Abstract: Through the specific distribution system,the effects of different types of circuit breakers on the thermal stability of low voltage cables are calculated in detail.According to the normal frame level of the circuit breaker rated current,the cable section of the distribution circuit is 6 mm² or above,which can meet the requirements of thermal stability.It is proposed that the thermal stability of the cable should not be checked unless it is very close to the distribution cabinet of the substation or the cable section of the distribution circuit is very small.

Key words: thermal stability check, thermal effect, three-phase short-circuit current, transient protection, short delay protection