Generating stations.
The general arrangements of a low-pressure supply station are shown in
figs. 3 and 4. It consists of a boiler-house containing a bank of
boilers, either Lancashire or Babcock & Wilcox being generally used (see
BOILER), which furnish steam to the engines and dynamos, provision
being made by duplicate steam-pipes or a ring main so that the failure
of a single engine or dynamo does not cripple the whole supply. The
furnace gases are taken through an economizer (generally Green's) so
that they give up their heat to the cold feed water. If condensing water
is available the engines are worked condensing, and this is an essential
condition of economy when steam turbines are employed. Hence, either a
condensing water pond or a cooling tower has to be provided to cool the
condensing water and enable it to be used over and over again.
Preferably the station should be situated near a river or canal and a
railway siding. The steam dynamos are generally arranged in an
engine-room so as to be overlooked from a switchboard gallery (fig. 3),
from which all the control is carried out. The boiler furnaces are
usually stoked by automatic stokers. Owing to the relatively small load
factor (say 8 or 10%) of a station giving electric supply for lighting
only, the object of every station engineer is to cultivate a demand for
electric current for power during the day-time by encouraging the use of
electric motors for lifts and other purposes, but above all to create a
demand for traction purposes. Hence most urban stations now supply
current not only for electric lighting but for running the town tramway
system, and this traction load being chiefly a daylight load serves to
keep the plant employed and remunerative. It is usual to furnish a
continuous current supply for traction at 500 or 600 volts, although
some station engineers are advocating the use of higher voltages. In
those stations which supply current for traction, but which have a
widely scattered lighting load, _double current_ dynamos are often
employed, furnishing from one and the same armature a continuous current
for traction purposes, and an alternating current for lighting purposes.
High-pressure continuous supply.
In some places a high voltage system of electric supply by continuous
current is adopted. In this case the current is generated at a pressure
of 1000 or 2000 volts, and transmitted from the generating station by
conductors, called high-pressure feeders, to certain sub-centres or
transformer centres, which are either buildings above ground or cellars
or excavations under the ground. In these transformer centres are placed
machines, called _continuous-current transformers_, which transform the
electric energy and create a secondary electric current at a lower
pressure, perhaps 100 or 150 volts, to be supplied by distributing mains
to users (see TRANSFORMERS). From these sub-centres insulated conductors
are run back to the generating station, by which the engineer can start
or stop the continuous-current rotatory transformers, and at the same
time inform himself as to their proper action and the electromotive
force at the secondary terminals. This system was first put in practice
in Oxford, England, and hence has been sometimes called by British
engineers "the Oxford system." It is now in operation in a number of
places in England, such as Wolverhampton, Walsall, and Shoreditch in
London. It has the advantage that in connexion with the low-pressure
distributing system secondary batteries can be employed, so that a
storage of electric energy is effected. Further, continuous-current arc
lamps can be worked in series off the high-pressure mains, that is to
say, sets of 20 to 40 arc lamps can be operated for the purpose of
street lighting by means of the high-pressure continuous current.
Alternating supply.
The alternating current systems in operation at the present time are the
_single-phase_ system, with distributing transformers or transformer
sub-centres, and the _polyphase_ systems, in which the alternating
current is transformed down into an alternating current of low pressure,
or, by means of rotatory transformers, into a continuous current. The
general arrangement of a _single-phase_ alternating-current system is as
follows: The generating station contains a number of alternators, A1 A2
(fig. 5), producing single-phase alternating current, either at 1000,
2000, or sometimes, as at Deptford and other places, 10,000 volts. This
current is distributed from the station either at the pressure at which
it is generated, or after being transformed up to a higher pressure by
the transformer T. The alternators are sometimes worked in parallel,
that is to say, all furnish their current to two common omnibus bars on
a high-pressure switchboard, and each is switched into circuit at the
moment when it is brought into step with the other machines, as shown by
some form of _phase-indicator_. In some cases, instead of the
high-pressure feeders starting from omnibus bars, each alternator works
independently and the feeders are grouped together on the various
alternators as required. A number of high-pressure feeders are carried
from the main switchboard to various transformer sub-centres or else run
throughout the district to which current is to be furnished. If the
system laid down is the transformer sub-centre system, then at each of
these sub-centres is placed a battery of alternating-current
transformers, T1 T2 T3, having their primary circuits all joined in
parallel to the terminals of the high-pressure feeders, and their
secondary circuits all joined in parallel on a distributing main,
suitable switches and cut-outs being interposed. The pressure of the
current is then transformed down by these transformers to the required
supply pressure. The secondary circuits of these transformers are
generally provided with three terminals, so as to supply the
low-pressure side on a three-wire system. It is not advisable to connect
together directly the secondary circuits of all the different
sub-centres, because then a fault or short circuit on one secondary
system affects all the others. In banking together transformers in this
manner in a sub-station it is necessary to take care that the
transformation ratio and secondary drop (see TRANSFORMERS) are exactly
the same, otherwise one transformer will take more than its full share
of the load and will become overheated. The transformer sub-station
system can only be adopted where the area of supply is tolerably
compact. Where the consumers lie scattered over a large area, it is
necessary to carry the high-pressure mains throughout the area, and to
place a separate transformer or transformers in each building. From a
financial point of view, this "house-to-house system" of
alternating-current supply, generally speaking, is less satisfactory in
results than the transformer sub-centre system. In the latter some of
the transformers can be switched off, either by hand or by automatic
apparatus, during the time when the load is light, and then no power is
expended in magnetizing their cores. But with the house-to-house system
the whole of the transformers continually remain connected with the
high-pressure circuits; hence in the case of supply stations which have
only an ordinary electric lighting load, and therefore a load-factor not
above 10%, the efficiency of distribution is considerably diminished.
[Illustration: FIG. 5.]
The single-phase alternating-current system is defective in that it
cannot be readily combined with secondary batteries for the storage of
electric energy. Hence in many places preference is now given to the
_polyphase system_. In such a system a polyphase alternating current,
either two- or three-phase, is transmitted from the generating station
at a pressure of 5000 to 10,000 volts, or sometimes higher, and at
various sub-stations is transformed down, first by static transformers
into an alternating current of lower pressure, say 500 volts, and then
by means of rotatory transformers into a continuous current of 500
volts or lower for use for lighting or traction.
