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Generator Protection System
Published in Ramesh Bansal, Power System Protection in Smart Grid Environment, 2019
One of the most important components of the generator is the excitation system, which consists of automatic voltage regulator (AVR), exciter, protection unit, etc., as shown in Figure 11.15. The exciter is designed to provide a source to the field winding of the generator. The excitation level of the generator is regulated by the application of the AVR, which is very effective during steady state operations. The original equipment manufacturers make different options to power the AVR of various generators. Numerous excitation systems are available, and each one has its own unique features and benefits based on a number of applications. The selection of the best option by the independent power provider is based on some technical and economic considerations. One of the most important components utilized in the generators are the rotating and alternator rectifier exciter rectifiers. The AVR is connected to the stator winding to regulate the level of excitation of the generator and to sustain a constant voltage at the terminals of the generator with the fluctuating load conditions. The power source of the AVR is obtained from one of the following options: self-excited, excitation boost system, permanent magnet generator and auxiliary winding. The aforementioned methods are cost-effective approaches to provide the required input power to the AVR due to their simplicity. The input power source to the AVR is mainly designed to supply a DC output to the exciter stator, and the voltage level sensor is used to determine the level at which the AVR induces a DC voltage on the exciter rotor.
Application and Protection of Medium-Voltage Motors
Published in Shoaib Khan, Industrial Power Systems, 2018
Brushless excitation has become the industry standard. A typical brushless excitation system is shown in fig. 9.12. The exciter is a brushless AC generator fitted with a rotating three-phase bridge rectifier to give a controlled DC output. The exciter is flange mounted on the nondrive end of the motor shaft. During starting, the field winding is shorted through a discharge resistor to block the DC current until the rotor is near full speed. The power required by the brushless exciter field is on the order of 100 V DC, with current ranging from 5 to 15 A.
Power Electronic Controls
Published in William S. Levine, Control System Applications, 2018
George C. Verghese, David G. Taylor, Thomas M. Jahns, Rik W. De Doncker
The exciter is the functional block that regulates the output voltage and current characteristics of a wound-field synchronous generator by controlling the instantaneous voltage (and, thus, the current) applied to the generator’s field winding. Exciters for large utility-class synchronous generators (> 1000 MW) must handle on the order of 0.5% of the generators’ ratedoutput power, thereby requiring high-power excitation equipment with ratings of 5 MW or higher [27].
Optimal Coordinated Frequency and Voltage Control of CCGT-Thermal Plants with TIDF Controller
Published in IETE Journal of Research, 2021
Satish Kumar Ramoji, Lalit Chandra Saikia
An AVR loop is imperative to maintain the voltage constancy in the generators, and the ALFC loop is vital for maintaining the frequency constancy during the incertitude nature of load [25]. The AVR loop constitutes an amplifier, static or DC excitation mechanism, generator field, and sensor. The excitation mechanism mainly accomplishes the voltage regulation as the excitation mechanism has complete control over the synchronous machine's field current. As a result, the field current is regulated in order to regulate the generator's terminal voltage. The generator's voltage is proportional to its speed and excitation [26]. The excitation mechanism will regulate the generator's terminal voltage if the speed is maintained at a constant level. The exciter is the source of excitation for the generator. The exciter is known as a DC exciter or a static exciter, depending on how DC power is delivered to the generator's field winding. This sensor senses the error voltage and can reliably calculate terminal voltage (ΔV) by comparing it with the reference voltage. An amplifier improves the inadequate voltage in order to control the voltage of the generator's field windings. So the excitation voltage (E) of the generator is being affected by the magnitude of the real power (Pe), which is given as [1]. V is terminal voltage, Xs is synchronous reactance, and (δ) is the phase angle difference between V and E. After a sudden change in load, the frequency, and voltage changes, so the change in real power is given by (3), change in terminal voltage is given by (4), and the change in excitation voltage is given by (5) K1 is the constant flux linkages, K2 is phase angle difference linked to the change in power to alter the direct flux axis. K5 is the change in terminal voltage to change in phase angle, depending on impedance, K6 is the change in terminal voltage to change in excitation voltage. is given by (5), where K3 is the impedance factor, K4 is change in rotor angle due to demagnetizing effect is given by Egf is the generator field's voltage in p.u. and Tfoc is the time constant for the field windings.