US2027221A - Direct trip device - Google Patents

Description

Jan. 7, 1936. M A BOSTWICK 2,027,221

DIRECT TRIP DEVICE Filed July 19, 1934 3 Sheets-Sheet 1 .Za @M Jan. 7, 1,936. M. A. Bos'rwlcK DIREG'I1 TRIP DEVICE 5 Sheets-Sheet 2 Filed July 19", 1934 P/a/Vea/ Sepa/wien INVENTOR /Vyrofz A. Eosfzaz'c/.

swf. ATT NEY Jal-1. 7, 1936. M A BOS-[WICK 2,027,221

DIRECT TRIP DEVICE Filed July 19, 1934 3 Sheets-Sheet 5 umm Ill

WITNESSEYS: INVENTOR ritmica .im 7, 193e UNITEDA rrxrEs'` PATENT OFFICE DIRECT 'nur DEVICE lMyron a'mtwick, Spokane, Wash., miglior to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 19, 1934, Serial No. 736,022

14 Claims.

y 5 particularlyA applicable to network protectors.

Various direct-trip devices having power-directional characteristics have heretofore been proposed, but, so far as I am aware, all such devices of the prior art have either had undesirable charlo acteristics, such as a circular tripping curve, or

have been unable to deliver a powerful mechanical tripping impulse unless built to an undesirably large scale.

It is'accordingly an object of my invention to l5 provide a novel direct-trip device which shall have substantially straight-line or other desirable tripping characteristics, and which shall operate to deliver a powerful mechanical tripping. impulse for'a given size or weight of the device.

20 Other objects oi' my invention will become evident from the following detailed description, taken in conjunction with the accompanying drawings, in which Figure 1 is an elevational view of a direct-trip 25 device embodying my invention.

Fig. 2 is a sectional view taken upon `the line II-H f Fig. 1. f Figs. 3 and 4 are elevational views of a detail of the device shown in Figs. 1 and 2. 30, Fig. 5 is a diagrammatic view of a magnetic circuit of myv improved direct trip device.

Figs. 6, 7 and 8 are vector diagrams illustrating the operation of my improved direct-trip device; and,

35. Figs. 9 and 10 are diagrammatic views of circuit breaker apparatus embodying my invention. In accordance with my invention, I utilize the principle of a pair of magnetic elements arranged to exert opposing forces upon a movable member, as disclosed in the United States patent to Edgar A. Hester, No. 1,948,711, issued Feb. 27, 1934, and assigned to the Westinghouse Electric 8: Manufacturing Company. As explained in the abovementioned patent, the mechanical tripping" energy delivered by such a device may be increased by causingvthe movable member to opcrate from a normally stable position through a mechanically unstable range to a tripping position; However, in accordance with my inven- 50 tion, a straight line tripping characteristic may be produced, whereas that ofthe Hester device is necessarily a circle. 1 f

Referring to Fig. l, the direct trip device of my invention comprises a movable member I ar- 55.' ranged to be acted upon by opposing forces produced by an actuating element 2 and a restraining element 3. In the preferred form of my invention, the movable member I is rotatably supported upon a shaft 4 in suchl a manner thatv the elements 2 and 3 normally exert opposing 5 moments or torques thereupon. It will be obvious, however, that there are numerous other mechanical arrangements suitable for obtaining the balance of forces involved in my invention, and that the invention may be practiced with such other arrangements.

The actuating element 2 comprises a stationary magnetic structure 5 consisting of a U-shaped. assembly of laminations arranged to form an open magnetic circuit, the laminati'ons being sew cured together by any suitable means such as bolts 5a. The magnetic 'structure 5 is fastened to a suitable base plate 6 of non-magnetic materal, by any suitable fastening means (not shown), in a position to partially surround a bus 20 bar 'I which carries the alternating-current to which the direct-trip device is to respond. The shaft I is mounted upon a pair of brackets 8, only one of which appears in Fig. l, seemed to the base plate 6 by means of machine screws .8a. 25 The ends of the shaft 4 are 'threaded to receive suitable fastening nuts la.