In the case of large cities such as London, New York, Chicago, Berlin
and Paris the use of small supply stations situated in the interior of
the city has gradually given way to the establishment of large supply
stations outside the area; in these alternating current is generated on
the single or polyphase system at a high voltage and transmitted by
underground cables to sub-stations in the city, at which it is
transformed down for distribution for private and public electric
lighting and for urban electric traction.
Owing to the high relative cost of electric power when generated in
small amounts and the great advantages of generating it in proximity to
coal mines and waterfalls, the supply of electric power in bulk to small
towns and manufacturing districts has become a great feature in modern
electrical engineering. In Great Britain, where there is little useful
water power but abundance of coal, electric supply stations for supply
in bulk have been built in the coal-producing districts of South Wales,
the Midlands, the Clyde valley and Yorkshire. In these cases the current
is a polyphase current generated at a high voltage, 5000 to 10,000
volts, and sometimes raised again in pressure to 20,000 or 40,000 volts
and transmitted by overhead lines to the districts to be supplied. It is
there reduced in voltage by transformers and employed as an alternating
current, or is used to drive polyphase motors coupled to direct current
generators to reproduce the power in continuous current form. It is then
distributed for local lighting, street or railway traction, driving
motors, and metallurgical or electrochemical applications. Experience
has shown that it is quite feasible to distribute in all directions for
25 miles round a high-pressure generating station, which thus supplies
an area of nearly 2000 sq. m. At such stations, employing large turbine
engines and alternators, electric power may be generated at a works cost
of 0.375d. per kilowatt (K.W.), the coal cost being less than 0.125d.
per K.W., and the selling price to large load-factor users not more than
0.5d. per K.W. The average price of supply from the local generating
stations in towns and cities is from 3d. to 4d. per unit, electric
energy for power and heating being charged at a lower rate than that for
lighting only.
Conductors.
We have next to consider the structure and the arrangement of the
conductors employed to convey the currents from their place of creation
to that of utilization. The conductors themselves for the most part
consist of copper having a conductivity of not less than 98% according
to Matthiessen's standard. They are distinguished as (1) _External
conductors_, which are a part of the public supply and belong to the
corporation or company supplying the electricity; (2) _Internal
conductors_, or house wiring, forming a part of the structure of the
house or building supplied and usually the property of its owner.
External conductors.
The external conductors may be overhead or underground. _Overhead_
conductors may consist of bare stranded copper cables carried on
porcelain insulators mounted on stout iron or wooden poles. If the
current is a high-pressure one, these insulators must be carefully
tested, and are preferably of the pattern known as oil insulators. In
and near towns it is necessary to employ insulated overhead conductors,
generally india-rubber-covered stranded copper cables, suspended by
leather loops from steel bearer wires which take the weight. The British
Board of Trade have issued elaborate rules for the construction of
overhead lines to transmit large electric currents. Where telephone and
telegraph wires pass over such overhead electric lighting wires, they
have to be protected from falling on the latter by means of guard wires.
By far the largest part, however, of the external electric distribution
is now carried out by _underground conductors_, which are either bare or
insulated. Bare copper conductors may be carried underground in culverts
or chases, air being in this case the insulating material, as in the
overhead system. A culvert and covered chase is constructed under the
road or side-walk, and properly shaped oak crossbars are placed in it
carrying glass or porcelain insulators, on which stranded copper
cables, or, preferably, copper strips placed edgeways, are stretched and
supported. The advantages of this method of construction are cheapness
and the ease with which connexions can be made with service-lines for
house supply; the disadvantages are the somewhat large space in which
coal-gas leaking out of gas-pipes can accumulate, and the difficulty of
keeping the culverts at all times free from rain-water. Moisture has a
tendency to collect on the negative insulators, and hence to make a dead
earth on the negative side of the main; while unless the culverts are
well ventilated, explosions from mixtures of coal-gas and air are liable
to occur. Insulated cables are insulated either with a material which is
in itself waterproof, or with one which is only waterproof in so far as
it is enclosed in a waterproof tube, e.g. of lead. Gutta-percha and
india-rubber are examples of materials of the former kind. Gutta-percha,
although practically everlasting when in darkness and laid under water,
as in the case of submarine cables, has not been found satisfactory for
use with large systems of electric distribution, although much employed
for telephone and telegraph work. Insulated underground external
conductors are of three types:--(a) _Insulated Cables drawn into
Pipes._--In this system of distribution cast-iron or stoneware pipes, or
special stoneware conduits, or conduits made of a material called
bitumen concrete, are first laid underground in the street. These
contain a number of holes or "ways," and at intervals drawing-in boxes
are placed which consist of a brick or cast-iron box having a
water-tight lid, by means of which access is gained to a certain section
of the conduit. Wires are used to draw in the cables, which are covered
with either india-rubber or lead, the copper being insulated by means of
paper, impregnated jute, or other similar material. The advantages of a
drawing-in system are that spare ways can be left when the conduits are
put in, so that at a future time fresh cables can be added without
breaking up the roadway. (b) _Cables in Bitumen._--One of the earliest
systems of distribution employed by T.A. Edison consisted in fixing two
segment-shaped copper conductors in a steel tube, the interspace between
the conductors and the tube being filled in with a bitumen compound. A
later plan is to lay down an iron trough, in which the cables are
supported by wooden bearers at proper distances, and fill in the whole
with natural bitumen. This system has been carried out extensively by
the Callendar Cable Company. Occasionally concentric lead-covered and
armoured cables are laid in this way, and then form an expensive but
highly efficient form of insulated conductor. In selecting a system of
distribution regard must be paid to the nature of the soil in which the
cables are laid. Lead is easily attacked by soft water, although under
some conditions it is apparently exceedingly durable, and an atmosphere
containing coal-gas is injurious to india-rubber. (c) _Armoured
Cables._--In a very extensively used system of distribution armoured
cables are employed. In this case the copper conductors, two, three or
more in number, may be twisted together or arranged concentrically, and
insulated by means of specially prepared jute or paper insulation,
overlaid with a continuous tube of lead. Over the lead, but separated by
a hemp covering, is put a steel armour consisting of two layers of steel
strip, wound in opposite directions and kept in place by an external
covering. Such a cable can be laid directly in the ground without any
preparation other than the excavation of a simple trench, junction-boxes
being inserted at intervals to allow of branch cables being taken off.
