Investigations of load-tap changer interaction

This paper explores the dynamic behaviour of loads and tap changers during the process of voltage collapse in power systems. Using an exponential recovery load model representing the dynamic behaviour of aggregate loads, the mechanism of voltage collapse is illustrated. Dynamic interaction between loads and transformers is investigated. Based on such dynamic considerations, a tap locking strategy is proposed which ensures that voltage collapse does not occur. Investigations focus on determining a critical value of tap position such that locking at a smaller value of tap results in stable behaviour, but locking at a larger value results in voltage collapse.