18 The N.Z. Journal of Science and Technology. [Jan. 
load (see fig. 2). The peak is usually between 8 and 9 a.m., being determined 
by the tramway load. There is a drop of about 1,000 kilowatts at midday 
for the lunch-hour. The most striking feature of the load-curve is the 
high load-factor, which ranges on the weekly output up to 61 per cent. 
The system of supply is the three-phase system, at a frequency of 50 
cycles per second. The transmission distance from Lake Coleridge power¬ 
house to the main distributing-station at Addington is sixty-three miles, 
and the electrical pressure between the transmission-wires is 66,000 volts. 
At the main distributing-station the pressure is transformed down to 10,500 
volts, at which it is distributed over six primary distributors, each in 
duplicate and of 1,000 kilowatts capacity. These radiate as follows 
Underground Cables : Christchurch City -— Armagh Street substation, 
2J miles ; Montreal Street substation, 1 \ miles ; tramway substation 
(Falsgrave Street), 2J miles. 
Overhead Lines : Lyttelton feeder, via Spreydon, Beckenham, Farnly, 
St. Martins, Hillsborough, Woolston, and Heathcote substations, 9J miles ; 
southern feeder, via Sunnyside, Sockburn, Hornby, Islington, Templeton, 
Tai Tapu, and Lincoln substations, 23 miles ; northern feeder, via Bic- 
carton, Waimairi, Belfast, and Kaiapoi substations, 19 miles. 
Main Consumers. 
Christchurch City Council .-—-The City Council take control of the whole 
of the reticulation within the city boundaries, purchasing the energy in 
bulk from the Department at 10,500 volts pressure, and supplying their 
own transforming and distributing stations, at which the pressure is reduced 
to 400/230 volts, three-phase, for retail supply. At Montreal Street sub¬ 
station there is also a bank of 300-kilowatt transformers stepping down 
to 3,000 volts for supplying a few heavy-power consumers, and at Armagh 
Street substation there are two 500-kilowatt rotary converters supplying 
direct current to the previously existing direct-current reticulation. This 
station is also equipped with four boilers of 500 horse-power each, two 
of 250 horse-power each with automatic coal-stokers, and two of 125 
horse-power each connected with refuse-destructors but capable of also 
being hand-fired with coal, and also with four steam-driven generators 
with a total capacity of 750 kilowatts, constituting the previous supply 
plant and now used as a stand-by and for taking the peak load. The 
present peak load on the city mains is 2,200 kilowatts, of which 2,000 are 
supplied from Lake Coleridge, and the balance is taken by the city’s own 
generating plant, thus reducing the city’s payment for power, which is 
based upon the maximum load taken. 
The immediate effect of the introduction of hydro-electric power in the 
city was a striking reduction in the Council’s retail and wholesale charges 
for electricity. The average charge for light was reduced from 5d. to 3d., 
and for power from 2Jd. to Id., with wholesale power rates down to Jd. 
for ordinary day work and to ^d. for night work. 
In the two years since a regular supply has been obtained from Lake 
Coleridge the demand within the city has gone up from about 700 kilowatts 
to 2,200 kilowatts, and is still increasing rapidly. During the same period 
the number of consumers within the city has gone up from 1,625 to 3,877, 
of whom 22 per cent, now pay less than 3s. per month and 33 per cent, 
pay less than 4s. per month on the average. Electricity in Christchurch 
is thus distinctly the “ poor man’s light.” 
Tramway Supply .■—The next largest consumer is the Christchurch 
Tramway Board, with a normal day load of 1,400 kilowatts. Their plant 
