This work reviews important concepts related to power system dynamics focusing on voltage stability. Mechanisms inherent to this phenomenon are investigated using an extended transient stability program. Through time domain simulations, it is shown stability scenarios involving under-load tap changers, overexcitation limiters, thermostatically controlled loads, loss of synchronism, partial voltage collapse and total voltage collapse. Remedial actions against voltage collapse are also implemented and tested. The computer simulations are carried out using an equivalent model representing the Brazilian south-southeast power system.