10kV drop-out fuse cutout the use and operation and maintenance

   Drop-10kV distribution line fuse is the branch line and distribution transformers of the most commonly used as a short-circuit protection switch, which has an economic, convenient operation, to adapt to the outdoor environment and strong characteristics, are widely used in 10kV distribution line and distribution transformer primary side as a protection and for equipment investment, cut operational purposes. It is installed on a 10kV distribution line branch line, can narrow the scope of power outages, because there is a clear break point, with the isolation switch functionality, to the maintenance section lines and equipment to create a secure operating environment, an increase of maintenance personnel sense of security. Installed in the distribution transformer can be used as the primary protection of distribution transformers, therefore, in the 10kV distribution line and distribution transformers have been popular. The working principle is: fuse tube fuse on both ends of the moving contacts (melt) is tight, the moving contacts will be pushed into the "Duckbill" protruding parts, the P-Cu films and static touch on the head made of with the moving contacts and therefore I fuse tube firmly stuck in the "Duckbill" Lane. When the short-circuit current through the fuse when the fuse to produce arc, fuse steel pipe lined with paper tube in the arc under the action of a large number of gas produced by the upper fuse tube was sealed, the gas down the side exhaust, blowing out the arc. As the fuse fuse, fuse tubes fuse to lose contact moving up and down the tie-down force, the fuse control their own gravity and the upper and lower static contact spring pieces under the action of the rapid drop tube fuse, so that the circuit disconnect , cut line or a faulty device fault section.

In reality, the system of rural power lines 10kV and distribution transformer fuses can not be the correct action, one of the reasons is the poor quality of agricultural electrician, sense of responsibility is not strong, all year round without falling type fuse of the maintenance and repair; causes The second is the drop-fuse cutout the poor quality of products and can not pull a flexible, co-operation. Two reasons for reducing the drop-out fuse functions. Reality often lack melt pipes, lack of melt or copper wire, aluminum wire hooks hanging wire instead of the melt even circumstances. Makes the trip circuit failure rate and high rate of distribution transformers. 

1 on the drop-out fuse cutout device Analysis of defects 

(1) Product process rough, manufacture of poor quality, lack of contact spring elasticity, resulting in poor contact and the contact sparks overheating. 

(2) The manufacture of fused pipe rotation axis rough inflexible, so that melting point reach a point of order management requirements, in particular, with the majority of the melting tube size reach a point of order requirements, melting the top tube is too long will die of robbery, resulting in melt After the melting tube fuse is not promptly drops, promptly arc cut off, resulting in melting tube burning or explosion; melting tube size is short, closing the difficulties, the contact being exposed to produce spark. Guang-Ling Electric Power Bureau, "6.7" accident on the part of such reasons, resulting in staff irritable heart, Shannian a melting pipes with hand-closing dynamics of electrocution death occurred.

(3) Disconnect the fuse rated capacity is small, its lower limit of less than three-phase short-circuit protected system capacity. At present, 10kV outdoor falling fuses are divided into three kinds of models, namely, 50A, 100A, 200A. 200A Drop-fuse breaker capacity limit is 200MVA, is a minimum of 20MVA. Interdiction capacity in accordance with its capabilities, we can easily see that the melt fuse short-circuit fault interrupter after can not be timely, but also tends to melt tube burning or explosion.

(4) some of the new switch fuses melt pipe size and the fixed contact part of the size match is inappropriate, easy to loose, in operation, when faced with external force, vibration, or strong winds, it will malfunction and fall on their own, not only reduced the sales electricity, but also difficult to ensure power supply reliability rate target. The presence of defects in several aspects, not only increased the workload of maintenance personnel, but also contributed to the maintenance personnel (especially for farmers, electricians) and improper use, completely lost their drop-out fuse due protection, short-circuit in the circuit can only be extended power outage, leapfrog to the total qualifying 10kV substation circuit breaker tripped, resulting in full-line blackout. 

2 pairs of drop-out fuse cutout (switch) the choice of 

10kV drop-out fuse cutout applied to ambient air non-conductive dust, no corrosive gases and flammable, explosive and other dangerous environments, the annual temperature changes of less than ±  40 ℃  than at outdoor venues. Of their choice is based on rated voltage and rated current of two parameters, that is, the rated voltage of fuse must be protected equipment (lines) of the rated voltage of match. Fuse with the rated current should be greater than or equal to the melt of the rated current. The melt rated current options for the rated load current of 1.5 ~ 2 times. In addition, three-phase short-circuit protection system should be the capacity of the selected fuse for checking. Three-phase short-circuit protection systems ensure that the capacity is less than the maximum capacity of fuses rated disconnect, it must be greater than the rated capacity of the lower limit of disconnect. If the fuse disconnect rated capacity (generally refers to the upper limit) is too large, is likely to be three-phase short-circuit protection system disconnected capacity of rated capacity of less than the lower end of fuse, resulting in difficulty in melt fuse interrupter when the final caused by melting tube burning, explosion and other accidents. At present, some still in the rural power supply unit transformation peak, in the selection of such fuses must strictly control product quality, protection of equipment qualified network, while noting the disconnect of its rated capacity of the upper limit and lower limit. 

