Scientific paper ID 1720 : 2018/3

Due to the high percentage of MV cable lines, including a large number of idling lines (no load), there is a large consumption of capacitive power at Vrajdebna substation in Sofia. To compensate for this capacitive energy, it is necessary to install compensating shunt reactor to replace existing capacitor batteries. The paper examines the need and effect of installing a three-phase oil reactor at this substation on the side of 20 kV. The type and parameters of the reactor used in accordance with the particular characteristics of the substation are discussed. Supplementary equipment (measuring transformers, circuit breakers, etc.), as well as the need for interlocks, re-setting of the relay protections and realization of thermal protection are provided. After installation, there is a significant drop in capacitive energy and the power factor significantly improves. Compensation of capacitive energy will lead to reduction of sanctions for reactive energy transmission, improvement of delivered energy quality, reducing the additional load on the equipment due to poorly compensated reactive energy, increasing reliability and reducing capital costs. Therefore, the installation of inductive compensating devices is beneficial at the current tariff for measuring and paying capacitive electrical energy.