Minimization of Financial Losses due to Voltage Sag in an Indian Distribution System using D-STATCOM

Voltage sag can cause considerable financial damage in an industry containing sensitive equipment. Many solutions exist to minimize financial losses due to voltage sag, varying from modification within the process itself to restructuring the supplying grid. In many cases the only possibility to minimize the financial losses is to install mitigation devices between the grid and the sensitive process such as power electronics devices Uninterruptible Power Supply (UPS). However, protecting the entire process by a dynamic or static UPS often turns out to be too expensive. This paper presents the minimization of financial losses due to voltage sag produced by balanced and unbalanced short circuit that occur at distribution system bus and along the transmission line using system impedance matrix (Z Bus) which incorporates D-STATCOM. The overall financial losses due to voltage sag could significantly change depending on the location of D-STATCOM used. In order to have an assessment of financial losses in real distribution systems, the classical static fault calculation should be amended to incorporate the effect of installation of these devices on financial losses. The cost-benefit analyses of inducting D-STATCOM for mitigating the effects of voltage sags have also been performed. Case studies based on a real Indian distribution system are used to illustrate the modeling method and the effectiveness of these devices in voltage sag mitigation.