US3148260A

US3148260A - Disconnecting switch having surge suppressing impedance

Info

Publication number: US3148260A
Application number: US185575A
Authority: US
Inventors: Jr Chester W Upton
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1962-04-06
Filing date: 1962-04-06
Publication date: 1964-09-08
Anticipated expiration: 1981-09-08
Also published as: GB974156A; BE630613A

Description

Sept. 8, 1964 c. w. UPTON, JR 3,148,260 uxscoumscmc SWITCH HAVING SURGE SUPPRESSING IMPEDANCE Filed April 6. 1962 WITNESSES lo INVENTOR Chester W. Upton, Jr

ATTORNEY United States Patent 3,143,260 DHEECONNECTING SWTTCH HAVING SURGE SUPPRES1NG IMPEDANCE Chester W. Upton, In, Penn Township, Westrnoreiand County, Pa, assignor to Westinghouse Eiectric Corporation, East Pittsburgh, Pa, a corporation of Pennsylvania Filed Apr. 6, 1962, Ser. No. 185,575 6 Ciairns. (Ci. 200-146) This invention relates, generally, switches and, more particularly, to a switch having a surge suppressing impedance or resistor inserted into circuit during the opening operation of the switch.

When applied on a power system having a high voltage, such as 345 kv. and higher, a surge suppressing resistor or impedance of the type described in Patent No. 3,004,116 and Patent No. 3,004,117, issued October 10, 1961, to S. B. Griscom and J. W. Skooglund, respectively, has had a limited effectiveness in eliminating overvoltages on the system during switching operations of unloaded buses and lines. The reason that it was not completely effective was that arcing occurred between the switch blade tip and the break jaw assembly as they separated and before any external resistance was inserted in the arc path. In order to eliminate the overvoltages, an external resistance must be introduced into the circuit before arcing is initiated.

An object of this invention is to provide for inserting a surge suppressing impedance or resistor in the circuit through a disconnecting switch prior to the establishing of an arc during opening of the switch.

Another object of the invention is to provide an auxiliary blade which cooperates with the main blade of a disconnecting switch to insert a surge suppressing resistor in the circuit through the switch.

A further object of the invention is to provide a corona shield for a spring-biased auxiliary blade on a disconnecting switch.

Still another object of the invention is to provide for resetting the spring-biased auxiliary blade during closing of the main blade of the switch.

Other objects of the invention will be explained fully hereinafter or will be apparent to those skilled in the art.

In accordance with one embodiment of the invention, a spring-biased auxiliary or flipper blade is so incorporated in a switch and impedance assembly that a parallel circuit through the flipper blade and the first stage or section of the impedance assembly becomes a series circuit immediately upon breaking the circuit through the main contacts of the switch. Thus, there is no arcing until after the main switch blade has completely cleared the break jaw of the switch and is disengaged from the flipper blade which is left within the protective shield of the first stage corona shield and areing contact. At this time the arc has in series with it the first stage of the impedance assembly, thereby damping any overvoltage associated with restrikes and thus protects the system.

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

FIGURE 1 is a view, partly in side elevation and partly in section, of a portion of a disconnecting switch and surge suppressing resistor assembly embodying the principal features of the invention;

FIGS. 2 and 3 are views, in section, taken along the lines II-II and III-III, respectively, in FIG. 1; and

FIG. 4 is a view, in plan, looking along the line IV-IV in FIG. 1.

Referring to the drawing, and particularly to FIG. 1,

to disconnecting the disconnecting switch and insulator supports shown therein are generally of the type described in the aforesaid Patent 3,004,117. Likewise, the impedance assembly is generally of the type described in Patent 3,004,117. As described in that patent, the impedance assembly functions as a surge suppressing resistor during opening of the disconnecting switch.

The portion of the disconnecting switch shown in the present drawing comprises a supporting insulator stack 10 upon which is mounted a combination break jaw support, surge suppressor support and terminal pad 11 composed of suitable conducting material, such as copper. A terminal connector 12 is attached to what may be called a terminal pad 11 for connecting a power conductor (not shown) to the switch. A stationary contact or break jaw 13 is attached to the terminal pad 11. A main switch blade 14 engages the stationary contact 13 when the blade is in the closed position. A generally hemispherically-shaped corona ball 15 is secured to the end of the blade 14.

The blade 14 is of the swinging type and the ball 15 follows an arcuate path 16 during opening and closing of the switch blade. An actuating mechanism (not shown) which may be of any suitable type such as, for example, the one described in Patent 2,436,296, issued February 17, 1948, to H. W. Graybill and P. Olsson, may be utilized for operating the switch blade 14. The blade operating mechanism may be supported by insulator supports similar to the insulator stack 10. A power conductor may be connected to the blade operating mechanism thereby completing an electric circuit through the switch when the main blade 14 is closed.

