CA1048090A - Circuit breaker protective shutter and current transformer apparatus - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE:
A circuit breaker protective apparatus including a safety shutter assembly housed in the cubicle of an electric switchboard and forming a diaphragm separating front and rear sections of the cubicle. One or more toroidal winding current transformers are mounted on the partition member of the safety shutter assembly which is provided with ports or pass-through holes corresponding to the insulated line terminal connectors to permit access thereto; each transformer surrounds a corres-ponding opening in the partition member and is magnetically linked with the respective line terminal when the circuit breaker is closed. Both the partition and safety shutter making up the shutter assembly are movable horizontally with respect to the vertical rear wall of the cubicle and the shutter is also movable vertically and parallel tot he partition member to shut the ports of the partition member.

Description

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~ he present invention relates to an impro~ed protective shutter de~ice, for cubicles making up an electric boaxd, which allows the electric circuit-breakers housed in the board cubicle~
to be connected ~afely and simply The apparatus of the inYention i~ constructed ~imilarly to that of Canadian Patent serial no.
1~0089494, is~ued on April 12, 1977~ to Ciboldi; this invention con~titutes an improvement over the subject matter descrlbed in that patent, in that it ~urther includes in~trument current trans-former~ to measure the value o~ the current flowing through the main circuit.
The prior art includes several known solutions for con-necting the in~trument current transformers with their relevant primary circuits.
One often-followed practice con3ist~s of placing the in-ætrument tran~ormer~ between the bus-bars or between the in-coming cable terminal and the fixed contact elements of the electric board cubicle equipped with draw-out circuit breaker. A ma~or dis-ad~antage o~ this practice is that the power supply to those parts which are metal connected with the tr~lsformer must o~ neces~ity be cut o~f when it is desired to either change the transfo~mer ratio or replace the instrwment transformerO
A second frequently-used practice contemplates placing the instrument transformer~ on the movable truck of the draw-out circuit breake*. ~his allows acce~ to the instrument tran~former after power has been ~hut o~f only to the panel o~ interegt. on the other hand, this solution impo~e~ rather complicated and ex-pensive connecting linkages on the primary circuit~. Moreover~ a further disadvantage of this second prior art sy~tem arises when-ever the circuit breaker is to be replaced: when the instrument transformers are placed on the same truck which ~upport~ the cir-cuit breaker, there occurs a loss of interchangeabilit~ with other circuit breakers equipped with instrument transformers having di~ferent values of rated current. It therefore becomes necessary '~

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to also replace the instrument transformers, a ~o~ which is not very easy, not at all quick, and is also expensive.
In acldition? with both of the above mentioned ~stems, the power circuit~ require two more attachement points whenever in~trument transformers are to be connected.
A third known pra¢tice consi~ts of using toroid-type instrument trans~ormers which are only magnetically ~inked with the live power circuit~; this eliminates the requirement of the additional attachement points on the same power circuits of the aforementloned prior art sy~tems. In thi~ third known construc-tion, the instrument transformer, after the circuit brea~er has been drawn out from its cubicle, remain3 at its original placement point, namely at the rear of the cubicle protectiYe shutter and be-come~ acce~sible only wh~n power to the concerned board section, namely the rear part, has been shut off.
As pointed out above, all these known solutions have one or more disavantage~ which cause substantial dif~iculty for both routine and overhaul maintenance. In practice, these ~if~iculties arlse any time the circuit breaker is to be switched o~f and drawn out from it~ own ~ubicle as well as whenever the circuit bre~ker is to be replaced by another equipped with an instrument trans-former of a different rated current ~alue.
A principal object of this invention is the construction of a shutter protection device for electric boards equipped with instrument current tran~former~ which are acces~ible on drawn-out cir¢uit breaker without haYing to shut off voltage to the primary conductors. It is a further object of this invention to equip the electric board9 and more specifically the shutter protection device, with instrument transformers which are arranged to allow for their replaoement under the safest possible conditionæ. It is a still further object of this invention to make use of instrument current ;~ransformers requiring no attachment to the prima~y sircuit~.

