Analysis of the Impact of Distributed Generation on Relay Protection Operation in Distribution Networks

Abstract

Relevance: the modern global power industry is undergoing a transformation from centralized generation systems to distributed ones with a high share of renewable energy sources (RES). This process is driven by the global environmental agenda and the need to reduce greenhouse gas emissions under the Paris Agreement [1]. In recent years, the Republic of Uzbekistan has made significant progress in transforming its energy sector. According to IRENA statistics (2026), the country's total installed RES capacity reached 10,027 MW by the end of 2025, compared with only 1,883 MW in 2016 [2]. The Strategy for the Transition of the Republic of Uzbekistan to a "Green" Economy for 2019–2030 and subsequent documents set the principal goal of increasing RES capacity to 27 GW and raising the share of "clean" energy in the overall energy balance to 40% by 2030 [3]. By the end of the decade, the population is expected to grow to 39 million and electricity demand to reach 120 TWh [4]. Implementing these plans entails the large-scale connection of solar and wind power plants to existing radial medium-voltage networks (6–35 kV). However, these networks, which account for more than one hundred thousand kilometers of lines in the assets of JSC "Regional Electric Networks," were originally designed for passive operation with a unidirectional power flow from the system substation to consumers. The connection of RES installations turns such networks into active systems with multiple supply sources, which violates the basic operating principles of relay protection and automation (RPA) systems. Therefore, it is relevant to analyze the impact of renewable energy sources (RES) on the operation of relay protection, with the aim of developing effective algorithms for setting protection systems in networks with distributed generation.

Aim: is to analyze the impact of RES-based power plants on short-circuit (SC) current parameters and on the operation of relay protection in distribution networks under changes in the direction of power flow.

Methods: modeling and calculation of SC currents in DIgSILENT PowerFactory, and determination of overcurrent protection (OCP) settings.

Results: a comparative analysis was performed, revealing a substantial influence of distributed generation on the operation of relay protection in distribution networks, which calls for the development of adaptive protection-setting algorithms.