US3588406A

US3588406A - High voltage beaver tail type switch with preinsertion resistor

Info

Publication number: US3588406A
Application number: US772526A
Authority: US
Inventors: Joseph Bernatt
Original assignee: S&C Electric Co
Current assignee: S&C Electric Co
Priority date: 1968-11-01
Filing date: 1968-11-01
Publication date: 1971-06-28
Anticipated expiration: 1988-06-28
Also published as: GB1267102A

Abstract

DURING THE FINAL CLOSING MOVEMENT OF A BEAVER TAIL TYPE SWITCH CONDUCTING ARM MEANS EXTENDING RADIALLY FROM NEAR THE DISTAL END OF THE SWITCH BLADE IS SWUNG INTO JUXTAPOSITION WITH TERMINAL CONDUCTOR MEANS CONNECTED TO A RESISTOR ASSEMBLY MOUNTED ON AND TO ONE SIDE OF THE STATIONARY SWITCH CONTACT TO CONNECT THE RESISTOR ASSEMBLY IN SERIES WITH THE SWITCH BLADE AND LIMIT THE INRUSH CURRENT INCIDENT TO CLOSING OF THE SWITCH.

Description

United States Patent I Inventor Joseph Bernatt Arlington Heights, 111.

Appl. No. 772,526

Filed Nov. 1, 1968 Patented June 28. 1971 Assignee S 8: C Electric Company Chicago. Ill.

HIGH VOLTAGE BEAVER TAIL TYPE SWITCH WITH PREINSERTION RESISTOR 1 Claim, 4 Drawing Figs.

u.s. C1 200/144, ZOO/48A Int. Cl H0111 33/16 200/146,

Field oISearch 146(APR1).48(f0rJ.48(R.P)

[56] References Cited UNITED STATES PATENTS 3,004.1 16 10/1961 Griscom H r. 200/48 3004.1 17 10/ i961 Skoog1und.... 200/146X 3.121491 3/1964 Gorman l.200/48(R)(P)X 3,235,694 2/1966 Thallner 200/144 (APRDX 3.291.947 12/1966 Van Sickle ..200/144(APRI)X Primary Examiner Robert K. Schaefer Assistant Examiner- Robert A. Vanderhye Attorney-Robert R. Lockwood ABSTRACT: During the final closing movement of a beaver tail type switch conducting arm means extending radially from near the distal end of the switch blade is swung into juxtaposition with terminal conductor means connected to a resistor assembly mounted on and to one side of the stationary switch contact to connect the resistor assembly in series with the switch blade and limit the inrush current incident to closing of the switch.

PATENTED JUN28 19m SHEET 1 OF 2 PATENTEU JUN28 l97l SHEET 2 OF 2 HIGH VOLTAGE BEAVER TAIL TYPE SWITCH WITII PREINSERTION RESISTOR This invention constitutes an improvement over the construction disclosed in Mikos et al. US. Pat. No. 3,163,736, issued Dec. 29, 1964i It is desirable to limit the inrush current in'a circuit in energization thereof. This is particularly the case when a capacitor bank is energized from a high voltage circuit or a high voltage electric power transmission line having relatively high capacitance is energized. If .the inrush current is not limited, transient disturbances in the system may be generated which may cause flashover, insulation breakdown, and the like. Further, the closure of the circuit in air may develop objectionable noise incident to formation of arcs on completion of the circuit.

Accordingly, among the objects of this invention are: To provide a new and improved manner for inserting a resistor in series with a high voltage switch during closing movement of its switch blade to limit the inrush current incident to completion of the circuit by the switch; to locate the resistor in such position that it does not interfere with the normal operation of the switch or the line conductor connected to the stationary switch contact and that it can be applied to a switch construction already connected in a high voltage circuit; to apply the resistor insertion assembly to a beaver tail type of switch blade; to mount the resistor assembly on the stationary switch contact to one side of the plane of pivotal movement of the switch blade; to provide conductor arm means extending radially from near the distal end of the switch blade for movement into juxtaposition with terminal conductor means of the resistor assembly to insert the resistor in the circuit during the closing movement of the switch blade; and to provide flexibility' in the connection between the conductor arm means and the terminal conductor means.

