GAS EXPLOSION.

Auckland Star, Volume LXV, Issue 2, 3 January 1934, Page 3

GAS EXPLOSION.

ORIGIN UNCERTAIN. POWER BOARD INVESTIGATION CABLE IN PERFECT ORDER. A careful investigation was made this morning in an endeavour to trace the cause of the serious explosion in Khyber Pass at an early hour yesterday morning which wrecked a house and set lire to it. The cause, however, has not been precisely determined. The general manager of the Auckland Electric Power Board, Mr. E. H. Bartley, said that there was sufficient evidence to say definitely that the explosion which followed a cable fault was in no way due to gases formed either through cable insulation or cable compounds. "The distance of the fault from the seat of the explosion," said Mr. Bartley, "is approximately 18 to 20 feet, and there i.s distinct evidence of gas ignition resulting from a cable fault even at that distance. The ground in the locality has been built up on three separate occasions, and on the dwelling side it is loosely packed and contains a number of cavities, voids or pockets in which gas can be retained. The electric cable on loth sides of the fault has been excavated and examined, and found in perfect condition, despite the fact that it has been in use for 12 to 15 years.

Policy of Replacing Cables. "All underground cables, whether for electrical supply purposes or otherwise, are- subjected to severe mechanical strains, and the system of laying adopted many years ago does not offer the .same mechanical protection as that provided by modern methods. The policy of the Auckland Electric Power Board has been to adopt later methods, using paper-insulated, lead-covered armoured cable instead of the earlier V.B. cable, and during the last two years many miles of reticulation have been dealt with. In fact, wherever any deterioration is indicated by testing, the work of relaying has been carried out. Practically the whole of the centre of the city has been dealt with, but _in respect to the area under consideration the cable has been shown to be in a perfectly good condition, calling for no attention.

"It is surmised that the cable fault in question has resulted from a subsidence in the 'made' ground throwing stresses on the cable beyond its mechanical strength. This damages the insulation, with the result that a fault is liable to occur. "Underground cable faults are met with in all electrical systems, due principally to the reasons stated, but on account of precautions taken and the provisions made for dealing with the.se faults, in recent years, generally speaking, troubles from this cause have been remarkably few."