USRE22872E - Apparatus for protecting power - Google Patents

Description

ApriLZQ, 1947.

G. A. MATTHEWS APPARATUS FOR PROTECTING'POWER LINES Original Filed May 7, 1940 4 Sheets-Sheet l dw/md 5003000 maomawomamwm Ampere:

- gfl Main/ eek; #04! m? April 29, 1947. G. A. MATTHEWS R. 22,872

- APPARATUS FOR PROTECTING POWER LINE-S Original Filed May 7, 1940 4 Sheets-Sheet 2 0 F g.4. l6

' n if ft :2 43 o 6/ 57/ 77km Delay 7Z5; 9 1; Man-60min:

2/ 0i/Lere/ April 29, 1947. G. A. MATTHEWS 7 I APPARATUS FORPROTECTING POWER LINES I 4 Sheets-Sheet 5 Original Filed May 7, 1940 M Apfil 29, 1947.

G. A. WTTHEWS APPARATU? FOR PROTECTING POWER LINES 4 Sheets-Sheet 4 Original Filed May 7, 1940 r &

Reissued Apr. 29, 1947 7 George A. Matthews, Detroit, Mich, assignor to The Detroit Edison Company, Detroit, Mich, a corporation of New York Original No. 2,352,556, dated June 27, 1944, Serial 333,875, May "I,

1940. Application for reissue August 20, 1945, Serial N0. 611,617

Claims. 1

This invention relates to apparatus for protecting electrical power lines against damage from short circuits and/or arcing faults between the line conductors. The invention is not limited to but is particularly useful in connection with, overhead feeder circuits of the insulated con ductor type. I 1

Studies of the records of interruptions to overhead circuits show that over 85% resulted from purely transient faults due to such causes as lightning flashover, line conductors momentarily swinging together, and small conductors or other foreign objects falling across the wires; and only a small percentage of circuit interruptions are due to permanent faults. Unfortunately, how ever, the power are that starts from a transient fault under the present systems of feeder circuit protection frequently results in a burn off of the line conductor, or at least in damage that so weakens the conductor as to give rise to mechanical breakage by wind, sleet or snow loadings.

The equipment generally employed by practically all utility companies for the protection of feeder circuits includes time-delay overcurrent relays for tripping the station breaker, and reclosing equipment for obtaining one or more timed reclosures up to a lockout in the case of a permanent fault. The tripping of the station circuit breaker has been purposely delayed to provide a, time differential between the operation of a protective device, such as the fuse at a distribution transformer or an overload breaker on a customer's premises, as it has been the generally accepted plan to avoid an opening of the main feeder circuit by faults which, in theory, could be removed by local protective devices. The operating characteristics of such equipment, in the typical case of a city circuit with a relay set to trip at 500 amperes, have been a delay of several seconds at overloads of from 500 to 750 amperes, with a progressive decrease in the tripping time to about 30 cycles, on a 60 cycles per second alternating current distribution circuit, at 2000 amperes. The delay in tripping remains approximately constant at higher fault currents, and the total circuit clearingtime for fault currents of 2000 amperes or over has been about 41 cycles, i. e., the relay tripping time plus about 11 cycles for opening the breaker contacts and extinguishing the are drawn between them. The equipment on rural circuits has been, in general, adjusted for a longer delay than that for city feeder circuits.

satisfactory several years ago, but the conditions ,for which it was designed have altered materially as increasing loads have resulted in the use of substation transformers of larger size and higher short circuit current capacity, and the bare concluctors originally installed on suburban and rural lines have been replaced by insulated or weatherproofed copperwire to meet local ordinances. An increase in the short circuit current in a fault obviously increases the rate at which an arcing fault damages the conductors and, for any given fault current, insulated conductors are badly burned or melted off beforethe-station breaker opens as the insulation holds an arcing fault at the total clearing time from 10 cycles to 5 cycles.

the location where it was initiated. With bare wires, the arc traveled freely along the line until it was blown out or reached insulators where it was usually stopped. Damage to the tie wires or to the insulators might then occur but, in general, there is less likelihood of damage to bare wires than to insulated wires in the case of transient faults,

Heavier short circuit currents and insulated conductors have thus created such conditions that even a transient fault generally results in a burn off of the conductors of the affected branch feeder circuit and frequently results in a. loss of service on the entire. main feeder circuits. It has been proposed to set the relays for instantaneous tripping of the station breakers, and to design the breakers for more rapid operation. Faster operation is obviously essential if burn off of the insulated conductors is to be avoided but the switchgear now commercially available cannot open a faulty 60 cycles line in less than about 10 cycles, and the best performance claimed for any experimental equipment has been 5 cycles between the initiation of the fault and the opening of the line.

I have made a systematic study of the burn of! characteristics of the weatherproofed copper wire now in general use, i. e., in sizes from No. 6 solid up to No. 4/0 stranded, and have found that it is not possible to effect a substantial decrease in circuit outage from transient faults by reducing The fact is that the short circuit current flow in an arcing fault between the insulated conductors of existing overhead distribution circuits is of such magnitude, with respect to the wire size, that serious damage or a complete burn of! results if the arcing faultcontinues beyond from /2 to 2 cycles on a 60 cycles line.

