Improvements in Systems of Electrical Distribution and Measurement.
Year: 1899

page_text: Date of Application, 30th Oct., 1899-Accepted, 27th Jan., 1900
COMPLETE SPECIFICATION.
Improvements in Systems of Electrical Distribution and
Measurement.
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, 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:-
In alternating current systems of distribution for lighting purposes it is usually
impracticable to employ a net work owing to the comparatively long distances
between the installations of the various consumers. For this reason it is cus-
tomary to supply each consumer or group of consumers with a transformer of a
size corresponding to the maximum load which may be put upon it.
"
We find that even under the best conditions, the load on such transformers is
exceedingly variable, being practically nothing during the day time and seldom
reaching a maximum even in the evening. The core loss of the transformers
therefore forms a comparatively large percentage of the energy supplied and thus
makes the all day" efficiency of the installation very low. Various means have
been proposed for obviating the difficulties above mentioned, but so far as we are
aware they are open to serious objections, either from a commercial or an en-
gineering standpoint. In many cases the transformers are operated from sundown
to midnight and disconnected during the remainder of the day. This has the
obvious disadvantage that the circuits are dead at all other times than between
sundown and midnight. Automatic devices have also been used for cutting in and
cutting out transformers in various combinations unnecessary here to mention.
These are expensive, complicated and unreliable.
The present invention aims to reduce the core loss of transformer installations
without at the same time incurring the disadvantages above referred to, and
depends for its effectiveness upon the fact that in private dwelling houses stores.
and the like, by far the greatest number of lights or other translating devices is
needed in the evening, comparatively few lights being used during the day time.
We therefore divide the secondary wiring into two circuits, to one of which is
connected all of those lights which are ed only during the night time, and to the
other the lights which are used during the day time, or during the day and night
both. Each of these circuits is supplied from a transformer of a size corres-.
ponding to the maximum load on the circuit which it feeds. Instead of main-
taining the secondary circuits distinct from each other we find it convenient to
consolidate two of the mains into a single conductor which acts as a common
return for the currents carried by the two circuits, thus forming a species of
three wire system. which differs, however, from the ordinary Edison three wire
system, as generally used in that the current in the common return is the sum
and not the difference of the currents flowing in the outside mains. The primary
ID

page_text: windings of the transformers are similarly connected, the three mains being
carried back to the station. In one of the mains a switch is inserted so as
to cut out the night transformer during the interval between midnight and the
following sunset.
3.
According to the arrangement above described the night transformer is run at
a comparatively high efficiency, and is cut out of circuit while there is no call for
current, thus saving a large amount of energy which would otherwise be wasted
in the transformer. The other transformer which we term the "all day" trans-
former is maintained in circuit day and night and being of small size dissipates
but a small amount of energy, at the same time supplying the small demand for
ight in those places which require light both day and night, as for instance, in
cellars, vaults and other dimly lighted or unlightened places.
..
Our invention furthermore comprises a system of multiple. rate metering to be
used in connection with transformer installations of the character described,
but is also applicable as will be readily understood, to many other systems of
distributing electricity..
The details of our invention will be fully described in the following specification
while its scope will be clearly and particularly pointed out in the appended claims.
Fig. 1 illustrates diagramatically a system of distribution embodying this in-
vention.
Fig. 2 is. a modification of the same...
Refering to Fig. 1, G illustrates a source of alternating current, as for instance,
an alternating current generator. Three mains a, b, c, lead therefrom, the
mains a, b, being permanently connected to the terminals of the source G and the
main c to one of the terminals through a switch of any suitable form. The "all
day" transformer D) is connected across the mains a, b, while the night trans-
former is connected across the mains b, c. It will thus be observed that the "all
daytransformer D is always in circuit, while the night transformer N may be
cut in or out by operating the switch . The secondaries of the transformers D
and N are connected in series, with terminals of like polarity together. From
the common point between the secondaries and from the two remaining terminals
are lead the secondary mains A, B, C. Those lights or other translating devices
which are to be used only at night are connected between the secondary mains
of the night transformer N, while the lights which are to be used or may be used
at any time during the whole day of twenty-four hours, are connected between
the secondary mains of the all day transformer D. The current which flows in
the return conductor B is the sum of the currents supplied to the translating
devices at any one time.
It is generally possible to make the "all day" transformer of very small size,
thus saving an amount of energy almost equal to that which would be saved if a
single large transformer were used during the night time only, and cut out at other
times. In a transformer system of the character described it is obvious that the
circuit on a night transformer is inoperative during the day time. This would
ordinarily appear objectionable to the customer, and if no compensating advan-
tages were presented it would seem preferable to him that all lights or translating
devices should be placed on the circuit which is always alive, thus defeating any
attempted saving in core loss.
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We have therefore found it advisable, to charge for current on the "all day"
circuit at a higher rate than for current on the night circuit.
The additional expense incident to the use of translating devices on the all
day circuit will thus result in a reduction of the number of such devices to a
minimum, thus allowing the use of a smaller transformer for the "all day" cir-
cuit which is always operative and in which the transformer core loss is always
going on. At the same time a maximum number of translating devices is placed
on the night circuit thus saving an amount of energy corresponding to the loss
which would take place if the circuit were energized during the no-load hours.
The method. of charging above described is the direct opposite of the two-rate

