Improvements in Switch Boards for the Control of High Voltage Electric Circuits and Apparatus.
Year: 1898

page_text: Date of Application, 19th Mar., 1898-Accepted, 25th June, 1898
COMPLETE SPECIFICATION.
Improvements in Switch Boards for the Control of High Voltage
Electric Circuits and Apparatus.
I, HORACE FIELD PARSHALL, of 83, Cannon Street, in the City of London,
England, Electrical Engineer, do hereby declare the nature of this invention, and
in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement:—
My present invention relates to an improvement in switch-boards for the
control of high voltage electric circuits and apparatus.
In interrupting high voltage continuous or alternating current circuits by
means of the usual switching mechanism it frequently occurs that vicious arcs
are formed between the switch blade and its contacts which are difficult to ex-
tinguish. These arcs may burn the contacts and adjacent parts of the switch as
well as other apparatus mounted on the switch-board in proximity to the high
tension switch contacts. A more serious result is the short circuiting of the
electric generating apparatus occasioned by the flaming arc, following the
rupture of such a circuit, establishing the electrical circuit between adjacent
terminals or switch contacts of opposite polarity. With the usual construction
of switch-board short circuiting of apparatus or circuits is of frequent occurrence
due principally to the disposition of switch contacts of opposite polarities in
proximity to one another, and on the same side of the switchboards.
aware that partitions of fireproof electrically insulating material have been placed
between the switch contacts of opposite polarity for the purpose of preventing
short circuiting between adjacent terminals or switch contacts by the arc due to
the opening of the high voltage circuits and more especially when transmitting
considerable electric energy. I believe, however, that the switch contacts
separated by fire-proof partitions of this description have heretofore always been
placed on one and the same side of the switch-board proper thus failing to
utilize the switchboard itself as a barrier.
I am
In order to avoid the difficulties consequent to present practice I propose to
utilize the switch-board itself as a partition separating the switch contacts, thus
rendering the establishment of the are between adjacent terminals of the same
conductor practically impossible.
I am aware that the simultaneous opening of high voltage circuits has been
arranged for at two or more switch points or contacts in series thus reducing the.
electromotive force per break in inverse proportion to the number of breaks and
this for the purpose of more easily interrupting the high voltage circuit. I am
also aware that the several switches and contacts for interrupting one and the
same conductor in the manner last described have all been placed on one side
of the switch-board and have even been separated from one another by fireproof
electrically insulating partitions for the reasons already stated. I believe myself to be
the first, however, to place the switch contacts of one and the same conductor to
be interrupted at more than one point simultaneously, on opposite sides of the
switchboard proper, for the purpose of utilizing it as a most efficient barrier or
partition separating these contacts. In addition, I prefer to place large electri-
cally insulating fireproof partitions between the switch contacts of different
polarities in order to prevent short circuiting between said contacts by the arcs

