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1. amp a prevents the effects from speeding into the system Working pricipal of relay with circuit breaker From the symbolic diagram we can see from the source line Electric power is coming through the CB to the Bus Bar Now if a fault _F i through the line Now we can see before CB a CT is there for protection CT ratio is designed to detect the fault current 1e if the current is more than the CT ratio then it is treat as fault current When such type of current is flow through line then CT secondary energized Bus bar Trip coil Relay coil Fig 9 2 Schematic diagram of relay with circuit breaker Page 72 The relay coil this relay coil close the path of trip circuit trip circuit get power by the DC source which energized the trip coil this trip coil give the trip pulse to the CB and CB is operate to open so the switchgear equipment s stay safe Fig block diagram of operation of Circuit breaker Classification of Relay The following important types of relays are generally used in electrical distribution amp transmission line i Induction type over current relay ii Induction type over voltage relay iii Distance relay iv Instantaneous relay v Differential relay vi Earth Fault relay vii Numerical relay viii Lock out relay Numerical Relay The numerical transformer protection unit RET316 4 is designed for the fast selective protection of two or three winding transformers In add
2. transformer has six separate windings three primary amp three secondary wound iron cores Enameled copper with insulation is used for winding Insulated papers are used for interlayer insulation Transformer Oil The tank is filled with transformer oil amp sealed It is a mineral oil obtained by refining crude petroleum It serves the following purposes Bs Provides additional insulation cg Carries away the heat generated in the core amp oils Good transformer oil should have high dielectric strength Low viscosity to provide good heat transformation Free from inorganic acid alkali amp corrosive Sulfur Free from sludging under normal operating condition It is Important to check the oil in regular intervals Page 31 Conservator It consists of an airtight metal drum fixed above the level of the top of the tank amp connected with the tank is completely filled with oil The conservator is partially is filled with oil The function of conservator is to take up construction amp expansion of oil without allowing it to come in contact with outside air Transformer oil will expand due to the heat generated because of losses Breather When the temperature changes expansion of contacts amp there is a displacement of air When the transformer cools the oil level goes down 7 air is drawn in The oil should not be allowed to come in contact with the atmospheric air as it may take moisture which may spoil it
3. 3 Three 50 Hz Dynl Three Phase ON Load Tap Changer HV LV A B C nabc 50 50 60 60 75 75 132 33 153 08 612 35 218 69 874 79 24 0 56 962 27 LI 650 AC 275 LI 200 AC 70 BS 171 IEC 76 33000 Volts in all Tap Positions 163843 ONAN Oil Natural Air Natural Page 82 ONAF Oil Natural Air Forced OFAF Oil Forced Air Forced 11 4 Transformer Vector Group The phase windings of a poly phase transformer can be connected internally in different configurations depending on what characteristics are needed from the transformer For example in a three phase power system it may be necessary to connect a three wire system to a four wire system or vice versa Because of this transformers are manufactured with a variety of winding configurations to meet these requirements Different combinations of winding connections will result in different phase angles between the voltages on the windings This limits the types of transformers that can be connected between two systems because mismatching phase angles can result in circulating current and other system disturbances Symbol Designation The vector group provides a simple way of indicating how the internal connections of a particular transformer are arranged In the system adopted by the IEC the vector group is indicated by a code consisting of two or three letters followed by one or two digits The letters indicate the winding configuration a
4. Fig 6 2 Transformer rating Page 33 LV Voltages and Currents in different tap position LEADS VoltS AMPS LV VOLTS LV AMPS Position JOINED T 33825 85 3 106 7 11550 249 9 312 4 8 33000 87 5 109 3 11550 249 9 312 4 32175 89 7 112 2 11550 249 9 312 4 31350 2 1 115 1 11550 249 9 312 4 Table 6 1 LV Voltages and Currents in different tap position dis Principal Tap Position 5 Step Voltage 1 25 of 11000 Volt 6 2 Parallel operation of single transformer 33KV Rf XY Y B T 4 Txl Tx2 Tx6 B 3x6KVA e uan www www 33X mmm mmm mm mmm GT mmm B R T Y i B 6 Fig 6 3 Parallel operation of single phase transformer Conditions l Primary windings of the transformers should be suitable for the supply system voltage and frequency 2 The Transformers should be properly connected with regard to polarity 3 The Transformers should have same turn ratio i e transformer ration The percentage impedances should be equal in magnitude and have the same X R ratio in order to avoid circulation currents Page 34 5 With transformers having different KVA rations the equivalent impedance should be inversely proportional to the individual ratings if the circulating currents are to be avoided Parallel operatio
5. 11 Operation amp Maintenance of S S 11 1 Operation 11 2 Transformer test 11 3 Transformer test on Annual maintenance for PGCB substation Savar 11 4 Transformer Vector Group 11 5 Maintenance of Circutt breaker Page 77 11 1 Operation To operate a grid substation there are some operation engineers under the supervision of the grid in charge In Tongi grid substation there are eight operation engineers 4 4 technical staff Shutdown work In the electrical system for any kinds of maintenance work on any section the must prerequisite is to assure the proper shutdown for that section For this the maintenance engineer will submit written request to the authority for shutdown of the specific part of the electrical system where maintenance is required After that the authority will take necessary steps to assure the proper shutdown of the specific part of the system All load feeders CB must be open which belongs to that transformer 1 Transformer secondary side 33kV CB ie Incoming CB open 2 Transformer 132kV side CB ie primary side CB open 3 Isolator open from both 132KV amp 33kV side 4 Grounding Switch Close from both 132kV amp 33kV side 5 Make additional grounding if required 6 Now the maintenance work can be started Shifting Duty i Make record of Power MW flow in each hour ii Make record of Energy MWh flow in each hour iii Switchgear equipment snpection iv Shutdown work v Load Management P
6. CONTETNS PAGE Declaration Acknowledgements Abstract Chapter 1 Organization 1 1 Introduction 1 2 Concerning Organization 1 3 Vision 1 4 Mission 1 5 REB Profile 1 6 Objective 1 7 Methodology 1 8 Organogram 1 9 Execuitve Members of Dhaka Palli Bidyut Samity 1 1 10 General Managers 1 11 Electricity Bill 1 12 Activities of Dhaka Palli Bidyut Samity 1 0 O t t RR Q N 1 13 Associations Chapter 2 Fundamental Information About Electrical System 2 Electric Power 9 2 2 Electricity 9 2 3 How Electricity Produces 10 2 4 Types of Electric current 10 2 5 How AC amp DC Generate 11 2 6 Some important terms 11 2 7 Basic Principle of AC generator 12 Page v 2 8 Basic Principle of DC generator 2 9 How are they used 2 10 Why use AC 2 11 Electrical circuits Chapter 3 Over view of Electrification system 3 1 Basic Content of Electrical system 3 2 Generation 3 3 Transmission 3 4 Distribution 3 5 Palli Bidyutap ofSamitys REBacrossBangladeshname 3 6 Map of PBSs Location Chapter 4 Electrical Sub 4 1 Definition of sub 4 2 Types of Sub Chapter 5 My Practicum Sub Station 5 1 DHAKA PALLI BIDYUT SAMITY 1 SAVAR 5 2 Single Line Diagram 5 3 Configuration of the Sub Station Chapter 6 33 11 KV Sub Station Equipme DPBS 1 6 1 Power Transformer 6 2 Parallel operation of transformer 6 3 Instrument Transformer 6 4 Definition of Switchgear 6 5 Insulator 6 6 Earthing Chapt
7. Fig 6 16 Suspension type insulator Page 45 3 Strain insulator When there is a dead end of the line or there is corner or sharp curve the line is subjected to greater tension In order to relieve the line of excessive tension strain insulators are used For low voltage lines shackle insulators are used as strain insulators For high voltage transmission lines strain insulator consists of an assemble of suspension insulator The discs of strain insulators are used in vertical plane Fig 6 17 Strain insulator 4 Guy insulator In PalliBiddyutSamity guy insulators are used in low voltage distribution 5 Stay insulator For low voltage lines the stays are to be insulated from ground at a height not less than 13 meters from ground 6 Shackle insulator Such insulators can be used either in a horizontal position or in a vertical position They can be directly fixed to the pole with a bolt or to the cross arm The conductor in the groove is fixed with a soft binding wire Fig 6 18 Shackle insulator Page 46 6 6 Earthing The word _earth or ground means many diff electrical installation these words can be used to mean either the protective conductor in a mains cord the common bonding network of the building the earth mass electrodes of the lightning protection system or the conductor of the mains supply that is connected to an earth mass electrode at the distribution transformer Page 47 C
8. Fig 8 11 Grounding Switch in close position Fig 8 12 Capacitor Bank Fig 8 13 power factor improvement Fig 9 1 Control Room for 33KV Switching sub station Fig 9 2 Schematic diagram of rela with circuit breaker Fig 9 3 Numerical Fig 9 4 Numerical Relay Fig 10 1 PGCB Duty Fig 10 2 Routine inspection Fig 10 3 Fixed contact is taken out for to maintenance Table Page Table 5 1 Configuration of the Sub Station 45 46 46 49 50 51 22 53 55 56 21 58 59 60 62 62 63 64 66 67 68 70 72 73 73 79 79 84 28 Page ix Table 6 1 LV Voltages and Currents in different tap position 34 References 87 Appendix 88 Page x Chapter 01 Organization 1 3 Introduction 1 4 Concerning Organization 1 5 Vision 1 6 Mission 1 7 REB Profile 1 8 Objective 1 9 Methodology 1 100rganogram 1 11Execuitve Members of Dhaka Palli Bidyut Samity 1 1 12 General Managers 1 11 Electricity Bill 1 12 Activities of Dhaka Palli Bidyut Samity 1 1 12 Associations Page 1 1 1 Introduction Electricity is the power that driving the whole world Now day we cannot think even moment without electricity Without electricity the civilization will go back to the thousands of epoch In every step of our modern life we are totally dependable on electricity This electric power comes to us by overcoming three steps these are eGeneration eTransmission eDistribution In our country Bangladesh Powe
9. Potential Transformer Potential transformer is used for voltage measurement and power system protection They are widely used in the power system for over voltage under voltage directional and distance protection The primary of the potential transformer is connected to the power circuit whose voltage has to be measured The secondary output gives a lower voltage which is very easy to measure by the common voltmeter The secondary winding turns of PT is designed to produce 110V irrespective of the primary voltage rating Fig 8 3 Potential Transformer Specifications 132KV OIL IMMERSED VOLTAGE TRANSFORMER TYPE OUTDOOR OIL IMMERSED SINGLE PHASE MODE JDCO F 132 TECHNICAL DETAILS RATED VOLTAGE HIGHEST 132KV VOLTAGE RATED 145 ROOT3KV FREQUENCY 50 OR 60HZ 132 ROOT3 0 L ROOT3 0 1KV RATED VOLTAGE RATIO 132 ROOT3 0 1 ROOT3 0 1 ROOT3 0 1K V Page 57 RATED VOLTAGE FACTOR 1 2 5 CONTINUOUS 1 5 TIMES 305 PARTIAL DISCHARGE UNDER NO MORE THAN 5PC 1 2UM ROOT3KV POWER FREQUENCY WITHSTAND VOLTAGE ON PRIMARY WINDINGS N TERMINAL 5KV RMS EARTH POWER FREQUENCY WITHSTAND VOLTAGE BETWEEN SECONDARY WINDING AND TO 3KV RMS EARTH MECHANICAL STRENGTH THREE 2000N DIRECTION 2 Current Transformer CT A current transformer CT is used for measurement of electric current When current in a circuit is too high to be measured directly by measuring instruments a current transformer produces a reduced current accurat
