This is the third slide set in series of Introductory course on Power Quality for undergraduates. This deals with transient over-voltages, Ferro Resonance, Over Voltage Protection, Switching Transients, Shielding
This is the third slide set in series of Introductory course on Power Quality for undergraduates. This deals with transient over-voltages, Ferro Resonance, Over Voltage Protection, Switching Transients, Shielding
HVDC (high-voltage direct current) is a highly efficient alternative for transmitting large amounts of electricity over long distances and for special purpose applications.
Introduction
Definition of FACTS system
Necessity of facts devices
Shunt connected controllers
Types of facts controllers
Shunt connected controllers
Benefits of FACTS
The concept of FACTS (Flexible AC Transmission System) refers to a family of power electronics based devices able to enhance AC system controllability and stability and to increase power transfer capability.
The design of the different schemes and configurations of FACTS devices is based on the combination of traditional power system components (such as transformers, reactors, switches, and capacitors) with power electronics elements (such as various types of transistors and thyristors).
##CONTENT##
Introduction
Voltage control
Power system control
Control of reactive power and power factor
Interconnected control and frequency ties
Supervisory control
Line compensation
Series compensation
Series and shunt compensation schemes for ac transmission system
This presentation gives detailed information about power quality i.e. how poor power quality is caused? what are the parameters on which we measure power quality? how can we solve the problem of poor power quality? this presentation will give you all the answers.
HVDC (high-voltage direct current) is a highly efficient alternative for transmitting large amounts of electricity over long distances and for special purpose applications.
Introduction
Definition of FACTS system
Necessity of facts devices
Shunt connected controllers
Types of facts controllers
Shunt connected controllers
Benefits of FACTS
The concept of FACTS (Flexible AC Transmission System) refers to a family of power electronics based devices able to enhance AC system controllability and stability and to increase power transfer capability.
The design of the different schemes and configurations of FACTS devices is based on the combination of traditional power system components (such as transformers, reactors, switches, and capacitors) with power electronics elements (such as various types of transistors and thyristors).
##CONTENT##
Introduction
Voltage control
Power system control
Control of reactive power and power factor
Interconnected control and frequency ties
Supervisory control
Line compensation
Series compensation
Series and shunt compensation schemes for ac transmission system
This presentation gives detailed information about power quality i.e. how poor power quality is caused? what are the parameters on which we measure power quality? how can we solve the problem of poor power quality? this presentation will give you all the answers.
POWER HARMONICS- SOURCES, ISSUES AND MITIGATIONASHIKS842
Various developments in the field of power system are being carried out to find a fruitful solution to mitigate the harmonics. some of the basic solutions are being described here.
SEMINAR PRESENTED ON 21 JANUARY 2017 CONDUCTED BY KERALA STATE ELECTRICITY BOARD ENGINEER'S ASSOCIATION.
Today, nearly every piece of electrical equipment generates harmonic currents and voltages. This Application Note gives a comprehensive and up-to-date overview of the subject. It explains why harmonic problems have been increasing over recent years, how they are generated, and by which type of equipment. It presents an overview of the various problems harmonic currents can create. Most of them are either related to different kinds of overloading – leading to problems of efficiency loss and overheating – or to disturbances of control and safety devices.
This Application Note also presents a brief overview of the available solutions. The four main mitigation solutions are passive shunt filters, passive series filters, isolation transformers, and active harmonic conditioners. The Application Note concludes that good design practice, the right electrical equipment, and good maintenance are the keys to preventing future problems.
Practical Power System Harmonics, Earthing and Power Quality - Problems and S...Living Online
The power system harmonics, earthing and power quality workshop is a comprehensive, highly practical and interactive course dealing with the various types of power quality problems that have a wide ranging effect on the power systems equipment and apparatus in any plant. You will have the opportunity to learn and discuss the fundamentals of power quality problems such as surges and voltage sags. Other problems having wide ranging effects on power system equipment such as voltage swells, voltage fluctuations, supply interruptions, frequency variations, harmonics and noise shall also be discussed in detail. Issues related to control of the occurrence of these problems by appropriate system design and mitigation of the effects of these by adoption of appropriate protective measures and by the addition of power conditioning equipment shall be discussed. Also, aspects related to designing of the systems, proper installation practices, analysis of the probable reasons and corrective measures will be discussed in detail. Practical examples from actual projects will be used extensively to illustrate the principles and drive home the point.
