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.

Outlines

00:00

🔍 Energy Efficiency in Power Plants

The first paragraph discusses the general concept of energy efficiency in power plants, emphasizing the importance of stable operating conditions and the standardization of voltage for ease of calculation. It highlights the differences in efficiency between various power sources, such as thermal, nuclear, and renewable energy sources like solar and wind. The speaker also touches on the efficiency rates of nuclear power plants, which are significantly higher compared to solar and wind energy, and the steps involved in energy conversion in thermal power plants, which contribute to energy loss.

05:02

🌐 Challenges in Renewable Energy Integration

This paragraph delves into the challenges faced in the integration of renewable energy sources, such as solar and wind, into the power grid. It mentions the term 'microgrid' and discusses the limitations related to installation, availability, and the cost of setting up wind and hydro power plants. The speaker also explains the role of an economizer in reducing energy consumption and improving boiler efficiency by preheating fluids, and the importance of enthalpy in this process.

10:05

🛠️ Power Plant Components and Their Functions

The third paragraph focuses on the components of power plants, such as economizers, superheaters, and pre-heaters, and their roles in the energy production process. It also touches on the concept of super-critical power plants and the grounding practices in switchyards, including the installation of earth mats for protection against lightning and other electrical faults. The speaker discusses the importance of the alternator's rating in power generation and the distinction between actual power and reactive power.

15:05

🌡️ Efficiency and Control in Power Generation Systems

The final paragraph addresses the efficiency and control mechanisms in power generation systems, particularly in thermal and hydroelectric power plants. It discusses the role of the prime mover and the governor in maintaining constant speed and the process of energy conversion in these plants. The speaker also mentions the efficiency rates of solar and wind power plants, which are notably lower than conventional energy sources, and the challenges in regulating the speed or intensity of the energy source in these systems.

Keywords

💡Prefold current

The term 'prefold current' seems to be a mispronunciation or a typo in the script. It is likely referring to 'pre-fault current,' which is the current flowing in an electrical system before a fault or malfunction occurs. In the context of the video, it is mentioned to establish the baseline for system conditions before any disturbances, which is crucial for understanding the stability and performance of the power system.

💡Offset

In the script, 'offset' could refer to the difference or compensation in a system's parameters to achieve a desired state or condition. It is often used in electrical engineering to describe adjustments made to voltage, current, or other variables to ensure system stability or to correct for imbalances.

💡Stable working region

The 'stable working region' refers to the operational state of a system where it maintains a consistent and reliable performance. In the video, it is mentioned that devices like generators are considered to be in a stable working region, implying that they operate without disturbances, which is essential for efficient energy production and distribution.

💡Efficiency

Efficiency in the context of the video pertains to the effectiveness with which energy is converted from one form to another in power plants. It is a key performance metric, with higher percentages indicating less energy loss during conversion. The script discusses the efficiency of different types of power plants, such as thermal, nuclear, and renewable energy sources.

💡Thermal power plant

A 'thermal power plant' is a type of power station that uses heat to generate electricity. The script mentions the steps involved in its operation, such as fuel preparation, steam production, and energy conversion, which inherently involves energy losses, thus impacting its overall efficiency.

💡Renewable energy

Renewable energy sources, such as solar and wind, are highlighted in the script as alternatives to conventional energy sources. They are characterized by their ability to be replenished naturally and are considered more environmentally friendly, although the script notes that their efficiency can be lower compared to non-renewable sources.

💡Economizer

An 'economizer' is a device used in power plants, particularly in boiler systems, to improve efficiency by preheating feedwater using the waste heat from flue gases. The script explains its role in reducing energy consumption and enhancing the overall thermal efficiency of the power generation process.

💡Enthalpy

Enthalpy is a thermodynamic property that represents the total heat content of a system. In the script, it is mentioned in the context of the economizer, where it likely refers to the heat content of the flue gases that are used to preheat the feedwater, thereby reducing the energy required for further heating.

💡Microgrid

A 'microgrid' is a localized grouping of energy resources that can operate independently from the traditional power grid. The script discusses the use of the term 'micro' in relation to power generation, indicating a shift towards smaller, more localized energy systems that can be more flexible and responsive to local energy needs.

💡Supercritical power plant

A 'supercritical power plant' is a type of thermal power plant that operates at conditions beyond the critical point of water, which allows for higher efficiencies and potentially lower emissions. Although not directly explained in the script, the term is mentioned, suggesting a discussion of advanced power plant technologies.

💡Earth mat

An 'earth mat' or grounding mat is used in electrical systems, particularly in switchyards, to provide a path for excess current or lightning to flow safely into the ground. The script describes its importance in construction for safety and protection against electrical faults.

💡Alternator

An 'alternator' is a device that converts mechanical energy into alternating current electricity. The script discusses the rating of alternators in terms of megawatts or gigawatts, which refers to their capacity to generate electricity, and the importance of considering actual power output rather than reactive power.

