System of Distribution.

The mains from the Kensington Court Station are laid underground in a culvert 18 in. by 12 in., which is built with brickwork and cement under the pavement. A double conductor of flat copper, 0·25 square inches section, is stretched from shackle insulators attached to iron bars, which are firmly built into the culvert; the continuity of the circuit is provided by means of stranded wire, which connects each section; the flat copper rests on the top of porcelain insulators, fixed on vertical iron pieces, which are built into the floor. Connections with the sewers are left for drainage, and six surface boxes are provided for every hundred yards. Where house connections have to be made, the branch wires are united by soldering to the bare copper mains. For crossing under the streets a heavily insulated cable is employed, and is led through cast-iron pipes.

Fig. 26.

Until a larger amount of mileage is actually at work, it is difficult to express an opinion as to which is the cheapest and most efficient method of laying conductors in the streets. The relative cost of two plans tried at Kensington Court—the insulated and the bare cable in a culvert—was given by Mr. Crompton in the following Tables, [No. 1] and [No. 2], which are taken from a paper read before the Society of Telegraph Engineers and Electricians on April 12th, 1888.

[Table No. 1] refers more particularly to what is known as the Callender-Webber system of using bitumen concrete, which is compressed into blocks or cases usually about 6 ft. long, 8 in. by 5½ in. section, having two-inch holes through which the insulated copper cable is led.

The estimates given in [Table No. 2] were criticised by Mr. Kapp, who thought that “a more reliable conductor could be obtained by using a high-class lead-covered cable, which might be laid in the ground with the simple protection of a rough tarred plank to cover it.” The cost of digging the trench and running in the cable from the drum was quoted at 3s. a yard, and the total cost, inclusive of £10 for surface boxes, at £155 per 100 yards, instead of £187, as shown by the Table.

Table I.

Cost of Laying 100 Yards of Double Conductor
underneath the Footway of a London Street.

Single.
No. 16.		⁷⁄₁₆¹⁹⁄₁₅¹⁹⁄₁₂¹⁹⁄₁₀
Area, square inches·0032·0225·0773·16130·25
Area, square millimetres2·0814·650104161·25
Weight per 100 yards run lb.7½53½183¼392576
Cost of copper at 7¾ d. £ 04 101 146 518 012 130 1815 0
Cost of insulation 13 24 86 112 024 170 3517 0
 Total cost of Cables 18 06 30 170 037 100 5412 0
Casing, bitumen, and cement 53 05 50 80 012 100 1210 0
Labour, Laying 30 04 00 50 05 00 60 0
Trenching and repairing 250 025 00 250 025 00 250 0
Surface boxes and connection 50 07 00 100 010 00 100 0
Engineer and superintendent 30 04 00 50 05 00 60 0
 Total £ 4211 051 80 700 095 00 1142 0
Add extra if copper, at 9½ d. 01 10 80 17 02 170 35 0
4212 151 160 717 097 170 1177 0
Cost of copper per lb., laid complete 513 60 194 07 90 50 04 1
Current in ampères1·28·1285890
Cost per ampère 3510 06 80 210 61 139 16 0
³⁷⁄₁₀Two Sets.
³⁷⁄₁₀		Four Sets.
³⁷⁄₁₀		Six Sets.
³⁷⁄₁₀
Area, square inches0·51·02·03·0
Area, square millimetres32264512901935
Weight per 100 yards run lb.1153230646126918
 Total cost of Cables 1080 0216 00 4320 0648 00
Casing, bitumen, and cement 160 022 00 400 055 00
Labour, Laying 100 018 00 350 050 00
Trenching and repairing 250 025 00 300 035 00
Surface boxes and connection 100 010 00 100 010 00
Engineer and superintendent 100 010 00 200 025 00
 Total 1790 0301 00 5670 0823 00
Add extra if copper, at 9½ d. 810 017 00 340 051 00
18710 0318 00 6010 0874 00
Cost of copper per lb., laid complete 03 3½0 28¾ 02 7¼0 26¼
Current in ampères1803607201,080
Cost per ampère 11 00 176 016 80 161

Table II.

Cost of Laying 100 Yards of Double Conductor of
Bare Copper carried on Insulators in a Culvert.

Area in square inches0·250·51·0
Area in square millimetres161·25322·5645
Weight of copper in lb. per 100 yards57611532306
Cost of copper at 7¾ d. per lb. £ 1815 037 50 7410 0
Laying 90 09 120 912 0
Insulators 04 60 46 04 6
6 surface boxes and connections 100 010 00 100 0
Culvert, 18 inches × 12 inches, for two lines conductor, 538 053 80 538 0
 in brickwork and cement, replacing pavement
Engineers and superintendence 60 010 00 100 0
Total £ 977 6120 96 15714 6
Extra for copper at 9½ d. per lb. 35 08 100 170 0
Total £ 10012 6128 196 17414 6
Cost of copper per lb. laid complete42 d.27 d.18·2 d.
Current in ampères90180360
Cost per ampère 12 30 145 09 8
Area, square inches2·02·553·00
Area, square millimetres129016451935
Weight of copper in lb. per 100 yards461261256918
Cost of copper at 7¾ d. per lb. 1490 0190 00 2240 0
Laying 915 09 150 100 0
Insulators 04 60 46 04 6
6 surface boxes and connections 100 010 00 100 0
Culvert, 18 inches × 12 inches, for two lines conductor, 538 053 80 538 0
 in brickwork and cement, replacing pavement
Engineers and superintendence 100 010 00 150 0
Total 2327 6263 76 31212 6
Extra for copper at 9½ d. per lb. 340 043 100 510 0
Total 2667 6306 76 36312 6
Cost of copper per lb. laid complete13·8 d.12 d. 12 6 d.
Current in ampères7209101080
Cost per ampère 07 50 69 06 8½