An armature 9 for the actuating element 2 is mounted in the air gap of the open magnetic structure 5, in such a manner as to close the 3@ magnetic circuit upon rotation of .the member I in the counter-clockwise direction.

The structure of the restraining element 3 is best shown 'in Fig. 2. Referring to Fig. 2, a laminated C-shaped pole-piece assembly I0 is se- 35 cured by means of suitable non-magnetic spacers Il to a U-shaped assembly of laminations I2 in such a manner as to provide air gaps at points and y. The U-Shaped laminations of the assembly I2 are preferably of the same size and 40 shape as those of the assembly 5, in order to provide` similar magnetic characteristics, for a purpose as will be hereinafter more fully explained.

The restraining element 3 is provided with an 45 armature I3, fastened to a metallic block Il (see Fig. 2) which constitutes part of the movable member l. In the preferred form' of my invention, the armature I3 is mounted upon a bolt I3a and is spaced from the block by means ofa compression spring I3b. A lock-nut I3c, threaded upon the bolt I3a, provides a means for adjusting the relative torques exerted on the movable member I by the actuating element 2 and the restraining element 3. A pair of voltage windings Illa and 55 Ib are provided upon the pole-piece asembly Iii',

for a purpose which will hereinafter appear. The terminals of the windings I 0a and Ib are brought out to a suitable terminal block Ic (see Fig. l).

The movable member i is preferably mechani-n cally balanced about the shaft 4 as an axis, and

' cally the entire magnetic circuit of the restraining comprises a pair of plates i5 and i6, separated by means of the block I4 and a lug 9a (see Fig. l) which constitutes part of the armature 9. Suitable machine screws -i and a bolt it are provided for fastening the block iii and lug 9a to the plates i5 and is. A tripping pin i9 is provided for mechanically operating the toggle mechanism or latch ofA a circuit breaker (not shown) in response to operation of ,the direct-trip device.A

The structure of the Q-shaped pole-piece as sembly i@ is best shown in Figs. 3 and 4. Referring to the latter gures, the laminations are of such size and shape as to provide an eiiective air' gap z across the entire cross-section oi the Vmagnetic circuit. A pairjof lag loops Eil and 2l are set inthe pole faces of the assembly 8S, to

provide an out-of-phase component of iiux to 22 are located, and the lagloop 22 is designed' to absorb twice as much'power, during normal operating conditions, as either lag loop 2@ or 2i. Referring to Fig. 5, which shows diagrammatielement 3, the magnetic structure i 2 is inductively interlinked with the equivalent single-turn circuit of the bus bar l, as indicated diagrammatically at la. However, because of the air gaps :c and y, the magnetic circuit divides into a leakage path 2d, an armature path 25 and a balancing path 25.

The purpose of this divided magnetic circuit is to make the mutual inductance of the voltage winding Ilia. and the main circuit 1a, equal to that of the potential winding IIib and-the main circuit 1a, so that by connection of the windings Ilia and IIib in opposition, mutual inductance effects between the potential circuit and the main circuit 'Ia may be eliminated.

Although the desired end may be accomplished in several ways, of such length that the total reluctance through the path 25 equals the total reluctance through the Vpath 26. With `this relationship of reluc tances, the windings Illa and Illb must have the same number of turns. As the power absorbed by the'lag loop 22 is equal vto that absorbed by both lag loops 20 and 2l, the iiuxes producedin the paths 25 and 26 in response to given value of alternating vcurrent in the voltage windings Illa equal in magnitude and phase position.

The effect of the ux which traverses the air- .gap path 24 is to introduce series reactance in the buscircuit 1a. Such reactance is not ordi-V narily objectionable, and in-network systems is, in fact, desirable.

The operation of the direct-trip device may be explained as follows, with reference to Fig. 5: The voltage windings I0a and IUb are preferably connected in series and energized in accordance I preferto make the air-gap z l .C may be rotated to other a main circuit voltage through a circuit which will be hereinafter pointed out. Assuming the normal direction of iiux produced by the winding 50a to be as indicated by the arrow-21, and the normal direction of uxproduced by the main gi circuit 'Ia to be as indicated by the arrows ib and 25, the uxes 2l and 25 normally add, and the vector resultant of iiuxes .25 and 26 produces a restraining force on the armature I3.

