Improvements in the Method of Distributing Electricity through Sub-stations, and in Apparatus for that Purpose.
Year: 1893

page_text: Date of Application, 24th July, 1893
Complete Specification Left, 24th Apr., 1894-Accepted, 2nd June, 1894
PROVISIONAL SPECIFICATION.
Improvements in the Method of Distributing Electricity through
Sub-stations, and in Apparatus for that Purpose.
We, CHARLES BERTRAM, of 128, Sandyford Road, Newcastle-on-Tyne,
Northumberland, and WILLIAM JOHN HOPE-JOHNSTONE, of 241, Camden Road,
London, Electricians, do hereby declare the nature of this invention to be as
follows:-
When electricity is to be used in districts at a distance from the dynamo or
generating station through a sub-station, according to the present practice two or
more transformers or banks of transformers are generally used; one or one set
being capable of transforming the maximum demand for current in the district
supplied from the sub-station, the others or other sets being capable of transforming
any convenient fractions of the maximum demand.
The object of this invention is to provide means of changing at the generating
station the transformer connected to the dynamo and thereby changing the
secondary mains at the sub-station to the secondary terminals of the same trans-
former whenever the measuring instruments at the generating station indicate that
the demand has fallen below a certain fraction of the capacity of the transformer
then in circuit, or risen above the capacity it is intended to convert; thereby we
obtain a higher efficiency of conversion during the hours of light load than would
be obtained should a transformer capable of converting the maximum demand be
left continually in circuit.
In order to explain the system we will consider the application of it to two
transformers or sets of transformers and will hereinafter refer to them as the
greater or lesser transformers.
:-
To attain this object, according to our method we arrange the wires as follows:-
We connect the two terminals of the primary coils of both the greater and the
lesser transformers direct to the generating station by means of separate cables, or
we connect one terminal of each of the said primary coils of the transformers to the
generating station by the same cable, and the other terminals thereof by distinct
and separate cables. The terminals of the secondary coils of both greater and
lesser transformers are separately connected to separate terminals of an automatic
electro-magnetic change-over switch hereinafter described in the sub-station, the
other terminals of said switch being connected to the secondary mains of the district
supplied by the sub-station. The said switch is operated by two solenoids or other
electro-magnetic devices which may be connected one as a shunt across either the
primary or secondary coils or in series with the primary mains of one transformer
or bank of transformers, the other as a shunt across either the primary or secondary
mains, or in series with the primary mains of the other transformer or bank of
transformers. If one of the terminals of the primary coils of each transformer have
a common cable connecting them to the generating station, if it is desired to put
the solenoids in series with the primary mains then the solenoids must be put in
series with the separate cables (and not with the one common to both greater and
lesser transformers).
When it is desired to change from one transformer or bank of transformers to
the other the connection between the dynamos and the primary circuit of the
transformer then in circuit is broken by the operator at the generating station by a
suitable switch, and the connection is then made between the dynamo and the
primary circuit of the other transformer, which being connected as described with
one of the automatic switch solenoids or other equivalent operates the switch,
thereby disconnecting the secondary mains and the secondary coil of the other

page_text: transformer and connecting the secondary mains with the secondary coil of the
transformer to which the solenoid belongs.
The change-over switch for use as above at sub-stations with two sets of
transformers consists of a tube or a bar with a superposed tube pivotted in the
centre to a bed plate, the tube being provided with an internal sliding weight of
mercury or other suitable material and adapted to oscillate. To said oscillating
device at convenient distances on opposite sides of the centre pivot the cores of the
solenoids or the moving parts of other equivalent or suitable electro-magnetic
devices are attached, and also contact pieces insulated from one another and from
the device and adapted to make and break contact with mercury cups or equivalents
to which the secondary mains and secondary transformer coils are attached; and
at either end of the oscillating device is arranged a switch for making and breaking
the circuits of the solenoids or equivalents respectively. On either solenoid or
equivalent being brought into action the switch automatically oscillates and the
contacts on one side of the centre pivot connect the terminals of the secondary
mains with the terminals of the secondary coil of one transformer and so complete
the secondary circuit, but as the other side of the bar is the exact opposite in.
action the secondary circuit of the other transformer will be broken, the primary
circuit of the latter transformer having already been broken at the generating
station.
