SECTIONAL TRANSACTIONS.— G. 351 



Sharlston Colliery. — The New Sharlston Colliery Co., Ltd., have one of the most 

 modern collieries in the district. Their hydraulic decking plant, new system of 

 spiral separators for cleaning coal, &c, are unique in this country. Their system of 

 economic power production is of exceptional interest. In their office is one of the 

 first pair of Parsons' turbines made. Visit to the coal-face. Tea by invitation of 

 the Company. 



Wakefield. 



Rothwell Haigh Collieries. — Messrs. J. & C. Charlesworth. Three very old 

 pumping engines, the oldest of which was probably originally of the ' Newcomen ' 

 type, erected in 1776, converted to ' Watt ' type in 1793. The engine at one time 

 pumped water to work a ' water balance ' for winding coal in adjacent shafts. There 

 is a ' horse gin ' for raising and lowering men working in the shaft. 



Monday, September 5. 



Mr. P. Dunsheath, O.B.E. — Super Tension Cables. 



The transmission of large blocks of power b}' underground cable is a subject of 

 great interest at the present time, and the paper reviews some of the most important 

 features of the problem. The working of cables at higher voltage is necessitated by 

 both technical and economic considerations, and the latter are illustrated by a series 

 of curves in which estimated costs of plant for typical super tension transmission are 

 plotted to show the interdependence of different factors, such as voltage and distance. 

 Time effects in cable failure are briefly discussed, and the characteristics and significance 

 of dielectric loss and power factor explained. In comparing the relative merits of 

 plain three-core and metal- sheathed core cables, it is shown that the latter havedecided 

 advantages, and one form, the reinforced S.L., possesses outstanding features. When 

 voltages of 66,000 and above are contemplated, the single core cable becomes a serious 

 rival to the three-core construction, and then eddy current losses in the sheaths have 

 to be guarded against by keeping the three cables as close together as possible and 

 avoiding individual magnetic armouring. The progress already made in cables for 

 132,000 v. systems is referred to, and the paper closes with -a discussion on the 

 difficult, but important, problem, the assessment of cable quality. 



Mr. H. W. Clothier. — Swifchgear for Alternating Current. 



After a reference to the comparatively recent rise of the science and industry of 

 switchgear, the paper proceeds to indicate the distinction between Continental, 

 American and British designs and to state the general tendencies of present-day 

 developments in America and in Great Britain. Future designs will be controlled 

 by the results of research on outstanding problems ; and the paper therefore states 

 some of these problems and their lines of solution as an avenue to a forecast of the 

 future. The problems dealt with are those of: (1) Insulation, under the headings 

 (a) general, (6) need for care in manufacture, (c) material for abnormal conditions, 

 and (d) cable insulation ; (2) Relief to operators, with special reference to means of 

 ensuring safety and accuracy of operation ; (3) The breaking capacity of circuit- 

 breakers ; (4) Metal-clad auxiliary apparatus ; (5) Measurement of currents in high- 

 voltage circuits ; (6) Economy, as influenced by various factors ; and (7) The draw- 

 out feature in metal-clad switchgear. The essentials for safety in all electrical plant 

 and devices are : (1) Complete enclosure of all conductors when alive ; (2) Effective 

 earthing of all accessible metal which may otherwise become alive by accident ; and 

 (3) Easy and safe means of isolation of moving parts for inspection and maintenance ; 

 and illustrations are given to show how these fundamental principles are applied to 

 switchgear, ranging in size from a domestic plug up to the very largest circuit breakers 

 for super-power stations. The paper concludes with a reference to possible lines of 

 future development, stressing especially the primary need for absolute freedom from 

 failure in switchgear if it is to fulfil its function of protecting the supply against break- 

 down or interruption. 



Mr. F. Muroatroyd. — The Mechanical Strength of Metal-Filament 

 Electric Lamps. 



The mechanical strength of metal-filament lamps is a matter of primary 

 importance to many users, some of whom may purchase each year thousands of lamps 



