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Permissible variation of frequency in power system is
┬▒1%
┬▒3%
┬▒5%
┬▒10%
┬▒3%
In Indian Power Systems, the grid frequency is nominally maintained at 50 Hz. To ensure the stability of the grid and the health of connected equipment, the Central Electricity Regulatory Commission (CERC) mandates a permissible variation range of ┬▒3% (48.5 Hz to 51.5 Hz).
In Indian Power Systems, the grid frequency is nominally maintained at 50 Hz. To ensure the stability of the grid and the health of connected equipment, the Central Electricity Regulatory Commission (CERC) mandates a permissible variation range of ┬▒3% (48.5 Hz to 51.5 Hz).
f=120NPтАЛ тАФ Relation between frequency (f), speed (N), and number of poles (P)
╬Фf=factualтАЛтИТfnominalтАЛ тАФ Frequency deviation formula
Frequency in an AC power system is directly related to the balance between active power generation and load demand. When generation exceeds demand, the frequency increases; when demand exceeds generation, the frequency drops. The ┬▒3% limit serves as a regulatory buffer to prevent protective relay operations, such as Under-Frequency Load Shedding (UFLS) or generator tripping, which occur if the frequency deviates beyond these critical safety bounds.
Nominal frequency in India is 50 Hz.
Grid frequency is an indicator of power balance between supply and demand.
Frequency variation causes instability in induction motors and sensitive electronic loads.
Automatic generation control (AGC) is used to regulate frequency within these limits.
Protects sensitive industrial equipment from damage
Prevents large-scale grid blackouts
Maintains synchronization of parallel generators
Tight frequency control requires high reserve power margins
Increased operational costs for power plants to maintain strict tolerance
Grid management and load dispatch centers
Design of power system protection relays
Operational maintenance of turbines and generators
The ┬▒3% limit is the standard operating range prescribed by IEGC (Indian Electricity Grid Code).
Deviation beyond this limit triggers hierarchical defense mechanisms including demand response and frequency-sensitive tripping.
B is correct тАФ The permissible variation of frequency in the Indian power system is maintained at ┬▒3% of the nominal 50 Hz.
Always remember that while ┬▒3% is the statutory frequency limit, voltage variations for low/medium voltage are typically ┬▒6% and for high voltage ┬▒10%.