10. later in different area they arrange a meeting for awareness of use of electricity How they save the electricity How reduce the load shedding They not only arrange the meeting for electricity but also they call the meeting in different social work Page 6 1 13 Associations RURAL ELECTRIFICATION BOARD Website http www reb gov bd DHAKA PALLI BIDYUT SAMITY 1 Website http www dhakapbs1 org bd MINISTRY OF POWER ENERGY RESOURCES Website http www powerdivision gov bd DHAKA ELECTRICITY SUPPLY COMPANY LIMITED BANGLADESH POWER DEVELOPMENT BORD http www bpdb gov bd Page 7 Chapter 02 Fundamental Information about Electrical System 2 1 Electric Power 2 2 Electricity 2 3 How Electricity Produces 2 4 Types of Electric current 2 5 How AC amp DC Generate 2 6 Some important terms 2 7 Basic Principle of AC generator 2 8 Basic Principle of DC generator 2 9 How are they used 2 10 Why use AC 2 11 Electrical circuits Page 8 2 1 Electric Power The amount of electrical energy developed in one second is called electric Power The electric power in a circuit is calculated using the equation P VIcosg Electric power where electric current is used to energized equipments In modern life we cannot think even a single moment without this electric power In our daily life we need electricity We need electricity in every work what we do in our daily life Now the question is why this elect
11. speed of response Page 43 1 zi Lee 6 5 Insulator insulator serves two purposes They support the conductor confined the current the conductors The most commonly used material for the manufacture of insulator porcelain There are several kinds of insulator and their use in the sub station will depend upon the service requirement For example post Insulator is used for bus bars post insulator consists of a porcelain body cast iron cap and flagged cast iron base The hole in the cap is threaded so that bus bars can be directly bolted to the cap Fig 6 14 Insulator Page 44 Types of line Insulator e Pin type insulator e Shackle insulator e Suspension type e Stay insulator insulator e Strain insulator e Guy insulator 1 Pin type insulator Pin type insulators are used for transmission and distribution of electric power voltage up to 33KV Fig 6 15 Pin type insulator 2 Suspension type insulator For high voltage i e beyond 33KV transmission line Suspension type insulators used This type insulator consists of a number of porcelain discs connected in series by the metal links in the form of strength The conductor is suspended at the bottom end of this string while the other end of the string is secured to the cross arm of the tower Each unit or discs is designed for 11KV The number of discs in series would obviously depend upon the working voltage
12. 0 MW There are six 1 1kV outgoing feeder in DHAKA PALLI BIDYUT SAMITY 1 It s incoming feeder is con but the 11 KV outgoing feeders are controlled it Fig 5 1 33 11 KV Sub Station DHAKA PALLI BIDYUT SAMITY 1 SAVAR Page 26 5 2 Single Line Diagram DHAKA PALLI BIDYUT SAMITY 1 33 11 KV Sub Station Polashbari Savar Kabirpur Bismile Sub station Isolator Bypass 33 Fuse Isolator Savar Grid Sub station 33 KV bus bar ET Air Break Switch or Isolator Fuse Isolator L A P T 33 11 KV a TN 3X5MVA Yo 6 X 3 33 20 MVA 15 MVA LA Isolator Isolator r s o te Single Phase Single Phase Voltage Regulator 11KV Voltage Regulator 11KV N Isolator N Isolator Isolator Isolator Isolator Isolator 11 KV t 11 KV ACR ACR Isolator Isolator A Isolator Isolator Isolator Isolator 11KV Distribution 11KV_ Distribution Fig 5 2 Single line Diagram 33 11 KV sub station Page 27 5 3 Configuration of the Sub Station SI NO PARTICULERS 2 SUPPLIER amp CONSULTING CHINA NATIONAL ELECTRIC WIRE amp CABLE 3 POWER TRANSFORMERS NOS Three 03 NOS 33 11KV 5 6 22MV A EACH 4 POWER TRANSFORMERS ENERGYPAC ENGINEERING LTD BANGLADESH MANUFACTURER U 7 CIRCUITBREAKERTYPE 53 KV and 11 KV SF6 8 9 SF6 33KV 1250Amp A C R IKV 630 Amp 10 NAME OF NOS OF FEDDER FEEDER 1 FEEDER 2 FEEDER 3 FEED
13. During the separation of contacts due to large fault current and high current density at the contact region the surrounding medium ionizes and thus a conducting medium is formed This is called the ARC 1 Automatic Circuit Recloser 11KV U Series three phase pole mounted auto recloser or circuit breaker uses the latest technology in solid dielectrics vacuum interruption and insulants This device does not use any gas or oil insulants Instead cyclo aliphatic epoxy bushings are used to insulate the vacuum interrupters This type of construction results in a more lightweight unit The design has been optimised for automation remote control and monitoring applications and has built in current and voltage measurement for data logging Fig 6 9 Automatic Circuit Recloser Page 39 specifications Rated voltages 15 and 27k V Rated short circuit current up to 12 Rated load current up to 630 316 grade stainless steel tank Solid epoxy dielectric Vacuum arc interruption I terminal voltage measurement Optional X terminal voltage measurement Mechanical lockout Three phase current measurement Applications MV overhead network protection Substation circuit breakers Pole mounted reclosers Loop Automation Automatic Changeover Generator control Smartgrid Feeder Automation Page 40 2 SE6 Circuit Breakers for or 33 KV The U series Automatic Circuit Recloser ACR is a state of the art electronical
14. ER 4 11KV FEEDER 5 FEEDER 6 11 CONDUCTOR SIZE For 33 kv conductor size 477MCM For 11 kv conductor size 4 0 ACSR For lateral line 1 0 ACSR For sub lateral line 3 For pole to pole 4 0 1 0 3 6 12 BUS TYPE SINGLE BUS 13 FIRE FIGHTING EQUIPMENT TYPE NO CAPACITY amp NOS 14 LIGHTING ARRESTER 36KV 15 ISOLATOR 33KV 1250 Amps 16 ISOLATOR 1250 Amps 17 C T RATIO 400 5 18 COVERAGE AREA UNDER THIS SUB 911 Sq Km Table 5 1 Configuration of the Sub Station Page 28 Chapter 06 Sub Station Equipment sDescription 6 1 Power Transformer 6 2 Parallel operation of transformer 6 3 Instrument Transformer 6 4 Definition of Switchgear 6 5 Insulator Page 29 6 1 Power Transformer There are three transformers whose used in parallel of same ratings 1 5 6 25 So each transformer can provide 5 0 8 4 MW to Maximum 6 25 0 8 5 MW load By operating three transformer in parallel the sub station capacity is 4 3 12 MW to 5 3z 15 MW so the substation capacity is 15 MW Maximum for one side There are six extra power transformers are used two for per phase whose are rated as 3 333 MVA so each two transformer can provide 3 333x2 MVA 6 666 MVA By operation six transformers as parallel operation 6 666 x 3 MVA 20MVA The total maximum capacity for this sub station is 15 20 MVA 35 MVA load Basic Principle The transformer is based on two principles firstly that an electric current can pro
15. HOP CONNECTION amp DIS CONNECTION METER TEST amp REPAIR COMPLAIN CENTER Related to Line Meter Fig 1 01 Organogram 1 9 Execuitve Members of Dhaka Palli Bidyut Samity 1 DEPT HEAD REVENUE METER READING BILLING amp COLLECTION DEPT HEAD MEMBER SERVICE amp POWER USE FEASIBILITY STUDY MEMBER EDUCATION POWER USE CONSUMER SERVICES ONE POINT SERVICES CONSUMER COMPLAINS Reading Billing Line shifting related HOUSE WIRING amp INSPECTION MR GOLAM MORTUJA General Manager MD MAMUN MOLLA AGM CONSTRUCTION AND MAINTANANCE O P 5 1 10 General Managers The Board of Directors mainly makes policy decisions to manages business of the company The Board has delegated a few authority to the Managing Director and other Executive Directors to operate the day to day business of the company Each PBS has a General Manager The General Manager are as mentioned below e Brigadier General Moin Uddin Chairman REB e MR GOLAM MORTUJA General Manager Dhaka Palli Bidyut Samity 1 Ismail Hossain Chittagong Palli Bidyut Samity etc 1 11 Electricity Bill 1 75 unit dise 3 36 taka 75 200 unit 4 O5taka 201 300 unit 8taka4 1 301 400 unit 6 88 taka 401 600 unit 7 18 taka 600 secet 9 38 taka 1 12 Activities of Dhaka Palli Bidyut Samity 1 Every Forth month
16. OPERATION amp MAINTENANCE OF 33 11 KV SUBSTATION OF DHAKA PALLI BIDYUT SAMITY 1 A thesis submitted in partial fulfillment of the requirement for the degree of Bachelor of Science in Electrical and Electronic Engineering Supervised by Dr M Samsul Alam Professor amp Dean Dept of EEE Daffodil International University Submitted by Md Alvi Sarowar ID 101 33 128 amp Md Hasan Imam Majumder ID 101 33 200 Daffodi University Department of Electrical and Electronic Engineering DAFFODIL INTERNATIONAL UNIVERSITY DHAKA BANGLADESH FEBRUARY 2014 Page i DECLARATION We hereby declare that this thesisOperation amp Maintenancetitledof 33 11 KV Substation of Dhaka Palli Bidyut Samity 1 has been done by us under the supervision of Dr M Samsul Alam Professor amp Dean Department of Electronics and Electronic Engineering Daffodil International University We also declare that neither this thesis nor any part of this thesis has been submitted elsewhere for award of any degree or diploma Supervised by Dr M Samsul Alam Professor amp Dean Dept of EEE Daffodil International University Submitted by _ _ ee ee U8 G Md Alvi Sarowar ID 101 33 128 Department of EEE Daffodil International University Md Hasan Imam Majumder ID 101 33 200 Department of EEE Daffodil International University Page ii ACKNOWLEDGEMENT First off all we would like to express our cor
17. PBS 3 Jamalpur PBS ChapaiNawabgonj PBS a Gazipur PBS Page 19 3 6 Map of PBSs Location tool by ammap com Dhaka PBS 1 PBS Map of Bangladesh Fig 3 4 PBSs of REB Dhaka PBS 1 PBS Dhaka 5 1 Address Palashbari Savar Dhaka 1340 PBS Phone 01769400024 02 7791452 General Manager Mr A G M Mortuza Board President Page 20 Chapter 04 Electrical Sub Station 4 1 Definition of sub 4 2 Types of Sub Page 21 4 1 Definition of sub station The assembly of apparatus used to change some characteristics e g Voltage AC to DC frequency Power factor etc of electric supply is called sub station 4 2 Types of Sub Station Substations may be described by their voltage class their applications within the power system the method used to insulate most connections and by the style and materials of the structures used These categories are not disjoint to solve a particular problem a transmission substation may include significant distribution functions for example i Transmission substation ii Distribution substation iii Collector substation iv Converter substation v Switching substation vi Classification by Insulation substation vii Classification by Structure substation i Transmission substation A transmission substation connects two or more transmission lines The simplest case is where all transmission lines have the same voltage In such cases the substa
