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Power Quality Fundamentals and Monitoring

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  1. Power Quality Fundamentals and Monitoring Ross M. Ignall Systems Applications Manager, Dranetz-BMI rignall@dranetz-bmi.com

  2. What We Will Cover… • Defining Power Quality and Reliability • PQ References & Fundamentals • Monitoring, Measuring High Reliability Facilities • Case Studies

  3. Power Monitoring Hardware Devices • measure and monitor power Data Acquisition Devices • measures physical processes Software andConsulting Services • power quality and distributed generation Aggregation of Distributed Generation • load curtailment of power sales WPT

  4. Defining Power Quality & Reliability

  5. 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.”

  6. What Does That Mean? Given the quality of supply do I have to worry about problems with my equipment or systems? It’s dependant on your susceptibility.

  7. What You Should Be Asking… What is my susceptibility to power problems? What is my economic exposure to such problems? $$$$

  8. Types Of Power Quality Problems

  9. Who’s Problem Is It? Customer’s Perspective* * Georgia Power Survey

  10. Who’s Problem Is It? Utility Perspective* * Georgia Power Survey

  11. The Big Picture It’s the complete electrical environment, not just the quality of supply

  12. What You Should Be Asking… Does my power system have the capacity for my present needs? How about future growth? Be Proactive!

  13. An Analogy… “Just because I have blank checks doesn’t mean that I have money in the bank to cash them”Ron Rainville, COO, US Data Centers

  14. Some Factoids

  15. Power Quality Factoids $50 billion per year in the USA is lost as a result of power quality breakdown.SOURCE: EPRI, 2000 Half of all computer problems and one-third of all data losscan be traced back to the power line.SOURCE: Contingency Planning Research, LAN TimesSandia National Laboratories estimates power quality and reliability problems cost US businesses approx.$150 billion annually in lost data, materials and productivity—60% are sagsIn 1999, the amount lost as a result of power quality in the US wasfive times the amount spent on power quality worldwide

  16. …The data center houses 45,000 square-feet of computer floor space. In one database, the company has consolidated $1.6 trillion of life insurance information.Energy Decisions, June 2001 During power supply shortages, utilities are generally permitted to have line voltage reductions, so-called “brown outs,” to cope with seasonal power demands…But if equipment is already operating on the low end of nominal voltage then the brown-out may cause excessive heat dissipation in motors and electronic equipment. Building Operation and Management, May 2000

  17. Power Density Factoids Traditional data center or large office building – 20-30 W/sq. ft.,Internet Data Center, on-line brokers, web hosts – 100-150 W/sq. ft.A web-enabled Palm Pilotrequires as much electricity as a refrigerator Mark MillsTransformation: Former 16 story Macy’s building used to consume 10 W/sq. ft.Now a telecommunications hotel that according to the utility could require 50 W/sq. ft. NY Times, July 3, 2000

  18. Costly Downtime! Industry Avg cost of downtime ($/hr)Brokerage $6,450,000 Credit Card $2,600,000 Pay Per View $150,000 Home Shopping $113,000 Catalog Sales $90,000 Airline Reservations $90,000 Tele-Ticket $69,000 Package Shipping $28,000 ATM Fees $14,400Source: 7x24 Exchange

  19. Introduction to Power Quality

  20. Power Grid Review GENERATOR 13.8kV-24kV L O A D DISTRIBUTION 34.5k-138kV 4k-34.5kV 12,470Y/7200V CONSUMER 4160Y/2400 480Y/277V 208Y/120V 240/120V TRANSMISSION 115k-765kV

  21. Generation • 50/60hz ‘Pure’ Sine Wave • Various Voltages • Types • Chemical • Mechanical • Nuclear • Solar

  22. Transmission • Those big towers • Voltage High • Current Small • Efficiency of Transmission Power Delivered to the Load Power Supplied From Generator

  23. Distribution • Typically 13kV • Commercial/Industrial - Three Phase, 480/277V • Residential - Split Phase 480V 480V 13kV 480V

  24. Single Phase Circuit Diagram L O A D Is V line Vn

  25. Can Wiring and Grounding Affect Power Quality? “That’s one of the things about living in an old house that drives me nuts. Never enough outlets!”

