This diploma thesis presents the design and dimensioning of a new transformer
substation TP Stara Cerkev šola as part of a detailed execution design (DZI) project. The
project addresses a comprehensive modernisation of the power distribution network
serving the settlements of Stara Cerkev and Konca vas in the Municipality of Kočevje.
The existing electrical infrastructure relies on two outdated pole-mounted transformer
substations—TP Konca vas (reference 01-10-10) and TP Stara Cerkev (reference 01-10-
16)—both constructed in 1977. Both substations no longer meet current power quality
standards (SIST EN 50160). Overloaded transformers, long overhead low-voltage
network routes with undersized conductors and resulting excessive voltage drops
systematically prevent the connection of new consumers and hinder the electrical
development of the settlement.
The proposed solution involves construction of a new prefabricated metal-enclosed cable
transformer substation type TEN6/24 with a 400 kVA power transformer, located on plot
232/30, cadastral municipality 1575 Stara Cerkev. The new substation will be radially
supplied via a 630 m long 20 kV cable NA2XS(FL)2Y 3×(1×150/25 mm²). Four new
LV distribution feeders with NA2XY-J 4×150 mm² cables will supply consumers in the
southern part of Stara Cerkev, the local school and the SOR distribution panel.
The thesis incorporates comprehensive engineering calculations, including: peak load
determination and transformer selection, short-circuit analysis at the medium-voltage
level (Ik" = 14.43 kA, Ip = 35.71 kA), thermal cable sizing for both MV and LV systems,
protective device settings, earthing system design (RTP = 1.38 Ω < 2.7 Ω) and voltage
drop verification. A dedicated chapter addresses the electrical cable duct system (EKK),
which facilitates future maintenance and network expansion without additional
excavation.
The thesis further addresses safety requirements, environmental considerations and
construction waste management. The analysis demonstrates that the proposed design
solution satisfies all technical and regulatory requirements and ensures long-term reliable
power supply.
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