The design difliculties encountered in reduc- Protective equipment of this type wasgenerally ing the clearing time of prior circuit breakers from 11 cycles to 8 cycles indicate that there is but littlev possibility of decreasing the operating time to less than about cycles with the prior protective methods and circuit arrangements. The problem of constructing switchgear for the removal of an arcing fault from a high voltage line in from /2 cycle to2 cycles can be solved however by placing on the feeder circuit an additional element which functions to reduce the line voltage at the fault to zero or substantially zero in from /2 to 2 cycles, depending upon the magnitude of the fault current, after the initiation of the fault. An interruption of current flow the fault within from to 2 cycles will be referred to hereinafter as an instantaneous removal" of the fault current, and this term is to be distinguished from the term instantaneous tripping, which signifies nothing more than the adjustment of the tripping relay to energize the circuit breaker Vopening coil in as short a time as is possible. The new element for use with existing switchgear or with the faster switchgear contemplated by this invention will be termed a "line shorting contactor or shorting contactor as its function is to short circuit the lines afiected by a fault, therebyestablishing a low resistance short circuit that develops the full short circuit current capacity of the transformer feedingthe distribution circuit. This heavy flow of current simplifies the circuit breaker design by insuring adequate power for the rapid operation of the breaker even in the case of a fault at a remote point on a longline.- The instantaneous suppression of the initial fault current substantially eliminates burn off from transient faults but does not solve the problems of protecting the overhead lines and associated station equipment, and of maintaining service 'on'other portions of the feeder circuit inthe case of a permanent fault on a branch line. The line shorting contactor supplements, but does not replace, other equipment such as circuit breakers, or other tim- 1 ing devices that reclose the circuit a plurality of times and for periods of upward of 30 cycles in attempts to burn off the fault or the faulty branch circuit in the case of a permanent fault. V

Objects of the invention are to provide novel apparatus for the instantaneous removal of arc ing faults from power distribution lines. Further objects are to provide apparatus for the instantaneous removal of the line voltage at a'faulty section by first short circuiting and then .opening the line, and for the subsequent reclosure v of the line for relatively long periods and at timed intervals, up to a lockout in the case of a pertional switch mechanism for successively energiz ing the line to send current through the fault if it remains on the line, and for opening the line permanently in the case of a permanent fault.

These and other objects and advantages of the peres.

must be about 4500 ing times of certain apparatus of this invention:

Fig. 2 is a fragmentary elevation of insulated conductors of different sizes showing limited damage caused by arcing faults that are suppressed in less than /30 second;

Fig. 3 is a fragmentary circuitdiagram of an electrical distribution system including protective equipment embodying the present invention;

Fig. 4 is a central section through a line shorting contactor;

Fig. 4c is a schematicdiagram of the same;

Y Figs. 5, 6 and 7 are sectional views of the coilshunting switch and time-controlled latching mechanism of the line shorting contactor;

Fig. 8 is a central section of a circuit breaker having the rapid operating characteristic of curve B of Fig. 1;

Fig. 8a is a schematic diagram of the same; and

Fig, 9 is an enlarged fragmentary view of the breaker contacts.

The novel features of the invention may be best understood by first considering curves No. 6" to No. 1/0 of Fig. 1, that show the time, in cycles on a cycles basis, in which arcing fault currents of different magnitudes burn off weatherproofed copper wires of the sizes indicated by the legends identifying the curves. The conductors were tested under conditions of horizontal spacing and tension that simulated service conditions on a' 5000 volt feeder circuit, and the arcs were initiated by drawing a No. 40 copper wire across bated sections of the conductors. The time values were obtained from an oscillograph and represent the actual parting of the conductors, i. e., they do not include the time of arcin'gbetween the conductors as they fell away after parting.

The smallest size, No. 6 W. P. copper wire, is used on many long branch feeder circuits where the normal load may be up to about 20 amperes and the substation transformers have a short circuit current output of upward of 1500 am- Curve No.- 6 shows that this small conductor will burn off in 2 cycles or & second under about 1700 amperes, while curve No. 4 shows that the arcing fault current amperes to bum'oif a No. 4 insulated copper wire in 2 cycles, and curve No. 2 shows that wire of this size will be burned oil in 3 cycles by an arcing fault of 5500 amperes, or in '7 cycles by an arcing fault of 1500 amperes.

