Introduction to Power Quality


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Introduction to Power Quality
by Dranetz-BMI

Introduction to Power Quality

  1. 1. Power Quality, Reliability and Management
  2. 2. What is a Power Quality Problem ? “ Any occurrence manifested in voltage, current, or frequency deviations that results in failure or mis-operation of end-use equipment.” Dictionary
  3. 3. What does that mean? It’s dependant on your susceptibility. Given the quality of supply do I have to worry about problems with my equipment or systems?
  4. 4. Typical Financial Loss Per Event Source: The Cost of Power Quality, Copper Development Association, March, 2001 Industry Typical Loss Financial $6,000,000/event Semi-conductor mfg. $3,800,000/event Computer operations $750,000/event Telecommunications $30,000/minute Data processing $10,000/minute Steel/heavy mfg. $300,000/event Plastics $10,000-15,000/event
  5. 5. Sources Of Power Problems <ul><li>Referenced at the utility PCC (point of common coupling) </li></ul><ul><li>Utility </li></ul><ul><ul><li>lightning, PF correction caps, faults, switching </li></ul></ul><ul><ul><li>impact from other customers </li></ul></ul><ul><li>Internal to the facility </li></ul><ul><ul><li>individual load characteristics, motors, ASDs </li></ul></ul><ul><ul><li>computers, microprocessors </li></ul></ul><ul><ul><li>wiring </li></ul></ul><ul><ul><li>changing loads </li></ul></ul>Typically, 70% of all PQ events are generated within the facility
  6. 6. Types Of Power Quality Disturbances (per IEEE 1159) <ul><li>Transients </li></ul><ul><li>RMS Variations </li></ul><ul><ul><li>Short Duration Variations </li></ul></ul><ul><ul><li>Long Duration Variations </li></ul></ul><ul><ul><li>Sustained </li></ul></ul><ul><li>Waveform Distortion </li></ul><ul><ul><li>DC Offset </li></ul></ul><ul><ul><li>Harmonics </li></ul></ul><ul><ul><li>Interharmonics </li></ul></ul><ul><ul><li>Notching </li></ul></ul><ul><li>Voltage Fluctuations </li></ul><ul><li>Power Frequency Variations </li></ul>
  7. 7. Types of Power Quality Problems
  8. 8. What is a Transient? <ul><li>Momentary (& undesirable) high frequency sub-cycle “event” </li></ul><ul><li>Usually measured in microseconds </li></ul><ul><li>May also be called a Spike, Surge or Impulse </li></ul><ul><li>Characteristics of a Transient: </li></ul><ul><ul><li>Rise time (dv/dt) </li></ul></ul><ul><ul><li>Ring frequency </li></ul></ul><ul><ul><li>Point-on-wave </li></ul></ul><ul><ul><li>Multiple zero crossings </li></ul></ul><ul><ul><li>Magnitude </li></ul></ul>
  9. 9. Transients -200 -100 0 100 200 Unipolar Positive Negative Notching Oscillatory Multiple Zero Crossings Bipolar
  10. 10. A transient power quality event has occurred on DataNode H09_5530. The event occurred at 10-16-2001 05:03:36 on phase A. Characteristics were Mag = 478.V (1.22pu), Max Deviation (Peak-to-Peak) = 271.V (0.69pu), Dur = 0.006 s (0.35 cyc.), Frequency = 1,568. Hz, Category = 3 Upstream Capacitor Switching
  11. 11. Possible Causes • PF cap energization • Lightning • Loose connection • Load or source switching • RF burst  Possible Effects • Data corruption • Equipment damage • Data transmission errors • Intermittent equipment operation • Reduced equipment life • Irreproducible problems Transients
  12. 12. What is an RMS Variation? (longer duration events) <ul><li>A change in the RMS voltage. Typically 16 ms (1 cycle) or longer </li></ul><ul><li>Reduction in voltage: Sag or Interruption </li></ul><ul><li>Increase in voltage: Swell </li></ul>
  13. 13. RMS Voltage Variations 100 -100 0 Sag Swell Interruption
  14. 14. Motor Starting
