UPRVUNL(AE) Power System Mock Interview | Important Questions for UPRVUNL | Interview preparation

Summary

This script delves into the intricacies of power plant operations, contrasting the efficiency of conventional thermal, nuclear, and renewable energy sources. It emphasizes the importance of the economizer in reducing energy consumption and improving boiler efficiency. The discussion also touches on the role of supercritical power plants, grounding in switchyards for safety, and the significance of zero sequence in relay systems. Additionally, it highlights the challenges in harnessing renewable energy, such as solar and wind, due to factors like installation costs and availability.

Takeaways

• 🔍 The script discusses the importance of system stability before a fault occurs, often assuming a unity voltage for ease of calculation.
• 🌐 It mentions that in general, the effects on generators and other devices are ignored when they are in a stable working region.
• 📈 The efficiency of power plants varies significantly, with thermal power plants at 40-50%, nuclear around 60-70%, and renewable sources like solar and wind typically lower.
• 💧 Hydropower is seasonal and depends on the availability of water supply, unlike thermal power plants which have a more consistent process.
• 🔥 Thermal power plants involve multiple steps of energy conversion, each with energy losses, unlike renewable sources which have fewer steps.
• 🌞 The efficiency of solar power is stated to be nearly 80%, and wind power around 70-80%, which is higher than conventional energy sources.
• 🌬 The term 'microgrid' is used due to installation issues, availability of resources like wind, and the height requirements for wind plants, influencing the scale of power generation.
• 🛠️ The role of an economizer in a boiler system is to preheat fluid and reduce energy consumption, improving overall boiler efficiency.
• ⚡ The grounding of a switchyard involves installing an earth mat to provide a path for excess current or lightning, protecting the electrical system.
• 🌐 The rating of an alternator is typically in megawatts or gigawatts, focusing on the actual power output rather than reactive power.
• 🔄 Negative sequence relays are used in alternators and transmission lines for fault detection, especially in cases of excitation failure.

Q & A

Why is the prefold current generally ignored in calculations?

It is ignored for simplicity, assuming the system is stable with a unity voltage before the fault, and to focus on the fault conditions rather than the normal operation.

What is the typical efficiency range for thermal power plants?

The efficiency of thermal power plants typically ranges from 40 to 50 percent.

How does the efficiency of nuclear power plants compare to thermal power plants?

Nuclear power plants have a higher efficiency, ranging from 60 to 70 percent.

What is the efficiency of renewable energy sources like solar and wind compared to non-conventional sources?

Renewable energy sources such as solar and wind have lower efficiencies compared to non-conventional sources, with solar efficiency around 15 to 20 percent and wind efficiency also being relatively low.

What is the role of an economizer in a boiler system?

An economizer is a device that preheats the fluid, reducing energy consumption and improving the overall efficiency of the boiler.

What are the typical steps in the energy conversion process of a thermal power plant?

The steps include fuel preparation, steam preparation, and energy conversion from one form to another, with significant energy loss at each step.

How is the efficiency of a solar power plant different from that of a wind power plant?

While the script mentions solar power plant efficiency as 15 to 20 percent, it does not provide a specific efficiency for wind power plants, but implies that it is also relatively low.

What is the purpose of grounding in a switchyard?

Grounding in a switchyard is used to provide a path for excess current or lightning to flow safely into the ground, preventing damage to equipment and ensuring safety.

What is the significance of the term 'supercritical' in power plants?

The term 'supercritical' refers to power plants operating at conditions beyond the critical point of water, where the efficiency can be significantly higher than conventional plants.

What is the role of a flywheel in a mechanical system?

A flywheel helps maintain constant speed in a mechanical system by storing and releasing energy as needed, compensating for fluctuations in the power source.

What is the difference between zero sequence and zero switching in electrical systems?

Zero sequence refers to the balanced condition of three-phase currents, while zero switching is a technique used to operate circuit breakers when the current passes through zero value, reducing the impact of switching.