Alternative method for testing overcurrent protection function by using least square method finding overcurrent function parameters without prior interrogation of relay setting

A utility usually installed modern power system protection relays from multiple manufacturers and models. The testing of the relays is very challenging due to its complexity. This would increase expenses due to additional test duration and longer disturbance of power for the substation can´t be energized. Therefore a test that could be done without prior accessing the setting would be needed for faster on site test. In this study, the alternative test method and procedure for by passing the setting complexity was evaluated. The result of testing data of overcurrent protection function at optimum number of valid test points was processed to reveal the setting of the functions. The calculation provided the time multiplier setting, minimum pickup current and the curve of the setting. The result suggests a valid testing could be done without extracting preexisting function setting.