  15. 15. IEEE1159 Characterizations (RMS Variations) <ul><li>Instantaneous (0.5 - 30 cycles) </li></ul><ul><ul><li>Sag (0.1 - 0.9 pu) </li></ul></ul><ul><ul><li>Swell (1.1 - 1.8 pu) </li></ul></ul><ul><li>Momentary (30 cycles - 3 sec) </li></ul><ul><ul><li>Interruption (< 0.1 pu, 0.5 cycles - 3s) </li></ul></ul><ul><ul><li>Sag </li></ul></ul><ul><ul><li>Swell </li></ul></ul><ul><li>Temporary (3 sec - 1 minute) </li></ul><ul><li>Long Duration (beyond 1 minute) </li></ul>
  16. 16. What is Directivity? <ul><li>Where the problem originated referenced to the point being monitored (where the instrument is) </li></ul><ul><li>Typically referred to as “Upstream” or “Downstream” </li></ul><ul><li>Upstream </li></ul><ul><ul><li>Source side . Originated from the source of supply (can be utility) </li></ul></ul><ul><li>Downstream </li></ul><ul><ul><li>Load side . Originated from a load </li></ul></ul><ul><li>Helps you identify where the problem is and what actions to take. </li></ul>
  17. 17. Case Study – Major Financial Institution (Benefits of Learning Directivity) <ul><li>Problem – Utility Sag </li></ul><ul><li>Damaged elevator controls </li></ul><ul><li>No UPS alarms (2 static, 1 rotary) </li></ul><ul><li>No reported problems with critical systems </li></ul>02/19/2002 00:29:29.26 PM Module Input Temporary Sag Rms Voltage AB Mag = 366.V (0.76pu), Dur = 3.300 s, Category = 2, Upstream Sag 02/19/2002 00:29:29.26 SYSA Input Temporary Sag Rms Voltage AB Mag = 353.V (0.73pu), Dur = 3.300 s, Category = 2, Upstream Sag 02/19/2002 00:29:29.26 SYSB Input Temporary Sag Rms Voltage AB Mag = 372.V (0.78pu), Dur = 3.300 s, Category = 2, Upstream Sag
  18. 18. Utility Sag Utility Supply RMS Trend Utility Supply Waveforms
  19. 19. Corresponding UPS Swell Utility Supply UPS Output UPS Swell
  20. 20. Conclusion <ul><li>Utility sags damaged elevator controls </li></ul><ul><li>Corresponding UPS Swell coincident with utility return to normal </li></ul><ul><li>Cause of swell being investigated by manufacturer </li></ul><ul><li>Possible effects of swells” </li></ul><ul><ul><li>Damaged power supplies and other devices </li></ul></ul>Without monitoring, the customer would be unaware of the UPS problem. The next time, the damage could be worse
  21. 21. PQ Rule #1 <ul><li>For a source generated Sag, the current usually decreases or goes to zero </li></ul>
  22. 22. August 14, 2003 Blackout: Long Duration Interruption
  23. 23. PQ Rule #2 <ul><li>For a load generated Sag, the current usually increases significantly. </li></ul>
  24. 24.  Possible Causes • Sudden change in load current • Fault on feeder • Fault on parallel feeder • Motor start • Undersized distribution system Possible Effects • Process interruption • Data loss • Data transmission errors • PLC or computer misoperation • Damaged product • Motor failure RMS Voltage Variations Causes and Effects
  25. 25. <ul><li>Common RMS Voltage Variations </li></ul><ul><li>Visualization methods using power monitoring instrumentation </li></ul><ul><ul><li>Sampled data </li></ul></ul><ul><ul><ul><li>Recorded Waveforms </li></ul></ul></ul><ul><ul><li>Magnitude vs. Time </li></ul></ul><ul><ul><ul><li>Timelines </li></ul></ul></ul><ul><ul><li>Magnitude vs. Event Duration </li></ul></ul><ul><ul><ul><li>CBEMA (IEEE 446) </li></ul></ul></ul><ul><ul><ul><li>ITIC </li></ul></ul></ul><ul><ul><ul><li>3-D Mag-Dur </li></ul></ul></ul><ul><ul><li>Equipment susceptibility curves </li></ul></ul><ul><ul><ul><li>Custom curves that represent that specific device </li></ul></ul></ul>
  26. 26. IEEE 446 - 1995 Limits (CBEMA)
  27. 27. Information Technology Industry Council (ITIC) Curve
  28. 28. Another Perspective – 3D Mag-Dur Histogram
  29. 29. <ul><li>( Laser Printer Heating Cycle) </li></ul>Case Study
  30. 30. Voltage Timeline Vl-n= 120 --> 108 45 seconds
  31. 31. SAG when heater turns on V l-n I load
  32. 32. Overlay Voltage & Current - Heater turning on
  33. 33. An integer multiple of the fundamental frequency Fundamental (1 st harmonic) = 60hz 2 nd = 120hz 3 rd = 180hz 4 th = 240hz 5 th = 300hz … What is a harmonic?
