INTRODUCTION

1. INTRODUCTION Bert van Bruchem

2. Program • Power Quality intro • Application examples: • Applications • Technical background Break. • Products: • Features (HW/SW) • Value selling aspects

3. 1. Power Quality introWhat is power quality? Power Quality is a measure of how well a system supports reliable operation of its loads. A power disturbance or eventcan involve voltage, current, or frequency. • Power disturbances are defined in terms of magnitudeand duration. • Disturbances range from transients to outages • When a power disturbance falls outside operating limits, equipment may be disrupted or damaged.

4. 1. Power Quality introHow to deal with PQ.

5. 1. Power Quality introCommon power disturbances Symptoms • Power outages • Tripping circuit breakers and ASDs • High utility bills • Flickering lights • Equipment running noisy and hot • Premature equipment failure • Poor performance & unexpected shutdowns • Lost data in electronics Causes • Voltage dips & swells • Transients • Noise interference • Harmonic distortion • Under / over voltage or current • Voltage unbalance

6. 1. Power Quality introCauses of disturbances • Internal causes: Approximately 80% of electrical disturbances originate within a business facility. • External causes: About 20% of power quality problems originate with the utility transmission and distribution system.

7. 1. Power Quality intro Inside the building • Typical facility problems: • Loose connections • Arcing connections • Overloaded circuits and transformers • Unbalanced loads • Harmonics caused by modern electronics • Illegal neutral to ground bonds • Ground loops • Undersized or shared neutrals

8. 1. Power Quality intro Utility generation & transmission • Typical utility problems • Fuses opening • Protective relays and circuit breakers operating • Power factor correction switching • Grid switching • “Reclosers” • Equipment arcing or failure • Downed lines (outage) • Excessive demand (undervoltage, “brownout”) Example: When reclosers operate repeatedly to try to burn off tree branches or squirrels it causes repetitive voltage sags as seen here.

9. 1. Power Quality intro Types of PQ work • Troubleshooting • Quality of service studies • Comprehensive PQ studies • Load studies • Commissioning

10. 1. Power Quality introPQ Customer segmentation Electricians or maintenance technicians whose primary responsibility is to maintain and troubleshoot the electrical system in their Industrial or Commercial facility Reduce downtime, Respond to internal complaints / RCM Utility refers to the distribution division that delivers power from the Hi-V transmission substations to the consumer.Two groups within distribution do PQ -Repairman (emergency crew) and Power Quality team RCM / respond to external complaints, Quality control Technicians responsible for installing, servicing, and repairing large equipment that is installed in a 3rd party facilityGE Healthcare, Otis Elevator, MGECommissioning, system check, respond to cust. complaints Firms that perform large electrical projects for facilities that may include either installation or service: Installers – run wire, install transformers and switchgear, etc Service – similar to Field Service, troubleshoot equipment problems at customer sitesCommissioning, apply to cust. demands

11. Power Quality introWe differentiate between the following basic PQ applications: • Monitoring Quality of supply • Disturbance analysis • Network optimization • Predictive maintenance

12. Power Quality intro The benefits of Power Quality Monitoring ? • Knowledge about real Power Quality levels and trends (meet the regulators needs) • Planning data for investments • Monitor emissions from industrial customers etc. • Optimise and monitor contracts with supplier or consumer. • Supports optimisation of electric network • Monitor performance of protection devices.

13. 1. Power Quality intro The benefits of Disturbance analysis. • Prevent similar disturbances • Reduce downtime • Competence and speed when dealing with customer complaints • Monitor performance of protection devices. • Improve maintenance

14. Power Quality intro The contribution towards Network Optimisation. • Prevent overloading • Improve balancing of loads • See trends • Monitor performance of compensating systems • Reduce energy bill

15. Power Quality introSupporting Predictive maintenance • Detect and anticipate • Check the critical parameters of motors • Find the cause of dips / swells • Monitor harmonic levels • Locate the cause of hot spots • ….