~ 8~0 Still another obJect o~ the present invention i8 the realization of a de~ice which~ while attaining the above specified objects, nevertheless maintain~ all of the positive feature~ nd advantage~
offered by the known solutions, and in particular, the positive fea-tures and the advantages already described in the above-mention-ed Canadian patent. It iB, finally, a further object of the present invention to pro~ide a protective derice, equipped with i~strument transformers, which9 due to it~ construction, operation and maintenance simplicity, effect~ a ~ig~ificant saving of space and reduction in manufacture and service costs compared with the known devices. These and other objec-t~, which one skilled in the axt can better deduce from the following detailed description, are advantageously achieved by the apparatus of this invention-j which includes an electric board protective device of the type described in said Canadian patent. A ~a~et~ shutter assembly, comprising a partition member and a shutter member, i~ houæed in the cubicle of the electric board assembly and forms a diaphragm arrangement which separates the front and rear section~ (or chambers) of the cubicle.
~he partition and shutter are disposed in clo~e facing relation~hip to each other a-nd are moYable horizontally with respect to the ver-tical rear wall of the cubicle; the shutter is also movable ~erti-cally and parallel to the partition. ~he latter is provided with ports or pass-through holes for access to the circuit line terminal connectors and corresponding bushing insulators; the shutter is de3igned to shut the ports or pass-through holes when the movable breaker a~sembly is drawn out of the cubicle~ ~he circuit breaker truck is provided with means to control the vertical movement of the ~hutter and the horizontal translational movement of both the partition and ~hutter to expo~e the line terminal members for connection with the breaker member~ when the truck is dra~n into the cubicle and to seal off access to the line terminal members when the breaker truck is moved to the draw-out po~ition.

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~ he invention al~o includes at least one instrument transformer o~ toroidal winding ~tyle, ~or metering the current intensity of the main circuit, installed on the partition member on the side ~acing the front section of the cubicle or board, in coxre~pondence with one o~ the pass-through ports. When the cir-cuit breaker is drawn out~ the ~afety shutter assembly proteets the front cubicle section against the pximary cirouit voltage pre-~ent in the rear section. ~he partition-mounted winding then be-comes acce~ible without having to disconnect the voltage from the ~o main terminals. When~the circuit breaker i~ drawn in and connected with the main circuit, the toroidal winding current transfor~er move~ hori20ntally with the partition member and becomes magnetic-ally linked with the line terminalsO It is to be pointed out that the term "electric board" generally mean~ a unit made up by group-ing ~everal basic, ~ingle cubicles. In the following description~
use will be made of both terms "cubicle" and "board", indiscriminately.
~ ig. 1 schematically ~hows a side view section of the ~quipment with the circuit breaker disconnected and fully drawn out9 safety shutters fully clo~ed, and toroidal in~trument current tran~-formers not linked with the primary circuit; and ~ig. 2 ~how~9 al90 in side view section, the ~quipment with the circuit breaker fully drawn in and connected, safety shutter~ ~ully open and at their tra~el end, and toroidal instru-ment current tran~formers linked with the primary circuit.
~ In order to simplify the arawings, the figures show only one circuit breaker pole. It is to be kept in mind that the speci~ication and the drawings of this invention apply as well to a common three-pole c-~rcuit breaker.
3o ~he apparatus of the in~ention includes a 3~ationary frame (or electric boaxd) 14~ preferably of metal con~truction, and having a rear panel 141 through which pass the high voltage ~ 48~901 line terminal connectors 23 protected by bushing insulators 11. A
k~own draw-out type of circuit breaker assembly is housed in a ca~ing 1 mounted on a truck 16 provided with wheels 15. ~he break-er components themselves may be on any appropriate known type and therefore will not be de~eribed ~urther.
Mounted on the fr~me 14 is a safety shutter a~embly including a barrier, or partition member 4 and a shutter member 6.
~he partition member 4 is mounted for horizontal movement along at lea~t one9 but generally two or more~ support a~ms or guides 5 which in tu~n are rigidly mounted to the back panel 14t.
The ~hutter member 6 i~ movable vertically and is guided by upright members 8 fixed to top and bottom portion~ of the main Yhutter 4~ ~y virtue of this mounting, sllutter 6 moves with parti-tion 4 a~ the latter is displaced horizontally in a manner to be described hereinafterO
~ he vertical movement of the shutter 6 is accomplished through a mechanism which includes a linkage rod 7 having one end connected to the shutter 6 and the other end thereof pivotally connected to one ~nd of a linkage block 9; block 9 is connected to a side wall of the frame 1~ by a member 12 which defines a pivot axis about whioh linkage block 9 is rotatable. Pivotal movement of linkage block 9 i~ obtained by mean~ of a rib member 10 fixed ~o the truck 16 carr~ing the circuit breaker element~. As the truck 16 is moved into the breaker cubicle defined by frame 14, rib 10 engage~ a pin 17 on linkage block 9. As truck 16 moves further into the electric board cubicle, rib 10 pushes against pin 17, thereby causing linkage block 9 to rotate in a counterclockwise ~irec-tion (relative to the position shown in Fig. 1) abo~t pivot axis 12~ ~he rotational movement o~ linkage block 9 is translated into a substantially upward vertical movement of l~nkage rod 7 to there-by urge auxiliary shutter 6 up~ardly along the track defined by guide members 8.