The material is covered by means of an interactive lecturing style, with plenty of practical examples and realistic case studies derived from real work performed in this area
MORE INFORMATION: http://www.idc-online.com/content/practical-power-system-harmonics-earthing-and-power-quality-problems-and-solutions-8
Application of passive harmonic filters to mitigate source side current harmo...eSAT Journals
Abstract
A combination of rectifier and DC – DC chopper is useful in feeding DC loads where the DC input to the loads needs to be stepped up or down. Both rectifier and chopper are based on power electronic switches which inject harmonics in the system. This harmonics is an undesirable effect which should be mitigated effectively. For this, passive harmonic filters are used. Passive harmonic filters are a simple and economical option for harmonic mitigation. Thus they find widespread application in various power systems. This paper deals with the analysis of harmonic distortion caused in a typical AC system feeding a DC motor through a rectifier and boost chopper setup. The analysis is done before and after the incorporation of passive harmonic filters on the AC side in order to study the effect of the same in the mitigation of source side harmonics. Key Words: – Total Harmonic Distortion - THD, boost chopper, harmonics, tuned filters, resonance
Effect of non sinusoidal waveform of a.c. machine performancevishalgohel12195
Effect of Non sinusoidal waveform of A.C. Machine performance
Nonsinusoidal Waveforms
Key Similarities and Differences between Sinusoidal and Nonsinusoidal Waveforms
Effect of harmonics in motor drives
Square wave inverter with 180° mode
Effect of leakage reactance on the harmonic content of current
Parasitic torques due to non-sinusoidal voltages
Imagine improving your money, time and health freedom through the Happy Life Project and loving every moment of it.
Visit http://www.slimhealthysingapore.com/happy-life-project/ for more information.
TOTAL HARMONIC DISTORTION POWER METER BY EMBUILT TECHNOLOGIESEmbuilt Technologies
THDPM-1 is THD analyzer which measures upto 51st harmonic.It provides Voltage and Current THD.It shows the net effect on THD due to load.
It also shows following parameters-
Voltage
Current
Watt
Frequency
Power Factor
It is useful for testing of LED Drivers, SMPS, CFL, CHOKES etc.
Application of Capacitors to Distribution System and Voltage RegulationAmeen San
Application of Capacitors to
Distribution System and Voltage
Regulation
POWER FACTOR IMPROVEMENT,
System Harmonics
Voltage Regulation
Methods of Voltage Control
You can learn about ECG AMPLIFIER, INSTRUMENTATION AMPLIFIER, ECG AMPLIFIER DIAGRAM, VALUE OF RC TIME CONSTANT ?, DRIVEN-RIGHT-LEG SYSTEM, EQUIVALENT CIRCUIT FOR THE INPUT OF AN ECG AMPLIFIER, Method to increase input impedance, Active filters, FREQUENCY RESPONSE, LOW PASS FILTER, HIGH PASS FILTER, BAND PASS FILTER, Resonant frequency, Quality factor or Q factor
VIDEO LINK: https://youtu.be/sBG17ffSh40
Refer this link to get idea about instrumentation amplifier
https://youtu.be/-j8ePvHOuGk
Identification and minimization of HarmonicsMayur Hiwale
In this ppt we will get to know about basic idea of harmonics, types of harmonics , measuring devices and minimizing techniques and also covering the there impact on power system and impact on consumer equipment's.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
4. Power System Impedance
• At low frequencies Power System Impedance is
determined by the impedance of the Transformer and
the Transmission lines. At Higher frequencies it is
determined by the impedance of the Power Factor
correction Capacitors.
