pf project report

Project Report May 19, 2008

Chapter 1OVERVIEW

1.1 Introduction to Power System

1.2 CET and CESCO

1.3 Loads in CET

1.1 Introduction to Power System

Power Factor Correction Of CET Page 1


lectrical power is a little bit like the air one breathe. One doesn't really think about it until it is missing. Power is just "there," meeting ones daily needs, constantly. It is only during a power failure, when one walks into

a dark room and instinctively hits the useless light switch, that one realizes how important power is in our daily life. Without it, life can get somewhat cumbersome.

EElectric Energy is the most popular form of energy, because it can be

transported easily at high efficiency and reasonable cost. The power system of today is a complex interconnected network as shown in fig. 1.

A Power System can be subdivided into four major parts: 1) Generation. 2) Transmission and Sub transmission. 3) Distribution. 4) Loads.

Power is generated at generating stations, usually located away from the actual users. The generated voltage is then stepped up to a higher voltage for transmission, as transmission losses are lower at higher voltages. The transmitted electric power is then stepped down at grid stations

The modern distribution system begins as the primary circuit, leaves the sub-station and ends as the secondary service enters the customer's meter


FIGURE 1

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socket. First, the energy leaves the sub-station in a primary circuit, usually with all three phases.

The most common type of primary is known as a wye configuration (so named because of the shape of a "Y".) The wye configuration includes 3 phases (represented by the three outer parts of the "Y") and a neutral (represented by the center of the "Y".) The neutral is grounded both at the substation and at every power pole. The primary and secondary (low voltage) neutrals are bonded (connected) together to provide a path to blow the primary fuse if any fault occurs that allows primary voltage to enter the secondary lines. An example of this type of fault would be a primary phase falling across the secondary lines. Another example would be some type of fault in the transformer itself.

The other type of primary configuration is known as delta. This method is older and less common. Delta is so named because of the shape of the Greek letter delta, a triangle. Delta has only 3 phases and no neutral. In delta there is only a single voltage, between two phases (phase to phase), while in wye there are two voltages, between two phases and between a phase and neutral (phase to neutral). Wye primary is safer because if one phase becomes grounded, that is, makes connection to the ground through a person, tree, or other object, it should trip out the fused cutout similar to a household circuit breaker tripping. In delta, if a phase makes connection to ground it will continue to function normally. It takes two or three phases to make connection to ground before the fused cutouts will open the circuit. The voltage for this configuration is usually 4800 volts.

Transformers are sometimes used to step down from 7200 or 7600 volts to 4800 volts or to step up from 4800 volts to 7200 or 7600 volts. When the voltage is stepped up, a neutral is created by bonding one leg of the 7200/7600 side to ground. This is commonly used to power single phase underground services or whole housing developments that are built in 4800 volt delta distribution areas. Step downs are used in areas that have been upgraded to a 7200/12500Y or 7600/13200Y and the power company chooses to leave a section as a 4800 volt setup. Sometimes power companies choose to leave sections of a distribution grid as 4800 volts because this setup is less likely to trip fuses or reclosers in heavily wooded areas where trees come into contact with lines.

For power to be useful in a home or business, it comes off the transmission grid and is stepped-down to the distribution grid. This may



happen in several phases. The place where the conversion from "transmission" to "distribution" occurs is in a power substation. A power substation typically does two or three things:

It has transformers that step transmission voltages (in the tens or hundreds of thousands of volts range) down to distribution voltages (typically less than 10,000 volts).

It has a "bus" that can split the distribution power off in multiple directions.

It often has circuit breakers and switches so that the substation can be disconnected from the transmission grid or separate distribution lines can be disconnected from the substation when necessary.

It often has circuit breakers and switches so that the substation can be disconnected from the transmission grid or separate distribution lines can be disconnected from the substation when necessary. The primary distribution lines are usually in the range of 4 to 34.5 KV and supply load in well defined geographical area. Some small industrial customers are served directly by the primary feeders.

1.2 CET and CESCO

The Central Electricity Supply Company Of Orissa Limited (CESCO) is responsible for power supply and distribution to College of Engineering and Technology (CET), Bhubaneswar. CESCO was incorporated on 19-11-1997 under the companies Act, 1956 as a Public Limited Company. Though the Company received the certificate for commencement of business on 30-12-1997, it started functioning separately with effect from 26-11-1998, under the license of GRIDCO, after notification by the Govt. of Orissa in the official gazette. CESCO received the Distribution and retail supply license from Orissa Electricity Regulatory Commission(OERC) to distribute and make retail supply of electricity in the Central Zone consisting of undivided Cuttack, Puri and Dhenkanal district with effect from 01-04-1999 and started functioning under own license from 01-04-1999.

College of Engineering and Technology (CET), Bhubaneswar gets its power supply through three 3-Φ distribution transformers of following specifications:1. TRANSFORMER 1 (Office Block)



KVA rating: 250 KVA Volts : HV 11000 V (no load) LV 433 V Ampere : HV 13.12 A LV 333.35 A Frequency: 50 Hz % Volt Impedance: 4.6 Type of Vector Group: DY11

2. TRANSFORMER 2 (Academic Block) KVA rating: 250 KVA Volts : HV 11000 V (no load) LV 433 V Ampere : HV 13.12 A LV 333.35 A Frequency: 50 Hz % Volt Impedance: 4.6 Type of Vector Group: DY11

3. TRANSFORMER 3 (Workshop & Laboratory) KVA rating: 100 KVA Volts : HV 11000 V (no load) LV 433 V Ampere : HV 5.25 A LV 133.33 A Frequency: 50 Hz % Volt Impedance: 4.5 Type of Vector Group: DY11

Loads of power systems are divided into industrial, commercial, and residential. Very large loads may be served from the transmission system. Large industrial loads are served from the sub transmission network. Industrial loads are composite loads, and induction motors form a high proportion of these loads. These composite loads are function of voltage and frequency. Commercial and residential load consist largely of lighting, heating and cooling. These loads are independent of frequency and consume negligibly small reactive power.

The various loads of CET come under the category of commercial loads having a load factor of 50% and an average duty cycle of 8 hrs a day. The loads


FIGURE 2


are generally ceiling fans, fluorescent lamps, Computers, air conditioners and other small loads.

1.3 Loads in CET

he transformer 1 (Office Block) 250 KVA supplies power to the library, administrative office, Syndicate bank, Mechanical engineering department, Computer science and engineering department and other classrooms. The loads connected are

given in the following table:T

ROOM NO.

