Penstock in a hydroelectric power plant is

Question

Examoogle · Accepted Answer

A conduit connecting forebay to scroll case of turbine

Explanation: A penstock is a large-diameter pipe or conduit used in hydroelectric power plants to transport water from the reservoir or forebay to the turbine's scroll case. It is designed to withstand high internal pressure, as it converts the potential energy of the stored water into kinetic energy required for power generation.

Working Principle: Water from the high-elevation reservoir flows through the penstock due to gravity. As water descends, its potential energy is converted into pressure and kinetic energy, which is then directed through the scroll case into the turbine runner to rotate the shaft of the electrical generator.

Key Formulas: $P = \rho g H$; $V = \sqrt{2gH}$

Key Points: Penstocks are typically made of steel or reinforced concrete to handle high pressure.; Water hammer effect is a critical concern, necessitating surge tanks to prevent pipe rupture.; The diameter is sized to minimize head loss due to friction.

Advantages: High efficiency in energy transfer.; Capable of handling significant pressure heads.

Disadvantages: Vulnerable to water hammer pressure surges.; High construction and material costs.

Applications: High-head hydroelectric power plants.; Pumped storage systems.

Additional Info: A surge tank is often placed between the forebay and the turbine to mitigate pressure fluctuations.. Option A refers to a draft tube, which is located after the runner. Option B refers to a nozzle, commonly used in Impulse turbines like Pelton wheels, not the conduit itself.

Answer: C is correct — A penstock serves as the primary conduit directing water from the upstream reservoir/forebay to the power-generating turbine.

Exam Tip: Remember: Draft Tube (after turbine) vs. Penstock (before turbine). Draft tubes recover kinetic energy; penstocks deliver potential energy.

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