“Power Quality”

1. Presentation on “Power Quality” Mr. P B Tupe

2. Presentation Sections What is Power Quality? Why Monitor Power Quality? Power Quality components European Standard EN50160 IEC 61000 Standard What should we demand from a PQM?

3. What is Power Quality? Steady-state disturbance Transient disturbance

4. What is Power Quality? IEEE ..the concept of powering and grounding sensitive electronic equipment in a manner suitable for the equipment LPQI (Leonardo Power Quality Initiative) ..a supply that is always available, always within voltage and frequency tolerance, with a pure, noise free, sinusoidal wave shape Sankaran (modified) ..a set of boundaries that allow electrical appliances and systems to function as intended without significant loss of lifetime or performance

5. A Brief History of Power Quality… 1879 1891 1917 1948 2006 First report on flicker Increased use of power electronics Shockley, Bardeen and Brittain invents the first transistor Thomas Alva Edisoninvents the light bulb Jonas Wenströminvents the three-phase system Mostly linear loads Increase in non-linear loads

6. Why Monitor Power Quality? The Cost of (poor) Power Quality: • Production losses • Extended outage time • Shortened equipment lifetime e.g. Transformer • Unexpected early failure • Overloading of equipment • Potential catastrophic failure • Chain reaction

7. Why Monitor Power Quality? According to a study performed by European Copper Institute in 2001, covering 1,400 sites in 8 countries, any given site in Europe has a 5-20 % probability that it will suffer from one or more of the problems listed. Typically, half of sites in energy-intensive industries or mission-critical office buildings will suffer from two or more problems

8. Why Monitor Power Quality? • Estimation of annual cost of poor PQ in Europe 10 billion EUR Power quality problems have increased since 2001 due to more sensitive equipment and more non-linear loads. • Typical losses in some industries due to poor PQ (2001) Semiconductor production EUR 3 800 000 Financial trading (per hr!) EUR 6 000 000 Computer centre EUR 750 000 Telecommunications (per min!) EUR 30 000 Steel works EUR 350 000 Glass industry EUR 250 000 Ref : Copper Development Association’s booklet 2001

9. Power Factor Description / Causes: Phase angle between voltage and current. Caused by capacitive or inductive loads such as: • Motors • Long power lines. Costs: Consequences: • Inefficient use of grid • Overheating • Losses • Network must be designed for higher currents

10. Supply voltage variations Description / Causes: Slow variations in the RMS. Caused by: • Changing loads • Tap changes on transformers Costs: Consequences: • Reduced life time of equipment • Production losses • Damage to equipment • Production losses • Reduced life time of equipment

11. Harmonics Description / Causes: Non-linear loads cause distorsion that causes other (higher) frequencies in the network. Caused by: • Switched power supplies (computers), Power electronics, Motor drives Consequences: Costs: • Increased losses. Overheating of neutral conductor and transformers • Resonance phenomena resulting in high currents and voltages. Broken capacitor banks. • Malfunction in control equipment • Production losses • Reduced life span of the equipment • Increased investments in filters and compensating equipment

12. Flicker Description / Causes: Cyclic variations in the voltage RMS. Variations in the range 0-30 Hz. Caused by: • Welding equipment • Rolling mills • Arc-furnaces Costs: Consequences: • Blinking lights that irritate and tire the eye and cause headaches • Indirect costs like reduced productivity • Often expensive solutions

13. Voltage unbalance Description / Causes: Amplitude and/or phase varies between the three phases. Caused by: • Uneven distribution of single-phase loads • Trains Consequences: Costs: • Loss of efficiency in 3 Ph motors • Corrosion and increased current in neutral conductors. • Stray currents in grounding system • Reduced life span of the equipment • Motor power cannot be fully utilised

14. Transients Description / Causes: Rapid and short (sub-cycle) changes in the voltage or current waveforms. Caused by: • Lightning • Faults and switching in the grid • Start of engines Costs: Consequences: • Tripping of protective equipment • Faults/damages in electronics such as computers or control systems for machines • Production loss • Failure or damage to equipment • Loss of information (computers)

15. Sags (dips) / Swells Description / Causes: Short variations in voltage RMS. Caused by: • Lightning • Faults and switching in the grid • Start of engines, rolling mills, welding sets Consequences: • Flicker • Disturbances in electronic equipment such as computers or control systems for machinery • Swells can destroy equipment (overvoltages) Costs: • Production losses • Loss of information in computers

