Hong Kong Regulations

USE OF ELECTRIC POWER ON THE TRAMWAY RULES - RULE 8

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-

        (i)    that the current passing from the earth connections through the
               indicator to the generator shall not at any time exceed either
               1.2A/km of single tramway line, or five per cent of the total
               current output of the station; (L.N. 156 of 1977)

        (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 direction of any current indicated
               by interposing a battery of three Leclanche cells connected in
               series if the direction of the current is from the return to
               the pipe, or by interposing one Leclanche cell if the direction
               of the current is from the pipe to the return. In order to
               provide a continuous indication that condition (i) is complied
               with, the company shall place in a conspicuous position a
               suitable properly connected and correctly marked
               current-indicator and shall keep it connected during the whole
               time that the line is charged. The owner of any such pipe may
               require the company to permit him at reasonable times and
               intervals to ascertain by test that the conditions specified in
               (ii) are complied with as regards his pipe.