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ACB TRIP | Top #3 ACB Trip reasons and its protection settings

October 25, 2019

ACB TRIP | Top #3 ACB Trip reasons and its protection settings

ACB is the short form for Air Circuit Breaker. Air circuit breakers (ACBs) are used for the protection of circuits that have a current of about 800 Amperes to 10-kilo Amperes flowing through them. The ACB provides circuit protection against the short circuit and the overcurrent condition in an electrical circuit. Air circuit breakers (ACBs) are used in circuits where the voltage range of the circuit is below 450 Volts. The ACB trip is described as when the current or voltage in a circuit in which the current between 800A to 10kA is flowing gets greater than the predefined values the ACB gets opened and the flow of current and voltage in the circuit is stopped. Similarly, ACB is opened in case of a short circuit and it prevents the circuit from more damage. The main function of the ACB is to quench the arching during overloading. 

Top three reasons due to which the circuit breaker keeps on tripping

Short Circuit:

  • The most common reason for the tripping of a circuit breaker is the short circuit. This short circuit condition is more hazardous than the overload condition due to which a circuit breaker trips. A short circuit occurs when a neutral wire and a hot wire are in contact and in this state a huge amount of current is allowed to flow throughout the wires and more heat is produced due to the extensive flow of current. This condition results in a fire in the wire and the whole wiring can catch the wire in this condition which can result in serious impacts. The reason behind the short-circuiting is faulty wiring and the loss of connections in the wiring.

Circuit Overload:

  • Each circuit has its own parameters for electrical flow. When the circuit is imposed to input greater than its original capacity then the overloading of the circuit occurs. If a light bulb has a rating of 5A and is exposed to a current of 8A the bulb will be overheated and overloading will occur which can result in the damaged appliance. Similarly, if a circuit is provided an input greater than its rating the circuit will be overloaded. Overloading of the circuit can trip the circuit breaker constantly if the issue is not fixed.

Ground Fault Surge:

  • Ground fault surge occurs when a hot wire is a contact with a ground wire due to any reason such as removed covering or insulation of the wire or faulty connection of the wire.  When there is a ground fault surge a huge amount of electricity starts flowing in the wires and circuit which can result in overheating of the wires and circuit. The constant ground fault surge present in the circuit will trip the circuit again and again. 

ACB Protection Settings

The protection settings for a circuit which should be known are as follows:

  • Long Time Delay.
    • The long-time delay should be adjusted in such a manner that the inrush current should be allowed to pass through the circuit breaker without tripping when the motor starts.
  • Ground Fault Pickup.
    • The ground fault pickup should be adjusted to a 20%-70% rating of the breaker. Ground fault pickup is the amount of ground-fault current which will bring the circuit breaker to the tripping point.
  • Continuous Amps.
    • The level of the current which will be allowed to pass through the circuit breaker without tripping is called the continuous amp. The continuous amp can be set in the range of 20% to 100% or the circuit breaker's normal rating.
  • Instantaneous Pickup.
    • When a circuit breaker is to be tripped without any intentional delay instantaneous pickup value should be adjusted between 2 to 40 times of the breaker's current. 
  • Short-Time Pickup.
    • For the selective tripping of the circuit breaker, the short-time pickup is used. The amount of the current which should be allowed to pass through the breaker for a short interval of time is determined by the short-time pickup. 
  • Short-Time Delay.
    • Short time delay is used with the short time pickup and it is the time for the postponing of the short time pickup trip.