190 BELL SYSTEM TECLINICAL JOURNAL 



circuit conditions and under load, to study the efilects of various trans- 

 former connections on wave shape, and to observe the effects on wave 

 shape of various types and magnitudes of load. 



The measurements made included analyses of the phase-to-neutral 

 and phase-to-phase voltages and phase currents on a large number of 

 generators, transmission lines and distribution feeders. Wherever 

 practicable, data were obtained as to the balance of the operating sys- 

 tems by measurements of residual voltages and residual currents. 

 Measurements were also made of the Telephone Interference Factors ^ 

 of the voltages and currents. Where telephone circuit exposures suit- 

 able for test purposes existed, noise measurements were made on the 

 communication lines to aid in determining the relation between power- 

 system wave-shape and balance and telephone circuit noise. The 

 actual measurements were for the most part conducted by the operat- 

 ing companies with the cooperation, during the first part of the testing 

 program, of representatives of the Joint Subcommittee. 



The mass of data accumulated during this survey is being summar- 

 ized in several technical reports which it is anticipated will yield much 

 valuable information pertaining to the wave-shape problem. An 

 important practical application of these data will be in connection with 

 the prediction of wave-shape conditions on new lines which are to be 

 involved in exposures with communication systems and on which 

 noise estimates are desired. 



In general, the survey data indicate that the magnitudes of the 

 harmonics present in voltage and current diminish with increasing 

 frequency, with the exception that a pronounced dip occurs in the re- 

 gion from 800 to 1500 cycles. This is, no doubt, a result of the efforts 

 of the machine designers to closely control the harmonics in this im- 

 portant region. Frequencies above 2000 cycles become extremely 

 small except where these may be introduced on the power circuits by 

 superposed carrier communication or signaling services. In general, 

 the frequencies used for such services have been in the range from 50 

 to 200 kc, which is above the range employed for carrier communica- 

 tion on telephone lines. 



In the general survey of wave-shape, no efforts were made to select 

 feeders involved in cases of inductive interference. Aside from the 

 survey work, however, representatives of the Subcommittee have par- 

 ticipated in a number of investigations of such cases in which power- 

 system wave-shape was an important factor. Much valuable data as 

 to wave-shape conditions under which coordination difficulties are 

 experienced have been obtained from these studies, while in obtaining 

 these data the Subcommittee representatives have been of service to 

 the local companies in the solution of the particular problems. 