page_text: system, now well known, in which current is charged for at a lower rate during
the day time when the station load is small, than during the night when it is high.
The objects to be obtained in the two systems of metering are different and there-
fore not inconsistent.
The system of metering devised by us, aims to prevent waste of energy in an
electrical distribution system, while the principal object sought for by the employ-
ment of a multiple rate system of the ordinary kind, is an equalization of load on
the system. In the two rate system already mentioned lower rates are charged
during the day as an inducement for the customer to use current at the time when
the load on the station is small. So far from being inconsistent are these systems
that we find it advisable to supply motor loads from the source of supply G during
the day time while the load on the station is small and to supply this current at a
reduced rate. In the drawings M illustrates a transformer supplying motors or
other translating devices and connected through a switch s with the source of
supply G. Owing to the reduced rate at which this current is supplied we find it
advisable in most instances that the circuit should be opened at night when the
motor load or demand for motor current is a minimum.
In connection with the system of distribution described and shown in the draw-
ings we have provided a system of multiple rate metering which automatically
records, according to the pre-determined rates, the amount of energy used in
both circuits.
In Fig. 1 we have shown an arrangement suitable for metering at different
rates, the energy expended in the "all day" circuit and the night circuit. For
this purpose a single recording watt meter W is employed, with its current coils E
connected in series with the common return B of the two circuits and its arma-
ture connected in shunt across the mains A B of the "all day" circuit, which, as
before explained are always energized. If the electromotice forces of the night cir-
cuit and of the "all day" circuit are equal it will be evident that the energy expended
in the two circuits will be metered at the same rate, since a given amount of
current flowing in the night circuit represents the same amount of energy as a
like flow of current in the "all day" circuit. In order therefore to cause the watt-
meter to register energy in the night circuit at a lower rate than in the all day
circuit we make the two circuits of different electromotive force, that of the night
circuit being higher than that of the "all day" circuit in proportion to the reduc-
tion of the rate desired. Thus if it be desired to charge for energy on the night
circuit at half the rate for that on the day circuit it is only necessary to make the
electromotive force on the night circuit twice that of the all day" circuit.
Under these conditions a given amount of current flowing in the night circuit
represents twice the expenditure of energy corresponding to the same amount of
current in the "all day" circuit.
The watt meter, which gives the same registration for the current in the common
return B, regardless from which circuit current is supplied, consequently registers
energy in the night circuit at half the rate that it registers energy in the "all
lay circuit, and this because of the fact that the speed of the meter is propor-
tional to the current in the field coil. Instead of the form of meter shown, any
other suitable form of meter may be employed.
In Fig. 2 we have shown a different arrangement for metering energy in the
night and in the "all day "circuits at different rates. In this case the two trans-
formers supplying the consumption circuits have the same ratio of transformation,
so as to give the same electro motive forces in the two circuits. A single watt-
hour meter W is employed as before, but the connections for the same are
differently made. The armature of the meter, as in the first instance is connected
across the mains A. B of the "all day" circuit.
One of these 'field coils F. or sets of field coils is connected in series with the
common return B, while the other field coil F is connected in series with the
main A of the "all day" circuit. As thus arranged will be evident that when
current flows in the "all day circuit it will pass through all of the field coils
"

