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Hormonics impact and_mitigation

Power Quality

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Hormonics impact and_mitigation

  1. 1. Harmonics Impact and Mitigation R.Panneer Selvam, B.E.,M.I.E, Former Superintending Engineer Tamil Nadu Electricity Board Mob- +91 9444389547 Mail id :
  2. 2. LIFT
  5. 5. SERVICE LIFT 2
  6. 6. Harmonic Generation Harmonics are mainly produced by non-linear loads which draw current of a different wave form from the supply voltage (see fig. ) The spectrum of the harmonics depends on the nature of the load. Harmonic voltages occur across network impedances resulting distorted voltages which can disturb the operation of other users connected to the same supply Degradation of network voltage caused by a non-linear load.
  7. 7. Main sources of harmonics Industrial loads Power electronic equipment: drives, rectifiers (diode or thyristor), inverters or switching power supplies; Loads using electric arcs: arc furnaces, welding machines, lighting (discharge lamps, fluorescent tubes). Starting motors using electronic starters and power transformers energisation also generates (temporary) harmonics. Domestic loads with power inverters or switching power supplies such as television, microwave ovens, induction hotplates, computers, printers,photocopiers, dimer switches, electrodomestic equipments, fluorescent lamps.
  8. 8. Harmonic levels The sources usually generate odd harmonic components (see fig. in next slide ). Power transformer energisation, polarised loads (half-wave rectifiers) and arc furnaces generate even harmonics in addition to odd harmonics components.  Inter harmonics are sinusoid components with frequencies which are not integer ultiples of the fundamental component (they are located between harmonics). They are due to periodic or random variations in the power drawn by various devices such as arc furnaces, welding machines and frequency inverters (drives, cycloconverters).
  9. 9. Characteristics of certain harmonics generators
  10. 10. Characteristics of certain harmonics generators
  11. 11. Harmonic Impact on Electrical Network Higher usage of of “Energy Efficient” power Electronics loads ( Nonlinear loads) pollute Electrical networks with harmonics In extreme cases excessive harmonic may lead to failure of equipment The usage of PF correction Capacitors further complicates the situation Capacitors don’t generate harmonics but may result in “Resonance”, when interact the presence of harmonics with the existing network.
  12. 12. EFFECT OF HARMONICSIN ELCTRICAL NETWORK  Harmonics have varied effect on the equipment and devices. The classified as  Instantaneous Effect , and  Long Term Effect
  13. 13. INSTANTANEOUS EFFECT Series / Parallel Resonance may happen Vibration and noise in Transformers, Reactors and Induction Motors Mal functioning sensitive electronics devices (PLC Circuits, Measuring and Lab Equipments ) Increase of zero sequence component – Hot neutral Interference in communication and control circuit ( Telephone, control and Monitoring circuit ) Total energy requirement to perform desired function increases.
  14. 14. MEDIUM TERM EFFECTS Failure of rotating machines Harmonic rotating field cause pulsating mechanical torque resulting in vibration and increased mechanical failure. Reduction in capacitor Life Draws high current and results in reduction in life. Premature failure in equipments such as Transformers , cables etc. Harmonics causes additional iron loses and and copper losses ( due to Skin effect)  Leads to increase in operating Temp  Cause premature failure
  16. 16. DIRECT COST Increased energy consumption due to higher losses
  17. 17. INDIRECT COST Maintenance Cost Because of the problems listed above, maintenance activity increases Due to heating , the insulation of motors degrades, warranting rewinding and results in increased maintenance cost Down-time cost Failure of equipment increases the down time and results in production cost Losses will be more on continuous process industry like petrochemical paper and cement industries. Equipment Replacement cost High level of harmonics may result in failure of equipment in electrical network ( Eg. PF correction capacitors, sensitive PLC cards, electronic devises etc. Result in replacement cost
  18. 18. INDIRECT COST ( Contd.) Equipment de-rating Cost When harmonics are present in the network equipments connected should have immunity level to harmonics Or, the equipment shall be de-rated. According to IEC 61000-2-4 electrical networks are classified as  Class – 1 - upto 5% THD  Class – 2 - upto 8% THD  Class – 3 - upto 10% THD Equipments to be designed to class 3 network will be costlier than for class 1 network
  19. 19. INDIRECT COST ( Contd.) Safety cost Safety criteria is extremely important in modern buildings whether commercial or residential Triplen harmonics are odd multiples of third harmonics Common in Single phase SMPS driven loads like computer, television and other office equipments They are abundant in IT parks and modern buildings The magnitude of neutral current may exceed the line current. Conventionally designed neutral current may get over-loaded, causing fire hazard. This can cause neutral open, and result in dangerous over voltage across single phase equipments  Resulting in equipment failure  Pose a serious risk to life of operating personnal
