Trust in Power System State Variables based on Trust in Measurements

Modern energy systems are cyber-physical systems with increasing relevance and influence of information and communication technology. This influence comprises all processes, functional, and non-functional aspects like functional correctness, safety, security, reliability, credibility and usability. In a former work by the authors, the assessment of trust, as an umbrella for the aforementioned aspects in measurements has been researched. Furthermore, the trust aspects were integrated into a state estimation to reflect a reduced trust in measurements in a reduced trust in state variables. A major drawback of that approach is that the convergence behavior of the state estimator is affected because trust is integrated in terms of standard deviations. The approach presented in this paper uses the sensitivities of the state variables to changes in the measurements, that are calculated during WLS state estimation, to weigh the trustworthiness of the input measurements for the calculation of the trustworthiness of each state variable after the state estimation process. A high residual indicates that the respective measurement has a limited influence on the estimated state variables. Therefore, the weighing factor mentioned above is combined with a factor that takes the measurement residuals into account. A proof of concept shows that this approach does not influence the characteristics of the state estimation and that it gives a reasonable estimation for the trustworthiness of the state variables based on the trust in the input measurements. The results are compared with the results of the former approach to show the advantages of the new approach.