• There is an intermediate range of frequencies where
the Capacitive and Inductive effects combine together
to give a very high impedance. A small Harmonic
Current within this Frequency range can give a very
high and undesirable Harmonic Voltage.
• This is the condition which is called Resonance
5. HARMONIC RESONANCE
• Harmonic resonance is generally caused by parallel
resonance between the Power Factor Correction capacitors
connected to a load and the transformer supplying that
load. When a number of harmonic current sources are
injecting currents into the supply and the frequency of one
of the harmonics coincides with the resonant frequency of
the supply transformer and Power Factor Correction
capacitor combination, the system resonates and a large
circulating harmonic current is excited between these
components. The result of this is that a large current at this
harmonic flows in the supply transformer, thus resulting in
a large harmonic voltage distortion being imposed upon
the load voltage.
6. HARMONIC RESONANCE CONTD---
• THE FORMULA TO DETERMINE THE ORDER OF
HARMONIC THAT MAY CAUSE RESONANCE IS
• Hr =
• SUPPOSE 20 MVAR CAPACITOR IS CONNECTED
ACROSS A SYSTEM OF 1000MVA SOURCE THERE
WILL BE CONDITION OF RESONSNCE AT 7TH
HARMONIC
• THE POSSIBILITY OF RESONANCE SHOULD BE
EXPLORED AND ELIMINATED DURING ANY
MODIFICATION OR ADDITION OF LOAD IN THE
POWER SYSTEM
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Resonance Frequency
• Resonance occurs at a frequency where system inductive
impedance equals capacitive impedance
• 2πftL =
• ft =
• In a typical system the order of Harmonic (Hr) where
resonance occurs can be calculated as
• Hr =
• For 1000 MVA source and 20 MVA capacitors
• Hr = = = 7.07
8. Power System Impedance
• Harmonic Order Nr where Resonance can occur is given by ‘Square Root’ of
• Short Circuit MVA of Source divided by MVAR of connected Capacitors.
•
• Nr =
• For 100 MVA Short Circuit Level and
800 KVAR Connected Capacitors
Nr =
• This is close to 11th Harmonic which may be present due to certain loads and will
cause Resonance at this undesirable point.
• If the Connected Capacitors are reduced to 500 KVAR then Nr increase to 14.1
and the risk of resonance at undesirable frequency close to some prevalent
Harmonics is eliminated.
9. HARMONIC RESONANCE CONTD
• SINGLE LARGEST CAUSE OF SEVERE
HARMONIC DISTORTION IS RESONANCE
• A NORMAL HARMONIC MAY BE AMPLIFIED 10
TO 25 TIMES IF RESONANCE OCCRSC AT OR
CLOSE TO CRITICAL FREQUENCIES
• IT OCCURS MAINLY DUE TO INDISCRIMINATE
USE OF PF CAPACITORS OR BECAUSE OF
INCORRECT APPLICATION OF FILTERS
10. LOAD ALLOCATION ON A
TRANSFORMER
• If a Transformer is loaded with mainly non
linear load the supply is highly corrupted as
there is no Damping of Harmonics
Amplification due to absence of linear load.
• Allocating combination of linear and non
linear loads on a Transformer is advisable as it
dampens the Harmonic Amplification and
minimizes Filtration needs
11.
12. OVERCOMING RESONANCE
• SERIES COMBINATION OF REACTOR AND
CAPACITOR TO CONTROL SYSTEM IMPEDENCE
TO AVOID RESONANCE CONDITION WHICH
CAN AMPLIFY HARMONIC CURRENT.