💡Negative sequence

The 'negative sequence' refers to a condition in three-phase electrical systems where the phase currents are equal in magnitude but 180 degrees out of phase with each other. The script mentions its relevance in the context of excitation failure in alternators and its use in directional relays for fault detection and protection.

Highlights

Importance of system stability before a fault, with the assumption of unity voltage for ease of calculation.

General generator and device operation in a stable working region, unaffected by faults.

Efficiency comparison between thermal, nuclear, and renewable energy sources, with nuclear power plants having higher efficiency.

The role of economizer in reducing energy consumption and improving boiler efficiency.

Different steps and energy losses in thermal power plants compared to renewable energy sources.

Higher efficiency of solar and wind energy conversion, despite requiring fewer steps.

Use of the term 'microgrid' due to installation issues and the availability of wind and solar energy.

The concept of supercritical power plants and their efficiency.

Earth mat installation in switch yards for grounding and protection against extra current or lightning.

Rating of alternators in terms of megawatts or gigawatts, focusing on actual power generation.

The role of negative sequence in alternators and its impact on excitation failure.

Use of directional and non-directional relays in transmission lines for fault detection and protection.

Time grading system for circuit breakers to operate in sequence during a fault.

Zero current switching technique for circuit breakers to operate at current zero value.

Efficiency rates of solar and wind power plants, and the challenges in their widespread adoption.

Importance of boiler efficiency in thermal power plants and its impact on overall energy generation.

Mechanical systems in hydropower plants, including Kaplan and Pelton turbines, and their electrical aspects.

Regulation of speed in prime movers and the role of governors in maintaining constant speed.

Understanding the color equation and its relevance in mechanical and electrical systems.

Transcripts

[Music]

foreign

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calculation why we generally ignore the

prefold current

um so because of the offset the

um ideally there what we take is that

the before the fault the system must be

working in a condition uh which is

stable and

uh we consider it as the voltage as

unity and that's why only for making our

calculation easy

um

in thing mode apart from this

uh sir

other than this sir uh

so we usually either ignore all kind of

effect we take as our general generator

and other devices are in the this stable

working region only uh like um they are

not getting any kind of effect

and uh also

before this

the prefall conditions are

depending no certain only I think this

much as that I can recall at the moment

that you first look at it

uh so definitely there are

um big uh you know competition um

boiling boilers and all that these are

actually big and shape that is the thing

that will come in our uh the smokes

coming out from those things

[Music]

power plant uh the roll power plant is

the efficiency uh from nearly 40 to 50

percent only

um

in the nuclear power plant

uh nuclear power transfer the efficiency

goes High nearly around UH 60 to 70

percent

when we go through this renewable energy

like the solar

solar Hydro wind efficiency goes so much

down when compared with the

non-conventional source of energy

can you repeat the question the voice

was breaking

when compared with the conventional

source of energy with the

non-conventional source of energy

was so much less

uh sir the

that we are actually utilizing on the

thermal power plant and other uh so

these are actually the number of

procedure and the steps events are if

you talk about Hydro then it is only

some seasonal thing uh when there is a

circular supply of water then only we

can utilize it in case of thermal power

plant you know the procedures are uh

like uh preparation of the fuel then

preparing of a stream and then uh

converting into one form to another form

uh that is actually taking a lot of uh

our energy at every step is uh

decreasing only we are just converting

it in one form to another and there is a

lot of loss of energy which we are

unable to collect that whereas compared

to other conventional sources of energy

on the wind the title and these kind of

energies on the number of steps is

actually lesser than compared to others

we don't require a large Plant and all

that for converting whether it is a

simple solar system we already require a

plate and the conversion of energy is

directly from you know the electrons so

what is the efficiency of solar and wind

uh sir the solar has the efficiency

nearly 80 percent and vendors also 70 to

80 percent only

80 percent efficiency

answer as far as I've read that is it is

higher in uh uh efficiency then our

Convention of oh yes sir

if it has a higher efficiency then why

we generally use the term the microgrid

synchronization why the term micro has

been used

uh actually actually sir that is due to

the installation issues and also the

availability of wind and it is like on

the height of wind plants that one

require and the installation cost all

that uh it is because of this only that

we are now

targeting the micro

um one power generation thing

um even this is the same case with uh

Hydro also

so that is also like uh wherever the

water supply is there a good substance

okay you're in the wrong track

tell me one thing

what is the role of economizer and what

are the gases that the economist

generally hold

uh sir uh economizer is actually

a device which is installed near the

condenser or the boiler so it it

actually reduces the energy consumption

and it is like uh it is useful in

preheating fluid sir

uh so it it is kind of like um in our

boiler so there are multiple steps like

we have a equivalizer we have super

heater and we have pre-heater all these

things combined to reduce the energy of

uh overall procedure okay so we're going

to measure just the heat exchanger yes

sir kind of

and uh sir improve the efficiency of the

boiler

yes sir

okay

what is said that economizer use fully

enthalpy

uh seven what

in in enthalpy

and

[Music]

