3. Where any rails on which cars run or any conductors laid between or within three 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 three 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 three 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 four volts, shall suffice to produce a current of at least two 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 six feet of any pipe except a main for water supply of not less than three 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 two amperes per mile of single tramway line or five 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 direction of any current indicated by interposing a battery of three Leclanché cells connected in series if the direction of the current is from the return to the pipe, or by interposing one Leclanché cell if the direction of the current is from the pipe to the return.
In order to provide a continuous indication that the 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.
7. When the return is partly or entirely uninsulated a continuous record shall be kept by the Company of the difference of potential during the working of the tramway between the points of the uninsulated return furthest from and nearest to the generating station. If at any time such difference of potential exceeds the limit of seven volts, the Company shall take immediate steps to reduce it below that limit.
8. Every electrical connection with any pipe shall be so arranged as to admit of easy examination, and shall be tested by the Company at least once in every three months.
9. Every line and every insulated return or part of a return except any feeder shall be constructed in sections not exceeding one half of a mile in length, and means shall be provided for insulating each such section for purposes of testing.
10. The insulation of the line and of the return when insulated, and of all feeders and other conductors, shall be so maintained that the leakage current shall not exceed one hundredth of an ampere per mile of tramway. The leakage current shall be ascertained daily before or after the hours of running when the line is fully charged. If at any time it should be found that the leakage current exceeds one half of an ampere per mile of tramway the leak shall be localised and removed as soon as practicable and the running of the cars shall be stopped unless the leak is localised and removed within 24 hours. Provided that where both line and return are placed within a conduit this regulation shall not apply.
11. The insulation resistance of all continuously insulated cables used for lines, for insulated returns, for feeders, or for other purposes, and laid below the surface of the ground, shall not be permitted to fall below the equivalent of 10 megohms for a length of one mile. A test of the insulation resistance of all such cables shall be made at least once in each month.
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3. Where any rails ou which cars run or any conductors laid be- tween or within three 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 three fect of the rails fontos any part of a return, it shall be electrically connected to the rails at distances apart not exceeding 100 feet by ineans 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 no- gative 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 three 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 Govern ment 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 four volts, shall suffice to produce a current of at least two amperes from one earth connection to the other through the earth, and a test shall be made at least once in every month to as- certain whether this requirement is complied with. No portion of either earth connection shall be placed within six feet of any pipe except a main for water supply of not less than three inches internal dianister which is metallically connected to the earth connections with the consents bereinbefore specified.
6. When the return is partly or entirely uninsulated the Company shall in the construction and maitenance of the tramway (a) so se- parate the uninsulated return from the general mass of earth, and from any pipe in the vicinity; (6) 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 fol. lowing conditions, viz.
(i) That the current passing from the earth connections through the indicator to the generator shall not at any time ex- ceed either two amperes per mile of single tramway line or five per cent. of the total current output of the station.
(i) 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 Leelanche rell if the direction of the current is from the pipe to the
return.
In order to provide a continuous indication that the 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.
7. When the return is partly or entirely uninsulated a continuous record shall be kept by the Company of the difference of potential during the working of the tramway between the points of the uninsu- lated return furthest from and nearest to the generating station. If at any time such difference of potential exceeds the limit of seven volts, the Company shall take immediate steps to reduce it below that limit. 8. Every electrical connection with any pipe shall be so arranged as to admit of easy examination, and shall be tested by the Company at least once in every three months.
9. Every line and every insulated return or part of a return except any feeder shall be constructed in sections not exceeding one half of a mile in length, and means shall be provided for insulating earh such section for purposes of testing.
10. The insulation of the line and of the return when insulated, and of all feeders and other conductors, shall be so maintained that the leakage current shall not exceed one hundredth of an ampere per mile of tramway. The leakage current shall be ascertained daily before or after the hours of running when the line is fully charged. If at any time it should be found that the leakage current exceeds one half of an ampere per mile of tramway the leak shall be localised and removed as soon as practicable and the running of the cars shall be stopped unless the leak is localised and removed within 24 hours. Provided that where both line and return are placed within a conduir this regulation shall not apply.
1. The insulation resistance of all continuously insulated cables used for lines, for insulated returns, for feeders, or for other purposes. and laid below the surface of the ground, shall not be permitted to fall below the equivalent of 10 megohms for a length of one mile. test of the insulation resistance of all such cables shall be made at least once in each month.
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