US3493699A - Isolating switch with sphere gap - Google Patents

Description

Feb- 3 1970 J. A. TU-RGEON ISOLATING SWITCH WITH SPHERE GAP 2 Sheets-Sheet 1 Filed Nov. 9, 1967 Feb. 3, 1970 J. A. TuRGEoN ISOLATING SWITCH WITH SPHERE GAP 2 Sheets-Sheet I Filed Nov. 9, 1967 wa www L z Q l f F l. NN MN Q MN l l IiIIIEIIINMLF l l l l |||.M. \M\N\ m lluml l t W i MN m United States Patent O U.S. Cl. 200-48 11 Claims ABSTRACT OF THE DISCLOSURE An isolating switch having two rotatable switchblades. The switchblades each have a contact at one of its ends and a spherical electrode at its other end whereby rotation of the switchblades to their closed position causes engagement of the contacts and rotation of the switchblades to their open positions produces a spherical open gap between the other ends of the switchblades and results in a substantially uniform dispersed electrostatic field in the open gap. The result is that the switch open gap may be made substantially shorter than the distance from the switchblades to ground and yet insure that any flashover will be between switchblades and ground rather than across the switch open gap.

BACKGROUND OF THE INVENTION This invention relates to electric switches and more specifically relates to high voltage air isolating switches of the disconnect type which are provided with novel switchblades `which substantially minimize the danger of flashover in the open gap between the switchblades when they are in their disconnect position and substantially reduces the required open gap.

Disconnecting switches are designed to isolate electrical apparatus and portions of electrical systems from energized lines for safe handling, maintenance, repair and inspection. It is, therefore, most important to provide adequate protection for personnel working in the immediate region of the disconnected equipment. Hence, when the switch is open, it is necessary that the gap in the open position must be adequate to withstand all usual, as well as anomalous, voltages impressed upon it by the system. If a surge voltage causes the switch open gap to ashover, the lives of personnel may be seriously jeopardized.

Such disconnecting switches are customarily designed so that the switch open gap will withstand higher voltages than the insulator columns which support the energized parts from the grounded metal base. As a result, fiashover is much more likely to occur between the energized parts and ground than across the switch open gap. In this manner, the insulator columns provide protection for the switch and operating personnel against surge voltages. However, this requires the provision of large open gaps in the switch to insure greater withstand ability than exists across the insulator columns.

In the past, methods used by others to insure greater withstand ability to high volt-ages of the switch open gap than the withstand ability across the insulator columns have included such devices as rod electrodes connected to the base of the insulator columns to reduce the effective withstand ability of the insulator columns as set forth in U.S. Patent No. 3,117,192, issued to J. B. Owens on Jan. 7, 1964 and assigned to the assignee of the instant invention, ground plane appendages connected to the ground base also effectively lowering the withstand ability of the insulator columns as set forth in U.S. Patent No. 3,312,795 issued to A. Foti and assigned to the as- ICC signee of the instant invention, and various other devices for effectively lowering the withstand ability of the insulating columns. All of these methods, however, suffer two critical drawbacks.

The first drawback is that the effective withstand ability of the insulator columns cannot be reduced without limitation. The effective withstand ability of the insulator columns cannot be reduced to the point that it will not be sufficient under high voltage conditions when the system is in operation. If the withstand ability of the insulator columns is too low, the system will not be able to function properly and reliably.

The second drawback is that the gap between the switchblades of the disconnecting switch in all of these cases behaves like a rod gap and since the withstand ability of the insulator columns must always be sufficiently high, this gap must remain large. The necessity of this large gap distance creates a situation subject to anomalous ashovers rather than the required controlled ashover to ground. With a very large gap behaving like a rod gap it is difficult to obtain the required fiashover control.

In recent times, power plants have been developed using voltages as high as SOO-700 kilovolts. These plants require disconnecting switches having insulator columns with great withstand ability during operation. The insulator columns must be in the order of 20 feet high to provide adequate withstand ability. Under these conditions the switch open gap using existing switchblades must be considerably longer to insure that fiashover will be across the insulator columns rather than in the switch open gap. By means of the present invention, the switch open gap has been reduced to between 4 and 6` feet while insuring no fiashover in the switch open gap.

This invention provides a new and novel switch open gap whereby the switch open gap is substantially shortened to produce greater control of any tiashovers without the necessity of reducing the effective withstand ability of the insulator columns.

This invention also permits the use of shorter switchblades and shorter mounting base to efiect a substantial saving and in situations where the withstand ability of the insulator columns is not required to be high under operating conditions, these components may be shortened even further.

This invention also permits a substantial saving in yard space as a result of the use of shorter switchblades and shorter switch open gaps.