LOAD TYPENO. OF LOAD

RATING(W) TOTAL(W)

101 Ceiling Fan(60watt) 12 720Fluorescent Lamp(40W) 21 840Air conditioner(1000w) 8 8000

Computer(120W) 1 120Xerox machine(1280) 1 1280 10960

102 Ceiling Fan(60watt) 10 600Fluorescent Lamp(40W) 16 640 1240

103 Ceiling Fan(60watt) 7 420Fluorescent Lamp(40W) 13 520Air conditioner(1000w) 4 4000 4940

104 Ceiling Fan(60watt) 2 120Fluorescent Lamp(40W) 4 160

Computer(120W) 1 120 400105 Ceiling Fan(60watt) 8 480

Fluorescent Lamp(40W) 16 640 1120106 Ceiling Fan(60watt) 6 360

Fluorescent Lamp(40W) 9 360 720Syndicate

bankCeiling Fan(60watt) 2 120

Fluorescent Lamp(40W) 2 80Computer(120W) 5 600 800

109 Ceiling Fan(60watt) 2 120C. Fluorescent Lamp(40W) 3 120

Computer(120W) 1 120Air conditioner(1000w) 1 1000

Fax machine (150) 1 150 1510111 Ceiling Fan(60watt) 2 120

C. Fluorescent Lamp(40W) 3 120Computer(120W) 1 120

Air conditioner(1000w) 1 1000Fax machine (150) 1 150 1510



Fax machine (150) 1 150 1510





Fax machine (150) 1 150 1510114 Ceiling Fan(60watt) 3 180

C. Fluorescent Lamp(40W) 8 320 500115 Ceiling Fan(60watt) 6 360

C. Fluorescent Lamp(40W) 6 240 600116A Ceiling Fan(60watt) 9 540

Fluorescent Lamp(40W) 18 720 1260116B Ceiling Fan(60watt) 7 420

Fluorescent Lamp(40W) 11 440 860117 Ceiling Fan(60watt) 9 540

Fluorescent Lamp(40W) 18 720 1260118 C. Fluorescent Lamp(40W) 10 400

Computer(120W) 15 3000Air conditioner(1000w) 4 4000 7400

119 Fluorescent Lamp(40W) 2 80Pedestal fan(60watt) 6 360

Air conditioner(1000w) 9 9000C. Fluorescent Lamp(40W) 17 680

Projector(200) 1 200 9960120 Ceiling Fan(60watt) 10 600

Fluorescent Lamp(40W) 11 440 1040201 Air conditioner(1000w) 19 19000

C. Fluorescent Lamp(40W) 36 1440Ceiling Fan(60watt) 33 1980Computer(120W) 3 360

Projector(200) 1 200Xerox machine(1280) 2 2560 25540

203 Ceiling Fan(60watt) 12 720Fluorescent Lamp(40W) 12 480Air conditioner(1000w) 4 4000 5200

English Lab

Ceiling Fan(60watt) 6 360

Fluorescent Lamp(40W) 6 240Air conditioner(1000w) 2 2000

Computer(120W) 1 120 2360205 Ceiling Fan(60watt) 6 360










C. Fluorescent Lamp(40W) 6 240 2640Computer

LabCeiling Fan(60watt) 21 1260


C. Fluorescent Lamp(40W) 27 1080 33380Corridor Fluorescent Lamp(40W) 17 680 680

Toilet Fluorescent Lamp(40W) 8 320Incandescent Lamp(100W) 8 800

Exhaust Fan(60W) 4 240Aqua guard (650W) 1 650 2010

The transformer 2 (Academic Block) 250 KVA supplies power to the Electrical department, Chemistry and Physics Department, Instrumentation and Electronics and Information Technology Departments and various other classrooms. The loads connected are given in the following table:

ROOM NO LOAD TYPENO. OF LOAD

RATING(W) TOTAL W)

217 Ceiling Fan(60watt) 6 360C. Fluorescent Lamp(40W) 8 320 680






Computer(120W) 3 360Printer(60W) 3 180 2000


corridor Incandescent Lamp(100W) 4 400 400Electronics

Lab.Ceiling Fan(60watt) 9 540

C. Fluorescent Lamp(40W) 18 720Computer(120W) 2 240

Socket(200w) 14 2800 3760Exam Fluorescent Lamp(40W) 8 320



Dept.Ceiling Fan(60watt) 5 300Computer(120W) 2 240

Air conditioner(1000w) 2 2000Xerox Machine(1280) 2 2560

Printer(60W) 2 120 5540138 Ceiling Fan(60watt) 11 660

Fluorescent Lamp(40W) 16 640 1300Socket


136 A Ceiling Fan(60watt) 6 360Fluorescent Lamp(40W) 12 480 840

136 B Ceiling Fan(60watt) 7 420Fluorescent Lamp(40W) 10 400 820





µp Lab. Ceiling Fan(60watt) 8 480Fluorescent Lamp(40W) 12 480


Socket(200w) 12 2400 10360Toilet Fluorescent Lamp(40W) 8 320

Incandescent Lamp(100W) 8 800Exhaust Fan(60W) 4 240 1360

Corridor Incandescent Lamp(100W) 6 600 600131 Ceiling Fan(60watt) 2 120

Fluorescent Lamp(40W) 4 160Computer(120W) 6 720 1000

129 Ceiling Fan(60watt) 1 60Fluorescent Lamp(40W) 2 80Air conditioner(1000w) 1 1000



Computer(120W) 1 120Printer(60W) 1 60

Air conditioner(1000w) 1 1000 1400132 Ceiling Fan(60watt) 1 60

Fluorescent Lamp(40W) 4 160Computer(120W) 1 120



Printer(60W) 1 60Air conditioner(1000w) 1 1000 1400


Computer(120W) 2 240Printer(60W) 2 120

Air conditioner(1000w) 1 1000Refrigerator (1000W) 1 1000 2660







123 B Ceiling Fan(60watt) 6 360Fluorescent Lamp(40W) 12 480 840

123 A Ceiling Fan(60watt) 8 480Fluorescent Lamp(40W) 16 640 1120




Exhaust Fan(60W) 4 240 1360Corridor Incandescent Lamp(100W) 6 600 600












Corridor Incandescent Lamp(100W) 6 600 600

The transformer 3 (Workshop and Laboratory) 100 KVA supplies power to the Workshop and Labs. of various departments. The loads connected are given in the following table:

ROOM NO. LOAD TYPENO. OF LOAD

RATING(W)

TOTAL W)

BsnlTower Air conditioner(1500w) 2 3000Fluorescent Lamp(40W) 2 80

Socket (1000W) 2 2000Socket(200W) 5 1000 6080

Electrical lab 1


Fluorescent Lamp(40W) 12 480Power socket(1000W) 10 10000

Socket(200W) 4 800 11760Electrical

lab 2Ceiling Fan(60watt) 7 420


Socket(200W) 18 360 9140Civil lab 1 Ceiling Fan(60watt) 5 300


Socket(200W) 5 10000 16780Civil lab 2 Ceiling Fan(60watt) 4 240


Socket(200W) 8 1600 8240Mechanical

lab 1Ceiling Fan(60watt) 4 140

Fluorescent Lamp(40W) 12 480Socket (200) 6 1200 1820

Mechanical lab 2



Mechanical lab 3



Mechanical lab 4


Fluorescent Lamp(40W) 10 400Socket (200W) 6 1200

Refrigerator (1000W) 1 1000



Computer (120W) 2 240 3080Corridor Fluorescent Lamp(40W) 12 480 480


Exhaust Fan(60W) 4 240Aqua guard (650W) 1 650 1450

Street light Mercury light(250W) 40 10000 10000



Chapter 2POWER FACTOR

2.1 Real, Reactive & Apparent Power

2.2 Definition of Power Factor

2.3 What is Power Factor?

2.4 Measurement of Power Factor

2.5 Causes of low Power Factor

2.6 Disadvantages of low Power Factor

2.7 Present Scenario in CET



2.1 Real, Reactive & Apparent Powereactive loads such as inductors and capacitors dissipate zero power, yet the fact that they drop voltage and draw current gives the deceptive impression that they actually do dissipate power. This “phantom

power” is called reactive power, and it is measured in a unit called Volt-Amps-Reactive (VAR), rather than watts. The mathematical symbol for reactive power is (unfortunately) the capital letter Q. The actual amount of power being used, or dissipated, in a circuit is called true power, and it is measured in watts (symbolized by the capital letter P, as always). The combination of reactive power and true power is called apparent power, and it is the product of a circuit's voltage and current, without reference to phase angle. Apparent power is measured in the unit of Volt-Amps (VA) and is symbolized by the capital letter S.

