Introduction
The Knee Point Voltage Calculator is a useful tool for determining the knee point voltage of a current transformer (CT). Knee point voltage is an essential parameter for protective relays and devices in power systems. To use this calculator effectively, follow the instructions below.
How to Use
Fill in the values for fault current (in amps), CT ratio, secondary winding resistance (in ohms), lead resistance (in ohms), and relay burden (in ohms). Click the “Calculate” button, and the Knee Point Voltage will be displayed.
Formula
The Knee Point Voltage (Vkp) is calculated using the formula:
Vkp = (2 * IF) / (CT * (RCT + RL + RB))
Where:
- Vkp: Knee Point Voltage (Volts)
- IF: Fault Current (Amps)
- CT: CT Ratio
- RCT: Secondary Winding Resistance (Ohms)
- RL: Lead Resistance (Ohms)
- RB: Relay Burden (Ohms)
Example
Let’s say you have a fault current of 500 Amps, a CT ratio of 1000, secondary winding resistance of 0.5 Ohms, lead resistance of 0.2 Ohms, and relay burden of 0.1 Ohms. Plugging these values into the formula:
Vkp = (2 * 500) / (1000 * (0.5 + 0.2 + 0.1))
Vkp ≈ 833.33 Volts
So, the Knee Point Voltage is approximately 833.33 Volts.
FAQs
- What is Knee Point Voltage?
Knee Point Voltage is the voltage at which a current transformer (CT) operates most effectively. It’s crucial for protective relays to ensure accurate operation during fault conditions. - Why is CT Ratio important?
CT Ratio determines the relationship between primary and secondary current. It’s essential for accurately scaling the output to match the fault current. - What is Relay Burden?
Relay Burden refers to the impedance of the protective relay connected to the CT. It’s necessary for calculating the Knee Point Voltage accurately.
Conclusion
The Knee Point Voltage Calculator simplifies the process of determining the knee point voltage, a critical parameter in power system protection. Ensure your protective relays operate effectively by using this tool to calculate the Knee Point Voltage accurately.