symposium 2008 23 rd MultiTopic International Symposium March
- Slides: 35
symposium 2008 23 rd Multi-Topic International Symposium March 28 & 29 2008 UES Harmonics and Its Impact On Industrial Consumers 1
symposium 2008 Power Quality Perfect power supply should be one that is always available ways within voltage and frequency tolerances and has a pure noise free sinusiodal wave shape UES 2
symposium 2008 Power Quality It is the consumers responsibility to take steps to ensure that the quality of power delivered to his process is good enough UES 3
symposium 2008 Power Quality Care full design using high resilience techniques can minimize the effect created by power quality defects UES 4
symposium 2008 Power Quality Defects n n n UES Harmonics Distortion Blackouts Under or over voltage Dips and surges Transients 5
symposium 2008 Harmonic distortion n n UES Harmonics has always existed in electrical power system. It harmless as long as its level is not substantial. However with the recent rapid advancement of power electronics technology, so called non linear loads, such as variable speed drives, induction furnaces, Ups, computers etc. These equipments are finding their way to industrial consumers. Harmonics induced by non linear loads are potential risk if they are not predicted and controlled. 6
symposium 2008 Non Linear Load n n UES Draws current only part of cycle and acts as an open circuit for the balance cycle. Change the impedance during the cycle have the resultant wave form is distortion and no longer confirm to a pure sine wave 7
symposium 2008 n n UES This yields RMS value of distortion as a percentage of the fundamental frequency This condition is called a non-linear load or non sinusoidal load The total amount of harmonics will determined the THD Of non-linear load The more sources impedance the more voltage distortion 8
symposium 2008 n n n UES Harmonics are represented by a frequency multiple of the fundamental frequency. Harmonics are designated by their harmonic numbers or multiple of frequency Total harmonic distortion is calculated as the sequences of all harmonics divided by normal frequency 9
symposium 2008 Classification of Load UES n Linear Loads Resistance Induction motors n Non Linear Load Induction Furnace Variable Drives Speed Drives Solid State Soft starters Instrument 10
symposium 2008 Poor Power Quality UES 11
symposium 2008 Ideal Power Quality UES 12
symposium 2008 Power quality self assessment n n n n UES n Computer lock ups Flickers Equipment damage Failure of data processing equipment Problems with switching of high loads Over heat neutrals Nuisance tripping Utility metering problems 13
symposium 2008 Power quality cost n UES Power quality cost industry about 15 billion dollars per annum 14
symposium 2008 Harmonics Distortion n n UES Results high current and voltages High energy consumption Shorter equipment life Increased maintenance cost Design failure in explosion proof equipment 15
symposium 2008 Effects of Harmonic n Generators n n UES Thermal Losses Effect of Sequence Components Voltage Distortion Line Notching 16
symposium 2008 Transformers n n n UES Thermal Losses Unbalance, Distribution, Transformers and Neutral Currents. Transformer Derating 17
symposium 2008 Induction Motor n n n UES Thermal Losses Effect of Harmonic Sequence Component Explosion proof motors and voltage distortion 18
symposium 2008 Motors Effect Of Harmonics On Explosion Proof Motors n n UES They are designed on pure sine waves, the rotor may over heat due to harmonics resulting hot rotor and damage of seals. Temperature exceed the T class. EExd, EExe, EExp, EEx. N according to. EN 600341 -2%voltage distortion is permitted. 3% voltage distortion is permitted for. EEx. N asper. EN 60034 -2 o 19
symposium 2008 Induction Motor Impact n n UES 1 - Voltage harmonics causes extra losses in direct line connected motors 2 - The 5 th harmonics creates a counter rotating field, where as the 7 th harmonic creates a rotating field beyond the motors synchronous speed. The pulsating torque causes wear and tear on couplings and bearing 20
