MODERN RELAY PROTECTION: AN ADVANCED METHOD OF RELAY COORDINATION

Abstract. This paper attempts to consider the prerequisites for creating an advanced method of accelerated relay coordination, designed to improve the reliability and speed of relay protection of power systems.

Keywords: power system, electric power industry, relay protection, relay coordination, protection reliability, evolution method.

Researchers have resorted to the following different mathematical methods and algorithms to solve problems of this nature: differential evolution method, particle swarm algorithm, simplex method, genetic algorithm, etc. [3, p. 213]. However, their application in practical optimization of proper relay protection is time-consuming or difficult at all, which raises the problem of accelerated and qualitative relay coordination. This problem acquires an even larger scale in the context of power supply intellectualization, where higher requirements are imposed on relays for efficient and correct protection coordination [1, p. 185]. Evolutionary algorithms could solve the problem, but their results and computation time are, unfortunately, correspondingly inefficient and unsuitable for the required conditions.

In order to overcome the problem of optimal solution strategy algorithms and provide efficient solutions for current state-of-the-art and future smart grids, an advanced ODR coordination method characterized by simplicity, practicality and an accelerated computation process is presented in [4, p. 614]. The method allows it to be implemented in evolutionary algorithms as a patch to achieve global values in optimization processes.

In this study, the introduction of a bounded target function allows to formulate the relay coordination problem. The latter is an operation time function that is divided into two separate components, which makes it possible to reduce the complexity and dimensionality of the mentioned constraints, in the sense that each of them is optimized separately with reduced constraints.

The effectiveness of the proposed method is verified in the study through its application to two specific systems with 12 and 24 ODRs, where the analysis of their faults as well as power flows is carried out in the power system simulation software DigSILENT, and the data in the MATLAB computer package. The target functions in the work are solved by the proposed methodology, the results are compared with the TSA and PSA, confirming that the simplicity of solving the problem is due to the separation of the target function into isolated parts, which ultimately eases the computational burden of relay coordination and improves the characteristics of the relay protection scheme.

The complexity of relay coordination in large-scale power systems causes a large number of computational operations, the research of simplification and acceleration problems of which led to the development of the accelerated coordination method proposed in the above study. This advanced approach allows to solve problems of this kind more qualitatively, in the sense that optimization algorithms within the considered method are characterized by better convergence, selecting those relay settings that can provide the proper quality of relay protection reliability in large-scale power systems and power grids of intelligent type [2, p. 95].