In electrical construction, improper connection of drop-out fuse leads can lead to issues ranging from poor contact and overheating to complete wire breakage. By clearly understanding the routing for the upper and lower terminals and following a systematic procedure, you can ensure a correct installation on the first attempt.
I. Preparation and Tools
Before beginning, ensure that the power is disconnected and all necessary safety measures are in place. Prepare the required insulated conductors (ensuring the cross-sectional area meets current-carrying capacity requirements), crimping tools, bolts, and other necessary hardware. Different fuse capacities have specific requirements for conductor cross-sections; for 10kV systems, 70mm² or 95mm² insulated conductors are commonly used, with the exact size determined by the load current. A common best practice in the field is to strip the ends of the conductors and attach the appropriate cable lugs beforehand, which helps avoid complications and haste during on-site installation.
II. Key Wiring Steps and Criteria
① Distinguish between upper and lower leads: The fuse unit consists of an upper stationary contact and a lower moving contact. The upper lead typically connects to an overhead line or busbar, while the lower lead connects to a distribution transformer or other load. Ensure that the connections are correctly matched; reversing them is strictly prohibited.
② Secure the upper lead: Insert the upper lead into the terminal hole of the upper stationary contact and fasten it using the designated bolts and spring washers. Verification: Once tightened, gently shake the conductor by hand; it is considered secure if there is no sign of looseness. If using a hydraulic crimping tool to attach cable lugs, ensure that the crimping die matches the lug specifications and that no cracks appear after crimping.
③ Secure the lower lead: Connect the lower lead to the terminal block of the lower moving contact. Ensure the lead hangs naturally; avoid excessive tension, which could cause the contact to deform. Verification: The conductor should have a smooth, gradual bend without any sharp angles or creases, and it must maintain an adequate safety distance from any surrounding live components.
III. Critical Post-Installation Checks
The work is not complete simply because the connections have been made. It is essential to check the flexibility of the fuse tube installation to ensure it can drop freely. At the same time, verify that the clearances between the lead wires and the ground, as well as between phases, comply with safety standards; this prevents short circuits caused by leads that are either too loose or too tight.