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Introduction to Power Engineering [EEE281]. Mushtaq Ahmad Bhatti Principal Engineer Department of Electrical Engineering COMSATS Institute of Information Technology, Wah Cantt, Pakistan. My Background. M.S Electical Engineering Control Systems University of Michigan, Ann Arbor USA

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Introduction to power engineering eee281

Introduction to Power Engineering[EEE281]

Mushtaq Ahmad Bhatti

Principal Engineer

Department of Electrical Engineering

COMSATS Institute of Information Technology,

Wah Cantt, Pakistan


My background

My Background

  • M.S Electical Engineering

    • Control Systems

    • University of Michigan, Ann Arbor USA

  • Master of Telecommunication Management

    • Institut National Des Telecommunication France

  • BSc Electrical Engg

    • University of Engineering and Technology, Lahore

  • Received Science &Technology Scholarship by Government of Pakistan for higher studies in USA.

  • Secured first class, second position in B.E with HONOURS.

  • Obtained SILVER MEDAL & CASH PRIZE on securing first class 2nd Position in F.Sc. from Multan Boardwith A-1 grade.

  • Obtained SILVER MEDAL &CASH PRIZES in matriculation exam.

  • Merit scholarships throughout academic career.


My background1

My Background

  • Management experience in the capacity of MP-II (Director Telecom, MoIT) and MP-I( Member Telecom, MoIT)

  • Chief Executive Officer of Public and Private Entities

  • Conceptualized USF Policy Framework and designed first lot for auction

  • Served as USF Board Member

  • Auction of Cellular, WLL and LL Licenses

  • Policy Formulation Experience for Telecom Sector

  • De-regulation Implementation experience


My background2

My Background

  • Regulatory Compliance experience

  • Privatization experience of Incumbent Operator

  • Experience as Board of Director of eminent Telecom entities

  • PSDP project Development experience for Telecom sector


My background3

My Background

  • Represented Pakistan internationally on renowned forums of ITU, ATP and CTO

  • Enlisted as Certified Director with Pakistan Institute of Corporate Governance after Certification in Corporate Governance Leadership Skills Programme

  • Trio experience of working with Incumbent Operator, Regulator and Policy Formulation body


Recommended books

Recommended Books

  • Principles of Power Systems by V.K. Mehta, Rohit Mehta

  • A course in Electrical Power by J.B. Gupta

  • Electric Power System Basics by Steve Blume, latest edition

  • Guide to Electric Power Generation


Course objectives

Course Objectives

  • Give understanding of Electric Power Systems fundamental

  • Basic Electrical terminology and concepts of

    • Power Plants

    • Substations

    • Transmission lines

    • Distribution lines

  • Basic electrical safety concepts


Course outline 1

Course Outline # 1

  • Fundamentals of Electric Power

    • Conversions of natural resources into electrical energy

  • Generation

    • Brief introduction of different types of power plants

  • Transmission

    • Requirement and types of transmission lines

  • Distribution Systems

    • Brief introduction of different types of distributions systems

  • Utilization

    • Different types of loads


Course outline 2

Course Outline # 2

  • Power Systems Protections

    • Concepts of Power Systems Protective Relaying

  • Power System Operations

  • Interconnection and Regulations

    • Benefits

    • Regulatory Requirements


Tentative lecture breakdown week wise

Tentative Lecture Breakdown (week-wise)


Tentative lecture breakdown week wise1

Tentative Lecture Breakdown (week-wise)


Tentative lecture breakdown week wise2

Tentative Lecture Breakdown (week-wise)


Tentative lecture breakdown week wise3

Tentative Lecture Breakdown (week-wise)


Fundamentals of electric power

Fundamentals of Electric Power

  • Energy basic necessity of life

  • Energy has made

    • shorter working days

    • Higher agricultural production

    • Higher industrial production

    • More balanced diet

    • Better transportation facilities

  • Energy used per person and standard of living are corelated


Fundamentals of electric power1

Fundamentals of Electric Power

  • Importance of Electrical Energy

    • Energy exists in different forms but most important form is Electrical Energy.

