Newest protection relays, which use superimposed quantities and traveling-wave based elements to implement ultra-high-speed line protection, impose new challenges on testing. Simple injection of steady-state currents and voltages does not allow to trigger these elements. There are different possibilities to test such relays, among others a realistic simulation of traveling waves. This requires an accurate model of the transmission line, which considers the frequency dependent effects and mutual impedances for multi-phase systems correctly.
This paper describes a practical solution for testing in the field using the simulation of traveling wave pulses with the correct timing. It even enables an end-to-end test using multiple time-synchronized test devices. Synchronized to GPS clocks with a sub-microseconds precision test devices have sufficient time accuracy to test traveling-wave based elements too.