16. Rapid Voltage Changes Description / Causes: Fast but small (<10%) variations in the voltage RMS. Caused by: • Connection/disconnection of loads • Tap changes on transformers Consequences: • Flicker Costs: • Indirect costs such as reduced productivity

17. Power (Poor) Quality

18. Two categories of PQ standards Voltage characteristics standards • EN 50 160 (EU standard) • IEC 61000-2-2 (LV), -12 (MV) • Norma Peruana (Peru) • Victorian Distribution Code (Australia) • Philippine Grid Code • Venezuelan Grid Code • Chinese standards Measurement methods standards • IEC 61000-4-7 (harmonics) • IEC 61000-4-15 (flicker) • IEC 61000-4-30 (methods)

19. European Standard EN50160 Voltage characteristics for electricity supplied by public distribution systems • Main characteristics of voltage at customer’s supply terminals • Public low-voltage and medium-voltage networks • Describes what is expected under normal operating conditions

20. EN50160 - Voltage variations Voltage magnitude: 95% of the 10-minute averages during one week shall be within 10% of the declared voltage of 230 V.All values shall be between -15% and +10%. Frequency: 99.5% of the 10-second averages during one yearshall be between 49.5 and 50.5 Hz. The frequency shall be between 47 and 52% for 100% of the time. Voltage unbalance: 95% of the 10-minute averages during one week shall be less than 0.02. Voltage fluctuations: 95% of the 2-hour long-term flicker severity values during one week shall not exceed 1.0.

21. EN50160 - Voltage variations (2) Voltage harmonics: 95% of the 10-minute averages during one week shall not exceed the values given in the table below Note: As for all other characteristics these values hold for 99.9% of the locations during 95% of time

22. European Standard EN50160 – in short

24. IEC 61000-4-30 Scope • Focused on parameters causingconductedphenomena • Describes measurementmethods – notthresholds or limits Describes measurement methods which will give reliable, repeatable and comparable results - regardless of the instrument being used

25. IEC 61000-4-30 PQ Parameters Detailed specification of measurement methods and accuracy for: • Power frequency • Voltage RMS • Flicker • Harmonics and interharmonics • Unbalance • Dips, swells, interruptions and transients • Mains Signalling

26. IEC 61000-4-30 Class A – Normative • High accuracy • Standards compliant • Contractual verification • Comparable results Class B – Indicative • Lower accuracy • May not meet all standards • Demand analysis • Results vary with instrument

27. IEC 61000-4-30 Flagging Concept When a single event such as a voltage DIP etc. occurs, the actual measurement interval shall be flagged and other parameters should be discarded during that interval to avoid counting the event more than once. New method !

28. Voltage RMS value T The RMS value is calculated from every 10-cycle value without time gaps. Other measurement intervals can be calculated based on 10-cycle values. Accuracy 0.1% of nominal voltage.

29. Performance specification, not a design specification ! ½ Cycle RMS values = 10ms (for DIPS detection) Measurement Aggregation time interval: 10 Cycles = 200ms 150 Cycles = 3s 10min Values are calc from 10 cycle values 2Hr Value = aggregated from 12 x 10min values Class A devices - tested thoroughly as per guidelines Class B devices – Liberty to manf to specify the methods and accuracies Results of 2 Class A devices an be compared.

30. Sliding reference Nominal levels might vary over time, especially on medium and high voltage. Threshold values must therefore always follow the actual reference level. This is called sliding reference since reference level is always average voltage last minute. Sliding Reference

31. IEC 61000-4-30 Summary • IEC 61000-4-30 provides standardised measurement methods • IEC 61000-4-30 guarantees comparable results between normative instruments • IEC 61000-4-30 guarantees users to have full knowledge about the instrument performance • IEC 61000-4-30 helps manufacturers of PQ instruments to implement standardised methods and algorithms • IEC 61000-4-30 is an essential document when developing new PQ standards

32. What should we demand from a power quality monitoring system? • Accurate and reliable measurement • Measure both voltage and current for disturbance tracking • IEC 61000-4-30 Class A instrument • Combination of permanent and portable instruments for full control of the whole network • Portable unit suitable for field use: IP65 • Designed for power quality monitoring: • Remote communication solutions for both permanent and portable instruments • Automated features: user defined limits, alarms etc • Give statistical information: data stored for years, not just months

33. Reference • IEC/ EN Standards • Web sites / Product catlogues – Unipower ,Yokogawa, Fluke, GE, Areva, a-eberle, Megger, ABB, Siemens etc. • www. Lpqi.com (Leonardo Power Quality Initiative) • Copper Development Association’s Reports