Automatic voltage regulators

P2. Patehett, G. N., Automatic Voltage Regulators and Stabilizers. Pitman, London, 1954. 

Details of special devices such as transducers, automatic voltage regulators, synchronising schemes, fault limiting reactors, reduced voltage motor starters, busbar trunking. 

The terminal voltage of the main generator is measured by the use of a voltage transformer connected across two of the stator lines, e.g. LI and L2. The signal is then rectified and smoothed in the automatic voltage regulator (AVR), by a circuit that incurs a small time constant Tr. ... 

Figure 4.1 Control system for the automatic voltage regulation of a synchronous generator.

Table 4.3 shows typical per unit values for the gains, limits and time constants used in the automatic voltage regulation systems for generators having ratings up to 50 MW. 

The time constants and gains of the control systems used in the automatic voltage regulators, governors and prime-movers. 

The control systems for the governors and automatic voltage regulators can be chosen from standard IEEE forms or can be built up separately to any degree of detail necessary. 

Association of Short-circuit Testing Authorities. American Society for Testing and Materials. Automatic voltage regulator. 

Figures D.3 and D.6 show the responses of frequency in the first one second. Both machines respond in much the same way in the first half second. This is dne to the fact that this part of the response is open loop and is mainly determined by the mechanical inertia and the size of the disturbance, as discussed in Chapter 21 of Reference 1 see also snb-section 2.5 herein. Also shown in these two figures are typical setting levels for underfrequency (81) multi-stage relays. In addition to the setting levels the relays shonld also have time delay settings, so that coordination with other power system equipment can be achieved, e.g. automatic voltage regulators of generators, automatic re-acceleration of induction motors, see also sub-section 7.6 herein. For the settings shown the relays would respond in the range of about 70 to 150 milliseconds, which is typically about half the response...

The associated equipment consists of a solid-state automatic voltage regulator that controls a thyristor converter which in turn supplies the generator field via a field circuit breaker, generator slip rings, and brush gear. The main power output from the generator to the step-up transformer is by means of a forced air-cooled, isolated phase bus duct, with tap offs to the unit service transformer, excitation transformer, and potential transformer cubicle. 

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