade 22 is in the normally open position shown in FIG. 1 with the knee of the toggle means being disposed at the pivot pin 23. During a closing operation as just indicated, the toggle means which includes the blade 22 and the auxiliary blade portion 24 is actuated to substantially an overcenter condition as the auxiliary blade portion 24 engages the contact assembly 150 and the auxiliary blade portion 24 is rotated with respect to the blade 22 until the stop pin 27 engages the outer side of the slot 29 at the upper end of the blade 22 after the auxiliary blade portion 24 engages the base plate 348 of the second guide means 153. It is important to note that during the final portion of the travel of the switch blade 22 toward a fully closed position with respect to the contact assembly 150, the blade 22 is traveling generally transversely with respect to the substantially vertical plane in which the blade 102 of the disconnecting switch 40 travels and that the switch blade 22 ultimately reaches a closed position in which the switch blade 22 is again disposed in generally the same switch blade 22 is again disposed in generally the same vertical plane as that in which the blade 102 of the disconnecting switch 40 travels.

During an opening operation of the grounding switch 20, it is assumed that initially the switch blade 22 of the grounding switch 20 is in the substantially vertical closed position indicated in phantom at 22" in FIG. 2 and that the auxiliary blade portion 24 at the upper end of the switch blade 22, as most nearly shown in FIG. 3, is substantially aligned with the longitudinal axis of the switch blade 22. When the hand crank 42 is manually turned or rotated to apply a driving torque to the output shaft 232 of the gear assembly 200, the switch blade 22 of the grounding switch 20 will rotate from a substantially vertical position generally away from or out of the substantially vertical plane in which the blade 102 of the disconnecting switch 40 travels with the auxiliary blade portion 24 initially remaining in engagement with the

contact fingers

332 and 334 of the contact assembly 150' and with the upper end of the auxiliary blade portion 24 gradually dropping until the upper end of the auxiliary blade portion 24 clears the

contact fingers

332 and 334 of the contact assembly 150. During an opening operation of the grounding switch 20, the auxiliary blade portion 24, as best shown in FIG. 3, will be angularly rotated with respect to the switch blade 22 during the initial portion of the opening movement of the blade 22 until the stop pin 27 on the auxiliary blade portion 24 is engaged by the other side of the slot 29 provided at the upper end of the blade 22. After the auxiliary blade portion 24 reaches the limit of its rotational travel with respect to the switch blade 22 as determined by the stop pin 27 and the slot 29, the switch blade 22 and the auxiliary blade portion 24 will travel along a generally conical surface or path as previously described until the blade 22 is rotated about the axis of the shaft 232 to reach the normally open position shown in FIG. 1 with the switch blade 22 again approaching the substantially vertical plane in which the blade 102 of the disconnecting switch 40 travels generally transversely with respect to the latter plane until the switch blade 22 reaches the final normally open position which is substantially horizontal as shown in FIGS. 1 and 2. As mentioned previously, when the switch blade 22 returns to the normally open position, it is disposed in generally the same plane as that in which the blade 102 of the disconnecting switch 40 travels or slightly spaced therefrom and generally parallel thereto as previously mentioned.

It is to be noted that the construction of the auxiliary blade portion 24 at the upper end of the switch blade 22 facilitates the release of the contact pressure between the contact assembly 150- and the switch blade 22 which is frictionally held between the

contact fingers

332 and 334 of the contact assembly by the biasing forces exerted on said contact fingers by the associated biasing

members

333 and 335, respectively. This is because the auxiliary blade portion 24 initially rotates through a predetermined angular position with respect to the blade 22 which is controlled by the size of the slot 29 and the position of the stop pin 27 on the auxiliary blade portion with the free end of the auxiliary blade portion 24 dropping downwardly during the initial opening rotation of the blade 22 to clear the contact assembly 150 as the blade 22 is rotated further toward the open position. Considering the blade 22 and the auxiliary blade portion 24 as a toggle means during the opening operation, the toggle means is initially in substantially an overcenter condition and is then partially collapsed to a predetermined degree to facilitate the release of the contact pressure between the blade portion 24 and the contact assembly 150 as just indicated. In other words, the blade portion 24 is pulled initially downwardly between the

