Some aspects of the digital implementation of protection time functions

A basic model for implementing protective time functions is reviewed and the factors affecting coordination when using relays representing different technologies are analyzed. A simple test based on a mathematical expression is presented as a means of assessing the dynamic performance of a relay with respect to varying input signals. Factors affecting the precision of digitally implemented time functions are analyzed together with sources of errors with respect to time computation. Tests presented indicate that conventional relays match the proposed ideal model