18. Technical Data 10361 Standard IEC ANSI BS amp AS Operating voltage max Rated power frequency withstand voltage 1 minutes 70 Impulse test voltage 1 2 50us 170 200 Rated frequency 50 or 60 Primary rated current 600 Maximum rated continuous thermal current 12 Secondary rated current Rated short time thermal current Ith 15ec Rated dynamic current 1dyn 2 5xlth Creepage distance min Short time load Mechanical Weight approx Page 37 Connection Diagram of CT and PT Connection Diagram of CT amp PT power conductor 7 current oO h ET high voltage power source dconnecli ger sai close switch BEFORE disconnecting ammeter atio rounded for a ae L 0 5 A meter movement range 0 120 VAC voltmeter range Fig 6 6 Connection Diagram of CT Fig 6 7 Connection Diagram of PT CT is connected in series with the circuit PT is connected in Parallel with the circuit 6 4 Definition of Switchgear Switchgear is an arrangement of some apparatus which are used to control amp protect the electrical circuits amp equipments Fig 6 8 Switchgear Page 38 Circuit Breaker CB A circuit breaker is equipment which can 1 Make or break a circuit either manually or automatically under normal conditions 2 Break a circuit under abnormal conditions A circuit breaker has two contacts Fixed amp Moving contact
19. age 78 Fig 11 1 PGCB Duty Routine inspection amp cleaning Routine inspection is done by the shift engineers amp routine cleaning is done by the technical stuffs Measuring the temperature of every joint is a part of daily inspection a thermo gun is use to measure the temperature It emits red laser light on the specific joint amp temperature reading is shown on its reading is taken below N N J OR EE Z 4i lt sg Fig 11 2 Routine inspection Page 79 i Emergency Maintenance Emergency maintenance is required when any uncertain hazard is occurred in the electric system ii Annual Maintenance In PBS 1 PGCB every end of the year they arrange annual maintenance schedule for every grid substation with a specific annual maintenance order 11 2 Transformer test Routine Tests Measurement of winding resistance Measurement of voltage ratio and check of phase displacement Measurement of short circuit impedance and load loss Measurement of no load loss and current Dielectric tests Separate source AC withstand voltage test Induced AC voltage test 09 SOY CUTS do UO qnx vb Partial discharge measurement Type Tests 9 Temperature rise test 10 Lightning Impulse tests Special Tests 11 Switching impulse voltage test 12 Measurement of dissipation factor tan 6 and capacitance 13 Measurement of zero sequence impedance s 14 Determination of sound level 15 Me
20. anizational point of view where it has been implemented There are so many improvements and applications that can be offered through this substation which of course would have direct benefit for the organization Page 86 References Principles of Power System by V K Mehta_ amp _Rohit_ Mehta A Hlectrical Textbook of Electrical Technology Vol 2 by POWER SYSTEM ANALYSIS 5th ed Protection Switchgear U A Bakshi and M V BakshiTheraja 4 htmhttp www ehow com list 5920618 types electrical currents html http www schoolphysics co uk age14 16 glance Electricity 20and 20magnetism Generator_dc index html PHPSESSID dca88 2092 bf5cda0d0f50e24300a64d53 http www ncert nic in html learning basket electricity electricity machine machine conte nt ht m http physicsstudents edublogs org wiki topic 12 12 2 1 2 http www school for champions com science electrical_generation htm http electronics polytech wikispaces com DC Generator http dc349 4shared com doc spDA wc9C preview html http macao communications museumf eng exhibition secondfloor moreinfo 2 4 1 ACGen erat or html http www one school net Malaysia UniversityandCollege SPM revisioncard physics electromagnetism ind uctio n html http www school for champions com science dc_circuits htm http ytcphyssci wikispaces com Ohm s Law http giszgqaiszmama blogspot com 2012 05 electricity parallel series circuit htm
21. ansmission line Fig 3 3 Underground Transmission line Fig 3 4 PBSs of REB Fig 4 1 Transmission line Fig 5 1 Sub Station PALLI BIDYUT SAMITY 1 SAVAR Fig 5 2 Single line Diagram 33 11 KV sub station Fig 6 1 Transformer core Fig 6 2 Transformer rating Fig 6 3 Parallel operation of single phase transformer Fig 6 4 Potential Transformer PT Fig 6 5 Current Transformer CT Fig 6 6 Connection Diagram of CT Fig 6 7 Connection Diagram of PT Fig 6 8 Switchgear Fig 6 9 Automatic Circuit Recloser Fig 6 10 SF6 Circuit Breaker Fig 6 11 Lightning arrester Fig 6 12 Air break switch Fig 6 13 Voltage regulator Fig 6 14 Insulator Fig 6 15 Pin type insulator 11 11 12 12 13 14 14 14 16 17 17 20 24 26 27 31 33 34 35 37 38 38 38 39 41 42 43 44 44 45 Page viii Fig 6 16 Suspension type insulator Fig 6 17 Strain insulator Fig 6 18 Shackle insulator Fig 7 1 One line diagram for 33 KV switching subs station Fig 7 2 Isolator Fig 7 3 Automatic Circuit Recloser ACR Fig 7 8 Current transformer CT Fig 7 9 Potential Transformer PT Fig 8 1 Transmission line Fig 8 2 One line diagram for 132 33 KV Grid sub station Fig 8 3 Potential Transformer Fig 8 4 Current Transform Fig 8 5 Isolator Fig 8 6 Automatic Circuit Recloser Fig 8 7 Lightning Arresters Fig 8 8 Lightering Arrester working principle Fig 8 9 Bus bar arramgement Fig 8 10 Power transformer
22. asurement of harmonics of the no load current A good transformer should have unbalances less than 1 Resistance Not more than 5 unbalance above 0 250 Ohms and 7 5 below 0 250 Ohms 2 Impedance lt 2 unbalance 3 Inductance 596 unbalance 4 Phase Angle Not more than 1 degree between phases Page 80 5 I F Not more than 2 digits difference and the readings should fall between 15 and 50 6 A shift in readings should be flagged for further testing or trending For instance a winding that tests as I F 48 48 46 and Phase Angle 70 70 69 should be checked further Normally a winding is beginning to experience inter turn shorts when the Phase Angle and I F begin to shift A corresponding unbalance in inductance and impedance indicates a severe fault A change in Phase Angle with a fairly balanced I F normally indicates a phase short For three phase transformer testing 1 All of the leads on the side opposite of the side being tested must be grounded to an earth ground 2 Test the primary from H1 to H2 then retest to verify that the readings are repeatable If they are not repeatable check the ground and continue 3 Test from H1 to H3 then H2 to H3 and finally a ground insulation test 4 Save the readings and check condition 5 Test the secondary winding by first checking X1 to X2 then retest to verify that the readings are repeatable If they are not repeatable check the ground and con
23. ated where arc is extinguish properly If the fault is temporary it automatically recloses the line after a few seconds Fig 7 3 Automatic Circuit Recloser ACR 3 Instrument Transformer A Current transformer The instrument current transformer CT steps down the current of a circuit to a lower value Andy s used in theentsameaspotentialtypestransformer ofThis is equipmdone by constructing the secondary coil consisting of many turns of wire around the primary coil which contains only few turns of wire In this manner measurements of high values of current can be obtained current transformer should always be short circuited when not 5 amperes For example a 4000 5 CT would provide an output current of 5 amperes when the primary was passing 4000 amperes The secondary winding can be single ratio or multi ratio with five taps being common for multi ratio CTs The load or burden of the CT should be of low resistance If the voltage time integral area is higher than the core s design rating the core goes into saturation towards the end of each cycle distorting the waveform and affecting accuracy Following the same line of thinking we can use a transformer to step down current through a power line so that we are able to safely and Page 51 easily measure high system currents with inexpensive ammeters Of course such a transformer would be connected in series with the power line like Figure oM Fig 7 8 Current transf
24. ave to find out of the following objectives They are follows e Study on Substation e Test and check the equipments of Substation e Identifying different types of problem which arise for operating this Substation e Suggest probable solution of the identified problem 1 7 Methodology Both primary and secondary data are being collected for the purpose of this report The report is concentrated of 33 11 KV Substation of Dhaka Polli Bidyut Somity 1 ePrimary Data Primary Data are collected from the books about power plants the Engineers through a face to face interview with a formal questionnaire the User Manual to the Engineers official documents of the company and Plant Operation Manuals e Secondary data Secondary data has been collected from the online resources Journals and Brochures Page 4 1 8 Organogram MEMBER CONSUMERS BOARD OF DIRECTORS GENERALMANAGER DY GENERAL MANAGER ENGINEERING CONSULTANT LEGALADVISOR DEPT HEAD GENERAL SERVICE DEPT HEAD DEPT HEAD ENGINEERING C O amp M DEPT HEAD ACCOUNTS LINE amp 5 5 MAINTENANCE amp OPERATION ADMINISTRATION SYSTEM ENGINEERING DESIGN amp PLANNING GENERAL ACCOUNTING LINE amp METER INSPECTION amp BANK MAINTENANCE RECONCILIATION PROCUREMENT MATERIAL amp STORE MANAGEMET METER PLANT PERSONNEL CONNECTION RE ACCOUNTING MINI VEHICLE MAINTENANCE ENFORCEMENT CONSTRUCTION Electric Line REPAIR WORKS
25. bar should be used 20 or 30 ampere greater than the load current o Every circuit breaker really has time setting option from O Isec If circuit breaker is more than one the time setting should be from 10ms to 80ms or 10ms to 15 from load circuit breaker to generator circuit breaker o Transformer oil and silica gel should be checked after one month or any types of fault occurs any time Oil should be changed if it is decomposed o Allcable should be cheek before use or any kinds o They use manually based equipment if they use PLC based equipment then the system will be easier o If they use new technology then the system loss will be reduce High system loss it will be reducing 12 2 Conclusion For a technical service provider plant O amp M activities are very important as its service mostly depends on the availability of its equipment To maintain properly it requires very efficient O amp M activities with minimum costing By using proper O amp M schedule of substation cost can be reduced and supply can be increased O amp M is traditionally classified as a part of output that comes from the system There are many diverse ways of evaluating O amp M of power system as well as different objectives O amp M comprises all measures for maintaining and restoring the target condition as well as determining and assessing the actual condition of the technical equipment in a system During this study it has been observed from the org
26. bles the fan to automatically run 6 Conservator Tank An oil preservation system in which the oil in the main tank is isolated from the atmosphere over the temperature range specified by means of an auxiliary tank partly filled with oil and connected to the completely filled main tank 7 Oil level indicator through this analog indicator oil can be measured Actually it indicates the oil level if the oil level inside the transformer is below the margin level then the transformer oil is fed by the power transformer 8 Temperature indicator through this analog indicator temperature of the oil is measured If the temperature of the oil is below the margin the force cooling system is run automatically or manually to keep the oil temperature below the margin temperature level 9 Bushing CT this bushing CT is use to measure the current of the primary winding of the transformer This measured value is monitored at the control room 10 Control box this box is used to control the transformer such as tap changing etc 8 9 Earthing of Station Transformer Two earthing transformer having provided in the 33 kV side of 132kV transformer Power transformers are using Delta Star connection So if any fault occurs in secondary side the earthing transformer grounds those current due to star connection So a neutral provided to power Trans formers Also it provides power for substation In this type of transformer Zigzag star and normal
