Ferroresonance occurrence during energization of capacitive voltage substations

Capacitive voltage substations are intended to supply electricity to rural communities directly from high voltage transmission lines. This technique leads to important cost reductions when compared with conventional alternatives using high voltage power transformers. However, some problems such as ferroresonance and overvoltages can occur in these substations during different operating conditions. The purpose of this paper is to assess the occurrence of these phenomena in the case of system energization. Some computer simulation test results are provided to highlight that the occurrence of ferroresonance depends on some parameters such as the amount of residual flux, the type of transformer winding connection, switching sequence of system energization and the initial angle of the system input voltage. Also it is shown that common ferroresonance suppression methods such as three phase simultaneous switching can not prevent these dangerous transients. At the end, some ferroresonance suppression methods applicable to these substations are described.