In March 2022, the guarantee measurement (GM) of the refurbished TG2 unit at the Vacha hydroelectric power plant in Bulgaria was carried out. The unit was measured at current head using the Gibson method of flow measurement. In addition to the measurement of energy parameters, the GM also included the measurement and evaluation of vibration, pressure pulsation and noise.

A very important input parameter for the Gibson method is the so-called penstock factor, for the calculation of which it is necessary to know precisely the lengths and diameters of the sections entering the calculation. Due to the riveted construction of the penstock at the HPP Vacha where the length of the sections alternates between the overlaid and the overlaying sections of about 3 m, and for different pressure sections, the determination of this factor was very challenging.

The measurements showed compliance with all guaranteed values of efficiency, maximum power, vibration and other verified parameters.