Artificial Transmission Lines With Distributed Constants

Abstract

Artificial transmission lines have been very valuable in developing the theory of transmission of power. This theory has been developed in great detail for steady state conditions, and it is now important to extend it to cover transient conditions. This can best be done upon artificial transmission lines but the usual lumpy type of line introduces parasitic reflections caused by the discrete units of inductance, and therefore are of very limited use for this purpose. Attempts have been made from time to time to produce artificial lines with distributed constants, but the results were either unsatisfactory or expensive and bulky. A method, originally proposed by Pupin, has been developed by which small compact and cheap artificial transmission line coils can be designed and built to represent any desired configuration of circuit. These involve tinfoil wound in with the wire between the different layers, insulated from the winding by the usual form of condenser dielectric paper. One of the most difficult parts is to arrive at a coil with the proper constants. Formulas have been derived for doing this which will calculate the result given by the coil within the limits of manufacturing error, and which can be used in a straightforward manner similar to the design of other electrical apparatus. Either single or polyphase lines may be represented, and a single-phase line representing the average configuration of a 110,000-volt line approximately 1000 miles (1600 km.