The armoured cable used is generally of the concentric pattern (fig. 6).
It consists of a stranded copper cable composed of a number of wires
twisted together and overlaid with an insulating material. Outside this
a tubular arrangement of copper wires and a second layer of insulation,
and finally a protective covering of lead and steel wires or armour are
placed. In some cases three concentric cylindrical conductors are formed
by twisting wires or copper strips with insulating material between. In
others two or three cables of stranded copper are embedded in insulating
material and included in a lead sheath. This last type of cable is
usually called a _two-_ or _three-core_ pattern cable (fig. 7).
[Illustration: FIG. 6.--Armoured Concentric Cable (Section).
IC, Inner conductor.
OC, Outer conductor.
I, Insulation.
L, Lead sheath.
S, Steel armour.
H, Hemp covering.]
[Illustration: FIG. 7.--Triple Conductor Armoured Cable (Section).
C, Copper conductor.
I, Insulation.
L, Lead sheath.
H, Hemp covering.
S, Steel armour.]
The arrangement and nature of the external conductors depends on the
system of electric supply in which they are used. In the case of
continuous-current supply for incandescent electric lighting and motive
power in small units, when the external conductors are laid down on the
three-wire system, each main or branch cable in the street consists of a
set of three conductors called the positive, middle and negative. Of
these triple conductors some run from the supply station to various
points in the area of supply without being tapped, and are called the
_feeders_; others, called the _distributing mains_, are used for making
connexions with the service lines of the consumers, one service line, as
already explained, being connected to the middle conductor, and the
other to either the positive or the negative one. Since the middle
conductor serves to convey only the difference between the currents
being used on the two sides of the system, it is smaller in section than
the positive and negative ones. In laying out the system great judgment
has to be exercised as to the selection of the points of attachment of
the feeders to the distributing mains, the object being to keep a
constant electric pressure or voltage between the two service-lines in
all the houses independently of the varying demand for current. Legally
the suppliers are under regulations to keep the supply voltage constant
within 4% either way above or below the standard pressure. As a matter
of fact very few stations do maintain such good regulation. Hence a
considerable variation in the light given by the incandescent lamps is
observed, since the candle-power of carbon glow lamps varies as the
fifth or sixth power of the voltage of supply, i.e. a variation of only
2% in the supply pressure affects the resulting candle-power of the
lamps to the extent of 10 or 12%. This variation is, however, less in
the case of metallic filament lamps (see LIGHTING: _Electric_). In the
service-lines are inserted the meters for measuring the electric energy
supplied to the customer (see METER, ELECTRIC).
Interior wiring.
In the interior of houses and buildings the conductors generally consist
of india-rubber-covered cables laid in wood casing. The copper wire must
be tinned and then covered, first with a layer of unvulcanized pure
india-rubber, then with a layer of vulcanized rubber, and lastly with
one or more layers of protective cotton twist or tape. No conductor of
this character employed for interior house-wiring should have a smaller
insulation resistance than 300 megohms per mile when tested with a
pressure of 600 volts after soaking 24 hours in water. The wood casing
should, if placed in damp positions or under plaster, be well varnished
with waterproof varnish. As far as possible all joints in the run of the
cable should be avoided by the use of the so-called looping-in system,
and after the wiring is complete, careful tests for insulation should be
made. The Institution of Electrical Engineers of Great Britain have
drawn up rules to be followed in interior house-wiring, and the
principal Fire Insurance offices, following the lead of the Phoenix Fire
Office, of London, have made regulations which, if followed, are a
safeguard against bad workmanship and resulting possibility of damage by
fire. Where fires having an electric origin have taken place, they have
invariably been traced to some breach of these rules. Opinions differ,
however, as to the value and security of this method of laying interior
conductors in buildings, and two or three alternative systems have been
much employed. In one of these, called the _interior conduit_ system,
highly insulating waterproof and practically fireproof tubes or conduits
replace the wooden casing; these, being either of plain insulating
material, or covered with brass or steel armour, may be placed under
plaster or against walls. They are connected by bends or joint-boxes.
The insulated wires being drawn into them, any short circuit or heating
of the wire cannot give rise to a fire, as it can only take place in the
interior of a non-inflammable tube. A third system of electric light
wiring is the safety concentric system, in which concentric conductors
are used. The inner one, which is well insulated, consists of a
copper-stranded cable. The outer may be a galvanized iron strand, a
copper tape or braid, or a brass tube, and is therefore necessarily
connected with the earth. A fourth system consists in the employment of
twin insulated wires twisted together and sheathed with a lead tube; the
conductor thus formed can be fastened by staples against walls, or laid
under plaster or floors.
The general arrangement for distributing current to the different
portions of a building for the purpose of electric lighting is to run up
one or more rising mains, from which branches are taken off to
distributing boxes on each floor, and from these boxes to carry various
branch circuits to the lamps. At the distributing boxes are collected
the cut-outs and switches controlling the various circuits. When
alternating currents are employed, it is usual to select as a type of
conductor either twin-twisted conductor or concentric; and the
employment of these types of cable, rather than two separate cables, is
essential in any case where there are telephone or telegraph wires in
proximity, for otherwise the alternating current would create inductive
disturbances in the telephone circuit. The house-wiring also comprises
the details of _switches_ for controlling the lamps, _cut-outs_ or fuses
for preventing an excess of current passing, and fixtures or supports
for lamps often of an ornamental character. For the details of these,
special treatises on electric interior wiring must be consulted.
