Transition Rates Assessment of Protective Relay Reliability Models With Incomplete Data

Usually the residence intervals in various states of power equipment are known, yet information about the number of transitions from one state to another is either missing or incomplete. This is mainly caused by a difficulty in recording of the state changes in the protection equipment or poor data acquisition and recording by power utilities. The transition rates are key parameters in all power system reliability models. Partial information on protection systems poses a challenge to construct or complete a transition rate matrix for reliability assessment. This paper addresses an issue of reliability evaluation of protective relays, operating in harmonic polluted environment. It presents a solution to the problem of finding transition rate matrix for a Markov chain of a simplified digital distance relay model. In this approach, the power system network and its associated protection is designed in a graphical preprocessor to Alternative Transients Program (ATPDraw). Parametric simulations of different circuit topologies during nominal and fault conditions are executed, processed, and analyzed automatically through batch and MATLAB scripts. Statistical calculations are implemented to obtain reliability parameters. An example is used to demonstrate the interactive protection system simulation, developed using the new approach.