Precautions for the hottest operation of drop fuse

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Precautions when operating drop fuse

in extensive practice, through the continuous summary of the operation of high-voltage drop fuse, it is found that when the three-phase load disconnects the first phase, the fracture voltage is low and the arc is small; When the second phase is disconnected, the fracture voltage is high, and a strong arc often appears after the circuit is disconnected, which is easy to short circuit the adjacent phase; At last, when the third phase is pulled, because the circuit has no current, there will be no arc. Therefore, it seems that the second phase is the key to ensure safety. In addition, the impact of air flow (wind, wind direction) on the safety of operation is also obvious. When the air flow lengthens the arc, it may cause phase to phase short circuit, cause large arc light, and endanger the safety of operators

the general drop fuse has no arc suppression device, so when the transformer is powered off, in order to prevent the arc burn accident, it should avoid switching off with load. In case of power failure of the transformer, first pull the shunt (Branch) switches on the low-voltage side, then pull the main switch of the low-voltage line, and finally pull the high-voltage fuse of the transformer. The operation sequence of transformer power transmission is opposite. In order to prevent misoperation, check whether the low-voltage switch is in the off position before pulling and closing the high-voltage fuse

rw-10f drop out fuse is equipped with arc extinguishing cover and arc extinguishing contact, which can pull and turn on the transformer. Personalized customization will bring the rated current of the order of the disperser. Therefore, it is not limited by the above operation sequence. For the sake of safety, when operating the high-voltage drop fuse, the staff should pay attention to the following:

(1) when opening the drop fuse, the operator must use an insulating rod with a suitable voltage grade and passing the test, wear insulating shoes, insulating gloves, insulating caps and goggles, or stand on a dry wooden platform, and be supervised to ensure personal safety

(2) the operator shall not have impact at the beginning or end of pulling and closing the drop fuse. The impact will damage the fuse, such as breaking and cracking the insulator, deflecting the duck beak, pulling and breaking the operating ring, etc. Therefore, when opening and closing the drop fuse, the staff must not exert too much force and impact to avoid damaging the fuse, and the opening and closing must be in place

the force in the process of closing the fuse is slow (at the beginning) fast (when the moving contact is close to the static contact) slow (when the moving contact is close to the closing end). The process of pulling the fuse is slow (at the beginning) and fast (when the moving contact is close to the static contact) and slow (when the moving contact is close to the end of pulling the switch). Fast is to prevent electric short circuit and contact burns caused by electric arc, and slow is to prevent mechanical damage of fuse caused by operating impact

(3) operation sequence of power off and transmission of distribution transformer: in general, in case of power failure, the low-voltage switch on the load side should be opened first, and then the high-voltage drop fuse on the power side should be opened

① in the case of multiple power supplies, the power failure in the above sequence can prevent the reverse power transmission of the transformer. In case of fault, the protection may refuse to operate, prolong the fault removal time, and expand the accident

② when purchasing from the power supply, the power transmission operation is carried out step by step at the same time to facilitate people and stimulate consumption, which can reduce the impact starting current (load), reduce voltage fluctuations, and ensure the safe operation of the equipment. In case of fault, it can immediately trip or stop the operation, which is convenient for inspection, judgment and treatment according to the power transmission range

③ when the power is cut off, stop the load side first, and the step-by-step power-off operation sequence from low voltage to high voltage can avoid the switch cutting off a large amount of current and reduce the amplitude and times of operating overvoltage. Try to avoid pulling and closing the drop fuse with load during operation. If the fuse is wrongly closed with load during operation, even if it is wrongly closed, or even an arc occurs, it is not allowed to pull the fuse apart again. If the fuse is pulled incorrectly with load, an arc will occur when the moving contact just leaves the fixed contact. 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 opened, do not close the fuse pulled by mistake. However, for distribution transformers with a capacity of 200KVA and below, the fuse on the high-voltage side is allowed to open and close the load current

(4) three phase operation sequence of high voltage drop out fuse:

① during power failure operation, pull the intermediate phase first, and then the two sides. During power transmission, the phases on both sides shall be closed first, and then the intermediate phase. The reason why the middle phase is pulled first in case of power failure is that the current when the middle phase is cut off is smaller than that of the side phase (part of the load of the circuit is transferred to two phases), so the arc is small and there is no danger to both phases. When operating the second phase (side phase) drop fuse, the current is large, and at this time, the middle phase has been opened. The other two drop fuses solve the difficulties that have plagued the development of the enterprise for a long time, and the distance is relatively far, which can prevent the arc from lengthening and causing phase to phase short circuit

② in case of strong wind, the power shall be cut off in the order of pulling the intermediate phase first, then the leeward phase, and finally the windward phase. During power transmission, the windward phase shall be closed first, then the leeward phase, and finally the intermediate phase, so as to prevent short circuit caused by wind blown arc

(5) generally, do not operate the drop fuse in rainy or snowy days. When it is necessary to operate, an insulating rod with a rain cover should be used. In case of lightning, it is strictly forbidden to operate the drop fuse and replace the fuse

(6) in case of any doubt or abnormal failure of the tensile testing machine material testing machine such as elastic modulus, strength and plasticity during operation, the operation shall be stopped and the operation can be continued only after the problem is found out. The purpose of stopping operation is not to allow blind operation in case of doubt. The fault is obvious, and generally the operation should be stopped. The equipment is abnormal. When the transformer has signs of serious failure (abnormal sound, oil injection, etc.), abnormal sound, abnormal light (spark), abnormal indication of indicating instrument or relay, abnormal smell, etc., in case of these conditions, the operation of high-voltage drop fuse should be stopped to find the cause

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