Strong Cable Sheathing

Press, Volume CII, Issue 30215, 21 August 1963, Page 14

Strong Cable Sheathing

(M.Z Press Association) WELLINGTON, August 20. Scientific tests had shown the armour which would sheath the Cook Strait power cable would wear rocks away more quickly than they would wear it away, said the general manager of the Electricity Department (Mr E. B. McKenzie) to the Wellington Lions' Club today. The armour was included m the cable to prevent it bending too sharply if it fell across rocks on the seabed when it was laid, said Mr McKenzie. A trial section of cable was deliberately laid over rocks at the entrance to

Oteranga Bay to test its ability to withstand damage when swinging in tidal changes. It was found to be as good as the day it was put down when it was lifted from the seabed two years later. Discussing the problems en countered in planning the pro ject, Mr McKenzie said that, of the two possible power cable routes, bne was 43 miles and the other 254 miles. Had the 43-mile route been chosen, the transmission of DC. current under the sea would have set up a magnetic field which would have upset ships’ compasses on the aporoaches to Wellington harbour. No such problem would be encountered on the 251-mile route from Fighting Bay in the South Island to Oteranga Bay in the north, along which three cables were to be laid 1000 yards apart. Each cable would be in one complete length, joints being eliminated.

Mr McKenzie, who illustrated his address with slides said the Cook Strait power cable project had really begun in 1950 when the department's chief engineer (Mr M G. Latta) put the scheme forward as a method of pro vid ing the North Island with the additional power it was foreseen it would need in 1965 and which it would be unable to supply from its own natural resources. About £ 125.000 had been spent on proving the practicability of the Cook Strait cable, he said. The 330 miles of transmission lines between Benmore and Haywards would cost £5,5 million. The cable itself would cost £2.877 million, and equipment for converting Benmore power from A.C. to DC. current and back from D C. to A.C. at Haywards would cost £9.3 million, making a total cost of £17.7 million. The cable had to be in service by late March, 1965, said Mr McKenzie.