When selecting a drop-out fuse, refer to the following points:
Rated voltage: should be greater than or equal to the highest actual working voltage. For example, a 10kV distribution network can use a 10kV drop-out fuse (such as RW10-10F/100A, RW11-10F/200A, etc.).
Rated current: The rated current of the fuse should be greater than or equal to the rated current of the fuse. The rated current of the fuse is selected as follows:
-100kVA or above distribution transformer high-voltage side, select 1.5 to 2 times the rated current of the distribution transformer high-voltage side.
-100kVA and below distribution transformer high-voltage side, select 2 to 3 times the rated current of the distribution transformer high-voltage side.
Distribution transformer low-voltage side, select 1 to 1.2 times the rated current of the distribution transformer low-voltage side.
Environmental conditions: Suitable for outdoor places with no conductive dust, no corrosive gas, and no flammable, explosive and other dangerous environments in the surrounding air, and the annual temperature difference ratio is within ±40°C.
(Special environmental conditions and parameters can be customized with our company Yueyang Electric Power)
Product quality: All parts should be complete, the shaft should be smooth and flexible, the casting should be free of cracks, sand holes and rust, the porcelain body should be good, and the fuse tube should not have moisture absorption, expansion or bending.
Check short-circuit capacity: Ensure that the three-phase short-circuit capacity of the protected system is less than the upper limit of the rated disconnection capacity of the fuse, but must be greater than the lower limit of the rated disconnection capacity. If the rated disconnection capacity of the fuse is too large, the three-phase short-circuit capacity of the protected system may be less than its lower limit, resulting in difficulty in extinguishing the arc when the fuse is melted, causing accidents such as burning and explosion of the fuse tube.
Installation requirements:
-The fuse should be tightened during installation (so that the fuse is subjected to a tensile force of about 24.5N), otherwise it is easy to cause contact heating.
-The fuse should be installed firmly and reliably on the cross arm (frame) without shaking or swaying.
The fuse tube should have a downward inclination of 25°±2°, which is conducive to the fuse tube falling quickly by its own weight when the fuse is melted.
-The fuse should be installed on a cross arm (frame) with a vertical distance of not less than 4m from the ground; if 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.
-The length of the fuse tube should be adjusted appropriately, and the duckbill tongue can buckle more than two-thirds of the contact length after closing, and the fuse tube cannot block the duckbill.
-When the 10kV drop-out fuse is installed outdoors, the phase-to-phase distance should be greater than 0.7m.
Operation precautions: Generally, load operation is not allowed, and only unloaded equipment (lines) are allowed to be operated. However, in the branch line of the 10kV distribution line of the rural power grid and the distribution transformer with a rated capacity of less than 200kVA, it can be operated with load according to specific requirements. The operation must be carried out by two people (one person for supervision and one person for operation), wearing insulating gloves that have passed the test, wearing insulating boots and goggles, using qualified insulating rods that match the voltage level, and it is forbidden to operate in thunderstorms or heavy rain. When opening the switch, first break the middle phase, then the leeward side phase, and finally the windward side phase; the order is the opposite when closing the switch. The force should be moderate during operation. After closing the switch, carefully check the duckbill tongue buckling the contact to ensure good contact.
Selection example: If a distribution transformer below 100kVA has a rated current of I on the high-voltage side, the rated current of the fuse can be selected as (2~3)I; if it is a transformer of 100kVA and above, the rated current of the high-voltage side is I, and the rated current of the fuse can be selected as (1.5~2)I. For example, for a 30kVA transformer, the high-voltage side voltage is 10kV, and the current is about 1.7A by calculation, so the rated current of the fuse can be selected as 4-5A.
At the same time, it is also necessary to pay attention to the specific parameter differences of different models, such as RW series, HRW series, etc. When making actual selections, the above factors should be considered comprehensively according to the specific situation to ensure that the appropriate drop-out fuse is selected. In addition, select products of qualified quality and strictly follow the installation and operation requirements.
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