Rapid measurement of Stability Margin to prevent damage due to Voltage Collapse.
“Voltage stability is the ability of a system to maintain voltage so that when load admittance is increased, load power will increase, and so that both power and voltage are controllable.”
The steep rise in demand for electrical energy in recent years has compelled power systems to operate closer to their limits than in the past. This makes power systems more susceptible to instances of voltage instability. If voltage instability is not addressed timely, it may eventually lead to voltage collapse. Therefore, stability analysis has become one of the top priority concerns of electric utilities. Neglecting this issue may lead to adverse economic effects. The loss caused during the August 2003 blackout in United States was estimated to be between $4 billion and $6 billion. Hence, utility companies need to pay considerable attention to the problem of voltage instability and should adopt effective strategies to address this issue.
Insolvability of the power flow equations and loss of voltage controllability are two mechanisms which cause voltage instability in power systems. Insolvability of the power flow equations implies a situation under which at least one load violates the maximum loadability limit, and as a result the feasible equilibrium point is lost.
All the reactive power sources (Generators, SVCs, etc) that injection of reactive power at a bus will increase that bus’s voltage magnitude. If this assumption is wrong, any voltage control action will result in an opposite corrective effect on the voltage magnitude of that bus. This situation is referred to as the loss of voltage controllability.