Trends in adaptive distance protection of multiterminal and double-circuit lines

With the changing technologies in the field of power system relaying, new protection concepts addressing new technologies are coming to the market. Therefore we need to keep track of international experiences and activities taking place in the field of modern protective systems. This paper gives a bibliographical survey, mathematical formulations, and general backgrounds of research and developments in the field of protection of multiterminal lines and double-circuit lines during the past 50 years, based on more than 100 published articles. Different techniques for parallel line protection and various methods for multiterminal lines are studied and an evaluation of them is undertaken with their advantages and disadvantages for identification of optimum technique as applied to specific applications. At the end, the philosophy of a new adaptive digital distance relaying scheme is also conceptualized. The collected literature has been divided into many sections so that new researchers do not face any difficulty in carrying out research in any specific area of the next generation's adaptive distance protection.