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37
The disadvantages advocated by the opponents of this system
are:—
(a.) Enormous cost of mains as compared with the high tension
alternating current system owing to the large
sectional area of copper required.
(b.) Loss of current in accumulators.
(c.) Depreciation of accumulators and consequent cost of
renewals.
(d.) Unsuitability for a large or scattered area.
The second system before mentioned, namely, the high tension
alternating current transformer system, is more generally used for large
or straggling districts, and is the system adopted for incandescent
lighting by the Dublin and Blackpool Corporations, and by various
companies at Brighton, Eastbourne, Exeter, Hastings, and other places,
and by the City of London Company, the Metropolitan Company, and
the House-to-House Company in the metropolis. The special feature
of this system is that it supplies low tension currents on the premises
lighted, while the mains are charged at high pressure, this high pressure
being transformed at suitable points to low pressure by means of an
apparatus known as the convertor or transformer. The transformers
are fixed either in sub-stations (in which case low tension distributing
mains are laid from these stations through the streets to be lighted)
or upon the consumers' premises. This latter arrangement is a great
advantage in the first instance when the demand for light is sure to be
scattered. Were it not for this arrangement it would be necessary to
lay low tension mains throughout the streets for the sake of, perhaps,
one or more consumers. The system is one which provides fully for
the safety of the public under the strict regulations laid down by the
Board of Trade. A further great advantage of the system is that of the
cost of cables, the low tension cables being, it is stated, from 100 to 400
times the size of high tension cables carrying the same load at same
percentage loss, and consequently, much more expensive.