CT (Current Transformer) and PT (Potential Transformer) are instrument transformers used in electrical systems to measure high current and voltage safely by stepping them down to lower, manageable values.
- Current Transformer (CT):
- Used to measure high current
- Converts large current into a smaller, proportional current
- Always connected in series with the circuit
- Potential Transformer (PT):
- Used to measure high voltage
- Converts high voltage into a lower, proportional voltage
- Connected in parallel with the circuit
Why they are used:
- Ensure safety of measuring instruments
- Enable accurate readings in power systems
- Used in metering and protection systems
Testing of CT and PT:
For CT:
- Polarity test: Checks correct terminal identification
- Ratio test: Verifies current transformation ratio
- Insulation resistance test: Ensures insulation safety
- Continuity test: Checks circuit completeness
For PT:
- Voltage ratio test: Confirms correct voltage transformation
- Polarity test: Ensures correct phase relation
- Insulation resistance test: Checks insulation strength
- Load (burden) test: Verifies performance under load
In simple terms:
CT measures high current and PT measures high voltage, and both are tested to ensure accurate and safe operation in electrical systems.