27. bulbs and electric heating elements work fine on AC electrical power However there are some situations in which DC power is preferable For instance small electric motors e g those which power food mixers and vacuum cleaners work very well on AC electricity but very large electric motors e g those which power subway trains generally work much better on DC electricity Let us investigate how DC electricity can be generated Voltage V Time 0 90 180 270 360 Position of the coil Armature Field magnet Brush Split ring Fig 2 7 DC Generator Initially the armature is vertical No cutting of magnetic flux occurs and hence induced current does not exist When the armature rotates the change in flux increases and the induced current correspondingly increases in magnitude After rotating by 90 the armature is in the horizontal position The change in magnetic flux is maximum and hence the maximum induced emf is produced When the armature continues to rotate the change in flux decreases At the 180 position there is no change in flux hence no induced current exists The induced current achieves Page 13 its maximum value again when the armature is at 270 After rotating 360 the armature returns to its original position metal brush rotating split ring F adl a Fig 2 8 How Direct Current Produce lead to external circui 2 9 How are th
28. city The unit of the ampere A defined as 1 ampere 1 coulomb per second Circuit Breaker An automatic switch that stops the flow of electric current in a suddenly overloaded or otherwise abnormally stressed electric circuit D DPBS DHAKA PALLI BIDYUT SAMITY 1 F Frequency Number of cycles over a specified time period over which an event occurs Feeder The temperature to which oil must be heated in order to give sufficient vapor to form a flammable mixture with air under the conditions of the test The vapor will ignite but will not support combustion Page 88 G Generator A device that produces electric current usually by rotating a conductor in a magnetic field thereby generating current through electromagnetic induction H Hertz Hz Units in which frequency is expressed Synonymous with cycles per second values Machine language programs are often written in hexadecimal notation HT High Temperature cooling water circuit Imm Isolator A passive attenuator in which the loss in one direction is much greater than that in the opposite direction a ferrite isolator for waveguides is an example L Load The electrical demand of a process expressed as power watts current amps or resistance ohms Load sharing way in which two or more alternators run to accommodate the load demands from the electrical network LT side Low tension side l lt amp Operation Maintena
29. current generate by AC generator Page 10 Direct currents DC Direct current DC is the unidirectional flow of electric charge Direct current is produced by sources such as batteries thermocouples solar cells amp commentator type electric machines of the dynamo type 2 5 How AC amp DC Generate There must also be some way to transfer the current to the rest of the circuit In an AC generator having a ring on each end of the wire does this metal contact or brush rubs or slides against each ring allowing the electricity to flow through the circuit In a DC generator this is done using one split ring called a commutator Normally AC is produce inside every generator to make it DC we use split ring commutator instead of slip ring this split ring commutator make DC from AC An AC generator uses two slip rings as shown in figure DC with split ring Commutator commutator Carbon Direct Current brush Galvanometer Fig 2 4 DC Generator 2 6 Some important terms Magnetic field The space around a magnet where its influence is felt Magnetic flux The total number of lines of force around a magnet is called magnetic flux Electromagnet It is an arrangement of a soft iron piece inside a solenoid The magnet loses its property when the current in the solenoid ceases Galvanometer The device used to detect the presence and direction of a feeble current Page 11 2 7 Basic Pr
30. dial gratefulness to almighty Allah for his kindness for which we successfully completed our thesis within time and we also apologize to his for our any kind of mistakes We would like to express our boundless honor and respect to our thesis Supervisor Professor Dr M Samsul Alam Professor amp Dean Department of Electronics and Electronic Engineering Daffodil International University for his encouragement and for giving our permission to involve with electronics related thesis We have done my thesis according to his direction We would like to express our heartiest gratitude to Dr Md Fayzur Rahaman Professor and Head department of Electrical amp Electronic Engineering Daffodil International University and Ms Fahmida Hossain Tithi Sr Lecturer department of Electronics and Electronic Engineering I thank all staffs of my departments for their help during working period we must acknowledge with due respect the constant support and patients of our parents Finally we beg pardon for our unintentional errors and omission if any Page iii ABSTRACT As technology is advancing the consumptions of power is steadily rising There are three steps for proper electrification these are 1 1 Electric Power generation 1 2 Electric Power Transmission Hi Electric Power Distribution This three are equally important for proper electrification without any one of this three the electricity system will be incomplete Pow
31. duce a magnetic field electromagnetism and secondly that a changing magnetic field within a coil of wire induces a voltage across the ends of the coil electromagnetic induction Charging the current in the primary coil changes the magnetic flux that is developed The changing magnetic flux induces a voltage in the secondary coil The two circuits are electrically isolated but magnetically linked through a low reluctance path If one coil is connected to a c supply an a c is setup in both of these circuits This helps to transfer the voltage from one side to another We have observed two at DPBS 1 long with two station transformers They carry rated voltage 5K VA These transformers are used to supply power to the station at night or emergency case All the transformers are 33 11 KV and d y mode and each transformer is properly grounded Page 30 Accessories of transformers Core amp Winding T Fig 6 1 Transformer core It may be of various shape ie core shell It is made of cold rolled grain oriented Siliconsteel of varnish insulation on the lamination The core is laminated to reduce the core loss The laminations are made in steps amp try to give circular cross section Bolts 7 nuts secure the lamination The core is placed at the bottom of the tank The tanks are constructed from sheet steel for small tank amp boiler sheet for large tank There are thermometer pockets radiator tubes for increasing cooling surfaces 3
32. e will break down the air insulation and form an arc The property of the non linear resistor is that its resistance decreases as the voltage current increases and vice versa Power circuit Voltage R Non linear resistor Current Lightning arrester iY Fig 8 8 Lightering Arrester working principle Page 62 8 7 Bus Bar arrangement When a number of generators or feeders operating at the same voltage have to be directly connected electrically bus bars are used as the common electrical component Bus bars are copper rods or thin walled tubes and operate at constant voltage Below three types of bus bar system are mentioned L Single bus bar system H Single bus bar system with sectionalisation III Duplicate bus bar system Fig 8 9 Bus bar arramgement Page 63 S 8 Transformer Electrical Power Transformer is a static device which transforms electrical energy from one Circuit to another without any direct electrical connection and with the help of mutual induction between two windings It transforms power from one circuit to another without changing its frequency but may be in different voltage level 394 ee ry Control box e Oil level indicator Fig 8 10 Power transformer 1 Transformer Tank This holds the transformer windings and its insulating medium oil filled Transformer tanks must be air tightly sealed f
33. elds and changing magnetic fields generate electrical currents Page 9 Electric potential the capacity of an electric field to do work on an electric charge typically measured in volts Electric Resistance R amp Conductance G The electrical resistance of an electrical element is the opposition to the passage of an electric current through that element the inverse quantity is electrical conductance 2 3 How Electricity Produces The fundamental principles of electricity generation were discovered during the 1820s and early 1830s by the British scientist Michael Faraday His basic method is still used today Electricity is generated by the movement of a loop of wire or disc of copper between the poles of a magnet The basic theory of electricity production is If a Magnetic Poles x Magnetic Flux D Axis of Brushes Rotation s Fig 2 2 Rotating Conductor Conductor rotates inside the magnetic fields or fields rotate around the conductor in both cases the electric current flows through the conductor thus the electricity is produced But the must condition is either conductor or magnetic field must be rotate 2 4 Types of Electric current There are two types of electrical currents Direct currents DC Alternating currents AC Alternating currents A O In alternating current AC the movement of electric charge periodically reverses direction This
34. electrifying rural Bangladesh Since its inception the purpose of the program has been to use electricity as a means of creating opportunities for improving agricultural production and enhancing socio economic development in rural areas whereby there would be improvements in the standard of living and quality of life for the rural people Page 2 Today there 70 operating rural electric cooperatives called Palli Bidyuit Samity PBS which bring service to approximately 93 99 134 new connection being made and more than 2 42 116 kms of line has been constructed This eight month Study involved more than 100 male and female qualified enumerators as well as a number of data quality controllers working to collect quantitative and qualitative data through the completion of questionnaires during the interview of 378 cases in more than 70 villages thanas in both electrified and non electrified areas of 23 different PBSs dispersed across the country in addition the fieldwork also included 27 focus group discussion and nine group discussion with the PBS Board and Members The four major categories of consumers namely domestic commercial irrigation and industry were included when preparing the sampling sizes for both experimental and control groups Fourteen different instruments are designed field tested and used for the information collection phases of the Study Since its inception in 1980 Dhaka Palli Bidyut Samity 1 is playing a
35. ely proportional to the current in the circuit which can be conveniently connected to measuring and recording instruments Current Transformer steps down the current from high value to a low value that can be measured by a measuring instrument or fed to a protective relay for system protection and monitoring CTs are used extensively for measuring current and monitoring the operation of the power system Pw Fig 8 4 Current Transform Page 58 8 4 Isolator Isolator is used to disconnect any section or unit from all live parts of a substation It is normally a knife switch designed to open a circuit under no load The main purpose of using isolator is to isolate one portion of a circuit from the other It should never be opened until the circuit breaker in the same circuit has been opened and should always be closed before the circuit breaker is closed Isolators are usually placed on either side of the circuit breakers for safety during maintenance and troubleshooting Based on the position of the isolator in the system it can be classified in three ways 1 Line Isolator Isolates an incoming or outgoing line from the bus 2 Bus Isolator Isolates two section of the bus 3 Transformer Isolator Isolates the transformer from the bus or the lines eC d ATL T E m STAN DA E Y nw V Fig 8 5 Isolator Page 59 Isolator specification Electromotion operatin