For further information the reader may be referred to the following
books:--C.H. Wordingham, _Central Electrical Stations_ (London, 1901);
A. Gay and C.Y. Yeaman, _Central Station Electricity Supply_ (London,
1906); S.P. Thompson, _Dynamo Electric Machinery_ (2 vols., London,
1905); E. Tremlett Carter and T. Davies, _Motive Power and Gearing_
(London, 1906); W.C. Clinton, _Electric Wiring_ (2nd ed., London,
1906); W. Perren Maycock, _Electric Wiring, Fitting, Switches and
Lamps_ (London, 1899); D. Salomons, _Electric Light Installations_
(London, 1894); Stuart A. Russell, _Electric Light Cables_ (London,
1901); F.A.C. Perrine, _Conductors for Electrical Distribution_
(London, 1903); E. Rosenberg, W.W. Haldane Gee and C. Kinzbrunner,
_Electrical Engineering_ (London, 1903); E.C. Metcalfe, _Practical
Electric Wiring for Lighting Installations_ (London, 1905); F.C.
Raphael, _The Wireman's Pocket Book_ (London, 1903). (J. A. F.)
History.
II. _Commercial Aspects._--To enable the public supply enterprises
referred to in the foregoing section to be carried out in England,
statutory powers became necessary to break up the streets. In the early
days a few small stations were established for the supply of electricity
within "block" buildings, or by means of overhead wires within
restricted areas, but the limitations proved uneconomical and the
installations were for the most part merged into larger undertakings
sanctioned by parliamentary powers. In the year 1879 the British
government had its attention directed for the first time to electric
lighting as a possible subject for legislation, and the consideration of
the then existing state of electric lighting was referred to a select
committee of the House of Commons. No legislative action, however, was
taken at that time. In fact the invention of the incandescent lamp was
incomplete--Edison's British master-patent was only filed in Great
Britain in November 1879. In 1881 and 1882 electrical exhibitions were
held in Paris and at the Crystal Palace, London, where the improved
electric incandescent lamp was brought before the general public. In
1882 parliament passed the first Electric Lighting Act, and considerable
speculation ensued. The aggregate capital of the companies registered in
1882-1883 to carry out the public supply of electricity in the United
Kingdom amounted to L15,000,000, but the onerous conditions of the act
deterred investors from proceeding with the enterprise. Not one of the
sixty-two provisional orders granted to companies in 1883 under the act
was carried out. In 1884 the Board of Trade received only four
applications for provisional orders, and during the subsequent four
years only one order was granted. Capitalists declined to go on with a
business which if successful could be taken away from them by local
authorities at the end of twenty-one years upon terms of paying only the
then value of the plant, lands and buildings, without regard to past or
future profits, goodwill or other considerations. The electrical
industry in Great Britain ripened at a time when public opinion was
averse to the creation of further monopolies, the general belief being
that railway, water and gas companies had in the past received valuable
concessions on terms which did not sufficiently safeguard the interests
of the community. The great development of industries by means of
private enterprise in the early part of the 19th century produced a
reaction which in the latter part of the century had the effect of
discouraging the creation by private enterprise of undertakings
partaking of the nature of monopolies; and at the same time efforts were
made to strengthen local and municipal institutions by investing them
with wider functions. There were no fixed principles governing the
relations between the state or municipal authorities and commercial
companies rendering monopoly services. The new conditions imposed on
private enterprise for the purpose of safeguarding the interests of the
public were very tentative, and a former permanent secretary of the
Board of Trade has stated that the efforts made by parliament in these
directions have sometimes proved injurious alike to the public and to
investors. One of these tentative measures was the Tramways Act 1870,
and twelve years later it was followed by the first Electric Lighting
Act.
It was several years before parliament recognized the harm that had been
done by the passing of the Electric Lighting Act 1882. A select
committee of the House of Lords sat in 1886 to consider the question of
reform, and as a result the Electric Lighting Act 1888 was passed. This
amending act altered the period of purchase from twenty-one to forty-two
years, but the terms of purchase were not materially altered in favour
of investors. The act, while stipulating for the consent of local
authorities to the granting of provisional orders, gives the Board of
Trade power in exceptional cases to dispense with the consent, but this
power has been used very sparingly. The right of vetoing an undertaking,
conferred on local authorities by the Electric Lighting Acts and also by
the Tramways Act 1870, has frequently been made use of to exact unduly
onerous conditions from promoters, and has been the subject of complaint
for years. Although, in the opinion of ministers of the Crown, the
exercise of the veto by local authorities has on several occasions led
to considerable scandals, no government has so far been able, owing to
the very great power possessed by local authorities, to modify the law
in this respect. After 1888 electric lighting went ahead in Great
Britain for the first time, although other countries where legislation
was different had long previously enjoyed its benefits. The developments
proceeded along three well-defined lines. In London, where none of the
gas undertakings was in the hands of local authorities, many of the
districts were allotted to companies, and competition was permitted
between two and sometimes three companies. In the provinces the cities
and larger towns were held by the municipalities, while the smaller
towns, in cases where consents could be obtained, were left to the
enterprise of companies. Where consents could not be obtained these
towns were for some time left without supply.
Some statistics showing the position of the electricity supply
business respectively in 1896 and 1906 are interesting as indicating
the progress made and as a means of comparison between these two
periods of the state of the industry as a whole. In 1896 thirty-eight
companies were at work with an aggregate capital of about L6,000,000,
and thirty-three municipalities with electric lighting loans of nearly
L2,000,000. The figures for 1906, ten years later, show that 187
electricity supply companies were in operation with a total investment
of close on L32,000,000, and 277 municipalities with loans amounting
to close on L36,000,000. The average return on the capital invested in
the companies at the later period was 5.1% per annum. In 1896 the
average capital expenditure was about L100 per kilowatt of plant
installed; and L50 per kilowatt was regarded as a very low record. For
1906 the average capital expenditure per kilowatt installed was about
L81. The main divisions of the average expenditure are:--
1896. 1906.
Land and buildings 22.3% 17.8%
Plant and machinery 36.7 36.5
Mains 32.2 35.5
Meters and instruments 4.6 5.7
Provisional orders, &c. 3.2 2.8
The load connected, expressed in equivalents of eight candle-power
lamps, was 2,000,000 in 1896 and 24,000,000 in 1906. About one-third
of this load would be for power purposes and about two-thirds for
lighting. The Board of Trade units sold were 30,200,000 in 1896 and
533,600,000 in 1906, and the average prices per unit obtained were
5.7d. and 2.7d. respectively, or a revenue of L717,250 in 1896 and
over L6,000,000 in 1906. The working expenses per Board of Trade unit
sold, excluding depreciation, sinking fund and interest were as
follows:--
1896. 1906.