  34. 34. Linear Voltage / Current No Harmonic Content voltage current
  35. 35. Non-Linear Voltage / Current Harmonic Content voltage current
  36. 36. <ul><li>When should I be concerned about Harmonics? </li></ul><ul><li>Harmonics are typically considered a problem when they are always present…Steady state distortion that is continuously occurring. </li></ul><ul><li>Although any waveform can have harmonics we are typically concerned with the cumulative effects of continual harmonic distortion on the power system </li></ul>
  37. 37. How are harmonics measured? <ul><li>Individual Harmonics </li></ul><ul><ul><li>2, 3, 4, 5, 6…50+ </li></ul></ul><ul><ul><li>Fourier Transform, FFT, DFT </li></ul></ul><ul><li>Total Harmonic Distortion (THD) </li></ul><ul><ul><li>Ratio, expressed as % of sum of all harmonics to: </li></ul></ul><ul><ul><ul><li>Fundamental (THD) </li></ul></ul></ul><ul><ul><ul><li>Total RMS </li></ul></ul></ul><ul><ul><ul><li>Load Current (I TDD only) </li></ul></ul></ul><ul><li>Interharmonics </li></ul><ul><ul><li>Content between integer harmonics </li></ul></ul><ul><ul><li>Required for new IEC standards (IEC 61000-4-30) </li></ul></ul>
  38. 38. Harmonic Spectrum
  39. 39. PQ Rule #3 <ul><li>Even harmonics typically do not appear in a properly operating power system . </li></ul><ul><li>Symmetry </li></ul><ul><li>Positive & Negative halves the same: Only odd harmonics. </li></ul><ul><li>If they are different: Even & Odd harmonics </li></ul>
  40. 40. <ul><li>What are Triplen Harmonics? </li></ul><ul><li>Harmonics who’s order is a multiple of 3 </li></ul><ul><ul><li>3, 6, 9, … </li></ul></ul><ul><li>Why should I be concerned about Triplen Harmonics? </li></ul><ul><li>Triplen Harmonics add in the neutral. </li></ul>
  41. 41. Additive Triplen Harmonics
  42. 42. Harmonics (sustained) Possible Effects • Overload of neutral conductors • Overload of power sources • Low power factor • Reduced ride-through Possible Causes • Rectified inputs of power supplies • Non-symmetrical current • Intermittent electrical noise from loose connections 
  43. 43. <ul><li>( Laser Printer Heating Cycle) </li></ul><ul><li>Continued… </li></ul>Case Study
  44. 44. Current Waveform - heater on
  45. 45. HARMONIC DISTORTION - heater on Ithd = 5% Harmonics V l-n Harmonics I load Vthd = 2.8%
  46. 46. Current With Printer Idle
  47. 47. Harmonic Distortion - Idle Ithd = 140% Harmonics V l-n Harmonics I load Vthd = 3.1%
  48. 48. Review of What We Just Saw <ul><li>Nearly Sinusoidal Current </li></ul><ul><ul><li>Low Voltage Harmonic Distortion (4%) </li></ul></ul><ul><li>Voltage and Current In-phase </li></ul><ul><ul><li>Power Factor Near One </li></ul></ul><ul><li>Flat-topping of Voltage when Idle </li></ul><ul><ul><li>Corresponds with Current Pulse </li></ul></ul>
  49. 49. Other PQ Concerns (defined in IEEE 1159) <ul><li>Frequency </li></ul><ul><ul><li>Frequency different from the ideal 50/60hz </li></ul></ul><ul><ul><li>Frequency not synchronized with the grid </li></ul></ul><ul><li>Unbalance </li></ul><ul><ul><li>Deviation from the average 3 phase voltage (IEEE) </li></ul></ul><ul><li>Voltage Fluctuations (Flicker) </li></ul><ul><ul><li>Small changes to the magnitude of the voltage </li></ul></ul><ul><ul><li>Visual perception. Effects on lights </li></ul></ul>
  50. 50. How Many Can You Find?