To cut out the solenoid or equivalent after it has operated the switch and so
prevent unnecessary waste of current, the circuit of the solenoid is made through
one or other of the above mentioned end switches which is opened if the solenoid is
a shunt on either the primary or secondary circuit and closed so as to short circuit
the coil if it is in series in the primary circuit; this operation is accomplished by
the action of the self acting weight directly or through the bar. The said weight
in the same travel closes or opens the switch of the other solenoid as the case may
require, so as to leave it ready for reversing the operation when required.
Dated this 22nd day of July 1893.
J. C. CHAPMAN,
Agent.
COMPLETE SPECIFICATION.
Improvements in the Method of Distributing Electricity through
Sub-stations, and in Apparatus for that Purpose.
We, CHARLES BERTRAM, of 128 Sandyford Road, Newcastle-on-Tyne, in
the County of Northumberland, and WILLIAM JOHN HOPE-JOHNSTONE, of
241 Camden Road, London, in the County of Middlesex, Electricians, 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 :-
When electricity is to be supplied from sub-stations at a distance from the
generating station it is usual to employ two or more transformers, or banks of
transformers, one of these being of sufficient capacity for the maximum load and
the other for any convenient fraction thereof.
Now the object of this invention is to enable one or other of these transformers
or banks of transformers to be brought into use at will, that is to say, to enable the
secondary mains to be charged by one or other of these transformers, or banks of
transformers, by merely actuating a hand switch when the reading on the
measuring instruments at the generating station shows this to be necessary. By
means of our invention a considerable saving is effected, as when the load is low the
smaller transformer is switched into circuit with the secondary mains, and there is
less loss in maintaining such smaller transformer magnetised than if the larger one
were maintained magnetised.

page_text: In order that our invention may be more readily understood we shall now
proceed to describe it in detail and for that purpose we shall refer to the
accompanying drawings which illustrate one type of our invention.
:
Figure 1 is a side elevation of a form of our change-over switch hereinafter to be
described.
Figure 2 is a cross section of the same.
Figure 3 shows the application of our invention to a simple case of the ordinary
two wire system.
Figures 4, 5 and 6 illustrate a case similar to that shown in Figures 1, 2 and 3.
except that the secondary mains are arranged on the three wire system, and the
switch modified to accord therewith.
We shall first describe one form of our change-over switch the said form being
one which gives good results in practice. Referring to Figure 1, A. is a rod to
which is attached the tube a' closed at both ends and having therein a quantity of
shot or mercury or the like so as to obtain what is known in contrivances of this
kind as a positive action. The rod and tube oscillate together on the centre a².
On each side of the pillar a³ and affixed to the bed-plate a is a solenoid, that on the
left being lettered B₁ and that on the right B². 61 62 are the cores of the said
solenoids. C1, C2, C3, C4, are mercury cups, and c¹, c², c³, c, are bridging contact
pieces insulated from one another and from the rod A. At each end of the switch
is a device D' D2 for opening and closing the solenoid circuit after the switch has
acted. The said devices consist of the levers d¹ d² having at one end the heavy
bridging contacts d³ d which dip into the cups of mercury d³ do. At each end of
the oscillating rod is a small striking pin d' d. E and E' (see Figure 3) are the
secondary mains fed through the transformers F and F. G is the switch at the
central station by means of which the current is switched from one transformer to
another as desired, when it is seen by the reading of the station instruments that
such a change is desirable.
To understand the action of our invention let us assume that F is the smaller
and F the larger of the two transformers, that the switch is in the position shown.
in Figure 3 and that it is desired to switch the smaller transformer out of circuit and
the larger transformer into circuit. The switch G will be reversed in position from
that shown in Figure 1, and the primary current instead of passing by conductor 1,.
primary winding p' and conductors 2 and 3, will now pass by conductor 4, primary
winding and conductors and 3. The secondary winding of transformer F will
now no longer be energised, but the secondary winding of transformer F will be.
energised, and the current in it will flow through secondary winding S2 conductors 10
and 9, device D2, conductor 8, solenoid B2 and conductors 7 and 6 back to secon lary
winding S2. As soon as the current flows through solenoid B2, its core ² is.
attracted and the right hand side of the rocking-lever pulled downwards so that the
bridging contact pieces c³, e dip into the mercury cups C³, C. At the same time.
the pin de strikes against the lever d² and raises the bridging contact piece d' out
of the cups d and breaks circuit at D2 so that solenoid B is no longer energised..
