What is the difference between CT and Rogowski coils?

CT (Current Transformer) and Rogowski coils are both devices used for measuring electrical current, but they operate on different principles and have distinct characteristics. Here’s a comparison of the two:

1. Principle of Operation:

• Current Transformer (CT): A CT is a traditional current-sensing device based on the principle of electromagnetic induction. It consists of a magnetic core and a secondary winding. The primary winding is connected in series with the electrical conductor carrying the current to be measured, while the secondary winding is connected to the measuring instrument or protective relay. When current flows through the primary winding, it creates a magnetic field in the core, inducing a proportional current in the secondary winding, which can be accurately measured.
• Rogowski Coil: A Rogowski coil is a flexible current sensor based on the principle of electromagnetic induction. It consists of a coil of wire wound in a helix-like fashion around a toroidal (doughnut-shaped) core, but it doesn’t have a solid magnetic core like CTs. When current flows through the conductor enclosed by the coil, it induces a voltage in the coil, and the integrated voltage provides a measure of the current passing through the conductor.

2. Size and Flexibility:

• CT: CTs are generally larger and bulkier due to their solid magnetic cores. They come in fixed shapes and sizes, and their form factor is not flexible.
• Rogowski Coil: Rogowski coils are more flexible and compact compared to CTs. Their design allows them to be wrapped around irregularly shaped conductors, making them ideal for applications where space is limited or where unconventional conductor shapes are involved.

3. Accuracy:

• CT: CTs are known for their high accuracy, typically providing precise measurements within a few percentage points of the actual current value.
• Rogowski Coil: Rogowski coils are also accurate, but their accuracy might be slightly lower compared to CTs. The accuracy can be influenced by factors such as the length and diameter of the coil and the number of turns.

4. Linearity:

• CT: CTs exhibit good linearity over a wide range of currents. They can accurately measure both low and high current values.
• Rogowski Coil: Rogowski coils are inherently more linear compared to CTs. Their output is directly proportional to the rate of change of the measured current, which can be advantageous in certain applications.

5. Saturation:

• CT: CTs can experience saturation at high currents, leading to inaccuracies in the measurements if the wbac current exceeds their rated capacity.
• Rogowski Coil: Rogowski coils do not have a solid magnetic core, so they do not experience saturation. They can handle a wide dynamic range of currents without significant accuracy loss.

summary

In summary, CTs and Rogowski coils both serve the purpose of measuring electrical current, but their principles of operation, size, flexibility, accuracy, linearity, 1200/5 and saturation characteristics are different. The choice between the two depends on the specific application requirements and constraints.