Improvements in Distribution of Electricity.
Year: 1895

page_text: PROVISIONAL SPECIFICATION.
Improvements in Distribution of Electricity.
I, ARTHUR WRIGHT, of 26 Park Crescent, Brighton, Electrical Engineer do
hereby declare the nature of this invention to be as follows:-
My invention has for its object the obtaining of greater economy in alternating
current systems of supplying electricity and the obviating as much as possible the
necessity of running high tension alternators and transformers at periods of
light load.
I supply the low tension distributing mains, such as the ordinary "three wire"
public supply mains, with low tension alternating currents direct from generating
stations and produced preferably by low tension alternators, and at periods of heavy
load I supplement the supply with high tension alternators feeding the low tension
distributors through transformers situated at different points of the network of
mains, the high tension alternators being properly synchronized with the current
from the low tension alternators I am therefore enabled wben desirable to simul-
taneously supply the low tension distributing mains with electricity direct from both
low tension alternators and high tension alternators, the latter through the medium
of transformers; at periods of heavy load the low tension alternators may or may
not continue to supply the mains.
I sometimes also supply low tension alternating currents direct from generating
plant situated in substations at various points of the distributing mains and the
supply is supplemented at periods of heavy loads by a high tension source of supply
situated elsewhere and feeding the same distributing mains through the medium of
transformers, these may be also be placed in the same substations.
Instead of employing low tension alternators at the generating station I sometimes
supply the low tension distributing mains with electricity generated by the high
tension alternators and transformed by transformers situated at the generating
station itself into low tension alternating currents.
At periods of light loads the transformers in the substations can be disconnected
automatically or by hand from the low tension distributing & the high tension
mains so as to absorb no energy until the load is such as to require their use.
The switching on and off of the above substation transformers may be
automatically effected by the currents in the low tension distributing mains in the
neighbourhood of these substations or through the medium of special wires running
to the generating station to them.
Dated this 2nd day of May 1895.
ARTHUR WRIGHT.

page_text: I, ARTHUR WRIGHT, of 26 Park Crescent, Brighton, in the County of Sussex,
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 invention relates to improvements in the distribution of electricity by means
of which greater economy is obtained.
At present we may take it for granted that in installing an electric supply system
for an ordinary district it is expedient that the distributing mains laid be for
currents of low tension and this holds true whether the said currents be continuous
or alternating ones.
There are two methods of supplying the distributing mains with electricity now
in ordinary use, namely (a) the low tension feeder system and (4) the high pressure
feeder system. In the first of these cases electricity is generated at low pressure
at the central station and conveyed to selected feeding points in the distributing
network direct; whilst in the second of these the electricity is generated at high
pressure at the station, conveyed to the feeding points, and there transformed down
by means of transformers of one kind or another to a low pressure suitable for the
distributing mains.
In the first of these systems, as is well known, the efficiency is at its highest at
light loads, as the CR or conductor losses are then negligible. At periods of
heavy loads, however these losses are proportionately very great.
In the second of these systems the losses, in so far as the feeder cables are
concerned, are negligible both at light and at heavy loads, but the loss sustained in
keeping the transformers magnetised and ready to supply current is very great
particularly during the period of light load, at which period the system is extremely
inefficient.
The foregoing being granted, it naturally follows that an extremely economical
way of supplying districts of sufficiently wide extent, is to supply the area within a
certain radius on the first of these systems and the area outside that radius on the
second of the said systems. Thus in the case of a well-known city the electric
supply is being carried out at present by means of these two systems simultaneously
the distributing mains of the central area being fed by low tension continuous
current feeders and the distributing mains of the outer area by high tension
alteruating current feeders through step down transformers, the two sets of
distributing mains being of course separate and distinct.
In a system embodying my invention alternating currents alone are employed
and the distributing mains of the two areas are not separate and distinct, but
constitute a single network.
In the accompanying drawings in which for greater clearness, the circuits are
represented by single lines, Figure 1 diagrammatically illustrates a case in which
that portion of the network within the dotted circle A represents the central area,
or portion which by reason of density of demand and proximity to the central
station (diagramatically represented by the ellipse X) can be more economically
supplied by low tension feeders than by high tension ones through the medium of
transformers. The portion outside the said circle A represents the outer area or
that part of the district where a scattered and smaller demand would not warrant
the heavy cost of low tension feeders direct from the central station; and which
area could only be economically worked by high tension feeders and transformers.
If now we connect the network in the outer area with that in the central area,
say at the points B and C as shown in the diagram, Figure 2, it will be obvious
that during the period of light load, probably eighteen or twenty hours out of the