R

As a rule, true power is a function of a circuit's dissipative elements, usually resistances (R). Reactive power is a function of a circuit's reactance (X). Apparent power is a function of a circuit's total impedance (Z). Since we're dealing with scalar quantities for power calculation, any complex starting quantities such as voltage, current, and impedance must be represented by their polar magnitudes, not by real or imaginary rectangular components. There are several power equations relating the three types of power to resistance, reactance, and impedance (all using scalar quantities):



These three types of power -- true, reactive, and apparent -- relate to one another in trigonometric form. We call this the power triangle:

2.2 Definition Of Power Factorhe power factor of an AC electric power system is defined as the ratio of the real power to the apparent power, and is a number between 0 and 1 (frequently expressed as a percentage, e.g. 0.5 pf = 50% pf).TIf is the impedance phase angle between the current and voltage, then

the power factor is equal to cos , and:

Since the units are consistent, the power factor is by definition a dimensionless number between 0 and 1. When power factor is equal to 0, the energy flow is entirely reactive, and stored energy in the load returns to the source on each cycle. When the power factor is 1, all the energy supplied by the source is consumed by the load. Power factors are usually stated as "leading" or "lagging" to show the sign of the phase angle, where leading indicates a negative sign.

If a purely resistive load is connected to a power supply, current and voltage will change polarity in step, the power factor will be unity (1), and the


FIGURE 3


electrical energy flows in a single direction across the network in each cycle. Inductive loads such as transformers and motors (any type of wound coil) consume reactive power with current waveform lagging the voltage. Capacitive loads such as capacitor banks or buried cable generate reactive power with current phase leading the voltage. Both types of loads will absorb energy during part of the AC cycle, which is stored in the device's magnetic or electric field, only to return this energy back to the source during the rest of the cycle.

2.3 What is Power Factor?

o understand power factor, visualize a horse pulling a railroad car down a railroad track as shown in fig. 4. Because the railroad ties are uneven, the horse must pull the car from the side of the track. The horse is

pulling the railroad car at an angle to the direction of the car’s travel. The power required to move the car down the track is the working (real) power. The effort of the horse is the total (apparent) power. Because of the angle of the horse’s pull, not all of the horse’s effort is used to move the car down the track. The car will not move sideways; therefore, the sideways pull of the horse is wasted effort or nonworking (reactive) power.

T

The angle of the horse’s pull is related to power factor, which is defined as the ratio of real (working) power to apparent (total) power. If the horse is led closer to the center of the track, the angle of side pull decreases and the real power approaches the value of the apparent power. Therefore, the ratio


FIGURE 4


of real power to apparent power (the power factor) approaches 1. As the power factor approaches 1, the reactive (nonworking) power approaches 0.

2.4 Measurement of Power Factorower factor in a single-phase circuit (or balanced three-phase circuit) can be measured with the wattmeter-ammeter-voltmeter method, where the power in watts is divided by the product of measured voltage

and current. The power factor of a balanced polyphase circuit is the same as that of any phase. The power factor of an unbalanced polyphase circuit is not uniquely defined.

P

A direct reading power factor meter can be made with a moving coil meter of the electrodynamic type as shown in fig. 5, carrying two perpendicular coils on the moving part of the instrument. The field of the instrument is energized by the circuit current flow. The two moving coils, A and B, are connected in parallel with the circuit load. One coil, A, will be connected through a resistor and the second coil, B, through an inductor, so that the current in coil B is delayed with respect to current in A. At unity power factor, the current in A is in phase with the circuit current, and coil A provides maximum torque, driving the instrument pointer toward the 1.0 mark on the scale. At zero power factor, the current in coil B is in phase with circuit current, and coil B provides torque to drive the pointer towards 0. At intermediate values of power factor, the torque provided by the two coils adds and the pointer takes up intermediate positions.

Another electromechanical instrument is the polarized-vane type. In this instrument a stationary field coil produces a rotating magnetic field (connected either directly to polyphase voltage sources or to a phase-shifting reactor if a single-phase application). A second stationary field coil carries a current


FIGURE 5


proportional to current in the circuit. The moving system of the instrument consists of two vanes which are magnetized by the current coil. In operation the moving vanes take up a physical angle equivalent to the electrical angle between the voltage source and the current source. This type of instrument can be made to register for currents in both directions, giving a 4-quadrant display of power factor or phase angle.

Digital instruments can be made that either directly measure the time lag between voltage and current waveforms and so calculate the power factor, or by measuring both true and apparent power in the circuit and calculating the quotient. The first method is only accurate if voltage and current are sinusoidal; loads such as rectifiers distort the waveforms from the sinusoidal shape.

2.5 Cause of Low Power FactorThe various causes of low operating power factor are:

All AC motor and transformers operate at lagging power factor. The power factor falls with the decrease in load.

Arc lamps and electric discharge lamps operate at low lagging power factor.

Due to increased supply mains voltage, which usually occurs during low load periods such as lunch hours, night hour etc, the magnetizing current of inductive reactance increases and power factor of the electrical plant comes down as a whole.

Industrial heating furnace such as arc and induction furnaces operates on very lagging power factor.

The power factor at which motors operate falls due to improper maintenance and repairs of motors. In repaired motors, less wire is sometimes used than originally wound motors, therefore, in such motors leakage of magnetic flux increases and power factor of the motor decreases. Reactive power required by inductive loads increases the amount of apparent power (measured in kVA) in the distribution system. The increase in reactive and apparent power causes the power factor to decrease.

Fig. 6 shows the operating power factor of various devices.



2.6 Disadvantage of Low Power FactorFor load P to be supplied at terminal voltage V and at a power factor cos

Φ by a 3 Φ balanced system then load current is given by:I=P / (√3VcosΦ)

If V and P are constant the load current I is inversely proportional to power factor i.e. lower the power factor higher is the current and vice versa. The higher current due to poor power factor affects the system and results in the following disadvantages:

Rating of generators and transformer are proportional to their output current, hence inversely proportional to power factor. Therefore they have to supply the same load at lower power factor thus leading to de rating of the device.

Cross sectional area of the bus bar and the contact surface of switch gear are required to be enlarged for the same power to be delivered but at low power factor.

For same power to be transmitted at low power factor current is high hence conductor size has to be increased for same current density.

Energy loss is directly proportional to square of the current; hence more loss occurs at low power factor.

Low lagging power factor results in large voltage drop in generators, transformers, transmission lines and distributors which results in poor regulation.

Low lagging power factor results in reduced handling capacity of all elements of the system.


FIGURE 6


The significance of power factor lies in the fact that utility companies supply customers with volt-amperes, but bill them for watts. Power factors below 1.0 require a utility to generate more than the minimum volt-amperes necessary to supply the real power (watts). This increases generation and transmission costs. For example, if the load power factor were as low as 0.7, the apparent power would be 1.4 times the real power used by the load. Line current in the circuit would also be 1.4 times the current required at 1.0 power factor, so the losses in the circuit would be doubled (since they are proportional to the square of the current). Alternatively all components of the system such as generators, conductors, transformers, and switchgear would be increased in size (and cost) to carry the extra current.

Utilities typically charge additional costs to customers who have a power factor below some limit, which is typically 0.9 to 0.95. Engineers are often interested in the power factor of a load as one of the factors that affect the efficiency of power transmission.

