Title: EE 2353 HIGH VOLTAGE ENGINEERING
1EE 2353HIGH VOLTAGE ENGINEERING
- D.ELANGOVAN M.E.,
- AP / EEE
- SVCE
- Lecture 2
- UNIT 4 Measurements of AC High Voltages
2Unit 4 Measurements
- MEASUREMENT OF HIGH DC VOLTAGES
- Series Resistance micro ammeter
- Resistance potential divider
- Generating Voltmeters
- Sphere Gaps
2
3Unit 4 Measurements
- MEASUREMENT OF HIGH AC VOLTAGES
- Series impedance voltmeter
- Potential Transformers (CVT)
- Electrostatic Voltmeters
- Potential Dividers
- Sphere gaps
3
4Unit 4 Measurements
- MEASUREMENT OF HIGH AC HIGH FREQUENCY IMPULSE
VOLTAGES - Potential Dividers (R C)
- Peak voltmeters
- Sphere gaps
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5Unit 4 MEASUREMENT OF HIGH DC VOLTAGES
- 1.Series Resistance micro ammeter
- Circuit diagram
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6Unit 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
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7Unit 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
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8Unit 4 MEASUREMENT OF HIGH DC VOLTAGES
- 1.Series Resistance micro ammeter
- Note
- Voltage VIR
- 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
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9Unit 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
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10Unit 4 MEASUREMENT OF HIGH DC VOLTAGES
- 1.Series Resistance micro ammeter
- Drawbacks
- More power dissipation
- Temperature effects
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11Unit 4 MEASUREMENT OF HIGH DC VOLTAGES
- 2.Resistance potential divider
- Need
- To avoid high loading of R
- Another resistor is added
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12Unit 4 MEASUREMENT OF HIGH DC VOLTAGES
- 2.Resistance potential divider
- Circuit diagram
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13Unit 4 MEASUREMENT OF HIGH DC VOLTAGES
- 2.Resistance potential divider
- Construction
- R1 R2 connected in series
- Voltage is measured across R2
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14Unit 4 MEASUREMENT OF HIGH DC VOLTAGES
- 2.Resistance potential divider
- Operation
- DC voltages are measured using resistance voltage
divider - R2 ltltlt R1
- High DC voltage applied.
- Drop across R1
- Measure the voltage directly across R2
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15Unit 4 MEASUREMENT OF HIGH DC VOLTAGES
- 2.Resistance potential divider
- Note
- Power Dissipation in resistor R1
- Need for cooling
- Series connection of resistors
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16Unit 4 MEASUREMENT OF HIGH DC VOLTAGES
- 3.Generating Voltmeter
- Principle
- Variable electrostatic generator which generates
a current proportional to the applied external
voltage
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17Unit 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
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18Unit 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
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19Unit 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
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20Unit 4 Measurements
- MEASUREMENT OF HIGH AC VOLTAGES
- Series impedance voltmeter
- Potential Dividers
- Electrostatic Voltmeters
- Potential Transformers (CVT)
- Sphere gaps
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21Unit 4 MEASUREMENT OF HIGH AC VOLTAGES
- Potential Dividers
- 1.R Dividers
- Power loss
- Temperature Effects
- 2.Series impedance
- 3.C dividers
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22Unit 4 MEASUREMENT OF HIGH AC VOLTAGES
- C dividers
- Series capacitance Dividers
- Apply the voltage
- Drop Across C
- Charging Current s measured using Micro ammeter
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23Unit 4 MEASUREMENT OF HIGH AC VOLTAGES
- C dividers capacitance potential Dividers
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24Unit 4 MEASUREMENT OF HIGH AC VOLTAGES
- C dividers capacitance potential Dividers
- Need to measure
- 1.Withstand-RMS voltage
- 2.Breakdown-Peak voltage
- RMS Peak/v2 for only sine wave
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25Unit 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
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26Unit 4 MEASUREMENT OF HIGH AC VOLTAGES
- RMS value measurement
- 1.Peak voltmeter with potential voltmeter(Davies
, Bowdler ,stand ring circuit) - 2.Electrostatic voltmeter
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27Unit 4 MEASUREMENT OF HIGH AC VOLTAGES
- Peak value measurement
- 1.Series capacitor peak voltmeter
- Principle
- Measure of charging current
- IcV?C
- Construction
- Stand. Capacitor Diode Meter
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28Unit 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
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29Unit 4 MEASUREMENT OF HIGH AC VOLTAGES
- Peak value measurement
- 1.Series capacitor peak voltmeter
- Current leads the voltage
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30Unit 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
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31Unit 4 MEASUREMENT OF HIGH AC VOLTAGES
- Peak voltmeter with potential voltmeter(Davis ,
Bowdler ,stand ring circuit)
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32Unit 4 MEASUREMENT OF HIGH AC VOLTAGES
- Peak voltmeter with potential voltmeter(Davis ,
Bowdler ,stand ring circuit) - The voltage to be measured is applied across
C1C2 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
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33Unit 4 MEASUREMENT OF HIGH AC VOLTAGES
- Peak voltmeter with potential voltmeter(Davis ,
Bowdler ,stand ring circuit) - Discharge Error
- Rest Charge Error
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34Unit 4 MEASUREMENT OF HIGH AC VOLTAGES
- RMS value measurement
- 1.Peak voltmeter with potential voltmeter(Davis ,
Bowdler ,stand ring circuit)
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35Unit 4 MEASUREMENT OF HIGH AC VOLTAGES
- Electrostatic Voltmeter
- Principle
- Force between the parallel plate electrodes is
given by - F1/2 V2A/D2
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36Unit 4 MEASUREMENT OF HIGH AC VOLTAGES
- RMS value measurement
- Electrostatic Voltmeter
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37Unit 4 MEASUREMENT OF HIGH AC VOLTAGES
- Electrostatic Voltmeter
- Construction
- HV Electrode insulated
- from earth
- LV electrode central point is movable
- Light beam
- Scale
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38Unit 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
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39Unit 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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