um

okay

um how we can generalize and how we can

regulate the economical efficiency

generalize our regulate

if suppose economizer is not there then

what would be the result

and everything will be done by boiler

only

play uh

heating of the water from its below

saturation to above saturation

everything will be done in that thing

only

so

okay have you hit the term super

critical power plant

super critical PowerPoint

no sir I have

not written

okay and in the switch yard what is the

rule of Earth mat

s are actually uh before when we are

constructing a switcher then during the

point of construction we usually install

a Earth mat below our c-shared so and we

provide the grounding to this not smart

only like uh it is a kind of net that we

have uh at particular depth in our Earth

and we connect the wires to the devices

right to it it provides the path for the

uh extra current or the lightning uh to

flow through it in the ground

okay

if suppose in the transmission line if

the Earth wire is not there

yes and which protection is disabled

which production is disabled

yeah

then

yeah with this Earth wire is being

placed

foreign

[Music]

for the case of any power plant right

though

the unit of alternator

yeah what is the rate of alternator

the rating of alternator

hmm

um

the alternator

okay we are there good but the rating of

the problem it is it is in what

okay another megawatt or gigawatt

um because we are considering about the

uh actual power only

uh not they are taking Consulting the

reactive power

okay what is meant to be with actual

power

uh sir

or the it doesn't

the component of our total power uh that

we are utilizing uh it is not uh not

doing in uh for generation of uh

like uh magnetic field and all these

things here so

it doesn't like we are presenting the

our total power in the terms of p plus

JQ so the thumb p is actually the actual

part that we are considering and we are

mentioning our brand in this term

solution

if suppose okay

have you heard that I'm negative

sequence really

a negative segment yes sir I haven't

recorded

um what is used

it is used in alternator only there in

case of failure of excitations

failure of excitation okay then where

does this release being used

let us also been used

um sir

namely

is also used in transmission lines also

uh

actually there are more relays also kind

of interesting only it has uh

inheritance Direction property and even

in case of negative sequence you know

the direction of our uh excitation will

be opposite to our uh the sequence that

we have so that is why we are

considering it in the failure of

excitation

so in a ring system does this more relay

is being used or this

native sequence relay is being used

Okay negative frequency relay it is

being categorized in Direction relay or

non-directional delay

uh

directional only

directionally in any looping which which

law will will follow

um system

sir uh like those are from near the

generation point we are having

non-directional and it depends after

that like we keep on putting a

directional

and suppose if there's someone there is

a fault occur in any system

then what is the sequence of the circuit

breaker to operate

keeping our circuit breakers

um

sir we use on time grading thing for

this like uh the nearest one will get

open first and then we calculate time

for other relays also

um

we do grading system and depending upon

that only like the one

near the

uh generation point will be opening in

the last and the other coming in between

first so

uh at all we see the number of relays

that are being installed and after that

only we calculate the time for each of

them okay

time is an issue okay suppose

zero current switching have you here

this term

yes sir uh when the current is passing

through the zero value then only we try

to operate our circuit design relay

Okay so

because all the things are related on

zero sequence is something different

uh zero sequences different sir and zero

switching is different

okay so we'll stop circuit breaker we

are using this zero sequence

uh

sorry sir I'm no idea about this

okay do we listen um

the performance was good

with a question will talk not a problem

and the thing is that the question will

be asked from the generation part okay

so one thing I want to give you

suggestion I have not asked about the

boiler boiler efficiency

so please go through go through this

okay

and now

hydropower plant Kaplan Pelton furnace

they are the part of mechanical but we

are just studying an electrical also

because they will ask

okay yes boiler okay into the thermal

and the hydro case we are also utilizing

this and the coal

and how the process of the code is being

generated

Prime over

okay

so they will ask the question on the

prime mover also

right

how the speed is being relegated and how

the speed is being maintained constant

part of the system

answer related to the efficiency and

also

you will get wrongly

in the flyable government

and see that we are in the flower

Governor we are regulating the

the speed

okay

um

yeah so

in the case of in the case of uh over

and under with the mechanical mechanical

with the mechanical system is being

designed with the steam power is

that is set to where the flywheel and

and

[Music]

see they will ask the color equation

they have one question that I've asked

in the previous interview

s condenser and the flywheel

yes okay

and the other two different things

okay so yeah in the last thing

efficiency of a solar power plant is

only 15 to 18 15 to 20 percent

yeah

oh yeah

and efficiency of a wind probably is

also very much less because

um because the terms of intensity that

we require is not it is not desired

we're not getting

right that is in the case of

what you say as a third third power

plant because in where we are regulating

the speed or intensity of the stream

right

[Music]

and all the goodness

okay

yes sir

[Music]