It the phase position of the current'in the i@ main circuit ia becomes such that the resultant of iiuxes 25 and 2i is reduced, the restraining torque produced by the element 3 may become less than the actuating torque of element 2, (Fig i) and the movable member i operates in counter- E@ clockwise direction. it will be noted that as the movable member i leaves its normal'position, the restraining force produced by the restraining element 3 becomes smailer and smaller because of the 'increasing air `gap in the restraining element 3, and the actuating force produced by the ele ment i2 becomes greater and greater because of the reduction of its air gap. In this way, the force exerted by the movable member i rapidly increases as it leaves its normal position. 25 The vector relationship of variables in the trip device is indicated in Fig. 6, in which the eiiects or magnetic saturation are, for convenience, not considered. Denoting the line voltage by E, the

voltage hun produced by the winding itla may be 33 represented by a vector si having magnitude and phase position determined by the impedance and phase angle of the potential circuit. An arbitrary value of line current is indicated by the vector Such a vector produces a proportional nun' 2@ in 35 the actuating element 2, which for convenience is shown to the 'saine scale. In the restraining element s, however, the iiux component Re corresponding to the current I, adds vectorially to the voltage nun 27, to produce a resultant ux 2d.

Assuming that the' lock-nut -I3c (shown in Fig. l.)v is adjusted so that the torque produced by the actuating element 2 Aexactly equals the torque produced by the restraining element for a given value oi line current, the magnitudes or actuating 35 and restraining forces are proportional to the nur.

vectors 28 and 29, respectively. As long asthe 'resultant vector 2S remains greater in scaiar.

value than the vector 28, the restraining force exceeds the actuating force and the device does not operate.

However, if the resultant vector 29 attains a value suchl as'29', terminating on a perpendicular bisector B of the voltage ilux vector 2l, the aotuating force exactly equals the restraining force, as may be seen from the geometry oi' the arrangement. To produce this condition, the corre sponding current vector must terminate on a line C parallel to line B. 'I'he line C accordingly represents the critical tripping condition or tripping characteristic oi the direct-trip device. For any' current vector which terminates in the shaded area belowvthe characteristic C, the device operates to trip open the associated circuit breaker.

Referring to Fig. 7,-" the tripping characteristic positions such as Cx, by changing the impedance phase angle of the potential circuitthrough the lcoils Ila and IIIb, as by adding impedances of various types, as is well understood in the relay art. Y By changing the adjustment of the lock-nut. I 3c, the straight-line tripping characteristic C may be converted' into circular characteristics such as D or D1.

. Returning to Figs. 14andf2, as the magnetic 75 ilar banks for supplying power equal. magnetic saturation tends to reduce the excess of Ytorque produced by the predominant elementat high current values. This has the effect of straightening out the portions of the' tripping' circle which correspond to high current values. Referring to Fig. 8, the power' direc- .tional characteristic of the trip device may be changed to the characteristic O for example, which results from the effect of magnetic saturation upon a tripping circle such as D of Fig. '1. The curve O of Fig. 8 is substantially a directional over-current characteristic. That is. to produce a tripping operation, the current must be of at least a predetermined minimum value Io, and must have a predetermined phase relationship as compared to the voltage E. J

Referring toy Fig. 9 in detail, a transformer bank Il, which may be one or a number of simnetwork 32, is connected between a feeder 33 and series impedances 4|,

`3411 and 34e for the three phases.

ytransmitting the mechanical tripping 51a, 31h and 31e to the one side of a protector circuit breaker I4. I have 1illustrated the primary windings of the transformer bank 3i connected in delta to the feeder '33 and the secondary windings connected in star with neutral grounded. but it will be understood that my invention may The circuit breaker 34 ispreferably of spe-` cialized construction having individual poles 34a, The poles 34a, 34h and 34c'are provided with separate springs 35a, 35h and 35e effective to operate the corresponding pole to fully open position whenever it is moved past dead center. A mechanical lostmotion connection 36 is provided for tripping open the two remaining poles, when any of the poles 34a, 34h or 34o has been moved beyond its dead center position. In this way, the trippingV of all the poles is brought about when any pole is tripped, although the initial latch load to trip the entire breaker corresponds to that of. a single pole only. The circuit breakeri is' provided with a closing solenoid 38, operable to close all the poles 34a, 54h and 34o as a unit.