  20. 20. Safety cost Safety criteria is extremely important in modern buildings whether commercial or residential Triplen harmonics are odd multiples of third harmonics Common in Single phase SMPS driven loads like computer, television and other office equipments They are abundant in IT parks and modern buildings The magnitude of neutral current may exceed the line current. Conventionally designed neutral current may get over-loaded, causing fire hazard. This can cause neutral open, and result in dangerous over voltage across single phase equipments Resulting in equipment failure Pose a serious risk to life of operating personnal
  21. 21. HARMONIC MITIGATION SOLUTION There are several methods of harmonic mitigation Harmonic mitigation shall provide following benefits  Reduce harmonic level to a desired level  Provide required Capacitive KVAR to improve PF  Prevent series or parallel resonance
  22. 22. TYPES OF HARMONIC FILTERS Harmonic Filters Active Harmonic Filters Passive Harmonic Filters Detuned Filters Hybrid Harmonic Filters Tuned Filters 7 % 14% Single Phase 3 Ph 4 wire 3 Ph 3 wire
  23. 23. PASSIVE HARMONIC FILTER  A series combination of reactor (L) and capacitor ( C )  Impedance based filter  Filtering capability depends on relative impedance w.r.t network impedance  The Reactor blocks the harmonic current flow to the capacitor  They are further classified as detuned or tuned based on proximity of its self tuned frequency  Self resonance frequency related to tuning factor  Tuning Factor p % =( XL / XC ) * 100  Tuning Frequency fr (HZ) = fs / (p/100) , where fs is fundamental frequency.
  24. 24. DETUNED FILTER If the tuning frequency of the filter is lower than 90%of the lowest harmonic frequency with considerable amplitude, it is called the “Detuned filter”  Eg. 7% tuning factor corresponds to the resonant frequency of 189 Hz ( fs = 50HZ)  Is a detuned filter for 5th harmonics ( 250 HZ )  It acts as capacitor for frequencies lower than its tuning frequency  As an inductor for higher frequencies  Series / parallel resonance at frequencies higher than tuned frequency is eliminated as the filter behaves like an inductor.  As it behaves like a capacitor for frequencies below tuning frequencies, care shall be taken to ensure that no significant harmonic component present below tuning frequency 
  25. 25. TUNED FILTER If the resonant frequency of the filter is within 10% of the harmonics to be filtered Called as tuned filter Carry more current as they offer low impedance path More expensive Used only in Special cases- where detailed system study was carried out Efficiency changes when network is modified. Several tuned filters are to be used in parallel, if more than one harmonic frequency to be filtered.
  26. 26. APPLICATION CONSTRAINTS FOR IMPEDANCE BASED (PASSIVE) FILTERS Sensitive to changes in the network Cannot handle wide spectrum of harmonic distortion Sensitive to System frequency changes Location limitations especially in vicinity of AC / DC drives Likely to permanently fail in case of sustained harmonic over load. Prier Knowledge of harmonic spectrum is required
  27. 27. ACTIVE HARMONIC FILTER • New generation of harmonic filters • Very high Speed IGBT ensuring response time of a few milliseconds • Capable of generating wide spectrum of harmonic currents to inject into the network to cancel the harmonic current drawn from the source by nonlinear loads • Additionally they can generate both capacitive and inductive reactive power in a step-less manner improving the PF of the load.
  28. 28. HYBRID FILTERS A combination of detuned and Active filter Active filters are used to handle the dynamically varying harmonic component and Detuned filters handle more predictable narrow band in addition to providing capacitive reactive power compensation at fundamental frequency
  29. 29. Impact of Harmonics The consequences of harmonics are linked  to the increase in peak values (dielectric breakdown),rms values (excessive overheating) and  to the frequency spectrum (vibration and mechanical stress) of voltages and currents. The effects always have an economic impact resulting from the additional costs linked to:  degradation in the energy efficiency of the installation (energy loss),  oversizing of equipment,  loss of productivity (accelerated ageing of equipment, unwanted tripping).  Malfunctions are probable with a harmonic distortion factor of greater than 8 % of the voltage.  Between 5 and 8 %, malfunctions are possible.  Thermal control devices. Indeed, when protective devices of this type calculate the rms value of the current from the peak value, there is a risk of error and unwanted operation even during normal operation with no overload.
  30. 30. Impact of Harmonics Disturbances induced by low current systems (remote control, telecommunications, hi-fi systems, computer screens, television sets). Abnormal vibrations and acoustic noise (LV switchboards, motors, transformers).  Destruction of capacitors by thermal overload If the actual frequency of the upstream capacitor-network system is similar to a harmonic order, this causes resonance and amplification of the corresponding harmonic. Loss of accuracy of measurement instruments A class 2 induction energy meter will produce in current and voltage, a 0.3 % additional error in the presence of 5 % of harmonic 5.
