The problem of numerical simulation of digital protective relay and its analog–digital (hybrid) solution

Penetration of renewable energy sources (RES) significantly changes operating modes of electric power systems (EPS) and has an unpredictable effect on operation of relay protection devices (RP). That is a reason, why the existing methods for calculating RP’ settings need to be updated. The authors carry out research and studies focused on development of new methods and means for RP setting up. The feature of the author’s approach is application of detailed mathematical models, reproducing processes simultaneously in the whole RP’ scheme, including primary transducers, and hybrid real-time simulator (HRTSim), implementing methodically accurate analog–digital (hybrid) solution of EPS model. Within the framework of the problem solution, a mathematical model of measuring part of digital protective relay was synthesized and its research was carried out in MATLAB. It is revealed that numerical methods for solving differential equations are badly applied for solving even simple mathematical models of RP, which is manifested in the obvious distortion of the simulation results. Using hybrid approach, a software–hardware mean was created and its test was carried out that showed no distortion of the output simulated signal. In addition, the operation of numerical transformer differential protection was studied via this mean.