UET Power House Internship Report

REPORT

Power House UET, Lahore

Internship Report

Tue July 16, 2015

Mudasser Raheem 2013-EE-36

Electrical Engineering Department

University of Engineering & Technology

Lahore-Pakistan

BRIEF CONTENTS

Introduction

Brief History Of Electric Power

Electric Power System

Generation Of Electric Energy

Energy Supply And Consumption In Pakistan

Potential Available For Power Generation

Power Transmission

Power Distribution

Three Phase Power System

Star – Delta Connections

Power Transformer

Auto Transformer

132/220 KV Switchyard

Earthing

Protection Relays & Protection System Of Hydel Power Plant

Turbines & Generators

50/230V D.C Batteries

Auxiliary And Emergency Supply System

Fire Protection System

Electricity is the basic need for the economic development of any country. Electricity has now

become a necessity for all as it powers the machinery, the computers, the health-care systems

and the entertainment of modern society. Every power system has three major

components.which are as follows:

LoadT.L

Transmission Line

Generator

Figure 1.1. Components of a Power System

Generation: source of power, ideally with a specified voltage and Frequency.

Transmission system: transmits power; ideally as a perfect conductor.

Load: consumes power; ideally with a constant resistive value.

BRIEF HISTORY OF ELECTRIC POWER

1885 – invention of transformer

Mid 1880’s – introduce ac system

1893 – First 3 phase transmission line operating at 2.3 kV

Early 1900’s – Private utilities supply all customers in area (city); recognized as a natural

monopoly.

ELECTRICAL POWER SYSTEM

How electrical power system works in various places is defined in the figure given

below:

Figure 1.2. Typical Power System.

STEPS OF TYPICAL POWER SYSTEM:

1) The generating station converts the energy of gas, oil, coal or nuclear fuel to electric

energy. The generator voltage is around 15-25 kV (12.5KV at Mangla Dam Generation).

2) The main transformer increases the voltage to 230-765 kV. (220-500KV in Pakistan). This

reduces the current and losses.

3) The high voltage transmission line transports the energy from the generating station to

the large loads, like towns. Example: Energy generated at Palo Verde is transported by a

500 kV line to the KYRENE substation at Phoenix.

4) The high voltage substation reduces the voltage to 500-220 / (220-132) kV. The

substation serves as a node point for several lines.

5) The sub-transmission lines (132 kV-11 kV) connect the high voltage substation to the

local distribution station.

6) The Distribution lines 11 kV distribute the energy along streets or underground. Each

line supplies several step-down transformers distributed along the line.

7) The distribution transformer reduces the voltage to 240 (1-phase) or 415V (3-phase)

which supplies the houses, shopping centers, etc.

GENEARATION OF ELECTRICAL ENERGY

Electrical energy is generated at the power stations by synchronous generators. Typical

generation voltages vary from 3.3 to 33 kV depending upon the demand of the load.

GENERATION SOURCES IN PAKISTAN:

The Energy mix in Pakistan and various other countries for the year 2003-04 is

given in Table 1.1:

Sources Pakistan India UK USA Canada

Oil 30.0% 35.0% 35.0% 40.0% 30.0%

Natural Gas 50.0 % 7.0% 35.0% 23.0% 27.0%

Coal 1.0 % 55.0% 16.0% 23.0% 24.0%

Other (Hydel, Nuclear, etc.) 19% 3.0% 14.0% 14.0% 19.0%

Table 1.1 – Primary Energy Mix by Country 2003-04.

ENERGY SUPPLY & CONSUMPTION IN PAKISTAN

Source wise primary energy supply in Pakistan in 2003-04 is indicated below:

Gas Hydel Coal Nuclear

15.8 % 50.8 % 30 % 0.2 % Oil

Table: 1. 2 – Energy Supply in Pakistan 2003-04

Sector wise energy consumption, excluding fuels consumed in thermal power generation in

the Year 2004 is as follow:

Industry Transport Domestic Commercial Agriculture Other

Governments

38.3 % 32.0 % 21.7 % 3.2 % 2.5 % 2.3 %

Table 1.3 – Energy Consumption in Pakistan 2003-04

POTENTIAL AVAILABLE FOR POWER GENERATION

God has blessed Pakistan with tremendous potentials available for power generation is:

Hydel Potential

Coal Potential

MULTIPURPOSE PROJECT:

Following table presents the multipurpose projects whose feasibility are

completed.