  31. 31. Impact of Harmonics Long term effects Current overload produces excessive overheating and leads to premature ageing of equipment:  Overheating of sources: transformers, alternators (through increased joule and iron losses). Mechanical stress (pulse torque in asynchronous machines). Overheating of equipment: phase and neutral conductors through increased joule and dielectric losses. Capacitors are especially sensitive to harmonics as their impedance decreases in proportion to the harmonic order.  Destruction of equipment (capacitors, circuit breakers,etc.)
  32. 32. Impact of Triplen Harmonics Overload and excessive overheating of the neutral conductor may result from the presence of third harmonic (and multiples of 3) currents in the phase conductors which add in the neutral. The TNC neutral earthing system uses the same conductor for neutral and protection purposes. This conductor interconnects the installation earth, including the metal structures of the building. Third harmonic (and multiples of 3) currents will flow through these circuits and produce variations in potential with the following results:  corrosion of metal parts,  overcurrent in the telecommunication links between the exposed-conductive- part of two devices (for example, printer and computer), electromagnetic radiation causing screen disturbance (computers, laboratory apparatus).
  33. 33. Effects of harmonics and the normal permitted levels
  34. 34. Remedial measures
  35. 35. Remedial measures
  36. 36. Remedial measures
  37. 37. Harmonic mitigation in M/S Hindustan Unilever Ltd.
  38. 38. Harmonic Filter Erected at HLL
  39. 39. CASE STUDY – 5 Jindal Steel & Power Ltd. DRI-II, Raigarh (MP) 4 Nos.150 Amp AF3 at KILN – 8 Existing Set - up at DRI - II Plant The major loads in DRI :  DC Thyristor Drives  UPS’s  AC Drives
  40. 40. The existing power Distribution in DRI - No. of KILNs - 4 Nos. - No. of Power Supply Transformer – 4 Nos. - Transformer rating – 1.7MVA - Load Distribution- One Trafo for per KILN. - Spare Transformer – 1 No. - Transformer efficiency (@ PF-1, assumed) – 98%
  41. 41. Problems Faced by user - Cable Over heating - Transformer over heating - Frequent failure of electronic PCB’s for unknown reasons - Frequent tripping of breakers resulting into interruption in process
  42. 42. Performance Results of AF3 Sr. No . Test Condition Phase R Y B 1 With One AF3 Connected Load Current (Amp) 558 A 612 A 560 A Current T.H.D. % 27.60% 29.40% 28.50% Power Factor 0.63 2 With Two AF3 Connected Load Current (Amp) 540 A 590 A 540 A Current T.H.D. % 7% 10% 10% Power Factor 0.72 3 With Three AF3 Connected Load Current (Amp) 480 A 487 A 482 A Current T.H.D. % 8% 7.90% 6.90% Power Factor 0.8 4 With Four AF3 Connected Load Current (Amp) 340 A 350A 344 A Current T.H.D. % 7.80% 8% 6% Power Factor 0.92
  43. 43. Customer Delivered Value Direct 1) Savings in KVA 2) Savings in Transformer losses (KW) Indirect 3) With AF3 two distribution transformers freed for future expansion 4) Cable temperature reduced 5) Stopped frequent & spurious tripping of MCCBs 6) Spurious blowing of fuses in distribution controlled 7) Due to improvement in power quality, the electronic control systems and logics are well protected 8) KVA demand is made free for additional usage
  44. 44. Summary of AF3 Test Results • Input currents reduced from 680 A to 350 A per phase. • Input PF is improved from 0.57 to 0.92 • Input current distortion reduced from 57% to 7-8% • Input KVA reduced from 489 to 252 KVA • KVA Released - 237KVA (direct reduction) • Existing transformer of 1.7 MVA was supporting 0.97 MW load earlier Now, it can support 1.56 MW load, if Harmonics & PF are controlled.
  45. 45. • Input currents reduced from 680 A to 350 A per phase. • Input PF is improved from 0.57 to 0.92 • Input current distortion reduced from 57% to 7-8% • Input KVA reduced from 489 to 252 KVA • KVA Released - 237KVA (direct reduction) • Existing transformer of 1.7 MVA was supporting 0.97 MW load earlier Now, it can support 1.56 MW load, if Harmonics & PF are controlled.
