Note: Descriptions are shown in the official language in which they were submitted.
8~ 9 ~
~ 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
'~
8~9~
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.
~q~48~
~ 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.
;D4~9~
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,
--8--
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~.
--9
