1456
No. 10 of 1902.
TRAMWAY.
3. Where any rails, on which cars run, or any conductors laid between or within 3 feet of such rails, form any part of a return such part may be uninsulated. All other returns or parts of a return shall be insulated, unless of such sectional area as will reduce the difference of potential between the ends of the uninsulated portion of the return below the limit laid down in rule 7.
4. When any uninsulated conductor laid between or within 3 feet of the rails forms any part of a return, it shall be electrically connected to the rails at distances apart not exceeding 100 feet by means of copper strips having a sectional area of at least one-sixteenth of a square inch, or by other means of equal conductivity.
5. When any part of a return is uninsulated it shall be connected with the negative terminal of the generator, and in such case the negative terminal of the generator shall also be directly connected, through the current indicator hereinafter mentioned, to two separate earth connections which shall be placed not less than 20 yards apart. Provided that in place of such two earth connections the company may make one connection to a main for water supply of not less than 3 inches internal diameter, with the consent of the owner thereof and of the person supplying the water, and provided that where, from the nature of the soil or for other reasons, the company can show to the satisfaction of an inspecting officer of the Government that the earth connections herein specified cannot be constructed and maintained without undue expense, the provisions of this rule shall not apply. The earth connections referred to in this rule shall be constructed, laid, and maintained so as to secure electrical contact with the general mass of earth, and so that an electro-motive force, not exceeding 4 volts, shall suffice to produce a current of at least 2 amperes from one earth connection to the other through the earth, and a test shall be made at least once in every month to ascertain whether this requirement is complied with. No portion of either earth connection shall be placed within 6 feet of any pipe except a main for water supply of not less than 3 inches internal diameter which is metallically connected to the earth connections with the consents hereinbefore specified.
6. When the return is partly or entirely uninsulated the company shall in the construction and maintenance of the tramway-(a) so separate the uninsulated return from the general mass of earth, and from any pipe in the vicinity: (b) so connect together the several lengths of the rails: (c) adopt such means for reducing the difference produced by the current between the potential of the uninsulated return at any other point: and (d) so maintain the efficiency of the earth connections specified in the preceding rules, as to fulfil the following conditions, viz.:-
(i) that the current passing from the earth connections through the indicator to the generator shall not at any time exceed either 2 amperes per mile of single tramway line, or 5 per cent. of the total current output of the station.
(ii) that if at any time and at any place a test be made by connecting a galvanometer or other current-indicator to the uninsulated return to any pipe in the vicinity, it shall always be possible to reverse the