Low voltage circuit breaker protection circuit a

 (1) A circuit with a low-voltage circuit breaker alone or a low-voltage circuit breaker and a knife switch
    1) For a substation with only one main transformer , the low-voltage side main switch uses a low-voltage circuit breaker, as shown in Figure 14-31a.
    2) For a substation equipped with two main transformers, when a low-voltage circuit breaker is used as the main switch on the low-voltage side, the capacity of the low-voltage circuit breaker should take into account that
when one main transformer stops working, the other main transformer will supply power to the substation. 60% to more than 70% of the load and all primary and secondary loads, and
both bus sections are live at this time. In order to ensure the safety of maintenance of the main transformer and low-voltage circuit breaker, the busbar of the low-voltage circuit breaker should be equipped with a knife switch or
isolating switch, as shown in Figure 14-31b, to isolate the feedback power from the low-voltage busbar.
  3) For low-voltage circuit breakers installed on low-voltage distribution outlets, in order to ensure the safety of maintenance of distribution outlets and low-voltage circuit breakers,
a knife switch should be installed on the busbar side of the low-voltage circuit breaker, as shown in Figure 14-31c, to isolate Power from the low voltage bus.
    (2) Circuits in which low-voltage circuit breakers cooperate with magnetic starters or contactors. For low-voltage circuits that operate frequently,
the wiring method shown in Figure 14-31d should be used. The low-voltage circuit breaker here is mainly used for short-circuit protection of the circuit, while the electromagnetic starter or contactor is used for the control of frequent operation of the circuit
, and the thermal relay on it is used for overload protection.
    (3) A circuit in which a low-voltage circuit breaker and a fuse cooperate. If the breaking capacity of the low-voltage circuit breaker is not sufficient to interrupt the short-circuit current of the circuit,
the wiring method shown in Figure 14-31e can be used. o. The low-voltage circuit breaker here is used as a circuit front on-off control and overload and voltage loss protection. It only installs a thermal
tripper and a voltage loss release. It does not install an overcurrent release, but uses a fuse or knife fuse. switch to achieve short circuit protection. If a self-resetting
fuse is used in conjunction with a low-voltage circuit breaker, it can not only effectively cut off the short-circuit current, but also automatically restore power supply after the short-circuit fault is eliminated,
thus greatly improving power supply reliability. Our country has now produced low-voltage circuit breakers such as IhlO-lOOR that combine low-voltage circuit breakers with resettable fuses
. This type of low-voltage circuit breakers will be used in low-voltage circuits.