2.7 Present Scenario in CEThe present scenario of power consumption in CET for the electricity bill of month 01/12/2007-31/12/2007 issued by The Central Electricity Supply Company Of Orissa Limited (CESCO) is as follows:T

Consumption type: commercialMetering: HVMaximum Contract Demand: 200 KWTransformer KVA: 250 KVASupply Volt KV: 11 KVLoad Factor: 50%Required power factor: 90%Actual power factor: 77%Fall in power factor: 13%

Three meters have been installed for measuring the KWH, KVAH, KVARH readings respectively.

METER Last Reading Curr. Reading Mul. Factor Net Reading

KWH 5408.79 5460.61 600 31092.00KVAH 7648.41 7715.50 600 40254.00



KVARH 5104.14 5146.19 600 25230.00

RENT CHARGES: RUPEESA: KWH charge for 31092 units @3.00x31092 93276.00B: Demand Charge for 200KW @Rs 50/KW 10000.00C: low voltage surcharge @0.0% of A+B 0.00D: P.F incentive@ 0.5% for rise above 95% 0.00E: Penalty on A+B for 13% fall in P.F 6712.94F: Electricity Charge A+B+C-D+E 109988.95G: Delayed payment Surcharge 11.95H: Meter Rent 0.00I: Customer Charge 250.00J: Reconnection Charge 0.00K: Miscellaneous Charge H+I+J 250.00

Thus our college CET is paying a penalty of Rs 6712.95 for low power factor of 13%. This low power factor is to be improved.



Chapter 3IMPROVEMENT OF POWER FACTOR

3.1 Introduction

3.2 Methods of Improving Power Factor

3.3 Low Tension Power Capacitors

3.4 Automatic Capacitor Switch

3.5 The Capacitor Unit And Bank Configurations

3.6 Location Of Capacitor banks

3.7 Capacitor Bank Protection

3.8 Harmonics Flow In Electrical systems



3.1 Introduction

hunt capacitor banks are used to improve the quality of the electrical supply and the efficient operation of the power system. Studies show that a flat voltage profile on the system can significantly reduce line

losses. Shunt capacitor banks are relatively inexpensive and can be easily installed anywhere on the network.

SThis chapter reviews principles of shunt capacitor bank design for pole

mounted substation installation and basic protection techniques along with special circuit design for harmonic suppression filers. The protection of shunt capacitor bank includes:

a) Protection against internal bank faults and faults that occur inside the capacitor unit.

b) Protection of the bank against system disturbances.

3.2 Methods for improving Power factor

The power factor can be improved by implementing various methods 1. Static VAR compensation 2. Synchronous condenser 3. Phase advancer

But in commercial buildings or non industrial consumers generally adopt the process of static VAR compensation. Static VAR compensation method is nothing but the usage of static devices like capacitor banks in parallel with the equipment operating at lagging power factor such as induction motors, fluorescent tubes etc. Static capacitors have the advantage of

Small losses or higher efficiency (about 99.6%), Low initial cost, Little maintenance owing to the absence of rotating parts Easy installation being lighter in weight and Capability to operate under ordinary atmospheric condition.

The main disadvantage of SCB is that its reactive power output is proportional to the square of the voltage and consequently when the voltage is low and the system needs them most, they are the least efficient.



3.3 Low Tension Power Capacitors

These are available in wide range such as mixed dielectric (MD), metalized poly propylene (MPP) and film foil (FF) type capacitors are manufactured using the latest automated production technologies under strict quality control and in controlled environmental conditions, for a variety of applications. Their design adds a touch of elegance ton electrical equipments.

ADVANTAGES OF USING LT POWER CAPACITORS: Reduced power costs due to reduction in KVA demand. Elimination of power factor penalties. Gain in system capacity due to reduction in total current drawn from the

mains. Reduction in power losses, increase in efficiency of the system and

consequent reduction in electricity bills. Reduction in voltage drop and improved voltage regulation. Engineered solutions using detuned LT power capacitors can reduce

harmonic distortion and risks of harmonic overloads thus enhancing overall performance and reliability of induction motors, transformers and other electrical installations.

FLEXI-BANK KIT:Flexi bank, our latest user friendly innovation, helps to form a capacitor

bank at site in less than an hour. Flexi bank kits comprise the following accessories:

Mounting frame Cable termination enclosure

ADVANTAGES OF FLEXI-BANK KIT: Wide range of bank output in KVAR. Easy maintenance. Easy cable termination of aluminum or copper supply cables. Easy electrical checking of individual units in the bank even when bank is

energized. Minimizes time required to procure and install capacitor banks. Better electrical availability of capacitor banks. Possibility of upgrading KVAR output.



METALLISED POLYPROPELENE DIELECTRIC, SELF-HEALING TYPE CAPACITOR (M.P.P):

This is low-loss dielectric. This means that the capacitor runs cool, normally only about 1 degree centigrade above ambient temperature .The wattage dissipated, would typically be about less than 0.5 W/KVAR compared with 5 W/KVAR for an equivalent conventional impregnated paper capacitor. This offers substantial energy saving in large stations.

SELF HEALING:The capacitor electrodes of a metalized polypropylene film capacitor

consist of thin layers of metal deposited on to the polypropylene under high vacuum .An isolated dielectric breakdown within the capacitor winding is repaired by vaporization on the metal deposit around the fault area. The capacitor remains unchanged except for an insignificant capacitance loss. A capacitor with self healing characteristics is unlikely to fail in short circuit under normal working conditions.

FOR HEAVY DUTY APPLICATIONS, DOUBLE DIELECTRIC CAPACITORS:These meet the demands of heavy duty industrial loads. These loads are

rectifiers, induction furnaces large rolling mills etc. the basic reason which makes these loads arduous in nature is that, each load gives rise to high over current or high over voltage in an irregular manner. Rectifier load or arc furnace generates harmonic voltages which would impose continuous and severe over current on capacitor. In order to build up the correct degree of protection, a capacitor needs to be given a higher over current and also higher surge voltage withstands capacity. This dual consideration has been taken into account to evolve a different construction of capacitors. The basic cell winding of this M.P.P. design remains the same as that for a conventional design. This design of the capacitor has been evolved keeping in mind the basic simplicity of construction of primary M.P.P. cell and its superiority in the capital and operating costs. The new design retains all these features and still raised by about a factor of over current as also the surge voltage with stand capacity.

ALL POLY-PROPYLENE (A.P.P.):In this type one layer of plain polypropylene and one layer of aluminum

foil, generally oil filled under vacuum like conventional impregnated paper capacitor. Elements are made flat and pressure is given for making stack. In built fuse is given to each element



MIXED DIELECTRIC TYPE (M.D.):In this type dielectrics are one layer of paper one layer plain

polypropylene and aluminum foil. M.D. type also requires to impregnate stack and provided with fuse like A.P.P.


Some of the Salient Features of the Automatic Capacitor Switch are: Current control to be adjusted to minimum 5 amperes with

respect to primary load current at .4 KV. Two pointers are to be set at meter relay provided at the

control panel according to load power factor. Automatic/manual control. Better voltage regulation. No unusual voltage rise or drop due to load variation. Better reliability.

BENEFITS OF AUTOMATIC CAPACITOR SWITCH: Extra KVA is pumped into the system so capital investment for

this equivalent KVA is conserved. Conservation of energy. Line loss minimum. Efficiency of distribution. Less maintenance/manpower/light-weight. Easy to mount at the existing pole without incurring any

substantial expenditure. Ideal for unmanned.

APPLICATION: To compensate reactive components due to variable load. To achieve conservation of energy.



