ELECTRICAL ENGINEER’S EVIDENCE

Press, Volume LXXXIV, Issue 25447, 19 March 1948, Page 8

ELECTRICAL ENGINEER’S EVIDENCE

“There is no evidence to show that the supply of electricity, the protective device within the Lichfield street substation on the circuit to the overhead line, or the overhead line was improper so as to cause, due to electricity, the fire at Ballantyne’s. There is no. evidence to show that, due to electricity, the fire originated in any of the following electrical parts:—service entrance mains, service fuses, electricity mains cable, main electrical switchboard,” said Mr S. M. Nicol, testing engineer to the State Hydro-electric Department at Christchurch since 1938.

Long technical evidence was given by Mr Nicol-to show that any damage to the main electrical cable to the cellar was done subsequent to the fire and after the cable had become displaced from its original and correct position. The insulation was burned off the conductors of the service entrance mains where they projected beyond the indoor and outdoor ends of their enclosing pipe. There was no sign of electrical burning throughout their length and, for that reason, it was not considered that those entrance service mains caused the fire. Molten metal could drip out of the end of the seryice fuse when it was being blown but *u tue light of experience that the enclosing asbestos tube v.*as protection from fire due to the blowing of a fuse, it was not considered that the actual blowing of the three service fuses caused the fire. The mains cable showed signs of having been at a very nigh temperature and of an electrical burning in a length in a portion of the basement. There was no evidence of failure of the cable at the two points where it was prepared for connexion

to apoaratus—the service fuses and the oil-filled circuit breaker at extreme ends. Experience had ihown that failure of the insulation of such a cable at other than a point where it had been prepared for connexion to apparatus was extremely unlikely. He considered that any fault current flowing in the armour of the cable was so small as to be ineffective in promoting heating. Although the marble main switchboard had been damaged by fire and falls of debris, no signs were noticed which would point to a heavy short circuit occurring on any of the apparatus or sub-circuits.

Many technical questions on the construction of a cable, and use of fuses were asked by Mr T. A. Gresson (for Ballantyne’s) Witness said minor and major failures of insulation had occurred and if the current reached the steel armouring, a relatively good conductor. no great risk would be caused so long as the cable was properly earthed.

Mr Gresson: If you do not provide an earth, you will create an electrical hazard, varying in degree? It is hazardous not to provide an earth?—l am not prepared to say "Yes” to that question without reservation or qualification.