Power development "slow and painful growth"

Waimarino Bulletin, Volume 6, Issue 266, 6 December 1988, Page 8

Power development "slow and painful growth"

This account of the early history of the Ohakune Power Station, continued from last week, was written by ex Ohakune Borough engineer Frank Woodward, who was responsible for the running of the station from 1929 to about 1950, then again from 1952 to its closure in 1958. The opening of the new King Country Power Board depot recently marks the passing of another chapter in the history of electric power in the Waimarino. The board's old depot has been until now housed in the power house of the old Ohakune power station. The depot is now to be put up for private tender so has an uncertain future.

The power systems of Raetihi and Ohakune borough s were interlinked in 1930 and a load-building programme, only partly successful due to the depression, was instituted.

In 1932 a new agreement was entered into whereby the Ohakune plant was to completely shut down and entire supply requirements were taken from Raetihi. This course proved disastrous, as growth o f load in both areas and the inability of the Raetihi plant to meet the demand resulted in breakdowns and blackouts, poor voltage and a generally poor supply in both areas. A request by Raetihi to bc released from their contract was granted and a new agreement was made under which they had no liability for a constant suppiy. A survey had been made by the State Hydro-electric Department for a proposed 110 K.V. line between Ongarue and Bunnythorpe v i a Ohakune, and the promise of an assured

supply appeared possible. Dam construction The outbreak of war in 1939 retarded construction of this line however and some stop-gap was imperative. Permission was therefore obtained to construct a dam across the Mangawhero above the Railway bridge, and to excavate a cut in the lip of the Mangawhero crater lake and thus divert the Mangawhero into the crater. It was estimated that the flow of the Mangawhero could be doubled for the three critical peak hours per day if the storage could be filled each day off-peak. This project proceeded with the use of scrap material and local labour, the final cost being in the vicinity of only £300. It had been expected that this

supplementary storage would be required for a period of only two years, but four years passed before the provision of a sub-station of 1500 K.V.A. a t Makaranui on the new line built for the State Hydro-electric Department enabled it to be dispensed with. The period during which the extra storage was depended upon had been trying and difficult with a succession of floods of record magnitude threatening the existence of the dam, the last flood almost completely filling the riverbed to the crest of the dam with

metal and debris. Fortunately there were several large bulldozers available from the Public Works Department and those were put to work restoring the headworks to normal in quick time. New substation In 1943 the supply areas of Ohakune and Raetihi were amended so that the new Government substation became the boundary between both areas, Ohakune taking over a small portion o f Raetihi reticulation south of the substation. A small 110/11 KV transformer bank was installed and it appeared that at last ample power would now be the order of things to come. After a very brief respite load shedding became necessary, radiator restrictions and water heating control orders held sway and North Island power shortages usherejd in another another long period of difficult supply conditions, further aggravated by increasing demands throughout the area and requests for extension to almost all points of the compass within and outside the existing licensed area. Maximum output The hydro plant and later the semi-diesel unit were, at the request of the State Hydroelectric Department being run at maximum output for feedback purposes, the maximum demand output being added to simultaneous . maximum demand at the sub for charging purposes, with a small

unit rebate for units generated. The original supply from Government sources in 1943 was taken through an 11 to 6.6 KV transformer bank but the bulk of the area was still supplied at the original primary voltage of 2.4 K.V.

A proposal in 1948 to reticulate the whole licensed area south of Rangataua to Karioi, Tangiwai and Field's Track necessitated a rebuilding programme involving elimination of all but a small portion of 2.4 K.V. with eventual changeover of the whole area to 1 1 K.V. The late Mr H.E. Webb was engaged to prepare plans and estimates for this work which was sanctioned in 1951 at and estimated cost of £20,000. In the interim, the

writer, F. Woodward had taken up a position with another supply authority and Mr J.H. Nicholls had been appointed Engineer, remaining in that position until 1952 when the writer again took up the position. N o progress had been made

with the changeover or extensions due to difficulty in raising the authorised loan money. Slow painful growth This difficulty was overcome early i n 1953 and the first portion, changeover to 11 KV from the substation to the powerhouse, commenced. On completion of this, extensions involving 2 3 route miles of high tension were proceeded with, followed by the installation of a ripple

system for load control. By 1963 the undertaking had grown to a total of 110 route miles and consumers to 1000, a slow and painful growth from four route miles and 136 consumers in 1914. The undertaking has

however been proud of three notable achievements. In spite of a very low density of consumers per mile it had no recourse to rural reticulation subsidy assistance, twice it gave an emergency supply to a neighbouring authority for some days when their own source had failed, and twice it gave a skeleton supply to the N.Z.E.D. substation during transformer failures. For some years a V.H.P. radio telephone installation has enTurnpage9

Remnants of power production

From page 8 abled a small staff to deal promptly with servicing and fault conditions in difficult country and the tariff charged compares favourably with most predominantly rural authorities. Shut down It was with much re-

gret that the generating plant was finally shut down in 1958 after 44 years service, due solely to decay in the wooden portion of the fluming. In the 50 years of its operation, the area served developed from heavily bushed country to clear open farms and

market gardening. The sawmills decreased from fifteen to two and those two drew their timber from outside sources. This resulted in a static population with practically no industrial development over the years. But the provision of an elec-

tricity supply wherever requested in this sparsely settled area enhanced property values and was some compensation for those sturdy pioneers who transformed the countryside around Ohakune into the very productive area that emerged.