Generation and distribution 2.81d. .99d.
Rent, rates and taxes .35 .14
Management .81 .18
Sundries .10 .02
------ ------
Total 4.07d. 1.33d.
In 1896 the greatest output at one station was about 5-1/2 million
units, while in 1906 the station at Manchester had the largest output
of over 40 million units.
The capacity of the plants installed in the United Kingdom in 1906
was:--
K.W.
Continuous current 417,000 / Provinces 333,000
\ London 84,000
Alternating current 132,000 / Provinces 83,000
\ London 49,000
Continuous current and \
alternating current > 480,000 / Provinces 366,000
combined / \ London 114,000
---------
1,029,000 k.w.
Economics.
The economics of electric lighting were at first assumed to be similar
to those of gas lighting. Experience, however, soon proved that there
were important differences, one being that gas may be stored in
gasometers without appreciable loss and the work of production carried
on steadily without reference to fluctuations of demand. Electricity
cannot be economically stored to the same extent, and for the most part
it has to be used as it is generated. The demand for electric light is
practically confined to the hours between sunset and midnight, and it
rises sharply to a "peak" during this period. Consequently the
generating station has to be equipped with plant of sufficient capacity
to cope with the maximum load, although the peak does not persist for
many minutes--a condition which is very uneconomical both as regards
capital expenditure and working costs (see LIGHTING: _Electric_). In
order to obviate the unproductiveness of the generating plant during the
greater part of the day, electricity supply undertakings sought to
develop the "daylight" load. This they did by supplying electricity for
traction purposes, but more particularly for industrial power purposes.
The difficulties in the way of this line of development, however, were
that electric power could not be supplied cheaply enough to compete with
steam, hydraulic, gas and other forms of power, unless it was generated
on a very large scale, and this large demand could not be developed
within the restricted areas for which provisional orders were granted
and under the restrictive conditions of these orders in regard to
situation of power-house and other matters.
The leading factors which make for economy in electricity supply are the
magnitude of the output, the load factor, and the diversity factor,
also the situation of the power house, the means of distribution, and
the provision of suitable, trustworthy and efficient plant. These
factors become more favourable the larger the area and the greater and
more varied the demand to be supplied. Generally speaking, as the output
increases so the cost per unit diminishes, but the ratio (called the
load factor) which the output during any given period bears to the
_maximum_ possible output during the same period has a very important
influence on costs. The ideal condition would be when a power station is
working at its normal _maximum_ output continuously night and day. This
would give a load-factor of 100%, and represents the ultimate ideal
towards which the electrical engineer strives by increasing the area of
his operations and consequently also the load and the variety of the
overlapping demands. It is only by combining a large number of demands
which fluctuate at different times--that is by achieving a high
diversity factor--that the supplier of electricity can hope to approach
the ideal of continuous and steady output. Owing to the dovetailing of
miscellaneous demands the actual demand on a power station at any moment
is never anything like the aggregate of all the maximum demands. One
large station would require a plant of 36,000 k.w. capacity if all the
demands came upon the station simultaneously, but the maximum demand on
the generating plant is only 15,000 kilowatts. The difference between
these two figures may be taken to represent the economy effected by
combining a large number of demands on one station. In short, the
keynote of progress in cheap electricity is increased and diversified
demand combined with concentration of load. The average load-factor of
all the British electricity stations in 1907 was 14.5%--a figure which
tends to improve.
Power companies.
Several electric power supply companies have been established in the
United Kingdom to give practical effect to these principles. The
Electric Lighting Acts, however, do not provide for the establishment of
large power companies, and special acts of parliament have had to be
promoted to authorize these undertakings. In 1898 several bills were
introduced in parliament for these purposes. They were referred to a
joint committee of both Houses of Parliament presided over by Lord
Cross. The committee concluded that, where sufficient public advantages
are shown, powers should be given for the supply of electricity over
areas including the districts of several local authorities and involving
the use of exceptional plant; that the usual conditions of purchase of
the undertakings by the local authorities did not apply to such
undertakings; that the period of forty-two years was "none too long" a
tenure; and that the terms of purchase should be reconsidered. With
regard to the provision of the Electric Lighting Acts which requires
that the consent of the local authority should be obtained as a
condition precedent to the granting of a provisional order, the
committee was of opinion that the local authority should be entitled to
be heard by the Board of Trade, but should not have the power of veto.
No general legislation took place as a result of these recommendations,
but the undermentioned special acts constituting power supply companies
were passed.
In 1902 the president of the Board of Trade stated that a bill had been
drafted which he thought "would go far to meet all the reasonable
objections that had been urged against the present powers by the local
authorities." In 1904 the government introduced the Supply of
Electricity Bill, which provided for the removal of some of the minor
anomalies in the law relating to electricity. The bill passed through
all its stages in the House of Lords but was not proceeded with in the
House of Commons. In 1905 the bill was again presented to parliament but
allowed to lie on the table. In the words of the president of the Board
of Trade, there was "difficulty of dealing with this question so long as
local authorities took so strong a view as to the power which ought to
be reserved to them in connexion with this enterprise." In the official
language of the council of the Institution of Electrical Engineers, the
development of electrical science in the United Kingdom is in a backward
condition as compared with other countries in respect of the practical
application to the industrial and social requirements of the nation,
notwithstanding that Englishmen have been among the first in inventive
genius. The cause of such backwardness is largely due to the conditions
under which the electrical industry has been carried on in the country,
and especially to the restrictive character of the legislation governing
the initiation and development of electrical power and traction
undertakings, and to the powers of obstruction granted to local
authorities. Eventually The Electric Lighting Act 1909 was passed. This
Act provides:--(1) for the granting of provisional orders authorizing
any local authority or company to supply electricity in bulk; (2) for
the exercise of electric lighting powers by local authorities jointly
under provisional order; (3) for the supply of electricity to railways,
canals and tramways outside the area of supply with the consent of the
Board of Trade; (4) for the compulsory acquisition of land for
generating stations by provisional order; (5) for the exemption of
agreements for the supply of electricity from stamp duty; and (6) for
the amendment of regulations relating to July notices, revision of
maximum price, certification of meters, transfer of powers of
undertakers, auditors' reports, and other matters.