  51. 51. Monitoring Approaches and Tools <ul><li>Handheld/Portable </li></ul><ul><li>(Reactive) Vs. Permanently Installed (Proactive) </li></ul>
  52. 52. Reactive Monitoring <ul><li>After the fact - Reactive </li></ul><ul><li>Forensic approach </li></ul><ul><li>Problem Solving, Hopefully you’ll find it! </li></ul><ul><li>Portable instrumentation typically used </li></ul>
  53. 53. Proactive Monitoring <ul><li>Permanently installed monitoring systems </li></ul><ul><li>Anticipate the future, On-Line when trouble occurs </li></ul><ul><li>Monitor system dynamics </li></ul><ul><li>Preventive Maintenance, Trending, identify </li></ul><ul><li>equipment deterioration </li></ul><ul><li>Power Quality and Flow </li></ul>
  54. 54. Monitoring Solutions From Dranetz-BMI Portable/Handheld Permanently Installed Get the right tool for the job!
  55. 55. Capabilities Handheld Family
  56. 56. PowerXplorer PX5 PowerGuide 4400 New Products!
  57. 57. <ul><ul><li>8 Channels </li></ul></ul><ul><ul><ul><li>4 Differential Voltage, AC/DC </li></ul></ul></ul><ul><ul><ul><li>4 Current, AC/DC </li></ul></ul></ul><ul><ul><li>256 Samples Per Cycle </li></ul></ul><ul><ul><li>50/60HZ, 16/20HZ (railroad) </li></ul></ul><ul><ul><li>Harmonics to the 63 rd </li></ul></ul><ul><ul><li>Flicker </li></ul></ul><ul><ul><li>Low Freq Transients (up to 5KHZ) </li></ul></ul><ul><ul><li>Medium Freq Transients (5-10KHZ) </li></ul></ul><ul><ul><li>Ethernet, USB, serial commun. </li></ul></ul>PowerGuide 4400 Color touch screen Unique annunciator
  58. 58. <ul><li>Applications </li></ul><ul><ul><li>Inrush </li></ul></ul><ul><ul><li>Fault Recorder </li></ul></ul><ul><ul><li>Motor Testing </li></ul></ul><ul><ul><li>Power Studies </li></ul></ul><ul><ul><li>System Commissioning/compatibility </li></ul></ul><ul><ul><li>Telecommunications </li></ul></ul><ul><ul><li>General Troubleshooting </li></ul></ul><ul><ul><li>Compliance </li></ul></ul>PowerGuide 4400
  59. 59. <ul><li>Advanced Power Quality Analysis </li></ul><ul><li>Includes all PowerGuide 4400 Features </li></ul><ul><li>High Speed (658/8800 like) Digitized Transients </li></ul><ul><li>Advanced Power Analysis </li></ul><ul><ul><li>IEEE1459 </li></ul></ul><ul><li>PX5-400 – 400HZ Option </li></ul>PowerXplorer PX-5
  60. 60. <ul><li>Applications </li></ul><ul><ul><li>All PowerGuide 4400 Plus… </li></ul></ul><ul><ul><li>Medical Diagnostic Equipment </li></ul></ul><ul><ul><li>Advanced PQ Surveys </li></ul></ul><ul><ul><li>400HZ Aircraft, Naval, Military </li></ul></ul><ul><ul><li>Utility Surveys </li></ul></ul><ul><ul><li>Any 658 or 8800 application </li></ul></ul>PowerXplorer PX-5
  61. 62. Data to ... ... Information to ... ... Answers Advanced Visualization
  62. 63. Thank You! Questions? Dranetz-BMI 1000 New Durham Rd. Edison, NJ 08818 1800-372-6832