AN IMPROVED VOLTAGE CONTROL ON LARGE-SCALE POWER-SYSTEM

To achieve a better voltage-var control in the electric power transmis sion system, different facilities are used. Generators are equipped wi th automatic voltage regulators to cope with sudden and random changes voltage caused by natural load fluctuations or failures. Other device s like capacitors, inductors, transformers with on load tap changers a re installed on the network. Faced with the evolution of the network a nd operating conditions, electricity utilities are more and more inter ested in overall and coherent control systems, automatic or not. These systems are expected to co-ordinate the actions of local facilities f or a better voltage control (more stable and faster reaction) inside d ifferent areas of the network in case of greater voltage and var varia tions. They afford besides a better use of existing reactive resources . Also, installation of new devices can be avoided allowing economy of investment. With this frame of mind, EDF has designed a system called Co-ordinated Secondary Voltage Control (CSVC). It's an automatic clos ed loop system with a dynamic of a few minutes. It takes into account the network conditions (topology, loads), the voltage limits and the g enerator operating constraints. This paper presents recent improvement s which allow the CSVC to control the voltage profile and different ki nds of reactive means on a large-scale power system. Furthermore, this paper presents solution to spread out investment costs over several y ears, considering a deployment gradually extended.