Optimally testing numerical multi-function generator protection elements

A numerical generator protection relay provides multiple functions and typically uses algorithms that do not work on the same principles as older electromechanical relays. Often relay test personnel still want to use old test methods developed long ago for electromechanical relays. Test results obtained from these old test methods may not be a good indication of whether or not the numerical relay protection functions properly. One such obsolete technique still often used is referred to as a static test. Fault voltage and/or fault current are injected to see if the selected protection function operates at the setpoint and is in tolerance. Many protection functions have dynamic characteristics and/or hidden features that cannot be properly tested using a static test. This paper demonstrates various techniques how to test numerical protection relays such as dynamic tests.