US2089285A - Circuit breaker - Google Patents

Description

Aug. 10, 1937. H. MILLIKEN 2,089,285

CIRCUIT BREAKER Filed June 2'?, 1954 l1 Sheets-Sheet l /7/4//1/ L /NE 'INVENTOR ATTORNEYSA Aug- 10, 1937- H. MILLIKEN 2,089,285

CIRCUIT BREAKER Filed June 27, 1954 ll Sheets-Sheet 2 Aug; 1o, 1937. MILUKEN 2,089,285

CIRCUIT BREAKER Filed June 2'7, 1934 ll Sheets-Sheet 3 Aug. 1o, 1937.

v Rec-.Lore VALVE! IT OM LIDE VALVE l2 H. MILLIKEN CIRCUIT BREAKER Filed June 27, 1934 ll Sheets-Sheet 5 H. MlLLiKEN CIRCUIT BREAKER Aug. l0, 1937.

Filed June 2'?, 1954 11 sheets-sheet 6 A ug- 10, 19373 H. MILLIKEN 2,089,285

v CIRCUIT BREAKER Filed June 27, 1954 ll Sheets-Sheet 7 (1km/amg a Aug. 10, 1937.

H. MILLIKEN CIRCUIT BREAKER Filed June 27, '1934 ll Sheets-Sheet lO Aug. 10, 1.937. H, M|| |KEN 2,089,285

CIRCUIT BREAKER Filed June 27, 1954 ll Sheets-Sheet ll F om fron/AGE TANK |70 nr) u) www] l Patented Aug. 10, 1937 uiirrrzl) STATES PATENT OFFICE Claims.

This invention relates primarily to circuit breakers used for interrupting heavy short-circuit currents on large power systems. An important objectA of the invention is to eliminate the lire hazard of oil commonly used for extinguishing the arcs in the interruption of such currents. In this invention, compressed airis used instead of oil for extinguishing the arcs. Compressed air circuit breakers which have heretofore been used have certain weaknesses and limitations, to overcome which, is an important purpose of this invention. With any type of circuit breaker it is necessary to provide a disconnecting switch in 'series with the circuit breaker in order to isolate the breaker from the live circuit when maintenance work is required. The invention provides for removal of voltage stress with great rapidity by improved coordination of currentinterrupting means and a disconnecting switch.

Another important object of the invention is to provide an improved circuit breaker designed to facilitate building up of a current interrupter assembly to accommodate increases in voltage.

Other objects of the invention will appear hereinafter.

In the drawings:

Fig. 1 shows diagrammatically the general arrangement of the circuit-breaker in the circuit, with its auxiliary equipment in closed position.

Fig. 2 is an end elevation, Fig. 3 a front elevation, and Fig. 4 a top plan, of one form of the circuit-breaker^ shown schematically in Fig. 1, this form being particularly adaptedfor use ,with circuits carrying voltages of the order of 132,000 to 154,000 volts. y

Fig. 5 is an end elevation, Fig. 6 a front elevation, and Fig. 7 a top plan of another form of the circuit-breaker, this form being particularly adapted for use with circuits carrying voltages of the order of 275,000 volts.

Fig. 8 illustrates the constructiomgin elevation and partially in section, of a transformer employed with my circuit-breaker.

Fig. 9 shows schematically in plan the ,arrangement of the primary winding of the transformer shown in Fig. 8. f

Fig. 10 is a horizontal section through an air channel of my current-interrupter, taken on the ,line Ill-I0 of Fig. 13.

Fig. 11 is a vertical section through my current-interrupter, taken on line Il-il of Fig. 10. y Fig. 12 is, another 'horizontalsection through an air channel, taken on the line I2|2 of Fig. 13. j

(Cl. 20o-81) Fig. 13 is a. vertical section on line I3-i3 of Fig. 12, the damper32 being open or removed to show the grid 3l.

