PRESENTATION ON Save The Environment :

Welcome to my Presentation

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PRESENTATION ON : Operation of 33/11 KV Substation at Comilla Palli Bidyut Samity-1

Presented byKamal Ahmed

Department of Electrical and Electronics EngineeringID # 12205003

IUBAT-International University of Business Agriculture and Technology 2

CONTENTS

INTRODUCTIONOBJECTIVE ORGANIZATIONAL OVERVIEWSYSTEM CRITERIA OF CPBS-1BASIC ELECTRICAL SYSTEMDISTRIBUTION SYSTEMSUBSTATIONTRANSFORMER POWER TRANSFORMERDISTRIBUTION TRANSFORMERINSTRUMENTAL TRANSFORMER3

CONT..

ISOLATORINSULATORFUSECIRCUIT BREAKERRELAYLIGHTNING ARRESTERBUS BARPOWER FACTORVOLTAGE REGULATORRECOMMENDATIONCONCLUSION

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INTRODUCTIONElectricity is very essential for the development of a nation. The dependence on electricity is so much that it has become a part and parcel of our life. The power sector in Bangladesh faced numerous problems characterized by lack of supply capacity, frequent power cuts, unacceptable quality of power supply, and poor financial & operational performance of the sector entities. Lack of good governance along with poor procurement management is considered to be the root cause of these problems.

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6 OBJECTIVE

Theoretical knowledge.Collecting Knowledge regarding Power & Distribution system of CPBS-1.Study about Substation.Test and check the equipments of Substation.Identifying different types of problem which arise for operating this Substation.Suggest probable solution of the identified problem.

Organizational OverviewBackground - Comilla Palli Bidyut Samity-1 is a part of REB started its activities on 12-01-1981 in Dhaka. Vision- To provide quality and uninterrupted electricity to vast majority of Rural Bangladesh for their personal, social and economic developmentMission- Quality and uninterruptable power supply.Goal- The goal is Comilla Palli Bidyut Samity-1 to reach the electricity in every home in 2020.

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System Criteria of CPBS-1 The average system will serve 30,000 to 75,000 consumers with an average of 750Km of distribution line.The nominal sub-transmission voltages are 33,000 volts Nominal voltage for primary distribution is 11000 volts. The system frequency is 50HZ Medium voltage side solidly grounded 4 to 6 three phase feeders will distribute power from the substation for distance of some 10 to 12 km with single phase branch or tap lines taking off from the three phase line as required to serve single phase consumers.8

Basic Electrical system

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Distribution system

Electricity can be distributed by two ways.Overhead distribution &Underground distribution 10

Overhead distribution

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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.

12Fig:33/11KV Sub-Station

Transformer A transformer is an electrical device that transfers energy from one circuit to another by electromagnetic induction without any moving parts. Transformers are used to convert high voltage to low voltage or low voltage to high voltage.13

Basic Function of Transformer

Transformer is an electrical device that ..

Transfer electric power from one circuit to anotherIt does so without a change of frequencyIt accomplishes this by electromagnetic induction14

Common Types of Transformer Power Transformer Generally used in transmission network

Its rating is given in terms of the secondary's maximum voltage and current-delivering capacity

Operates at high voltagegreater than 33 KV with 100% efficiency

Has a big size

Used in generating station, transmission & distribution substation at high insulation level.

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Power Transformer 33/11KVSpecification of Three Phase Power Transformer

Transformer Type OUT DOORType of Cooling ONAN/ONAFRated MVA 5/6.25Rated KV HV 33 LV 11Rated Line Current HV 87.5/109.3 LV 270.5/332.6No of Phase 3Standard Frequency 50Hz

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Fig : 3-Phase Power Transformer

Common Types of TransformerDistribution Transformer

Used for the distribution of electrical energy

Operates at low voltage as less than 33KV in industrial purpose and 440v-220v in domestic purpose

It works at low efficiency at 50-70%

Has small size easy in installation

Has low magnetic losses & it is not always fully loaded.

