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Good afternoon. Power Quality issue & Harmonics. by Abdualah Aljankawey 3201836 EE 6643 . Definition. The term power quality means different things to different people .

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  1. Good afternoon

  2. Power Quality issue &Harmonics by Abdualah Aljankawey 3201836 EE 6643

  3. Definition • The term power quality means different things to different people . • Power quality is the interaction of electronic equipment within the electrical environment. This consists of generators, Transformers, breakers, wiring and grounding. • Good power quality would be a reliable supply of sinusoidal, 60Hz waveforms resulting in few operational anomalies.

  4. Why is power quality so important? • Power quality is an increasingly important issue for all electrical consumer . • Problems with powering and grounding can cause data and processing errors that affect production and service quality. • Each time production is interrupted electrical consumer, your loses the margin on the product that is not manufactured and sold

  5. Power Quality problems • Definition. • P.Q. problems is any power problem manifested in voltage , Current ,or frequency deviation that result in failure or miss operation of Costumer equipment. • Surges and spikes (overpowering). • Harmonics ( current & voltage ) • Voltage Fluctuations.

  6. Cont. • Transient voltages . • blackouts . • noise . • sags (under powering). • Poor power quality can yield repeated equipment failures, safety hazards, process interruptions and shutdowns.

  7. Lightning

  8. Transient voltage surge suppressors TVSS

  9. Voltage Fluctuations Lights flickering? It could be the result of voltage fluctuations in your facility's electrical system. High- and low-voltage conditions can result in equipment damage, data loss and erroneous readings on monitoring systems. Overloaded power circuits are typically the cause behind under-voltage conditions. Heavily loaded motors such as air conditioners can result in intermittent low voltages. Less common but more damaging are over-voltage conditions, which can be seen in facilities that have rapidly varying loads.

  10. Harmonics • Harmonic current are generated to small extent and at law distortion level by . 1- Generation equipment . 2- transmission equipment. 3- Distribution equipment . 4- Industrial load . 5- Domestic load.

  11. Harmonic

  12. 5th harmonic distorted sine wave

  13. Harmonics affect Power Quality • Equipment to fail prematurely. • Decrease the efficiency of the electrical. distribution and utilization network. • Causes grounding potential rise. • light flickering. • Faulty operation of Computerized data processing equipments and computer. networks and computer equipment.

  14. Cont. • Faulty operation of Control devices, protective relays etc. • Extra loss in transformer, rotating machines etc. • Noise in electrical equipments • Noise are generated by electronic devices

  15. Total Harmonic Distortion Extras/Measurements The THD is defined as the root mean square (RMS) value of the total harmonics of the signal, divided by the RMS value of its fundamental signal

  16. Mathematical THD

  17. Interruption • Definition :when the voltage drops below 10% of its nominal value it is called an interruption or a blackout.  • interruptions are the most severe form of power problem, because equipment shuts down or lighting goes off since the voltage dropped below the point that these devices can operate. • Where sags and under voltage typically represent more than 92% of power problem events, interruptions represent less than 4% of such problems.

  18. Over voltage • Over voltage is an increase in voltage above 110% of nominal for more than one minute. •   Over voltage has detrimental effects on most electronics by causing them to overheat.

  19. Transient voltage ,noise ,Sag or Dip and Under voltage

  20. Equipment causes Power Quality Problems • Uninterruptible Power Supplies • Variable Frequency Drives • Battery Chargers • Large Motors During Startup • Electronic Dimming Systems • Lighting Ballasts (esp. Electronic) • Arc Welders, and Other Arc Devices • Medical Equipment, e.g. MRI s and X-Ray Machines

  21. Solutions • Power filters . • Isolation transformer . • Line reactors. • Online UPS.

  22. Power filters • Filter is a device that removes something from whatever passes through it. • To eliminate line-current harmonics. • To improve the power factor. • To reduce electrical interference.

  23. Electrical Filter Any combination of Passive (R, L and C) and/or active (transistors or operational amplifiers) elements designed to select or rejects a band of frequencies.

  24. cont • Mainly shunt type • Usually connected in parallel with power system or electric load • Provide low impendence (ZF) path to ground for all harmonic currents at one or more tuned harmonic frequencies.

  25. Important characteristics presented by the filters • Highly effective, reducing harmonics to negligible levels. • Elimination of several harmonics with a single active filter, resulting in a smaller number of filters in the substation. • Absence of problems with resonance frequencies due to interaction with the network impedance or with other filters, capacitor banks or reactors in the station

  26. Cont. • Excellent performance despite variation of the system frequency. • Self-adaptation to changes in the network impedance. • Reduced size, allowing implementation using container techniques. • In addition to reducing installation time, this makes it possible to test the complete equipment as a system at the factory before shipment.

  27. Active filter • Use op amps with resistor and capacitors in their feed loops. • Active filters can have high input impedance ,low out put impedance . • Easier to design than passive filters. • Using Op amp can achieve very good accuracy.

  28. Active Filter

  29. Active filters Circuits based on Op Amps, Resistor, and capacitors

  30. Schematic of Low-Pass Active Filter

  31. Advantages & disadvantages • More flexibility • Better noise filtering. • Easy to Read Graphical Circuit Displays • Doesn’t address fundamental issue of capacitor size. • Issues: • Requires a passive filter before active filter so Op amp doesn’t have to work so hard • Requires quicker op amp • Requires more power. • Generate noise. • Problems of accuracy.

  32. Types of Shunt filters • Switched Tuned Arm Power filters (STAF) • Switched Damped power filters (S.C-Type) • Switched Asymmetrical Tuned Arm Filter (SATAF). • Switched Combined Tuned Arm filter and Static Capacitor Compensator. • Switched Static Capacitor Compensator • Switched Blocking Filter

  33. Main components of Filters • Inductor:- Block high frequency signal, conducts low frequency signal • Capacitor:- Conducts high frequency signal, block low frequency signal • Resistor:- No frequency selective properties, but are used to determine time constants of the circuit

  34. Switched Tuned Arm Filter

  35. Switched Tuned-Arm Filter • Simple and common • Filter impedance Zf=R-j[ωL-1/ωC] • Acts as low impedance at the tuned frequency • effectively shunts most harmonic at frequencies below or above the tuned value • Resonance Frequency fr=1/[2π(LC)] • Used to filter specific dominant frequency

  36. Switched Asymmetrical Tuned Arm Filter • Commercial and industrial nonlinear load (both odd and even harmonics)

  37. Switched TAP +Static capacitor Compensator

  38. Switched C-Type Filter topology

  39. Switched C-Type Power Filters • High pass damped power filters • Used to reduce higher-order harmonics above 5th and 7th orders • Provide low impedance path for wide spectra of dominant harmonics, thus requires less tuning • Less sensitive to temperature variation • Alternative to costly number of TAF • Low quality factor (Q) • Demerits- large capacitance-costly

  40. Switched Tuned Arm Power Filter and capacitor Compensator Scheme

  41. SwitchedHybrid-Tuned filter with wide-band filtering and static capacitor Compensator

  42. Hybrid switched dual-capacitor compensator scheme

  43. Single Phase Switched Filter and capacitor Compensator for single phase motorized load

  44. Single Line Diagram of system and Modulated/PWM TAF

  45. Single line diagram of Distribution system with PWM (TAP) power filter

  46. Single Line Diagram of System and Modulated/ PWM Switched Asymmetrical STAF

  47. General layout of Modulated Power Filter/Switched capacitor Compensator (MPF/SCC)

  48. Single Line Diagram of the Utilization Circuit with the series blocking capacitive Scheme (SBCS)

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