What is the purpose of filling the fuse with quartz sand

The purpose of filling the fuse with quartz detection-quartz sand is to enhance the arc extinguishing ability of the fuse. Quartz sand has high thermal conductivity insulation performance, has a large contact area with the arc, easy to absorb arc energy, so it can make the arc quickly cooled.

The quartz sand used to fill fuses is usually carefully selected specially treated. In order to ensure its density, special equipment must be used for filling, users are allowed to fill at will, so as to deteriorate the performance of the fuse.

How to coordinate the selective protection between the upper lower levels of fuses other electrical appliances?

For a system, if there is a failure, the impact of the failure must be limited to a minimum. This requires cutting off the power supply nearest the point of failure. In the system between the upper lower levels, it is required to selectively fuse the lower fuses, the higher level fuses will be affected. Specifically, the rated current of the upper fuse must be greater than that of the lower fuse. The coordination of the upper lower fuses is usually called coordination coordination. Fuses other electrical appliances should also have such coordination coordination. The new standard stipulates the selectivity of overcurrent protection between upper lower fuses, with the ratio of 1.6:1 2:1 respectively. For example, when the rated current of the level fuse is 100A, the rated current of the higher level fuse should be 160A 200A. The proportion to be used is usually specified in the technical conditions of the product. As for the coordination between fuse other electrical appliances, it should be determined by calculation according to their respective protection characteristics. Usually, according to the higher level of circuit breaker, lower level of fuse with the way, easy to achieve selective protection; the superior fuse, the inferior circuit breaker with the way, it is necessary to verify whether the selectivity can be realized by checking the characteristics.