Fig. 14 is a vertical section on the line l4-I4 of Fig. 1o. 5

Fig. 15 is a vertical sectional view of the air valve used in conjunction with my circuit-breaker.

Fig. 16 is a diagram of a means for opening the automatic disconnecting switch.

' Referring to Fig. 1, the main, high voltage, alternating current may be considered as coming in from the main line. on the left of the iigure, to insulator |40, passing through the automatic disconnecting switch I, through a transformer 2,A thence through an automatic transfer switch or by-pass switch 3, thence through a current transformer 4, a non-automatic disconnecting switch 5 to the outgoing main line on the upper right of the figure. Transformer 2 is alternative to transformer 4, only one being re- 20 quired. In shunt with by-pass switch 3 is the current interrupter K which includes contacts 6, movable contacts A'1, held closed by springs 8, current-reducing resistors RI and R2, potentialequalizing-resistors R3, and resistor-tap-contacts 9 and 9a.

As shown in Figs. 1 and 4, the disconnecting switch l includes a horizontal switch blade Ic, which in closed position engages a contact borne by an insulator N0. The blade forms part of a horizontally foldable linkage mechanism including the links Ib and ld and the lever la. Link ib is pivotally connected at one end to a crank arm which is rotatable about a vertical axis by rotation of n insulator stack 114. 'Ihe opposite end of linka?) is pivotally connected to one end of the lever la Whose opposite end is in turn pivotally connected to the inner end of the switch blade. Between its ends, the lever la is pivotally supported or fulcrumed at a ilxed point. The linkr Id is pivotally connected at one end to the switch blade at a point spaced inward from the connection of the lever la with the blade. At its opposite end the link Id is pivotally supported at a iixed point. The switch blade is shifted to open position by rotation of the insulator stack I4, through 180. The link Ib is so arranged as to dispose its ends on dead centre with respect to the axis of insulator I4 in both the open and closed positions of the switch blade, thereby lool:- ing the switch mechanism against accidental drifting. The purpose of the folding mechanism is to maintain the same space between 4phases with the switch open or closed, and at the same time providefor horizontal movement of switch urged into contact with its cooperating horn by a spring 21. The resistor tap contacts 9 and 9a are spaced along the walls of the arc chutes opposed to theouter edges of the horns 1. The resistor taps comprisegranular resistor material contained in an insulating tube under spring pressure, the several sections of the resistor having resistivities best suited to their sequence in the circuit. The outer edge of each horn and the opposed insulation wall having the resistor tap contacts, in eiect, define a narrow arc chute, the edge of the horn forming a movable wall of the chute. For cushioning the opening movement of the horns, there are provided for each pair of hornsl a brake strip 28, with which the horns make wiping frictional contact, and a bumper 29.

Each diffusion chamber 30 has an air cooling grid 3l, formed of thin superposed metal strips spaced very close together. The grid is disposed so that the air discharged into the chamber 30 from the arc chutes must pass through the grid on its way out of the chamber. A damper 32 is provided at the outlet of each diffusion chamber to keep out snow, dust, insects, etc. The air blast opens the dampers and they close by their own weight.

The insulation body of each of the superposed interrupter units may be built up of superposed horizontal sheets of different grades of completely arc-prooi material, the intermediate sheets being of material selected chieiiy for its high dielectric strength. TheA structure is vheld securely together by large diameter rods 30 of insulating material. These rods resist the air pressure and stresses of operation. Weatherproof insulating material covers the structure and has shields 33 to prevent the formation of a continuous coating of snow, sleet, etc. The entire interrupter structure is supported by insulator stacks.

It is an important feature of the interrupter that the electrical stress is vertical, not horizontal. A horizontal top surface cannot be kept free .from a continuous covering of snow, forming a conducting path which would cause a short circuit from end to end, whereas the vertical sides can be protected by the shields above noted. Additional advantages of the vertical arrangement are: elimination of bending stress on the insulating rods, and simplification of base plate construction by the use of steel instead of insulation material.