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The partition member 4 is, as previou~ly noted, mounted for hori~ontal movement along support arms 5. In the disclosed embodiment9 partitlon 4 i~ normally u~ged into its rest po~ition (~ig, 1) by means of spring3 3 disposed around a central rod 24 and housed in a suitable tubular casing 13 fixed at one end 18 to the ~rame 14 and having an opening at the other end through which rod 24 projects for connection to the partition 4. In it~ initial or rest position, the parti-tion 4 is located in front of the in-sulator-protected line terminal~ 23 to ~eparate the main cubicle space from the terminal contac-t space. Access to the terminal connectors i9 obtained through corresponding openings 19 in parti-ti~n 4. Openings 19 are large enough to clear the bu~hing~
insulators 11 when the shutter assembly i~ moved to its rearmost position against rear wall 14'.
In the ~ull draw-out po~ition of the breaker assembly (Fig. 1), shutter 6, located in it~ lowermDst position, cover~
openings 19 in partition 4 to prevent acces to the line contact terminals. Shutter 6 has at least one opening 20 90 that in an intermediate draw-out po~ition of the breaker a~embly, with ~hutter 6 at its uppermost position9 opening 20 coincides with the upper opening 19 of partition 4 to permit access to the upp~r line terminal 23; the bottom of shutter 6 is raised sufficiently to ex-pose the lowermost opening 19 o~ shutter 4 to thereby permit access to the lower line -terminal 23. In a minor modification, shutter 6 could be made longer and provided with a ~econd opening 20 coin-ciding with lower opening 19 of partition 4 in the raised position of shutter 6.
~ reaker hou~ing 1 includes pressing members 2 either in-tegrally formed therewith or fixed thereto in a known manner; mem-bers 2 contact partition 4 as the breaker housing 1 i~ dra~n intothe cubicle in frame 14. As the breaker assembly 1 moves into the cubicle toward the full draw-in position, members 2 pres~ against partition 4 until, in the Eully drawn-in position (Fig. 2), parti-tion 4 and shutter 6 are disposed adjacent the rear panel 14';
shutter 6 is maintained in its raised position by the engagement of rib 10 against pin 17, preventing clockwise rotation of the link-age block 9.
The apparatus also includes two instrument current trans-formers 21 and 22 of toroidal style, which are mounted on main shutter 4 coaxially with holes 19.
The operation of the safety shutter assembly itself is described in detail in said above Canadian patent. The following description will relate the shutter assembly operation with that of the transformer windings of this~invention.
The circuit breaker assembly is shown in Fig. 1 in its dlsconnected state in which the circuit breaker lS fully drawn out and the shutter assembly is fully closed. At this time, instrument transformers 21 and 22 are disconnected from the primary circuit and are unaffected by any voltage or current in the high voltage line. In this position, shutter 6 and partition 4 cooperate to seal off the rear part of the electric board 14 from the front part in which the transformers 21 and 22 are located. Thus, the trans-formers may be safely worked on or removed without danger of a workman coming into contact with the high voltage terminals loca-ted behind the shutter 6.
The toroid winding transformer used in this invention has the advantage that it can be magnetically coupled with the high voltage circuit without having to wire the transformer directly to the high voltage line.
Fig. 2 shows the circuit breaker connected to line ter-minals 23. In this position, the cam assembly of the linkabe hlock 9 and rib member 10 have moved shutter 6 upwardly to free the open-ings 19 in partition member 4. Pressing members 2 have pushed the , 3~ q~
partition 4 horizontally to the right to expose the terminal bushings ll. In this position, instx~ment tranformers 21 and 22 surround the respective bushings 11 and their rele~ant line ter-minals 23. ~he transformer coils are now magnetically linked to the respective high voltage lines. Access to the transformers or to the circuit breaker terminals is prevented by the interposed casing lo ~ he apparatus of this invention achieYes the advantages of extreme simplicity and high service safety: the full drawing out of the circuit breaXer is possible only when both the partition and shutter ha~e reached their fully cloRed positions. Even wh~n circuit breaker l is fully disconnected ~rom the line terminals but not completely drawn out of board cubicle 14 (~ig. l), the parti-tion 4 will already haye reached its rest position, thus clearly separating the live chamber of the cubicle (containing the line terminalæ) from the section within the operator's reach; further access to the cubicle and transformer coils 21 and 22 can be had only after circuit breaker l has been completely drawn out and re-movad from the board cubicle. ~his guarantees that no live member can accidentally remain uncovered~ an unintentional manual opening of the shutter assembly being impossible.
Any operation directed to overhaul, ratio changing, re-placement or simple repair of the instrument transfor~er may in this way be made much easier and with complete safety to the oper-ator.
Iwo distinct instrument transformers 21 and 22 have been shown in the drawings as magnetically linked with terminals 23;
however, it is to be noted that the instrument current transformer can be also installed only in the upper or only in the lower posi-tion according to the service needs of the electric board, as thisis unimportant from both electrical and magnetic points of view.
It is also to be pointed out that, according to this invention, 9~
toroidal style windings are to be nece~sarily used, as this style is cheaper than others and results in a saving of the amount of materials used, with a consequent price decrea~e for the whole equipment. Also, the placement of the toroidal transformer~ on shutter 4 is made in a way that involves little or no dimensional increase (particularly, in the depth) of the board, in comparison with the case where no instrument transformer i5 required.
It i~ to be understood that various mbdifications in the ~tructural det~ of the pre~erred embodiment described herein ma~ be made within the scope of thi~ invention and without depart-ing from the spirit thereof. It is intended that the scope of this invention shall be limited solel~ by the hereafter appended claim~.

