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247
The system is a combination of moderately high pressure
direct current batteries using accumulators, and direct current
motor transformers for low pressure discharge.
The mode of distribution employed is that the current is
generated at the central stations at a pressure of 1,000 volts,
and is delivered to five sub-stations where it is transformed by
means of continuous-current motor transformers to a pressure of
100 volts. Storage batteries are placed in these sub-stations,
which, after being charged from the high pressure mains are
switched on to the low pressure lamp service ; during the period
of light load the accumulators alone are used, and during the
period of heavy load,the transformers are turned on one at a time
as the load increases and turned off similarly as the load
decreases, the sub-stations being completely shut down after the
transformer work is over.
The lamp connections at the present time are 50,000 8-candle
incandescent power lamps. There is no public street lighting.
In Draycott Place there are six water-tube boilers (four of
Babcock and Wilcox type and two of Mills type) having a total
capacity of 900 horse power, at a working pressure of 150lbs.
per square inch. The waste steam is used for partially heating
the feed water; the current is generated by separately excited
dynamo machines, driven by Willan's compound high speed
engines coupled direct to the dynamos. The dynamos are of
the Elwell and Parker type. The Committee only visited one of
the sub-stations ; but they were informed that in three of them
a battery and motor transformers are used, and two of the substations
contain batteries alone.
The furthest point served from any sub-station in the district
is at present about 1½ miles.
PORTSMOUTH.
The site of the generating station is in proximity to the
harbour, and is fairly central for the supply mains radiating to
Southsea, Portsea and Landport. The buildings upon a portion
of the site have been erected to allow of future extensions being
economically carried out, they consist of boiler, economiser and
engine-house with a coal store convenient to the boilers. The
offices are over the coal store, and the store and test rooms, &c.,
adjoin the engine-house. The engine-house is 102 feet long by
66 feet wide, and is spanned by a travelling crane capable of
lifting a weight of at least 10 tons. The boilers consist of five
Lancashire boilers, and work at about 1401bs. to the square inch,
The boilers are fitted with mechanical stokers and furnaces, and
coal is conveyed to the hopper of these stokers by a conveyor running
across the boiler-house directly over the hopper. There are