Utilization of a mixture of CTs and current sensors in line differential protection applications

Abstract

The popularity of Rogowski sensors is increasing due to their advantages over conventional CTs. Consequently, network utilities may sometimes end up facing a question whether it would be possible to use line differential protection on a line where the current measurements at the local end are based on CTs, whereas, the remote end measurements are based on current sensors. The main challenge in the use of such a combination in line differential protection applications is that while CTs may saturate, Rogowski sensors do not. Such issues were studied in a hardware-in-the-loop simulation setup. Based on the studies conducted, it appears that the use of mixture of CTs and current sensors for line differential protection applications is a feasible option provided that the CTs are properly dimensioned and that the protection settings are carefully chosen.