16. 2. Application examples • “A bad reaction at the chemical plant” • Voltage unbalance • Voltage distortion and harmonics • Power system resonance • “Dips on the ski slopes” • Voltage dips • Flicker • “Gusty power at the wind farm” • Transients • “ Wasted power at the wastewater plant” • Energy consumption • Power factor

17. Bad reaction at the chemical plant

18. Chemical Plant: scenario • During a PdM procedure, a technician finds hot across-the-line pump motors using a Thermal Imager • The feeders for the motors supplied both motor starters and newer drives The plant has been phasing out the older electromagnetic starters • No new motors or loads had been added Proactive maintenance and testing at a chemical plant uncover a problematic legacy

19. Chemical Plant: PQ analysis • Maintenance tech uses a Fluke 434 PQ Analyzer on the motor terminals and sees unbalanceis within limits. • Tech measures voltage distortion and notes that 5th harmonic is high. Voltage distortion is 14 %. • He determines an old PF correction cap had been switched in by mistake. The capacitor had been installed when all of the motors used soft starts. It had never been decommissioned! • The capacitor caused resonance at approximately the 5th harmonic. Capacitor removed, problem solved!

20. Lessons and questions • Lessons • Electrical issues than can cause motor overheating: • Voltage unbalance • Overcurrent • Current unbalance (e.g. single phasing) • Voltage distortion • Combining across-the-line motors and motor drives on the same feeders can cause distorted voltage • Capacitors can turn harmless harmonic current into a problem • Questions • Why did the electrician check voltage balance? • What are harmonics and why are they important? • What made the 5th harmonic so high?

21. Why is unbalance important? • Voltage unbalance causes inefficiency in a 3-phase system. • To maintain voltage balance, each phase should draw approximately equal current. • Voltage unbalance causes current to flow in the neutral in wye systems. • Motors do not like to see more than 5 % voltage unbalance Unbalanced loading Unbalanced current Unbalanced voltage

22. Harmonics and distortion • Consequences of harmonics : rotation • Each harmonic has its own rotation: Harmonic order 7 1 2 3 6 4 5 100 Hz 50 Hz 150 Hz 200 Hz 250 Hz 350 Hz 300 Hz Frequency - + - + 0 0 + Rotation

23. Distorted waveforms Harmonic frequencies combine with the fundamental to form distorted voltage or current waveforms Total Harmonic Distortion (THD) expresses contribution of all harmonics a) A 212 A rms sine wave at the fundamental frequency b) A 28 A rms sine wave at the 3rd harmonic Combination of (a) and (b) resulting in a distorted waveshape A spectrum display shows a breakdown of the components

24. Voltage distortion on motors • General: Higher frequencies cause heating due to eddy currents and skin effect • 3th Harmonic causes neutral current • 5th harmonic causes counter-torque • Harmonics can cause reonance Less than 5 % voltage THD desired

25. 3th harmonic

26. 5th harmonic

27. Power system resonance In this case the 5th harmonic was close to the resonance freq so causing the problem

28. The resonance dilemma ….Solutions: • Remove PF correction capacitors - need may be reduced since today’s ASD’s have/cause high DPF • Use capacitor systems designed for use with harmonic loads. • Active filters can improve DPF and substantially reduce harmonics Remember!: motor windings + PF cap’s can mean resonance! How can I improve PF without creating a harmonics problem?.........

29. Dips on the ski slopes

30. Ski Café: The problem • Restaurant patrons at a ski resort complain the lights are flickering • Electrical contractor comes but voltage on DMM is OKE • Local utilitys is contacted, they connect a Fluke 1740 at the point of common coupling • The point of common coupling is at the bottom of the ski hill!

31. Ski Café: initial measurements • The Fluke 1740 Recorder : • some small voltage dips of a volt or two • No significant flicker • large current increases with the dips. • So, no problem for the Utility • The local contractor returns, with a Fluke 434.

32. Ski Café: tracing the problem 1 2 3

33. Ski Café: solution • The new deep fryer was allready installed over the summer. No one noticed the light problem during the summer, when daylight masked the problem. • The problem was due to the long feeders between the main switchgear • A separate feeder was installed for the fryer. Problem solved.

34. Lessons and key questions Lessons • Long or undersized wiring can contribute to voltage dips • Power recording can help zero in on the load causing the dips. Finding the culprit with the Fluke 345, 434, 1735. Questions • Why did running additional wiring solve the problem? • How did the electrician know where the problem was? • Restaurant customers complained that the lights were “flickering” but was this what PQ professionals call “flicker”?