The first of the Power Bills was promoted in 1898, under which it was
proposed to erect a large generating station in the Midlands from which
an area of about two thousand square miles would be supplied. Vigorous
opposition was organized against the bill by the local authorities and
it did not pass. The bill was revived in 1899, but was finally crushed.
In 1900 and following years several power bills were successfully
promoted, and the following are the areas over which the powers of these
acts extend:
In Scotland, (1) the Clyde Valley, (2) the county of Fife, (3) the
districts described as "Scottish Central," comprising Linlithgow,
Clackmannan, and portions of Dumbarton and Stirling, and (4) the
Lothians, which include portions of Midlothian, East Lothian, Peebles
and Lanark.
In England there are companies operating in (1) Northumberland, (2)
Durham county, (3) Lancashire, (4) South Wales and Carmarthenshire, (5)
Derbyshire and Nottinghamshire, (6) Leicestershire and Warwickshire, (7)
Yorkshire, (8) Shropshire, Worcestershire and Staffordshire, (9)
Somerset, (10) Kent, (11) Cornwall, (12) portions of Gloucestershire,
(13) North Wales, (14) North Staffordshire, Derbyshire, Denbighshire and
Flintshire, (15) West Cumberland, (16) the Cleveland district, (17) the
North Metropolitan district, and (18) the West Metropolitan area. An
undertaking which may be included in this category, although it is not a
Power Act company, is the Midland Electric Corporation in South
Staffordshire. The systems of generation and distribution are generally
10,000 or 11,000 volts three-phase alternating current.
The powers conferred by these acts were much restricted as a result of
opposition offered to them. In many cases the larger towns were cut out
of the areas of supply altogether, but the general rule was that the
power company was prohibited from supplying direct to a power consumer
in the area of an authorized distributor without the consent of the
latter, subject to appeal to the Board of Trade. Even this restricted
power of direct supply was not embodied in all the acts, the power of
taking supply in bulk being left only to certain authorized distributors
and to authorized users such as railways and tramways. Owing chiefly to
the exclusion of large towns and industrial centres from their areas,
these power supply companies did not all prove as successful as was
expected.
In the case of one of the power companies which has been in a favourable
position for the development of its business, the theoretical
conclusions in regard to the economy of large production above stated
have been amply demonstrated in practice. In 1901, when this company was
emerging from the stage of a simple electric lighting company, the total
costs per unit were 1.05d. with an output of about 2-1/2 million units per
annum. In 1905 the output rose to over 30 million units mostly for power
and traction purposes, and the costs fell to 0.56d. per unit.
An interesting phase of the power supply question has arisen in London.
Under the general acts it was stipulated that the power-house should be
erected within the area of supply, and amalgamation of undertakings was
prohibited. After less than a decade of development several of the
companies in London found themselves obliged to make considerable
additions to their generating plants. But their existing buildings were
full to their utmost capacity, and the difficulties of generating
cheaply on crowded sites had increased instead of diminished during the
interval. Several of the companies had to promote special acts of
parliament to obtain relief, but the idea of a general combination was
not considered to be within the range of practical politics until 1905,
when the Administrative County of London Electric Power Bill was
introduced. Compared with other large cities, the consumption of
electricity in London is small. The output of electricity in New York
for all purposes is 971 million units per annum or 282 units per head of
population. The output of electricity in London is only 42 units per
head per annum. There are in London twelve local authorities and
fourteen companies carrying on electricity supply undertakings. The
capital expenditure is L3,127,000 by the local authorities and
L12,530,000 by the companies, and their aggregate capacity of plant is
165,000 k.w. The total output is about 160,000,000 units per annum, the
total revenue is over L2,000,000, and the gross profit before providing
for interest and sinking fund charges is L1,158,000. The general average
cost of production is 1.55d. per unit, and the average price per unit
sold is 3.16d., but some of the undertakers have already supplied
electricity to large power consumers at below 1d. per unit. By
generating on a large scale for a wide variety of demands the promoters
of the new scheme calculated to be able to offer electrical energy in
bulk to electricity supply companies and local authorities at prices
substantially below their costs of production at separate stations, and
also to provide them and power users with electricity at rates which
would compete with other forms of power. The authorized capital was
fixed at L6,666,000, and the initial outlay on the first plant of 90,000
k.w., mains, &c., was estimated at L2,000,000. The costs of generation
were estimated at 0.15d. per unit, and the total cost at 0.52d. per unit
sold. The output by the year 1911 was estimated at 133,500,000 units at
an average selling price of 0.7d. per unit, to be reduced to 0.55d. by
1916 when the output was estimated at 600,000,000 units. The bill
underwent a searching examination before the House of Lords committee
and was passed in an amended form. At the second reading in the House of
Commons a strong effort was made to throw it out, but it was allowed to
go to committee on the condition--contrary to the general
recommendations of the parliamentary committee of 1898--that a purchase
clause would be inserted; but amendments were proposed to such an extent
that the bill was not reported for third reading until the eve of the
prorogation of parliament. In the following year (1906) the
Administrative Company's bill was again introduced in parliament, but
the London County Council, which had previously adopted an attitude both
hostile and negative, also brought forward a similar bill. Among other
schemes, one known as the Additional Electric Power Supply Bill was to
authorize the transmission of current from St Neots in Hunts. This bill
was rejected by the House of Commons because the promoters declined to
give precedence to the bill of the London County Council. The latter
bill was referred to a hybrid committee with instructions to consider
the whole question of London power supply, but it was ultimately
rejected. The same result attended a second bill which was promoted by
the London County Council in 1907. The question was settled by the
London Electric Supply Act 1908, which constitutes the London County
Council the purchasing authority (in the place of the local authorities)
for the electric supply companies in London. This Act also enabled the
Companies and other authorized undertakers to enter into agreements for
the exchange of current and the linking-up of stations.
Legislation and regulations.
