Abstract :
The planning of the EHV transmission system for James Bay provided Hydro-Québec with an opportunity to review the protection philosophy established for its first 735-kV system. A working group was formed in the fall of 1974 to establish a protection philosophy which would satisfy planning, design and operating criteria, in order to obtain optimum system protection and the best possible utilization of the James Bay transmission system at minimum cost. Hydro-Quebec´s committee on extra high voltage approved the recommendations of the working group1 in the spring of 1976. The purpose of this paper is to summarize certain parts of the working group´s study, particularly those relating to transmission lines, tie lines linking substations at the same latitude, and transformers. These elements of the system were chosen in order to bring out the fundamental differences in their protection.