36. ent of Electrical system Theelectricalsystemconsistsofthreemainsectors 1 Power station s that p ro d u c e electricity from combustible fuels coal natural gas biomass or non combustible fuels wind solar nuclear hydro power 2 Transmission lines that carry electricity from power plants to demand centers and 3 Transformers that reduce voltage so distribution lines carry power for final delivery Now we go for a brief discussion about the Electrification system As we know before that for a complete electrification system we need three steps sector these are i Generation ii Transmission iii Distribution 2 LLi a Power Station SS 1 Sm alli GENERATION Power Transformers Distribution Substation DISTRIBUTION Fig 3 1 Electrification System Page 16 3 2 Generation Electric power is generated by Electric Power Generating plants they are usually located near a source of water and away from heavily populated areas They are u sually quite large to take advantage of the economies of scale The electric power which is generated is stepped up to a higher voltage at which it connects to the transmission network 3 3 Transmission Fig 3 2 Overhead Transmission line Fig 3 3 Underground Transmission line After producing the electric power it transmit through the country by the transmission line system Electric utilities are tied together by transm
37. er 7 33 KV Switching Substation Savar of DPBS 1 7 One line diagram 7 2 Switch yard 13 14 14 14 16 17 17 18 18 20 22 22 26 27 28 30 34 35 38 44 46 49 50 Page vi Chapte 8 Savar 132 33 KV Grid Sub station of PGCB 8 1 Transmission line 8 2 One line diagram 8 3 Instrument Transformer 8 4 Isolator 8 5 Automatic Circuit Recloser 8 6 Lightning arrester 8 7 Bus Bar arrangement 8 8 Transformer 8 9 Earthing of Station Transformer 8 10 Grounding Switch 8 11 Capacitor Bank for Sub Station Chapter 9 Control Room 9 1 Main equipments of Control Room Chapter 10 Sub Station Protection 10 1 Protection against Lightning Chapter 11 Operation amp Maintenance of S S 11 1 Operation 11 2 Transformer test 11 3 Transformer test on Annual maintenance for PGCB substation Savar 11 4 Transformer Vector Group 11 5 Maintenance of Circuit breaker Chapter 12 Supplementary Part 12 1 Recommendation 12 2 Conclusion Figure Page Fig 1 01 Organogram Fig 2 1 Rotating fields Fig 2 2 Rotating Conductor 55 56 57 59 60 62 63 64 65 66 66 70 75 78 81 82 83 84 86 86 10 10 Page vii Fig 2 3 AC Generator Fig 2 4 DC Generator Fig 2 5 AC Generator Fig 2 6 How Alternating Current Produce Fig 2 7 DC Generator Fig 2 8 How Direct Current Produce Fig 2 9 Commutator of DC generator Fig 2 10 Pulsating DC Fig 3 1 Electrification System Fig 3 2 Overhead Tr
38. er Grid Company ltd is the BPDB Bangladesh Power Development Board wound company which is the only authorized company for the Electric Power Transmission sector in Bangladesh Rural Electrification Board REB has many sub stations all over the country which are connected through the distribution line these stations are called sub station This project paper provides the synopsis assessment of all the systems existing 33 11KV Dhaka Palli Bidyut Samity 1 Savar Rural Electrification Board REB has the vast electricity distribution network all over the country amp the electric power plants are connected with the transmission line to assure the continuity of electric power The electric power plants produce power amp feed in to the transmission line All power plants are connected parallel with the transmission and distribution line Dhaka Palli Bidyut Samity 1 Savar has AIS Air Insulated Switchgear switchyard Every sub station is controlled by some experienced manpower including one in charge 2 3 engineers 4 5 technical staffs All kinds of maintenance work of the sub station done by them in addition sub station operation work done by the engineers Every year annual maintenance work is done in every sub station in according to the official schedule This thesis report is prepared in according to the operation and maintenance procedure of 33 11KV Sub Station including emergency maintenance work Page iv TABLE OF CONTENTS
39. ey used In our country we have no DC transmission or distribution system We use DC in batteries solar cells IPS UPS amp lower voltage applications today But we have the AC transmission and distribution system in Bangladesh AC electricity currently provides the majority of the domestic power supply 2 10 Why use AC AC power can be controlled using transformers to increase or decrease the strength of the current while DC power is much harder to transform DC electricity also loses much more voltage when transmitted 2 11 Electrical circuits In terms of source basically there are two types of circuit i AC circuit The electrical circuit which is powered by AC source ii DC circuit The electrical circuit which is powered by DC source In terms of connection basically there are two types of circuit 1 Series circuit The electrical circuit where there is only one path for current flow is known as series a bi circuit i m w Source o ss Fig 2 9 Commutator of DC generator Fig 2 10 Pulsating DC Parallel circuit The electrical circuit where there is more than one path for current flow 18 known parallel circuit Page 14 Chapter 03 Over view of Electrification system 3 1 Basic Content of Electrical system 3 2 Generation 3 3 Transmission 3 4 Distribution 3 5 Palli Bidyut Samitys name and ma 3 6 Map of PBSs Location Page 15 3 1 Basic Cont
40. g device Type CJ6B Operation voltage 110 dc Operatin current 3 5a Control vltage 110 dc Control current la Numner 0901080 Year 12december 2008 Weight 50 g 8 5 Automatic Circuit Recloser It is an one kind of switchgear and protection device When any type of fault such as ground fault line fault short circuit fault etc it works properly Besides this due to maintenance of the substation to isolate the line at first it through it line can be isolated where arc is extinguish properly If the fault is temporary it automatically recloses the line after a few seconds Fig 8 6 Automatic Circuit Recloser Page 60 Specifications Page 61 8 6 Lightning arrester Lightning arresters are protective devices used to divert the surge voltage due to lightning It is used in electrical power system to protect the insulation on the system from the damaging effect of lightning In times of lightening it conducts the high voltage surges on the power system to the ground Fig 8 7 Lightning Arresters Working Principle of Lightning Arrester The figure shows a basic form of a surge arrester It consists of a spark gap in series with a non linear resistor One end of the diverter is connected to the terminal of the equipment to be protected and the other end is effectively grounded The length of the gas is so adjusted that normal line voltage is not enough to cause an arc across the gap but a dangerously high voltag
41. h works when is fail There is also a battery charger These batteries arrangement supplies about 110 V and high ampere So the main equipments installed in control room are listed below 1 High tension panel 2 Low tension panel 3 Bus bar coupling 4 Power factor improvement coupling panel 5 Back up battery 6 Battery charger 7 Relay panel Fig 9 1 Control Room for 33KV Switching sub station Page 70 1 High Tension Panel this is a panel where 132kv or 33 kv switchgears are operated line voltage line current phase voltage power factor etc values are measured and monitored Due to fault condition it automatically operates the high tension switchgears For each feeder the is a H T panel 2 DC system of the Sub Station Storage Battery A cell is a device in which an electrical difference of potential is established between the two electrodes as a result of chemical reaction between the electrode amp electrolyte There are two types of cell 1 Primary cell 2 Secondary or storage cell A Lead acid cell B Alkaline cell Working Principle When the ve plate of Lead per Oxide amp ve plates of spongy lead are immersed in dilute amp H2SO4 amp connected together by means of external circuit current flows round the circuit The cell works until the per Oxide is used up amp under this condition the cell is said to be discharging The cell under fully discharged condition Positive Plate PbO2 Negat
42. hapter 07 33 KV Switching Substation Savar of DPBS 1 7 One line diagram 7 2 Switch yard Page 48 This is a switching sub station from where Dhaka Palli Bidyut Samity 1 and other PBSs controlled It has thirteen feeders from where different PBSs are feed power Actually it is consists of a feeder controlling room and a switching yard All controlling such as line current each feeder line and phase voltage for each feeder are measured by many Low Tension L T panel and High tension panel H T Switch yard is the place where the actual equipments are working properly 7 1 one line diagram TATION BCT 600 4001 T 2 X4ormer 417T 2400 1600 1 GCB T 2 Sec ingao China SINGLE LINE DIAGRAM OF SAVAR 33KV SWITCHING SUB STATI 132KV Main Bus Twin Martin 2000A i 1 3 GCB T 1 Sec ingao China T 1 X4ormer 407T 132 33kv 50 75 TEBA China Dyn 1 Z 1554 Jr Asstt Manager by Md Hasan Al Rajib Jr Md Rezaul Hague Asstt Manager ked b Prepa Fig 7 1 One line diagram for 33 KV switching subs station Page 49 This switching sub station is mainly consists of two parts as below 1 Switchyard 2 Control Room The main components are described below briefly 7 2 Switch Yard This is a large place where switch gear components are paced according to the one line diagram which is provided by an experienced electrical engineer after elec
43. inciple of AC generator We know when a conductor cuts magnetic flux then an emf is induced on the conductor This emf is induced by Faradays law of electromagnetic induction The induced emf is directly proportional to the time rate of change of magnetic flux linked with it Cycle Fig 2 5 AC Generator Fig 2 6 How Alternating Current Produce The armature is initially at the vertical position No magnetic flux is cut and hence no induced current exists When the armature rotates the change in magnetic flux increases and the induced current increases until its maximum value at the horizontal position As the armature continues on its rotation the change in magnetic flux decreases until at the vertical position no induced current exists Subsequently upon reaching the horizontal position again the induced current is maximum but the direction of the induced current flowing through the external circuit is reversed The direction of the induced current which flows through the external circuit keeps on changing depending on the orientation of the armature This induced current is also known as alternating current The current is positive in one direction and negative in the other The slip rings play a critical role in the generation of alternating current Page 12 2 8 Basic Principle of DC generator Most common electrical appliances e g electric light
