From voltage stability point of view, maximum permissible loading limits must not be exceeded in the operation of power systems. The risk of cascading outages in power systems manifests itself in a number of ways like loss of generation units, breaker failures, common tower and common right-of-way circuit outages, combination of system conditions and events. With the advent of structured competitive power markets, and with the lack of needed investment in the transmission grid, electric power systems are increasingly being operated close to their limits. When a power system is subjected to large disturbances control actions need to be taken to steer the system away from severe consequences and to limit the extent of the disturbance. The main factor, which causes these unacceptable voltage transients, is the inability of the distribution system to meet the demand for reactive power. The major research in dealing with voltage collapse is the proper diagnosis of the underlying factors causing low voltage. These disturbances often result in voltage collapse of the system, which in turn causes huge losses in the system as well as monetary losses. This paper deals with some newer techniques for the prevention of the voltage system collapse for voltage system collapse, which may have a very large economic impact on the society. It also focuses on right initiation at right time to ease control action to enhance stability, reliability and security of the power system so as to provide a preventive plan to minimize the chances of failure in power system as possible.