The general supply of electricity is governed primarily by the two acts
of parliament passed in 1882 and 1888, which apply to the whole of the
United Kingdom. Until 1899 the other statutory provisions relating to
electricity supply were incorporated in provisional orders granted by
the Board of Trade and confirmed by parliament in respect of each
undertaking, but in that year an Electric Lighting Clauses Act was
passed by which the clauses previously inserted in each order were
standardized. Under these acts the Board of Trade made rules with
respect to applications for licences and provisional orders, and
regulations for the protection of the public, and of the electric lines
and works of the post office, and others, and also drew up a model form
for provisional orders.
Until the passing of the Electric Lighting Acts, wires could be placed
wherever permission for doing so could be obtained, but persons breaking
up streets even with the consent of the local authority were liable to
indictment for nuisance. With regard to overhead wires crossing the
streets, the local authorities had no greater power than any member of
the public, but a road authority having power to make a contract for
lighting the road could authorize others to erect poles and wires for
the purpose. A property owner, however, was able to prevent wires from
being taken over his property. The act of 1888 made all electric lines
or other works for the supply of electricity, not entirely enclosed
within buildings or premises in the same occupation, subject to
regulations of the Board of Trade. The postmaster-general may also
impose conditions for the protection of the post office. Urban
authorities, the London County Council, and some other corporations have
now powers to make by-laws for prevention of obstruction from posts and
overhead wires for telegraph, telephone, lighting or signalling
purposes; and electric lighting stations are now subject to the
provisions of the Factory Acts.
Parliamentary powers to supply electricity can now be obtained by (A)
Special Act, (B) Licence, or (C) Provisional order.
A. _Special Act._--Prior to the report of Lord Cross's joint committee
of 1898 (referred to above), only one special act was passed. The
provisions of the Electric Power Acts passed subsequently are not
uniform, but the following are some of the usual provisions:--
The company shall not supply electricity for lighting purposes except to
authorized undertakers, provided that the energy supplied to any person
for power may be used for lighting any premises on which the power is
utilized. The company shall not supply energy (except to authorized
undertakers) in any area which forms part of the area of supply of any
authorized distributors without their consent, such consent not to be
unreasonably withheld. The company is bound to supply authorized
undertakers upon receiving notice and upon the applicants agreeing to
pay for at least seven years an amount sufficient to yield 20% on the
outlay (excluding generating plant or wires already installed). Other
persons to whom the company is authorized to supply may require it upon
terms to be settled, if not agreed, by the Board of Trade. Dividends are
usually restricted to 8%, with a provision that the rate may be
increased upon the average price charged being reduced. The maximum
charges are usually limited to 3d. per unit for any quantity up to 400
hours' supply, and 2d. per unit beyond. No preference is to be shown
between consumers in like circumstances. Many provisions of the general
Electric Lighting Acts are excluded from these special acts, in
particular the clause giving the local authority the right to purchase
the undertaking compulsorily.
B. _Licence._--The only advantages of proceeding by licence are that it
can be expeditiously obtained and does not require confirmation by
parliament; but some of the provisions usually inserted in provisional
orders would be _ultra vires_ in a licence, and the Electric Lighting
Clauses Act 1899 does not extend to licences. The term of a licence does
not exceed seven years, but is renewable. The consent of the local
authority is necessary even to an application for a licence. None of the
licences that have been granted is now in force.
C. _Provisional Order._--An intending applicant for a provisional order
must serve notice of his intention on every local authority within the
proposed area of supply on or before the 1st of July prior to the
session in which application is to be made to the Board of Trade. This
provision has given rise to much complaint, as it gives the local
authorities a long time for bargaining and enables them to supersede
the company's application by themselves applying for provisional orders.
The Board of Trade generally give preference to the applications of
local authorities.
In 1905 the Board of Trade issued a memorandum stating that, in view of
the revocation of a large number of provisional orders which had been
obtained by local authorities, or in regard to which local authorities
had entered into agreements with companies for carrying the orders into
effect (which agreements were in many cases _ultra vires_ or at least of
doubtful validity), it appeared undesirable that a local authority
should apply for a provisional order without having a definite intention
of exercising the powers, and that in future the Board of Trade would
not grant an order to a local authority unless the board were satisfied
that the powers would be exercised within a specified period.
Every undertaking authorized by provisional order is subject to the
provision of the general act entitling the local authority to purchase
compulsorily at the end of forty-two years (or shorter period), or after
the expiration of every subsequent period of ten years (unless varied by
agreement between the parties with the consent of the Board of Trade),
so much of the undertaking as is within the jurisdiction of the
purchasing authority upon the terms of paying the then value of all
lands, buildings, works, materials and plant, suitable to and used for
the purposes of the undertaking; provided that the value of such lands,
&c., shall be deemed to be their fair market value at the time of
purchase, due regard being had to the nature and then condition and
state of repair thereof, and to the circumstance that they are in such
positions as to be ready for immediate working, and to the suitability
of the same to the purposes of the undertaking, and where a part only of
the undertaking is purchased, to any loss occasioned by severance, but
without any addition in respect of compulsory purchase or of goodwill,
or of any profits which may or might have been or be made from the
undertaking or any similar consideration. Subject to this right of
purchase by the local authority, a provisional order (but not a licence)
may be for such period as the Board of Trade may think proper, but so
far no limit has been imposed, and unless purchased by a local authority
the powers are held in perpetuity. No monopoly is granted to
undertakers, and since 1889 the policy of the Board of Trade has been to
sanction two undertakings in the same metropolitan area, preferably
using different systems, but to discourage competing schemes within the
same area in the provinces. Undertakers must within two years lay mains
in certain specified streets. After the first eighteen months they may
be required to lay mains in other streets upon conditions specified in
the order, and any owner or occupier of premises within 50 yds. of a
distributing main may require the undertakers to give a supply to his
premises; but the consumer must pay the cost of the lines laid upon his
property and of so much outside as exceeds 60 ft. from the main, and he
must also contract for two and in some cases for three years' supply.
But undertakers are prohibited in making agreements for supply from
showing any undue preference. The maximum price in London is 13s. 4d.
per quarter for any quantity up to 20 units, and beyond that 8d. per
unit, but 11s. 8d. per quarter up to 20 units and 7d. per unit beyond is
the more general maximum. The "Bermondsey clause" requires the
undertakers (local authority) so to fix their charges (not exceeding the
specified maximum) that the revenue shall not be less than the
expenditure.