    • Energy may be needed as heat, light and motive power

    • Due to technological advancement electricity can be conveniently converted into other forms

    • Advancement of country measured in terms of per capita consumption of electrical energy


Fundamentals of electric power2

Fundamentals of Electric Power

  • Convenient form

  • Easy control

  • Greater Flexibility: Ease of transportation from one place to other

  • Cheapness

  • Cleanliness: not associated with smoke, fumes or poisonous gases

  • High Transmission Efficiency


Generation of electrical energy

Generation of Electrical Energy

  • Conversion of energy available in different forms in nature into electrical energy is known as generation of electrical energy

  • Electrical energy is manufactured commodity like furniture, clothing

  • Unique characteristic: Instantaneous production and utilization


Generation of electrical energy1

Generation of Electrical Energy

R Y B

Energy from some source

Alternator

Prime Mover


Sources of energy

Sources of Energy

  • Sun

    • Heat energy radiated by Sun focused with the help of reflectors

    • Heat energy used to raise steam which in turn runs turbine-alternator

      • Requires large areas

      • Not useable in cloudy days

      • Uneconomical method


Sources of energy1

Sources of Energy

  • Wind

    • Wind mills drives generators

    • Generators charge batteries to be used when there is no wind

    • Maintenance and generation costs are low

    • Variable output

    • Unreliable

    • Power generated is small


Sources of energy2

Sources of Energy

  • Water

    • Potential Energy

    • Turbines

    • Alternators

    • Popular because maintenance and production costs are small

  • Fuels

    • Coal

    • Oil

    • Gas


Sources of energy3

Sources of Energy

  • Nuclear Energy

    • Fission reaction of Uranium releases abundant amount of heat

    • 1Kg of Uranium produces equivalent to4500 tonnes of coal

    • Heat……>steam…..>Steam turbine……>Alternator

    • High Cost of fuel

    • High cost of technology

    • Problem of disposable radio active material

    • Dearth of trained personnel


Sources of energy4

Sources of Energy

  • Comparison


Ball park operating costs

Ball park operating Costs

Nuclear:$10/MWh

Coal:$40/MWh

Wind:couple $/MWh

Hydro:few $/MWh

Solar: $0/MWh

Natural Gas:

cost in $/MWh is 7 to 20 times fuel cost in $/MBtu;

for example, with $8/MBtu gas, cost is $56/MWh to $160/MWh.


Energy

Energy

Energy:

Integration of power over time,

Energy is what people really want from a power system,

How much work you accomplish over time.

Energy Units:

Joule= 1 watt-second (J)

kWh– kilowatthour (3.6 x 106 J)

Btu– 1055 J; 1 MBtu=0.292 MWh

U.S. electric energy consumption is about 3600 billion kWh (about 13,333 kWh per person, which means on average we each use 1.5 kW of power continuously).


Power

Power

Power:

Instantaneous rate of consumption of energy,

How hard you work!

Power = voltage x current for dc

Power Units:

Watts = amps times volts (W)

kW –1 x 103 Watt

MW – 1 x 106 Watt

GW–1 x 109 Watt

Installed U.S. generation capacity is about 900 GW ( about 3 kW per person)

Maximum load of Austin about 2500 MW.

Maximum load of UT campus about 50 MW.


Simple power system

Simple Power System

  • Every power system has three major components:

    • generation: source of power, ideally with a specified voltage and frequency

    • load or demand: consumes power; ideally with a constant resistive value

    • transmission system: transmits power; ideally as a perfect conductor

  • Additional components include:

    • distribution system: local reticulation of power,

    • control equipment: coordinate supply with load.


Complications

Complications

No ideal voltage sources exist.

Loads are seldom constant and are typically not entirely resistive.

