Automatic Voltage Regulation (AVR)

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Automatic Voltage Regulation (AVR)

These following ways of voltage regulation. First two are performed on the transformer, while third way is on the relay system in the power substation.

  1. Off Circuit Tap Changer
  2. On Load Tap Changer
  3. Automatic Voltage Regulation (AVR)

Automatic Voltage Regulation (AVR)

The tap-changer is installed to meet voltage variation in the systems connected to the transformer. It is not certain that the goal would be to maintain a constant secondary voltage at all times.

However, certain functions for coordination between different transformers in the same station are part of the tap-changer technology. When different transformers are directly parallel connected their tap-changer should move in step with each other. This is arranged in such a way that one is wired as a master and the other as a slave.

Absolutely simultaneous operation will not be achieved but there is a small interval with circulating current between the two transformers. This is however without any practical importance.

Voltage Regulation

An Automatic Voltage Regulation takes in a range of voltage levels and automatically outputs a voltage with a much narrower range of voltage levels.

For example,

a typical automatic voltage regulator for power quality application may have an input voltage range of +10% to -25% of the nominal input voltage and convert this to a regulated voltage range of +3% to -3% of the nominal output voltage as shown the graphic for a 480V input and output.

A voltage regulator may have a symmetrical input voltage range (e.g. +10% to -10% of nominal voltage) or an asymmetrical input voltage range as shown in the example.

The choice of symmetrical versus asymmetrical input voltage range is dictated by purpose and design of the voltage regulator. The output voltage regulation range is almost universally symmetrical (e.g. +3% to -3% of nominal output voltage).

A voltage regulator may also perform a voltage step up or step down function whereby the nominal incoming voltage is transformed to a different output voltage level (e.g. a step up from a 208V input to a 400V output).

For a voltage regulator with step up or step down capability, the input and output voltage ranges are usually applied to the input and output voltages (e.g. the example would become 208V +10/-25% on the input voltage range and 400V +3%/-3% for the regulated output range).

Reference // Electrical Engineering portal & utspower

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