• THE COMBINATION SHOULD BE INDUCTIVE AT
CRITICAL FREQUENCY BUT CAPACITIVE AT
FUNDAMENTAL FREQUENCY FOR THIS
TUNING FREQUENCY SHOULD BE BELOW
LOWEST ORDER HARMONIC 5TH (250 HZ)
14. Harmonic Generation by Nonlinear
Loads
• UPS
• DC DRIVES
• VFD
• THYRISTOR CONTROLLED HEATING
• INDUCTION FURNACES
• ELECTRONIC CHOKES FOR FUORESCENT LAMPS
• BATTERY CHARGER
• WELDING CONTROLS AND RECTIFIERS
• SMPS SUPPLIES
15. ADVERSE EFFECTS OF HARMONICS
• INCREASED HEATING DUE TO IRON AND
COPPER LOSSES AT HARMONIC FREQUENCIES
• CHANGE IN PERFORMANCE CHARACTERISTICS
OF ELECTRICAL AND ELECTRONIC
EQUIPMENTS
• OVERLODING OF NEUTRAL
• CAPACITOR FAILURES
• SPURIOUS TRIPPINGS
• ERATIC OPERATION OF CONTROLS
16. ADVERSE EFFECTS OF HARMONICS
• INTERFERENCE WITH COMMUNICATIONS
• MEASUREMENT ERRORS IN METERING
DEVICES
17. RELEVANCE OF HARMONICS TODAY
• HIGH NON LINEAR LOADS
• VISIBILITY OF PROBLEM BECAUSE THE
MEASURES TO TACKLE HARMONICS ARE NOT
IN PLACE
• INCEASED USE OF CAPACITORS FOR PF
IMPROVEMENT LEADING TO AMPLIFICATION
OF HARMONICS
18. Series Resonance
At tuning frequency ft
XL = XC
• 2πftL =
• ft =
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19. • Capacitive Reactance decreases with frequency and inductive
reactance increases with frequency
• The total reactance of the combination takes minimum value at
resonance frequency
• The total reactance of the combination takes minimum value at
resonance frequency
• For 7% resonance frequency = 189Hz
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20. Series resonance
• Tuning frequency for 7% detuned reactor in LC series
circuit
• Detuning ratio p = 0.07
• Fundamental frequency = fn
• Tuning frequency = ft
• L = Inductance
• C = Capacitance
• 2πfnL = x 0.07
• fn
2 = x 0.07
23. DETUNED FILTERS
• DETUNED FILTER IS A SERIES LC CIRCUIT
TUNED TO AVOID RESONANCE CONDITION. IT
OFFERS LOW IMPEDENCE PATH TO SELECTED
HARMONIC FREQUENCIES DETERMINED BY
THE TUNING FREQUECY. IT PROVIDES
CAPACITIVE KVAR TO THE SYSTEM AND A
NOMINAL REDUCTION OF HARMONICS
24. DETUND FILTERS CONTD---
• VOLTAGE RISE ACROSS CAPACITOR
Vrise % = ( )2 x 100
Fn is Network Frequency
Ft is Tuning Frequency of LC combination
• 5.67% DETUNED FILTER– 210 HZ TUNING
FREQUENCY
• 7% DETUNED FILTER – 189 HZ TUNING
FREQUENCY
• 14% DETUNED FILTER – 134 HZ TUNING
FREQUENCY
25. Typical Solutions Applied to Resonant
Power Systems – Detuning Reactors
• This solution involves connecting a reactor in series with the Power
Factor Correction capacitor such that the tuning frequency of the L-
C combination is 189Hz (50 Hz system). This tuning frequency is
chosen in order to ensure that this capacitor branch appears
inductive for all of the major harmonics on the system, thus
eliminating the possibility of a resonance occurring. Any resonance
involving the 3rd harmonic is ignored as Power Factor Correction
capacitors are generally connected in a Delta configuration, this
preventing any 3rd harmonic (zero sequence) current flow. The
tuning frequency is chosen to be far enough below the 5th harmonic
to avoid the Power Factor Correction capacitor filtering the 5th
harmonic current but not so low that an excessive voltage rise is
produced across the capacitor at the fundamental frequency.
26. Typical Solutions Applied to Resonant
Power Systems – Partial Filtration
• This solution involves connecting a reactor in
series with the Power Factor Correction capacitor
such that the tuning frequency is approximately
210Hz (50 Hz system). This configuration is series
resonant quite close to the 5th harmonic (250Hz)
and as such affords a degree of harmonic
filtration. Using this configuration will remove
typically 50% of the 5th harmonic current and
30% of the 7th harmonic current. This
configuration would be used where the existing
harmonics are higher than the ideal level but not
so high that a full filtration system is required.
