Operational Problems in turbo generators and their analysis Rao S. Adinarayana, Rao K. Poornachandra, Anil P. Bharat Heavy Electricals Limited, Hyderabad, India Online published on 18 September, 2018. Abstract Synchronous generators are the most widely used machines in the power generation industry across the world. The electromagnetic components are often referred to as the active parts of generator. These parts consist of several entities within the generator viz., Stator core, Stator coils/bars, Stator winding, Output leads/bushings and phase connectors, Rotor excitation leads, Rotor coils, Rotor winding, Supervisory and monitoring components. In addition to the above, a synchronous generator requires a reliable direct current field excitation to the rotor provided by the excitation system for its satisfactory operation. The excitation systems widely used these days fall in to either of the two types viz., Static excitation and brushless excitation system, the later being the most commonly used in industrial power generation segment. The purpose of this article is to provide an overview on some of the operational problems encountered in turbo-generators and their analysis for understanding the possible remedial actions to mitigate these problems. The synchronous generators are the major sources of short-circuit currents in power systems. However, the fault occurrence is rare but can be highly detrimental to the machine as well as the power system to which the generator is connected. The major operational problems occurring in turbo-generators can be broadly classified in to three categories viz., problems due to system disturbances, problems due to faults in and around the machine and problems due to operating the equipment beyond OEM specified limits. Under system related problems, the fluctuations in voltage and frequency, sudden load throw-off conditions, switching surges and HV side disturbances are dealt with. In general, the allowable generator voltage variations are set to limit the field current within rotor thermal and under excitation capabilities. Similarly, the allowable frequency variations are set as per the guidelines of national grid in respective countries. Various types of earth faults in stator and rotor, short circuits, faults in excitation system, faulty synchronization, motoring, pole slipping, asynchronous operation and the effects of shaft voltages are covered under the problems in and around the generator. Phase faults in generators are rare, but they can occur and must be protected against. Phase faults if not detected fast often develop into ground faults. Most of the generator stator winding faults are phase to ground faults. The type of generator neutral grounding significantly influences protection against stator earth faults. The article concludes with explaining the two-shift operation in Gas turbine applications and the effects of operation of the equipment beyond the OEM specified limits. Top Keywords Generator, Earth Fault, Short Circuit, Excitation System, Faulty Synchronisation, Reverse Power Operation, Asynchronous Operation, Shaft Voltages, Pole Slipping, Two Shift Operation, Permissible Limits. Top |