Name of Project Capacity (MW) Feasibility Status

Kalabagh 3600 Completed

Munda 740 Completed

Basha 4500 In Hand

Total 8840

Table 1.4 – Future Multipurpose projects in Pakistan 2003-04

The electricity demand in the country is increasing day by day. The demand/supply

projections indicates that power shortage will appear from the year 2006, and will increase to

5500 MW in the year 2010 if no measures are taken to bring in new capacity.For Pakistan, the

cornerstone of self-reliance in power sector development is optimal utilization of hydel

resources.

Hydropower is cheaper, eternally available source of energy and a bounty of nature in contrast

to environmentally hazardous and non-renewable sources of energy. Pakistan is fortunate to

be endowed with economically exploitable hydropower potential of more than 50,000 MW.

There are vast resources of coal in Pakistan as well and coal is a cheap indigenous energy

resource. Pakistan’s coal resources may generate more than 100,000 MW of electricity for the

next 30 years.

The power requirements must be fulfilled by setting up new projects based on indigenous fuel

resources such as coal, hydel power, and renewable energies.

Development & utilization of indigenous available potential fuel resources will not only reduce

the cost of electricity but also strengthen the country’s economy and save precious foreign

exchange.

POWER TRANSMISSION

The power stations are located quite far away from the load centers. Transmission

networks are required to:q

Connect generating plants to consumption points

Create large power pools for increased reliability

The primary transmission voltages are 110, 132, 220 or 500 kV depending upon the distance

and amount of power to be transmitted. Secondary transmission is normally of the order of

66kV (obsolete in Pakistan now) and 132 kV.

High voltage AC transmission offers:

Higher transmission capacity / Km

Lower line-voltage drop / Km

Lower transmission losses / MW transfer

Reduced right-of-way requirement / MW transfer

Lower capital and operating costs / MW transfer

The equipment used for power transmission system is

Transformers

Step-up transformer

Voltage Regulators

Phase Shifters

Step-down Transformers

Transmission Lines & Cables

Relays & Circuit Breakers

Disconnectors &Earthing Switches

Shunt & Series Reactors & Capacitors

Static VAR Compensators

Current Transformers & Potential Transformers

POWER DISTRIBUTION

Power Distribution System receives electrical energy from the HV/MV levels at bulk

power delivery points and supplies energy to customers

At standard voltage levels

Single phase and/or three-phase

The voltages for primary distribution are 11, 6.6 or 3.3 kV depending upon the requirement of

bulk consumers and for secondary distribution the voltage level are 415/240V.

It is made up of the following main equipment:

Distribution transformers (DXF)

Feeder sections (including underground cables)

Switches, fuses, reclosures

Automatic load transfers

14

BulkPowerPoint

33/11DXF

11/5DXF

5/0.4/0.21DXF

HV / MV

Network

33KV 15 KV 5 KV220V

Industrial

Customers

Residential

Customers

Commercial

& Municipal

Customers

Large

Industrial

Customers

Power Distribution

Figure 4. Typical Power Distribution System

A distribution system may further be classified into feeders, distributors and service mains.

1. FEEDERS:

Feeders are the conductors, which connect the substations to the areas fed

by those substations. Generally feeders are not tapped at any point for supply to

the consumers, therefore, current density remains constant throughout the

length of the feeder. Hence, it is designed mainly for constant current carrying

density.

2. DISTRIBUTORS:

Distributors are the conductors from which load is tapped at different

points for supply to the consumers. The current density of a distributor does not

remains constant throughout its length. Distributors are designed mainly for

voltage drop in them. The voltage drop in a distributor should not exceed +- 5%.

3. SERVICE MAINS:

Service Mains are the conductors, which connect the distributor to the

consumer’s premises.

Figure 5. Elements of a Distribution System

UTILITY RESTRUCTURING:

Driven by significant regional variations in electric rates

Goal of competition is to reduce rates through the introduction

of competition

Eventual goal is to allow consumers to choose their electricity

supplier

In Pakistan, WAPDA is also under the process of disintegration. Eight Distribution

companies (Disco) are being constituted: which are

LESCO

GEPCO

MEPCO

IESCO

FESCO

KESC

PESCO

THREE PHASE POWER SYSTEM:

THREE-PHASE SUPPLY:

A three-phase supply is generated when three coils are placed 120° apart and the

whole rotated in a uniform magnetic field as shown in Figure 19.2(a). The result is three

independent supplies of equal voltages which are each displaced by 120° from each other

as shown in Figure 19.2(b).

The convention adopted to identify each of the phase voltages is:

R-red, Y-yellow, and B-blue, as shown in Figure 19.2.

Figure :Three-phase supply

The phase-sequence is given by the sequence in which the conductors pass the point

initially taken by the red conductor. The national standard phase sequence is R, Y, B.