Thesignificance o1 thisfamily of curves is that arcing faults ofthe magnitudes encountered on various feeder circuitsof different wire sizes will 55 manent fault; Objects are to provide line .protecting switching equipment of high current caburn oil the conductors in the 8 or 10 cycle in tervalbetween the faultinitiation and the opening of the fastest switching gear of the present commercial installations. -Furthermore, a reduction of the breaker opening .time'tc 5cycle's' will i not efl'ect an appreciable reductionin the burn invention will be apparent from'the following specification when taken with the accompanying drawings in which:

Fig. 1 is a curve sheet showing the relation between the'magnitudeof a fault current and, respectively, the time required to burn oil. insulated conductors of different sizes and the operat-' oil or damage from arcing faults, and the present experimental attempts to obtain 5cy'cle operation of a circuit breaker therefore will not eliminate the burn on of .insulated fconductor's by arcing flashoversdue to purely transient faults Some damage resultsfroman'y arcing faul but the factor or. safety normally provided in- 0 good circuit design permits some reduction in the cross-section of the conductor without introducing a serious hazard of mechanical weah ess. Tests on many arc-burnedcopper wires of several sizes indicate that, in general,'the damage is not likelyto result in breakage of wire by high wind or sleet loadings when the burn reduces the original cross-section by not more than about 25%. The limited damage resulting from arcing the main feeder circuit.

' aas'ra' cordance with this invention, is indicated by Fig. 2 in which insulated copper wires of sizes No. 2, No. 4 and No. '6 are identified by reference numerals 2, 4 and I5, respectively. The line voltage was 5000 volts and the arcing fault current was 1500 amperes in the series of tests in which the specimens of Fig. 2 were obtained. The areing fault on the smallest wire 6 was removed in V2 cycle, and the arcing faults on wires 2 and 4 were removed in 2 cycles. The illustrated arc burns b of the several conductors are typical of the results obtained during a systemmatic study of arcing damage to line conductors, and mechanical tests of similar specimens showed that burns of this order do not reduce the tensile strength of the wires below safe working values.

Reverting to Fig. l,'the curves A, A show the relation between fault current and the operating time of line shorting contactors, to be described later, of normal current ratings of 100 and 200 amperes, respectively, and curve B shows the opening time of a novel circuit breaker contemplated by this invention. Overload currents of the order of 1500 and 2500 amperes will actuate the line shorting contactor to closed position, thereby collapsing the line voltage at the fault to zero, within substantially /2 cycle after the fault initiation. Curve B shows that the new circuit breaker will open in 2 cycles at anyfault current above about I amperes. These operating speeds are substantially higher than any previously attained on feeder circuits with switch gear that is electrically and mechanically stable, and these high operating speeds for the instantaneous suppression of the fault current, by collapsing the line voltage and/or opening the line, eliminate the burn off of line conductors by transient faults.

A typical embodiment of the invention is shown in the Fig. 3 circuit diagram of a substation and 5000 volt, 60 cycles feeder circuit working out of a high voltage line X, Y, Z. The transformer T and regulator R are or may be of conventional design. Reclosing circuit breakers CB are placed on the several main feeder conductors at, 11, 2,, at the substation and may be of conventional design but preferably, as shown, are of a new instantaneously operating design and consist in fully automatic single pole circuit breakers that are self-contained and self-actuated. A line shorting contactor SC is also placed on each conductor of the main feeder circuit, preferably at some distance from the substation to cushion the shock ,to be placed upon the station equipment by the metallic short circuit that is placed upon the line when the shorting contactors are 'tripped' substation where the load has been reduced by various branch circuits B that are connected to The branch circuits may be of No. 6 copper wire, either bare or insulated depending upon local ordinances, and each branch is preferably protected by fuses F.

'In the case of an important feeder branch 3',

the branch is preferably protected by repeater fuses RF.

The physical structure of a line shorting contactor SC is shown in Fig. 4, and the elements and circuit connections are shown schematically in Fig. 411. Each shorting contactor is a fully automatic, self-contained unit housed within a chamber comprising a hollow insulator II with upper and lower metal sleeves ll, I2, and top and bottom closures l3, [4 that are bolted to the sleeves II, l2, respectively. The central portion of the insulator III is grooved or otherwise shaped to receive a supporting bracket l5 by which the shorting contactor is mounted on a pole or framework within a substation. A source or line terminal I3 enters the upper shell I l through an insulating bushing l1, and a load terminal I8 extends through and is welded or otherwise me chanically and electrically connected to the shell II. The operating coil IQ of the contactor is connected between theterminals I6, l8 by straps 20, 2|, respectively, the coil l3 comprising a single or multiple layer solenoid wound from a flat copper bar. The coil I9 is mounted within a laminated core 23 that is secured between a pair of supporting plates 24 by bolts 25, and the plates 24 are secured to and grounded on the upper metallic shell II by brackets 26. Thecentral section 21 of the laminated core rests upon a rubber cushioning member 23 to serve as a stop for the plunger, the cushioning member being carried by a plate 29 that is rigidly secured to the supporting plates 24. The armature or plunger 30 comprises laminations riveted to ribs 30' that are welded to the switch rod 3i and project above the laminations to carry a part of the control mechanism. The conical contact 32 on the switch rod 3| is axially alined with a conically recessed contact assembly comprising a plurality of wedge-shaped segments 33 on leaf springs 34. The lower ends of the springs 34 are secured to a cylinder 35 on a plate 36 that is supported from the plate 29 by a plurality of insulating rods 31. A pressure contact member 38 is connected to plate 36 by jumpers 39 and pressed into engagement with the lower closure I4 by a spring 40. A terminal lug 41 projects below the closure II for connection to similar lugs of the shorting contactors of other phases or to the conductor of a two-wire branch other than that to which source and load terminals l6, l8 are connected.