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Figure : Distribution Transformer

Specification of Three Phase Distribution Transformer

Type of Cooling ONAN/ONAFRated KVA 2500Phase 3Rated Voltage HV 11 KV LV 0.415KVRated Current HV 131.2A LV 3478.01AFrequency 50Hz

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Figure :3-Phase Distribution Transformer

Specification of Distribution Transformer

Type Wound CorePhase 1Rated Voltage HV 6350V LV 240VRated Current HV 11.81A LV 312.5AFrequency 50HTotal Weight 450Kg

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Fig :1 Phase Distribution Transformer

Common Types of TransformerInstrument Transformers

1. Current Transformer (C.T)

Current transformer is used for stepping down AC current from higher value to lower value for measurement/protection.Current transformer is two types.Indoor type andOutdoor type.

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Fig : Current Transformer

Type of Core

Normally current transformer is provided with multi core. Cores are divided into two categories: Protective Measuring.Protection core of current transformer is used for over current protection, earth fault protection, differential protection etc. Measuring core of current transformer is used to supply current to measuring instruments like ammeters, watt-meters, KVA meters, KWh meters etc.

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Application of Current TransformerDirect measurement of current in high voltage system is not possible because of insulation problem of measuring instruments.Its is also not possible to use current flowing through the system directly for protection purpose due to its high value and high insulation problem.

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Use of Current Transformer

AC power supplies of appliances.In ground fault circuit interrupter. Circuit breakers.AC power supply grids.

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Fig : Sub Station

Common Types of TransformerInstrument Transformers

2.Potential TransformerPotential transformers are used to step-down highs system voltage low standard value accurately in proportion to their ratio.Potential Transformer is two types.Indoor type andOutdoor type.

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Fig: PT

Application of Potential TransformerDirect measurement of voltage in high voltage system is not possible because of insulation problem of measuring instruments. It is also not possible to use directly voltage for the system protection purpose due to its high value and high insulation problem of protection relays.

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Use of Potential Transformer (PT)Potential transformers are used in the AC power supplies of appliances, In ground fault circuit interrupter. Circuit breakers. AC power supply grids.

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Isolator

Isolator is a disconnecting switch, which operate under no load condition. It has no any specified current breaking capacity or current making capacity.

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Fig: Isolator

InsulatorThe overhead line conductors should be supported on the poles or towers. Insulators are those substance which do not can flow current from conductor to earth supports. The most commonly used material for the manufacture of insulator is porcelain.

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Fig: Insulator

Insulator TypesIn PBS system 5 types of insulator are used.Pin type insulatorSuspension type insulatorStrain insulatorShackle insulator &Stay insulator

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Pin type insulator :

Pin type insulators are used for transmission and distribution of electric power voltage up to 33KV

Suspension type insulator: For high voltage like as 33KV transmission line, Suspension type insulators used.

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Fig: Pin type insulators

Fig:Suspension type insulator

Strain insulator Dead end of the line or the corner or the sharp curve, the line is subjected to greater tension

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Fig: Strain insulator

Shackle insulator

It 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.

For low voltage lines, the stays are to be insulated from ground at a height not less than 13 meters from ground.

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Stay insulator

Fig: Shackle insulator

Fig: Stay insulator

FUSE

A fuse is a short pitch of metal, inserted in the circuit, which melts when excessive current flows thought it for sufficient time. It is inserted in series with the circuit to be protected.

Fig: Fuse33

Circuit Breaker34A circuit breaker is an electrical equipment which can open or close a circuit under all conditions such as no load, full load and fault conditions. It can be operated manually under normal conditions and automatically under fault conditions.

Operation of circuit breakerCircuit breaker consist of fixed and moving contactUnder normal condition these contact remain close .When fault occurs the secondary current of C.T will increase and the trip coil get energizedthe moving contact is pulled apart by relay mechanism, thus opening the circuit.

