Extra high voltage transmission means

Question

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Option B: Voltage in a range of 400 kV to 750 kV

Explanation & Concepts:
Extra High Voltage (EHV) transmission is defined by the Indian Standard classification for power transmission lines. In electrical engineering, transmission systems are categorized based on voltage levels to manage power transfer, line losses, and insulation coordination.

Working Principle: As voltage levels increase, the current required to transmit a specific amount of power decreases according to the relation $P = \sqrt{3} V_L I_L \cos \phi$. Lower current significantly reduces $I^2 R$ transmission losses and improves voltage regulation. EHV levels are necessitated for long-distance bulk power transmission to ensure economic feasibility and efficiency.

Key Formulas: $P = \sqrt{3} V_L I_L \cos \phi$ — Real power transmission formula showing the inverse relationship between voltage and current for constant power; $P_{loss} = 3 I_L^2 R$ — Power loss formula explaining why higher voltage reduces transmission losses

Key Points: HV (High Voltage) usually refers to ranges between 33 kV and 220 kV.; EHV (Extra High Voltage) covers the 400 kV to 750 kV range.; UHV (Ultra High Voltage) applies to transmission systems operating above 750 kV.; Increasing voltage allows for smaller conductor cross-sections for the same power capacity.

Advantages: Reduced transmission line losses; Improved power transfer capability; Enhanced system stability; Reduced conductor material requirements

Disadvantages: Increased cost of insulation and towers; Higher corona loss and radio interference; Complex substation equipment design

Applications: Bulk power transmission over long distances; Interconnection of regional power grids

Additional Info: In the Indian power sector, 400 kV is a standard backbone voltage for inter-state transmission.. Option A refers to lower voltage categories (HV/MV/LV).. Option C corresponds to UHV (Ultra High Voltage) systems.

Answer: B is correct — Extra High Voltage (EHV) transmission is internationally and nationally recognized as the range between 400 kV and 750 kV.

Exam Tip: Always distinguish between EHV and UHV (Ultra High Voltage); UHV is specifically reserved for voltages exceeding 750 kV (e.g., 800 kV or 1200 kV).

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Option A: Voltage less than 400 kV

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Option C: Voltage greater than 750 kV

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Option D: Any of above

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