Outdoor Overhead Line Distribution Type Expulsion Drop-out Fuse Cutout with KEMA Certification

Outdoor drop out fuses are suitable for use in AC 50HZ, rated voltage 10KV power systems, as overload and short-circuit protection for transmission and distribution lines and power transformers, as well as for opening and closing rated load currents.

The widely used outdoor drop out fuses generally come in three types: RW7, RW11, and RW12.

Application Environment

10kV drop out fuses are suitable for outdoor environments with no conductive dust, no corrosive gases, and hazardous environments such as flammability and explosiveness. The annual temperature difference ratio is within ± 40 ℃. The selection is based on two parameters: rated voltage and rated current, which means that the rated voltage of the fuse must match the rated voltage of the protected equipment (line).

Operation precautions

Under normal circumstances, it is not allowed to operate drop out fuses with load, only allowed to operate unloaded equipment (lines). However, branch lines of 10kV distribution lines in rural power grids and distribution transformers with a rated capacity of less than 200kVA are allowed to operate with load according to the following requirements:

(1) Two people are responsible for the operation (one for supervision and one for operation), but they must wear tested and qualified insulated gloves, insulated boots, goggles, and use qualified insulated rods with matc

hing voltage levels for operation. Operation is prohibited in climate with lightning or heavy rain.

(2) When pulling the brake, it is generally stipulated to first pull off the middle phase, then pull off the leeward side phase, and finally pull off the windward side phase. This is because the distribution transformer has changed from three-phase operation to two-phase operation, and the arc spark generated when the middle phase is pulled off is minimized, which does not cause a phase to phase short circuit. Next is to break the leeward phase, as the middle phase has been pulled apart and the distance between the leeward phase and the windward phase has doubled. Even if overvoltage occurs, the possibility of a phase to phase short circuit is very small. When the windward phase is finally broken, only the capacitive current to ground is generated, and the electric spark produced is already very slight.

(3) When closing the circuit breaker, the operation sequence is reversed when closing the circuit breaker. First, close the windward side phase, then close the leeward side phase, and finally close the middle phase.

(4) Operating the melting tube is a frequent task, and if not noticed, it can cause contact burns and poor contact, leading to overheating of the contacts and annealing of the spring, resulting in even worse contact and forming a vicious cycle. So, when pulling and closing the melting tube, moderate force should be applied. After closing, carefully check that the duckbill tongue can tightly grasp more than two-thirds of the tongue length. You can use a brake lever to hook the upper duckbill and press it down a few times, then gently try pulling to check if it is closed properly. Failure to close in place or securely, insufficient pressure on the static contacts of the fuse, can easily cause contact burns or the fuse tube to fall off on its own.