44. ires are placed over line conductors at such position that practically all lightning strokes are intercepted by them The ground wire is ground at each tower or pole through as low resistance as possible When the direct lightning strokes occur on the transmission line will be taken u by the ground wire The heavy current flows to the ground through the ground wire so it protects the line from harmful effects of lightning Page 75 3 Lightning arrester Lightning arresters are protective devices for limiting surge voltages due to lightning strikes A lightning arrester is a device used on electrical power systems to protect the insulation and conductors of the system from the damaging effects of lightning The typical lightning arrester has a high voltage terminal and a ground terminal When a lightning surge or switching surge which is very similar travels along the power line to the arrester the current from the surge is diverted through the arrestor in most cases to Technical Specification Type 2 120 Max Rating 120 KV 10 KA Heavy Duty Station Class Pressure Relief Class B Long Duration Discharge 1 Unit Sections 2 Manufacturer Bowthorpe England Year of Manufacture 1991 4 Fire Protection The fire protection device should be kept in store yard for safety of equipment s during storage It can be useful in the time of danger This includes fire extinguishers constant supply of water etc Page 76 Chapter
45. ission lines into large systems called power grids They are thus able to exchange power so that a utility with a low demand can assist another with a high demand to help prevent a blackout which involves the partial or total shutdown of a utility There are two types of electric power transmission 1 Overhead transmission ii Underground transmission A major goal of overhead power line design is to maintain adequate clearance between energized conductors and the ground so as to prevent dangerous contact with the line and to provide reliable support for the conductors resilient to storms ice load earthquakes and other potential causes of damage Today overhead lines are routinely operated at voltages Page 17 exceeding 765 000 volts between conductors with even higher voltages possible in some cases Transmission lines when interconnected with each other become transmission networks these are typically referred to as power grid the network is known as the National Grid and the sub station at which the transmission lines are linked is called Grid Sub Station 3 4 Distribution Electricity distribution is the final stage in the delivery of electricity to end users A distribution system s network carries electricity from the transmission system and delivers it to consumers Typically the network would include medium voltage less than 50 KV power lines substations and pole mounted transformers low voltage le
46. ition the application for the protection of auto transformers and block generator transformer units is possible The relay will detect different kinds of faults Fig 9 3 Numerical Fig 9 4 Numerical Relay Page 73 Chapter 10 Sub Station Protection 10 1 Protection against Lightning Page 74 10 1 Protection against Lightning Transients or Surges on the power system may originate from switching or other causes but the most important amp dangerous surges are those which caused by lightning The lightning surges may cause serious damage t transmission lines that reach the ssaryequipmentto provide a protection against lightning surges they are 1 Earth Screen 2 Overhead Ground Wire 3 Lightning Arrestor 4 The Fire Protection 1 Earth Screen The power stations amp the substations are ge These stations can be protected from direct lightning strikes by providing earthing screens It consists of a network of Copper conducto in the substation or Power station The screen is properly connected to earth on at least two points through low impedance On the occurrence of direct stroke on the station the screen provides a low resistance path by which lightning surges are connected to the ground In this way station equipment sning are protected a 2 Overhead Ground Wires The most effective method of providing protection against direct lightning strokes is by the use of overhead ground wires The ground w
47. ive plate Pb Electrolyte dil H2SO4 sp Gravity 1 25 During discharge The chemical action can be represented by the following chemical equation At ve condition PoO2 H2 H2SO4 PbSO4 2H20 At ve condition Pb SO4 PbSO4 During Charging When a direct current from an external source is passed through it from positive to negative the following the following changes will occur At ve plate PbSO4 So2 2H20 PbSO04 2H20 At ve plate PbSO4 H2 Pb H2SO4 Color of the plate at the end of the charge becomes Positive plate Dark Brown Negative plate Slate Gray The batteries are connected to the circuit breaker for tripping the circuit breaker Here trip is used through type relays Page 71 3 Protective relay Relay Definition A protective relay is a device that detects the fault and initiates the operation of the C B is to isolate the defective element from the rest condition in the electrical circuit by constantly measuring the electrical quantities which are different under normal and fault condition The electrical quantities which may change under fault condition are voltage current frequency and phase angle Having detected the fault the relay operates to close the trip circuit of C B There are two principle reasons for this firstly if the fault is not cleared quickly it may cause unnecessary interruption of service to the customer Secondly rapid disconnection of faulty apparatus limits the amount of damage to it
48. l Burden Current 8h earth fault winding A 6 Rated Voltage Factor 1 2 Un Continous Creepage distance min mm 1230 Short time load Mechanical N 3750 Weight approx kg 70 2 Current Transformer CT The instrument current transformer steps down the current of a circuit to a lower value Andy s used in the same typesrmer ofThis is equipmentdone by constructing the secondary coil consisting of many turns of wire around the primary coil which contains only few turns of wire In this manner measurements of high values of current can be obtained A current transformer should always be short circuited when not 5 amperes For example a 4000 5 CT would provide an output current of 5 amperes when the primary was passing 4000 amperes The secondary winding can be single ratio or multi ratio with five taps being common for multi ratio CTs The load or burden of the CT should be of low resistance If the voltage time integral area is higher than the core s design rating the core goes into saturation towards the end of each cycle distorting the waveform and affecting accuracy Following the same line of thinking we can use a transformer to step down current through a power line so that we are able to safely and easily measure high system currents with inexpensive ammeters Of course such a transformer would be connected in series with the power line like Figure Page 36 Fig 6 5 Current Transformer CT
49. l http farside ph utexas edu teaching 3 16 lectures node9 1 html http www infoplease com ce6 sci A0860502 html http kiran111 hubpages com hub electrical substation http heag en alibaba com product 325207748 200603654 JW_252 Outdoor High Voltage Earthing Switch html http en wikipedia org wiki Capacitor voltage transformerhttp www alibaba com product free 11479573 Mcr310 Draw Out Module Over Current htmlhttp www circuitmaniac co m 2009 03 19 self balance system over current and earth fault protection Page 87 Appendix A AC Alternating Current Alternator A synchronous AC generator Alternator rotor The rotor consists of a coil of wire wrapped around an iron core B Bus bar The metal often copper bar system which is the distribution media for the 3phase high voltage system in the power plant Current Transformer electrical engineering current transformer is used for measurement of electric currents Current transformers are also known as instrument transformers Capacitor A device capable of storing electric energy It consists of two conducting surfaces separated by insulating material It blocks the flow of direct current while allowing alternating current to pass Conductor A wire or cable for carrying current CT Short for Current Transformer An AC current measuring the generators to share the reactive component of the Current The rate of flow of electri
50. ly controlled outdoor pole mounted three phase recloser The pole top circuit breaker is one of the manufacture s family of outdoor circuit b automation schemes Fig 6 10 SF6 Circuit Breaker Sulfur hexafluoride SF6 gas is an alternative to air as an interrupting medium SF6 is a colorless nontoxic gas with good thermal conductivity and density approximately five times that of air The principle of operation is similar to the air blast breakers except that the SF6 gas is not discharged into the atmosphere A closed circuit completely sealed and self contained construction is used SF6 Circuit Breakers are mostly use in Indoor type Primary sub stations in Sri Lanka and other countries because of its convenience 1 2 3 4 Good heat transfer quantity Pressure can be checked easily Short arcing time Compartmented SF6 HV load break isolating switch Page 41 Specifications mo SOME TEL NTE T MANUFAC 3 Lightning arrester Lightning arresters are protective devices for limiting surge voltages due to lightning strokes lightning arrester is a device used on electrical power systems 0 protect the insulation and conductors of the system from the damaging effects of lightning The typical lightning arrester has a high voltage terminal and a ground terminal When a lightning surge or switching surge which is very similar travels along the power line to the arrester the current from the surge is diver
51. n of three phase transformer Conditions 1 All the conditions for the single phase transformer are applicable for 3 phase transformer The voltage ration must refer to the terminal voltage of primary and secondary 3 The phase displacement between primary and secondary voltages must be the same 4 The phase sequence must be the same 5 the transformers in the 3 phase transformer bank will be the same construction either core or shell 6 3 Instrument Transformer 1 Potential Transformer PT Transformers can also be used in electrical instrumentation systems Due to transformers ability to step up or step down voltage and current and the electrical isolation they provide they can serve as a way of connecting electrical instrumentation to high voltage high current power systems Potential transformers are designed to provide as accurate a voltage step down ratio as possible To aid in precise voltage regulation loading is kept to a minimum the voltmeter is made to have high input impedance so as to draw as little Fig 6 4 Potential Transformer PT Page 35 PT PRODUCT DESCRIPTION Technical Data Type VT036 2 Standard IEC ANSI BS amp AS Connection Line to line Connection Operating voltage max kV 36 Rated power frequency withstand voltage 1 minutes kV 70 Impulse test voltage 1 2 50us kV 170 200 Rated frequency Hz 50or 60 Primary Voltage V 36000 Secondary Voltage 100 240 Secondary Therma
52. nce Parallel operation one unit supplying power to same network Phase line A line in an electrical network having system voltage potential PLC Programmable Logic Controller Power factor The extent to which the voltage zero differs from the current zero p f kW kVA Page 89 PT Potential Transformer PGCB Power Grid Company Of Bangladesh Ltd R REB Rural Electrification Board S SF6 SulphurHexa Fluoride Circuit Breaker Voltage droop The difference in voltage at no load and full load expressed as a percent of the full load value Voltage regulator A device which maintains the voltage output of a generator by other electrical equipment Y Y connection An interconnection of the phases of a three phase system to form a configuration Resembling the letter Y A fourth neutral wire Page 90
