1、 Reasonable selection of drop out fuse

10kV drop fuse is suitable for the environment without conductive dust, corrosive gas, inflammable, explosive and other dangerous environment. The annual temperature difference ratio is less than ± Outdoor places within 40 ℃.

The selection is based on the 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 shall be greater than or equal to the rated current of the melt. The rated current of the melt can be 1.5-2 times of the rated load current.

In addition, the selected fuse shall 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 (generally refers to its upper limit) is too large, it is likely that the three-phase short-circuit capacity of the protected system is less than the lower limit of the rated breaking capacity of the fuse, which makes it difficult to extinguish the arc when the fuse is fused, and eventually causes the fuse tube burning, explosion and other accidents.

2、 Correct installation of drop out fuse

1. 10kV drop out fuse shall be installed outdoors, and the phase to phase distance shall be greater than 70cm. And it is firmly and reliably installed on the cross arm (frame) with a vertical distance of not less than 4m from the ground, without any shaking or shaking phenomenon. If it is installed above the distribution transformer, a horizontal distance of more than 0.5m should be kept from the outermost contour boundary of the distribution transformer, so as to prevent other accidents caused by the falling of the molten tube.

2. During the installation, the melt should be tightened, otherwise it is easy to cause contact heating. The melt used must be the standard product of the regular manufacturer with certain mechanical strength.

3. The fusion tube should be downward 25 °（± two °） The length of the melting tube should be adjusted appropriately. It is required that the duckbill tongue can hold more than two-thirds of the length of the contact after switching on, so as to avoid the misoperation of self falling during operation. The melting tube should not hold the duckbill to prevent the melting tube from falling in time after melting.

3、 Normal and reasonable operation of drop out fuse

The branch lines of 10kV distribution lines and distribution transformers with rated capacity less than 200KVA in rural power grid are allowed to operate with load according to the following requirements:

1. The operation shall be carried out by two persons (one for supervision and the other for operation), but they must wear qualified insulating gloves, insulating boots and eye protection glasses, and use qualified insulating rod with matching voltage level for operation. It is forbidden to operate in the climate of lightning or heavy rain.

2. During the switching operation, it is generally stipulated that the intermediate phase is pulled off first, then the leeward side phase is pulled off, and finally the windward side phase is pulled off. From: home of Electrical Technology

Because the distribution transformer is changed from three-phase operation to two-phase operation, the arc spark generated by breaking the middle phase is the smallest, which will not cause phase to phase short circuit. The second is to break the leeward side phase. Because the middle phase has been pulled apart, the distance between leeward side phase and windward side phase has doubled. Even if there is overvoltage, the possibility of phase to phase short circuit is very small. Finally, when the windward side phase is pulled off, there is only capacitive current to the ground, and the spark is very slight.

3. When switching on, the operation sequence is opposite. When switching on, first close the windward side phase, then close the leeward side phase, and finally close the middle phase.

4. It is a frequent project to operate the melting pipe. If it is not noticed, the contact will be burned, resulting in poor contact, overheating the contact, annealing the spring, making the contact worse, forming a vicious circle.

Therefore, when pulling and closing the fusion tube, the force should be moderate. After closing, it is necessary to carefully check that the duckbill tongue can tightly clasp more than two-thirds of the length of the tongue. You can hook the upper duckbill with a brake rod and press it down a few times, and then gently pull it to check whether it is closed. When the switch is not in place or firmly closed, the pressure of the static contact on the fuse is insufficient, which is very easy to cause the contact burn or the fuse tube to drop.

4、 Strengthen the operation and maintenance of drop out fuse

In order to make the fuse operate more reliably and safely, in addition to strictly selecting the qualified products and accessories (including fuses, etc.) produced by regular manufacturers according to the regulations, special attention should be paid to the following matters in the operation and maintenance management:

1. Whether the rated current of the fuse matches the melt and load current properly, if not, it must be adjusted.

2. Each operation of the fuse must be careful, 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 are abnormal phenomena such as corrosion and ineffective rotation, whether the parts are damaged, and whether the spring is corroded.

3. The standard melt must be used in the melting pipe. It is forbidden to replace the melt with copper wire and aluminum wire. Moreover, it is forbidden to use copper wire, aluminum wire and iron wire to bind the contact.

4. For the newly installed or replaced fuse, it is necessary to strictly check and accept the process, which must meet the quality requirements of the regulations, and the installation angle of the fuse pipe must reach 25 ° Left and right dip angle.

5. After the melt is fused, it should be replaced with a new melt of the same specification. It is not allowed to connect the fused melt and then put it into the melt pipe for further use.

6. The fuse should be inspected regularly, not less than once a month at night, to check whether there is spark discharge and poor contact. If there is discharge, it will be accompanied by a hissing sound, so it should be arranged as soon as possible.