Claims (2)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A protective apparatus for electric board cubicle circuit breaker assemblies having a frame including at least rear and side walls defining a cubicle therebetween, means mounting high voltage line terminals on said rear wall such that said ter-minals extend at least partially into said cubicle, and a circuit breaker housing movable into and out of said cubicle and having contact members located thereon which mate with said line terminals when said housing is fully drain into said cubicle, said protective apparatus comprising:
a protective shutter assembly located in said cubicle and substantially dividing said cubicle into front and rear sec-tions, said shutter assembly including a partition member having openings therein corresponding to the locations of said line terminals in said cubicle and a shutter member mounted on said partition member, said shutter being horizontally movable with said partition member and movable substantially vertically between closed and open positions, wherein, in said closed position, said shutter member covers said openings in said partition member to prevent access to said line terminals, and, in said open position, said shutter member uncovers said openings in said partition mem-ber to permit access to said line terminals:
means mounting said shutter assembly in said cubicle for substantially horizontal movement toward and away from said rear wall between the first and second positions, wherein, in said first position, said shutter assembly is spaced from said rear wall a distance greater than the distance said line terminals ex-tend into said cubicle from said rear wall, and wherein, in said second position, said shutter assembly is located adjacent said rear wall such that said line terminals project through said openings in said partition member; and at least one toroidal winding instrument transformer for metering current through said line terminals mounted on the sur-face of said partition member facing said front section adjacent to and in correspondence with one of said openings in said parti-tion member.

2. The protective apparatus according to claim 1, further comprising a plurality of instrument current transformers mounted on said front section facing surface of said partition member in correspondence with respective ones of each of said open-ings in said partition member.