80 Scientific Proceedings^ Royal Dublin Society. 



jr , _ Fi a + i(i 



'2 — — r "; = -p 7T, = a + It. 



cosh ml s + ^c 





(5) Ddermiimtion of corona loss. 



For a single-phase or symmetrical three-phase system 

 7 = 1 for polished round wires, 



= '98 to -Qo for roughened or weathered wires, 

 = '87 to 'So for seven-strand cables. 

 „ _ 9-96A 

 " 273 + ff 



F„ = 123,400 ygalogio- volts. 

 Loss Q = 5-53 X -^ X I* X ( F - V,)- x ID"" watts per line. 



12. When the line is comparatively short and the voltage not especially high, 

 the capacity and leakage of the line may be neglected. The calculations then 

 become greatly simplified. The efficiency and regulation are calculated by the 

 following formulte : — 



13. Illustrations will now be given of the procedure in particular cases. It is 

 convenient to follow the routine arrangement of the calculations employed below. 



(1) Dcda for one line. 



Line, symmetrical three-phase. 



Frequency, oO cycles per second. 



Voltage between wires at receiving end, 66,000 volts. 



Greatest power delivered, 8,250 kw. 



Power factor of load, cos ^ = "85. 



Effective average value of current delivered throughout a year, 31 amps. 



per phase, being 1'225 x mean amps, for year, since the load- curve is 



approximately equivalent to a sine-curve in which h' = h. (See 



paragraph 8.) 

 Length of line, I = 25 miles. 



Conductors of copper, spaced h = 108 inches mutually apart. 

 Cost of conductor material, 2 = 15 pence per lb. 

 Interest and depreciation rate thereon, r = -08. 

 Value of power, s = 1 penny per unit. 

 Average atmospheric temperature, Q = 20° C, and barometric pressure, 



li = 30 inches. 



