The function of protective relay in a circuit breaker is

The function of a protective relay in a circuit breaker is to detect abnormal conditions in the electrical circuit and trip the circuit breaker to disconnect the power supply in case of a fault or abnormality. The relay is designed to detect specific types of faults or abnormalities, such as:

  1. Overcurrent: The relay detects an excessive current flow in the circuit, which may indicate a short circuit or overload.
  2. Overvoltage: The relay detects an excessive voltage in the circuit, which may indicate a fault or abnormality in the power supply.
  3. Undervoltage: The relay detects a low voltage in the circuit, which may indicate a fault or abnormality in the power supply.
  4. Ground fault: The relay detects a ground fault, which is a fault that occurs when a current flows to ground.
  5. Phase fault: The relay detects a phase fault, which is a fault that occurs when a current flows between two or more phases of a polyphase circuit.

The protective relay uses various techniques to detect these faults, including:

  1. Current sensing: The relay measures the current flowing in the circuit and compares it to a set threshold.
  2. Voltage sensing: The relay measures the voltage in the circuit and compares it to a set threshold.
  3. Frequency sensing: The relay measures the frequency of the voltage in the circuit and compares it to a set threshold.
  4. Time delay: The relay uses a time delay to allow the fault to clear itself before tripping the circuit breaker.

The protective relay is typically connected to the circuit breaker and is designed to trip the breaker quickly enough to prevent damage to the equipment or personnel. The relay is also designed to reset automatically once the fault has cleared, allowing the circuit breaker to be re-closed and the power supply to be restored.