The interrupter operates as follows: A strong `blast ofair admitted to the, pipe i8 flows into'the conduit formed by the bores 25 of the interrupter units and said conduit distributes the air to all of the arc chutes. The first effect when the air blast arrives at the entrance of an arc"chute is to blow the movable contactor 6 outward laterally away from the horn 1. Contactor 6 bears an auxiliary or arcing contacter 6a which separates from horn 1 slightly after 6, thereby saving 6 from being burnt by the arc. Said contacter moves away from the horn before the horn is moved by the air blast, because it has less inertia than the horn. The arc resulting from said lateral movement of the contactor is blown along the narrow passage between the horn and the opposed xed wall` of the chute, having the resistor tap contacts 9 and 9a. The arc makes electrical contact with said taps successively, thus shunting current awayI from the-.preceding contact and reducing the total current by the insertion of resistance in the cir cuit. The arc carrying the reduced current is broken when one end is blown toward the far end of the horn, while the other end remains on contact 9a. The conditions during that moment are ideal for the breaking of the arc, viz., the cross section of the arc cannot be greater than the narrow passage (about one-half square inch); the length of the arc (unless it is broken sooner) is relatively great, extending from 9a to the far end of the horn and the full velocity and pressure of the air blast extends from end to end of the arc, thereby obtaining a maximum deionizing, or reduction in conductivity, and cooling effect with a` minimum quantity of air.

While the foregoing is taking place, the horn 1 is moving outward under the air pressure which overcomes the force of the spiral spring 8. The horn is shifted to fully open position in about onehundredth of a second and it is held open by the air blast until after the disconnecting switch I has opened and removed voltage stress from the interrupter. There is a separation of about twelve inches between the end of the horn and contact 9a, which provides a liberal factor of safe ty against restriking of the arc in the arc chute 26. The horn in all of its positions is spaced out of contact with the tap contacts 9 and 9a.

The horns being connected in pairs, as shown,

the two arcs discharged from the same pair oi horns are of the same electrical potential and cause no short circuit when theylare blown together in the same diffusion chamber 30, one chamber for each pair of horns being provided. The arcs or incandescent gases from diierent pairs of horns are prevented from blowing together until after they have been thoroughly mixed `with the blast of cold air and thus rendered safely rnon-conducting. The diffusion chambers accomplish this very completely by providing a large space in which turbulent action iscaused by several abrupt changes in direction. The grids 3| are also a very effective cooling means.

To guard against possible condensation of moisture over the interior surfaces oi the interrupter structure, a small quantity of air, which has been thoroughly dried and slightly heated, is passed continuously through the interrupter, to prevent the entrance of moist air. This supply of dry air is obtained from leakage past the automatic valves, as will be described hereinger, and/or directly from the main air tank The interrupter described has this fundamental advantage: The entire range of commercial transmission voltages (from 12,000 to 275,000 volts) can be properly served with one design of interrupter element or unit only six inches high and four feet square. A large number of these elements can be stacked up in a relatively small space. For 138,000 volts, the stack is only about forty inches high, and for 275,000 'mits about seven `feet high. When' still higher voltages are required, they can be served by simply adding a few more similar elements or units.

For the 275 kv. circuit breaker, there is pro` vided an improved arrangement of insu'iatcr stacks to support the interrupter. For said voltage, eight standard insulators in series are required in each stack, making a height of about eleven feet, rendering such a stack relatively weak to resist bending stress (about 600 lbs. ultimate strength), whereas the stack has a vdirect tensile strength of about 23,000 ibs. In the present structure, for greater strength, the supporting insulators are diagonally or obliquely central space beneath the interrupter. The .iu-

energizing an electromagnet is determined by the necessary inductance of the coil which delays' the rise of the current to its final value. Either type of electromagnet may be used with either valve 60 or 6I.

