Digital Automatic Voltage Regulator(D-AVR) TOSATEX1000
Functions

• Automatic Voltage Regulator (AVR)

The automatic voltage regulator (AVR) maintains the generator terminal voltage at a constant level.

• Manual Excitation Control (MEC)

The manual excitation controller (MEC) maintains the field current at a constant level.

• Under excitation Limiter (UEL)

The UEL is used to limit under excitation of a generator during AVR operation. The UEL gives the "excitation increase" signal to the AVR when the generator is excited below a set point. (Fig. 2 shows the limiting characteristics of the UEL.)
• Over excitation Limiter (OEL)

The OEL is used to protect an excessive temperature rise caused by over excitation of a generator during AVR operation. The OEL sends the "excitation decrease" signal to the AVR when the excitation exceeds a set point.
• Overexcited Reactive-power Limiter (OQL)

The OQL is used to limit the reactive power (reactive current) of a generator during AVR operation, thereby limiting over excitation of the generator.
The OQL sends the "excitation decrease" signal to the AVR when the reactive power (reactive current) exceeds a set point.
• Voltage-per-Frequency Limiter (VPFL)

The VPFL is used to prevent the main transformer from over excitation by limiting the V/F value of a generator during AVR operation. The VPFL sends the "excitation decrease" signal to the AVR when the V/F value exceeds a set point.

Optional Function
In addition, the followings can be added with customer's requests;

• Cross Current Compensator (CCC)

The CCC gives the voltage dropping characteristic against reactive current to a generator under AVR operation, for stable parallel operation and proper distribution of reactive power.
• Line-drop Compensator (LDC)

The LDC supplies the compensation signal corresponding to a line drop to the AVR to maintain the voltage at a constant level at a fixed point in the transmission line
• Power System Stabilizer (PSS)

The PSS expands the dynamic stability range of the parallel operation of a generator with a power system.
When power deviation is detected in the generator, the PSS quickly suppresses it by controlling the excitation.
• Automatic Reactive-power Regulator (AQR)

The AQR automatically regulates the reactive power (in stricter forms, reactive current) of a generator. The reactive-power can be regulated to a value given by the following equations:


Q = a (constant reactive power control)
Q = b • P (constant power factor control)
Q = a + b • P (combined type of the above two)


57R (setting parameter "a") and 55R (setting parameter "b") are of the manual setting type normally, but the remote setting type is also available.