As described in the aforesaid Patent 3,004,117, the impedance assembly comprises three resistor sections 17 which are inserted in three successive stages A, B and C in series with the are drawn during opening of the switch. Each resistor section 17 may comprise a hollow insulating cylinder 18 inside of which is disposed a suitable resistance element which may be of the carbon block type. The cylinder 18 may be composed of porcelain or other suitable insulating material, such as an epoxy resin. A supporting casting 19, having an external flange 20 thereon, may be cemented to each end of each cylinder 18. The bottom casting 19 of the lowermost resistor section 17 may be attached to the terminal pad 11 by mounting bolts 21. The mounting castings 19 on the adjacent ends of the resistor sections 17 may be joined together by similar mounting bolts 21 which extend through the flanges 20 on the mounting castings. If desired, a single wire-wound resistor with taps thereon may be utilized in place of separate sections of resistance.

A generally U-shaped corona shield 22 is attached to a mounting plate 23 which is disposed between the mounting castings 19 of the resistor sections 17 of the impedance stages A and B. As shown in FIGS. 1 and 2, the legs of the shield 22 are bent inwardly and upwardly. The shield 22 is preferably formed from a hollow metal tube. A generally ring or doughnut-shaped corona shield 24 is attached to a mounting plate 25. The plate 2.5 is secured between the mounting castings 19 for the resistor sections 17 of impedance stages B and C. A generally ovalshaped corona shield 26 is attached to a mounting plate 27. The plate 27 is attached to the top casting 19 of the resistor section 17 of the impedance stage C. The

corona shields

24 and 26 are also formed from cylindrical metal tubing.

Spaced electrostatic side shielding or corona rings 28, constituting a break jaw corona shield, are disposed on opposite sides of the stationary contact 13. These shields 28, also provide shielding for the flipper or auxiliary blade in the closed position. The two rings 28, only one of which is shown, may be attached to the terminal pad 11.

The rings 28 are preferably formed from cylindrical metal tubing.

As shown in FIG. 1, the supporting plate 23 and the

corona shields

24 and 26 are spaced from the arcuate path 16 traveled by the end 15 of the main blade 14. Thus, these members function as arcing contacts during opening of the switch. The are transfers from one arcing contact to the next as the blade 14 swings open. In this manner, the resistance of the impedance assembly is inserted into the circuit by increments until the entire resistance is in the circuit;

However, as explained hereinbefore, in order that the surge suppressing resistor may function most effectively in eliminating overvoltages, resistance must be introduced into the circuit before any arcing is initiated. In order to accomplish the insertion of resistance into the arc path before any arcing takes place, a spring-biased flipper or auxiliary switch blade 31 is disposed to engage I the end 15 of the main switch blade 14 when the main blade engages the break jaws or stationary contact 13. As shown most clearly in FIGS. 1 and 2, the auxiliary blade 31 is generally of a hair-pin shape with the ends of its legs formed into a torsion spring and attached to the mounting plate 23 to bias the blade 31 against the corona ball 15 on the main blade 14. Thus, the first stage A of the impedance assembly is connected in parallel circuit relation with the circuit through the break jaw 13 when the main blade 14 is closed. The parallel circuit extends through the auxiliary blade 31 and the lowermost resistor section 117 to the terminal pad 11 to which the break jaw 13 is also attached. It, however, carries negligible current in the closed position since it is a high resistance path relative to the main switch blade contacts.

During opening of the main blade 14 the auxiliary blade 31 follows the main blade and remains in contact with the ball 15 until the auxiliary blade 31 engages the mounting plate 23 which functions as a stop member to stop the upward movement of the auxiliary blade 31, thereby separating the auxiliary blade from the main blade as the main blade continues to travel upwardly. When the main blade 14; is completely disengaged from the stationary contact 13, the circuit to the resistor sections 17 becomes a series circuit and the first increment of resistance is inserted in series with the arc to be initiated after the end 15 f the main blade 14 leaves the auxiliary blade 31.

In this manner the auxiliary blade 31 prevents arcing Therefore, the auxiliary blade 31 is encompassed by the shield 22 when the blade 31 is in the open position.

