High-voltage D-C. railway practise

During the past 10 years, the operation of electric railways at d-c. voltages of 1200 and 1500 has become common and higher voltages have been shown to be practicable. The paper deals first with the fundamental differences in apparatus for 1200 or 1500 volts as compared with the former 600-volt standards and indicates the apparent tendency of general practise with regard to a number of alternative constructions which must usually be considered in each specific application of these systems. Referring then to the use of higher d-c. voltages which is just beginning, it points out the tendency to reach an ultimate maximum by employing a multiplicity of voltages differing but slightly from each other, such as 2400, 3000, 3600, 4200, etc, for successive installations. It recommends, in order to avoid the confusion which must surely result from this, that efforts be made to establish at once a single standard for high-voltage lines. The paper shows that final standards in voltage are usually fixed by broad economic considerations rather than by physical limitations and suggests that 5000 volts direct current would offer a very satisfactory voltage for such a standard if commercial apparatus for this voltage were available. Finally, it touches briefly upon the operation of the experimental 5000-volt line at Jackson, Michigan, which has been so successful as to give great hope that the system will be commercially developed.