COMPARISON BETWEEN LT SWITCHED AND FIXED TYPE CAPACITOR CONTROL:

Automatic Capacitor Switch Fixed Type Capacitor Control 1. Suitable for variable load. 1. Suitable for fixed load.

2. Automatic Switching and smooth control on powerfactor for variable load can be achieved.

2. Automatic Switching not possible as it is suitable for fixed load.

3. Suitable for pole mounted type on existing structure without involving any additional civil cost etc.

3. Only substation mounting type and involving the additional civil construction.

4. SF-6 Gas filled AutomaticSwitch is used and almostmaintenance free.

4. Maintenance cost substantial.

5. Light Weight. 5. Heavy Weight.

6. Less down time. 6. More down time.

3.5 The Capacitor Unit And Bank Configurations

THE CAPACITOR UNIT:

The capacitor unit, Fig. 7 shown on next page, is the building block of a shunt capacitor bank. The capacitor unit is made up of individual capacitor elements, arranged in parallel/ series connected groups, within a steel enclosure. The internal discharge device is a resistor that reduces the unit residual voltage to 50V or less in 5 min. Capacitor units are available in a variety of voltage ratings (240 V to 24940 V) and sizes (2.5 KVAR to about 1000 KVAR).

CAPACITOR UNIT CAPABILITIES:



Relay protection of shunt capacitor banks requires some knowledge of the capabilities and limitations of the capacitor unit and associated electrical equipment including: individual capacitor unit, bank switching devices, fuses, voltage and current sensing devices. Capacitors are intended to be operated at or below their rated voltage and frequency as they are very sensitive to these values; the reactive power generated by a capacitor is proportional to both of them (KVAR=2f V2). The IEEE Standard 18-1992 and Standard 1036-1992 specify the standard ratings of the capacitors designed for shunt connection to ac systems and also provide application guidelines.

These standards stipulate that:1. Capacitor units should be capable of continuous operation up to 110% of rated terminal rms voltage and a crest voltage not exceeding 1.2 x √2 of rated rms voltage, including harmonics but excluding transients. The capacitor should also be able to carry 135% of nominal current.2. Capacitors units should not give less than 100% or more than 115% of rated reactive power at rated sinusoidal voltage and frequency.3. Capacitor units should be suitable for continuous operation at up to 135%of rated reactive power caused by the combined effects of:

Voltage in excess of the nameplate rating at fundamental frequency, but not over 110% of rated rms voltage.

Harmonic voltages superimposed on the fundamental frequency. Reactive power manufacturing tolerance of up to 115% of rated reactive

power.


FIGURE 7


BANK CONFIGURATION:

The use of fuses for protecting the capacitor units and it location (inside the capacitor unit on each element or outside the unit) is an important subject in the design of SCBs. They also affect the failure mode of the capacitor unit and influence the design of the bank protection. Depending on the application any of the following configurations are suitable for shunt capacitor banks:

(a) Externally fusedAn individual fuse, externally mounted between the capacitor unit and

the capacitor bank fuse bus, typically protects each capacitor unit. The capacitor unit can be designed for a relatively high voltage because the external fuse is capable of interrupting a high-voltage fault. Use of capacitors with the highest possible voltage rating will result in a capacitive bank with the fewest number of series groups.

A failure of a capacitor element welds the foils together and short circuits the other capacitor elements connected in parallel in the same group. The remaining capacitor elements in the unit remain in service with a higher voltage across them than before the failure and an increased in capacitor unit current. If a second element fails the process repeats itself resulting in an even higher voltage for the remaining elements. Successive failures within the same unit will make the fuse to operate, disconnecting the capacitor unit and indicating the failed one.

Externally fused SCBs are configured using one or more series groups of parallel-connected capacitor units per phase (Fig. 8). The available unbalance signal level decreases as the number of series groups of capacitors is increased or as the number of capacitor units in parallel per series group is increased. However, the KVAR rating of the individual capacitor unit may need to be smaller because a minimum number of parallel units are required to allow the bank to remain in service with one fuse or unit out.


FIGURE 8


(b) Internally fusedEach capacitor element is fused inside the capacitor unit. The fuse is a

simple piece of wire enough to limit the current and encapsulated in a wrapper able to withstand the heat produced by the arc. Upon a capacitor element failure, the fuse removes the affected element only. The other elements, connected in parallel in the same group, remain in service but with a slightly higher voltage across them. Fig. 9 illustrates a typical capacitor bank utilizing internally fused capacitor units. In general, banks employing internally fused capacitor units are configured with fewer capacitor units in parallel and more series groups of units than are used in banks employing externally fused

capacitor units. The capacitor units are normally large because a complete unit is not expected to fail.(c) Fuse less shunt capacitor banks

The capacitor units for fuse less capacitor banks are identical to those for externally fused described above. To form a bank, capacitor units are connected in series strings between phase and neutral, shown in Fig. 10. The protection is based on the capacitor elements (within the unit) failing in a shorted mode, short- circuiting the group. When the capacitor element fails it welds and the capacitor unit remains in service. The voltage across the failed capacitor element is then shared among all the remaining capacitor element groups in the series. For example, is there are 6 capacitor units in series and each unit has 8 element groups in series there is a total of 48 element groups


FIGURE 9


in series. If one capacitor element fails, the element is shortened and the voltage on the remaining elements is 48/47 or about a 2% increase in the voltage. The capacitor bank continues in service; however, successive failures of elements will lead to the removal of the bank. The fuse less design is not usually applied for system voltages less than about 34.5 kV. The reason is that there shall be more than 10 elements in series so that the bank does not have to be removed from service for the failure of one element because the voltage across the remaining elements would increase by a factor of about E (E – 1), where E is the number of elements in the string.

The discharge energy is small because no capacitor units are connected directly in parallel. Another advantage of fuse less banks is that the unbalance protection does not have to be delayed to coordinate with the fuses.

(d) Unfused shunt capacitor BanksContrary to the fuse less configuration, where the units are connected in

series, the unfused shunt capacitor bank uses a series/parallel connection of the capacitor units. The unfused approach would normally be used on banks below 34.5 kV, where series strings of capacitor units are not practical, or on higher voltage banks with modest parallel energy. This design does not require as many capacitor units in parallel as an externally fused bank.

3.6 Location Of Capacitor Banks

CENTRAL COMPENSATION: When the main purpose is to reduce reactive power purchase due to power suppliers tariffs, central compensation is preferable. Reactive loading conditions within a plant are not affected if compensation is made on the high voltage side. When made on the low voltage side, the transformer is relieved. Cost of installation on the high voltage and low voltage sides respectively determine where to install the capacitor.

GROUP COMPENSATION:


FIGURE 10


Group compensation is preferable to central compensation if sufficiently large capacitors can be utilized. In addition to what is obtained at central compensation, load on cables is reduced and losses decrease. Reduced losses often make group compensation more profitable than central compensation. Because of large available group compensation is suitable for harmonic filters.

INDIVIDUAL COMPENSATION: The advantage with individual compensation is that existing switching and protective devices for the machine to be compensated can also be utilized for switching and protection of capacitors. The costs are there by limited solely to purchasing the capacitors. Another advantage is gained by the capacitor being automatically switched in and out with the load. However this signifies that individual compensation is solely motivated for apparatus and machines which have a very good load factor.

Usually, in a long feeder, receiving end voltage bucks considerably due to drop and consumers at this is affected. Therefore, it is essential to install the switched capacitor nearer to the receiving end of the feeder where the load concentration is more. Subsequently, the improvement in power factor and voltage will be experienced by consumers who are connected after the tapping point of switched capacitor in the system. However prior to the installation of the switched capacitor at set location, the power factor, the peak demand and off peak demand load current should be noted carefully.