A three-phase a.c. supply is carried by three conductors, called ‘lines’ which are coloured

red, yellow and blue. The currents in these conductors are known as line currents (IL) and

the p.d.’s between them are known as line voltages (VL). A fourth conductor, called the

neutral (coloured black, and connected through protective devices to earth) is often used

with a three-phase supply.

If the three-phase windings shown in Figure 19.2 are kept independent then six wires are

needed to connect a supply source (such as a generator) to a load (such as motor). To

reduce the number of wires it is usual to interconnect the three phases. There are two

ways in which this can be done, these being:

A Astar connection, and

A delta, or mesh, connection.

Sources of three-phase supplies, i.e. alternators, are usually connected in star,

whereas three-phase transformer windings, motors and other loads maybe co

either in star or delta.

BALANCED 3-PHASE SYSTEM:

A balanced 3 phase () system has

three voltage sources with equal magnitude, but with an angle shift of 120

equal loads on each phase

equal impedance on the lines connecting the generators to the loads

Bulk power systems are almost exclusively 3

Single phase is used primarily only in low voltage, low power settings, such as residential

and some commercial

ADVANTAGES OF 3-PHASE POWER S

Can transmit more power for same amount of wire (twice as much as single phase)

Torque produced by 3 machines is constant

Three phase machines use less material for same power rating

Three phase machines start more easily than single phase machines

THREE PHASE TRANSMISSION LINES:

phase supplies, i.e. alternators, are usually connected in star,

phase transformer windings, motors and other loads maybe co

PHASE SYSTEM:

) system has


equal loads on each phase


Bulk power systems are almost exclusively 3


PHASE POWER SYSTEM:


machines is constant

Three phase machines use less material for same power rating


THREE PHASE TRANSMISSION LINES:

phase supplies, i.e. alternators, are usually connected in star,

phase transformer windings, motors and other loads maybe connected






Figure:Three Phase Transmission Lines

STAR-DELTA CONNECTIONS:

The network shown in Figure (a) consisting of three mpedances ZA, ZB and ZC is said to be

p-connected. This network can be redrawn as shown in Figure (b), where the arrangement is

referred to as deltaconnected or mesh-connected.

Figure 34.1(a) Mesh connected network,

(b) Delta-connected network.

The network shown in Figure 34.2(a), consisting of three impedances, Z1, Z2 and Z3, is said to

be T-connected. This network can be redrawn as shown in Figure 34.2(b), where the

arrangement is referred to as starconnected.

Figure 34.2 (a) T-connected network.

(b) Star-connected network.

POWER TRANSFORMER

1 TRANSFORMERS:

A transformer is a static electrical device used in electric power systems to

transfer power between circuits through the use of electromagnetic induction. Transformers

are devices that transfer energy from one circuit to another by means of a common magnetic

field. When an alternating current flows in a conductor, a magnetic field exists around the

conductor. If another conductor is placed in the field created by the first conductor such that

the flux lines link the second conductor, then a voltage is induced into the second conductor.

The use of a magnetic field from one coil to induce a voltage into a second coil is the principle

on which transformer theory and application is based. Transformers range in size from

thumbnail-sized used in microphones to units weighing hundreds of tons interconnecting the

power grid. A wide range of transformer designs are used in electronic and electric power

applications. Transformers are essential for the transmission, distribution and utilization

of electrical energy.

1.1 INDUCTION LAW:

The transformer is based on two principles:

An electric current can produce a magnetic field.

A changing magnetic field within a coil of wire induces a voltage across the ends of

the coil (electromagnetic induction).

current passing through the primary coil creates a magnetic field. The primary and secondary

coils are wrapped around a core of very high magnetic permeability, so that most of the

magnetic flux passes through both the primary and secondary coils. Any secondary winding

connected load causes current and voltage induction from primary to secondary circuits in

indicated directions.

POWER TRANSFORMERS

The term power transformer is used to refer to those transformers used in the generator and the distribution circuits, and these are usually rated at 500 KVA and above. Power systems typically consist of a large number of generation locations, distribution points, and interconnections within the system or with nearby systems, such as a neighboring utility. The complexity of the system leads to a variety of transmission and distribution voltages. Power transformers must be used at each of these points where there is a transition between voltage levels.

http://en.wikipedia.org/wiki/Electric_power_transmission

http://en.wikipedia.org/wiki/Electric_power_distribution

http://en.wikipedia.org/wiki/Electric_power

http://en.wikipedia.org/wiki/Magnetic_field

http://en.wikipedia.org/wiki/Permeability_(electromagnetism

Figure :An example of a power transformer used in electric power system

AUTO TRANSFORMER

Transformer that acts like an isolation transformer by changing

Voltage Levels

Current Levels

Impedance values

But does not isolate between the Primary

CUIRCUIT DIAGRAM OF AUTO TRANSFORMER:

Circuit diagram of auto transformer is as follow:

Figure : Auto vs Isolation Transformer

An example of a power transformer used in electric power system

Transformer that acts like an isolation transformer by changing

But does not isolate between the Primary and the Secondary

CUIRCUIT DIAGRAM OF AUTO TRANSFORMER:

Circuit diagram of auto transformer is as follow:

Figure : Auto vs Isolation Transformer

An example of a power transformer used in electric power system

As a result:

Requires less copper

Lighter

I2R losses are less

More efficient

Lower leakage

Lower losses

Lower magnetizing current

Increase kVA rating

No galvanic Isolation

USE OF AUTO TRANSFORMER:

In power distribution lines to counteract line Z

Motor starting circuits

If there is an insulation breakdown between coils the supply voltage may be

imposed onto the low voltage load

It is recommended that the voltage reduction should only be by a maximum

of 25%

132/220 KV SWITCHYARD

Switchyard is basically switching scheme which may be termed as substation for

transmission while Planning and design of substations to be based on the following aspects:

Security of supply, extendibilty, maintainabilty and operational flexibility

Statutory safety requirements

Protection from direct lightening stroke

Switching scheme:-

765 kV Substation: Double bus double breaker

400 kV Substation: One and half breaker scheme/ double main and transfer bus

bar scheme

220 kV Substation: Double main and transfer scheme/ double main with breaker

by-pass scheme

132kV Substation: Main and transfer scheme.

EARTHING:

CONCEPT OF EARTHING SYSTEM:

All the people living or working in residential, commercial and industrial

installations, particularly the operators and personnel who are in close operation and contact

with electrical systems and machineries, should essentially be pro

electrification. To achieve this protection, earthing system of an installation is

defined,designed and installed according to the standard requirements

WHAT IS EARTHING:

The process of connecting metallic bodies of all the elec

equipment to huge mass of earth by a wire having negligible resistance is called Earthing.

term earthing means connecting the neutral point of supply system or the non current

carrying parts of the electrical apparatus to the gener

all times an immediate discharge of electrical energy takes place without danger.


tation: Main and transfer scheme.

EARTHING SYSTEM:



with electrical systems and machineries, should essentially be protected against possible


defined,designed and installed according to the standard requirements.

The process of connecting metallic bodies of all the electrical apparatus and

equipment to huge mass of earth by a wire having negligible resistance is called Earthing.


carrying parts of the electrical apparatus to the general mass of earth in such a manner that


Figure :Concept of Earthing




tected against possible


trical apparatus and

equipment to huge mass of earth by a wire having negligible resistance is called Earthing.The


al mass of earth in such a manner that


1 OBJECTIVES OF THE EARTHING:

Provide an alternative path for the fault current to flow so that it will not

endanger the user

Ensure that all exposed conductive parts do not reach a dangerous potential

Maintain the voltage at any part of an electrical system at a known value so as

to prevent over current or excessive voltage on the appliances or equipment.

1 GOOD EARTHING MEANS:

Good Earthing must have low impedance enough to ensure that sufficient

current can flow through the safety device so that it disconnects the supply ( <0.4

sec ). Fault current is much more than the full load current of the circuit which

melts the fuse. Hence, the appliance is disconnected automatically from the

supply mains.

1 QUALITIES OF GOOD EARTHING:

Must be of low electrical resistance

Must be of good corrosion resistance

Must be able to dissipate high fault current repeatedly

1 PURPOSE OF EARTHING:

To save human life from danger of electrical shock or death by blowing a fuse

i.e. To provide an alternative path for the fault current to flow so that it will

not endanger the user

To protect buildings, machinery & appliances under fault conditions ie. To

ensure that all exposed conductive parts do not reach a dangerous potential.

To provide safe path to dissipate lightning and short circuit currents.

To provide stable platform for operation of sensitive electronic equipments

i.e. To maintain the voltage at any part of an electrical system at a known

value so as to prevent over current or excessive voltage on the appliances or

equipment .

To provide protection against static electricity from friction

PROTECTION RELAYS & PROTECTION SYSTEM OF HYDEL POWER

PLANT

1 WHAT IS A RELAY?

(IEEE) define a relay as an electric device that is designed to interpret input

condition in a prescribed manner and after specified condition are met to respond to cause

contact operation .Relay are utilized in all as pacts of activity, the home ,communication ,

industry…..etc.