Transmission system has resistance, inductance, capacitance and flow limitations.

Simple system has no redundancy so power system will not work if any component fails.


Power system examples

Power System Examples

Electric utility: can range from quite small, such as an island, to one covering half the continent:

there are four major interconnected ac power systems in North America (five, if you count Alaska), each operating at 60 Hz ac; 50 Hz is used in Pakistan

Airplanes and Spaceships: reduction in weight is primary consideration; frequency is 400 Hz.

Ships and submarines.

Automobiles: dc with 12 volts standard and higher voltages used in electric vehicles.

Battery operated portable systems.


Goals of power system operation

Goals of Power System Operation

Supply load (users) with electricity at

specified voltage (110 ac volts common for residential),

specified frequency,

at minimum cost consistent with operating constraints, safety, etc.


Major impediments

Major Impediments

Load is constantly changing:

Power system is subject to disturbances, such as lightning strikes.

Engineering tradeoffs between reliability and cost.


Units of energy

Units of Energy

  • The Capacity of an agent to do work is known as energy

  • Mechanical, electrical and thermal energy

  • Mechanical energy

    • Unit is Newton-meter or joule

    • Mech energy in jouls=Force in newtonxdistance in meters

  • Electrical energy units watt-sec or joule

  • One watt-sec or I joule of energy is transferred between two points if p.d. of 1 volt exists between them and one ampere of current passes for one second.

  • Elect energy in watt-sec or jouls=Voltage in voltsxCurrent in ampxtime in seconds


Units of energy1

Units of Energy

  • 1 watt-hour=1wattx1hour

  • =1wattx3600sec=3600 watt-sec

  • 1kilowatthour=1kwx1hour=1000wattsx3600se

  • =36x1o^5 watt sec

  • Heat

    • Heat is form of energy which produces sense of warmth. Units are Calorie, British thermal units (B.T.U) and centigrade heat units (C.H.U)


Units of energy2

Units of Energy

  • Calorie

    • Amount of heat required to raise the temperature of 1 gm of water through 1 Centigrade.

    • Ikcal=1Kgx 1C=1000gmx1C=1000 Calories

  • BTU

    • Amount of heat required to raise temp of 1 lb of water through 1 F

  • CHU

    • Amount of heat required to raise temp of 1 lb of water through 1 C


Relationship among energy units

Relationship among energy units

  • i) Electrical and Mechanical

    • 1KWh=1kwx1Hr=1000Wattsx3600Sec

    • =36X10^5watt-sec or joules

      ii) Heat and Mechanical

    • 1 Calorie=4.18 J (By experiment)

    • 1CHU=1lbx1C=453.6 gmsx1C=453.6Cals

      =453.6X4.18=1896 JOULS

      c) 1BTU=1lbX1F=453.6 gramsx5/9C=252 Calories

      =252x4.18 joules=1053 jouls


Relationship among energy units1

Relationship among energy units

  • iii) Electrical and Heat

    • 1KWh=3600000 Joules=3600000/4.18=860x10^3 Calories=860Kcals

      b) 1KWH=36X10^5 Joules=36x10^5/1896CHU=1898 CHU

      c) 1kWh=36x10^5/1053 BTU=3418 BTU


Efficiency

Efficiency

  • Output energy divided by input energy is called energy efficiency

  • Question

    • Energy is supplied to a d.c. generator at the rate of 4200 J/s. Generator delivers 32.2 A and 120 V

      • Calculate % efficiency of the generator?

      • How much energy is lost per minute of operation?

