Current Transformer (CT) – Construction and Working Principle

Potential Transformer Working Principle

The potential transformer attached to the power network whose voltage should be sensed is connected between the ground and the phase. That means the primary section of a potential transformer is attached to the high voltage network, and the secondary section of a transformer is connected to a multimeter. Because of the mutual induction, the two sides are magnetically joined together and operate on the principle of electromagnetic induction.
The reduced voltage is detected through the secondary side with respect to the voltage within the primary section using a voltmeter. Because of the large impedance in the system, the small current moves across the secondary side and performs similarly to the usual transformer with no or low power. Hence these kinds of transformers work at a voltage level of 50 to 200VA. Click here to explore more about the principle of a potential transformer.
Based on the convention transformer, the transformation ratio is

Where ‘V₁’is the voltage of the primary winding, ‘V₂’ is the voltage of the secondary side, ‘N₁’is the number of turns in the primary section, and ‘N₂’is the number of turns in the secondary side. The high voltage of a network can be identified using the above formula.

Potential Transformers Classification

Potential transformers can be classified into the following forms based on their function.

• 
  Metering voltage transformers
  
• 
  Protection voltage transformers
  
• 
  Electromagnetic Potential Transformers
  
• 
  Capacitive Potential Transformers
  

Protection Voltage Transformers

These exist in single or three-phase types and work with the highest accuracy. They are utilized to perform and monitor measuring instruments, relays, and other devices.

Electromagnetic Potential Transformers

These are the same as the primary transformer, where primary and secondary sections are wounded on a magnetic center. It operates based on a value of above or below 130KV. The primary section is determined based on the phase, and the secondary section is connected to the ground. They are employed in the relay, metering, and high voltage networks.