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Design, Construction and Commissioning of a Rooftop Photovoltaic Power Plant 66 kWp for VIR-90 Ltd


  • duration:
    Mar 2022 – June 2022
  • Budget:
    45 500 EUR

Project site

VIR-90 is located in Sofia.

Project scope

The current project concerns a photovoltaic power plant with an installed capacity of 66.01kWp, built on the roof of a production hall.
For the conversion of solar energy, highly efficient monocrystalline modules (panels) generating constant voltage are used. 161 units were used to obtain the installed power of the plant. panels with a nominal power of 410Wp each, mounted on the roof on a factory structure made of aluminum profiles, fastened to it with fasteners.
The DC voltage obtained from the panels is converted into AC by 2 specialized three-phase solar inverters. To form an optimal voltage at the input of each inverter in order to increase the overall efficiency of the system, the photovoltaic panels are connected electrically in series in groups of the so-called thongs.
The inverters are installed indoors in the production hall, and are connected to the so-called GRT-FET-0.4kV, which is installed right next to them.
The GRT-FET and the Inverters form a 0.4kV electrical system ensuring the inclusion of the Photovoltaic Power Plant in parallel with the power system. The inverters are equipped with the necessary voltage protections (minimum voltage) preventing operation of the FEC in “island mode”, i.e. automatic shutdown of the plant in the absence of voltage in the power distribution network. Inverters limit the appearance of higher harmonics in the electrical network. GRT-FET 0.4kV is equipped with the necessary protective equipment, providing maximum current protection, overload protection and overvoltage protection.