  • Ans

    • Input Power=4200J/s=4200W

    • Out put Power=EI=120X32.2=3864 W

    • %efficiency=3864/4200X100=92%

    • Power lost=4200-3864=336W

    • Energy lost per min=336X60=20160 J


Calorific value of fuels

Calorific value of Fuels

  • The amount of heat produced by the complete combustion of a unit wieght of fuel is known as its calorific value. In case of solid or liquid fuel, it is expressed as cal/gm or Kcal/kg. In case of gaseous fuels it is expressed as cal/litre or Kcal/lit


Comparison of fuels

Comparison of fuels

  • Advantages of liquid fuels over Solid fuels

    • i) handling of liq fuel is easier. Require less space

    • Ii)Combustion of liquid fuel is uniform

    • Iii)Solid fuels have higher moisture. Burn with difficulty

    • Iv)Waste product ash is cumbersome to dispose

    • V) Firing of liquid fuel can be controlled easily. Hence easy to manage load


Comparison of fuels1

Comparison of fuels

  • Advantages of Solid fuels over liquid fuels

    • i) Liquid fuels danger of explosion

    • Ii)Liquid fuels are costlier

    • Iii)Sometimes liquid fuels generate unpleasant odour while burning

    • Iv)Liquid fuels require special type of burners

    • V) Liq fuels need to be heated in cold weather to avoid freezing


Generating stations

Generating Stations

  • Bulk electric power is produced by special plants known as generating stations or power plants

  • A generating station employs a prime mover coupled to an alternator for production of electric power

  • Prime mover ( steam turbine or water turbine) converts some other form of energy into mechanical energy. Alternator converts mech to elect


Classification of generating stations

Classification of Generating stations

  • Steam power stations (Thermal )

  • Hydroelectric power stations

  • Diesel power stations

  • Nuclear power stations


Steam power station

Steam Power Station

  • A generating station which converts heat energy of coal combustion into electrical energy is known as steam power station

  • Steam produced in boiler

  • Steam is expanded in prime mover and condensed in condensor

  • Steam turbine moves alternator which converts mechanical energy into electrical energy


Steam power station1

Steam Power Station

  • Advantages

    • The fuel (i.e. coal) used is quite cheap

    • Less initial cost as compared to other generating stations

    • Installed at any location. Only coal needs to be transported

    • Requires less space as compared to hydroelectric

    • Cost of generation is less as compared to Diesel power stations


Steam power station2

Steam Power Station

  • Disadvantages

    • Pollution of air

    • Running cost more than Hydroelectric stations


Steam power station3

Steam Power Station

  • Schematic arrangement of Steam Power Station

  • 1 Coal and ash handling plant

    • Coal pulverised to increase surface exposure

    • Pulversied coal is fed to the boiler by belt conveyer. Coal burnt in boiler and ash removed

    • 100MW thermal power station on 50% load factor

      • Requires 20000 tons of coal per month; 10-15% of burned coal is ash produced


Steam power station4

Steam Power Station

  • 2 Steam generating plant

    • Boiler

    • Super heater

    • Economizer

    • Air preheater

  • 3 Steam turbine

  • 4. Alternator

  • 5 Feed water

  • 6 Cooling arrangements


Choice of site for steam power stations

Choice of site for Steam Power Stations

  • Supply of fuel

  • Availability of water

  • Transportation facilities

  • Cost and type of load

  • Nearness to load center

  • Distance from populated areas

liquid


Efficiency of steam power station

Efficiency of Steam Power Station

  • Overall efficiency of steam power station is quite low because huge amount of heat is lost in the condensor and heat loss occurs at various stages (29% overall efficiency)

  • Thermal efficiency: the ratio of heat equivalent of mechanical energy transmitted to the turbine shaft to the heat of combustion of coal is known as thermal efficiency of steam power station: 30%thermal efficiency

  • Overall efficiency: the ration of heat equivalent of electrical output to the heat of cumbustion of coal is known as overall efficiency: 29%


Equipment of power station

Equipment of Power Station

  • 1 Steam generating equipment:

