DC CIRCUIT BREAKER AND FUSE WHICH IS THE ADVANCED PROTECTIVE EQUIPMENT

Many electricians think that fuses are outdated protection appliances, while DC circuit breakers are advanced protection appliances. Is this notion correct?

It can be seen that the time-current characteristic change curve of the fuse is closer to the characteristic analysis curve of the thermal endurance learning ability of the protected working circuit, indicating that it has a better overload protection effect, but its use is not as convenient as the DC circuit breaker. If the DC circuit breaker trips due to overcurrent, it can be closed to supply power after troubleshooting, which is very simple and convenient. The fuse must be replaced in time with the same specification of the fuse, for which it is necessary to provide a variety of spare parts with different specifications, which brings a lot of trouble to the user.

The fuse wiring also needs to be paid more attention. For example, the center terminal of the screw fuse must be connected to the power supply side, and the screw terminal must be connected to the load side. Otherwise, it is easy to cause an electric shock accident when the fuse is replaced.

However, at present, in the environmental design of our country, some factory production enterprises, office buildings and other power distribution systems managed by electrical automation professionals (BA4 and BA5 personnel, see Appendix C) basically use DC circuit breakers. Few need to use fuses, but in some other economically developed countries, the use of these two types of electrical appliances is about half.

As we all know, the price of the DC circuit breaker is very high for the bulk capacity of the main line, while the fuse with a rated current as small as 30 can easily cut off a short-circuit current of 50 kilometers, and the cost of replacing the fuse is very limited. In addition, after switching off the DC circuit breaker, the blocking capacity of the contacts remains unchanged after replacing with a new spare. In this regard, it would be safer to cut the short circuit with a fuse.

In addition, when the current level difference of each fuse according to the product standard (ie, the agreed non-fusing current If is 1.25in, and the agreed fusing current If is 1.6in) is 1.6 times, the product standard specifies all levels of fuses Its selectivity can be guaranteed when used as overload protection, but it is difficult to achieve DC circuit breakers. In other words, fuses have better selectivity between overload protection levels, which can reduce the surface of power failure during overload protection action.