Abstract

Reactive power (vars) is required to maintain the voltage to deliver active power(watts) through transmission lines. Motor loads and other loads require reactive power to convert the flow of electrons into useful work. When there is not enough reactive power, the voltage sags down and it is not possible to push the power demanded by loads through the lines. Synchronous generators are rated in terms of the maximum MVA output at a specified voltage and power factor (usually 085 or 0.9 lagging) which they can carry continuously without overheating. The active power output is limited by the prime mover capability to a value within the MVA rating. The continuous reactive power output capability is limited by three considerations: armature current limit, field current limit, and end region heating limit. During the daily operation, power systems may experience both over-voltage and under-voltage violations that can be overcome by voltage/Var control generators can generate or absorb reactive power depending on the excitation. When overexcited they supply the reactive power, and when under excited they absorb. Here we are using a single microcontroller for automatic controlling of reactive power (MVAR) flow and maintain a terminal voltage in 230 KV transmission line.

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