There is no statutory obligation on municipalities to provide for
depreciation of electricity supply undertakings, but after providing for
all expenses, interest on loans, and sinking fund instalments, the local
authority may create a reserve fund until it amounts, with interest, to
one-tenth of the aggregate capital expenditure. Any deficiency when not
met out of reserve is payable out of the local rates.
The principle on which the Local Government Board sanctions municipal
loans for electric lighting undertakings is that the period of the loan
shall not exceed the life of the works, and that future ratepayers shall
not be unduly burdened. The periods of the loans vary from ten years for
accumulators and arc lamps to sixty years for lands. Within the county
of London the loans raised by the metropolitan borough councils for
electrical purposes are sanctioned by the London County Council, and
that body allows a minimum period of twenty years for repayment. Up to
1904-1905, 245 loans had been granted by the council amounting in the
aggregate to L4,045,067.
Standardization.
In 1901 the Institution of Civil Engineers appointed a committee to
consider the advisability of standardizing various kinds of iron and
steel sections. Subsequently the original reference was enlarged, and in
1902 the Institution of Electrical Engineers was invited to co-operate.
The treasury, as well as railway companies, manufacturers and others,
have made grants to defray the expenses. The committee on electrical
plant has ten sub-committees. In August 1904 an interim report was
issued by the sub-committee on generators, motors and transformers,
dealing with pressures and frequencies, rating of generators and motors,
direct-current generators, alternating-current generators, and motors.
In 1903 the specification for British standard tramway rails and
fish-plates was issued, and in 1904 a standard specification for tubular
tramway poles was issued. A sectional committee was formed in 1904 to
correspond with foreign countries with regard to the formation of an
electrical international commission to study the question of an
international standardization of nomenclature and ratings of electrical
apparatus and machinery.
The electrical industry.
The electrical manufacturing branch, which is closely related to the
electricity supply and other operating departments of the electrical
industry, only dates from about 1880. Since that time it has undergone
many vicissitudes. It began with the manufacture of small arc lighting
equipments for railway stations, streets and public buildings. When the
incandescent lamp became a commercial article, ship-lighting sets and
installations for theatres and mansions constituted the major portion of
the electrical work. The next step was the organization of
house-to-house distribution of electricity from small "central
stations," ultimately leading to the comprehensive public supply in
large towns, which involved the manufacture of generating and
distributing plants of considerable magnitude and complexity. With the
advent of electric traction about 1896, special machinery had to be
produced, and at a later stage the manufacturer had to solve problems in
connexion with bulk supply in large areas and for power purposes. Each
of these main departments involved changes in ancillary manufactures,
such as cables, switches, transformers, meters, &c., so that the
electrical manufacturing industry has been in a constant state of
transition. At the beginning of the period referred to Germany and
America were following the lead of England in theoretical developments,
and for some time Germany obtained electrical machinery from England.
Now scarcely any electrical apparatus is exported to Germany, and
considerable imports are received by England from that country and
America. The explanation is to be found mainly in the fact that the
adverse legislation of 1882 had the effect of restricting enterprise,
and while British manufacturers were compulsorily inert during periods
of impeded growth of the two most important branches of the
industry--electric lighting and traction--manufacturers in America and
on the continent of Europe, who were in many ways encouraged by their
governments, devoted their resources to the establishment of factories
and electrical undertakings, and to the development of efficient selling
organizations at home and abroad. When after the amendment of the
adverse legislation in 1888 a demand for electrical machinery arose in
England, the foreign manufacturers were fully organized for trade on a
large scale, and were further aided by fiscal conditions to undersell
English manufacturers, not only in neutral markets, but even in their
own country. Successful manufacture on a large scale is possible only by
standardizing the methods of production. English manufacturers were not
able to standardize because they had not the necessary output. There had
been no repetitive demand, and there was no production on a large scale.
Foreign manufacturers, however, were able to standardize by reason of
the large uniform demand which existed for their manufactures.
Statistics are available showing the extent to which the growth of the
electrical manufacturing industry in Great Britain was delayed. Nearly
twenty years after the inception of the industry there were only
twenty-four manufacturing companies registered in the United Kingdom,
having an aggregate subscribed capital of under L7,000,000. But in 1907
there were 292 companies with over L42,000,000 subscribed capital. The
cable and incandescent lamp sections show that when the British
manufacturers are allowed opportunities they are not slow to take
advantage of them. The cable-making branch was established under the
more encouraging conditions of the telegraph industry, and the lamp
industry was in the early days protected by patents. Other departments
not susceptible to foreign competition on account of freightage, such as
the manufacture of storage batteries and rolling stock, are also fairly
prosperous. In departments where special circumstances offer a prospect
of success, the technical skill, commercial enterprise and general
efficiency of British manufacturers manifest themselves by positive
progress and not merely by the continuance of a struggle against adverse
conditions. The normal posture of the British manufacturer of electrical
machinery has been described as one of desperate defence of his home
trade; that of the foreign manufacturer as one of vigorous attack upon
British and other open markets. In considering the position of English
manufacturers as compared with their foreign rivals, some regard should
be had to the patent laws. One condition of a grant of a patent in most
foreign countries is that the patent shall be worked in those countries
within a specified period. But a foreign inventor was until 1907 able to
secure patent protection in Great Britain without any obligation to
manufacture there. The effect of this was to encourage the manufacture
of patented apparatus in foreign countries, and to stimulate their
exportation to Great Britain in competition with British products. With
regard to the electrochemical industry the progress which has been
achieved by other nations, notably Germany, is very marvellous by
comparison with the advance made by England, but to state the reasons
why this industry has had such extraordinary development in Germany,
notwithstanding that many of the fundamental inventions were made in
England, would require a statement of the marked differences in the
methods by which industrial progress is promoted in the two countries.
There has been very little solidarity among those interested in the
commercial development of electricity, and except for the discussion of
scientific subjects there has been very little organization with the
object of protecting and promoting common interests. (E. GA.)