27. Typical Solutions Applied to Resonant
Power Systems – Full Filtration
• This configuration involves a number of
capacitor arms being tuned very close to
particular harmonic frequencies with the
express purpose of removing these
harmonics. In the example shown the 5th and
7th harmonics are being targeted.
• TUNING FREQUENCIES ARE 240 HZ AND
334HZ
28. TUNED FILTERS
• TUNED FILTER IS AN LC CIRCUIT THAT IS
TUNED TO PROVIDE BOTH A HARMONIC
CURRENT REDUCTION WHILE AVOIDING A
RESONANCE CONDITION. IT IS TUNED CLOSE
TO THE FREQUENCY OF A SPECIFIC HARMONIC
CURRENT WITH THE GOAL OF PROVIDING A
LOW IMPEDANCE PATH TO THAT HARMONIC
CURRENT THUS REDUCING THE AMOUNT OF
THAT HARMONIC CURRENT FROM BEING
INJECTED INTO THE DISTRIBUTION NETWORK
31. SYSTEM HARMONIC IMPEDANCE
• This graph shows how the system harmonic impedance
varies with 400 KVAr connected in the various
configurations detailed in the previous slides. Clearly,
the plain capacitor solution results in the highest peak
harmonic impedance at the 7th harmonic. The full
filtration has two peaks at the 4th and 6th harmonics.
However, these harmonics do not naturally occur and
the impedance at the significant harmonics (5th and 7th)
is very low. The other systems provide a moderately
low impedance throughout the harmonic range but
most importantly, avoid any resonant peaks.
32. COMPARISON OF HARMONIC
RESONANCE SOLUTIONS
• This slide shows the harmonic voltage
distortion resulting from the implementation
of the four capacitor configurations
mentioned earlier. The voltage distortion
resulting from the connection of plain
capacitor banks is not acceptable whereas
that resulting from all the other solutions is.
33. Objectives of Harmonic Mitigation
• To have normal operation of all electrical
equipments and to get their normal expected
life
• To obtain operational efficiency and energy
efficiency
• To maintain power quality
• To meet the harmonic current and voltage
distortion limits prescribed by international
standards or by utility supply companies.
34. Why to use Segmented Film MPP
Capacitors
• Inherently safe and Environment friendly construction
• Can safely clear an internal fault or a voltage transient without
isolating the capacitor
• Can isolate the capacitor safely at the end of service life or in
extreme loading conditions
• Fine manufacturing tolerances
• Absence of any trapped moisture and impurities
• Better suitability for handling high frequency harmonics due to their
low ESR values
• High power density leading to compact low space construction
• Excellent quality uniform metal layer end connection with metal
spray
• Lower CO2 emission requirements
35. Capacitors with High Current Carrying
Capacities
• The IEC standards require capacitors to be capable of
continuously handling 130% of rated current but in
harmonic environment this value can be exceeded and
values higher than 200% can only be considered safe.
This is now becoming possible with the advent of
segmented MPP type low ESR capacitors which have
excellent over current handling capabilities. ESR value
assumes higher significance in view of high frequency
harmonics being handled by capacitors. ESR value had
a limited significance when fundamental frequency
current was the only consideration.
36. Problems with APP Capacitors
• Absence of inherent safety features
• High dissipation factor
• High manufacturing tolerances
• Poor quality of bimetallic end connections
• Abnormally high operating temperatures
• Loose winding with trapped moisture and
impurities
• Low power density leading to higher space
requirements
• Higher CO2 emission requirements
37. Inherent Capacitor Safeties
• The absence of any inbuilt safety mechanism to
clear internal faults leads to continued operation
under abnormal conditions of over temperature,
over pressure and degradation of oil, thus leading
ultimately to complete failure under unsafe
conditions. The undesirable mode of failure
under heavy loads, or at the end of service life
has made APP capacitors unusable worldwide for
LT applications. The ongoing research for
development of HT capacitors with a superior
and safer technology may soon phase out APP
capacitors for HT applications too
38. Ventilation and Cooling Requirements
• Capacitor panels need adequate ventilation and
cooling. Present day practice where reactors and
thyristor switching are increasingly becoming part
of capacitor panels, the cooling needs assume
greater significance. Compartmentalized
construction is unsuitable and needs to be
discontinued. Similarly these reactive power
systems should not be clubbed with MCC and
PCC panels as the design, performance and
operating requirements are more complex and
need specialized attention.