page_text: resulting from breaking the circuit connections at the switch points. In the
accompanying drawings I have illustrated a practical form of my invention;
Figure 1 being a front elevation of the switchboard arranged for the simultaneous
opening, at two distinct contact points per circuit of a high voltage circuit com-
prising three conductors; Figure 2 a sectional view of the same switchboard,
and Figure 3 a rear elevation, (only one of the three switches being shown in this
figure).
Referring to Figure 1, T are the terminals of the three circuits on the front of
the switchboard S of electrically insulating fireproof material, the terminals T
on the back of the switchboard being the corresponding terminals of the same
circuits thus interrupted at two points simultaneously. The switch contacts D, D₁
receiving the blades A2 of the switch arms A, A¹ are attached to or form part of
bolts B passing through electrically insulating supports I; washers W separate
the terminals T, T¹, from the insulating supports I. A nut N screwed down on
washer secures the bolt B to its support. The latter is reduced in diameter
and passes through the switchboard, being held firmly in place by the nut, of
electrically insulating material J. A cap H of electrically insulating material
covers the nut N and washer O thoroughly protecting them from possible arcs at
the adjacent terminal. The switch arms A, A¹ are pivoted at P and P¹ and each
provided with a toothed segment A³ meshing together for the purpose of ensuring
simultaneous opening and closing of the circuit at contacts D and D¹ as shewn in
Figure 2. In this figure the switch is shown in its closed position, the dotted
lines indicating the position of the switch arms when the circuit is open. R in-
dicates a stop of elastic material, such as india rubber, intended to lessen the
shock due to falling of switch arms on opening the switch. The casting h,
supporting the pivots P and P¹ is secured to the switchboard S by bolts 9 and
nuts and thoroughly insulated from the switchboard by electrically insulating
material and m. The cables leading to the high voltage circuits or machines are
attached to the terminals T, T¹ in the usual manner. For the purpose of separat-
ing the adjacent terminals and switch mechanism of one circuit or of one con-
ductor from that of another, the partitions Q and V of fireproof electrically in-
sulating material are placed between the switches, as indicated in Figure 1, a
plate of electrically insulating material d secured by screws i to the partitions Q,
prevents arcing over the top of the switchboard S or partitions Q and V. The
switchboard S being of the panel type, partitions Q₁ may be placed at each side,
as shewn in Figure 1, to separate the adjacent switch mechanism from apparatus
on neighbouring panels.
Vertical rods U of wood or other suitable electrically insulating material pro-
vided with upper and lower extensions K and F serve to unite the switch arms
to the tripping lever L. The upper extensions K are forked and receive the
horizontally projecting portions A of the switch arms A' between the same as
is shewn in Figures 2 and 3. These forked extensions K are also provided with
vertical slots K³ closed at their upper ends; and adapted to receive two hooks r
projecting from the sides of the horizontally projecting portions A* of the switch
arms A¹ On the lower end of said forked extensions are formed
ears K³ which receive eye bolts t to which are attached spiral springs M
having their upper ends attached to the hooks r. It is evident that a
downward movement of the rod U will at first stretch the springs M and finally
open the circuit at the contacts D and D¹ with great rapidity. The tension of
the springs may be regulated by moving the nut e and check nut e¹. The tension
to be applied to these springs is evidently dependent upon the effort required to
release the switch blades from their respective contacts D, D¹. It is not intended
that the switch shall be opened by the engagment of the slotted forked extension K
with the hooks r except in case the springs do not act. Perfect electrical con-
tinuity between the switch arms of one and the same circuit is assured by the
flexible copper conductor C electrically uniting the arms near their pivots P, P¹
without interfering with their movement. The several arms of lever L are

page_text: attached to the several forked lower extensions F of the switch rods U by means
of pins a secured in place by cotter pins j. The shaft G mounted in brackets E
serves to support the lever L, the brackets E being attached to the switchboard S
by bolts 6 and nuts v. The insulated handle Z of the lever L is arranged at the
front of the switchboard, the lever L passing through an opening in the switch-
board which is protected by plate secured by screws q.
It is clear that an upward movement of the handle Z of lever L will simul-
taneously open the three circuits controlled by the switchboard shown in accom-
panying drawings at contacts D and D', each circuit being interrupted at two
When the switch is to be closed a down-
different points as already described.
ward movement of the handle Z causes the fork K to engage with hooks r thus
raising the switch arms from the dotted position of Figure 2 until the circuit is
made at contacts D and D. The movement of switch arms is simultaneous
with those indicated by the letter A' owing to the intermeshing segmental gears A³
clearly shown in Figure 2.
I believe that the above described disposition of switching mechanism for the
control of high voltage circuits embodies all the advantages of simultaneous
interruption of a high voltage circuit at several points with a most efficient
isolation of adjacent switch contacts of the same polarity as well as adjacent
contacts of opposite polarities, thus effectually preventing the establishment or
inaintenance of the destructive high voltage are at the opening of such circuits.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:-
1. A switchboard for controlling high voltage continuous or alternating electric
circuits comprising a panel of electrically insulating fireproof material on which
is mounted all the mechanism for opening and closing the several circuits, the
conductor of any one of the several circuits controlled from the switchboard being
interrupted at two distinct and separate switch contacts, which together with
their respective electrically connected switch-arms are situated on opposite sides
of the panel with the object of utilizing the latter as a most effective barrier
separating the respective switch contacts of a given conductor.
2. A switchboard for controlling high voltage continuous or alternating current
circuits comprising a panel of electrically insulating fireproof material on which
is mounted all the circuit opening mechanism, the conductors of each of the
several circuits controlled from the switchboard being interrupted at two distinct
and separate switch contacts, which together with their respective electrically con-
nected switch-arms are situated on opposite sides of the panel with the object of
utilizing the latter as an efficient barrier separating the respective switch-con-
tacts of a given conductor; the switch contacts on one side of the panel being
separated from each other by large barriers or partitions of electrically insulating
fireproof material and a partition or barrier of the same material covering the top
of the switch board and the tops of the vertical barriers, with the object of
preventing short circuiting between adjacent terminals or switch contacts of
opposite polarity; electrically connected switch-arms for opening and closing
the several circuits simultaneously at two distinct and separate switch contact
points, and a single lever actuating all switch arms simultaneously.
3. A switchboard embracing the special construction and arrangement herein
described and illustrated in the accompanying drawings.
1
1000