A protective relay is defined as a relay whose function is to detect defective line or apparatus

or other power system condition of an abnormal or dangerous nature and to initiate

appropriate control circuit condition. Fuse are also used in protection and define as an over

current protective device with in a circuit opening fusible part that is heated and severed by

the passage of the over current thought it.

A primary objective of all power system is to maintain a very high level of condition of service,

and to minimize the outage times when intolerable conditions occur. Loss of power, dip of

voltage and over voltage will occur due to consequences of natural events, physical accident,

equipment failure a disoperation by human error.

Protection is the science, skill, and art of applying and setting and / or fuses to provide

maximum sensitivity to fault and undesirable condition.

1 TYPICAL POWER CIRCUIT BREAKER:

Protective relays provide the "brains" to same trouble ,but as low energy device

they are able to open and isolate the problem area of the power system . CBs and varions

types of circuit interrupters are used to provide the "muscle" for fault isolation .

Thus protective relays and interrupting devices are "team" .protective relays without CBs have

no basic value except for alarm. On the other hand , CBs without protective relays are only

energized or de energized manually.

1 TYPICAL RELAY & CB CONNECTION :

Usually protective relays are connected to power system through CT and/or VT.

The circuit can be represented by a typical "one-line'" ac schematic and dc trip circuit

schematic as shown in fig (1-9) .in normal operation and when CB(52) is closed , it is contact

closes to energize the CB trip coil 52T, which function to open breaker main contact and de

energize the connected circuit. The relay contacts are not designed to interrupt the CB trip coil

current so an auxiliary relay is used to "seal in" or by pass the protective relay. Then 52a will

open to de energize the breaker coil.

Fig-1.9: Typical single –line ac connection of a protective relay with its de trip schematic

1 BASIC OBJECTIVES OF SYSTEM PROTECTION :

Protection does not mean prevention, but minimizing the duration of the trouble,

the five basic objectives are:

Reliability: assurance that the protection will perform correctly.

Selectivity: maximum continuity of service with minimum system disconnection.

Speed of operation: minimum fault duration and consequent equipment damage.

Simplicity: minimum protective equipment and associated circuitry to achieve the

protection objectives.

Economics: maximum protection at minimum total cost.

AUXILIARY AND EMERGENCY SUPPLY SYSTEM

GENERAL REQUIREMENTS

The A.C and D.C auxiliary services panels equipped with circuit breakers for

incoming and outgoing circuits, protective devices, instruments, meters, C.T's

and auxiliary equipment to be used with 200 kVA pad mounted transformer.

The cubicle for auxiliary services panels shall consist of three separate portions

with partitions of insulating material for separating A.C., D.C. and D.C. emergency portions.

The panels shall be designed for indoor use and shall be mounted on the floor.

The panels shall be designed throughout to secure safety during operation inspection and

maintenance.The auxiliary panel shall consist of bus bars, three phase and neutral for A.C and

positive and negative for D.C. main and emergency supplies, appropriate connections,

incoming and outgoing circuit breakers, A.C. no voltage relay D.C. under voltage and battery

earth fault relays, instruments, meters, annunciators, cable glands and cable trays all mounted

in a suitable metal enclosure.Thebreakers,instrumentsand meters shall be flush mounted.The

panel will befed through LT underground cables which will be connected directly to the A.C.

and D.C. incoming circuit breakers terminations.

FIRE PROTECTION SYSTEM

FIRE PROTECTION SYSTEM

The CO2 fire protection system for the gas turbine unites extinguishing the fire by

reducing the oxygen.

To reduce the oxygen content, a quantity of Co2 greater than 34% a compared by

volume is discharged in to the combustion chamber, when exposed to high

temperature.

OVER SPEED PROTECTION SYSTEM

Under normal operation the speed of the shaft is under the control of speed loop

or temperature loop.

The over speed protection system consists of a primary electronic system.

The primary electronic over speed protection system senses the turbine speed,

speed detection software and associated circuits.

Mechanical over speed protection system is a backup for electronic over speed

protection system failure.

OVER TEMPERATURE PROTECTION SYSTEM

The over temperature protection system protects the GT from possible damage

caused by over firing. It is a backup system which operates only after failure of the

speed and temperature over ride loops.

Control of turbine is done mainly by start up speed acceleration, synchronization

and temperature controls

Temperature, speed, vibration, flame and compressor operation limits over

temperature and over speed systems are provided as independent backup system

for temperature control and speed control systems.

Vibration detections and protection is activated by abnormal turning vibration

amplitude.

Flame Diction and protection system is activated if flame is not established during

start up or if it is lost during operation.

-----------------------------------------------------------------------------------------------------------------------

UET Power House Internship Report

Documents

Transcript of UET Power House Internship Report