contact fingers

332 and 334 of the contact assembly 150 with a wiping action until the blade portion 24 clears the lower ends of the

contact fingers

332 and 334. As previously mentioned, the biasing or projecting member 26 is provided on the supporting base 104 as shown in FIG. 1 to insure that the blade portion 24 assumes the desired angular position with respect to the longitudinal axis of the blade 22 in the normally open position of the blade 22 with the blade portion 24 being held frictionally in the desired angular position by associated spring washers which may be provided as required in a particular application on the pivot pin 23.

If the terminal means T1. should be inadvertently reenergized after the switch blade 22 of the grounding switch 20 has been actuated to a closed position as just described to effectively place the terminal means T1 at a ground potential through a path which includes the conducting bar 350, the shielding

members

162 and 164 electrically in parallel, the conducting member 310, the contact fingers 3-32 and 334, the auxiliary blade portion 24, the switch blade 22, and the flexible shunts 172 shown in FIG. 2 which electrically connect the switch blade 22 to a ground terminal provided on the supporting base 104, short-circuit current would flow from the terminal means T1 through the current carrying path just mentioned an associated protective device such as an automatic circuit breaker interrupted the short-circuit current to again deenergize the terminal means T1. In a conventional grounding switch structure which includes a simple right-angle bend or turn in the current carrying path which leads from a terminal means, such as the terminal means T1, to an associated grounding switch blade, the magnetic forces which result would tend to blow the grounding switch blade to the open position unless mechanically latched and would lead to severe damage or destruction of the grounding switch during the assumed operating condition. It is to be noted that in the disclosed structure, the current carrying path as defined by the electrically conducting bar 350 leads or extends generally transversely with respect to the longitudinal axis of the switch blade 22 when the switch blade 22 is in the closed position but that an electrically conducting path defined by the shielding

members

162 and 164 is interposed between the conducting bar 350 and the auxiliary blade portion 24 which engages the contact assembly 150. Since the shielding

members

162 and 164 comprise the only current carrying or electrically conductive path between the contact assembly which is supported on said shielding members and the conducting bar 350, the shielding

members

162 and 164 form with the auxiliary blade portion 24 of the grounding switch 20 a magnetic flux producing winding when current flow therethrough, such as during the short-circuit condition just described, which results when the terminal means T1 is inadvertently re-energized. If it is assumed that the instantaneous direction of the short-circuit current during such an operating condition is in an upward direction with respect to the switch blade 22 as indicated by the arrow I in FIG. 3, the short-circuit current will divide when the current reaches the contact assembly 150 and more specifically when the current reaches the conducting member 310, as shown in FIG. 5, with half of the current flowing through each of the shielding

members

162 and 164 as indicated by the arrows 1 /2 until the current reaches the electrically conducting member or bar 350 in which the currents will reunite and the short-circuit current will flow toward the terminal means T1, as indicated by the arrow I in a direction which is generally transvrese with respect to the longitudinal axis of the switch blade 22 when the switch blade 22 is in the closed position. It is to be noted that when the current leaves the contact assembly 150, the current will flow in a generally downward direction during the assumed operating condition through the

intermediate portions

162B and 164B of the shielding

members

162 and 164, respectively, and then flow toward the conducting bar 350 and the terminal means T1 in such a direction that the magnetic flux as produced by the current flow in the shielding

members

162 and 164 will be in a direction extending generally from left to right as viewed in FIG. 4 inside the shielding

members

162 and 164. In accordance with the conventional right-hand rule which relates the directions of the current flowing in a conductor with the magnetic flux acting on the conductor and the magnetic force which results from the interaction of the magnetic flux and the current in the conductor, the forces exerted on the auxiliary blade portion 24 which is disposed inside the shielding

members

162 and 164 when the grounding switch 20 is closed, due to the interaction of the magnetic fluxes produced by the current flow through the shielding