The hollow insulator is filled with oil to a level above the core 23, and a low resistance connection from the load terminal l8 to the moving contact 32 is obtained through jumpers 32' that extend from contact 32 to the \plate 23.

The upper end of the rod 3| extends through a strap 42 that is fixed to the supporting plates 24, and a. spring 43 is coiled about the rod 3| to hold the rod in elevated position against the closing force developedlby coil l9 at current flow less than a predetermined amount, for example 50%, above rated current that the contactor can carry for long periods.

The source or line terminal I6 is connected to the stationary contact 44 of a coil-shorting switch by the strap 20 and a jumper 45. The movable switch contact 44' is carried by an arm 46 pivoted upon the supporting plates 24 and normally retained in open-circuit position by a spring 41 that is anchored to plate 24 byasbolt adjustable along slot 41'. The arm 46 is grounded on the load terminal l8 through the supporting plates and preferably is connected to the plate 24 or to lead 2| by a jumper", see Fig; 4a. A closure of switch contacts 44, 44 will short circuit the operating coil l9 and thus prevent operation of the shorting contactor. Time-delay mechanism, indicated. generally by the block 49, is provided for retaining the switch 44, 44 in 7 closed position for a predetermined interval following a closure of the switch. I

The control mechanism for the shorting contactor is located between the upper ends of the supporting plates 24 and comprises a mechanical linkage having parts mounted on the plates 24 and other parts pivoted to the central ribs 30' of the laminated core. The control mechanism is illustrated in Figs. -7 as viewed from a plane through the axis of the rod 3|, except that the timing mechanism is shown in elevation at the right of Fig. 5 and in Figs. 6 and '7.

The movable contact arm 46 comprises a pair of duplicate members mounted on plates 24 by a pivot pin 5| and joined at their outer ends by a strap 46 which carries the contact 44'. A link 52, also pivoted on pin 5|, is coupled to the contact arm 46 through a hairpin spring 53 that urges the contact arm 48 clockwise when link 52 is rotated clockwise by a plunger. A pivot pin '54 connects the other end of link 52 to a latch member 55 and extends through an elongated slot in a link 56 that is pivoted to the core plate 30'. The upper end of the latch member is cut back for locking engagement with a roller 51 on the pivot pin of a lever 58, the latch member being pressed toward the roller 51 and a latchreleasing pin 59 on lever 58 by a spring 69. The forked outer end of lever 58 receives apin 5| on a timing lever 62 carrying a pawl 63 that bears on ratchet wheel 54 on the shaft of an escapement mechanism of conventional type, indicated by the block 49. Pawl 63 drives the ratchet wheel clockwise when lever 62 is rocked in that direction by a spring 65, and rides idly over the-ratchet wheel when the lever is moved counterclockwise by a link 65 having an elongated slot receiving a pin 61 on the core plate 30. The core plate 30 has an inclined slot, defined by'a notch in the plate and a projection 68, for receiving a roller 69 on a hold-off" link that is pivoted to the supporting plates 24 and urged clockwise towards a stop pin III by a spring 12.

The control mechanism operates in the following manner. The arm 46 is normally held in raised position by the spring 41, and the roller 59 of link 10 is seated in the inclined slot of the core plate 3ll', as shown in Fig. 5. A predetermined current flow through coil l9 overcomes the spring 43 and moves the core 30 and rod 3i downwardly to close the shorting contactor, and the several parts'then have the positions shown in Fig. 6. Link 56 moves the latch member 55 down into locking engagement with the roller 51, and rocks the link 52 clockwise to stress the spring 53 that urges the contact arm 46 towards closed position. The drop of the plunger released the roller 69 of link Ill from the slot in the core plate 30, and thereby forced link III, in conjunction with the spring 12, clockwise to the stop I I. This brought the upper end of link 10 into the path of the bar 46' of the contact arm 46 and thus prevented a closure of the coil-shunting, contacts 44, 44'. Link 66 moved the timing lever 62 counterclockwise and thereby stressed the spring 65 that is to restore the timing lever to normal position with a time-delay that is controlled by the escapement mechanism 49. The latch-release pin 59 is now spaced from the latch member 55.

