Use of Current Transformer (CT) for High Current Measurement

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Use of Current Transformer (CT) for High Current Measurement Difference in Use of CT and Shunt

Use of Current Transformer (CT) for High Current Measurement

Sr.
No.

CT

Shunt

1.

Power loss in measuring is very small or Nil.

Power loss is more when shunt is used for H. V. Current measured.

2.

Electrical isolation from High voltage circuits in power system.

Electrical isolation from HV circuit is not possible when
shunt is used.

3.

Electro optional technique is possible for measuring Extra High voltage
circuit currents. (EHV)

In EHV circuits shunts cannot be used.


Electro Optional Technique :

  • A voltage signal proportional to the measuring current is generated and is transmitted to the grounds through the technique known as electro optical technique device.
  • Light pulses proportional to the voltage signal are transmitted by a glass optical fibre bundle to a photo detector and converted back into an analog voltage signal.
  • Following Figure shows the EHV current measurement.
Use of Current Transformer (CT) for High Current Measurement Difference in Use of CT and Shunt

The parts of the circuits are as follows :

  1. EHV conductor carrying high value current.
  2. Current sensing CT.
  3. Power supply CT.
  4. Power supply PT.
  5. Analog digital signal converter.
  6. Digital Analog convertor.
  7. Insulator for EHV.
  8. Electro optical glass fibre.
  9. Series high ohmic resistors.
  10. Indicating / Recording unit.

The current transformer (CT) and potential transformer (PT) supply the power to signal converter and optical device.
The accuracy of the system is ± 0.5 %

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