members

162 and 164 will be generally in a direction toward the conducting bar 350 to assist in holding the auxiliary blade portion 24 in an engaged position with respect to the contact assembly 150. It is to be noted that the magnetic flux produced by the current flow in the conducting bar 350 as indicated by the arrow I would still act on the auxiliary blade portion 24 which is disposed between the shielding

members

162 and 164 and would interact with the current in the blade 22 to produce a force acting on the blade 22 which would otherwise tend to blow the blade 22 open from the engaged position indicated in phantom at 22" in FIG. 2. The relative magnitudes, however, of the fluxes produced by the current flow through the shielding

members

162, 164 and the corresponding forces on the auxiliary blade portion 24 compared with the corresponding values of those produced by the current flow I and acting on the upper end of the switch blade 22 and the auxiliary blade portion 24 are such that the forces exerted on the auxiliary blade portion 24 by the magnetic fluxes produced by the shielding

members

162 and 164 are relatively much greater than the force exerted on the blade 22 and the auxiliary blade portion 24 by the magnetic flux produced by the current flow I and interacting with the current through the switch blade 22 so that a net force results on the auxiliary blade portion 24 tending to hold the auxiliary blade portion 24 in the engaged position. In other words, because of the change in the direction of the current between the switch blade 22 and the terminal means T1 produced by the shielding

members

162 and 164 acting as blow-in windings, the switch blade 22 is magnetically latched in the engaged position indicated in phantom at 22" in FIG. 2 if the terminal means T1 should be inadvertently re-energized to cause short-circuit current to flow through the grounding switch 20 as just described. The shielding

members

162 and 164 therefore act both as shielding members to prevent corona discharge adjacent to the conducting parts of the grounding switch 20 at the break end of the grounding switch 20 and also to assist in magnetically latching the upper end of the switch blade 22 of the grounding switch 20 in the engaged position in the event that the terminal means T1 should be inadvertently or accidentally re-energized following the closing of the grounding switch 20.

It is to be understood that in a particular application, the disconnecting switch 40 and a grounding switch 20 as disclosed may comprise one pole of a three phase high voltage switch structure in which the other pole units of the three phase switch structure may be disposed in sideby-side relation or laterally spaced from the disconnecting switch 40 and the associated grounding switch 20. More specifically, the output shaft 47 of the gear assembly 48 shown in FIG. 3 may be extended axially to be mechanically or operatively connected to the other pole unit of a three-phase switch structure with only a single hand crank 42 and a single vertical drive shaft 46 being required in a particular application. It is also to be understood that the teachings of the applicants invention may be applied to other types of grounding structures in which the switch blade of the grounding switch would otherwise form with the associated contact assembly a simple right-angle bend in the current carrying path. It is to be further understood that a grounding switch structure as disclosed may be employed to ground either the hinge end or the break end of the associated main disconnecting switch by mounting the stationary contact assembly at the appropriate end of the associated disconnecting switch.

The apparatus embodying the teachings of this invention has several advantages. For example, the switch blade of the grounding switch as disclosed is retained in an engaged position with respect to the associated contact assembly magnetically in the event that the associated terminal means is inadvertently re-energized following the closing operation of the grounding switch by the use of shielding members which both provide a current carrying path for the current which produces the magnetic fluxes which assist in the latching operation in which also prevent corona discharge. In addition, the grounding switch structure as disclosed avoids the need for more complicated operating mechanisms which provide the dual motion of the switch blade which includes both an overall arcuate motion and a motion about its own axis in order to permit mechanical latching of certain types. The grounding switch structure as disclosed also avoids the necessity for greatly increased mechanical forces which might be otherwise required in certain types of switch structures to latch the grounding blade in the engaged position during the short-circuit conditions are described previously. Finally the shielding and blow-in Winding structures disclosed prevent the severe damage or destruction of the grounding switch which would otherwise result in certain applications if the terminal means of the main apparatus should be inadvertently re-energized following a closing operation of the grounding switch, without requiring separate structural parts to perform the magnetic latching function.

