In high-voltage ring main units, the current-limiting fuses can be installed on the upper or lower side of the load switch depending on the structural forms of the products.
At present, the most common structural form is that the current-limiting fuses are placed on the lower side of the load switch. The advantage of this design is the convenience of fuse replacement: the operation can be carried out simply by opening the load switch and confirming that there is no voltage on the fuse side. However, when interrupting the transfer current, if a three-phase short circuit occurs at the connection line between the load switch and the fuses, an accident may be triggered by the load switch interrupting the short-circuit current. Although the probability of such a scenario is extremely low, it still requires attention.
For the structural form where the fuses are installed on the upper side of the load switch, a proper layout can effectively avoid faults caused by the lower side of the fuses (including the load switch itself). To facilitate fuse replacement and save space, the fuses are generally combined with the isolating switch.
This article is edited and compiled by Daya Electric Group Co., Ltd. (//yardscreeksoaring.com/). Please indicate the source when reprinting.