What is voltage collapse and how is it prevented?

Voltage collapse occurs when the system cannot meet reactive power demand, causing progressive voltage decline and potential blackout. It typically happens when the system operates near its power transfer limit and a contingency reduces reactive support. Prevention involves: adequate reactive reserves, load shedding schemes, proper VAR compensation placement, voltage stability studies, and maintaining transfer margins. Warning signs include declining voltage and high VAR generation. UVLS (under-voltage load shedding) provides last-resort protection.