3.7 Capacitor Bank Protection

The protection of SCB’s involves: a) Protection of the bank against faults occurring within the bank

including those inside the capacitor unit.b) Protection of the bank against system disturbances and faults.

This paper only discusses relay based protection schemes that provide alarm to indicate an unbalance within the bank and initiate a shutdown of the bank in case of faults that may lead to catastrophic failures. It does not deal with the means and strategies to protect individual elements or capacitor units. The protection selected for a capacitor bank depends on bank configuration, whether or not the capacitor bank is grounded and the system grounding.



PROTECTION AGAINST INTERNAL BANK FAULTS:

a) Phase to Phase faults Usually individual phases of a SCB are built on separate structures where phase to phase faults are unlikely. However, consider an ungrounded single wye capacitor bank with two series groups per phase where all three phases are installed upon a single steel structure. A mid-rack fault between 2 phases as shown in Fig. 11 is possible and will go undetected. This fault does not cause an unbalance of the neutral voltage (or neutral current if grounded) as the healthy voltage is counter balance by the 2 other faulty phase voltages.The most efficient protection for mid-rack phase to phase faults is the negative sequence current. Tripping shall be delayed to coordinate with other relays in the system.

b) Faults on capacitor banks Time over current relays for phase and ground are required to provide protection for phase and ground faults on the connecting feeder (or bus work) between the bank bus and the first capacitor unit. Directional over current relays looking into the bank are preferred to avoid mal operation of the TOC 51N for unbalance system faults.

PROTECTION AGAINST SYSTEM DISTURBANCES AND FAULTS:

The capacitor bank may be subjected to over voltages resulting from abnormal system operating conditions. If the system voltage exceeds the capacitor capability the bank should be removed from service. The removal of the capacitor bank lowers the voltage in the vicinity of the bank reducing the


FIGURE 11


overvoltage on other system equipment. Time delayed or inverse time delayed phase overvoltage relays is used.

SYSTEM OVER VOLTAGE PROTECTION:

The capacitor bank may be subjected to over voltages resulting from abnormal system operating conditions. If the system voltage exceeds the capacitor capability the bank should be removed from service. The removal of the capacitor bank lowers the voltage in the vicinity of the bank reducing the over voltage on other system equipment. Time delayed or inverse time relayed phase over voltage relays are used.

RELAYS FOR BANK CLOSING CONTROL:

Once disconnected from the system a shunt capacitor bank cannot be re-inserted immediately due to the electrical charge trapped within the capacitor units, otherwise catastrophic damage to the circuit breaker or switch can occur. To accelerate the discharge of the bank, each individual capacitor unit has a resistor to discharge the trapped charges within 5min. Under voltage or undercurrent relays with timers are used to detect the bank going out of service and prevent closing the breaker until the set time has elapsed.

The protection of shunt capacitor banks uses simple, well known relaying principles such as over voltage, over currents. However, it requires the protection engineer to have a good understanding of the capacitor unit, its arrangement and bank design issues before embarking in its protection.

Unbalance is the most important protection in a shunt capacitor bank, as it provides fast and effective protection to assure a long and reliable life for the bank. To accomplish its goal, unbalance protection requires high degree of sensitivity that might be difficult to achieve.

3.8 Harmonics Flow In Electrical System

1. WITHOUT CAPACITOR

First consider a plant without capacitors. Non linear loads on the power system will act as a constant source of harmonic current. The harmonic current will flow in the direction of lowest impedance. Since the impedance of the



source is small, the harmonics in general will flow back to the source and the harmonic voltages that are produced by the flow of harmonic currents will usually be insufficient to cause any problems inside the plant Only if the harmonic loads are a high percentage of the transformer capacity will a situation such as this create harmonic problems within the plant.

2. CAPACITOR INSTALLED

In the plant where power factor correction capacitors are installed, the normal flow of Harmonics may be modified if Resonance conditions are set up by the capacitor and transformer. The Capacitor itself does not generate harmonics. Depending upon amount of capacitance and location of connection, the capacitor can create a harmful resonant circuit with inductive impedance of the system, near to the frequency of major harmonics present in the system. The resonant condition will amplify the magnitude of the harmonics flowing within the plant.


FIGURE 12

FIGURE 13


HOW CAN HARMONIC PROBLEMS BE ELIMINATED:

1- Detuning Resonance:There are number of ways to avoid resonance when installing

capacitors. In large system it may be possible to avoid resonance by relocating the capacitors in the system and varying the KVAR output rating of the capacitors. With Automatic capacitor switching there will be different resonant frequency for each step. In such cases it is very difficult to avoid resonance.

Solution: Harmonic blocking filterTo avoid resonance, a detuned reactor must be connected in series with

each capacitor such that the capacitor/reactor combination is inductive at the critical frequencies but capacitive at fundamental frequency. The percentage of reactor should be decided carefully to avoid resonance at any other predominant frequency.

2- Harmonic Suppression:

Solution: Harmonic Absorption FiltersHarmonic currents can be significantly reduced in an electrical system

by using a harmonic absorption filter. Harmonic filter is basically a series combination of capacitor and reactor tuned to provide low resistance path to the designated frequency. In theory, the impedance of the filter is zero at the tuning frequency. Therefore the harmonic current is absorbed by the filter. This together with the natural resistance of the circuit means that only a small level of harmonic current will flow in the network.


FIGURE 14


BENEFITS OF HARMONIC ABSORPTION FILTER:

There are the following advantages of harmonic filter: Reduction in Total Harmonic Distortion. Increase in Power factor. Reduction in KVA demand Reduction in Losses. Increase in KVA Demand capacity of Transformer.

HARMONICS EFFECT IN COMMERCIAL BUILDINGS:

In case of a commercial building the following background of harmonics can be obtained:

Neutral wire overheating. High unit consumption.

Harmonic analysis showed neutral wire is drawing high level of third harmonicThe harmonic source is the UPS system. The solution is by using third harmonic filtering banks. System condition after installation of capacitor bank:

No overloading of neutral wire. 4% reduction in unit consumption.


FIGURE 15


Chapter 4SYSTEM DESIGN, OPTIMIZATION AND

PAY-BACK ANALYSIS

4.1 KVAR To Be Compensated

4.2 Static VAR Capacitors Employed

4.3 Specification Of Capacitor Bank


4.5 Protection And Mountings

4.6 Payback Period Calculation

4.7 Economic Analysis



4.1 KVAR To Be Compensated:

Maximum demand= 200 KWCurrent power factor =0.77 (from the bill)

Apparent power S= P / cosφ = 200 / 0.77= 260 KVAReactive power Q= S sinφ= 260 x 0.638 =166 KVAR……..(i)Power factor needs to be improved to cosφ’ = 0.90Apparent power S’ =P / cosφ’= 200 / 0.90 = 222.2 KVAReactive power Q’= S’ sinφ’= 222.2 x 0.4358 = 97 KVAR………(ii)From equation (i) and (ii) ,KVAR to be injected in the supply to improve the power factor from 0.77 to 0.90 is 166 - 97=69 KVAR.

