Question

The voltage transformer is also known as ________. (Air core transformer Potential transformer)

Hint:

A Potential Transformer (PT) is designed as an extremely precise step-down voltage transformer that operates under near-open-circuit conditions to maintain highly accurate primary-to-secondary transformation ratios.

Answer 1

Step 1: Understanding Voltage Transformations in Power Systems:
High-voltage transmission lines carry voltages in the kilovolt (kV) range. To safely measure these voltages or connect control systems, the high voltages must be scaled down to standard, manageable levels.

Step 2: Instrument Transformer Classifications:
This scaling is performed using specialized instrument transformers:

• Current Transformer (CT): Steps down line currents to standard low levels (typically $1\text{ A}$ or $5\text{ A}$) for measurement.
• Potential Transformer (PT): A highly accurate step-down transformer that scales down high primary voltages to standard safe secondary values (typically $110\text{ V}$) for metering, monitoring, and protective relays.

Step 3: Comparing with Air Core Transformers:
An air-core transformer does not contain an iron magnetic core and is designed to minimize core losses at high radio frequencies, which is entirely different from power-frequency utility metering.

Step 4: Conclusion:
Therefore, a voltage transformer is also known as a Potential transformer.