During opening of the switch, an arc is first drawn between the auxiliary blade 31 or the corona shield 22 which function as an arcing contact and the main switch blade corona ball as the main blade travels upwardly. At this time, the first stage A of the impedance assembly is in series with the arc path. As the main blade moves upwardly, the arc transfers to the corona shield 24 which functions as an arcing contact. At this time the resistance of the second stage B is added to the first stage A which are now connected in series in the arc circuit. As the blade 14 continues upwardly, the arc transfers to the corona shield 26 thereby connecting the third stage C until after the main switch blade has completely cleared the break jaw and the corona shields 28. As explained hereinbefore, the insertion of resistance into the circuit before any arcing takes place makes the surge suppressing resistor most effective in eliminating overvoltages or surges during the interruption of the circuit through the disconnecting switch. When the main switch blade 14 moves towards the closed position, the corona ball 15 retrieves the auxiliary blade 31 from within the first stage corona shield 22 and drives it downward against the torsion spring bias to the closed position shown in FIG. 1 of the drawing.

On switches utilized at 345 Inf. and higher, it is essential that all exposed external surfaces have relatively large radii in order to assure an acceptable radio interference and corona level. The auxiliary blade which incorporates its own torsion spring must inherently be of small diameter material. It is, therefore, necessary for the auxiliary blade to be within the protective shield of the jaw corona shield 28 when the switch is closed. In the open position, the auxiliary blade comes to rest within the protective shield of the first stage corona shield and arcing contact. Therefore, it is shielded in both the open and the closed positions and is within the protective Zone of both shields during operation. It will be noted that the auxiliary bade 31 is bent in a manner similar to the manner in which the legs of the shield 22 are bent.

in the arc circuit. As the main blade 14- and corona ball 15 which serves continuously as an arc terminal until the time of arc extinction continue to rise still further, the arc lengthens until it can no longer sustain itself and is extinguished.

The particular numerical value of the resistance in ohms employed in the impedance assemblage depends upon the circuit components and the voltage. Its electrical dimensioning is described in detail and claimed in the aforesaid Patent 3,004,116. Generally, the resistance value is preferably several times the surge impedance of the circuit connected to the disconnecting switch. The current magnitude encountered in the application of switches of the present type is relatively low. Therefore, there isno burning or pitting of the auxiliary blade 31, corona ball 15 and the corona shields 22, Z4, 26 which function as arcing contacts.

As explained hereinbefore, the present invention provides for inserting resistance into the circuit through a disconnecting switch before any arcing is initiated during opening of the switch. In this manner, the effectiveness of a surge suppressing resistor in eliminating overvoltages or surges on a power system during switching operations is increased. Any overvoltage associated with restriking of the arc drawn during opening of the switch is damped by the external resistance and the system is protected.

Since numerous changes may be made in the abovedescribed construction 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 drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. A disconnecting switch comprising a relatively stationary contact, a swinging main switch blade engageable with the stationary contact to complete an electrical circuit through the switch and movable to open the switch, a resistor having one terminal electrically connected to the stationary contact, a spring-biased auxiliary switch blade electrically connected to another terminal of the resistor, said auxiliary switch blade being disposed to engage the main switch blade to establish a circuit through the resistor in parallel with the circuit through the stationary contact when the main blade engages the stationary contact and to follow at least a portion of the movement of said main switch blade, said parallel circuit becoming a series circuit through the main blade, the auxiliary blade and the resistor as soon as the main blade is separated from the stationary contact during opening of the switch, and stop means for disengaging the auxiliary blade from the main blade after the main blade is completely separated from the stationary contact.

2. A disconnecting switch comprising a relatively stationary contact, a swinging main switch blade engageable with the stationary contact to complete an electrical circuit through the switch and movable to open the switch, a resistor having one terminal electrically connected to the stationary contact, an auxiliary switch blade electrically connected to another terminal of the resistor, spring means for biasing the auxiliary blade against the main blade to establish a circuit through the resistor when the main blade engages the stationary contact to cause said auxiliary blade to follow the main blade for at least a portion of the movement of said main blade, said circuit through the auxiliary blade and the resistor being maintained in series with said main blade immediately upon and during opening of the switch until after the main blade is completely separated from the stationary contact, and stop means for disengaging the auxiliary blade from the main blade when the main blade has traveled a pre determined distance from the stationary contact.

3. A disconnecting switch comprising a relatively stationary contact, a swinging main switch blade engageable with the stationary contact to complete an electrical circuit through the switch, a resistor having one terminal electrically connected to the stationary contact, an auxiliary switch blade electrically connected to another terminal of the resistor, spring means for biasing the auxiliary blade against the main blade to establish a circuit through the resistor when the main blade engages the stationary contact, said circuit through the auxiliary blade and the resistor being maintained during opening of the switch until after the main blade is completely separated from the stationary contact, stop means for disengaging the auxiliary blade from the main blade when the main blade has traveled a predetermined distance from the stationary contact, and a corona shield encompassing the auxiliary blade when it engages the stop means.

