What are the preventive measures for common failures of drop-out fuses?

1. Reasonable choice of drop-out fuse

The 10kV drop-out fuse is suitable for outdoor places where the ambient air has no conductive dust, no corrosive gas, flammable, explosive and other dangerous environments, and the annual temperature difference ratio is within ±40℃. The selection is based on the two parameters of rated voltage and rated current, that is, the rated voltage of the fuse must match the rated voltage of the protected equipment (line). The rated current of the fuse should be greater than or equal to the rated current of the melt. The rated current of the melt can be 1.5 to 2 times the rated load current. In addition, the selected fuse should be checked according to the three-phase short-circuit capacity of the protected system. Ensure that the three-phase short-circuit capacity of the protected system is less than the upper limit of the rated breaking capacity of the fuse, but must be greater than the lower limit of the rated breaking capacity. If the rated breaking capacity of the fuse (usually the upper limit) is too large, it is likely that the three-phase short-circuit capacity of the protected system will be less than the lower limit of the rated breaking capacity of the fuse, which will make it difficult to extinguish the arc when the melt is blown, which will eventually cause Accidents such as burnt pipes and explosions.

2. Install the drop-out fuse correctly

(1) The 10kV drop-out fuse is installed outdoors, and the distance between phases should be greater than 70cm. And it is firmly and reliably installed on a cross arm (frame) with a vertical distance of not less than 4m from the ground. The European-style cable connector must not have any shaking or shaking. If it is installed above the distribution transformer, it should maintain a horizontal distance of more than 0.5m from the outermost contour boundary of the distribution transformer to prevent the fuse tube from falling and causing other accidents.

(2) The melt should be tightened during installation, otherwise it is easy to cause contact with the hair. The melt used must be a standard product of a regular manufacturer and have a certain mechanical strength.

(3) The fusion tube should have an inclination angle of 25° (±2°) downward, and the length of the fusion tube should be adjusted moderately. It is required that the duckbill tongue can buckle more than two-thirds of the length of the contact after closing, so as to avoid running In the event of spontaneous fall, the fusion tube must not be dead on the duckbill to prevent the fusion tube from falling down in time after the melt is blown.

3. Operate the drop-out fuse normally and reasonably

In rural power grids, 10kV distribution line branch lines and distribution transformers with rated capacity less than 200kVA are allowed to operate with load according to the following requirements:

(1) The operation is carried out by two persons (one person for supervision, one person for operation), but must wear insulated gloves that have passed the test, wear insulated boots, and wear goggles. Use qualified insulated rods with matching voltage levels to operate. Operation is prohibited under heavy rain.

(2) When opening the gate, it is generally stipulated that the middle phase is pulled off first, then the side phase leeward is pulled, and the side phase facing the wind is pulled off finally. This is because the distribution transformer is changed from three-phase operation to two-phase operation, and the arc spark generated when the middle phase is broken is the smallest, which will not cause a short circuit between phases. The second is to pull off the leeward side phase. Because the middle phase has been pulled apart, the distance between the leeward side and the windward side has doubled. Even if an overvoltage is generated, the possibility of a short circuit between the phases is very small. When the windward side phase is finally pulled off, only the capacitive current to the ground is generated, and the spark produced is already very slight.

(3) When closing, the operating sequence is reversed when opening the brake, first close the windward side phase, then close the leeward side phase, and finally close the middle phase.

(4) The operation of the fusion tube is a frequent item. If it is not noticed, it will cause contact burns and poor contact. The contacts will overheat and the spring will be annealed. This will cause the contacts to be more poorly contacted, forming a vicious circle. European-style cable connector, therefore, use moderate force when pulling and joining the fusion tube. After closing, carefully check that the duckbill tongue can be tightly clasped by more than two-thirds of the length of the tongue, and the upper duckbill can be hooked down by the pull lever. After a few clicks, try to pull gently to check if it fits properly. Failure to be in place or not securely closed when closing, the static contact pressure on the fuse is insufficient, which can easily cause contact burns or the fuse tube to fall by itself.

4. Strengthen the operation and maintenance of drop-out fuses

In order to enable the fuse to operate more reliably and safely, in addition to strictly selecting qualified products and accessories (including fuses, etc.) produced by regular manufacturers in accordance with the requirements of the regulations

Special attention should be paid to the following matters in operation and maintenance management:

(1) Whether the rated current of the fuse is matched with the melt and load current value is appropriate, if the match is not proper, it must be adjusted.

(2) Each operation of the fuse must be careful and not careless, especially the closing operation, the moving and static contacts must be in good contact. Check whether the rotating part of the fuse is flexible, whether there is any abnormality such as rust, rotation failure, etc., whether the parts are damaged, and whether the spring is rusted.

(3) Standard melt must be used in the melting tube. It is forbidden to replace the melt with copper wire and aluminum wire, and it is not allowed to use copper wire, aluminum wire and iron wire to tie up the contacts.

(4) For newly installed or replaced fuses, the acceptance process must be strictly checked, and the quality requirements of the regulations must be met. The installation angle of the fuse pipe must reach an inclination angle of about 25°.

(5) After the melt is fused, it should be replaced with a new melt of the same specification, and the fused melt should not be connected and then loaded into the fuse tube for continued use.

(6) The fuse should be inspected regularly, and no less than once a month at night to check for discharge sparks and poor contact. If there is a discharge, it will be accompanied by a hissing sound. Arrange for treatment as soon as possible.

Yichang Hengyuan Technology Co., Ltd. is a professional manufacturer of European-style cable connectors, plug connectors, cable branch boxes, American elbow connectors, high-voltage vacuum circuit breakers, high-voltage load switches, lightning arresters, zinc oxide arresters, tank arresters, overvoltage protectors, Counters, monitors, heat-shrinkable cable accessories, cold-shrinkable cable accessories, T-shaped heads, wall bushings, European cable accessories, American cable joints, transformer neutral point protection devices, fuses, isolating switches, PT cable heads, elbows Manufacturers of type cable joints, 10kV outdoor terminals, switch cabinets, cable intermediate joints, cable accessories and other products