The Ultimo Power Station, or Ultimo Powerhouse, was an electricity generating plant located in the inner-city Sydney suburb of Ultimo, New South Wales. Commissioned in 1899, it was the first major power station in Sydney and was originally built to supply power for the electric tram network. Prior to this, a small installation had existed at Regent Street, which was brought into use on 15 June 1882. Additionally, experimental electric tram operations powered by small generators had been in intermittent use in Sydney since 1890.
Generating plant
Ultimo Power Station boasted a mixture of equipment, initially consisting of American-made steam engines coupled to dynamoelectric machines (direct current generators). Later generating units were British-made turbo-alternators. Most of the alternating current (AC) equipment operated at 6,600 volts, 25 cycles per second.
Direct current plant – 600 V
The original generating plant at Ultimo consisted of four cross-compound, reciprocating steam engines supplied by E.P. Allis & Co of Milwaukee, Wisconsin, each rated at 1250 horsepower (hp) and running at 100 rpm. HP cylinder diameter was and LP cylinder diameter was . Steam pressure was . Each steam engine was coupled to a multi-pole, compound-wound dynamo supplied by the General Electric Company (GE) of Schenectady, New York. Each dynamo (generator) was rated at at 550 volts direct current (1545 amperes) and could be overloaded by up to 50 percent to satisfy peak demand. To cater to the growing demand of the electrified tram network, the engines were frequently run at . Each tram had less than worth of motors, but the original installation did not allow for growth. It followed that expansion of the power station beyond the initial four units was planned from the beginning.
Steam was initially supplied by 14 horizontal multi-tubular under-fired (Colonial) fire tube boilers by G. & C. Hoskins, Sydney. Each was rated at and operated at a pressure of . The boilers were hand fired and had natural draught to a single chimney at the end of the building. Only twelve boilers were needed to provide sufficient steam for full-capacity power generation, leaving two in reserve.
The original generating units were removed in 1915 and 1916, but some of the boilers were retained (see below).
First alternators – 6600 V, 25 Hz
The George St tram line experienced serious voltage drop problems, especially at the Circular Quay end. To fix this situation Alternators were brought into use from 1902, starting with three 1500 kW/6.6 kV units supplied by GE. Each alternator was powered by an Allis Reynolds vertical cross compound condensing reciprocating steam engine rated at 2500 hp at 75 rpm. HP cylinder diameter was and the LP cylinder diameter was with a stroke. The 40-pole alternators generated three phase current at 25 Hz.
Alterations to the boiler house at this stage saw six of the original boilers removed. Then eight Babcock & Wilcox long-drum, chain-grate boilers were added. Steam pressure was and superheaters gave a final temperature of . As more generators were installed an additional 24 new boilers from Babcock & Wilcox (UK), each rated at 450 hp at 160 lb/sq in were added. By 1904 a total of thirty two B&W boilers were then on site.
Provision (foundations) was made for the addition of three more reciprocating steam engine-alternator sets, but this was abandoned in favour of turbo-alternators.
Vertical engine nos 5, 7 and 9 were removed between 1912 and 1914 to allow the addition of turbo-alternators.
Turbo-alternators – 6600 V, 25 Hz
The first turbo-alternator was brought into use at Ultimo Power Station on 9 January 1905(No6)Supplied by C.A. Parsons & Company of Newcastle-upon-Tyne, England. The steam turbine was rated at 3000 hp, ran at 1500 rpm and drove an 1875 kW alternator at 50 Hz. The steam was raised in 16 new Babcock & Wilcox (UK) boilers, installed in 1905, bringing the total number of boilers on site to 48. These boilers were placed on top of the 32 original boilers.
Two additional turbo-alternators were brought into use in 1909. Supplied by C.A. Parsons & Company, each was rated at 5000 kW with an overload capacity of 7500 kW and generated three phase alternating current at 25 Hz. They were numbered 10 and 12. Twelve new Babcock & Wilcox (UK) superheated boilers were added in 1910, and another 8 were added in 1913. They were also placed on top of the original boilers. The remaining eight fire-tube boilers were removed in 1912/13 to make room for coal bunkers.