Individual direct trip devices 31a, 31h and 31o, of the type described above, are provided for initiating the tripping of the individual poles in respense to a reverse power condition, or vector product of current and voltage, above a predetermined value in the corresponding phase. A set of lost motion trip rods 39 are provided for impulses of the direct trip devices corresponding poles 34a, 54h and 34e. n

The direct trip devices 31a, Ilb and 31o are provided with the pairs of potential windings i0a and/|01) describedabove in connection with Figs. 1 and 2. However, for simplicity, the pairs of windings 10a and l0 arer represented together as the single winding 40 in Fig. 9. The windings 40 are connected' in delta circuits which include and preferably also, saturable shunt reactors 42. The saturable ref actors 42 have the usual attened volt-ampere so that the actuating and restraining torques for a given value of line current are not to a distribution be practiced with other connections known in the art. The circuit breakcharacteristic, and tend to carry a disproportionately large share of the current through the series impedance 4I at high voltages. In this way, a great reduction of voltage applied to the windings 40 is prevented in the event of low line voltage during fault conditions. At the same time adequate voltage energy is obtained at low line voltages without excessive heating of the potential coils during normal voltage conditions.

To obtain the desired characteristics the re-- actors 42 are designed to saturate at a voltage considerably below normal line voltage, such as of normal;

The closing solenoid 38 is connected in a closing circuit which includes a set of rectifiers 43, preferably of the dry or copper oxide type, and front contact members of a voltage responsive relay 44. The voltage responsive relay 44 is connected to the output terminals of a phase-sequence filter 45, preferably of the type described 20 The phase-sequence filter 45 comprises an t0` auto-transformer 45a, having a tap to provide a voltage less than half of the total voltage impressed on the auto-transformer, for example, a 40%V tap, and an impedance consisting of a reactor 45b anda resistor 45e having a combined 55 lagging phase angle 'of 60. Assuming that the phase rotation of the secondary voltages of the transformerbank 3| is as indicated by the subscripts a, b, and c of the network conductorsua,

32h and J2e, the coil of the lvoltage responsive relay 44 is subject to a voltage equal to the vector sum of 40% of the voltage between the b phase transformer secondary terminal and thea phase transformer secondary terminal. and 40% of the voltage between the b phase transformer secondary terminal and the c phase network conductor 32o, but lagging the latter voltage by 60. As explained in the above mentioned patent of B. E. Lenehan, the translating device corresponding to the voltage relay 44 is energized in accordance with a positive symmetrical component of the polyphase voltage applied to the terminals of the filter 45 under similar conditions.

,other net-work protectors supplied from the feeder and the opening of -the feeder circuit breaker (not shown). The lock-out relay 4B is designed to drop out at a low voltage such as 10% of normal line voltage and toreclose at a considerably higher voltage such as of Inormal line voltage. I

A transfer relay 41A is provided for transferring the c-phase connection of the l,phase sequence filter 45 fnom the network side of the protector to the transformer secondary Iside whenthe network 32 is deenergized.

The operation of the apparatus shown in Fig. 9 may be set forth as follows: The various relays .and switches are shown ln the positions which they assume when the network 32 and the' feeder work 32.

If a fault occurs on the network 32, the direction of power ow remains normal, and the fault is burned o in the usual manner.