0.95

0.90

0.85

0.80



NOMOGRAM FOR CALCULATION OF REQUIRED KVAR RATING

For our case, maximum Load= 200 KWPresent Power factor= 0.77Desired Power factor= 0.90From the NOMOGRAM, the multiplying factor= 0.34Thus Capacitor rating Required = load x mul. Factor

= 200 x 0.34 = 68 KVAR

4.2 Static VAR Capacitors Employed Our SVAR capacitors have a long life cycle up to 100000 hrs .Our capacitors are even corona free and are very easy in handling. As long as their safety precautions are concerned, we are equipped following safety features:

Dry type design Self healing type Over pressure disconnecter Non inflammable Touch proof terminal

Our product also comprises some striking feature regarding its mounting application and general environment. They are:Mounting Reduced cost of mounting Mounting can positioned in any way Less maintenance

Environment:

Easy in disposal. Non polluting on PCB Eco- friendly



4.3 Specification Of Capacitor Bank

Capacitors Bank 20 KVAR@440V, 50Hz 3 Phase

Rs. 15000 (price according to brand, this being the minimum)Cost

Life cycle 100000 operating hours

TerminalsThreaded for secure connection. Leak free gasket seals. 10KVA standoff terminal bushings.

Dielectric Fluid Wet cells-Eccol, lll B liquid NFPA classification.

Flash Point +212 C. Fire Point: +260 C

Dielectric Film Polypropylene

COST OF KVAR CAPACITOR BANK = 4 x 15000= Rs. 60000/- only


It has the following specifications-No of capacitor banks: 4Microcontroller based controlMinimum switched bank: 1Operating voltage: 440 voltsFrequency: 50 HzTo avoid the inrush switching current, reactors are connected in series with the automatic switch.Cost: Rs. 45,000 (minimum price available -Trinity Heavy Electrical)

4.5 Protection And Mountings

Specification:Air break switches: 0.4KV, 100AFuse: HRC fuseCost of protection and mountings = Rs. 20,000/- onlyTotal expenses of the correction device = 60000 + 45000 + 20000 = Rs. 1,25,000 /- only



4.6 Payback Period CalculationSavings in one month = Rs. 6,712Saving in a year = Rs. 6,712 x 12 = Rs. 80,544Assuming zero maintenance and depreciation in the first six months of installation,Savings = Rs. 6712 x 6 = Rs. 40,272After six months, maintenance charges is about 1% of total installation cost= Rs. 1,25,000 x 0.01 = Rs. 1250/- onlyNet savings in a month after six months = Rs. 5,462/- onlyHence, number of months required to recover the total pay-back= Rs. (1,25,000 - 40272) / Rs. 5462= 15.5 months i.e. fifteen month and fifteen days.

Hence, total payback periods= 15.5 + 6= 21.5 monthsWe know, as mentioned in the capacitor bank specification the life of capacitor bank is around 1,00,000 working hours. Assuming the capacitor bank is to be connected to the load throughout the day, the life period of the capacitor bank= (1,00,000) / (365 x 24)= 11.4 yearsAfter the payback period, the remaining life of the capacitor bank i.e. ( nine years approx.) will make only profit but the maintenance charges for the capacitor bank will increase from 1 to 5%.

4.7 Economic Analysis

Mathematically KVAR required is 69 KVAR while from the NOMOGRAM the KVAR required is 68 KVAR.

Annual Penalty paid in a year is Rs. 6,712 x 12 = Rs. 80,544. The cost Of KVAR Capacitor Bank = 4 x 15000= Rs. 60,000. The cost of the Automatic Capacitor Switch is Rs. 45,000. The cost of protection and mounting devices is Rs. 20,000. The cost involved in installation is Rs. 1,25,000. The total payback period is 21 months and 15 days assuming 1%

maintenance charge of installation cost after 6 months.



Chapter 5CASE STUDY

5.1 Case Study 1

5.2 Case Study 2



5.1 Case Study 1

LOCATION: UNIVERSITY OF GHANA, LEGON What elements constitute Industrial electricity bills? Industrial electricity bills in Ghana comprise several billing elements, namely:-

Maximum demand in KVA, Electrical Energy Consumption in KWH, Power Factor surcharge, National Electrification Scheme (NES) Levy per KWH, Street Lighting Levy per kWh, and a Service Charge.

The industrial/commercial electricity user in Ghana can reduce costs by:- Reducing the maximum demand. Reducing the electrical energy consumption. Improving power factor to avoid paying.

HOW IS POWER FACTOR SURCHARGE APPLIED? Power Factor surcharges were introduced in January 1995 and

consumers whose plant power factors are below a threshold value of 0.90 are levied with a surcharge according to the following formula:-

PFS = (0.90 - Pfactual) x MD x MDcharge

where, MD is the Maximum Demand for the month in kVA, MDcharge is the maximum demand charge per kVA set by the PURC in the tariffs.

Pf actual is the actual power factor of the consumer’s system, measured by the demand meters installed by the utilities.

Unlike taxes or levies, the Power Factor Surcharge is avoidable. It is

therefore highly recommended for industrial (including mining) and commercial consumers to avoid this surcharge by improving plant power factor to 0.90 or above.

As part of measures adopted by government to reduce recurrent expenditure, the Ministry of Energy is installing Power Factor Correction equipment in five tertiary institutions. The first of the five to benefit is the University of Ghana, Legon where 26 capacitor banks were installed on transformers that serve the various halls and academic facilities of the University.



The activity was implemented by the Energy Foundation on behalf of the

Ministry of Energy. The contract for the supply and installation of equipment which was specified by the Energy Foundation was executed by AB Management & Agency Ltd, a local energy management firm and one of the few contract energy managers in the country. Equipment installation was completed in November 2005.

RESULTS:

The first results of the effect of the installation on the electricity bills of the University appeared in December when the bill for the first full month after the installation was presented. Since then, energy consumption for January and February 2006 has been collected for analysis. From the preliminary analysis the following conclusions can be drawn.

The total cost of electricity to the University has reduced from an average of ¢1.28 billion a month between October 2004 and November 2005, to a three-month average of ¢643million in December 2005 and January 2006. In December 2004 the University paid a total of ¢1.38billion on electricity.



The reduction has been mainly due to a reduction in Maximum Demand from 4,659kVA in November 2005 to 2,175kVA in December and further to 1,627kVA in January 2006. As a result of the installation Power Factor has improved from an average of 0.83 to 1. Power Factor Surcharge which averaged ¢28.5million per month has been totally eliminated.



A remarkable achievement is the reduction in energy use and consequent cost. It is important to note that the University is supplied power at 11kV and is metered at a bulk meter point before power is distributed to the various transformers scattered throughout the campus. The installation of the capacitors has reduced cable losses, (I R) losses to such an extent that actual electricity consumption has reduced. It is important also to note that in December 2004, the University consumed 1,525,130kWh of electricity as against 819,131kWh in December 2005.

COST SAVING:Compared to the electricity cost profile before the installation, the

University of Ghana is saving an average of ¢641.49million a month. This means that the cost reduction for the University of Ghana alone is enough to pay for the installations in all the five tertiary institutions in less than 4 months. The total cost of the installations in all the five institutions namely University of Ghana, Legon, University College of Education, Winneba, GIMPA, University of Cape Coast and KNUST was ¢1.9billion.



5.2 Case Study 2 Power factor improvement in a plastic factoryObjective: To evaluate the effect of installing power factor correction capacitors on equipments in a factory producing plastic sacks and containers. Also to assess the performance overtime and the economics of project.Potential users: All industries, large and small with low power factor.Investment cost: Rs. 1,31,200Savings achieved: Rs .87,709Pay-back period: 18 months

Introduction:This project was carried out under the demonstration programme of the

Gridco DSM cell supported by technical assistance from the UK department for international development (DFID). Gridco are aware that there are many small to medium industrial units in Orissa operating at low power factor values below the mandatory 0.9 level. As a result these consumers are paying more for their electricity through penalty charges and Gridco has to carry the increased reactive power loads. This in term leads to voltage fluctuations and increased transmission losses. For this reason Gridco DSM cell have launched a power factor improvement programme.