Upon the first opening of the circuit breakers CB, the rod 3| is lifted by the spring 43 and the parts assume the positions shown in Fig. 7. Link 52 cannot move up as it is locked by the engagement of latch member 55 with the roller 51, and

the stress in the spring 53 tends to move the contact arm 46 clockwise to close contacts 44, 44'. This closing motion takes place as soon as the core assembly moves upwardly to force the roller 69 of link Ill into the inclined slot by the projection 68. The elongated slot in links 86 permits the core assembly to lift, but the counterclockwise movement of the timing lever 58 is retarded by the escapement mechanism 49 since the timing lever is locked to the escapement mechanism by the pawl 53 and ratchet wheel 54. The time-delayed return movement of the lever 58 displaces the pin 59 into engagement with the latch member 55 to force it out of locking engagement with the roller 51. When released from roller 51, the latch member 55 is moved upwardly by the spring 53 thus releasing the stress in that spring and thereby permitting the spring 41 to rock the arm 46 counterclockwise to open contacts 44, 44'. The equipment is thus reset to the condition shown in Fig. 5 after a time-delay determined by the escapernent mechanism 49. The time-delay is suflicient, as stated above, to permit the reclosing circuit breaker CB to operate through a predetermined time-delay to a lookout in the case of a permanent fault on the line.

It is to be noted that, upon the initial removal of current by the circuit breaker, the shorting contactor is locked out electrically by the switch 44, 44' that shunts the coil I9, and mechanically by roller '69 and its supporting link Hi that is blocked against clockwise movement by the strap of the closed contact arm 46.

The tripping current of the shorting contactor is determined by the number of turns of the coil l9, and the forces exerted by springs 43, 41, 53 and 65. The lockout period is determined, for

\ any given escapement mechanism, by the force developed by the spring 65 and by the gear train in the escapement mechanism. A control of the operating characteristics is readily attained by adjusting the compression of spring 43 by the downward or upward movement of the locknuts on the end of the rod 3!. The spring 43 opens the shorting contactor in about 5 cycles after the circuit breakers open, but the exact opening time is not important since the first reclosure of the circuit breaker is delayed for from 30 to 60 cycles as a protection against multiple lightning strokes. The shortingcontactor must open under no-load, however, as the simple design which facilitates an instantaneous closure makes 1 no provision for extinguishing an are between the main contacts. a

The operating speeds indicated by curves A, A of Fig. 1 have been obtained in mechanically stable equipment such as shown in Fig. 4, and trial installations have fully demonstrated that insulated conductors can be protected from burn off from transient faults when the line voltage is removed from the fault in /2 cycle. The line shorting contactors do not, and are not intended to, protect the conductors against burn off in the case of a permanent or relatively permanent fault. The maximum service is maintained and the location of a permanent fault is most readily ascertained, when the faulty branch circuit is isolated by sectionalizing fuses or is burned oil during the sequence of operations of a reclosing circuit breaker prior to a final lockout.

The shorting contactors may be used with any station breakers of the reclosing type but the maximum protection is obtained when the circuit breakers CB are of the type shown diagramfaults between the substation and the shorting contactors which, as stated above, are preferably located some distance from the station to reduce the shock to station equipment by the dead short circuit produced by the shorting contactors. Furthermore, the new circuit breakers afiord substantial protection against burn ofi during the lookout time of the shorting contactors after a closure arising from a transient fault. The shorting contactors may be out of action for about, 3 minutes in such cases since service is restored at the first reclosure of the circuit breaker. Lightning strokes during this interval will usually result in a burn ofi when the circuit breakers are of prior types and open in from 10 to 40 cycles,

but this damage is prevented when the new circuit breakers are used with the line shorting contactors.

full automatic operation. As shown in Fig. 3a,

the circuit breaker includes a tripping coil 89'and operating coil 8| in series between terminals 82, 83, the operating coil 8| being normally shunted by the switch 84 that is opened by the tripping coil 99 against a spring 84'. This switch and the main breaker switch are of the reciprocating rod type, as described and claimed in my prior Patent No. 2,167,665, granted August 1, 1939, "Circuit breaker," in which an annular arc-extinguishing chamber is formed by horn fiber or other organic material which gives off de-ionizing gases when vaporized by the arc.

The core or plunger 85 of coil 8| is secured to a metal rod 86 which carries the movable contact 81 of the circuit breaker and terminates in a rod 88 of horn fiber or the like. The stationary breaker contacts include a main contact 89 that is normally engaged by the rod 86 or its movable contact 81, and an arcing contact 99 above and spaced from the main contacts. The arcing contact 99 is connected to the main contact 89 through a spiral coil 9| coaxial with the rod 86 and the contacts. The function of coil 9| is to rotate the arc that is drawn between the moving contact 81 and the arcing contact 99 when the breaker opens, and the coil is wound in the sense oppositethat of the operating coil 8|. The shunt or tripping switch 84 is of simpler design as the are drawn across its contacts can be extinguished without the aid of an arc-spinning coil.

Timing mechanism 92 is provided to delay the second and subsequent openings of the breaker,

but the firstlopening takes place with no delay.

The timing mechanism is indicated generally by the block diagram overlyin the junction of the operating lever 93 ofswitch 84 and the link 94 that connects lever 93 to the armature 95 of the trip coil 89. Any desired type of mechanism may be employed to delay the opening of the shunt switch 84 for intervals of 69 cycles or upward when the fault is still on the line at thefirst or subsequent closures of the breaker. The detailed construction is not illustrated since it forms no part of the present invention.

