138 
The N.Z. Journal of Science and Technology. 
[Mar. 
Tables. 
In this paper the rotation of time proceeds clockwise, so that the 
angles advance counter-clockwise according to the usual convention: 
thus if the current lags behind the E.M.F. in time the phase of the E.M.F. 
is in advance of the phase of the current, and if the position of the 
current be taken as a datum and the E.M.F. is 30° in advance the position 
is represented thus /30° O'. If the current is in advance of the E.M.F. 
by 30° the position is represented thus \30° O'. This convention is 
adopted in the annexed tables, which give the values of essential functions 
in the equations for a number of sizes of cables which are found to be 
generally useful in departmental work :— 
(1.) Evaluation of the attenuation factor m and the surge impedance 
factor n for 10 ft. spacing. 
(2.) Evaluation of the attenuation factor m and the surge impedance 
factor n for 9 ft. and 8 ft. spacing. 
(3.) Evaluation of the attenuation factor m and the surge impedance 
factor n for 7 ft. and 6 ft. spacing. 
(4.) Values of cosh Im and sinh Im for 100, 150, 200, and 250 miles 
for 10 ft. spacing. 
(5.) Values of cosh Im and sinh Im for 100, 150, 200, and 250 miles 
for 9 ft. spacing. 
(6.) Values of cosh Im and sinh Im for 100, 150, 200, and 250 miles 
for 8 ft. spacing. 
(7.) Values of cosh Im and sinh Im for 100, 150, 200, and 250 miles 
for 7 ft. spacing. 
(8.) Values of cosh Im and sinh Im for 100, 150, 200, and 250 miles 
for 6 ft. spacing. 
(9.) Calculations of 100-mile transmission at 100,000 volts. 
(10.) Calculation of corona loss. 
The tables will enable any one to calculate all the electrical properties 
of a transmission-line with facility for such spacing and sizes of cable as 
are in ordinary use. 
Calculations. 
An orderly arrangement of the calculations is helpful and useful for 
reference, and Table 9 is presented as an example of a calculation of 
a typical transmission-line case and of a form of tabulation. The cal¬ 
culation is for a transmission of 13,500 kw. delivered to a substation 
100 miles distant at 100,000 volts between phases on a three-phase 
circuit. The calculations are in terms of the voltages to neutral and 
of the power per phase. The power factor at the substation is taken 
at 95 per cent. This high value is not attainable without special 
means, such as the use of synchronous condensers at the substation 
end. The usual power factor obtained from a mixed power-supply 
system at maximum load is between 83 per cent, and 86 per cent, if 
uncontrolled, which considerably limits the power which may be trans¬ 
mitted with good regulation. 
A great deal of improvement is effected by making special contracts 
with customers for the employment of synchronous motors and of static 