This invention solves the problems of the prior art by providing new and novel switchblades which set up a substantially uniform dispersed electrostatic field over a wide but controlled area when the switchblades are in their disconnect position rather than the concentrated electrostatic field lacking uniformity previously established by switchblades producing rod gaps.

In a preferred embodiment of the invention, a center break two-insulator disconnect switch is provided with a pair of rotatable switchblades each having contacts on one end and spherical electrodes on the other end. When the contacts are engaged, the spherical electrodes are on opposite sides of the insulator columns and when the switchblades are rotated to their disconnect position, the spherical electrodes are rotated to a position directly between the insulator columns with the sep-aration between the two spherical electrodes defining the switch open gap. With the switchblades in this latter position a sphere gap is produced and any potential difference between the two switchblades will set up a substantially uniform dispersed electrostatic field. Since the electrostatic field is substantially uniform and over a wide area, the voltage necessary to cause any fiashover in the switch open gap will be far greater than necessary for a rod gap and the switch open gap may be decreased substantially.

Accordingly, a primary object of this invention is to provide a novel switch open gap to protect against llashover in this gap in disconnecting switches.

Another object of this invention is to provide a novel switchblade construction for disconnecting switches which permits a decrease in the length of the switch open gap of the switch.

Another object of this invention is to provide novel switchblades having spherical electrodes and having minimum blade length and still preventing open gap breakdown on the occurrence of surge voltages.

Another object of this invention is to provide a disconnecting switch wherein the switch open gap is substantially shorter than the insulator columns and yet insures against ashover in the switch open gap.

Yet another object of this invention is to prOvide a diS- connecting switch having integrated coordinated switchblades, insulator columns and base ground to insure proper contact when the switch is closed and propel positioning of the switchblades when the switch is open.

These and other objects of this invention will become apparent from reading the accompanying description and drawings, in which:

FIGURE 1 is an elevational view of the disconnect switch of the instant invention with the switch in its closed condition;

FIGURE 2 is an elevational view of the disconnect switch of the instant invention with the switch in its disconnected condition; and

FIGURE 3 is a top view of the switch base of the disconnect switch.

Referring now to FIGURES 1 through 3, there is shown a center break two-insulator disconnect switch assembly comprised of a switch base which is preferably of a rigid metallic structure. The switch base 10 is electrically grounded by a suitable conductor (not shown). The switch base 10 is provided with a channel 12 for housing rotatable link 13. The switch base 10 is also provided with two pairs of concentric cylindrical holes 14 and 15, and 15 and 17, respectively. The concentric holes engage the lower portions of the insulator columns 18 and 19 in an obvious manner such that the columns are rotatable within these holes.

Insulator columns 18 and 19 have gears 21 and 22, respectively, at their lower ends. Gears 21 and 22 lit into holes and 17, respectively, to engage gears 23 and 24, respectively, located on link 13. Insulator column 19 also has an operating crank arm 25 rigidly connected to it. Crank arm 25 is rotatable between two positions as defined lby stops 26 and 27, respectively. At their upper ends, insulator columns 18 and 19 are rigidly connected to switchblades or contact yarms 31 and 32, respectively, in any suitable manner. It is noted that the base and insulator columns may have any suitable arrangement whereby the insulator columns are rotatable, such as shown in U.S. Patent No. 3,235,698 assigned to the assignee of the instant invention.

Switchblades 31 and 32 are made of suitable conductive material and have contacts 33 and 34, respectively, on one end thereof. The contacts may be of any suitable structure, such as shown in'above-mentioned U.S. Patent No. 3,235,698. The switchblades 31 and 32 also have spherical electrodes 35 and 36, respectively, on their ends opposite the contacts. The switchblades 31 and 32 are pivotally connected to conductors 37 and 38, respectively, in any suitable manner. It is to be noted that while spherical electrodes have been shown, the electrodes may also be toroidal shaped rings.

Having described the structure of one embodiment of the instant invention, the operation of the disconnect switch will now be described. When the switch is closed, the jaw-type contact finger arrangement of contact 33 is held in proper engagement with contact 34 by means of operating crank arm 25 being placed in position against stop 26 as shown in FIGURE 1. If for some reason the switch must be disconnected, such as for maintenance, repair or inspection, the crank arm 25 is rotated 180, in the direction shown in FIGURE 1, from its position against stop 26 to a position against stop 27.

The rotation of crank arm causes the rotation of insulator column 19. Rotation of column 19 causes its gear 22 which is in engagement with gear 24 of link 13 to rotate link 13. The rotation of link 13 results in the rotation of its gear 23 and this rotates insulator column 18 through its engagement with gear 21.