It a fault occurs on'the feeder 33, the direction of power ilow reverses in one or more phase conductors, and one or more of the direct trip devices 3'la, 31h or 31o operate toropen the corresponding poles 34a, 34h or 34e-of the network circuit breaker 34. Because of the lost motion provided in the trip rods 39, the direct trip device 37a, 31o or 31e which operates is permitted an initial movement before the tripping impulse is transmitted to the corresponding pole of the circuit breaker 34. The tripping force is, accordingly, greatly increased above that which would be available if the direct-trip deviceA acted upon the circuit breaker pole from its normal position. As soon as any of the individual poles 34a., 34h or 34e is moved beyond its dead center position, the

corresponding spring 35a, 35h or 33e completes its opening operation, and the lost motion device 36 operates to trip out the two remaining poles of the circuit breaker 34.

When the feeder 33 has been completely deenergized by the opening of all network protectors supplied therefrom and by the opening of the feeder breaker (not shown) the lock-out relay 46 drops out to connect the voltage responsive relay 34 to the phase sequencelter 45. Assuming that the network 32 remains energized, the transfer relay 41 remains closed, and the phase sequence lter 45 is energized in accordance with the polyphase system of voltages consisting of two phases of transformer secondary voltage and one phase of networkvoltage. When the positive symmetrical components of this system of polyphase voltages exceed a. predetermined value, such as"% of normal, the voltage responsive relay 44 closes to complete an energizing circuit for the closing solenoid 38 of the circuit breaker 34. The circuit breaker 34, accordingly, recloses. If, however, upon the opening of the circuit i breaker 34, the distribution network 32 is deenergized, the transfer relay 41 drops out and the phase sequence illter 45 is energized in accordance with the polyphase secondary voltage of the transformer bank 3|. In this way, it is possible for the network circuit breaker 34 to bereclosed when the network 32 is deenergized, if the transformer secondary phase vvoltages are of substantially normal value and correct phase sequence. Although I have described my invention as applied to a specialized circuit breaker construc-l tion having individual pole tripping, the invention is equally applicable to single phase circuit breakers or to polyphase circuit breakers in which the poles are operated as a unit.

Fig. 10 shows diagrammatically an application of my invention to a polyphase circuit breaker 50, with individual direct trip devices 31 for separate phases connected mechanically together as a unit. A lost motion' connection 48 is provided between the direct trip devices 3l and the latch soa/of the nrt-uitA breaker. with this arrangement the direct trip devices 31 totalize the power of all phases, and operation occurs when thepolyphase reverse power iiowexceeds a predetermined value.

I do not intend that the present invention shall' be restricted to the speciiic details, arrangement of parts, or circuit connections herein set forth, as various modifications thereof may be eiiected without departing fron the'spirit and scope of aoaaaai my invention. I desire, therefore, that only such limitations shall be imposed as are indicated in the `appended claims.

I claim as my invention:

1. ,In an alternating-current direct-trip device, 5 a movable tripping member operable to a tripping position, an electromagnetic actuating element energized solely in accordance with a current condition for moving said member to said position, anda second electromagnetic element energized 10 in accordance with a voltage condition and a current condition for preventing movement of said member to said position except under predetermined conditions of current and voltage.

2. In an alternating-current direct-trip device, 15 aymovable tripping member operable from a normal position to a tripping position. an electromagneticactuating element energized solely in accordance with a current condidtion for moving said member from said normal position to said z 0 tripping position, said actuating element being eiiective to develop increasing force with increasing displacement of said member from said normal position, and a second electromagnetic element energized in accordance with a voltage condition and a current condidtion for preventing movement of said member from said normal position except under predetermined conditions of current and voltage.

3. In an altemating-current direct-trip .de- 30 vice, a movable tripping member operable from a normal position to a tripping position, an electromagnetic actuating element energized solely in accordance with a current condition i'orl moving said member from' said normal 'position to $4 said tripping position, and an electromagnetic restraining element energized in accordance with a voltage condition and a current condition for exerting a restrainingNrce on saidl member to prevent movement thereof from said normal position except under predetermined condidtions of current and voltage, said restraining element being eiective to develop decreasing restraining force with increasing displacement of said member from said normal position. t5

4. In an alternating-current device responsive to a vector product of a voltage condition and a second electrical condition, a A voltage winding, a. series impedance, a shunt impedance, a voltage energizing circuit for said winding including said winding and said shunt impedance in parallel relationship and said series impedance in series relationship, said impedances having volt-ampere characteristics so related as to cause the percentage variation oi' voltage applied to said winding 55 to be less than the percentage variation of voltage applied to said lenergizing circuit, for a change of the latter voltage between predetermined limits.

