Flicker

1. Flicker John Outram Outram Research Ltd Bosham,West Sussex (+44) 1243 573050 johnoutram@aol.com, www.outramresearch.co.uk 1

2. Outram Research LtdPM7000 PM2000 PM1000 SCOUT PM3000 PM6000 PRONTO

3. Flicker • What is it? • Is it important? • How is it caused? • Relevant Standards • How is it measured? • Can we do anything about it? • Examples 3

4. Flicker – What is it? • A perceptible change in light intensity • Generally caused by small fluctuations in voltage • Rarely harmful to electronic equipment • Nuisance - causing annoying, noticeable changes in lighting levels 4

5. Is it important? • Yes! • Second most common Power Quality problem • As well as being irritating - • Can cause Migraines, • Bring on epileptic fits

6. Its effect depends on • how often and how regularly the voltage fluctuates, • if rapid, the frequency of the flickering • how much of a voltage change occurs, • ambient light levels. 6

7. and also on • The kind of light • Incandescent • Fluorescent • HID - high intensity discharge • The gain factor of the lamp 7

8. Flicker - Early History • 1891 –Power Distribution Frequency chosen to prevent visible Flicker. • 1921 – Early research into human response (< 10 Hz) • 1925 – “GE Flicker Curve” from the 1921 research. • 1937 - Comprehensive study on human perception of flicker, validates GE Curve • 1950s – Fluorescent lights introduced – concern of “strobe” effects. • 1964 - Modified GE Flicker Curve => IEEE Standard 8

9. Organisations feeding IEC • UIE - The Union Internationale d’Electrotherme, • CIGRE - Conférence Internationale des Grands Réseaux Electriques à Haute Tension • CIRED - Congress International des Reseaux Electriques de Distribution • Significant cross fertilisation from BSI Nov 2, 2005 9

10. More recent history • 1980s – IEC working groups, leading to: • 1993 - EN60868 – Flickermeter, Evaluation of Flicker • 1994 - 61000-3-3 Flicker limits for low voltage eqpt < 16A • 1994 - 61000-3-5 Flicker limits for LV eqpt > 16A • 1996 - 61000-3-7 Flicker limits MV & HV systems (1kV to 230kV) • 1995 - EN50160 Public Supply Voltage characteristics • 1998 - IEC 61000-4-15 Flickermeter • 2005 - IEEE 1453 Flickermeter - as IEC61000-4-15 with extensions

11. Flicker Evaluation on a product(61000-3-3 < 16A)

12. Flicker - Terminology • Pu - Unit of perception. The average person just about sees 1.0 pu • Pst - Short term flicker “perceptibility”. The average person borders on irritation for a level of 1.0 • Measured over a short period, normally 10 minutes • Plt - Long term flicker “perceptibility”. Same scale as Pst • Measured over longer period, typ. 2 hours (12 Pst intervals) • Acceptable level is lower than for Pst • Pfs – Instantaneous Flicker Sensation 12

13. Flicker Nov 2, 2005 13

14. Flicker - causes • Electric arc furnaces • Induction motors w/high inrush currents (high efficiency AC units) • Arc-welders, spot-welders • Wind turbine generators • Ovens • Malfunctioning power electronics • Any large-draw varying load! 14

15. Flicker - Impact • Worse closer you are to offensive load • Worse on weak (high impedance) systems • Larger offensive loads cause more flicker • Made worse by: • High gain factor lighting • Lower-inertia lighting • Dimmers (maybe) 15

16. Flicker Low Voltage, Medium Voltage, < 132 kV High Voltage, > 132kV Pst < 1.0 < 0.8 Plt < 0.8 < 0.6 Typical Working Levels on the Network < 0.1 Pst is rare. 16

17. Pst evaluation for multiple motor starts Nov 2, 2005 17

18. IEC Flickermeter Nov 2, 2005 18

19. PM7000 <=====Ranger PQ products, measurement options

20. Statistical processor

21. Flicker – final calculations used in IEC modelP0.1is flicker level exceeded for 0.1% of the time, etc. 21

22. IEC Flickermeter Nov 2, 2005 22

23. Plt calculation – when? Nov 2, 2005 23

24. Mitigation Depends on the source of the problem Good News!! 90% of problems are neutral related, or involve poor joints, and some are just unfortunate configurations

25. Mitigation Not so good news 10% are serious, and probably expensive, caused by heavy industrial plant • Change feed to offending plant • Run new feed to sensitive site • Invest in distribution infrastructure

26. S & C Electric Company • STATCOM – Static Synchronous Compensator • Adaptive VAR Compensator (Switched capacitor - ½ cycle response)

27. American Superconductor • SuperVAR Dynamic Synchronous Condenser • Flicker mitigation – Steel mills, mines, arc furnaces. • Reactive compensation, Dynamic Power Factor correction

28. Best Characteristics • Response time 1/4 cycle, though switches can operate faster • Reactive power range up to +/- 150Mvar • Shunt connection at 450V to 400kV • Minimal harmonics, no special filtering 28

29. Example 1 - Oops!

30. Oops!

31. Oops!

32. Example 2 - Significance of Rate

33. Example 3 33

34. High Flicker levels not obvious from Voltage 34

35. Diagnose from Instantaneous Flicker and Current 35

36. Pfs & Current unrelated 36

37. 2 mins – after midnight 37

38. Zoomed to 2 secs ½ cycle of 6 Hz Nearly worst case 38

39. Flicker John Outram Outram Research Ltd www.outramresearch.co.uk 39