Voltage collapse-experience and modelling

The problems found in the control of voltage will depend on the geography of the power system (relative location of power sources and demand, terrain), demand levels and the development stage reached, for instance, the type and amount of reactive power compensation. The risk of voltage collapse, which in some circumstances can occur at near normal operating voltages, may be the factor determining power transfer limits with significant implications for operation and planning. This has led to considerable work on the estimation of maximum power limits set by voltage conditions and on the detection of critical conditions. Most of these applied studies have used a steady state approach, but there has also been great interest in theoretical issues, e.g. what are the dynamics of voltage collapse and what are the advantages of using a dynamic approach, to what extent can steady state techniques be relied on. Another important issue is the impact of demand characteristics, on voltage behaviour