Qualitative Analysis of Transmission Lines

Abstract

The process proposed in this paper is called ``Qualitative Analysis of Transmission Lines'' because of its similarity to chemical qualitative analysis. Based upon a previous presentation by Mr. Percy H. Thomas the ``critical load'' for transmission lines is introduced with a simple formula for determining it and various rules are given for the variation of power factor voltage, etc., of a line by relating the actual load to the critical load. The most important parts of Mr. Thomas's presentation are abstracted and presented showing the fundamental physical and mathematical basis for this method of analysis. The detail development of the formula for the critical load is then given and the effect of the various line constants upon it are briefly discussed. Working from the critical load a vector interpretation of the action of a long high-voltage transmission line is given. From this vector interpretation it is possible to predict certain essential operating characteristics of transmission lines. Based on the previous generalities practical examples of transmission lines operating at critical load are then given showing how it is possible by the qualitative analysis to predict desired conditions of operation. Two of these examples show the operation of a 3100 mile copper transmission line of 220 kv. nominal potential. Another shows a 3875-mile aluminum transmission line. In the conclusion an appeal is made for further work along these lines and it is pointed out particularly that this is not an approximate method but an exact method for ``Qualitative Analysis of Transmission Lines.''