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Power Quality Problems & Solutions

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Published in: Electrical
16,117 Views

Notes On Various Power Quality Issues Present In An Electrical System And Their Respective Solutions.

Bhupali K / Pune

33 years of teaching experience

Qualification: M.Tech (PES's, Modern college of engineering, pune - 2015)

Teaches: Algebra, Mathematics, Physics, Electrical, Electronics

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  1. Welcome to Presentation of Seminar on Power Quality Problems & Solutions" Miss, Bhupali P. Kumbhar
  2. Content ' Introduction — Definition / meaning — Poor & Good Power Quality ' Power Quality Problems (PQP) — Categories of power quality problems ' Causes & Consequences of PQP ' Solutions to PQP ' References 2
  3. Power Quality Power Quality: — Electrical network's ability to supply a clean & stable power supply ' Poor Power Quality: — sufficient deviation in the power supply to cause equipment failure Good Power Quality: — power supply is sufficient for the equipment to operate satisfactorily ' Power Quality = Voltage Quality, P = V I 3
  4. Power Quality Problems Voltage sag (or dip) Short-interruptions Long interruptions Voltage spikes Voltage swells Harmonic distortion Voltage fluctuations Noise Voltage Imbalance 4
  5. Voltage Sag(or Dip) Definition: — Decrease of the voltage level between 10 and 90% of the nominal rms voltage Causes: — Faults on the transmission or distribution network. — Faults in consumer's installation. — Connection of heavy loads & start-up of large motors. ' Consequences: — Malfunction of microprocessor- based control systems that may lead to a process stoppage. — Tripping of electromechanical relays. Instantaneous Value 5 -100% -150% RMS Value •120% 5
  6. Short-Interruptions ' Total interruption of electrical supply for duration from few milliseconds to one or two seconds. Causes: — Opening and automatic reclosure of protection devices. — Insulation failure, lightning and insulator flashover. ' Consequences: — Tripping of protection devices. — Loss of information and malfunction of data processing equipment. — Stoppage of sensitive equipment (such as ASDs, PLCs). 300 ms 6
  7. Long Interruptions Total interruption of electrical supply for duration greater than 1 to 2 seconds. Causes: — Equipment failure in the power system network. — Storms and objects (trees, cars, etc) striking lines or poles, fire. — Human error, bad coordination or failure of protection devices. ' Consequences: — Stoppage of all equipment. 1000/0 -100% Time 7
  8. Voltage Spike Definition: — Very fast variation of the voltage value for durations from a several microseconds to few milliseconds Causes: — Lightning, switching of lines or power factor correction capacitors, disconnection of heavy loads. Consequences: Destruction of components (particularly electronic components) and of insulation materials — data processing errors or data loss — electromagnetic interference. Voltage Spil«e 8
  9. Voltage Swell Definition: — Increase in RMS voltage above 110% at power frequency Causes: — Start/stop of heavy loads. Poorly dimensioned power sources. — Poorly regulated transformers. Consequences: Flickering of lighting and screens. — Damage or stoppage or damage of sensitive equipment. Voltage swell wave form 100% .100% 9
  10. Harmonic Distortion waveform corresponds to the sum of different sine-waves with different magnitude and phase, having frequencies that are multiples of power frequency Causes: — all non-linear loads: power electronics equipment SMPS, data processing equipment Consequences: overheating of all cables and equipment loss of efficiency in electric machines errors in measures when using average reading meters — tripping of thermal protections. u menta arm •c 10 Ti me
  11. Voltage Fluctuations Definition: — Oscillation of voltage value, amplitude modulated by a signal with frequency of 0 to 30 Hz. Causes: — Frequent start/stop of electric motors oscillating loads Consequences — flickering of lighting and screens t 11
  12. Noise Definition: — Superimposing of high frequency signals on the waveform of the power-system frequency. Causes: — Electromagnetic interferences provoked by microwaves, television diffusion — Radiation due to welding machines — Improper grounding Consequences: — Disturbances on sensitive electronic equipment — data processing errors. 12
  13. Voltage Imbalance A voltage variation in a three-phase system in which the three voltage magnitudes or the phase-angle differences between them are not equal. Causes: — Large single-phase loads — Incorrect distribution of loads by the three phases of the system. Consequences: — The most affected loads are three phase induction machines. — Increase in the losses. 13
  14. PQ Solutions POWER CONDITIONING EQUIPMENT 1. 2. 3. 4. 5. 6. 7. 8. 9. Transient Voltage Surge Suppressors (TV SS) Filters Isolation Transformers Voltage Regulators Dynamic Voltage Restorer Uninterruptible Power Supply (UPS) Unified Power Quality Conditioner (UPQC) Static Var Compensator(SVC) Thyristor based static switch 14
  15. References ' Anfbal T. de Almeida (2003). A Presentation on 'Power Quality Problems and New Solutions' in International Conference on Renewable Power and Power Quality '03 Vigo, University of Coimbra (April 9 — 11). Mandela Gain (2012). 'Power Quality Problems and solutions: An Overview' in International Journal of Science and Research, Vol. 3(10) 15
  16. ??-???? YOU 16

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