Principles of Power System

Circulating Current Scheme for Transformer Protection: Merz-Price Circulating Current Scheme for Transformer Protection is commonly used for the protection of power transformers against earth and phase faults. The system as applied to transformers is fundamentally the Stine as that for generators but with certain complicating features not encountered in the generator application. The complicating features and

Earth Fault Protection or Leakage Protection: An Earth Fault Protection usually involves a partial breakdown of winding insulation to earth. The resulting leakage current is considerably less than the short-circuit current, The Earth Fault Protection may continue for a long time and cause considerable damage before it ultimately develops into a short-circuit and removed from

Buchholz Relay: Buchholz Relay is a gas-actuated relay installed in oil immersed transformers for protection against all kinds of faults. Named after its inventor, Buchholz, it is used to give an alarm in case of incipient (i.e. slow-developing) faults in the transformer and to dis­connect the transformer from the supply in the event of severe internal faults. It

Protection of Transformers: Transformers are static devices, totally enclosed and generally oil immersed. Therefore, chances of faults occurring on them are very rare. However, the consequences of even a rare fault may be very serious unless the transformer is quickly disconnected from the system. This necessitates to provide adequate automatic Protection of Transformers against possible

Balanced Earth Fault Protection: In small-size alternators, the neutral ends of the three-phase windings are often connected internally to a single terminal. Therefore, it is not possible to use Merz-Price circulating current principle described above because there are no facilities for accommodating the necessary current transformers in the neutral connection of each phase winding. Under

Differential Protection of Alternators: The most common system used for the protection of stator winding faults employs circulating-current principle (Refer back to Art. 21.18). In this scheme of Differential Protection of Alternators, currents at the two ends of the protected section are compared. Under normal operating conditions, these currents are equal but may become unequal

Protection of Alternators: The generating units, especially the larger ones, are relatively few in number and higher in individual cost than most other equipment’s. Therefore, it is desirable and necessary to provide Protection of Alternators to cover the wide range of faults which may occur in the modern generating plant. Some of the important faults