Statistical approach for evaluation of current transformer saturation

摘要

Historically, power system protection schemes were performed by electromechanical relays and regime symmetrical component currents. Many modern digital relays have been installed in the last years, replacing old electromechanical solutions, but not accompanied by the current transformers (CT) substitution due to their long life span. Recently, utilities face the challenge of having to replace obsolete superseded CTs, that may cause undue trips due to saturation in the first cycles of a fault. The aim of this work is to determine a methodology to best classify and prioritize the substitution of those CTs more prone to cause problems. The approach to the problem is carried out by a combination of the statistical probability of saturation occurrence with the impact of the undue trip caused by that saturation. A case study is carried out to demonstrate the benefits of the methodology. The results show that even counterintuitive situations can be found and resolved with the present approach.