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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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Which of the abnormality possible in alternator?
Failure of prime mover
Overloading
Over voltage
All of above
All of above
Quick Summary: Alternators are subject to various electrical and mechanical abnormalities during operation, which require robust protection schemes. These abnormalities include failures of the prime mover (e.g., steam/water supply failure), overloading, and over-voltage, all of which can damage insulation or cause mechanical instability.
Alternators are subject to various electrical and mechanical abnormalities during operation, which require robust protection schemes. These abnormalities include failures of the prime mover (e.g., steam/water supply failure), overloading, and over-voltage, all of which can damage insulation or cause mechanical instability.
Pin=τ⋅ω — Mechanical power input from prime mover
Qloss=I2R — Heating effect during overloading
The prime mover failure leads to reverse power flow, where the alternator acts as a synchronous motor. Overloading causes stator overheating due to excessive I2R losses, while over-voltage can lead to dielectric breakdown of the winding insulation, necessitating protective relays like reverse power, thermal, and over-voltage relays respectively.
Prime mover failure causes the alternator to draw power from the grid, triggering reverse power protection.
Overloading leads to excessive stator heating, exceeding the thermal limits of insulation.
Over-voltage often results from sudden load rejection or voltage regulator failure.
Protection schemes are essential to prevent permanent damage to the generator windings and excitation system.
Protects generator assets from cascading failure
Ensures system stability during transient disturbances
Over-protection can lead to unnecessary tripping (nuisance tripping)
Increased system complexity and cost of relaying
Thermal power plants
Hydroelectric stations
Industrial captive power plants
Failure of prime mover results in the alternator running as a motor, which can be detected by reverse power relays.
Over-voltage can be caused by loss of excitation in other machines or sudden loss of load in radial networks.
D is correct — All listed conditions represent critical abnormalities that can occur in an alternator, requiring specific protection mechanisms to ensure operational safety.
Always remember that abnormalities are categorized as either Electrical (Short-circuit, Over-voltage) or Mechanical (Prime mover failure, Loss of synchronism).