The breaker is housed within a chamber comprising a hollow insulator 98 and end closures 91, 88 of metal that carry terminals 82, 83, respectively. The insulator is provided with metal fiber plates or disks I94,

sleeves 99 to which the closures are bolted. and is recessed to receive a mounting bracket I99. A plate I9I extends across the-upper end of the insulator 96 and constitutes the support for the trip mechanism and the breaker assembly, and the control mechanism is located in the domed closure 91 above the plate I9I. The insulator 9B is preferably filled with oil to approximately the lower face of the plate I9I that supports all 01' the switch and control mechanism.

The framework of the breaker assembly includes a series of rods I92, 2. metal plate I93 on which the coil BI rests, and a plurality of horn Insulating rods I95 are threaded upon rods I92 to secure the plate I93 against spacing sleeves I95 on rods I92, and rods I92 are threaded upon the rods I95 to carry the disks I94. A dashpot for arresting the opening movement of the breaker is formed by the enlarged lower end of the'core 85 and a-cylinder I98 that is'mounted between the plate I93 and the upper disk I94. The top portion of the cylinder flares inwardly above vent openings that permit a free escape of oil from within the cylinder during the major part of the opening movement of the rod 86.

The two intermediate plates I94 are separated slightly and are recessed to receive small horn fiber disks I94 that form the outer wall of the arc-suppressing chamber. The small plates may bereplaced when the diameter of the chamber has been appreciably increased by the vaporization of the horn fiber. The arc-spinning coil 9! is mounted between the two lower disks I94, and connected between arcing contact 99 that is recessed into the lower face of the upper disk of this pair' and a flanged brass tube I98 that is bolted to the bottom disk I94 to support the main contact assembly. The main contact 89 includes a plurality of arcuate segments secured to the upper ends of the several sections of a longitudinally slotted tube I99 of resilient metal. The flanged lower end II9 of the tube I99 is electrically connected to a disk I I I by a jumper I I2, and the disk I I I is pressed against a boss on the lower closure 98 by springs I I3 coiled about guide rods that extend through the flange I I 9.

The breaker opens against a spring H4, and displaces a rachet bar II5 into engagement with the wheel II6 of an escapement mechanism. The spring II4 tends to reclose the breaker as soon as the circuit opens but the downward motion of the switch rod 86 is delayed by the escapement mechanism. The escapement may be of known types, including means for locking the breaker in open position after a. predetermined number of reclosures if the fault is still on the line and means for resetting from any point in the schedule of reclosures when the breaker closes on a sound line. The time-delay may be of the customary order of from 30 to 60 cycles, but the specific design of the escapement mechanism is not an essential feature of this invention.

It is to be noted that theline current flows through the series operating coil 8| only when the shunting switch 84 is opened by the coil 89. The tripping current is determined by the coil 89 and the reclosing spring 84' of the shunting switch 84. The tripping value may be adjusted as desired but will usually be set up to 200% or more of the rated current capacity of the breaker. Heat developed in the coil 89 by continued overloads short of the tripping value does not cause serious heating and coil destruction, as has been the case with some prior breakers with series operating coils, since the coil 80 opens only the shunting switch 84 and not the breaker contacts.

It is therefore possible to design the operating coil II to develop sufllcient force for an exceedingly high speed opening of the breaker since only a momentary current surge flows in the operating coil. The reciprocating rod and de-ionizing chambervconstruction also contribute to high speed operations as a 1 to 2 inch movement of the rod, which is sufficient to separate the contacts and suppress the arc, is obtained in about 2 to 3 cycles with operating coils ll of practical design. The initial opening of the breaker is effected in from 2 to 3 cycles in accordance with the magnitude of the fault current, as shown graphically by curve B, Fig. l,

but the subsequent openings are delayed by the timing mechanism 92 to supply current to a persistent fault for periods of 30 cycles and upward, thereby to blow sectionalizing fuses if the fault cannot be burned off. This results in the isolation of the faulty branch but service is maintained on the remainder of the feeder system.

The method of operation of the protective equipment is as follows. The circuit breakers are adjusted to trip at a selected overload value, which may be, as in present practice, about 200% of the rated current capacity of the breaker, and the line shorting contactors are set to trip at a lesser overload. Any fault that results in the predetermined overload at the line shorting contactors thus trips the contactors to place a metallic short circuit across the affected conductors in $6 cycle after the fault initiation.

This instantaneous suppression of the fault current prevents the blowing of fuses and the burn oil of insulated conductors at the fault. In the case of bare wires, the instantaneous suppression of the fault current eliminates damage to the supportingstructure when a traveling arc starts close to and would reach the supporting structure before it is blown out. The circuit breakers are tripped either by the initial fault current or by the heavy current flow through the closed contactors SC, and reclose after a delay or from 30 to 60 cycles which permits de-ionization of the gases in the region of the arc path. The shorting contactors open with the interruption of current flow by the circuit breakers, and are locked out for a predetermined time during which the circuit breakers go through a series of timedelay trip operations to lockout in the case of permanent faults.

