Unwanted trip probability estimation of digital protection relays using time-domain simulations

This paper revisits the concept of hidden failures in cascading outages. It presents a new methodology to evaluate the probability of hidden failures of protection relays in power systems. Given that most of the proposed models describing the probability of unwanted triggering of relays have been developed considering electromechanical relays that are being phased out, there is a need to propose a new methodology to quantify this probability for digital relays. This paper proposes a framework which relies on time-domain simulations of power system components, including digital relays. Preliminary results show that the probability of unwanted trips is correlated to the load level at the adjacent node, meaning that a uniform probability of unwanted trips is not an acceptable model for this hidden failure mode.