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What is the level of voltage at generating station that is stepped up for primary transmission?
11 kV
33 kV
66 kV
Any of above
11 kV
In electrical power systems, power is typically generated at generating stations at voltages ranging from 11 kV to 33 kV. To minimize I2R losses and reduce the cross-sectional area of conductors during long-distance transmission, this voltage is stepped up using step-up transformers to high transmission voltages (e.g., 132 kV, 220 kV, 400 kV).
In electrical power systems, power is typically generated at generating stations at voltages ranging from 11 kV to 33 kV. To minimize I2R losses and reduce the cross-sectional area of conductors during long-distance transmission, this voltage is stepped up using step-up transformers to high transmission voltages (e.g., 132 kV, 220 kV, 400 kV).
P=3тАЛVLтАЛILтАЛcos╧Х тАФ Representation of power in a 3-phase system
PlossтАЛ=I2R тАФ Power loss in transmission lines
The generating station uses step-up transformers at the switchyard to increase the generated voltage level before it enters the primary transmission grid. This process relies on the principle of electromagnetic induction where the transformer turns ratio N2тАЛ/N1тАЛ is designed such that V2тАЛ=V1тАЛ├Ч(N2тАЛ/N1тАЛ). By increasing the voltage V, the current I decreases for the same power P=VI, which significantly reduces power dissipation in the transmission lines.
Most alternators are designed to generate voltage in the 11 kV to 33 kV range due to insulation limitations at higher voltages.
Higher transmission voltages reduce the required conductor cross-section, leading to significant economic savings on copper/aluminum.
The primary transmission voltage in India is standard at 132 kV, 220 kV, 400 kV, and 765 kV.
Reduction in line current (I)
Significant reduction in power losses (I2R)
Reduced volume of conductor material required
Increased cost of switchgear and transformers
Requires high levels of insulation (dielectric strength)
Complex maintenance procedures at high voltage substations
Long-distance power transmission lines
Grid interconnectivity
Bulk power supply to industrial zones
While 11 kV is the most common standard for generation, modern large-capacity generators may occasionally generate at 22 kV or 33 kV, though 11 kV remains the widely accepted standard for textbook problems.
Options B and C represent voltage levels used in sub-transmission or distribution networks, not typical generating station output before step-up.
A is correct тАФ The standard voltage generated at most power stations is 11 kV, which is subsequently stepped up for transmission.
Always remember: higher voltage means lower current for the same power, which is the fundamental reason behind high-voltage transmission.