When a large current is opened, a strong arc is generated, and the breaking current of the circuit breaker depends on its arc extinguishing ability. When the fault current is higher than its breaking current, the circuit breaker cannot be extinguished well when the circuit breaker is opened, and the circuit breaker will explode in severe cases.
A large amount of heat is generated when a large current passes through the main electrode of the circuit breaker. The thermally stable current of the circuit breaker depends on the DC resistance of the circuit breaker. When the fault current is higher than its thermally stable current, the main contact of the circuit breaker may be burned out.
When a large current passes through the main electrode of the circuit breaker, a certain electromagnetic force is also generated. The dynamic and stable current of the circuit breaker depends on the structure of the circuit breaker and the distance between the phases. When the fault current is higher than its dynamic stability current, the electrode of the circuit breaker may be damaged by electromagnetic force, and in serious cases, the porcelain bottle may crack or even explode.
The same is true for the thermally stable currents of current transformers and grounding switches. Among them, the current transformer should pay more attention to the thermal stable current, because its secondary current is more likely to overheat.