    • i) Boiler: water tube boilers, fire tube boilers

      Water tube boilers less space, high working pressure ;less explosions

      ii) Boiler furnace; a) Plain refractory walls; b) Hollow refractory wallls c) Water walls

      iii) Super heater: made of special alloy steel such as Chromium-molybdenum a) Radiant Superheater b) Convection Superheater

      iv) Economiser


Equipment of power station1

Equipment of Power Station

  • V Air Preheater: a) Recuperative type b) Regenerative type

  • 2. Condensers: i) Jet condesers ii) Surface Condensers

  • 3. Prime Movers: steam engine and steam turbine i) Impluse turbine ii) Reactions turbine

  • 4. water treatment plant

  • Electrical equipment: i) alternators ii) transformers iii) switch gear


Hydro electric power station

Hydro-electric Power Station

  • A generating station which utilizes potential energy of water for generation of electrical energy is known as hydro-electric power station.

  • Hilly area, river or lake,

    Dam…….>water turbine……..> alternator

    Flood control, irrigation water and drinkable water


Hydro electric power station1

Hydro-electric Power Station

  • Advantages

    • No fuel required

    • Quite neat and clean

    • Small running charges

    • Simple construction and requires less maintenance

    • Does not require long starting time

    • Robust and has longer life

    • Irrigation and flood control

    • Less manpower to operate


Schematic arrangements of a hydro electric power station

Schematic Arrangements of a Hydro-electric power Station

  • Dam, Reservoir

  • Pressure Channel, Valve House: Main Sluice Valves and automatic isolating valves

  • Penstock, water turbine.

  • Surge tank protects penstock from bursting in case the turbine gates suddenly close due to electrical load being thrown off


Choice of site for hydro electric power station

Choice of site for hydro electric power Station

  • i) Availability of water

  • Ii) Storage of water

  • Iii) Cost and type of land

  • Iv) Transportation facilities


Constituents of hydro electric plant

Constituents of Hydro-electric Plant

  • Hydraulic structures

    • Dam: Concrete, stone masonry, earth or rock fill. Masonry dam for narrow canyons. Earth fill dam for wide valley

    • Spill ways

    • Headworks consists of the diversion structure at the head of an intake.

    • Surge tank is a small reservoir or tank in which water level rises or falls to reduce the pressure swings in the conduit


Constituents of hydro electric plant1

Constituents of Hydro-electric Plant

  • Hydraulic structures

    • V) Penstocks Open or closed conduits for carrying water to the turbines: Concrete penstock for low head <30m. Steel penstock are for any type of head. Thickness increases with head. Devices for protection include automatic butterfly, air valve and surge tank. Air valve minimizes vaccum


Constituents of hydro electric plant2

Constituents of Hydro-electric Plant

  • Water Turbines

    • i) Impulse Turbines

      • Used for high heads. Entire pressure of water is converted into kinetic energy in a nozzle. Example include Pelton wheel. Elliptical buckets. Needle or spear controlled by governor

      • Ii) Reaction Turbines

        • Used for low and medium heads

        • Francis Turbine and kaplan turbine

        • Fixed blades and runner blades

        • Reaction force are produced when water pressure and velocity are decreased when water falls on runner blades


Diesel power station

Diesel Power Station

  • A generating station in which diesel engine is used as the prime mover for the generation of electrical energy is known as diesel power station

  • For small power requirements

  • Transportation facilities are not adequate

  • Stand by arrangemnets


Diesel power station1

Diesel Power Station

  • Advantages

    • Design and lay out are simple

    • Occupies less space

    • Quick start and can pick load in a short time

    • Less quantity of water for cooling

    • Overall cost for comparable system of steam power generation is small

    • Thermal efficiency of the plant is high

    • Requires less operating staff


Diesel power station2

Diesel Power Station

  • Disadvantages

    • Fuel is costly

    • Does not work satisfactorily under prolonged over load conditions

    • Suitable for small power

    • Lubricant cost is high

    • Maintenance charges are high


Schematic arrangement of diesel power plant

Schematic arrangement of Diesel Power Plant


Schematic arrangement of diesel power station

Schematic Arrangement of Diesel Power Station

  • Fuel Supply System: storage tank, strainers, fuel transfer pumps and all day tank