page_text: twenty-four, sufficient current will be supplied to the outer area from the central
area network without any direct transmission through special feeders to the outer
area network; and that it is only during the period of heavy or comparatively
heavy load, say four to six hours out of the twenty-four, that the supply of current
to the outer area network will have to be supplemented by high tension feeders.
leading direct to the outer area.
My invention provides that as soon as the load becomes sufficiently heavy to.
necessitate the supply of current being supplemented, automatic connection with
high tension feeders is established as I shall now proceed to describe.
D, D, Figure 2, are step down alternating transformers the primaries P of which
are in circuit with the high tension feeders E, E, and the secondaries S of which
are connected or disconnected from the distributing mains F of the onter area by
the automatic switches G, G, diagrammatically represented by small circles. The
said automatic switches may be of any of the well known kinds operated by
variations either in the voltage or current. For instance, 1 may so arrange that
the coils of magnetically actuated switches being supplied with current by a shunt
from the distributing mains, as soon as the current traversing their coils is
insufficient to maintain the switch in its open position the said switch is closed as
for example by gravity or by a spring so as to complete the circuit between the
distributing main and the secondary coil S of the transformer or transformers.
Such automatic 'switches are well known in the art and need not be further
described here. As soon as the load on the distributing main or in other words
the demand for current, has increased and the voltage fallen to such an extent that
the shunted current traversing the switch coils no longer maintains the switch in
its open position the circuit is closed from the distributing main through the
secondary coils S of the transformer D; and now the transformer is converted for
the time being into a step up transformer its coil S becoming for the nonce a
primary and its coil P a secondary. A current is now induced in coil P which
traversing the feeder E gives an indication at the central station through any
convenient audible or visible indicating device so as to convey intelligence to the
attendant that it is time to switch on supplementary current from the central
station to the distributing mains of the outer area. The attendant then starts the
high tension alternators H, H, and when he has brought them into proper
synchronism with the low tension alternators J, J, as shown by the indicating
device just mentioned he switches the said high tension alternators on to the
feeders E, E, so that these supply high tension currents to the transformers D, D,
which, again becoming step down transformers, supply low tension current to the
distributing mains F, F. These distributing mains are now receiving sufficient low
tension current to cope with their load and the two sets of distributing mains in
the two areas are helping one another.
It will be obvious that instead of using the high tension feeders E to transmit
the indications as aforesaid the said indications may be transmitted over a special
indicating circuit or circuits extending between a point or points in the outer area
and the central station, an automatic switch of the type hereinbefore mentioned
being employed for the purpose of closing the said indicating circuit or circuits.
It is obvious that I may dispense with the low tension alternators J, J, at the
central station altogether in which case the low tension distributing mains of the
central area would be supplied by step down transformers at the central station.
At periods of light load the transformers D may be disconnected automatically
or by hand from the low tension distributing mains so as to absorb no energy
until the load is sufficient to require their use. Means for so automatically
disconnecting the transformers are well known in the art and need no further
description here.
I have hereinbefore spoken of the high tension feeders E being supplied with
current from high tension alternators H at the central station. It is obvious that
the said feeders may be supplied with high tension currents from step up
transformers K at the central station, the said step up transformers being supplied

page_text: with current from the low tension alternators J. L is an ordinary switch on the
high tension omnibus bar.
If desired, instead of feeding the network during the period of heavy load or
comparatively heavy load by means of the low tension feeders M, M, simultaneously
with the high tension feeders E, E, I may disconnect the low tension feeders after.
switching on the high tension feeders and supply current during the said period of
heavy or comparatively heavy load by means of the high tension feeders alone.
It will be seen that under my invention the distributing mains of the central area
and those of the outer area constitute a single distributing network.
Having now particularly described and ascertained the nature of my said inveu-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. The improvement in the distribution of electricity which consists in supplying
a single network during the period of light or comparatively light load with low
tension alternating currents fed direct from low tension feeders and during the
period of heavy or comparatively heavy load supplementing this supply with low
tension alternating currents from trausformers fed by high tension feeders substan-
tially as set forth.
2. The improvement in the distribution of electricity which consists in supplying
a single network during the period of light or comparatively light load with low
tension alternating currents fed direct from low tension feeders and during the
period of heavy or comparatively heavy load supplying the said network with low
tension alternating currents from transformers fed by high tension feeders the said
low tension feeders being disconnected during the said period of heavy or.
comparatively heavy load substantially as set forth.
3. The improvement in the distribution of electricity which consists in the
combination with a single network of distributing mains of both low tension feeders
and of high tension feeders with alternating current transformers substantially as
and for the purpose set forth.
DL3 1
1000