Design of the electrical network for several district substations in the Uray Urban District, Khanty-Mansi Autonomous Okrug – Yugra.

During the course of the final qualifying work, the set objectives were met, and the following key results were obtained.

An analysis was conducted regarding the current state and development prospects of the electrical networks in the Uray urban district. It was determined that the Uray energy district faces a power deficit, with electricity supplied from external sources via 500–220 kV lines. The key supply hub is the 110 kV "Uray" substation—commissioned in 1969 and equipped with two 26.25 MVA transformers—which necessitates equipment modernization. The presence of Category I and II reliability consumers was identified, including an oil refinery, healthcare and educational facilities, and heating plants; this requires the use of network configurations featuring redundancy and automatic reserve transfer capabilities.

Based on a technical and economic comparison of options, the configuration of the proposed 10/0.4 kV electrical network was justified. The adopted circuit designs account for consumer reliability categories and ensure the required level of power supply reliability. Active and reactive power balances were calculated, and the types, ratings, and installation locations of compensation devices were determined to ensure standard voltage levels for consumers.

Power transformers were selected for the planned district substations. The specifications for 10/0.4 kV packaged transformer substations (with transformer ratings up to 630 kVA) were determined based on calculated loads and projected urban development. Conductor cross-sections for overhead and cable lines were selected according to economic current density criteria and verified against heating limits, mechanical strength, and permissible voltage drop, taking into account the region's climatic conditions (specifically, ice and wind loads). Calculations of steady-state electrical operating conditions confirmed the throughput capacity of the designed network and verified that consumer voltage levels remain within regulatory limits across all analyzed scenarios. Short-circuit current calculations made it possible to verify the selected electrical equipment for thermal and dynamic stability, as well as to determine appropriate settings for relay protection and automation devices.

Schematic diagrams were developed for the 10 kV and 0.4 kV switchgear, utilizing modern factory-assembled switchgear units that ensure safe maintenance and ease of operation. Relay protection and automation measures were proposed, including protection for transformers against internal faults and overloads, as well as automatic transfer switching (ATS) systems on the 0.4 kV side for Category I consumers.