According to this invention, a disconnecting switch construction, such as that disclosed in the above identified patent, is modified to insert a resistor in the circuit while the switch is being closed for limiting the inrush current. The switch blade is of the beaver tail type and is arranged to be pivoted about an axis perpendicular to its length toward and away from a cooperating stationary switch contact and also to be pivoted about its longitudinal axis into and out of high pressure contact engagement with the-stationary switch contact. The resistor, that is inserted in the circuit during the closing movement of the switch blade, is selected to have the necessary thermal capacity to accommodate momentarily relatively high current flow that may occur when the circuit is closed on a load requiring relatively large current or on a short circuit. The resistor having such capabilities is enclosed in a housing of porcelain or the like and, at its lower end, is mounted on a bracket in offset relation to one side of the stationary switch contact. The upper end of the housing has mounted thereon terminal conductor means which includes a terminal rod having an intermediate hairpinsection and an elongated depending arcing section that extends in parallel spaced relation to the stationary switch contact. Near the distal end of the switch blade a conducting arm extends radially and, at its distal end, it carries an arcing finger. As the switch blade approaches the switch closed position and before an arc is drawn between it and the stationary switch contact, the arcing finger is juxtaposedto the depending arcing section of the terminal rod. The therebetween is of the order of 0.]25 inches with the result that a current conducting arc is formed therebetween and current starts to flow through the resistor as the switch blade continues to swing toward the switch closed position. The current is limited'. by the resistor and ceases to flow therethrough when the resistor is shortcircuited on contact engagement of the switch blade with the arcing horns of the stationary switch contact. During the final closing movement of the switch blade, it is rotated about its longitudinal axis to move laterally extending ribs or the beaver tail plate section of the switch blade at its distal end into high pressure contact engagement with upstanding inverted U-shaped contact fingers of the stationary switch contact. This movement is accompanied by corresponding rotation of the conducting arm and arching finger away from the depending arcing section of the terminal rod. v

In the drawings: FIG. 1 is a top plan view of a switch construction provided with resistor inserting means embodying thisinvention. FIG. 2 is a a view, in side elevation, of the switch construction shown in FIG. 1 FIG. 3 is a view, in side elevation, of the switch blade and stationary switch contact to demonstrate how the conducting arm means is oriented on the switch blade. FIG. 4 is a view, partly in elevation and partly in section, taken generally along the line 4-4 of FIG. 3.

Referring now particularly to FIGS. 1 and 2 of the drawings, it will be observed that the reference character 10 designates, generally, switch means in which the present invention is embodied. The switch means 10 includes a base, indicated generally at 11, that may be formed of a pair of rolled steel channels suitable secured together. Mounted on the base 11 are a first insulator 12, a second insulator 13, which is rotatable, and a third insulator 14. The second insulator I3 is rotatably mounted on a bearing 15 that is carried by the base 11 and it has an arm 16 extending therefrom for connection to a suitable operating linkage, that is indicated, generally, at 17. It will be understood that, for three phase operation, three of the switch means 10 are mounted on a suitable switching structure in proper spaced relation, depending upon the voltage of the circuit and that suitable operating means, common to the operating linkage 17, is provided for effecting the simultaneous rotation of the second insulator 13 of each switch means 10 for effecting simultaneous operation of the three switch means 10 for either opening or closing the circuit as may be required.

Extending upwardly from and rotatable with the second insulator 13 is a shaft 18. The shaft 18 extends through and is rotatably mounted on a mechanism housing 19. At its upper end the shaft 18 carries a switch crank 20 which is rotatable therewith. The switch crank 20 is pivotally connected to a link 21 that is pivoted at 22 to an arm 23 which extends from a switch blade 24 that forms a part of a disconnecting switch that in indicated, generally, at 25. The switch blade 24 is pivoted at 26 on a bracket 27 which is carried by one wall of the mechanism housing 19. At its distal end the switch blade 24 is arranged to move into and out of high pressure contact engagement with a line contact member, shown generally at 28, which is carried by the first insulator 12. It will be understood that, on rotation of the second insulator 13 y the operating linkage 17, a corresponding rotation of the switch crank 20 is effected for swinging the switch blade 24 out of or into high pressure contact engagement with the line' contact member 28, depending upon-the direction of rotation.

It is desirable that the switch blade 24 be opened only after the circuit has been opened previously by some other means. The reason for this is to prevent the drawing of an arc between the distal end of the switch blade 24 and the line contact member 28 when the circuit is interrupted under load which might result in damage to these parts or in the creation of a fault by arcing over to an adjacent phase or to ground. For this purpose there is mounted between the mechanism housing 19 and a line terminal 31, which is carried by the third insulator 14, a current interrupter that is indicated, generally, at 32. Separable contact means are provided in the current interrupter 32 which are operated by the mechanism within the mechanism housing 19 under the control of the shaft 18.

The line contact member 28 includes inverted U-shaped contact fingers 33 which are suitably mounted on a terminal member 34 from which a line terminal 35 extends for connection to a line conductor. The terminal member 34 is suitably mounted on a line contact member support 36 which is directly supported by the first'insulator 12.