It is, therefore, seen that rotation of crank arm 25 simultaneously rotates switchblades 31 and 32 into the position shown in FIGURE 2 whereby the spherical electrodes 35 and 36 produce a sphere gap between the switchblades. This sphere gap results in a substantially uniform dispersed electrostatic field in the switch open gap and requires a much higher voltage for ashover across the gap than that for a rod gap of the same spacing.

In accordance with the present invention, adequate protection for personnel is provided against flashover in the switch open gap by dispersing the electrostatic field in this region. This dispersed electrostatic field requires a. much higher voltage for lashover than does the concentrated electrostatic eld of a. rod gap. Furthermore, with the dispersed electrostatic field, the switch open gap may be considerably shortened and more easily coordinated with the withstanding ability characteristic of the insulator columns.

As an example of the great saving in space enabled by the instant invention, it has been found that in la 700 kilovolt system requiring an insulator column length of 20 feet, the use of hemispherical electrodes of a radius of three and one half feet permits the provision of a switch open gap of only six feet. It is seen that the switch open gap is considerably shorter than the insulator column and still provides adequate protection against ashover in this gap.

Further protection to personnel working in the switch open gap is provided -by the novel switchblades of the instant invention since any flashover between the switchblades and ground will occur in regions not between the insulator columns. The reason for this is that the spherical electrodes in the region between the insulator columns produce a dispersed electrostatic field while the ends of the switchblades outside this region produce more of a rod gap between these ends of the switchblades and ground. The results of this feature of the switchblades are that any dangerous tlashover will be in a region away from personnel and that the insulator columns will shield the switch open gap from any ionized gases created by ashover between the switchblades and ground.

While the preferred embodiment of the instant novel invention has been described, many variations and modications will now be obvious to those skilled in the art. For example, the sphere gap in the switch open gap may be created by suitable electrodes connected to the upper ends of the insulator columns, rather than having them as integral parts of the switchblades. As pointed out before, these electrodes may be in the form of toroidal rings rather than in the form of spheres.

The embodiments of the invention in which an exclusive privilege or property is claimed or dened as follows:

1. An electric switch comprising: a first and second conductor movable relative to each other to cause engagement and disengagement between said conductors; and means connected to said conductors for producing a dispersed electrostatic eld between said conductors when said conductors are moved relative to each other to their disengaged position and for producing a substantially smooth gap condition between said first and second conductors when said conductors are in their disengaged position.

2. An electric switch as set forth in claim 1 wherein said means for producing a. dispersed electrostatic field produces a substantially uniform electrostatic field.

3. An electric switch as set forth in claim 1, wherein said means for producing a substantially smooth gap condition produces a sphere gap condition between said first and second conductors when said conductors are in their disengaged position.

4. An electric switch as set forth in claim 3 wherein said means `for producing a sphere gap condition includes first and second spherical electrodes.

5. A center break disconnect switch comprising: rst and second switchblades with first and second contacts on one end of each of said switchblades, respectively; and means on the other end of each of said switchblades for producing a dispersed electrostatic field between the switchblades when the switchblades are in their open position.

6. A center break disconnect switch as set forth in claim 5 wherein said means for producing a. dispersed electrostatic field includes first and second spherical electrodes on said first and second switchblades, respectively.

7. A center break disconnect switch as set forth in claim 6 wherein said first and second switchblades are mounted on first and second insulator columns, respectively, and said insulator columns are supported by a base.

8. A center break disconnect switch as set forth in claim 7 wherein the distance between the switchblades when the switch is open is substantially shorter than the insulator columns and yet the breakdown voltage for flashover is greater between the switchblades than from the switchblades to said base across their respective insulator columns.

9. A center break disconnect switch as set forth in claim 7 further comprising means connected to said inl sulator columns Ifor rotating said insulator columns be tween a first and second position whereby said contacts are engaged in said first position and said contacts are disengaged in said second position.

10. A center break disconnect switch as set forth in claim 9 wherein said switchblades and spherical electrodes are integral units and wherein in said first position said contacts on said switchblades are engaged between said insulator columns and wherein in said second position said spherical electrodes are opposite eachother between said insulators to form a sphere gap in the switch open gap.

11. An electric switch comprising: first and second conductors movable relative to each other to cause engagement and disengagement between first and second contacts on one end of each of said conductors; and means connected to said conductors for producing a dispersed electrostatic field between the other ends of said conductors when said conductors are moved relative to each other to cause disengagement between said first and second contacts.

References Cited UNiTED STATES PATENTS 2,135,353 11/1938 Rorden 174-144 X 2,820,086 1/1958 -Nicholas -s 174-140 3,117,192 1/1964 Owens 317-17 X 3,227,830 1/1966 Ransom.

FOREIGN PATENTS 369,956 1923 Germany.

ROBERT K. SCHAEFER, Primary Examiner H. J. HOHAUSER, Assistant Examiner U.S. Cl. X.R.

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