Case study summary:Jagnnath Plastics incurred regular high penalty charges for low power

factor so decided to improve it to Gridco’ s threshold of 0.9 ( or better) by the installation of capacitors to various items of equipment. It was expected that PF penalty charges and maximum demand charges would decrease. The installation was carried out, a 200 KVAR LT capacitor bank being installed with the effect that penalty charges averaging Rs 5,900 per month were totally eliminated. Maximum demand fell by 18 KVA to an average 122 KVA giving the company scope for reducing their contract demand.

The overall cost for the design, purchase and installation of the 8 capacitors with control gear, testing and commissioning was Rs. 1,31,200 giving a simple payback for the scheme of 1.5 years.

Equipment: Manufacturer / Supplier: LT power capacitors



Background of project: Contract demand is 205 KVA. Maximum demand in 1996 – 97 was 152 KVA (July).The annual electricity bill (Sep 96- Aug 97) was Rs. 20,45,125 of which Rs. 70, 701 was the power factor penalty charge. Power factor was a minimum of 0.74 but had been as low as 0.64 in the previous years. The company proceeded to have the equipment installed in March 1997. The installation was completed over one day and disruption to production was minimal.

Power Factor correction:In many electrical industrial systems, a great part of the load is due to

electric motors. The coils or windings within the motors have an inductive element that causes a reactive current which does no useful work to flow in the circuit.

There are however, methods which can be used to correct this negative, or lagging KVAR by introducing positive KVAR. The most common method is to introduce capacitors, which are devices with no moving parts and so have a very long and maintenance free life. Introducing capacitor banks will allow the plant to supply for more KVA.

Description of project: Power factor correction equipment was installed on the main incoming supply to the factory. There are 8 capacitors, each of the ration 25 KVAR controlled automatically by a micro controller which beings extra capacitance online as required.

Estimation of project cost:Total investment cost for 8 capacitors and the control equipment was

Rs. 1,31,200.

Assessment of performance:The power factor at the factory has been improved from a previous

average of 0.81 to an average of 0.92. The effect on maximum demand has been reduced to an average of 140 to 122 KVA. Economic Analysis:

Annual power factor penalty charges for the 12 months prior to equipment installation were Rs. 87, 709.



Actual installation cost of power factor correction equipment was Rs. 12,31,200.

Power factor penalty charges following installation of power factor correction equipment were nil.

Simple pay back is calculated at 1.5 years.

Environmental Benefit:The reactive current that flows in the circuit, but dose no useful work,

cause the size of the switch gear, fuse gear, cables and transformers to be greater which means increased cost to the consumer as well as T & D company.

Future potential:Nineteen industrial sites located in Cuttack, Jagatpur, Choudwar and

Bhubaneswar areas have been studied by the DSM cell. Power factor values were found varying from 0.64 to 0.88. Penalty charges were being incurred by most of these consumers. These 19 companies represent 3% of the small to medium sized industrial consumers in Orissa (load in access of 100 KW). There is therefore a potential for reducing peak demand on the transmission and distribution system of Orissa by an estimated 14 MVA by extrapolation, by power factor improvement.



Chapter 6CONCLUSION



CONLCUSION

he power factor of a power system is the major of its economy. So, the design Engineers always attempts to make this power factor as close as to unity. Power factor decreases due to the increased usage of inductive

loads as we have discussed in Chapter 2. Therefore the power distribution companies always sets up a mandatory minimum power factor at the premises of consumers. In our state the mandatory power factor is 0.9 described by the Central Electricity Supply Utility of Orissa. The decrease in power factor below this reference is compensated by the consumer based on their maximum demand and the no. of units consumed.

T

College of Engineering & Technology, Bhubaneswar has it’s transformers of different ratings and have various inductive loads which is a major cause of lagging low power factor about 0.77. So, a penalty of Rs. 6,712 is charged on account of 13% fall.

Hence, to compensate for this decrease in power factor shunt capacitor method can be used as it’s advantages are already described in Chapter 3. Proper analysis design and implementation of this capacitor banks with appropriate mounting and protecting devices will not only reduce the bill charges but also make the profit on long term.

FUTURE TRENDS OF THE PROJECT:

The electricity consumption depends upon the infrastructure, instruments and different loads. The CetB is going to consume more loads in future after the completion of main building, hostels, and staff quarters, thereby increasing the load and also a hike in energy consumption and penalty charges. The penalty charges in future will be around 4-5 times after few years. If proper steps to improve the power factor upto mandatory level will not be taken, then the college will pay more penalties of around 30 to 40 thousands in a month. Again, the tariff may increase in the coming years, which will result in more profits to the college. So the concerned authority is requested to implement this project in COLLEGE OF ENGINEERING AND TECHNOLOGY, BBSR.



APPENDIX

Average load: Average of the load occurring on the power station in a given period is known as average load.

Capacity factor: It is the ratio of actual energy produced to maximum possible energy that could have been produced during a given period.

Connected load: It is the sum of continuous rating of all the equipment connected to supply system.

Demand factor: It is the ratio of maximum demand on power station to its connected load.

Depreciation: The decrease in the value of the power plant equipment and building due to constant use is known as depreciation.

Diversity factor: The ratio of sum of individual maximum demands to the maximum demand on power station.

Fixed cost: It is the cost which is independent of maximum demand and unit generated.

Interest: The cost of use of money is known as interest. Load curve: The curve showing the variation of the load on the power

station with reference to time is known as load curve. Load factor: The ratio of average load to maximum demand during a

given period. Maximum demand: It is the greatest demand of load on power station

during a given period. Payback period: The time between which capital cost is compensated

from the day of installation is known as payback period. Running cost: It is the cost which depends only upon the number of unit

generated.



BIBLIOGRAPHY

WEBSITE:

http://en.wikipedia.org/wiki/Power_factor http://en.wikipedia.org/wiki/Power_factor_correction http://peswiki.com/energy/Directory:Power_Factor_Correction http://www.elec-toolbox.com/usefulinfo/pfcorrection.htm http://www.energycentral.com/centers/calendar/event.cfm?eid=17639 http://ambercaps.com/lighting/power_factor_correction_concepts.htm http://www.leonardo-energy.org/drupal/taxonomy/term/350 http://whitepapers.silicon.com/0,39024759,60019660p,00.htm http://powerfactorsolutions.eaton.com/ http://www.powerfactorsolution.com/8 http://whitepapers.silicon.com/0,39024759,60031583p,00.htm?

wp_user_rating=1

BOOKS:

Wadhwa C.L, Power Systems. Elgerd Olle.L, An Introduction To Energy Systems, 2nd edition.


http://whitepapers.silicon.com/0,39024759,60031583p,00.htm?wp_user_rating=1

http://whitepapers.silicon.com/0,39024759,60031583p,00.htm?wp_user_rating=1

http://www.powerfactorsolution.com/8

http://powerfactorsolutions.eaton.com/

http://whitepapers.silicon.com/0,39024759,60019660p,00.htm

http://www.leonardo-energy.org/drupal/taxonomy/term/350

http://ambercaps.com/lighting/power_factor_correction_concepts.htm

http://www.energycentral.com/centers/calendar/event.cfm?eid=17639

http://www.elec-toolbox.com/usefulinfo/pfcorrection.htm

http://peswiki.com/energy/Directory:Power_Factor_Correction

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

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

Documents

pf project report