Design and construction of two complete transformer stations to supply charging stations, design and construction of cable routes to charging stations


Troleybusni & Avtobusni Prevozi EOOD (Trolleybus and Bus Transport)

Stara Zagora, Region of Stara Zagora

Assigned: April, 2022/ Completed:  January, 2023


Contract has been awarded under Operational Programme ‘Environment 2014-2020’, project proposal ‘Implementation of measures to improve quality of life in the city of Stara Zagora’, priority axis ‘Improving air quality’.

EL KONTROL was selected as the contractor for implementation of this project proposal, which includes elaboration of detailed design, execution of construction, and designer supervision during construction.

In terms of classification, it belongs to infrastructure construction carried out in an urban environment.

Project is related to provision of 33 new electric buses by the Municipality of Stara Zagora. Vehicles operate through 18 double charging stations.

To power supply the charging stations, we constructed a concrete complete indoor switchgear (CCIS) fed from two different sources. Two concrete complete transformer stations (CCTS) were also constructed: CCTS 2 - 2 x 1000 kVA 20/0.4 kV, and CCTS 3 - 2 x 800 kVA 20/0.4 kV, together with associated medium and low voltage cabling.

Scope of activities completed under the project:

- Elaboration of detailed design;

- Construction and equipping concrete complete indoor switchgear (CCIS);

- Construction and equipping two concrete complete transformer stations (CCTS);

- Construction of 20 KV cable lines from external power supply points to the CCIS, and to the two CCTS respectively, including supply and installation of LV cables;

- Construction of reactive power compensation system for each of the two power supply lines;

- Construction of conduit cable routes for LV cables – from the LV panels in the CCTS to the charging stations;

- Construction of 0,4 kV cable lines including supply, laying and connection of LV cables - from the LV panels in CCTS to the charging stations;

- Construction of earthing installation and lightning protection installation for the charging stations;

- Construction of foundations for the charging stations;

- Construction of automatic load transfer on the LV side of the power supply, construction of emergency signalization;

- Control tests and commissioning of the installed equipment and facilities;

- Designer supervision during construction.