  • Air Intake System:

  • Exhaust System: silencer

  • Cooling System: Heat released partly converted to work. The remaining heat passes through cylinder walls, pistons, rings. Cooling system consists of water source, pump and cooling tower


Schematic arrangement of diesel power station1

Schematic Arrangement of Diesel Power Station

v. Lubricating System

Vi Engine starting System: manual starting with handles for small sets. For large units compressed air is used


Nuclear power station

Nuclear Power Station

  • A generating station in which nuclear energy is converted into electrical energy is known as nuclear power station.

  • U235 or Th232(Thorium) are subject to nuclear fission reaction in reactor

  • Heat generated is used to produce steam at high temp and pressure

  • 1 Kg of U235 equivalent to 4500 tons of high grade coal


Nuclear power station1

Nuclear Power Station

  • Advantages

    • Small fuel. Transportation cost is saved

    • Requires less space

    • Low running charges

    • Economical for bulk production

    • Can be located near load center

    • Large deposits of fuel. Continues supply of energy for thousands of years

    • Reliability of operation


Nuclear power station2

Nuclear Power Station

  • Disadvantages

    • Expensive fuel and difficult to recover

    • Capital cost is high

    • Plant commissioning requires technical capabilities

    • Radioactive pollution

    • Maintenance charges are high. Highly costly skilled labour

    • Not suitable for variable load

    • By products to be disposed either in deep trench or sea bed


Nuclear power station3

Nuclear Power Station

  • i) Nuclear Reactor: Control of Chain reaction

    • Cylindrical pressure vessel

    • Fuel rods, moderators graphite and Control rods Cadmium

  • Ii) Heat Exchanger

  • Iii) steam turbine

  • Iv) Alternator


Selection of site for nuclear power station

Selection of Site for nuclear power station

  • Availability of Water

  • Disposal of Waste

  • Distance from populated areas: dome

  • Transportation facilities


Gas turbine power plant

Gas Turbine Power Plant

  • A generating station which employs gas turbine as the prime mover for the generation of electrical energy is known as gas turbine power station

  • Air is used as working fluid. Compressed air heated by burning fuel in the chamber or by use of air heater

  • Hot and high pressure air expands and does work in gas turbine

  • Compressor, gas turbine,and alternator are mounted on same shaft

  • Stand by for Hydro electric power plants


Gas turbine power plant1

Gas Turbine Power Plant

  • Advantages

    • Simple to design since no boilers are required

    • Much smaller in size compared to steam power station of same capacity

    • Initial and operating cost are low compared to steam power station

    • Requires less water as no condenser

    • Maintenance charges are small

    • Gas turbine are simple in construction and operation than steam turbines

    • Quick starting from cold conditions

    • No stand by losses. As in case of Steam power generations, boiler is to be kept in operation even in no load conditions


Gas turbine power plant2

Gas Turbine Power Plant

  • Disadvantages

    • Problem in starting. For Compressor power from external source is required. However, after start up turbine does not require external power

    • Greater power developed by turbine is utilized by compressor. Output is low

    • Overall efficiency is low 20% because exhaust gases contain sufficient heat

    • Life is less as combustion chamber temp is quite high 3000F


Gas turbine power plant3

Gas Turbine Power Plant

  • Compressor: rotatory type

  • Regenerator : device which recovers heat from exhaust gases of the turbine

  • Combustion Chamber: heat is added from burning oil. Chamber temp is 3000F. Combustion gases are cooled to 1300-1500F before delivering to turbine

  • Gas turbine: Expansion and work. Exhaust gases temp is 900F

  • Starting motor: for starting compressor. Battery operated motor


Comparison

Comparison


Comparison1

Comparison


Comparison2

Comparison


Variable load on power stations

Variable Load on Power Stations

  • Most Complexities are because of Load variations

  • Power is to be produced as and when required

  • Max efficiency vs load

  • Function of Power System is to connect Power Plant to the Consumers’ load by interconnected system of transmission and distribution netwok