The current will now pass from secondary winding S2 by conductors 10 and 14,.
mercury cups C and bridging contact piece c, conductor 13, secondary mains Ei.
and E, conductor 12, mercury cups C³, bridging contact piece c³, and conductors 11
and 6 back to secondary winding S. The larger transformer is now feeding the
secondary mains.
Suppose now that the load falls. This is indicated at the central station, when.
the attendant puts switch G back to its normal position, that is to say into the
position shown in Figure 3. The primary current now passes by conductor 1,
rimary winding p', and conductors 2 and 3. Secondary winding S' is now
energised, and the current passes by conductors 15 and 16, solenoid B', conductor 17,.
levice D' and conductors 18 and 19 back to secondary winding S¹. Core is now
ttracted and the rocking lever is brought back into its normal position, that is to
ay, into the position shown in Figure 1 when bridging pieces c' and c² dip into
mercury cups C and C³ and circuit at D' is broken by-pin & causing bridging

page_text: contact d³ to be raised out of mercury cups d³. The circuit through B' is now
broken and the current flows from secondary winding S¹ by conductors 15 and 20,
mercury cups C³, contact piece c³, conductor 21, secondary mains E' and E,
conductor 22, mercury cups C', bridging contact and conductors 23 and 19 back
to secondary winding S¹. The secondary mains are now charged by the smaller of
the two transformers.
Figure is a vertical section through the change-over switch, the parts being
indicated by the reference letters.
Figures 4, 5 and 6 show the application of our invention to an installation on the
three wire system. It differs from the case shown in Figures 1, 2 and 3 merely in
that there are three sets of mercury cups and bridging contact pieces instead
of two.
It will thus be seen that a considerable saving is effected, inasmuch as the loss
sustained by keeping the larger transformer magnetised whilst the smaller trans-
former is sufficient for the work is avoided.
We desire it to be understood that we do not limit ourselves to the form of
change-over switch described. Any competent electrical engineer could modify the
details of the switch to an almost indefinite extent without departing from the spirit
of our invention. The form of switch shown is however a practical form which will
give good results in practice.
Although we have only shown the application of our invention to a simple case
of two single transformers, it will be readily understood that it is equally applicable
to the case of two groups of transformers at a sub-station, and that there may be
as many sub-stations as is desired on each pair of primary main circuits.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manuer the same is to be performed, we declare that what we
claim is :
1. The method of distributing electricity through sub-stations which consists in
switching the transformers or groups of transformers alternately into and out of
circuit substantially as set forth.
2. The method of distributing electricity through sub-stations which consists in
passing the current through one or other of two primary circuits leading from the
central station to a sub-station, there causing a solenoid or other equivalent device
to actuate a switch which brings the secondary winding of one transformer or set of
transformers into circuit with the secondary mains and at the same time cuts the
secondary winding of the other transformer out of circuit, substantially as set
forth.
3. The method of distributing electricity through sub-stations which consists in
passing the current through one or other of two primary main circuits leading to a sub-
station, there causing a solenoid or its equivalent to actuate a switch which brings
the secondary winding of one transformer or set of transformers into circuit with
the secondary mains whilst at the same time cutting the secondary winding of the
other transformer or set of transformers out of circuit, cutting the said solenoid or
its equivalent out of circuit by a device, such for example as D, and bringing the
other solenoid or equivalent into circuit so as to be ready for the next action of the
switch, substantially as set forth.
4. The change-over switch substantially as set forth.
5. The specific form of change-over switch illustrated by Figures 1, 2 and 3.
e The ifin form of chance-over switch illustrated in Figures 4. 5 and 6.
Vated tuis 2 ay pin
J. G. LORRAIN, M. Inst. E.E., M. Inst. M.E.,
Norfolk House, Norfolk Street, Strand, London, W.C.,
Chartered Patent Agent.