FALLEN ELECTRIC WIRES

Hauraki Plains Gazette, Volume XXXVII, Issue 4921, 4 January 1926, Page 4

FALLEN ELECTRIC WIRES

-THE FATALITY AT TAUWHARE.

USE OF PROTECTIVE DEVICES. The recent regrettable fatality at Tauwhare, when an elderly man and his grandson lost their lives, through the falling of a high tension line, has drawn widespread attention to the necessity of some apparatus which will, make provision for the automatic disconnection of lines in cases of their contact with the earth.

Discussing the matter with a Waikato Times representative, the engineer to the Thames Valley Power Board, Mr N. G. McLeod, stated that the incident was particularly unfortunate in that had the “faultmen” received the telephone message .the accident would not have occurred, but even then it would have been only good fortune, since a person may have been at the fence or under the wire when it fell.

“The use of overhead lines has been developed for two main reasons,” said Mr McLeod, “to allow of supply being given to consumers who could not otherwise obtain it owing to the too great cost of the underground system and to allow of supply being obtained from distant natural sources of power, the transmission pressure being greater than underground cables a,re manufactured to withstand.” He added that so far as New Zealand was concerned the firs,t reason given was the principal reason for the use of overhead lines. All lines have to be. constructed in accordance with the requirements of the Public Worhs Department’s regulations. In these regulations the worst conditions of windpressure and temperature were assumed, and the line must be designed to withstand at least twice, and for certain materials at least four times, these worst conditions'. Certain things may, however, occur .to the strongest lines to defeat the object of the safety factors mentioned. The collision of a vehicle with a pole-line might, and apparently did at Tauwhare, affect the safety of the line. Persons shooting at or throwing stones at insulators, might cause such another fatality. The care and experience of the men employed upon erection was a large factor also. The manner in which joints were made, the tension to which the wires were strung, and the avoidance of any nicks in copperwire were the principal points to be watched. It was a matter of interest that the most dangerous lines, when on the ground, were .those which did

not exceed the limits of high pres-

sure. Lines operating at extra high pressure, 11,000 volts and upwards, did not appear to have caused any personal accident in New Zealand due to .their falling on the ground, since the electrical disturbance caused by this condition was such that power was immediately cut off. In fact, it was seldom that a person had lost his life due to pressure of 15,000 volts, and upwards, unless, of course, he had actually fallen on the cnoductors,. This was because the current leaps to a person before he can actually touch the conductor, thus throwing him clear; and while the person might be rendered unconscious and receive severe burns, he usually made a satisfactory recovery. It was possible to render lines safe when they fell, but the extent of this protection and the limiting of the inconvenience to consumers due to power being cut off were questions of the capital expenditure which could, be afforded to render this protection.

Continuing, Mr McLeod said that tlie new Public Works, requlations, which would shortly be issued, made provision for the automatic, disconnection of lines in. the case of their contacting with earth. This regulation was fully endorsed by the supply authorities' engineers, at their conference in Wellington a little while ago. It demanded .that a line be made “dead” automatically within jt vei’y short time after it falls .to the ground. This would certainly give excellent protection compared .with what generally existed at the present time, but it would not prevent a person who was on a fence at the moment a line fell on it from receiving a shock. In his district, he said, the fences were earthed where lines, below a certain size cross or run parallel with fences. It wap an additional safeguard which would protect a person who was in contact with the fence if a wire fell. The possibility of a wire actually falling on a person was most remote, and while it was, possible to build and protect lines so that they would be made “dead” before actually touching the ground, the cost would be such as to prohibit supply to liiojst country consumers. The extent to which supply to consumers would be interfered with by the operation of protective devices als.o depended upon how much money could be afforded in supplying protection. Di the case of a line coming down, that line would be made “dead,” but it was not desirable that many good lines should be cut out along with the defective line. It was possible to isolate only the defective line, or even only the defective portion of that line, but the extent to which this' could be done depended

upon how much money was available.

Summarising the .whole case for prevention of danger to life, Mr McLeod considered, that it was more important for fallen wires to be avoided, and that the supply authority be immediately notified. All cases of coir lision with poles should be immediately reported, even though the line appeared to be uninjured; that all men working on lines should lie absolutely faithful in their services,, iso that no defective material or workmanship was allowed.; and that any person doing anything to injure a line should be informed upon, as it was a matter affecting public safety. It was stated by Mr McLeod that his board was obtaining suitable protective apparatus, and that he knew several other boards were doing likewise.