Valve 60 has entrance ports 49 which completely surround piston 48 which closes the ports in the position shown. Electromagnet 43, having coil 44 normally carrying current, energizes magnetic circuit 45 holding movable armature 46 down against its pole-piece. Breaking magnet current releases 46 and compressed spring 41 snaps piston 46 upward about fsths of an inch, uncovering ports 49 and discharging the air from space 50.

Valve 6I has a rubber seat-62 with an opening of 21/2 inch diameter normally closed by a metal cip 63 held up by air pressure in space 64 closed by a piston-type of valve similar to valve 60. Energizing electromagnet 59 lifts the piston, discharges air from space 64 and air pressure in space 53 blows cup 63 downward inch discharging air from space 53 through an openingof 3 sq. in. cross section.

The automatic closing of valve I1 takes place in the following manner:

Referring again to Fig. 1, the pressure of the air blast moves piston Il to the left admitting air pressure to the upper end of cylinder I3, (opening automatic switch I) and thence to pipe 65, which is of sufficiently large diameter (and volume) to cause a short delay in pressure rise (to .allow time for switch I to open before the air blast is shut off). Air pressure arriving via pipe 55 at valve I1, enters small cylinder 66 forcing piston 48 down closing Valve 60, enters cylinder 61 forcing its piston down closing the discharge from space 64, passes through check-valve 66 building up pressure in spaces 50 and 53, closing 40 disc 4I shutting off the air blast. Space 64 is relled by air through check-valve 69 and pipe 10,

thereby forcing cup 63 upward closing valve 6 I.

Y So long as switch I remains open, the air pressure conditions remain as just described. When air pressure is admitted to the lower end of cylinder I3 (Fig. l.) (to reclose switch I) air pressure is discharged from pipe 65 to atmosphere through cylinder I3 and slide valve I2, which leaves valve I1 ready to open automatically if and when required. In order to reduce friction of piston 43 and the piston in cylinder 61 to a minimum, no packing is used and there is a continuous slight leakage. In order tosupply this leakage and maintain pressure in space 50, 53 and 64 so that valve 6I and disc 4I will remain closed, a continuous supply of compressed air is taken through opening 1 I, pipes 12 and 13 to spaces 53 and 50, and through needle valve 14 and pipe 10 to space'64. Needle valve 14 is adjusted to pass air at the minimum rate required to hold 63 closed, so as not to unnecessarily retard 63 when it opens. Leakage of high pressure air into the chamber at the under side of the valve I1 flows out through a pipe 11 65 which delivers into the air blast conduit I8, as shown in Fig. 1. By means of a valve 16, flow of lsaid air may be adjusted to provide a continuous flow of a small amount of warm air to the interrupter to dry out its interior. The air so delivered will, of course, have insufficient pressure to operate the-interrupter.

Fig. 8 is an elevation (partly in section) of the current-potential transformer 2 as itis applied to Y a, circuit breaker of the type shown in Figs. 2, 3 and 4. 'Ihe two stacks of insulators 90 are the same stacks I4 which support the interrupter. The insulators are of the type commonly used and have iron caps and pins, which are therefore magnetic. Steel channel 9I is part of the structure supporting the interrupter, and steel plate 92 is the baseplate of the interrupter. Pedestals 93, supporting plate 92 are iron. These existing iron and steel supports form a circuit consisting of magnetic material except the gaps of porcelain at the insulators. Coils 94, shown in section in Fig. 8 and in plan (dlagrammatically) in Fig. 9, are preferably made of thin wide copper bars bent into spirals, insulated from the adjacent parts. The two coils 94 are connected in series with the main high-tension circuit, the polarity of the coils being such as to produce magnetic elds in the direction shown. The greater part of the induced magnetic ux follows shorter paths through the air and does not reach the bottom channel 9| and secondary coils 95 and 96. However, a suiclent portion of the flux passes through coils 95 and 96 to induce a voltage suitable for operating an ordinary voltmeter or potential coil of an ordinary switchboard relay. An ordinary Weston portable voltmeter connected to one of the secondary coils gives voltage readings almost exactly proportional to the current in the main high tension coils 94,