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Figure : Mechanism of Circuit Breaker

PBS Used circuit breakerIn PBS system 2 types of circuit breaker are used.Automatic Circuit Recloser (ACR) &Oil circuit Recloser (OCR)

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Auto Circuit Recloser

ACR :Operated by control panelSF6 is being used for insulationVacuum interrupter is being used for extinguishing the arcTwo coil is being used closing coil and trip coil

37 Fig : ACR

Oil circuit Recloser

OCR :Operated manually by fiber stickTransformer oil is being used for insulationOil interrupter is being used for arc interruptionFive coil of three types is being used like series trip coil (3),ground trip coil, closing coilCkt will trip at least double of rated current

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Fig : OCR

RelayA protective relay is an automatic device that detects the fault and initiates the operation of the circuit breaker to isolate the defective element from the rest of the system.

The Relays detect the abnormal conditions in the electrical circuits by constantly measuring the electrical quantities which are different under normal and fault conditions.

After detecting the abnormal conditions, it close the trip circuit in order to disconnect the faulty part from healthy part.

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Operation of Relay

Primary winding of C.T is connected in series with the line Secondary winding of C.T is connected with relay coil.Trip coil and relay coil is connected with supply. If fault occur, heavy Current flow through the relay coil. Causing the relay to operate by closing its contact.

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Figure 31: Relay Operation

Lightning arresterA lightning arrester is a protective device which conducts the high voltage surges on the power system to the ground.A lightning arrester is used on electrical power system to protect the insulation on the system from the damaging effect of lightning.

Fig: Lighting arrester

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Bus barWhen a number of lines operating at the same voltage have to be directly connected electrically.

Bus-bars are copper rods and operated at constant voltage. The incoming and outgoing lines in a substation are connected to the bus bars.

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Fig: Arrangement of bus bar

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Main and Transfer bus arrangement

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CB

CB

CB

CB

CB

CB

Transformer

CB

Main bus barTransfer bus barCB

Bus coupler

POWER FACTOR

The cosine of angle between voltage and current in an AC circuit is known as power factor.In AC circuits, the power factor is the ratio of the real power that is used to do work in the circuit and the apparent power that is supplied to the circuit.The power factor can get values in the range from 0 to 1.

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Importance of Power FactorLower utility fees by :Reducing peak KW billing demandEliminating the power factor penaltyIncrease the system capacity and reduce the system losses in electrical system.Increase the voltage level in electrical system.

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Methods of Power Factor Improvement Static capacitor.Synchronous condenser &Phase advancers.

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Static CapacitorThe power factor can be improved by connecting capacitors in parallel with the equipment operating at lagging power factor. The 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 Figure48

Fig: Capacitor connected in Delta or Star

Figure: Capacitor Bank use for power factor improvement

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Automatic Voltage RegulatorA voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level.Voltage regulators operate by comparing the actual output voltage to some internal fixed reference voltage.

Specification of Automatic Voltage RegulatorPhase Number 1Type of Cooling ONANRated Power 416.5KVARated Voltage 6350 VRated Current 656AVoltage Regulation 10Frequency 50 Hz

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Fig: Voltage Regulator

Single Line Diagram of Distribution Substation

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Fig: Single Line Diagram

Rating of Distribution Substation There are three Transformer T1, T2 & T3 EachTransformer are same rating 10 MVA

Current: Primary Current - 175A Secondary Current - 575A

Voltage: Primary Voltage - 33KV Secondary Voltage - 11KV

This Substation Total Rating is 30 MVA.

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Recommendation According to system design, the ratio of HT line and LT line must be 70:30 in PBS system. The load of rearrangement of substation feeder must be done properly. But they do not follow it. They use manually based equipment, if they use PLC based equipment then the system will be easier.Need to change wooden poles and cross arms. 53

Conclusion Electricity is the basic necessity for the economic development of a country. The industrial development and living standard of the people are directly related to the more use of electricity. Without electricity it is impossible to industrialize and irrigation as agro based country.

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: Thank You 56