page_text: of the meter, while when current flows in the night circuit, current will pass only
through those coils of the meter which are in series with the common return B.
If the turns of the two sets of field coils have an equal affect upon the armature
it will be evident that current in the "all day" circuit will be metered at a rate
twice that of the current in the night circuits. If it be desired to change the
relative rates of metering for the two circuits it is only necessary to change the
relative number of turns of the two sets of field coils connected respectively in
series with the common return B and the main A of the "all day" circuit. As
illustrating how this change may be made, we have shown in Fig. 2 the coil F¹
of the meter as provided with a plurality of terminals t so that by connecting
the main A to different terminals the number of effective turns of the coil Fi
may be varied.
The relative rates of metering in the two circuits are approximately in the
proportion of the total number of active field turns to the number of turns in the
common return alone. By suitably adjusting this relation of turns the respec-
tive rates of metering may be made anything desired.
By the employment of the above described system of distributing and metering
electricity, we have found that by far the largest part of the iron losses of the
transformers may be saved and since this loss constitutes a large percentage of the
station output, a considerable reduction in price may be made for those lights
which are operative only in the evening. Even with such a reduction in charges
the saving effected is generally more than sufficient to compensate for the expense
and inconvenience of an additional primary wire.
Although the system of metering which we have described above is particularly
useful in connection with alternating current systems of distribution already
described, it will, of course be evident, that it is in no respect limited thereto but
in its broader features is equally applicable to other systems of distributing alter-
nating currents, as well as to direct current distributing systems, and we intend
hereinafter to claim broadly to this system of metering regardless of the particular
nature of the system of distribution in connection with which it is employed.
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:
1. The method of metering the flow of electric energy in a plurality of electric
circuits, which consists in measuring at different rates and simultaneously
summing up the flow of energy in the individual circuits.
2. The method of metering the flow of electric energy in two electric circuits
which consists in measuring at different rates and simultaneously summing up the
flow of energy in the two circuits.
3. The method of metering the flow of electric energy in two interconnected
electric circuits, which consists in measuring at different rates and simultaneously
summing up the flow of energy in the two circuits.
4. The method of recording the consumption of electrical energy, which consists
in simultaneously recording at different rates the energy consumed in a plurality
of electric circuits.
5. The method of recording the consumption of electrical energy, which consists
in simultaneously recording at different rates the energy consumed in a plurality
of interconnected electric circuits.
6. The method of multiple rate metering, which consists in passing through a
single recording meter the currents from a plurality of circuits in which the
energy consumption is to be metered, and causing the meter to sum up and simul-
taneously record the consumption of energy according to different rates prede-
termined for the respective circuits.
7. The method of multiple rate metering, which consists in passing through a
single recording meter the currents from a plurality of interconnected circuits in
which the energy consumption is to be metered, and causing the meter to sum

page_text: up and simultaneously record the consumption of energy according to different
rates predetermined for the respective circuits.
8. The combination with a plurality of electric circuits provided with a
common return conductor, of a meter having a plurality of field coils less in
number than the total number of supply conductors, one of which field coils is
inserted in the common return.
9. The combination with a plurality of electric circuits provided with a common
return conductor, of a meter having a plurality of field coils less in number than
the total number of supply conductors, one of which field coils is inserted in the
common return, and the other coils respectively in other conductors of the supply
circuit.
10. The combination with three conductors one of which acts as a common
return for current flowing in the other two, of a recording meter provided with
two field coils one of which is connected in series with the common return and the
other in series with one of the other conductors.
11. The combination with three conductors one of which acts as a common
return for the other two, of means for maintaining substantially equal electro-
motive forces between the common return and the other two conductors respec-
tively, and an electric meter provided with two coils one of which is connected in
series with the common return and the other with one of. the remaining
conductors.
12. The combination with three conductors one of which acts as a common
return for the other two, of means for maintaining substantially equal electro-
motive forces between the common return and the other two conductors respec-
tively, an electric meter provided with two coils one of which is connected in
series with the common return and the other with one of the remaining conduc-
tors, and means for varying the ratio between the effective ampere turns of the
two field coils.
13. The combination with three conductors, one of which acts as a common
return for the other two, of means for maintaining substantially equal electro-
motive forces between the common return and the other two conductors respec-
tively, an electric meter provided with two coils one of which is connected in
series with the common return and the other with one of the remaining con-
ductors, and means for varying the number of turns of one of the field coils.
14. The combination with a plurality of electric circuits provided with a
common return conductor, of a meter having a plurality of field coils one of
which is inserted in the common return.
15. The combination with a plurality of electric circuits provided with a
common return conductor, of a meter having a plurality of field coils one of
which is inserted in the common return, and means for varying the ratio
between the effective ampere turns of the coils.
16. The combination with a plurality of electric circuits provided with a com-
mon return conductor, of a meter having a plurality of field coils one of which
is inserted in the common return, and means for varying the number of turns of
one of the coils.
17. The combination with a plurality of electric circuits provided with a
common return conductor, of a meter having a plurality of field coils one of
which is inserted in the common return, and means for varying the magnetizing
power of one of the coils.
18. In a system of distribution the combination of a plurality of supply cir-
cuits one of which is continuously supplied with energy and another of which is
supplied with energy periodically, and means for simultaneously recording at
different rates the energy consumed in the said circuits.
19. In a system of distribution, the combination of a plurality of supply
circuits one of which is continuously supplied with energy and another of which
is supplied with energy periodically, and means for recording at different rates the
flow of energy in the two circuits, the flow of energy in the continuously supplied

