Current transformer before circuit breaker

A current transformer (CT) is often installed before a circuit breaker in a power distribution system. Here's why:

Function of a Current Transformer (CT):

A current transformer is a type of electrical transformer that measures the current flowing through a circuit. It produces a secondary current that is proportional to the primary current, but with a much lower amplitude. The secondary current is typically in the range of 1-5 amps, while the primary current can be in the range of hundreds or thousands of amps.

Purpose of installing a CT before a Circuit Breaker:

The primary purpose of installing a CT before a circuit breaker is to provide a safe and reliable way to measure the current flowing through the circuit. Here are some benefits:

  1. Current measurement: The CT allows for accurate measurement of the current flowing through the circuit, which is essential for monitoring and controlling the power distribution system.
  2. Protection: The CT helps to protect the circuit breaker and the downstream equipment from overcurrents and faults. By detecting the current flowing through the circuit, the CT can trigger the circuit breaker to trip in case of an overcurrent or fault.
  3. Fault detection: The CT can detect faults such as short circuits, overloads, and ground faults, which helps to prevent damage to the equipment and ensure the safety of personnel.
  4. Monitoring: The CT provides a way to monitor the current flowing through the circuit, which helps to identify potential issues and prevent equipment failures.

Typical installation:

In a typical installation, the CT is connected in series with the circuit, usually between the power source and the circuit breaker. The CT secondary current is then sent to a metering device, such as an ammeter or a digital meter, which measures the current and provides an indication of the current flowing through the circuit.

In summary, installing a current transformer before a circuit breaker provides a safe and reliable way to measure the current flowing through the circuit, protects the circuit breaker and downstream equipment, detects faults, and monitors the circuit for potential issues.