  26. ACTUAL SINGLE PHASE CIRCUIT DIAGRAM L O A D Is V line Vpcc Vdp L1 R1 L2 R2 I n1 l n2 Vn L3 R3 L4 R4 Vg L5 R5 L6 R6 I g2 l g1

  27. Sources Of Power Problems Referenced at the utility PCC (point of common coupling) • Utility • lightning, PF correction caps, faults, switching, other customers • Internal to the facility • individual load characteristics • wiring • changing loads

  28. Power Quality References & Terms

  29. IEEE Standards Coordinating Committee • SCC-22 • Oversees development of all PQ standards in the IEEE • Meet at both Summer and Winter Power Engineering Society meetings • Coordinate standards activities • Progress reports • Avoid overlap and conflicts • Sponsors task forces to develop standards • 1433 Task Force to pull together terms. IEEE & IEC

  30. IEEE Standard 1159-1995 Definition of Terms Monitoring Objectives Instruments Applications Thresholds Interpreting Results

  31. IEEE 1159 • 1159.x Task Force • Data Acquisition & Recorder Requirements for 1159-1995 • Combination of 1159.1 & 1159.2 • Coordination with IEC standards (61000-4-30 and revisions) • New recommended practice to be developed by July 2001 • 1159.3 Task Force • Power Quality Data Interchange Format (PQDIF) • Format for the exchange of PQ and other information between applications • Developed by Electrotek Concepts

  32. IEEE 519-1992 • Recommended Practice For Harmonics • Recommends Limits at the PCC • Voltage Harmonics • Current Harmonics • Ongoing work to modify IEEE 519-1992 • Limits for within a facility • Frequency dependant

  33. International Electrotechnical Commission (IEC) • International standards for all electrical, electronic and related technologies. • IEC Study Committee 77A – Electromagnetic Compatibility, presently 5 Working groups • SC77A/WG 1: Harmonics and other low-frequency disturbances • SC77A/WG 2 : Voltage fluctuations and other low-frequency disturbances • SC77A/WG 6 : Low frequency immunity tests • SC77A/WG 8: Electromagnetic interference related to the network frequency • SC77A/WG 9: Power Quality measurement methods

  34. Types Of Power Quality Disturbances (as per IEEE 1159) • Transients • RMS Variations • Short Duration Variations • Long Duration Variations • Sustained • Waveform Distortion • DC Offset • Harmonics • Interharmonics • Notching • Voltage Fluctuations • Power Frequency Variations

  35. Transient Characteristics • High frequency "event" • also called Spike, Impulse • Rise time (dv/dt) • Ring frequency • Point-on-wave • Relative versus Absolute amplitude • Multiple zero crossings

  36. Transients Unipolar Oscillatory Bipolar Notching Positive 200 100 0 -100 -200 Negative Multiple Zero Crossings

  37. Transients Possible Effects • Data corruption • Equipment damage • Data transmission errors • Intermittent equipment operation • Reduced equipment life • Irreproducible problems Possible Causes • PF cap energization • Lightning • Loose connection • Load or source switching • RF burst 

  38. Power Factor Correction Capacitor Transient 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

  39. RMS Voltage Variations • Instantaneous (0.5 - 30 cycles) • Sag (0.1 - 0.9 pu) • Swell (1.1 - 1.8 pu) • Momentary (30 cycles - 3 sec) • Interruption (< 0.1 pu, 0.5 cycles - 3s) • Sag • Swell • Temporary (3 sec - 1 minute)

  40. Swell Sag Interruption 200 150 100 50 0 -50 -100 -150 -200 RMS Voltage Variations

  41. SAGSOURCE GENERATED • DURATION • fault clearing schemes • may be series of sags (3-4) • MAGNITUDE • distance from source • feeder topology • cause • LOAD CURRENT • usually slightly higher, decrease, • or zero

  42. PQ Rule For a source generated Sag, the current usually decreases or goes to zero

  43. PQ Rule For a source generated Sag, the current usually decreases or goes to zero

  44. SAGLOAD GENERATED • DURATION • type & size of load • usually single event per device • MAGNITUDE • type & size of load • wiring & source impedance • LOAD CURRENT • usually significantly higher

  45. PQ Rule For a load generated Sag, the current usually increases significantly.

  46. Motor Starting- Another Cause of Sags

  47. Motor Starting– Inrush Current with decay

  48. SWELLS • Sudden change in load • Line-to-ground fault on another phase • Often precede a sag

  49. SWELLS when Load Drops Off

  50. Voltage Variations Sags/Swells Possible Causes • Sudden change in load current • Fault on feeder • Fault on parallel feeder Possible Effects • Process interruption • Data loss • Data transmission errors • PLC or computer misoperation • Damaged Product