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Date：08-05-2021
Safety preparation:
When pulling out the drop type fuse, the operator must use the insulation rod with suitable voltage level and passed the test, wear insulation shoes, insulation gloves, insulation cap and goggles, or stand on a dry wooden platform, and be supervised to protect personal safety.
Notes:
When the operator starts or ends the pull or close drop fuse, there shall be no impact.The impact will damage the fuse, such as pulling and cracking the insulator, deflecting the duck bill, pulling and breaking the operation ring, etc.The staff should not exert too much force during the operation of the drop type fuse, so as to avoid damage to the fuse, and the splitting and closing must be in place.
The process force of the fuse is slow (start)- fast (when the moving contact is near the static contact)- slow (when the moving contact is near the end of closing).The process of pulling the fuse is slow (start)- fast (when the moving contact is near the static contact)- slow (when the moving contact is near the end of the pull).Fast is to prevent electrical short circuit and burn contacts caused by arc, slow is to prevent the operation of impact force, causing mechanical damage to the fuse.
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The sequence of operation for stopping power supply of the distribution transformer is as follows: Under normal circumstances, the low-voltage switch on the load side should be pulled first, and then the high-voltage drop fuse on the power side should be pulled.
In the case of multiple power supply, according to the above sequence of power outage, can prevent transformer back transmission, in case of failure, protection may refuse to move, prolong the fault removal time, make the accident expand.Step by step transmission operation from the power supply side can reduce the impact starting current (load), reduce voltage fluctuation, and ensure the safe operation of the equipment.In case of fault, can immediately trip or stop the operation, easy to check, judge and deal with according to the power range.In the case of power failure, stop the load side first. In the operation sequence of power failure step by step from low voltage to high voltage, the switch can avoid cutting off large current flow and reduce the amplitude and frequency of operation over voltage.
In the operation, try to avoid pulling and dropping fuses with load. If it is found that the fuses with load are misaligned during the operation, even if the fuses are misaligned or even arc occurs, it is not allowed to open the fuses again.If the wrong pull fuse with load occurs, when the moving contact just leaves the fixed contact, an arc will occur. At this time, it should be closed immediately to eliminate the arc and avoid the expansion of the accident.However, if all fuses have been pulled open, it is not allowed to re-close the mistakenly pulled fuses.For distribution transformers with a capacity of 200 kva or less, the fuses on the high voltage side are allowed to separate and combine the load current.
Operating sequence
Three phase operation sequence of high voltage drop fuse.
Power failure operation, should first pull the middle phase, then pull both sides of the phase.
The main reason for pulling the middle phase first is to consider that the current when the middle phase is cut off is less than the side phase (a part of the circuit load is carried by the two phases), so the arc is small, and there is no danger to the two sides of the phase.When the second phase (side phase) drop type fuse is operated, the current is larger, while the middle phase has been pulled open, and the other two drop type fuses are far away from each other, which can prevent the short circuit between phases caused by the elongated arc.When there is a strong wind, we should first pull the middle phase, then pull the lee phase, and finally pull the windward phase in the order of power failure.
When sending electricity, the two sides of the first phase, after the middle phase.
When the power is transmitted, the first wind phase, then back to the phoenix phase, and finally the middle phase, so as to prevent the short circuit caused by the wind arc.
The installation note
Precautions for installation of high voltage drop fuse
1, the installation should be the melt tension (melt by about 24.5N tension), otherwise easy to cause touch hair heat.
2, the fuse installed on the cross arm (frame) should be firm and reliable, can not have any shaking or shaking phenomenon.
3. The melting pipe should have a dip Angle of 25°±2°, so that the melting pipe can fall rapidly by its own weight when the melt is fused.
4. The fuse should be installed on the cross arm (frame) with a vertical distance of no less than 4m from the ground. If it is installed above the distribution transformer, it should keep a horizontal distance of more than 0.5m from the outermost contour boundary of the distribution transformer, in case of other accidents caused by falling molten pipes.
5. The length of the melting pipe should be adjusted appropriately. It is required that the duck mouth tongue can buckle more than two thirds of the length of the contact after closing, so as to avoid the wrong action of falling by itself during operation.
6. The melt used must be the standard product of the regular manufacturer, and has a certain mechanical strength. Generally, the melt can withstand the tensile force of more than 147N at least.
7. 10kV drop type fuse is installed outdoors, and the distance between phases is greater than 70cm.