symposium 2008 Variable Speed Drives Lighting n n n UES Flicker Effects of Line Notching on lighting Potential for Resonance 21
symposium 2008 Effect s of Harmonics Capacitors Capacitive reactance decreases as the frequency increases. A relatively small percentage harmonic voltage can cause a significant current to flow in capacitor circuit UES Presence of harmonic current causes distortion in wave form If the natural frequency of capacitor bank/power system reactance is closed to a harmonic than partial resonance occur with amplified values of voltage and current, the elevated current will cause over heating. 22
symposium 2008 Uninterruptible Power Supplies (UPS) Computer & Computer Based Equipment Creates Third Harmonic UES 23
symposium 2008 Cables n n UES Thermal Losses Skin & Proximity Effects Neutral System in four-wire system. Additional Effect Associated with Harmonic 24
symposium 2008 Cables Effect of harmonics on cable n Thermal losses Example load current=600 harmonic current=42% Rms current=600 x square =651 A Increase in losses=(651/600)squrex 100 =17. 73% UES 25
symposium 2008 Miscellaneous Effects n n n n UES n n EFFECTS AND NEGATIVE CONSEQUENCE Conductor over heating/skin effect depending on frequency Capacitor failure Faulty operation of fuse and circuit breaker Increased stray losses in transformer resulting increase in iron, copper or eddy Increased losses in generator/multiple zero crossing affect the timing of the voltage regulator, causing interference and operation instability Incorrect recording by utility meters Miss operation of drives 26 Interferences in computer/telephone
symposium 2008 Measurement Harmonics Problem In Measurement Peak factor=peak value/rms value Form factor=rms/mean Measurement is based on average reading, rms calibrated, Which is measuring average(0. 636 xpeak) and multiplying the result by form factor 1. 11 This is valid only for pure sine wave Pure sine wave crest factor=peak/rms or 1. 414(1/0. 707) The higher the crest factor more accurate it will be UES 27
symposium 2008 UES Measuring Equipment Telephones Circuit Breakers Fuses Relays Radio, Television, Audio & Video Equipment Capacitors 28
symposium 2008 Inter Harmonics IEC 1000 -2 -1 n Frequencies which are not integer of the multiple frequencies n SUB HARMONICS Whose frequency is less than fundamental UES 29
symposium 2008 Allowable Limit of Current and Voltage Harmonics UES n Voltage Harmonic 5% n Current Harmonic 10% 30
symposium 2008 Harmonic Calculation 1 -Calculate the source S. C capacity and reactance 2 -Harmonic current/order = I*Ih% Voltage/harmonic order = 1. 732*h*S*Ih UES 31
symposium 2008 Harmonic Calculation 3 - Harmonics voltage as percentage= Vh/Vr X 100 4 - Transformer S. C Current = transformer full load current/transformer impedance 5 - Generator s. c = generator full load current/generator reactance 6 - Source impedance = V 2/s. c mva UES 32
symposium 2008 Example Direct Calculation Of Harmonic Voltage Distortion 1 -Transformer full load current of 2000 KVA current=2886 Amps 2 -S. C current=2886/0. 06=48. 1 KA 3 -S. C MVA=1. 732 x 400 x 48100=33. 32 MVA 4 - Supply reactance=400 x 400/33. 32 MVA=0 -00480 ohm UES HARMONIC CURRENT PER ORDER Motor full load current=962 A 5 th harmonic current=32. 27% =962 x 0. 3227=310. 44 A Voltage=1 -732 x 5 x 0 -00480 x 310. 44=12. 9 V Harmonic as% of rms=18. 6 x 100/400=3. 225 %. THD=/v 5 squre+V 7 squre+----- 33
symposium 2008 n n UES The profusion of non linear loads makes harmonics distortion of power a phenomenon of increasing amplititudes. The effects of which cannot be ignored since almost all the power network components are in practice affected. The issue of power harmonics are more apparent then ever. controlling and monitoring industrial system and their effects are a potential problem for industrial consumers. 34
symposium 2008 Thanks UES 35
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