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Power System Voltage Stability

Understanding the voltage instability phenomenon and its effects in detail facilitates the research community to develop methodologies that can detect instability in a timely manner. Traditionally voltage instability in the system is identified through P-V and Q-V curves that are plotted using repetitive runs of load flow programs. It is observed that voltage stability is affected by the load dynamics, voltage control devices like OLTC, and hitting of over excitation limiters of the synchronous generators. In the following sections of this chapter, the concept of voltage instability with P-V and Q-V curves, load restoration mechanism with on load tap changer (OLTC), and with different types of loads are briefly presented.