Instantaneous Specific Protection Method Against Faulty Synchronizations of Synchronous Machines

Abstract

The probability of faulty synchronization of a generator is very small, but not impossible. The main cause of a faulty synchronization is due to wiring errors caused during maintenance or commissioning when voltage transformer and synchronizing equipment are connected or reconnected wrongly. Faulty synchronizations of synchronous generators cause overcurrent and high electromagnetic torque values that can severely damage, not only the generators their selves, but also prime movers and step-up transformers. Moreover, they produce disturbances on the power system such as power oscillations and voltage sags that can end up collapsing the system if it is not cleared quickly. Despite that, conventional synchronous generator protection systems have not a specific function against faulty synchronizations. This paper presents and analyzes a new and specific protection method against faulty synchronizations. The method is based on an instantaneous low setting overcurrent protection that is only activated during synchronizations. Once the synchronization ends, the protection gets disabled in order to allow the increase of the generator power output. Consequently, it minimizes the damages and the disturbance in the power system through rapid detection and tripping. The method has been successfully validated by computer simulations for a thermal power plant 362 MVA turbo-generator, and by experimental tests on a 5 kVA laboratory generation unit.

Emergency Prevention Control as a Means of Power Quality Improvement in a Shipboard Hybrid Electric Power System

“…where i d Load is the load current along the d-axis. The inverter's output voltage along the q-axis, U q C , is shown in Equation (23).…”

“…Currently, various protection devices [22,23] are widely used to determine the degree of power quality, allowing operation if the controlled parameters (voltage and frequency) of the parallel-operating power sources are within acceptable limits. Depending on the levels of deviation of the controlled parameters, these devices form control signals to disconnect the power source from the MSB, resynchronizing it or unloading the power sources by tripping non-essential consumers.…”

Impact Study of Unequal Voltages of Power Plants (Generators)

“…As a result of the wrong synchronization resulting from the unequal values of voltages, a disturbance occurred in the various variables of both machines. It is assumed that the angular velocity of both machines and therefore the frequencies are equal, but due to the wrong synchronization, the difference increases between them due to growth of the reduction in the excitation level of the rotor of the second machine, and as shown in the figures (6,7). Because of the wrong synchronization, the terminal voltage of both machines decrease with the decrease in the excitation level of the second generator rotor, as shown in the figure (8).…”

“…The main cause of a faulty synchronization is due to, human errors, when voltage transformer and synchronizing equipment are connected or reconnected wrongly during maintenance leads to wiring errors and error ratio of voltage transformers. This deviation produces a high sudden reactive power flow either into the generator or into the power system, according to the voltage difference sign [6].…”