The purpose of LV protection unit
If we are talking about LV applications, protection (or trip) unit is functional part of circuit breaker, and in most cases, they are physically integrated in the same housing as well. So, in order to explain a purpose of protection unit better, let us first remember what does a circuit breaker actually do.
Circuit breaker is a device which, as the name implies, serves to safely break the circuit while current flows through it. This circuit breaker operation can be initiated by two different reasons:
- Electrical operator (or some other person) wants to switch off some circuit. This usually happens while actual current is smaller than rated current of the circuit.
- Some fault downstream of circuit breaker occurs. In this case, actual current (or voltage) will be outside rated limits for the circuit, and circuit breaker will disconnect it from the supply, in order to prevent damage of the equipment and safety risk.
In other case listed above, operation of the circuit breaker will be initiated without intervention of any external factor or device, including an electrician, or some other technical personel.