  46. 46. Case Study-6 Software Development Company Sutherland Global Service, Chennai
  47. 47. Problems Experienced - Frequent failure of Electronic Boards in Servers and Work Station areas - Slow down of Network for reason unknown - Tripping of Generator - Distribution Transformer getting overheated Site Condition Installed Power = 640 KVA Generator Capacity = 300 KVA
  48. 48. Load Current and THDv (measured in UPS panel) Phases Load Current without AF3 Load Current with AF3 R 237 A 182 A Y 208 A 168 A B 187 A 150 A Phases VTHD without AF3 VTHD with AF3 R 7.8% 2.6% Y 8.3% 2.5% B 7.6% 2.5%
  49. 49. THDi (measured in UPS panel) Phases iTHD without AF3 iTHD with AF3 R 62% 12.7% Y 62.8% 14.5% B 64.8% 16.5%
  50. 50. Results ● Substantial KVA demand reductions up to 32.16 KVA ● Issues related with the noise, EMI and RFI in the facility was eliminated ● Failure of Electronic Boards in the Server stopped completely ● Generator and EB Transformer heating issues resolved ● Generator capacity requirement reduced to half
  51. 51. Critical Problems Solved ● Inoxpa India Limited, Pune – D G Hunting Problem and Maintenance Cost reduction ( AHF + TVSS + Detuned reactors + Earthing System Improvement ) ● Savings in the Diesel Consumption, Load running on Single DG Set and DG Hunting stopped. ● 80 % Electronic Component Failure reduction – reported by the Customer.
  52. 52. Critical Problems Solved ● Suprabha Industries Limited Lucknou. ● Load – Seam Welding, Co2 and Spot Welding ● Product – Fuel Tank, Silencers ● Problems – Power Factor, High KVAh consumption reported and Heavy Bills from EB. ● Solution – AHF + TVSS + Detuned Reactors + transformer ● Problem Solved and Adopting all solutions in the new plant during Project Level Itself. ● Tank Leakage/Rejection % reduced from 30 % to 10 % in the process due to improvement in the welding Quality.
  53. 53. Critical Problems Solved Vijayshree Industries Limited, Tata Nagar – Transformer Overheating and Power Factor Issue was there for 5 Years, PF Improved From 0.55 to 0.85 and Above. Issue Solved. (13 Km Feeder was separately allotted to the consumer by EB and Detuned Reactors Installed.) Electronic PCB Manufacturing Company, Pune – EB Meter Malfunctioning and Excess billing problem resolved, (EB - Meter Replacement ) Meter Mfg Company Modified the meter designs Suitable to work in the high harmonic environment in the year 2001.
  54. 54. Critical Problems Solved Upcoming Challenge 3 – FRP Composites Company, Product Quality Issue, Product Rejection Problem. Upcoming Challenge 1– Heavy Fabrication Industry – CNC Welding Machine Drive failure Problem Upcoming Challenge 2– CNC Machine Shop, More Component Rejection Problem Upcoming Challenge 4 – Pharma Company, Product Qty Weight Accuracy Issue, Product Rejection Problem.
  55. 55. Some of the Symptoms of Poor Power Quality 1 High Demand Charges 2 Power Factor Penalties 3 Unable to Maintain Good Power Factor 4 Computers Crashing 5 Computers Locking Up 6 Computers Memory Losses 7 Dropped Telephone Calls 8 Erratic Equipment Operation 9 Equipment Running Hot 10 Nuisance Tripping
  56. 56. Some of the Symptoms of Poor Power Quality 11 Lights Flickering 12 Motor Failures 13 Nuisance Tripping 14 Speed/Setting Drifting 15 Component Failures 16 Equipment Running Hot 17 Power Supply Failures 18 Surge Suppressor/UPS Failures 19 Circuit Board Failures 20 Overheating Transformers
  57. 57. Some of the Symptoms of Poor Power Quality 21 Overheating Wires/Conduit / Cables 22 Excessive Neutral Current 23 Disturbed/Wavy Audio-Visual Displays 24 Over-Heating Conductors/Switchboards 25 Persistent Fuse Blowing 26 Short Life of Lamps 27 Mains-Based Timing (clocks run fast) 28 Buzzing/Crackling Audio Systems 29 General Equipment Malfunction 30 Motor Start Problems
  58. 58. Some of the Symptoms of Poor Power Quality 31 Erratic control of process performance 32 Weight Accuracy Problem in the Process 33 Dimensional Accuracy Problem 34 More % of Rejection due to Power Issues 35 Hum Noise in the Breakers / Substation 36 Transformer Over Heating / Hum Noise 37 Corona Effect in the HT Lines 38 Life of Equipments is Low 39 Maintenance Cost is High 40 Fault Finding Cost and time is High
  59. 59. Some of the Symptoms of Poor Power Quality 40 Fault Finding Cost and time is High 41 Problems due to Unknown Reasons 42 Product production cost High due to Unknown Reason 43 Poor Product Quality due to Unknown Reason 44 Frequent Earth Faults 45 Contactor Coil Failure rate is High 46 Any Other Problem ( Unknown Reason )
  60. 60. 80 Thankyou

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