Discussed here is a technique for testing digital devices based on the calculation and control of two or more characteristics of a binary electric signal at a reference point. Signals coming from a healthy and failed digital device that are indistinguishable by the value of one of the characteristics may differ in value of the other characteristic. The combination of test methods can significantly reduce the potential of not detecting the failure of digital device. The technique is aimed at increasing the information content of the healthy state monitoring results and the possibility of localizing failures in digital instruments and devices of power systems.

Modern methods for analyzing and assessing the reliability of complex technical systems consider only its individual elements. The specifics of structural-functional interactions and integration into subsystems of different hierarchical levels are not taken into account. Studies show that analyzing the reliability of urban electric transport, also focus on individual components: the reliability of electric traction rolling stock, the reliability of the power supply system, the reliability of the track infrastructure, etc. The authors propose an approach that allows to consider urban electric transport as a complex technical system consisting of several levels that are hierarchically subordinate. Each level combines the components directly involved in the transmission and transformation of electric power into mechanical operation of the rolling stock under the influence of the external environment by means of traction electrical equipment. This approach will allow to develop the theoretical foundations of methods for analyzing the impact of the reliability of individual components of a complex technical system of urban electric transport on the effectiveness of the electric traction implementation.

A technique is proposed for optimization the composition of diagnostic parameters based on a combination of heuristic algorithms with the method of linear integer programming. The solution obtained using the heuristic algorithm with relatively small consumption of computational resources is taken as an initial one for optimization or checking the optimality of the composition of parameters using the linear integer programming method. The combination of a heuristic algorithm with the method of linear integer programming saves significant computational resources when searching for the optimal solution. The technique is aimed at minimizing costs when creating diagnostic support for monitoring performance and failure detection when considering the serviced and reconstructed electronic devices and equipment of power systems.