Benmore Will Allow High S.I. Peak Load

Press, Volume CIII, Issue 30541, 9 September 1964, Page 16

Benmore Will Allow High S.I. Peak Load

Transformers at the Benmore hydro-electric station would enable the station to contribute power at the rate of at least 400 megawatts to the South Island system, said Mr R. S. S. Meredith, district electrical engineer of the New Zealand Electricity Department, yesterday. Mr Meredith said this would allow a substantial increase on this winter’s peak of 603 megawatts in the South Island. He was replying to “Grid Dip,” who said in a letter to the editor of “The Press”:— “Is the power from Benmore, to be transmitted to the North Island, generated as alternating or direct cur-

rent? If as direct current, is there any provision made for conversion to A.C. for use in the South Island grid? Also, as D.C. is used over the Cook Strait cable, has provision been made to convert to A.C. at this end so that power can be sent from North to South if necessary?”

“Robbin’ Hood” asked a similar question. Mr Meredith said the generation at Benmore would be alternating current. It would be converted to direct current at Benmore to go through the transmission line and the Cook Strait cable, and back to alternating current at the other end. The AC-DC and DC-AC conversion valves at each end were identical and consequently were reversible, as were the cable and transmission line.

Control equipment being provided at present allowed for variation of the amount of power from zero to full load (600 megawatts) in the south to north direction only, by altering the phase angle of the grids in the valves. Reversal of flow would require some additional gridcontrol equipment. “Could Be Done”

“It is difficult to imagine practical circumstances when actual reversal would be required,” said Mr Meredith, “as it would mean that the South Island would be short by more than 600 megawatts. If actual reversal was required at some time in the distant future it could be done by installing a comparatively small amount of equipment.” Mr Meredith said it would be possible in effect to send large amounts of energy from the North Island to the South Island by reducing the amount of power being drawn off from the Benmore supply by the North Island. “In time of shortage in the South Island, for example, the Meremere steam station could be started up, and in consequence the whole of its output could be made available in the South Island. Similarly, extra load could be put on other North Island stations.”