A Current Transformer (CT) is a vital device used to measure alternating current (AC) safely and efficiently. Its working principle is based on the fundamental concept of electromagnetic induction, similar to a regular transformer.
How Does It Work?
A CT has a primary winding, a secondary winding, and a magnetic core. The key difference is that its primary winding is typically a single, thick conductor (or the main power cable itself) that carries the high current we want to measure. This primary current creates a changing magnetic field in the core. This changing field then induces a proportional, but much smaller, current in the many turns of the secondary winding. The ratio between the primary and secondary current is fixed. For example, with a 100:5 ratio CT, 100 amps flowing in the primary conductor will produce 5 amps in the secondary circuit. This allows high currents to be accurately represented by a standardized, lower value.
Product Features
1. High Accuracy and Transformation Ratio: CTs are designed to have a very precise turns ratio, ensuring that the secondary current is a highly accurate, scaled-down replica of the primary current. This is essential for reliable measurement and system control.
2. Isolation and Safety: A critical feature of a CT is that it electrically isolates the high-voltage primary circuit from the low-voltage secondary circuit. This allows operators and sensitive equipment like meters and relays to work with a safe, low-current signal without any direct connection to dangerous high voltages.
3. Fixed Secondary Current: Regardless of the primary current level, a standard CT is designed to output a maximum of 5A or 1A on its secondary side under normal conditions. This standardization simplifies the design of all connected instruments.
Common Applications
Current Transformer are used everywhere electrical power is distributed and managed.
1. Energy Metering: They are the core component in electricity meters for homes, industries, and the power grid, providing the current signal for billing.
2. Protective Relaying: In electrical substations and switchgear, CTs constantly monitor current. If they detect a fault (like a short-circuit or overload), they send a signal to protective relays which then trip the circuit breaker to isolate the problem.
3. Current Monitoring and Control: They are used in control panels and power management systems to monitor the current flow in various parts of an electrical system, helping in load management and equipment control.