5.'In an alternating-current device responsive 60 to a vector product of a voltage condition and a second electrical condition, a voltage winding, a series impedance, shunt impedance means having a flattened volt-ampere characteristic within predetermined-limits of applied voltage, and a 65 voltage energizing circuit for said winding including said winding and said -shunt impedance in parallel relationship and said series impedances in series relationship.

6. In an alternating-current device responsive 70 to a vector product-of a voltage condidtion and -a second electrical/condition; a voltage winding, a

. condition,

allel relationship and 'said series impedance in series relationship.

7. In an alternating-current direct-trip device, a movable tripping member, an actuating element and a restraining element arranged to exert opposing forces upon said member, each oi.' said elements having a magnetic portion responsive to a common electrical condition, said portions being designed to have similar magnetization characteristics, and means for inductively energizing said portions to the same flux density for each value Voi said condition to thereby substantially balance the eiects of magnetic saturation in said device. i

8. In an alternating-current direct-trip device, a movable tripping member, an. actuating element and a restraining element arranged to exert opposing forces upon said member, each of said elements having a magnetic portion responsive to a common electrical condition, said portions having figuration in the plane of magnetic flow, and means for inductively energizing said portions to a common flux density ior each value of said to thereby substantially balance the effects of magnetic saturation in said device.

9. In an alternating-current direct-trip device, a movable tripping member, an actuating element and a restraining element arranged to exert opposing forces upon said member, each oi said elements having an assembly of laminations responsive to a common electrical condition, said laminations being similar in size and design for both of said elements, and means for inductively energizing said laminations to a common flux density for each value of said condition, to thereby substantially balance the effects of magnetic saturation in said device.

10. In an alternating-current direct-trip device, a magnetic structure arranged to provide a magnetic circuit having a pair of parallel branches and a common portion, a ilrst means for inductively energizing said common portion in accordance with a iirst electrical condition, a second means for inductively energizing one of said parallel branches in accordance with a second electrical condition, a third means for oppositely energizing the remaining one of said parallel branches in accordance with said second electrical condition, and a common energizing circuit for said second and third means,

the mutual reactance of said rlrst and second` means being equal to the mutual reactance oi said iirst and third means, whereby inductive interference between sa'd first means and said common energizing circuit is eliminated.

11. In an alternating-current direct-trip device, magnetic structure arranged to provide a magnetic circuit having a pair of parallel the same area and similar con` branches and a common portion, means for inductively energizing said common portion in accordance with a current condition, a pair oi windings for inductively energizing said parallel branches in opposite directions in accordance with a voltage condition, and a common energizing circuit for said windings, the mutual reactances of said windings to said means being equal, whereby inductive interierence between said means and said common energizing circuit is eliminated.

12. In an alternating-current direct-trip device, magnetic structure arranged to provide a magnetic circuit having a pair of parallel branches of equal reluctance and a common portion, a first means for inductively energizing said common portion in accordance with a iirst electrical condition, a second means for inductively energizing one of said parallel branches in `accordance with a second electrical condition, a third means ior oppositely energizing the remaining one of said parallel branches in accordance with said second electrical condition, and a common energizing circuit for said second and third means, said second and third means being of equal number of effective turns whereby inductive interference between said first meansV circuit is avoided.

14. In an alternating-current"direct-trip device, a magnetic structure arranged to provide a first branch having a movable armature therein, a second branch in parallel to said first branch, and a common portion in series with both of said branches, means for balancing a magnetic condition ci corresponding condition of said second branch comprising means for inductively energizing said branches in opposite directions, a first lag loop means interlinked with part of said first branch adjacent said armature to prevent chattering oi said armature, and a second lag loop means interlinked with a corresponding part of said second branch to balance the eiect of said first lag loop means.

said first branch with aA

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