Inverse time overcurrent relays using linear components

Inverse time overcurrent relays with various time-current characteristics are required for matching the characteristics of other protective devices and thermal characteristics of the protected equipment. The authors have presented, in this paper, a method wherein any time-current characteristic curve of overcurrent relays can be synthesized from small segments which are realized using only linear components and, therefore, follow a simple and definite mathematical law. Since, in the proposed approach, the characteristic curve is not obtained by fitting nonlinearities of components into it, the accuracies with which the characteristic can be produced and repeated both are very high.