53. nd in such cases it is generally desirable to take special steps to improve the power factor This can achieved by the following equipment i Static capacitors ii Synchronous condenser Phase advancers Static capacitor Power factor can be improved by connecting capacitors in parallel with the equipment operating at lagging power factor The capacitor generally known as static capacitor draws a leading current and partly or completely neutralizes the lagging reactive component of load current This raises the power factor of the load For three phase loads the capacitors can be connected in delta or star as shown in fig 04 Static capacitors are invariably use for power factor improvement in factories Page 67 Fig 8 13 power factor improvement Page 68 Chapter 09 Control Room 9 01 Main equipments of Control Room Page 69 9 01 Main equipments of control room It is a room from where all the switchgear equipments are controlled Here all the equipments are connected through grounding wire or underground cable When any operation is done the associated operation is done by motor control This room is equipped with high tension panels H T and low tension panels L T whose are connected with the associated switchgear equipments The line voltage line current phase voltage power factor etc values are monitored in this room These values are recorded in a note book It has also a battery backup section whic
54. or it to isolate its content from any atmospheric contaminants 2 High Voltage Bushing this is the terminals where the primary windings of the transformer terminates and serves as an insulator from the transformer tank Its creapage distance is dependent on the voltage rating of the transformer 3 Low Voltage Bushing like the high voltage bushing this is the terminals where the secondary windings of the transformer terminates and serves as an insulator from the transformer tank Low voltage bushing can be easily distinguished from its high voltage counterpart since low voltage bushings are usually smaller in size compared to the high voltage bushing Page 64 4 Cooling Fins Radiator in order for the transformer to dissipate the heat it generated in its oil insulation cooling fins and radiators are usually attached to the transformer tanks The capacity of the transformer is dependent to its temperature that is why it is imperative for it to have a cooling mechanism for better performance and higher efficiency 5 Cooling Fans can be usually found attached to the cooling fins Cooling fans can be either be a timer controlled or a winding oil temperature controlled Cooling fans helps raises the transformer capacity during times when the temperature of the transformer rises due to its loading Cooling fans used on the transformer are actuated by the help of a relaying device which when senses a relatively high temperature ena
55. ormer CT B Potential Transformer PT Transformers can also be used in electrical instrumentation systems Due to transformers ability to step up or step down voltage and current and the electrical isolation they provide they can serve as a way of connecting electrical instrumentation to high voltage high current power systems Potential transformers are designed to provide as accurate a voltage step down ratio as possible To aid in precise voltage regulation loading is kept to a minimum the voltmeter is made to have high input impedance so as to draw as little It has an ration such as if the ration is like this 500 5 it means if primary voltage is 500V then the secondary voltage is 5V Page 52 Fig 7 9 Potential Transformer PT Specifications 35kV Voltage Transformer TYPE SINGLE PHASE OIL IMMERSED OUTDOOR MODE JDXF 35W2 RATED VOLTAGE 36kV FREQUENCY 50 60HZ POWER FREQUENCY WITHSTAND VOLTAGE 95kV IMPULSE WITHSTAND VOLTAGE 200kV RATED PRIMARY VOLTAGE 33 ROOT 3 kV RATED RATIO 33 ROOT3 0 11 ROOT 3 0 11 ROOT 3 0 11 ACCURACY CLASS 0 2 0 5 6P Page 53 Chapter 08 Savar 132 33 KV Grid Sub station of PGCB 8 1 Transmission line 8 2 One line diagram 8 3 Instrument Transformer 8 4 Isolator 8 5 Automatic Circuit Recloser 8 6 Lightning arrester 8 7 Bus Bar arrangement 8 8 Transformer 8 9 Earthing of Station Transformer 8 10 Grounding Switch 8 11 Capacitor Bank for Sub Station Page 54 As 33KV Sa
56. r Development Board BPDB is the mother organization in electric power sector BPDB regulate all company in electric power sector There are some companies in electric power generation and distribution sector but in transmission sector Power Grid Company of Bangladesh Ltd PGCB is the only company in Bangladesh and Rural Electrification Board REB including Palli Bedyut Samity PBSs is one of the largest distributer around this country 1 2 Concerning Organization Bangladesh Power Development Board BPDB was assigned to manage power transmission system power generation and power distribution throughout Bangladesh before formation of Power Grid Company of Bangladesh Ltd PGCB but Rural Electrification Board REB is the most larger power distributor throughout the countryside The Rural Electrification Board of Bangladesh has been providing service to rural member consumers for over 36 years Continued support from the Government of Bangladesh the donor community consulting partners and member consumers will help this program continue to expand providing the gift of electricity to millions more Bangladeshi households businesses and industries The Bangladesh Rural Electrification RE Program was founded with a Presidential Ordinance in October 1977 that established the Rural Electrification Board REB as the semi autonomous government agency reporting to the Ministry of Power Energy and Minerals Resources Which was responsible for
57. rent or the reverse Formerly rotary converters changed frequency to interconnect two systems such substations today are rare v Switching substation A switching substation is a substation which does not contain transformers and operates only at a single voltage level Switching substations are sometimes used as collector and distribution stations Sometimes they are used for switching the current to back up lines or for parallelizing circuits in case of failure An example is the switching stations for the HVDC Inga Shaba transmission line vi Classification by insulation Switches circuit breakers transformers and other apparatus may be interconnected by air insulated bare conductors strung on support structures The air space required increases with system voltage and with the lightning surge voltage rating For higher voltages gas insulated switchgear reduces the space required around live bus Instead of bare conductors bus and apparatus are built into pressurized tubular containers filled with Page 23 sulfur hexafluoride SF6 gas This gas has a higher insulating value than air allowing the dimensions of the apparatus to be reduced In addition to air SF6 gas apparatus will use other insulation materials such as transformer oil paper porcelain and polymer insulators vii Classification by structure Outdoor above ground substation structures include wood pole lattice metal tower and tubular metal struc
58. ric power is must for modern life The best answer is electric power is the convenient power which can be converted in to any power as our requirements such as 2 2 Electricity Electricity is the set of physical phenomena associated with the presence and flow of electric charge Electricity gives a wide variety of well known effects such as lightning static electricity electromagnetic induction and the flow of electrical current In electricity charges produced electromagnetic fields which act on other charges Electricity occurs due to several types of physics Electric charge A property of some subatomic particles which determines their electromagnetic interactions Electrically charged matter is influenced by and produces electromagnetic fields Electric current A movement or flow of electrically charged particles typically measured in amperes In other word we can say that the flow of electron is called current Electric Voltage Voltage is the potential energy that makes the electrical current flow in a circuit by pushing the electrons around The unit of voltage is volt Electric field An especially simple type of electromagnetic field produced by an electric charge even when it is not moving i e there is nonelectric current The electric field produces a force on other charges in its vicinity Moving charges additionally produce a magnetic field Electromagnets Electrical currents generate magnetic fi
59. s insulating properties Air may cause acidity or sledging of oil so the air coming in is passed through an apparatus called breather for extracting moisture The breather consists of a small vessel which contains a drying agent like Silica gel crystal Bushing It is fixed on the transformer tank and these connections is made to the external circuits Ordinary porcelain insulators can be used as bushing up to voltage of 33 kV Above 33kv oil filled type bushings are used In filled bushings the conductor is passed through the hollow porcelain insulator which is filled with oil Tap Changing Mainly 132 33 kV transformer uses on load tap changing amp 33 11 kV transformer is used of load off load tap changing The tap changer is generally done on H V side because current flow is less than LV side Which reduces the flashing during the tap changing Here tap changed in 132 33 kV transformer Page 32 Technical data amp 14001 COUT DOOR ONAN ONAF 33 11 AN ISO 9001 TRANSFORMER TYPE TYPE OF COOLING RATED MVA Hv iv RATED KV 5 RATED LINE Hv 87 57109 3 CURRENT Amp 249 9 312 4 VECTOR GROUP 1 NO OF PHASES 5 IMPEDANCE HV LV EID CERTIFIED COMP ANY OPTG PRESSURE OF PRV STANDARD cle MASS OF OIL TOTAL MASS FREQUENCY TRANSPORT MASS INSULATION LEVEL CORE amp COIL TANK amp FITTINGS
60. s follows 1 D Delta winding also called a mesh winding Each phase terminal connects to two windings so the windings form a triangular configuration with the terminals on the points of the triangle 2 Y Wye winding also called a star winding Each phase terminal connects to one end of a winding and the other end of each winding connects to the other two at a central point so that the configuration resembles a capital letter Y The central point may be connected outside of the transformer 3 Z Zigzag winding or i nt e rc on ne cte d s t ar win di n g Basically similar t o a star winding but the windings are arranged so that the three legs are bent when the phase diagram is drawn Zigzag wound transformers have special characteristics and are not commonly used where these characteristics are not t h e transformer at all and must be connected externally Page 83 11 5 Maintenance of Circuit breaker Yearly the circuit breakers are required to maintain It is required to measure the ohms between the two conductors whose are namely fixed contact and moving contact If the measuring value is small it is good for the system Fig 11 3 Fixed contact is taken out for to maintenance Page 84 Chapter 12 Supplementary Part 12 1 Recommendation 12 2 Conclusion Page 85 12 1 Recommendation The following points should be developed o Allinstruments should be clearance between two equipment o Bus