i. e., the graphic relation between the high tension current and the voltage on the instrumentv is almost a straight line starting from zero and inclined upward. A voltmeter having a scale calibrated and marked in amperes therefore gives an accurate reading of the high tension current. The voltage induced in coils 95 and 96 lags exactly behind the high tension current; this fixed phase relation makes this voltage suitable for use in all instruments heretofore operated by current from a current-transformer, it being necessary to replace the current coil in the instrument by a potential coil. 'The 90 phase relation above mentioned is advantageous in connection with directional relays for opening circuit breakers when the main line current reverses on a short circuit. Short circuit currents lag almost 90 behind the line-to-neutral voltage, and thel induced voltage in coils and 96 (being 90 behind the line current) is almost behind the line-to-neutral voltage, which by simply reversing the instrument wiring, brings the two voltages in the relay almost in phase, thereby giving aA maximum torque for definitely controlling the directional contacts of the relay.

Coils 95 and 96 are placed in theinclined positions shown for the purpose of enclosing va portion of the leakage flux which would not otherwise pass through them.

The two coils 91 are for the purpose of opposingA a portion of the leakage fiux thereby increasing somewhat the useful portion of the flux. Each of the coils 91 is short-circuited on itself and the only current in it is that induced by the leakage ux which it opposes.

In applying the current-potential transformer 2 to the higher voltage type of circuit breaker shown in Figs. 5, 6 and 7, it is preferable to place coils 95 and 96 around insulator stacks Vwhich are close together at the lower end and inclined apart at their upper ends, thereby enclosing a maximum magnetic flux.

Transformer steel laminations 96 may be secured to steel channel 9| and steel plate 92 to increase the total magnetic flux.

The transformer just described is advantageous in the higher commercial voltages (132 kv. and upward) in that its cost is very much less than discharge ends of the arc chutes open and an arcing member in each chute shiftable by gas blast to break the circuit, and means to direct a blast of gas into the arc chutes of all of said units to shift the arcing members to circuitbreaking position.

8. A gas blast circuit breaker comprising a plurality of similar, interchangeable units directly superimposed in vertical succession and separably connected and each comprising a body of insulation having therein a horizontal arc chute and a vertical bore in lateral gas delivery communication with one end of the Mchute and a diffusion chamber in receiving communication with the opposite' end of the chute and an arcing member in each chute shiftable by gas blast to break the circuit, said bores of the different units being in vertical register to form a conduit for delivery of a gas blast to the arc chutes of all of the units to shift the arcing members to break the circuit.

9. A gas blast circuit breaker comprising a plurality of similar interchangeable units directly superimposed in vertical succession and separably connected and each comprising a body of insulation having therein a horizontal arc chute and an arcing member in the chute shiftable by gas blast for circuit breaking, and means to direct a gas blast into the chutes of all oi the units to shift said arcing members for circuit breaking.

10. A .circuit breaking apparatus comprising a current interrupter and a disconnecting switch connected in series in a circuit, characterized in that said disconnecting switch comprises a stationary insulator stack bearing one of the switch contacts, a movable insulator stack bearing a switch element for engagement with said contact, a supporting arm for said movable insulator stack pivotally mounted at one end to swing about a vertical axis and bearing the movable stack at its c opposite end in close proximity to said Contact on the stationary stack when the switch is closed, the length of said supporting arm being several times the length of said switch element borne by the movable stack and the arm being adapted to swing about its axis more than -ninety degrees for wide separation oi said switch element from said contact when the switch is opened, and a iiexible electrical connection between said shiftable switch element and the interrupter.

HUMPHREYS MlLLIKEN.

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