- The sequence of operations varies with the nature of the fault I on a feeder circuit B. If the fault was due to a transient cause, such as lightning or a small wire dropped across the line, the circuit breakers stay in on the first reclosure. If the fault is'still on the line, the heavy current flow tends to burn oil" the fault I and to blow the fuses F. The feeder circuit itself may burn off before or simultaneously with the burning of the foreign object that is across the line. If the line is not cleared by one of these methods, the fuses blow to remove the faulty section from the feeder system before the circuit breakers complete a full sequence of reclosures to a lookout, and service is thereby restored to the remainder of the feeder circuit. The instantaneous closure of the shorting contactors protect the fuses against damage before the first opening of the circuit breakers, and thereby affords greater latitude in the selection of the time-response characteristics of sectionalizing fuses. The fuses will usually blow durl2 ing the first reclosure of the circuit breakers in the case of a permanent'fault.

Protection against bum oil is obtained whether the circuit breakers are of the described construction or of prior designs that require at least 8 cycles to open. The Fig. 8 circuit breakers afford greater protection against an outage of a part or all of the feeder since they open in about 2 cycles.

' The existing substation equipment may be such that the line shorting contactors should be located a mile or more from the station to reduce the shock placed on the station equipment by the metallic short circuit. The impedance gradient of the line to the short circuit point reduces the current drawn by ashort circuited line, and the maximum short circuit current at a given substation can therefore be controlled to some extent by locating the shorting contactors some distance from the station. The preferred spacing will de-.

pend upon such factors as the capacity of th station equipment and of the line feeding it, the standards of operation established by the public utility company, and the type of service fed by the protected circuits. The shorting contactors can be located at the substation in some cases but at other stations the preferred location may be from one mile up to two or three miles from the station. This means that a portion of the feeder is not protected by the shorting contactors, but the reclosure is on a clear line.- Another lightning stroke during the lookout period of the shorting contactors will usually result in a burn off when the breakers are of the prior designs but the high opening speed of the new breakers will usually protect even the smaller insulated a burn on. v

The new-circuit breakers maybe used without 1 the shorting contactors but the full advantages of the invention are attained when a feeder circuit is protected jointly by the new circuit breakers and the line shorting contactors.

It is to be understood that adequate protection against burn off from transient faults may be had on some feeders when the fault current continues for more than from to ,2 cycles, but equipment with this high operating speed is readily manufactured and there is no advantage to be gained by designing the equipment for a longer operating time. D

Time values are stated in cycles on a 60 cycles per second basis since it is the usual practice in this art to measure the operating times of protective switchgear with oscillographs that generate a "timing wave" of the frequency of the electrical distribution system. The novel equipment of this invention was tested and has been used on lines supplied with alternating current of a frequency of 60 cycles per second but the protective methods and apparatus may be used on direct current lines or alternating current lines energized at 25 cycles per second or at other frequencies. I

Claims specific to the line shorting contactor and to the reclosing circuit breaker herein illustrated and described have been presented in divisional applications Serial No. 438,823, filed April wires against 13, 1942, on which Patent No. 2,334,571 issued November 16, 1943, and Serial No. 439,576, filed April 18, 1942, respectively.

The circuit arrangement or combination of protective devices herein shown and .described is illustrative of the invention, and various changes that may occur to those familiar with the art fall within the spirit of my invention as set forth in the following claims.

I claim:

1. In an electrical distribution system, the combination with a current source, conductors extending from said current source to form a distribution circuit, reclosing circuit-interrupting means responsive to a fault on said circuit to effect the first opening thereof after a time delay during which arcing conduction resulting from a fault will damage the conductors, said circuit-interrupting means including control mechanism for opening and reclosing the circuit a plurality of times to a final lockout in the event of a permanent fault, of means to protect said conductors against damage from transient faults; said protecting means comprising a normally open switch across said conductors, spring means biasing said switch to open position, means responsive to a fault current to close said switch prior to the first opening of said distribution circuit by said circuit-interrupting means, thereby to establish a metallic short-circuit across said conductors and remove the voltage from the fault point, said spring means opening said switch to remove said metallic short-circuit upon opening of said distribution circuit by said circuit-interrupting means, said control mechanism including means to delay the first reclosure of said circuit-interrupting means until said switch is opened to remove said metallic short-circult, and timing means to lock said switch against reclosure during the time period required for operation of said reclosing circuit-interrupting means \to a final open position in the event of a permanentfault.

2. In an electrical distribution system, the combination with reclosing protective apparatus for opening the system after a time delay of from l/30 second to about 1 second after fault initiation and to reclose the system a plurality of times to a lockout in the event of a permanent fault; of

time-delay means energized upon the opening of slid switch by said spring means to prevent a reclosure of said switch within the time interval required for operation of said reclosing protective apparatus to a lockout in the event of a permanent fault,

3. In an electrical distribution system, a current source, conductors extending from said source, and branch circuits connected across said conductors through circuit interrupters including thermally responsive means for opening the same after a time delay interval in the event of faults on the respective feeder circuits, of protective means to preclude opening of said interrupters from transient faults; said protective means comprising a normally open shorting circuit connected across said conductors between said branch circuits and said current source, a line shorting contactor for closing said shorting cir-- cuit, and means responsive to fault current flow to actuate said shorting contactor to closed position within a time interval substantially shorter than the time delay interval within which said circuit interrupters may open, thereby. to collapse the voltage at the fault point to zero, and means for opening said shorting circuit after a predetermined time interval.

