The paper shows the role played by load tap changing (LTC) transformers, equipped with tap automatic control, in the analysis of voltage stability at the receiving end of transmission links. Owing to the slow nature of the process, voltage stability at load nodes is investigated with regard to the mid-term dynamics of synchronous generators and to the secondary voltage regulation. The importance of load models is also recognized so that voltage and frequency load characteristics are introduced and their effects on the voltage stability conditions are evaluated and discussed.