On-line estimation of available generator reactive power for network voltage support

This paper discusses a method to evaluate the available reactive power of individual generators that could be deployed to support voltage in the power network. The method is based on real time calculation of reactive power capability limits of the generator (i.e. modification of generator capability chart) taking into account limitations imposed not only by loadability thresholds of generator components but also by performance thresholds imposed by generator auxiliary equipment. It is demonstrated that the actual reactive power support that generator could provide to the network can be substantially reduced compared to the value indicated by the standard generator capability curve provided by the manufacturer at the time of commissioning of the generator. The proposed method enables full utilisation of actual available reactive power of individual unit, and consequently of the entire power plant, to support voltages in transmission network.