4. In a disconnecting switch, in combination, a relatively stationary contact, a main switch blade engageable with the stationary contact to complete an electrical circuit through the switch and movable to open the switch, said main blade being movable through an arcuate path of travel, an impedance assembly comprising a plurality of resistor sections disposed adjacent the stationary contact and extending therefrom in the general direction of said path of travel, a plurality of arcing contacts tapped into said impedance assembly to insert impedance into the circuit during opening of the switch, said arcing contacts being spaced from said arcuate path of travel, an auxiliary switch blade engaging the main blade to connect one resistor section in the circuit when the main blade is closed, spring means biasing the auxiliary blade against the main blade to follow the movement of said main blade during at least a portion of the movement of said main blade and to maintain the circuit through the auxiliary blade and the resistor in series with said main switch blade immediately upon and during the opening of said switch until after the main blade is separated from the stationary contact during opening of the switch and corona shielding means disposed on opposite sides of said stationary contact to shield said auxiliary blade when said switch is in the closed position.

5. In a disconnecting switch, in combination, a relatively stationary contact, a main switch blade engageable with the stationary contact to complete an electrical circuit through the switch and movable to open the switch, said main blade being movable through an arcuate path of travel, an impedance assembly comprising a plurality of resistor sections disposed adjacent the stationary contact and extending therefrom in the general direction of said path of travel, a plurality of arcing contacts tapped into said impedance assembly to insert impedance into the circuit during opening of the switch, said arcing contacts being spaced from said arcuate path of travel, an auxiliary switch blade engaging the main blade to connect one resistor section in the circuit when the main blade is closed, spring means biasing the auxiliary blade against the main blade to cause said auxiliary blade to follow said main switch blade during at least a portion of the movement thereof to maintain the circuit through the auxiliary blade and the resistor in series with the main switch blade until after the main blade is separated from the stationary contact immediately upon and during opening of the switch, and stop means for disengaging the auxiliary blade from the main blade when the main blade has traveled a predetermined distance along said arcuate path.

61 In a disconnecting switch, in combination, a relatively stationary contact, a main switch blade engageable with the stationary contact to complete an electrical circuit through the switch, said main blade being movable through an arcuate path of travel, an impedance assembly comprising a plurality of resistor sections disposed adjacent the stationary contact and extending therefrom in the general direction of said path of travel, a plurality of arcing contacts tapped into said impedance assembly to insert impedance into the circuit during opening of the switch, said arcing contacts being spaced from said arcuate path of travel, an auxiliary switch blade engaging the main blade to connect one resistor section in the circuit when the main blade is closed, spring means biasing the auxiliary blade against the main blade to maintain the circuit through the auxiliary blade and the resistor until after the main blade is separated from the stationary contact during opening of the switch, stop means for disengaging the auxiliary blade from the main blade when the main blade has traveled a predetermined distance along said arcuate path, and corona shielding means encompassing the auxiliary blade when it engages the stop means.

References Cited in the file of this patent UNITED STATES PATENTS 1,563,833 Christensen Dec. 1, 1925 1,861,129 Milliken May 31, 1932 2,571,864 Graybill Oct. 16, 1951 2,840,671 Gietfers June 24, 1958 3,004,117 Skooglund Oct. 10, 1961

Claims

1. A DISCONNECTING SWITCH COMPRISING A RELATIVELY STATIONARY CONTACT, A SWINGING MAIN SWITCH BLADE ENGAGEABLE WITH THE STATIONARY CONTACT TO COMPLETE AN ELECTRICAL CIRCUIT THROUGH THE SWITCH AND MOVABLE TO OPEN THE SWITCH, A RESISTOR HAVING ONE TERMINAL ELECTRICALLY CONNECTED TO THE STATIONARY CONTACT, A SPRING-BIASED AUXILIARY SWITCH BLADE ELECTRICALLY CONNECTED TO ANOTHER TERMINAL OF THE RESISTOR, SAID AUXILIARY SWITCH BLADE BEING DISPOSED TO ENGAGE THE MAIN SWITCH BLADE TO ESTABLISH A CIRCUIT THROUGH THE RESISTOR IN PARALLEL WITH THE CIRCUIT THROUGH THE STATIONARY CONTACT WHEN THE MAIN BLADE ENGAGES THE STATIONARY CONTACT AND TO FOLLOW AT LEAST A PORTION OF THE MOVEMENT OF SAID MAIN SWITCH BLADE, SAID PARALLEL CIRCUIT BECOMING A SERIES CIRCUIT THROUGH THE MAIN BLADE, THE AUXILIARY BLADE AND THE RESISTOR AS SOON AS THE MAIN BLADE