39. Where to apply Harmonic Mitigation
Scheme
• The technical benefits of applying harmonic
solutions are available upwards of the point
• of application. Most solutions today are applied
by users close to the point of utility company’s
supply to meet mainly statutory requirements.
The harmonic solutions need to be shifted
downwards closer to the harmonic generating
loads in order to pass on the benefits to both the
utility company and the user.
40. Reactors
• Reactors should have Class F or Class H insulation level, less than 10
watts per Kvar power loss, continuous current handling capacity of
150% of rated value or higher, Linearity of 175%. In a changed
scenario the utility companies are moving towards imposing
significant penal charges for not maintaining harmonic levels below
specified values. At times the specified maximum limits are more
stringent than those recommended as per IEEE519. This calls for
following an elaborate and accurate designing process for reactor
selection. A hitherto common practice of using a 7% reactor which
was mainly meant to provide some protection to capacitors may
have to be done away with in favor of reactors which can provide
filtration to achieve desired harmonic levels. Reactors also dampen
effect of transients during capacitor switching.
41. Step configuration
• Step configuration involving sizing of individual steps and
number of total steps needs to be carefully selected to
avoid resonance occurrence at switching of any step. It may
be necessary to skip a particular step to achieve this
purpose. Most designers will have specific software
developed for the purpose. Indiscriminate selection of step
sizes and number of steps may lead to some undesirable
combination resulting in resonance occurrence and
resultant pitfalls thereof. Here the clients and consultants
who often inadvertently suggest particular step
combinations need to be warned of the possible dangers. It
is best to leave this exercise to the designers after giving
them the broad guidelines about the least count of power
factor correction over the normal operating range.
42. 29-Jul-15 42It's All About Saving Your Money !!!
IEEE 519 1992
Total Harmonic Distortion (Current)
• Where I1 is fundamental component
Total Demand Distortion (Current)
• Where IL is the maximum demand load current of the
facility within 15 or 30 minutes demand window.
43. 29-Jul-15 43It's All About Saving Your Money !!!
Detuning Frequencies
• For series LC Detuned Filters the tuning frequency (Ft) is set
below the lowest Harmonic with remarkable amplitude which
is normally the fifth Harmonic
Where f = fundamental frequency P = Detuning Ratio in
percentage
• For 7% Detuning Ratio
44. 29-Jul-15 44It's All About Saving Your Money !!!
• For 5.67% Detuning Ratio
• For 14 % Detuning Ratio
45. 29-Jul-15 45It's All About Saving Your Money !!!
Power Factor Correction
Case 1
• KVA Capacity of source required is 100 KVA, Active power is
80 KW and Reactive Power is 60 KVAR
• Reactive power is supplied by the source
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Power factor correction in the
presence of Harmonic Generating Loads
• Capacitors provide low impedance path to harmonics
• If the resonance caused by addition of capacitors occurs near
any of the generated harmonics then the harmonics get
amplified
• Capacitors get stressed due to flow of harmonics through them
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Reactive Power Requirement
• Initial power factor Cos ᴓ1
• Desired power factor Cosᴓ2
• Initial reactive Power Q1 =
Ptanᴓ1
• Final reactive Power Q2 = P
tanᴓ2
• Required reactive Power
= ᴓ1 - ᴓ2
= P tanᴓ1 - P tanᴓ2
= P (tanᴓ1 - tanᴓ2)
= P (Multiplying factor)
48. 29-Jul-15 48It's All About Saving Your Money !!!