35. What causes low voltage? • Too much system impedance and… • Too much load current What causes low voltage? A voltage dip is simply an incidence of low voltage that occurs over a period of ½ cycle to 1 minute. A voltage dip occurs when current is drawn over a short period.

36. System impedance (Z) Each conductor has some resistance. As current flows through each resistance, voltage drops Voltage at the load = source voltage minus all IR drops • System impedance depends on: • Length of feeder and branch • Gauge of wire (diameter) • Source capacity

37. Dips and swells trending Trend voltage at the sensitive load • Capture dips and swells as short as a single cycle • Use cursor to read: • Real time stamp (Date: hour: minute: second) • Single cycle Min/Max • Simultaneous recording of voltage and current to isolate source of disturbances

38. Isolating source of disturbance Load disturbance: Downstream current inrush causes voltage sag Source disturbance:Upstream voltage sag causes little change or current drop

39. Flicker • Defined by standard IEC 61000-4-15 • Perceptible flicker in lighting caused by periodic voltage sags • Measured by a statistical “Lamp-Eye-Brain” model that duplicates how most people are affected by flickering incandescent lights • Causes • Loads that draw in periodic “gulps” (ex: arc furnaces, welders) • Basic measurements • PST -- A statistical figure derived over 10 minutes. A reading of 1.0 causes flicker that can be perceived by 50 % of people • PLT -- A statistical figure derived from PST over 2 hrs • Represents the likelihood that fluctuations will cause annoyance Voltage changes of 0.5 %, aprox. eight times per second, can causes perceptible flicker!

40. Flicker measurements • A reading greater than 1 means that most people will perceive flicker in an incandescent bulb • Measurements • Pst (1 min): Short-term flicker over 1 minute • Pst: Short-term flicker over 10 minutes • Plt: Long-term flicker over 2 hours 1745, 1760, 434 and 435 can tackle this item.

41. Gusty power at the wind farm

42. Wind Farm: scenario Transformers were failing much too quickly. Why? • 4 wind turbines share one transformer • Each turbine is equipped with a rectifier and inverter. The inverter produces 50 Hz regardless wind speed. • Transformer has had to be repaired twice in two years.

43. Wind Farm: utility investigation The utilities power monitors haven’t picked up anything. They hired an engineer who hooked up a Fluke 1760 and left it for a week Result: • Transients appeared on every cycle Advice: • The output of the inverter causes transients at the transformer • The engineer suggests: “replace the inverters!”

44. Wind Farm: investigation part II Next: • They did contact the inverter manufacturer • The manufacturer’s technician hooked up a Fluke 1760 and left it for another week

45. Wind Farm: solution • The designers used the data from the Fluke 1760 to identify a problem in the inverter outputs… …Faulty outputs • Action: The manufacturer makes a design change on the inverters and supplies new assemblies to the wind farm Problem solved!

46. Lessons and questions Lessons • Transients can dramatically shorten the life of equipment • Capturing transients and determining how often they occur can require long-term monitoring Questions • What are transients? • What causes transients and what are the effects? • How do we capture transients? • What can we tell about the source of a transient by looking at it’s shape? • Can you protect the system?

47. What are transients? A transient is a disturbance that lasts less than one cycle. We have different types: • Impulsive • oscillatory

48. Transients: cause and effect Causes of transients: • Utility transformer tap switching • Capacitor switching • Lightning • Motors switching off • Switch and relay contact “bounce” Effects of transients: • Damage semiconductor junctions • Damage Insulation • Coupling into adjacent conductors • Corrupt data signals

49. How do we capture transients? Most instruments that support transient capture use Envelope Triggering • Set a tolerance around an ideal sinewave • Any event that goes outside the envelope triggers the instrument to capture the waveform • You get to see voltage (and sometimes current) waveforms for all phases at the exact time of trigger • Cursors and zoom function help with the analysis.

50. Transients with series of oscillations (ringing): Utility capacitot Switching Far away Impules, high frequency transients Local switching Closer Spikes/glitches Transient shape Example: Narrow switching transient of -410 V (under the cursor) and voltage distortion due to SCR dimmer failure