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BELL SYSTEM TECHNICAL JOURNAL 



from about 0.5 to 4 per cent of the capacitance between line wires. 



Values of the capacitance of 165-, 128-, and 104-mil pairs in space and 

 on a 40-wire line are given in the following table: 



As before, values are given for pairs having wire separations of 8, 12, 

 and 18.25 in. These values include an allowance for the dry weather 

 capacitance of the insulators. The difference between the values in 

 space and on a 40-wire line indicates the importance of the effect of the 

 other wures, the insulators, etc., upon the capacitance. The capaci- 

 tance values given in the table are fairly representative of the values 

 that will obtain on well transposed lines. 



The values of inductance and capacitance which have been given are 

 based on the assumption that the nominal separation between wires is 

 preserved throughout the entire line. This is not the case when drop 

 bracket transpositions are employed. As has been pointed out, the 

 wires are brought closer together at the drop brackets, thereby in- 

 creasing the capacitance and decreasing the inductance. The amount 

 of the change in inductance and capacitance due to this cause ranges 

 from 1 to 5 per cent for the transposition arrangements designed for 

 carrier system operation. 



Leakage Conductance 



The leakage conductance per unit length of circuit, which is repre- 

 sented in the transmission formulas by the symbol G, is by far the most 

 erratic of the primary constants. Since it is a momentous factor in 

 the attenuation its investigation has been very actively prosecuted over 

 a considerable period of time. 



The determination of the value of G for direct current is quite simple, 

 involving merely a measurement of the actual conductance between 

 wires for a length of circuit short enough to avoid propagation effects. 

 For alternating currents, however, it is customary to employ an 

 equivalent value of G which includes all of the losses suffered by the 