4. In an overhead power distribution system, a source of current, a pair of overhead conductors forming a circuit fed from said current source, means including a normally open switch operative to closed position by a fault current to shortcircuit said conductors, circuit interrupting means responsive to the fault current and the short-circuit current to open said circuit, means responsive to the opening of said circuit by said circuit-interrupting means to render said short- ,circuiting means inoperative for a predetermined period after the initial operation thereof, and control means operative within said predetermined period to reclose said circuit-interrupting means a plurality of times prior to a final opening thereof in the case of a permanent fault.

5. In an electrical distribution system, the conibination with a current source, conductors forming adistribution circuit fedfrom said source, and circuit-interrupting means responsive to overload current flow and including mechanism for opening and reclosing said circuit a plurality of times priorto a final opening thereof in the event of a permanent fault, of a shorting circuit across said conductors including a normally open shorting switch having contacts permanently connected to the respective conductors, means responsive to fault current flow to close said shorting switch prior to the initial opening of the distribution circuit by said circuit-interrupting means, means to open said shorting switch in the interval between the initial opening and the first reclosure of the distribution circuit by said circuit-interrupting means, and timing means to lock said shorting switch in open position for a period longer than the operating time or said circuit-interrupting means to a final cirsaid circuit and to reclose the same a plurality of times for intervals of the order of at least second, 'of means to protectsaid conductors from damage in the case of transient faults; said protecting means comprising means to shortcircuit; said conductors prior to the initial opening of the circuit -by said circuit-interrupting means, means operative upon the initial opening of the distribution circuitto remove the shortcircuit, and means to lock said short-circuiting means against operation for a predetermined period after the removal of the short-circuit, said predetermined period extending over a plurality of opening and reclosing operations of said cir. cuit-interrupting means.

7. In an electrical distribution system, the combination with an alternating current source, a feeder circuit connected to said current source, and circuit-interrupting means of the reclosing v 15 type on said feeder circuit, said means including mechanism responsive to excessive current flow to open and to reclose said circuit-interrupting I means a plurality of times, a line'shorting con-'- v 'tactor for short circuiting the feeder circuit; said line shorting contactor including means respon-p sive to excessive current flow to operate said cona close said second switch.

tactor to short circuit the feeder circuit prior to the initial opening of said circuit-interrupting means and within second after a fault inception, means to operate said contactor to remove the short-circuit upon the initial openins of said circuit-interrupting means, and timing means to lock said contactor in open circuit condition for a predetermined period following an operation thereof to open circuit condition.

8. In an electrical distribution 'system, the in-, vention as claimed in claim "I, wherein said clifcuit-interrupting means comprises a reclosing circuit breaker between said current source and said feeder circuit. 1

9. In an electrical distribution system, the in- 'vention as claimed in claim '1, wherein said cir-,

cuit-interrupting means comprises repeater fuses on said feeder circuit.

. 10. In an electrical distribution system, the combination with an alternating current source, an overhead feeder circuit including insulated conductors, a circuit breaker betweensaid current source and said feeder circuit, and means responsive to excess current flow to open and to reclose said circuit breaker a plurality of times, 1 of a normally open switch connected across said feeder circuit, means responsive to excess current arising from a fault to close said switch within one cycle after fault inception, means to open said switch upon the'initial opening of the feeder contactor upon the initial opening of said cir- I circuit by said circuit breaker, and means for retaining said switch inopen position for a period corresponding to a plurality of reclosures of said circuit breaker after the initial operation thereof.

11. The invention as claimed in claim 10, wherein said means for closing said switch in- Number '12. In an electrical distribution system, the combination with an alternating current source, a feeder circuit, a circuit breaker including means to open the same in response to a fault on the feeder circuit, and time-delay means for reclosing the circuit breaker, of a normally open line shorting contactor connected across the feeder circuit, means including a coil in series with said feeder circuit to close said contactor instantaneously upon fault inception, means to open said cuit breaker, locking means to retain said contactor open after a cycle of closing and opening thereof due to a fault on the feeder circuit, and time-delay means for rendering said locking means inoperative.

13. The invention as claimed in claim 12, wherein said locking means includes a switch .for shunting said coil.

14. The invention as claimed in claim 12, wherein aid locking means includes a mechanical latch for locking said contactorin open position.

15. The invention as claimed in claim 12, wherein said locking means includes a switch for shunting said coil and a mechanical latch for lo'cking said contactor in open position.

v .GEO. A. MATTHEWS.

naraaancas crran The following references are of record in the fileof this patent:

UNITED STATES PATENTS Name Date Nicholson Oct. 1'7, 1916

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