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Measurement of high_voltage_and_high_currentunit_iv_full_version

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High voltage engineering
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Measurement of high_voltage_and_high_currentunit_iv_full_version

  1. 1. SVCE 1 EE 2353 HIGH VOLTAGE ENGINEERING D.ELANGOVAN M.E., AP / EEE SVCE Lecture# 2 UNIT 4 – Measurements of AC High Voltages
  2. 2. SVCE 2 Unit 4 Measurements MEASUREMENT OF HIGH DC VOLTAGES Series Resistance micro ammeter  Resistance potential divider  Generating Voltmeters  Sphere Gaps
  3. 3. SVCE 3 Unit 4 Measurements MEASUREMENT OF HIGH AC VOLTAGES  Series impedance voltmeter  Potential Transformers (CVT)  Electrostatic Voltmeters  Potential Dividers  Sphere gaps
  4. 4. SVCE 4 Unit 4 Measurements MEASUREMENT OF HIGH AC HIGH FREQUENCY & IMPULSE VOLTAGES  Potential Dividers (R & C)  Peak voltmeters  Sphere gaps
  5. 5. SVCE 5 Unit 4 MEASUREMENT OF HIGH DC VOLTAGES 1.Series Resistance micro ammeter Circuit diagram:
  6. 6. SVCE 6 Unit 4 MEASUREMENT OF HIGH DC VOLTAGES 1.Series Resistance micro ammeter Construction: A large value of resistance (few hundreds of mega ohms) is connected in series with uA Protective device (Zenor diode, neon glow tube)connected across the uA
  7. 7. SVCE 7 Unit 4 MEASUREMENT OF HIGH DC VOLTAGES 1.Series Resistance micro ammeter operation R should be high High DC voltage is applied Voltage drop across the resistance The current flowing thro’ R is measured in uA
  8. 8. SVCE 8 Unit 4 MEASUREMENT OF HIGH DC VOLTAGES 1.Series Resistance micro ammeter Note: Voltage V=IR Drop in Ammeter is negligible R should be chosen such that 1 to 10 uA is allowed for full scale deflection 500 kv can be measured Accuracy : 0.2%
  9. 9. SVCE 9 Unit 4 MEASUREMENT OF HIGH DC VOLTAGES 1.Series Resistance micro ammeter Need for protective device If R fails, heavy current will flow thro’ uA To divert protective device is used
  10. 10. SVCE 10 Unit 4 MEASUREMENT OF HIGH DC VOLTAGES 1.Series Resistance micro ammeter Drawbacks More power dissipation Temperature effects
  11. 11. SVCE 11 Unit 4 MEASUREMENT OF HIGH DC VOLTAGES 2.Resistance potential divider Need To avoid high loading of R Another resistor is added
  12. 12. SVCE 12 Unit 4 MEASUREMENT OF HIGH DC VOLTAGES 2.Resistance potential divider Circuit diagram
  13. 13. SVCE 13 Unit 4 MEASUREMENT OF HIGH DC VOLTAGES 2.Resistance potential divider Construction R1 R2 connected in series Voltage is measured across R2
  14. 14. SVCE 14 Unit 4 MEASUREMENT OF HIGH DC VOLTAGES 2.Resistance potential divider Operation DC voltages are measured using resistance voltage divider R2 <<< R1 High DC voltage applied. Drop across R1 Measure the voltage directly across R2
  15. 15. SVCE 15 Unit 4 MEASUREMENT OF HIGH DC VOLTAGES 2.Resistance potential divider Note Power Dissipation in resistor R1 Need for cooling Series connection of resistors
  16. 16. SVCE 16 Unit 4 MEASUREMENT OF HIGH DC VOLTAGES 3.Generating Voltmeter Principle Variable electrostatic generator which generates a current proportional to the applied external voltage
  17. 17. SVCE 17 Unit 4 MEASUREMENT OF HIGH DC VOLTAGES 3.Generating Voltmeter Time variant capacitance system can be developed between the high voltage electrode and earthed electrode, then current flowing to earth electrode will be a measure of the voltage
  18. 18. SVCE 18 Unit 4 MEASUREMENT OF HIGH DC VOLTAGES 3.Generating Voltmeter Connect High voltage source to disc electrode H L1,L2,L3 are earthed electrode The L1 has vanes and its rotated at constant speed The rotor vanes of L1 periodically cover and uncover the static sensing electrode L3 Capacitance between H & L3 changes periodically
  19. 19. SVCE 19 Unit 4 MEASUREMENT OF HIGH DC VOLTAGES 3.Generating Voltmeter The shape and No of vanes of L1,L2 are designed that they produce sinusoidal variation in the capacitance The generated ac current is rectified and read by a moving coil instrument
