BROKEN POWER LINES

Taranaki Daily News, 16 October 1934, Page 9

BROKEN POWER LINES

REPORT BY ENGINEER . WHAT REGULATIONS PROVIDE, DIRECTIONS FOR THE PUBLIC. Following prominence given in the Press to the danger of broken power lines after a Taranaki accident in which a number of cows were killed by electricity, Mr. W. H. Huggett, electrical engineer of the New Plymouth Borough Council, presented a comprehensive report to the town clerk which was tabled at the council meeting last night. Special reference was made in the report to an interview with Mr. A. C. Owen, of the Public Works Department, Wellington, in which Mr. Owen was reported to have said that regulations provided for an automatic cut-off in the case of wires breaking.

Mr. Huggett’s report read:— “Referring to the report under the heading broken power lines in a New Plymouth newspaper on October 10, I suggest that Mr. Owen did not quite understand tire position, or could not have been aware that the broken wires referred to in previous articles were low tension ones. The section of the regulations r quoted, No. 37, refers to high tension lines only, and reads as follows; Tn high and extra high pressure threephase alternating current systems,, the connection, of the circuits with . earth shall be made in accordance with the following requirements.’ “Section (c) states: Tn unattended generating stations or sub-stations supplying overhead lines, earth leakage relays shall be provided so that in the event of a leak to earth occurring either the faulty line will be cut out or the whole of the system supplied from this station or. sub-station rendered dead.’ “Section (f) states: Tn continuously attended generating stations or sub-sta-tions a visual. and audible indication may be used in place of automatic disconnection of supply-’ SAFETY PRECAUTIONS. “The other regulation quoted under No. 226 also deals with high or extra high-tension lines. All overhead electric lines are constructed in accordance with Public Works Department regulations, which provide for materials of ample strength, correct pole spacings and safety precautions, and are inspected annually by an officer of the Public Works Department; The regulations require that all high or extra high-tension lines shall be equipped with automatic cut-outs or earth leakage relays to indicate a fault or render any section ‘dead’ should they fall to earth. “With the relatively high soil resistance in this area the council, in order to make the system more safe, recently at great expense raised the primary voltage of the system from 6600 to 11,000 volts, as it was found that at 6600 volts the soil conditions generally, were such that the protective apparatus did not always function, and some gorse hedges were burnt in consequence. “All precautions have been taken and the whole system ‘rung’ with a grounded neutral wire, which means that a metallic circuit which is connected with the general mass of earth by connecting them with the underground water main at many points in the borough area and at Waitara and Inglewood, also at short intervals to iron pipes driven into the ground at permanently damp places throughout the area, provides a direct path for fault or earth currents to the power station. In this ring all earth connections are made and, as a further precaution, all fences along the roads where overhead lines are erected are well grounded. “It is not possible to instal protective apparatus to low-tension lines which would render .them ‘dead’ and ‘safe’ under all conditions; therefore all fallen lines should be treated as live ones and should not be touched except with a dry stick or other dry substance, and then the one endeavouring to move them must be careful that the end of the wire does not curl and contact with his body. RULES FOR THE PUBLIC. “General rules. to adopt for fallen wjres. might be given as follows: (a) Firstly, advise power supply authorities immediately; (b) do not touch or, allow anyone else to touch the wire, but guard it until it has been made ‘dead’; (c) if a fallen wire must be moved, do so only with something dry, such as a long stick, coat or other dry woollen or cotton material, but every care must be taken not to let the bare hands touch the wire. “Wire fences can be made . safe by earthing them. This can best be done by digging a trench about two feet deep and of sufficient length to take about 50 yards of stout wire, which should be placed in the bottom of the trench, back-filled and rammed and the ends of the wire securely connected, to all the wires on the fence. If this is done and the connection maintained, fences so treated could generally be regarded as safe; “Breaks in .wires Jiave been caused by irresponsible persons shooting at insulators with rifles, thus destroying the insulation of the line and damaging the wire, causing it to break in high winds. The department offers a reward of £25 to anyone giving information which will lead to the conviction of any person damaging borough property.”