  • Priniciple components of PS are: Power Station, transmission lines and distribution systems


Variable load

Variable Load

  • Effects of variable load

  • i) Need of additional equipment

  • Ii) increase in production cost

  • Load Curve: Curve showing load variation on the power station wrt time is called load curve

    • Daily load curve show variation

    • Area under the load curve gives number of units in the day

    • Peak demand

    • Av Load=Area under curve/24

    • Load factor: Ratio of area under the curve to the total load rectangle area=av load/max demand

    • Load Curve helps in planning operation of Power plant


Important terms

Important Terms

  • Connected load: It is the sum of continuous ratings of all the equipments connected to the system

  • Maximum demand: It is the greatest demand of load on the power stations during a given period. Max demand is less than connected load

  • Demand factor: max demand/connected load

  • Average load: The averages of loads occurring on power station in a given period is known as average load


Important terms1

Important Terms

  • Daily av load=No of units (KWH) generated in a day/24

  • Monthly av load=No of units generated in a month/number of hours in a month

  • Yearly av load=no of units generated in a year/8760 hrs

  • Load factor=Av load/max demand

    • =Units generated in T hours/Max demandXThours

  • Diversity factor=sum of individual max demands/max demand on power station


  • Important terms2

    Important Terms

    • Plant capacity factor= Actual energy produced/max energy that could have been produced

    • =Average demandxT /Plant capacityxT

    • =Av demand/Plant capacity

    • Annual plant capacity factor=annual KWH output/Plant capacityx8760

    • Reserve Capacity=Plant Capacity-Max demand

    • Plant Use factor=Station output in KWH/Plant capacityxhours of use


    Types of load

    Types of Load

    • i)Domestic Load

    • Ii)Commercial Load: lighting for shops, fans and electric appliances. Seasonal variation due to AC and heaters

    • Iii) Industrial load: small industry 25kW

      • Medium 25-500kW . Large > 500kw

  • Iv) Muncipal load: street lighting. Water motors

  • V) Irrigation Load

  • Traction Load: Railway, tram cars, trolly buses


  • Introduction to power engineering eee281

    • Typical Demand and diversity Factors

    • Load Curves and Selection of Generating Units: The number and size of units are selected in such a way that they correctly fit the station load curve

    • Ii)units of different capacities to meet load requirements

    • Iii) The capacity of the plant should be more than 15-20% of the max demand

    • Spare generating unit

    • Large generating units less


    Introduction to power engineering eee281

    • Base Load: The unvarying load which occurs almost the whole day on the station is known as base load

    • Peak load: The various peak demands of load over and above base load is known as peak load

    • More efficient plant to pick base load. Less efficient plant to supply peak load


    Interconnected grid system

    Interconnected Grid System

    • Interconnection of several generating stations in parallel is known as interconnected grid system

      • Exchange of peak loads

      • Use of older plants

      • Ensures economical operation

      • Increases diversity factor

      • Reduces plant reserve capacity

      • Increases reliability of supply


    Variable load on power stations1

    Variable Load on Power Stations

    • One line diagram

    • 2-3 3phase alternators: Voltage is 11-25KV

    • Step up500, 220 KV

    • Loads are in middle and south

    • Main hydel plants are Terbela, Mangla and Warsak

    • Small hydel units: Shadiwal, Nandipur, Chicho ki Millian, Renala Khurd

    • Main thermal plants are at Faisalabad, Multan, Kot Addu, Guddu, Hyderabad. Coal fired at Quetta


    Introduction to power engineering eee281

    • Chashma 900 Mw nuclear

    • Primary transmission 500, 220 and 132 Kv,66KV

    • Tarbella to jamshoro 500Kv

    • Primary Grid Stations

    • Secondary Grid Stataions/substations; being fed by primary or secondary transmission lines but are bascically meant to feed 33 11 KV distribution systems

