Improvements in Systems of Electrical Distribution.
Year: 1899

page_text: Date of Application, 22nd Nov., 1899-Accepted, 30th Dec., 1899
COMPLETE SPECIFICATION.
Improvements in Systems of Electrical Distribution.
We, THE BRITISH THOMSON-HOUSTON COMPANY LIMITED, of 83, Cannon Street,
in the City of London, Electrical Engineers, do hereby declare the nature of our
said invention (which has been communicated to us from abroad by Charles P.
Steinmetz, of Schenectady, in the County of Schenectady, State of New York,
United States of America, Electrical Engineer), and in what manner the same
is to be performed to be particularly described and ascertained in and by the
following statement:―
Our invention relates to alternating current systems of electrical distribution
and is more particularly of use in those systems in which the work circuits are
operated at comparatively low potentials, although it is not in any sense limited
in its application by the potentials employed.
In order to compensate for the resistance drop of potential in direct current
net works it is customary to use an, extensive system of feeders extending back
to, and conveying current from the power station. In low potential alternating
current systems it is obvious that the same system of feeders and mains as in a
direct current system, might be employed if desired. The expense and incon-
venience of extending feeders from the power station to distant points in the
net work is, however, one of the serious disadvantages met with in the employ-
ment of low tension currents for distribution over extended areas. It is one of
the objects of our invention to do away with the necessity for the use of extensive
and cumbersome feeder circuits in low tension alternating systems of electrical
distribution. In accomplishing the object stated we make use of the fact that
the potential in an inductive circuit may be made to rise if a source of leading
current or electro motive force be connected thereto. By suitably proportioning
and adjustment this rise of potential may be made to compensate exactly for the
drop of potential due to ohmic resistance or other causes. A constant potential
may thus be maintained.
In carrying out the invention in practice any suitable source of leading current
may be employed, though for the present purpose we find it convenient to use
synchronous motors with over-excited fields. These are preferably located in
proximity to those points in the net work which require to be raised in potential
to compensate for the drop in the mains. These sources of leading currents, or
phase modifiers, are connected by what we may term "suction feeders," with
points in the net work in the immediate vicinity and act to draw up the potential
at those points to the value desired. By the means described constant potential
regulation may be secured without the necessity of extending feeders back to
the source of supply.
The nature of this invention will be more apparent from the following
description taken in connection with the drawings and its scope will be particu-
larly pointed out in the appended claims.
The system to be described, is fed from any suitable source of alternating
currents. In the drawings, a stepdown transformer A is shown as serving this
purpose though it is obvious that a generator, rotary converter or other suitable

page_text: source might equally as well be employed so far as effecting the object of this
invention is concerned. The transformer A has the primary winding P fed from
the mains, a, b, while the secondary S is tapped at a point intermediate of its ends
and connected to a main d. The outer terminals of the secondary are connected
to mains c, e, thus forming, in conjunction with the main, a three wire system
which is intended to supply a net work of conductors of considerable extent.
In the drawings we have shown, for convenience, only a portion of the net
work. The mains e¹, d, e, and e², 2, 2 are connnected to the corresponding
wires of the three wire system and convey current to lamps Lor other translating
devices connected to the net work in the ordinary manner. Over-excited syn-
chronous motors are connected to the net work at suitable points and are located
at sub-stations more or less remote from the source of current supply. For
purposes of illustration we have shown two synchronous motors M¹, M² con-
nected to the mains e¹, d, e, and e², ², respectively. Leading from the
terminals of the motors are feeders F which connect with points in the net
work in proximity thereto.
;
The employment of the means shown obviates the necessity for carrying
feeders back to the main station. In accordance with the. present invention
feeders are led from points in the net work back only to the nearest sub-station
containing only a synchronous motor with over-excited fields, as has been
explained.
The self induction of the mains, acting in conjunction with the leading electro
motive force derived from the over-excited synchronous motors, will frequently
be sufficient to cause the desired rise of potential to compensate for drop. If
the self induction of the mains is insufficient for this purpose it is necessary to
introduce an artificial self induction and this may be done by coiling the mains
or the feeders from distance to distance, as illustrated for example at N; Orand P
in the drawings, or if desired inductance coils with iron cores may be employed
as indicated at N, O and P' in dotted lines.
If the synchronous motors MI and M2 be built with very low self induction
they will, even without regulation, exert a powerful equalizing influence tending
towards the maintenance of a constant potential. If closer regulation for con-
stant potential is desired the motors may be regulated by means responsive
to changes of potential of the mains. Inasmuch as the specific means for regu-
lating the motors forms no essential part of the present invention it is considered
unnecessary to illustrate or further describe the same.
Although the invention has been shown as applied to a three wire system it
will of course be understood that it is in no way limited thereto for it is equally
applicable to any system employing alternating or variable currents of electricity,
whether the same be single phase or multiphase.
Instead of synchronous motors of the ordinary type in which a separately
excited field is used we may, if desired use self exciting machines such as rotary
converters since either type of machine is applicable for the purposes of this
invention. The direct current produced by the rotary converters may be employed
solely for purposes of field excitation or may in addition he distributed to
translating devices as may be found desirable.
.
Having now particularly described and ascertained the nature of our said
invention (as communicated to us from abroad) and in what manner the same is
to be performed we declare that what we claim is:
יד
1- The combination of a phase advancing device connected to an inductive
supply circuit and feeders leading from said phase advancing device.
The combination of mains, a phase advancing device connected to" said
mains, and feeders leading from said phase advancing device.
г
The combination of a work circuit, a phase advancing device connected
thereto, and feeders leading from said phase advancing device to said work
circuit,

page_text: 4 The combination of a work circuit, an artificial inductance in said work
circuit, means for supplying current through said inductance to a phase advancing
device, and feeders leading from said phase advancing device to points in said
work circuit.
5-The combination with a three wire system of distribution, of a phase
advancing device in connection therewith and feeders leading from said phase
advancing device.
6-The combination of a source of alternating currents an interconnected
system of distributing conductors connected thereto, phase advancing devices
located at sub-stations and connected to points in the system, and " suction
feeders" leading from said phase advancing devices and connected to other points
in the system.
7 The method of distribution which consists in taking a current from a
system at one point and returning a leading current derived therefrom to another
point in the system.
8-The method of distribution which consists in passing current from one
part of an inductive circuit through a phase advancing device, and impressing
the electromotive force at the terminals of the phase advancing device upon
another part of the circuit.
9 The method of distribution which consists in passing current from an
inductive line through a phase advancing device and impressing the electro-
motive force at the terminals of the phase advancing device on parts of the line
having an electromotive force lower than that at the terminals of said phase
advancing device.
11
1
1
1000
THE BRITISH THOMSON-HOUSTON CO. LTD.
ALFRED CLEMENTS,
Assistant Secretary.
W. MARTINDALE, Directors.
A. H. MONKS,