What is the working principle of CVT?
2 Answers
A Capacitance Voltage Transformer (CVT) is used primarily in high-voltage systems to measure voltage. Here’s a brief overview of its working principle:
1. **Capacitance Divider:** The CVT employs a capacitive voltage divider as its primary measurement element. It consists of a high-voltage capacitor (the primary capacitor) and a lower-voltage capacitor (the secondary capacitor). The high-voltage capacitor is connected in series with the high-voltage line, and the secondary capacitor is connected across the secondary winding of the transformer.
2. **Voltage Scaling:** The high-voltage capacitor divides the line voltage into a lower voltage. This voltage is proportional to the line voltage but is much lower and safe for measurement.
3. **Voltage to Current Conversion:** The lower voltage from the capacitive divider is then converted into an equivalent current. This is often done using a transformer with a secondary winding. The secondary winding of this transformer produces a proportional current that is easier to handle and measure.
4. **Measurement:** The current or the scaled-down voltage is then used for measurement and control purposes. This scaled-down voltage can be connected to conventional voltage measuring instruments or relays.
5. **Additional Components:** CVTs often include a series inductor to improve the frequency response and reduce harmonics. This inductor helps in achieving a more accurate representation of the high-voltage signal.
The main advantage of a CVT is its ability to safely measure high voltages without needing a direct connection to the high-voltage line, reducing safety risks and maintenance needs.
1. **Capacitance Divider:** The CVT employs a capacitive voltage divider as its primary measurement element. It consists of a high-voltage capacitor (the primary capacitor) and a lower-voltage capacitor (the secondary capacitor). The high-voltage capacitor is connected in series with the high-voltage line, and the secondary capacitor is connected across the secondary winding of the transformer.
2. **Voltage Scaling:** The high-voltage capacitor divides the line voltage into a lower voltage. This voltage is proportional to the line voltage but is much lower and safe for measurement.
3. **Voltage to Current Conversion:** The lower voltage from the capacitive divider is then converted into an equivalent current. This is often done using a transformer with a secondary winding. The secondary winding of this transformer produces a proportional current that is easier to handle and measure.
4. **Measurement:** The current or the scaled-down voltage is then used for measurement and control purposes. This scaled-down voltage can be connected to conventional voltage measuring instruments or relays.
5. **Additional Components:** CVTs often include a series inductor to improve the frequency response and reduce harmonics. This inductor helps in achieving a more accurate representation of the high-voltage signal.
The main advantage of a CVT is its ability to safely measure high voltages without needing a direct connection to the high-voltage line, reducing safety risks and maintenance needs.