Indeed, transient simulation using tools like EMTP or PSCAD can be useful in field testing power system protection schemes, especially for complex networks for which traditional short-circuit simulations may provide misleading results. While short-circuit testing is appropriate for steady-state fault conditions, it has a tendency to overlook transient phenomena such as CT saturation, DC offset decay, or evolving faults that influence relay performance. Open-loop transient simulations may be employed to test relay performance under real-life conditions, particularly for distance protection, line differential relays, and protection schemes which are affected by switching transients. They are not very useful in the field test, though, because of the lack of real-time interaction and the need for special test equipment. A more realistic alternative for transient-based relay testing in the field is Hardware-in-the-Loop (HIL) testing with Real-Time Digital Simulators (RTDS), which allows dynamic testing under simulated transient events for more accurate and reliable protection scheme verification.

In my view, this is not particularly important for field tests on power system protection schemes. Transient analysis is often not even required at the stage of designing a protection system. For example, transient stability or motor acceleration studies are essential for equipment selection, but for protection and control functions, calculated values are usually applied. In protection system design, the key factors are the short-circuit currents and the equivalent impedances (X, R) at the fault locations. These can be obtained directly from short-circuit analysis. From this, the specified primary time constant (Tp) can be readily calculated, which is then used, for example, in CT saturation evaluation during CT sizing.