596 



BELL SYSTEM TECHNICAL JOURNAL 



longitudinal voltage to be employed would be that remaining after 

 correction for the shielding effect due to wires on which protectors 

 have operated. 



As mentioned previously, mutual shielding of the telephone wires on 

 a line may prevent the operation of some protectors, particularly on a 

 large line. Consequently, the exact analysis of the distribution of 

 voltage-to-ground of all of the wires on a large line becomes very 

 complex. Moreover, as is often the case, if impedance conditions are 

 not uniform, such as where circuits are not coterminous, the complete 

 analysis of the voltage-to-ground becomes even more complicated. 

 Under such conditions it will generally be found that the distribution 

 of voltage-to-ground along the different circuits is different, and 

 consequently, voltages exist between different wires due to these 

 differences in the voltage-to-ground. Likewise, voltages may exist 

 between wires on which the protectors have operated and wires on 

 which the protectors have not operated. 



POWER LINE 



'W 



TO AMPLIFIER — 

 AND METER — 



TELEPHONE LINE 



A-DEMONSTRATION 



r<5M/\r<JMAK2M/V<5>-AAK2M/\r<l>^ 



B- THEORY 



Fig. 15 — Voltage to ground for telephone line grounded at both ends where fault is 

 inside exposure — double-end feed. 



All of the above analyses have been made on the assumptions of con- 

 tinuous telephone wires. If a wire is opened at one point the longi- 

 tudinal voltage, reduced by shielding from any currents which exist 

 in other continuous wires, will appear across the "open." On a large 



