LAKE COLERIDGE.

Press, Volume LXII, Issue 18678, 29 April 1926, Page 8

LAKE COLERIDGE.

VERY HEAVY OVERLOAD. WHY FEND ALTON WAS DARK. J Comparatively early in the evening of Friday last, the 33rd inst., an unprecedented demand on Lake Coleridge power was made, and the previous record maximum load —which was 14,740 k.w., or 2740 k.w. in excess of the nominal capacity of tho generating plant, and which was registered between <5.30 p.m. and 7 p.m. en the 9th inst.—was exceeded.

The actual load is not known, because at 5.52 p.m. an S.O.S. was received from the power station, asking for relief. At that time the load probably was up to the previous record—l4,74o k.w. The Tramway Board immediately was called upon to supply 500 k.w. from its stand-by plant, and did so. This, however, proved insufficient, and to relievo the Lake Coleridge Power House, certain of the Public Works Department's 11,000 volt feeders at the Addington sub-station had to bo cut oft'. Unfortunately one of those feeders supplied the Waimairi County, and Fendalton, and other parts of the county were deprived of light, the urgency for relief being so great that it was not. possible to give any warning. It is considered probable that the maximum load en Fridnv night was over 10,000 k.w.

Provision for Greater Relief. As stated in "The Press," 011 tho 17th inst., the Department can call on stand-by plants that can afford relief up to ISOO k.w. Discussing last Friday's experience with a reporter, Mr It. G. HacGibbon, Resident Engineer, Lake Coleridge scheme, stated yestorday that it was unlikely to recur as the Department has made arrangements with the Tramway Board for its plant to provide 1000 k.w. every Friday night. "Tho overload capacity of tlm Lake Coleridge power station is not limited by the overload capacity of the turbines and generators," Mr Mac Gibbon added, by the quantity of water that can -he taken through the No. 1 tunnel. When a heavy overload occurs, like that experienced last Friday, the level of the water In the surge chamber falls rapidly. This is duo to the friction in the tunnel, and tho limit of the output of the station is reached when the level of the water in the surge chamber drops below tho lovel of the top of the pipe line, a state of things that lets air as well as water into the pipes. This condition of affairs will be remedied as soon as the new intake and surge chamber, with tho necessary gates, are completed. As it is proposed to complete the tunnel connecting the two surge chambers—thus permitting the new surge chamber to increase the supply of water to the old surge chamber—the excessive friction loss in the No. 1 tunnel at overload periods, will be eliminated. At present this connecting tunnel has been driven to the concrete wall of the old surge-chamber, and all that is necessary to complete it is to break through this wall. To do this will necessitate tho complete shutting down of the plant, and this will be done on & Sunday, in order to cause the least possible inconvenience to consumers. It is hoped that these works—the new intake, ■testing of the gates, and the connecting tunnel between the' two surge chambers —will be completed in three or four weeks.''

Work Well Advanced. Mr F. Langbien, Resident Engineer, Public Works Department, said that the intako works are well advanced; in fact, practically completod. The upward oxcavation, to connect the intako caisson with the subaqueous tunnel, has been finished. A certain length is to be taken off the top ol' the caisson, and when this is done tho water from the lake will flow into tho subaqueous tunnel and thence to the No. i tunnel. Tho gates at the inlet and at 1; '■ new surge chamber yet have to be-testsd, but this will not take long. The report for the week ended the 25th inst. states that the maximum load at the power-house was 14,430 k.w., registered between 11 a.m. and 11.30 a.m. on the 20th inst.; the previous week it was 14,680 k.w,, registered on the 114tli. As stated above, last week's t maximum at the power-house probably was 15,000 k.w. last Friday night. At the Addington substation the maximum load last week was 11,825 k.w., registered on the same date and between the same hours as the power-house maximum; the provious week it was 11,230 k.w. Tho lako level last week was at 1670.60 ft; tho previous week it Was 1670.73 ft; tho average inflow from the Harper river was 249 cusccs; the provious week, 274 cusccs.