  20. 20. SVCE 20 Unit 4 Measurements MEASUREMENT OF HIGH AC VOLTAGES  Series impedance voltmeter  Potential Dividers Electrostatic Voltmeters  Potential Transformers (CVT) Sphere gaps
  21. 21. SVCE 21 Unit 4 MEASUREMENT OF HIGH AC VOLTAGES Potential Dividers 1.R Dividers  Power loss  Temperature Effects 2.Series impedance 3.C dividers
  22. 22. SVCE 22 Unit 4 MEASUREMENT OF HIGH AC VOLTAGES C dividers Series capacitance Dividers Apply the voltage Drop Across C Charging Current s measured using Micro ammeter
  23. 23. SVCE 23 Unit 4 MEASUREMENT OF HIGH AC VOLTAGES C dividers capacitance potential Dividers
  24. 24. SVCE 24 Unit 4 MEASUREMENT OF HIGH AC VOLTAGES C dividers capacitance potential Dividers Need to measure 1.Withstand-RMS voltage 2.Breakdown-Peak voltage RMS = Peak/√2 for only sine wave
  25. 25. SVCE 25 Unit 4 MEASUREMENT OF HIGH AC VOLTAGES Peak value measurement 1.Chubb-Frotscue method ( Series capacitor peak voltmeter) 2.Peak voltmeter with potential voltmeter(Davis , Bowdler ,stand ring circuit) 3.Digital peak voltmeter 4.Sphere gap
  26. 26. SVCE 26 Unit 4 MEASUREMENT OF HIGH AC VOLTAGES RMS value measurement 1.Peak voltmeter with potential voltmeter(Davies , Bowdler ,stand ring circuit) 2.Electrostatic voltmeter
  27. 27. SVCE 27 Unit 4 MEASUREMENT OF HIGH AC VOLTAGES Peak value measurement 1.Series capacitor peak voltmeter: Principle Measure of charging current Ic=VὡC Construction Stand. Capacitor Diode & Meter
  28. 28. SVCE 28 Unit 4 MEASUREMENT OF HIGH AC VOLTAGES 1.Series capacitor peak voltmeter: Operation Apply voltage Charging current is rectified by D1 and measured Other half cycle no conduction
  29. 29. SVCE 29 Unit 4 MEASUREMENT OF HIGH AC VOLTAGES Peak value measurement 1.Series capacitor peak voltmeter: Current leads the voltage
  30. 30. SVCE 30 Unit 4 MEASUREMENT OF HIGH AC VOLTAGES Peak value measurement 1.Series capacitor peak voltmeter: Drawbacks Voltage wave shape is not pure Sinusoidal. Contains oscillations Current may not be uniform Calibration is wrong
  31. 31. SVCE 31 Unit 4 MEASUREMENT OF HIGH AC VOLTAGES Peak voltmeter with potential voltmeter(Davis , Bowdler ,stand ring circuit)
  32. 32. SVCE 32 Unit 4 MEASUREMENT OF HIGH AC VOLTAGES Peak voltmeter with potential voltmeter(Davis , Bowdler ,stand ring circuit) The voltage to be measured is applied across C1&C2 divider. The voltage appears on C2 is rectified into DC and charge the Cs. Meter read the peak value of C2 Multiplying Divider ratio we can get the voltage to be measured
  33. 33. SVCE 33 Unit 4 MEASUREMENT OF HIGH AC VOLTAGES Peak voltmeter with potential voltmeter(Davis , Bowdler ,stand ring circuit) Discharge Error Rest Charge Error
  34. 34. SVCE 34 Unit 4 MEASUREMENT OF HIGH AC VOLTAGES RMS value measurement 1.Peak voltmeter with potential voltmeter(Davis , Bowdler ,stand ring circuit)
  35. 35. SVCE 35 Unit 4 MEASUREMENT OF HIGH AC VOLTAGES Electrostatic Voltmeter Principle Force between the parallel plate electrodes is given by F=1/2 €V2 A/D2
  36. 36. SVCE 36 Unit 4 MEASUREMENT OF HIGH AC VOLTAGES RMS value measurement Electrostatic Voltmeter
  37. 37. SVCE 37 Unit 4 MEASUREMENT OF HIGH AC VOLTAGES Electrostatic Voltmeter Construction HV Electrode insulated from earth LV electrode – central point is movable Light beam Scale
  38. 38. SVCE 38 Unit 4 MEASUREMENT OF HIGH AC VOLTAGES Electrostatic Voltmeter Operation High voltage is applied Due to electrostatic forces deflection of rotating Element Light focused on the mirror Gets reflected & measured
  39. 39. SVCE 39 Unit 4 MEASUREMENT OF HIGH AC VOLTAGES Electrostatic Voltmeter Drawback For a Constant distance d, the sensitivity is small Advantage No source loading Continuous Reading also possible

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