Since numerous changes may be made in the above described apparatus and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all the matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. A high voltage switch comprising an insulator stack, terminal means mounted on one end of the insulator stack, an elongated switch blade pivotally supported adjacent to the other end of the insulator stack to move between a first position generally perpendicular to the insulator stack and a second position generally parallel to the insulator stack with the free end of the blade being adjacent to the terminal means in the second position, a pair of spaced corona shielding members mounted on said one end of the insulator stack to project transversely with respect to the insulator stack and electrically connected to the terminal means, and contact means mounted on 'and between said pair of corona shielding members to be engaged by said switch blade in the second position, said pair of corona shielding members forming the only current carrying path between the contact means and the terminal means.

2. The combination as claimed in claim 1 wherein the pair of corona shielding members comprise a pair of corona rings shaped to produce magnetic fluxes when currents flow therethrough which interact with the current in the switch blade to assist in retaining the free end of the switch blade in engagement with the contact means.

3. The combination as claimed in claim 1 wherein the terminal means forms part of a current carrying path which is generally transverse to the switch blade in the second position and the corona shielding members are shaped to form with the blade a magnetic flux producing Winding when current flows therethrough, the magnetic flux produced by said winding being in a direction to interact with the current in the blade to assist invretaining the free end of the blade in the second position in engagement with the contact means.

4. A high voltage switch structure comprising first and second spaced, substantially parallel insulator stacks each having terminal means mounted thereon, a first switch blade pivotally connected to the terminal means on one of the insultaor stacks to move in a predetermined path lying generally in a plane between an open position and an engaged position with respect to the terminal means on the other insulator stack, a first pair of corona shielding members disposed on each insulator stack on opposite sides of the associated terminal means and generally parallel to the plane in the first switch blade moves, a second switch blade rotatably supported adjacent to the lower end of one of the insulator stacks to move in a predetermined path between a first position and a second: position in which the free end of the second switch blade is disposed adjacent to the top of the adjacent insulator, stack, a second pair of spaced corona shielding members mounted on the insulated stack adjacent to the second switch blade to project beyond the other pair of shielding members on the same insulator stack generally transversely with respect to the plane in which the first switch blade moves, contact means mounted on and between the second pair of corona shielding members to be engaged by the second switch blade in the second position, said second pair of corona shielding members forming the only current carrying path between the last-mentioned contact means and the terminal means on the adjacent insulator stack. 1

5. The combination as claimed in claim 4 wherein the second pair of corona shielding members comprises a pair of corona rings shaped to produce magnetic fluxes when current flows therethrough which interact with the current in the second switch blade to assist in retaining the free end of the second switch blade in the second position in engagement with the associated contact means.

6. The combination as claimed in claim 4 wherein the terminal means on the insulator stack adjacent to the second switch blade forms part of a current carrying path which extends generally transversely to the second switch blade in the second position and the second pair of corona shielding members are shaped to form with the second switch blade magnetic flux producing windings when current flows therethrough with-the-magnetic flux thus produced interacting with the current in the second blade to assist in retaining the second switch blade in the second position.

7. A high voltage switch comprising stationary contact means, a rotatable shaft, an elongated switch blade secured to the shaft and movabletherewith in a predetermined path to actuate the free end of the blade into and out of engagement with the stationary contact means, a pair of corona shielding members disposed on opposite sides of the stationary contact means and on opposite sides of the free end of the blade when the blade is in engagement with the stationary contact means, relatively stationary conducting means forming a current carrying path which extends generally transversely with respect to said blade when said blade is in engagement with said stationary contact means, said corona shielding members forming the only electrically conductive paths between said stationary contact means and said relatively stationary conducting means when the blade is in engagement with the stationary contact means, said corona shielding members being shaped to produce magnetic fluxes when current flows therethrough which interact with the current in the blade to assist in retaining the free end of the blade in engagement with the stationary contact means.

References Cited UNITED STATES PATENTS 1,958,159 5/1934 Bresson 335- 2,154,665 4/ 1939 Christensen 20048 3,024,328 3/1962 Burdeshaw 20048 X 3,288,955 11/1966 Turgeon 20048 ROBERT K. SCHAEF ER, Primary Examiner H. J. HOHAUSER, Assistant Examiner U.S. Cl. X.R. 174-440