Voltage across Capacitor in a
series LC Filter
Vc = Voltage across capacitor
Vn = System voltage
P = Detuning Ratio in percentage
For 7% detuning ratio
• Plus 10 % Tolerance = 520 V
• Next available standard voltage is 525 V
49. • For 5.67% Detuning Ratio
Next available standard voltage is 525 V
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50. Capacitor inrush current
Isolated bank
• Isolated bank
•
• Ipk = inrush current
• Ft = inrush transient frequency
• Io = Steady State current value
• Fo = power frequency
• Ipk is 5 to 15 times the normal capacitor current
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51. Discharging of capacitors
• IEC 60831-1 Clause 22
• Each capacitor unit/bank is provided with a means for
discharging each unit in 3 min. to 75 volts or less
• From an initial peak voltage of times rated voltage Un
• In a single phase unit
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52. • R = Discharge Resistance in Ω
• t = Discharge time from Un to Ur in seconds
• Un = Rated voltage in volts
• Ur = Residual voltage in volts
• K = Coefficient depending on connection module of resistor to
capacitor (k=1 for R in parallel with C )
• C = Capacitance in Farads
• Indian standards
Discharge time = 1 min
Residual voltage = 50 V
•
29-Jul-15 52It's All About Saving Your Money !!!
53. 6-pulse diode rectifier
• The most common rectifier circuit in 3-phase AC drives is a
6-pulse diode bridge. It consists of six uncontrollable
rectifiers or diodes and an inductor, which together with a
DC-capacitor forms a low-pass filter for smoothing the DC-
current. The inductor can be on the DC- or AC-side or it can
be left totally out. The 6-pulse rectifier is simple and cheap
but it generates a high amount of low order harmonics 5th
especially with small smoothing inductance.
• If the major part of the load consists of converters with a 6-
pulse rectifier, the supply transformer needs to be
oversized and meeting the requirements in standards may
be difficult. Often some harmonics filtering is needed.
54. 12-pulse diode rectifier
• The 12-pulse rectifier is formed by connecting
two 6-pulse rectifiers in parallel to feed a
common DC-bus. The input to the rectifiers is
provided with one three-winding transformer.
The transformer secondaries are in 30° phase
shift. The benefit with this arrangement is that
in the supply side some of the harmonics are
in opposite phase and thus eliminated. The
major drawbacks are special transformers and
a higher cost than with the 6-pulse rectifier
55. 18 pulse and 24-pulse diode rectifier
• 18 pulse converter uses three sets of 6 pulse
bridge rectifiers that are supplied from three
different power sources each of which are phase
shifted by 20 electrical degrees. This results in
cancellation of the 5th, 7th, 11th and 13th
harmonics
• 24-pulse rectifier has two 12-pulse rectifiers in
parallel with two three- winding transformers
having 15° phase shift. The benefit is that
practically all low frequency harmonics are
eliminated but the drawback is the high cost.
56. FORMULAE
• KVAR = 2 π f CV² (Capacitive KVAR 1 Ph)
• KVAR = √3 2 π f C V² (Capacitive KVAR 3 Ph)
• KVAR = V²∕ 2 π f L (Inductive KVAR 1 Ph)
• KVAR = √3 V²∕ 2 π f L (Inductive KVAR 3 Ph)
57. FAULT LEVEL CALCULATIONS
Transformer Fault MVA =
Transformer MVA Capacity/ Per Unit Impedance
For 10 MVA Transformer having 9 % Impedance
Fault MVA = 10/.09 = 111MVA
58. Conclusion
• There is increasing presence of non linear loads leading to
harmonic generation and their further amplification due to
resonance conditions induced by capacitors. To safeguard
their installation utility companies are rightly coming out
with penal tariff structures. Correctly designed effective
harmonic solutions designed by using ETAP or equivalent
software which can provide greater filtration volumes are
imperative. Precautions need to be taken while allocating
loads on transformers, ensuring avoidance of resonance
while adding capacitors steps and selecting only reliable
and technologically superior components. A casual
approach in selecting capacitor steps and reactor detuning
factor may lead to resonance and associated problems.