1. What is CT Ratio?

CT Ratio (Current Transformer Ratio) is the ratio of primary current to secondary current in a current transformer. It indicates how much the primary current is reduced to a measurable secondary current for protection and metering applications.

2. How Does the Calculator Work?

The calculator uses the CT Ratio formula:

Where:

• Primary Current — Input current flowing through the transformer (amps)
• Secondary Current — Output current from the transformer (amps)

Explanation: The ratio represents the transformation relationship between the primary and secondary sides of the current transformer.

3. Importance of CT Ratio Calculation

Details: Accurate CT ratio calculation is essential for proper relay protection, energy metering accuracy, and system monitoring in electrical power systems.

4. Using the Calculator

Tips: Enter primary current and secondary current in amps. Both values must be valid (greater than 0). The calculator will compute the CT ratio.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical CT ratio?
A: Common CT ratios include 100:5, 200:5, 400:5, 800:5, etc., where the first number is primary current and second is secondary current in amps.

Q2: Why are CT ratios important in protection systems?
A: CT ratios ensure that protective relays receive accurate current measurements to detect faults and operate correctly during abnormal conditions.

Q3: Can CT ratio affect meter readings?
A: Yes, incorrect CT ratio settings can lead to inaccurate energy measurements and billing errors in metering applications.

Q4: What happens if secondary current is zero?
A: Division by zero is undefined. Secondary current must always be greater than zero for valid CT ratio calculation.

Q5: How do I select the right CT ratio?
A: CT ratio selection depends on maximum expected primary current, burden requirements, and the specific application (protection vs. metering).