61. ss than 11 KV distribution wiring 3 5 Palli Bidyut Samitys name and map of REB across Bangladesh Electricity distribution sub stations throughout the country are given below of REB whose are connected to a 33 KV line coming from grid sub stations The location name map of the sub stations are shown below PBSs Name PBSs Name PBSs Name Dhaka PBS 1 Chittagong PBS 1 Faridpur PBS EM Tangail PBS Bogra PBS Jhenaidah PBS Comilla PBS 1 Thakurgaon PBS Rajshahi PBS 277 2 3 Chandpur PBS 5 Madaripur PBS Kur Lalmoni PBS Hobigonj PBS Barisal PBS 2 Magura PBS E Moulvibazar PBS 29 Chittagong PBS 2 Brahman Baria PBS Pabna PBS 1 Meherpur PBS Mymensingh PBS 2 EX Pabna PBS 2 Noakhali PBS Nilphamari PBS EN Sirajgonj PBS Bagerhat PBS Gopalgonj PBS Jessore PBS 1 Narsingdi PBS 1 Bhola PBS Page 18 Jessore PBS 2 Kishoreganj PBS Rajbari PBS Natore PBS 1 Narsingdi PBS 2 Sylhet PBS 2 13 Natore PBS 2 36 Naogaon PBS 59 Shariatpur PBS NU Rangpur PBS 1 Sylhet PBS 1 Munshigonj 5 Satkhira PBS Laximipur 5 Dhaka PBS 2 Feni PBS Barisal PBS 1 Sunamgonj PBS Mymensingh PBS 1 Patuakhali PBS Sherpur PBS 18 Dinajpur PBS 1 4 Manikgonj PBS 64 Mymensingh PBS 3 i Dinar PST Sr Raise Nee Kushtia PBS Comilla PBS 2 Gaibandha PBS Joypurhat PBS Cox s Bazar PBS 66 Jhalakati PBS 2 Pirojpur PBS 44 Dinajpur PBS 2 67 Khulna PBS Pein PBS fia EA Rangpur PBS 2 Netrokona PBS 68 Chittagong
62. star connections are used Zigzag star is used in H V sides amp normal stars are used in L V side Here in the H V side zigzag stars used because it reduces the heating effect of fault current amp makes it robust Page 65 8 10 Grounding Switch Grounding switch provide safety during maintenance work For any maintenance work the safety steps that must be taken is Step 1 Load CB must be open Step 2 Isolator must be open Step 3 Grounding switch must be close When maintenance work is done the reveres processes must be done Grounding Switch is close position Fig 8 11 Grounding Switch in close position Specifications Type RD 303 812668 Manufacturer Hawker Siddeley UK Commissioning 1994 Rated Voltage 132 KV Max Voltage 145 KV Rated Current 1250 Amps Short Time Current 31 5 KA for 3 Sec Rated Lighting Impulse Withstand 650 K V 8 11 Capacitor Bank for Sub Station The capacitor banks are used across the bus so that the voltage does not get down below the required voltage When the inductive property of the line increases then the voltage lags behind current amp causes loss of money so to raise the voltage up amp prevent loss of money capacitor banks are used It raises the voltage raises power factor as well Page 66 Fig 8 12 Capacitor Bank Normally the power factor of the whole load on a large generating station is in the region of 0 8 to 0 9 However sometimes it is lower a
63. ted through the arrestor in most cases to earth Page 42 4 Air Break switch Air break switches are used in electrical substations to allow isolation of apparatus such as circuit breakers and transformers and transmission line for maintenance work to ensure the maximum safety Air break switches must be used at no load condition Fig 6 12 Air break switch 5 Voltage Regulator A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level It may use an electromechanical mechanism or passive or active electronic components Depending on the design it may be used to regulate one or more AC or DC voltages With the exception of shunt regulators all voltage regulators operate by comparing the actual output voltage to some internal fixed reference voltage Any difference is amplified and used to control the regulation element This forms a negative feedback servo control loop If the output voltage is too low the regulation element is commanded to produce a higher voltage For some regulators if the output voltage is too high the regulation element is commanded to produce a lower voltage however many just stop sourcing current and depend on the current draw of whatever it is driving to pull the voltage back down In this way the output voltage is held roughly constant The speed of response control loop must be carefully designed to produce the desired tradeoff between stabilityand
64. tinue 6 Test from X1 to X3 then X2 to X3 and finally a ground insulation test 7 Save the readings and check condition For single phase transformer Single phase transformers are tested slightly differently and require a known reading for the primary to be compared to such as with a similar transformer or a past test on the same transformer The basic steps for single phase transformer testing are as follow 1 All of the leads on the side opposite of the side being tested must be grounded to an earth ground 2 Test the primary from H1 to H2 then retest to verify that the readings are repeatable If they are not repeatable check the ground and retest Page 81 3 Ground the primary then test X1 to X2 then retest to verify that the readings are repeatable If they are not then check the ground and retest These procedures can be used on three phase pad mount and single phase pole mount transformers regardless of connection type 11 3 Transformer test on Annual maintenance for PGCB substation Savar Transformer Rating Sheet Job Description 50 75 132 33 KV 3 phase 50Hz Power Transformer Number of Phase s Rated Frequency Vector Group Connections Type of Tap Changer Winding Designation Terminal Notation Rated Capacity in MVA ONAN ONAF OFAF Rated Voltage in kV Rated Current in Ampere ONAN ONAF OFAF Basic Insulation level in kV Line Terminals Standard LV Voltage Serial No
65. tion contains high voltage switches that allow lines to be connected or isolated for fault clearance or maintenance A transmission station may have transformers to convert between two transmission voltages voltage control power factor correction devices such as capacitors reactors or static VAR compensators and equipment such as phase shifting transformers to control power Page 22 ii Distribution substation A distribution substation transfers power from the transmission system to the distribution system of an area It is uneconomical to directly connect electricity consumers to the main transmission network unless they use large amounts of power so the distribution station reduces voltage to a value suitable for local distribution iii Collector substation In distributed generation projects such as a wind farm a collector substation may be required It resembles a distribution substation although power flow is in the opposite direction from many wind turbines up into the transmission grid Usually for economy of construction the collector system operates around 35 kV and the collector substation steps up voltage to a transmission voltage for the grid iv Converter substations Substations may be associated with HVDC converter plants traction current or interconnected non synchronous networks These stations contain power electronic devices to change the frequency of current or else convert from alternating to direct cur
66. trical calculation The main components are described below 1 Isolator In Sub Station it is often desired to disconnect a part of the system for general maintenance and repairs This is accomplished by an isolating switch or isolator An isolator is essentially a knife Switch and is design to often open a circuit under no load in other words isolator Switches are operate only when the line is which they are connected carry no load For example consider that the isolator are connected on both side of a cut breaker if the isolators are to be opened the C B must be opened first If an isolator is opened carelessly when carrying high current the resulting arc easily causes flashover to earth This may batter the supporting insulators amp may even cause a fatal accident to the operator particularly in the high voltage circuit The operating principle is manual plus one of the following Electrical Motor Mechanism 2 Pneumatic Mechanism Isolators cannot be opened unless the Circuit Breakers are opened Circuit Breakers cannot be closed until isolators are closed 15 DSN 4 y 4 Fig 7 2 Isolator Page 50 2 Automatic Circuit Recloser It is an one kind of switchgear and protection device When any type of fault such as ground fault line fault short circuit fault etc it works properly Besides this due to maintenance of the substation to isolate the line at first it through it line can be isol
67. tures although other variants are available Where space is plentiful and appearance of the station is not a factor steel lattice towers provide low cost supports for transmission lines and apparatus Low profile substations may be specified in suburban areas where appearance is more critical Indoor substations may be gas insulated switchgear at high voltages or metal enclosed or metal clad switchgear at lower voltages A Primary power lines side Secondary power lines side Primary power lines 2 Ground wire 3 Overhead lines 4 Transformer for measurement of electric voltage 5 Disconnect switch 6 Circuit breaker 7 Current transformer 8 Lightning arrester 4 1 Transmission line Page 24 Chapter 05 My Practicum Sub Station 5 1 DHAKA PALLI BIDYUT SAMITY 1 SAVAR 5 2 Single Line Diagram 5 3 Configuration of the Sub Station Page 25 5 1 DHAKA PALLI BIDYUT SAMITY 1 SAVAR 33 11 DHAKA PALLI BIDYUT SAMITY 1 sub station is one of the important power sub stations of Dhaka because it supplies power to the Industrial area in Saver amp locality Kabirpur and Savar Grid Substations are the original source for DHAKA PALLI BIDYUT SAMITY 1 sub station The Sub Station is AIS Air Isolated Sub Station Capacity of the Sub Station is 35 MVA There are three power transformer of 5 6 25 MVA there are also six transformers rating 3 333 MVA whose are connected in parallel Maximum load of the Sub Station is 3
68. var switching sub station of REB is feed power by Savar 132 33 KV Grid Sub station so authorized sent me to visit the Savar 132 33 KV Grid Sub station of PGCB Power Grid Company of Bangladesh which is one of the power generation and transmission company So I am going to discuss about 132 33 kv PGCB sub station details the main components are discussed below 8 1 Transmission line This PGCB Grid sub station is feed power from Aminbazar 1 and Aminbazar 2 through double circuit transmission line of 132kv Fig 8 1 Transmission line Transmission line double circuit Name of Transmission line Aminbazar 1 and Aminbazar 2 commissioning 2010 tower 95 Nos Route Length 60 k m Conductor size 635 MCM ACSR Page 55 8 2 One line diagram 4 a comte i n L t 3 e LL a 2 enin 104 3 iVdS es 2 1 899 Briss 1 79 Vo0SZ Plqenig 4eq sng 296 1 1 829 oe voooz unjew um sng Jejsue11 t o MES ge0z 899 acor 829 104 2 34 vdS 10 5 2 4 2 8 L UVZVENINV Page 56 Main components of Savar 132 33 KV Grid Sub station of PGCB 8 3 Instrument Transformer 1
69. vital role in Agricultural Industrial and Socio Economic Development of Dhaka District The Rural Electrification Program conducted by Dhaka Palli Bidyut Samity 1 has acted a leap forward in the development of socio economic structure of rural areas in Dhaka District as well as entire Bangladesh If has significant and sustained impact on agricultural growth industrialization and business amp commercial activities in the rural areas It is a consumer owned entity organized on the basic principles of Co operative for distribution of electric power to its members and operates on No Loss No Profit basis for the mutual benefits of all its Members 1 3 Vision Electricity for all by 2020 1 4 Mission Quality and uninterruptable power supply 1 5 REB Profile Rural electrification Board a public service company Its Head Office is Rural electrification Board Nikunja 2 Khilkhet Dhaka 1229 Page 3 1 6 Objective The Rural Electrification Association at the programs agricultural industrial and economic social development of the role of the state of being To achieve food self sufficiency through the modern irrigation systems and other large and small cottage industries and a wide education health and information technology development as well as the leading role in the all Districts of Bangladesh Rural Electrification Program of the leading role in the development of quality of In order to obtain the broad objectives I h

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