In order to provide for high pressure contact engagement between the switch blade 24 and'the inverted U-shaped contact fingers 33 the switch blade '24 is provided near its distal end with a beaver tail plate section 37 thatis arranged to enter between the contact fingers 33 at an angle when the switch blade 24 is swung toward the switch close position about pivot axis 38 through the pivot 26 on the bracket 27. The pivot axis 38 is at right angles to the longitudinal axis 39 of the switch blade 24. The closing movement of theswitch blade 24 is arrested when it engages a stop 40 and during the final closing action the switch blade 24 is rotated about the longitudinal axis 39 to move the beaver tail plate section 37 to a position at right angles .to the contact fingers 33 and thus into high pressure contact engagement therewith.

With a view to preventing arcing between position switch blade 24 and the contact fingers 33 when the switch blade is swung toward the closed position, inverted U-shaped arcing fingers 41 are mounted on the terminal member 34 and are arranged to be engaged by an arcing tip 42 that projects endwise form the switch blade 24. As the switch blade 24 is swung toward the close deposition-it will be understood that the arcing tip 42 approaches the arcing fingers 41 before coming within arcing distance of the contact fingers 33.

As pointed out above it is likely that there may be a substantial inrush current in the circuit in which the switch means 10 is connected. This may be due to the switch closing on a short circuit, closing on a capacitor bank and the like. In order to limit the inrush current a resistor 44 is arranged be connected in series with the circuit and particularly in series with the switch blade 24 as it is being swung toward the closed position. The resistor 44 is chosen so as to have sufficient thermal capacity to withstand momentarily current flow that is likely to take place therethrough on closure of the switch blade 24. The resistor 44 forms a part of a resistor assembly as indicated, generally, at 45 and may be constructed as disclosed in the copending application of John J. Mlkos, Ser. No. 768,825, filed Oct. 18, 1968. The resistor assembly 45 includes an insulating housing 46 that may be formed or porcelain and it has a lower end terminal 47 and an upper end ter minal 48 between which the resistor 44 is connected. A support plate49, FIG. 1, extends laterally from the lower end terminal 47' and is secured by bolts 50 to a metallic bracket 51 that, in turn, is secured by bolts 52 to line contact member support 36. In this manner the lower end terminal 47 is solidly connected to the line contact member 28. A conductor extension, indicated generally at 53, is connected to the upper end terminal 48. The conductor extension 53 includes a conductor plate 54 that is secured by bolts 55 to the upper end terminal 48. The conductor plate 54 extends angularly and laterally from the upper end of the resistor assembly 45 and has at its distal end a terminal rod that is indicated, generally, at 56 and forms a part of the conductor extension 53. The terminal rod 56 has an end section 57 that extends into an opening 58 near the distal end of the conductor plate 54 and is secured there by set screws 59. The terminal rod 56 has 5 an intermediate .hairpin section 60 which includes a generally semicircular plan section 61, as indicated in FIG. 1, and an inverted U- shaped section in elevation 62 as shown in FIG. 2. This construction provides considerable flexibility in the terminal rod 56. The terminal rod 56 also includes a depending arcing section 63 which is positioned generally parallel to the line contact member 28 and is located in spaced relation thereto as indicated in FIG. I.

By positioning the resistor assembly 45 in offset relation with respect to the line contact member 28 or in offset relation with respect to the plane in which the switch blade 24 is pivoted about axis 38, there is no interference with the operation of the switch blade 24 or with a conductor that may be connected to the line terminal 35. Thus it is possible to apply the resistor assembly 45 to a switch construction that is already connected in service in a high voltage transmission line.

In order to place the resistor 44 in circuit with the switch blade 24 as it is being moved toward the closed position conducting arm means, indicated generally at 66, is provided. The conducting ann means 66 includes aconducting arm 67 that extends radially from the switch blade 24. As shown more clearly in FIG. 4 the conducting arm 67 is secured to a semicircular clamp 68 with which a matingsemicircular clamp 69 cooperates to hold the conducting arm 67 in place on the switch blade 24. Socket head cap screws 70 interconnect the

clamps

68 and 69. In addition a set screw 71 extends through the central portion of the clamp 69 and into the switch blade 24 in order to position accurately the conducting arm 67 thereon.

