Generator Loss Of Excitation Protection Research Articles

A setting-free flux-based synchronous generator loss of excitation protection

Protection against loss of excitation (LOE) in synchronous generators is requisite because of its harmful effects on both the generator and power system. This paper proposes a setting-free method to detect loss of excitation in synchronous generators. To this end, a flux-based method which is based on derivative of the flux is proposed in order to detect the fault. Because of negative amount of the flux derivative or rate of the flux variation at the LOE moment, it can be a good index to specify the fault. The proposed method does not require any threshold to act in different situation, for example, in different loads or existence of the FACTs devices. It should be stated that proposed relay will operate without any delay in all the mentioned situations. In order to validate the operation of the proposed method, some simulations have been done in MATLAB/Simulink software.

Impact of static synchronous compensator on flux‐based synchronous generator loss of excitation protection

In order to increase the power transfer and providing the optimum utilisation of the power system capability, application of flexible alternating current transmission system (FACTS) devices technology, such as static synchronous compensator (STATCOM), has been attracted, in recent years. However, the STATCOM changes the voltage and current of the power system that disturb the operation of the impedance-based synchronous generator loss of excitation (LOE) protection. Then, this study proposes a new flux-based LOE protection method, in the presence of STATCOM, that is based on the local variation of the flux linkage of the generator available at the location of relay. The mentioned relay is independent of other generator protection relays without any coordination. In order to show the satisfying operation of the proposed method, some simulations have been carried out in the Matlab/Simulink software. A single-machine infinite bus and a three-machine infinite bus systems have been used in simulations. The results show that the presence of STATCOM has no important effect on the performance of proposed relay opposite to a negative offset relay with two protective zones (the widely used impedance method) which is affected by STATCOM operation.

Impact of Midpoint STATCOM on Generator Loss of Excitation Protection

This paper explores the impact of a transmission-line midpoint STATCOM on the performance of the generator loss-of-excitation (LOE) protection. In this context, investigations are conducted on a two-hydrogenerator power station for two LOE contingencies, namely, a complete LOE due to a field-winding short circuit and a partial LOE due to a sudden drop in the excitation voltage at different generator loadings. The results of these investigations show that the midpoint STATCOM has adverse impacts on the LOE distance relay in the form of delay time and/or underreach phenomenon. These adverse impacts vary with the generator loading and the LOE mode. The time-domain simulation studies are conducted using PSCAD/EMTDC software.

A High Speed, Discriminating Generator Loss of Excitation Protection

A new loss of excitation protection scheme has been devised in order to minimize the system voltage disturbance caused by excitation failure. It was designed specifically to prevent tripping of a sensitive load adjacent to a generating station with only one unit in operation. Besides meeting the special requirements of the single unit environment, the scheme appears to have some advantage over conventional loss-of-field protection when used in a station with more than one unit in service. The relay described has been in service for two years, complementing conventional protection, at a large nuclear plant which now has three units in operation. The relay is being modified to include limited over-excitation protection for future applications.