    • In Wapda substations are distribution transformers


    Power factor improvement

    Power Factor Improvement

    • The cosine of angle between voltage and current in an a.c. circuit is known as power factor

    • Active or wattful Component

    • Reactive Component

    • Power Triangle

    • Disadvantages of low power factor

      • Large KVA rating: kVA=KW/Cos∂

      • Greater Conductor Size

      • Large Copper losses

      • Poor Voltage regulation

      • Reduced handling capacity of the System


    Power factor

    Power Factor

    • Causes of low power factor

      • Most ac motors induction type: low pf at light load 0.2-0.3 and rises to 0.8-0.9 at peak load

      • Arc Lamps, electric discharge lamps and industrial heating furnaces low pf

      • Variable load. Low load Supply voltage is increased by magnetization current; hence low pf

      • Power factor improvement

        • Static Capacitors

        • Advanatges

          • Low losses

          • Little maintenance

          • Easy installation

          • Ordinary temp


    Power factor1

    Power Factor

    • Disadvantages

      • Short service life 8-10 years

      • Easily damaged if voltage exceeds rated value

      • Once damaged repair is uneconomical

    • Synchronous Condenser

      • A Synchronous motor takes leading current when over excited

      • Advantages

        • By varying field excitation the magnitude of current can be changed

        • Motor windings have thermal stability to short circuit currents

        • Faults can be removed easily

      • Disadvantages

        • Considerable losses in motors

        • High maintenance cost

        • Noisy

        • Except 500kva , Cost is greater than that of static capacitor


    Power factor2

    Power Factor

    • Phase advancers

      • Used to improve pf of induction motor

      • Exciting ampere turns provided by external source, stator winding will be relieved of excitation and pf will be improved

      • Phase advancer is simply ac exciter

      • Connected on same shaft as the main motor and is connected to the rotor circuit of the motor

      • It provides exciting ampere turns to the rotor circuit at slip frequency

      • As exciting ampere turns are at slip frequency, lagging kVAR are significantly reduced

      • Not economical below 200 HP

    • Calculation of Power Factor Correction


    Importance of power factor improvement

    Importance of Power Factor Improvement

    • For Consumers: Tariff based on max demand in KVA and units consumed

    • For generating Station: higher pF higher KWH out put of the station

    • Most Economical power Factor

    • Meeting Increased kW demand on Power Stations

      • By increasing kvA Capacity

      • By improving power factor


    Electric supply system

    Electric Supply System

    • The conveyance of electric power from a power station to consumers’ premises is known as electric supply system

      • Three Components: Power station, transmission lines and distribution system

      • 3-Phase, 3 wire ac is universally adopted for generation and transmission

      • Distribution: 3 phase, 4 wire ac system


    Electric supply system1

    Electric Supply System

    • i) Generating Stations

      • 3 Phase Alternators operating in parallel

      • Voltages may be 6.6, 11, 33 KV. Most Common is 11 KV

      • Step up to 66, 132, 220, 400, 500 KV

      • High Voltage transmission: saving in conductor material and transmission efficiency. Limitation due to insulation problems, transformer cost etc.

      • Ii) Primary Transmission: From GS to outskirt of the city. Normally 3-phase 3 wire overhead lines with high vlotages; typical 132 KV


    Electric supply system2

    Electric Supply System

    • Iii) Secondary Transmission: Receing Station at out skirt. Reduction in voltage:132…..>33KV

    • Iv) Primary Distribution: Substation 33Kv……>11KV

      • 11KV lines run along important roads of the city. Big consumers with load more than 50KW are supplied at 11KV for further handling with their own substations

    • V) Secondary Distribution: Distribution substation: 400V, 3P, 4Wire for secondary distribution. Voltage between phase and neutral is 230V.

      • Feeders, Distributors and Service Mains


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