page_text: circuit being recorded at a higher rate than the corresponding record for the
periodically supplied circuit.
20. In a system of distribution, the combination of a plurality of supply cir-
cuits one of which is continuously supplied with energy and another of which is
supplied with energy periodically, and means for recording at different rates the
flow of energy in the two circuits.
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21. In a system of distribution, the combination of a plurality of transformers
one of which is continuously in circuit, and another of which is cut out during.
certain intervals, and means for simultaneously recording at different rates
the energy consumed in the permanently connected transformer circuit and the
periodically connected transformer circuit.
22. In a system of distribution the combination of a plurality of transformers
one of which is continually in circuit and another of which is periodically cut
out of circuit, and means for recording at different rates, the flow of energy
in the two transformer circuits, the flow of energy in the circuit of the per
manently connected transformer being recorded at a higher rate than the flow of
energy in the periodically connected transformer circuit.
23. In an alternating current system of distribution the combination of a
source of electrical energy, a plurality of transformers one of which is fed from
the source by permanently connected mains and another through a circuit which
may be interrupted at will, connections from one terminal of each secondary coil
to a common point and mains connected to the common point and to the free ter-
minals of the secondary. coils.
24. In an alternating current system of distribution, the combination of a
plurality of supply mains two of which are for carrying current of the same phase
or polarity, means for connecting or disconnecting one of the said two mains to
or from the source of supply, a plurality of transformers fed from the two mains
aforesaid operating in conjunction with other supply mains, and a connection. from
one terminal of each transformer secondary coil to a secondary main and connec-
tions from the other terminal of each coil to a common point.
25. In an alternating current system of distribution, the combination of a
plurality of supply mains two of which are for carrying current of the same phase
or polarity, means for connecting or disconnecting one of the said two mains to or
from the source of supply, a plurality of transformers fed from the two mains
aforesaid operating in conjunction with other supply mains, a connection from one
terminal of each transformer secondary coil to a secondary main connections from
the other terminal of each coil to a common point and an additional main, con-
nected to the common point.
26. In an alternating current system of distribution, the combination of supply
mains, a plurality of transformers with their primaries connected to the mains,
and their secondaries with one terminal of each connected to a common point and
with the electro-motive forces of the secondaries in opposition, and mains
leading from the common point and from the free terminals of the secondaries.
27. In an alternating current system of distribution the combination of supply
*mains, a plurality of transformers with their primaries connected to the mains, and
their secondaries with one terminal of each connected to a common point and
with the electro-motive forces of the secondaries in opposition, and means for
cutting out one of the transformers.
28. In an alternating current system of distribution, the combination of supply
mains, a plurality of transformers with their, primaries connected to the mains,
and their secondaries with one terminal of each connected to a common point and
with the electro-motive forces of the secondaries in opposition, and means for
interrupting at will the supply of energy, to one of the transformers.
29. The combination of a plurality of supply circuits, and means for metering
at different rates the energy consumed in the different circuits.
30: The combination of a plurality of circuits and means for metering the

page_text: energy consumed in one circuit at a rate different from that at which the
energy consumed in another of said circuits is metered.
31. The combination of a plurality of circuits and a single meter for metering
the energy consumed in one circuit at a rate different from that at which the
energy consumed in another of said circuits is metered.
32. The combination of a plurality of circuits and means for metering the
expenditure of energy in any number of said circuits, the energy expended in one
circuit being metered at a rate different from the rate of metering for another
circuit.
33. The combination of a plurality of circuits and means for simultaneously
metering the expenditure of energy in any number of said circuits, the energy
expended in one circuit being metered at a rate different from the rate of meter-
ing for another circuit.
THE BRITISH THOMSON-HOUSTON CO. LTD.,
J. J. MANHEIM,
A. R. MONKS,
Directors.
ALFRED CLEMENTS,
Assistant Secretary.