Near its distal end contact finger 72 extends radially, from the conducting arm 67 and into overlying relation with the depending arcing section 63 of the terminal rod 56 when the switch blade 24 is swung toward the closed position. The contact finger 72 extends through a transverse opening 73 in the conducting arm 67 and is secured in position therein by a set screw 74. Preferably the relation between the depending arcing section 63 and the contact finger 72 is such that a uniform gap of the order of 0.125 inch as indicated at 75 is provided therebetween. This insures that the contact finger 72 can move freely with respect to the depending arcing section 63. The voltage at which the switch means 10 ordinarily operates is such that the relatively small gap 75 is promptly arched over as the switch blade 24 is moved toward the switch closed position.

It is desirable that the conducting arm 67 be located accurately on the switch blade 24 in horizontal to provide the proper relationship between the contact finger 72 and the depending arcing section 63 as the switch blade 24 is swung toward the closed position. This is accomplished by positioning the conducting arm 67 on the switch blade 24 when the switch blade 24, as indicated in FIG. 3, is at an angle of about l0 from its fully closed position. When the switch blade 24 is so located, the conducting arm 67 is clamped in position and such that it extends horizontally or parallel to the base 11, assuming that it is in a horizontally position. Then the cap screws 70 are tightened and the set screw 71 is screwed into place to hold positively the conducting arm 67 in position on the switch blade 24.

As the switch blade 24 is swung toward the switch closed' position about pivot axis 38 on rotation of the switch crank 20 as the result of the rotation of the second insulator 13, the beaver tail plate section 37 is located at an angle of about 30 with respect to the horizontal. This condition is maintained as the switch blade 24 is rotated to the position shown in FIG. 3 which also is shown in FIGS. 1 and 2. This facilitates entry of the beaver tail plate section 37 between the contact fingers 33. As the movement of the switch blade 24 continues about the pivot axis 38, the distal end of the switch blade 24 engages the stop 40. Continued movement of the switch crank 20 effects pivotal movement of the switch blade 24 about the longitudinal axis 39 to position the beaver tail plate section 37 substantially horizontal or at right angles to the contact fingers 33. This is accompanied by a corresponding movement of the conducting arm 67 and contact finger 72 away from the depending arcing section 63 to the position indicated by broken lines for the contact finger 72 in FIG. 1.

As soon as the contact finger 72 approaches the upper end of the depending arcing section 63 of the terminal rod 56 in the closing movement of the switch blade 24, an arc is established therebetween and current begins to flow through the resistor 44. Because of its resistance this current flow is limited and there is a corresponding reduction in the inrush current. The closing movement of the switch blade 24 continues with the inrush current being limited by the resistor 44. The arcing tip 42 engages the arcing fingers 41 and shortly thereafter the beaver tail plate section 37 engages the contact fingers 33 with the result that the resistor 44 is short circuited and current no longer flows through it.

When the second insulator I3 is rotated in a reverse direction there is a corresponding reverse movement of the shaft 18 and of the switch crank 20. The arrangement is such I that, before the switch blade 24 disengages the line contact member 28, the current interrupter 32 is operated to open the circuit under the control of mechanism within the mechanism housing 19. Then continued rotation of the lecond insulator 13 in an opening direction swings the switch blade 24 out of high pressure contact engagement with the contact fingers 33 and to an open circuit position which is substantially at right angles to its switch closed position. During the final portion of the opening movement of the switch blade 24, the mechanism within the mechanism housing 19 is arranged to reclose the circuit interrupter 32. Thus, in the switch open position, the contacts of the circuit interrupter 32 are closed while the switch blade 24 occupies a generally upright position.

As pointed out above the resistor assembly 45 is offset to one side of the line contact member 28. In addition it is inclined away from the line contact member 28 in order to permit the construction of the terminal rod 56 with substantial flexibility between-the upper end of the resistor assembly 45 and the depending arcing section 63.

I claim:

1. A resistor inserting switch construction having a stationary switch contact and a cooperating switch blade pivoted about an axis perpendicular to its longitudinal axis for movement toward and away from said stationary switch contact, said switch construction being characterized by a resistor assembly mounted at one end to one side of the plane of pivotal movement of said switch blade on said stationary switch contact and electrically connected thereto,

terminal conductor means connected to and extending from the other end of said resistor assembly with its distal end forming an arcing section disposed in offset generally parallel relation to said stationary switch contact,

conducting arm means carried by and extending radially from said switch blade near its distal end and arranged to be moved into juxtaposition to said arcing section of said terminal conductor and form a current conducting arc therebetween to connect said resistor assembly in series with said switch blade as it is swung to switch closed position with saidstationary switch contact, and

means pivotally mounting said switch blade about its longitudinal axis for movement at its distal end into high pressure contact engagement with said stationary switch contact and swinging said conducting arm means away from said arcing section while said switch blade is pivoting into said high pressure contact engagement.