Analysis of the Behavior of Digital Protections of Transmission Lines When Subjected to Frequencies Outside the Operating Range, in a Real Case

This paper reports on the improper operation of the overvoltage protection, in a real case, due to the estimation error of its phasors, when the frequency of the voltage signal was not compatible with the sampling frequency. It was possible to observe the recovery time of the frequency tracking signal. The results obtained by applying the simulation of the occurrence in the IED are also illustrated, as well as an analysis of the concepts applied in the calculations of the IED phasors. Thus, the conclusion is presented by exposing the solution adopted for the referred problem.