3 Installation of three drop fuse cutout

(1) Installation should be to melt tension (to melt the tension about being around 24.5N), otherwise easily lead to heat contact. 

(2) fuse installed in the horizontal Tam (architecture) should be solid and reliable, can not have any shaking or shaking phenomenon.

(3) melting down the pipe should be 25 °  ±  2 °  of inclination, to facilitate the melt when the melt fuse tube can quickly drop the weight on their own. 

(4) fuse should be installed in the vertical distance from the ground is not less than 4m cross-Tam (architecture), on top of that if installed in the distribution transformer, distribution transformer should outline the borders of the outermost horizontal distance of more than 0.5m in order to Anti-melt tube case raised other incidents fall. 

(5) the length of the tube should be adjusted melting moderate demands, after closing Ischaemum tongue can withhold more than two-thirds of the length of contact in order to avoid falling on their own place in the operation of the malfunction, melting the top tube should not die Ischaemum in order to prevent the melt after the melt fuse tube can not be timely fall. 

(6) used by the melt must be regular factory standard products, and has a certain degree of mechanical strength, generally require more than the melt at least able to withstand the pull of 147N. 

(7) 10kV drop-out fuse installed in the outdoor demanding phase distance greater than 70cm. Reposted elsewhere in the paper for free download 

4 drop-out fuse cutout operation 

Under normal circumstances do not allow operation with a load of drop-out fuse, only allow it to operate no-load equipment (lines). But in Rural 10kV distribution line branch line and the rated capacity of less than 200kVA distribution transformer allow the load operation in accordance with the following requirements: 

(1) operation carried out by the two (one monitoring, one operator), but must be worn by the pilot qualified insulating gloves, wear insulated boots, goggles, use the voltage level to match qualified insulation rod operation, in the thunder and lightning, or Prohibition of operation of a climate of heavy rain. 

(2) wind up its operations, the general rule is first pulled off the middle phase, and then pull back side of the wind phase, the final-phase pull off the windward side. This is because the distribution transformer to run from the three-phase to two-phase operation, pull off the middle-phase arc spark generated when the minimum will not result in white short-circuit. Followed by the leeward side pull-off phase, because the intermediate phase has been opened, the leeward side of phase and relative distance from the windward side has doubled, even over-voltage generated, resulting in the possibility of inter-phase short-circuit is small. Pull off the windward side of the final phase, the only-to-ground capacitance current, generated by electric spark already are mild.

(3) The closing time of operation wind up in the opposite order, first-phase co-wind side, and then combined leeward side compared and finally close the intermediate phase. 

(4) Operating melt pipe is a frequent project, attention will result in less contact burns caused by being exposed to contact overheating, spring annealing to promote access to even more bad contact, forming a vicious cycle. So, pull, co-melting tube when a moderate force, He Hao, after carefully checking Ischaemum the length of the tongue to closely link with two-thirds of the tongue, can wind up Ischaemum downward pressure on the rod hook several times, and then gently pull test to check Gehao. Closing failed to put in place or combined solid, static contact pressure to fuse the lack of contact burn or melt easily create their own drop tube. 

5 drop-out fuse cutout operation and maintenance management 

(1) In order to fuse more reliable, safe operation, in addition to the formal selection of a point of order demanding manufacturers of qualified products and accessories (including fused pieces, etc), in the operation and maintenance management should pay particular attention to the following matters: 

①  fuse with rated current and the melt and load current values match fit, if the mis-match must be regulated. 

②  fuse each operation carefully to be careful and not careless, especially the closing operation, must be made dynamic and static contact good contact.

③  melting tube must use the standard melt, prohibit the use of copper wire aluminum wire instead of the melt, but are not allowed to use copper wire, aluminum wire and the wire would contact the use of banding to live.

④  on the new installation or replacement of the fuse must be strictly inspection processes, procedures must meet the quality requirements, melting pipes installed about 25 °  angle of tilt to reach the bottom corner. 

⑤  After the melt fuse to be replaced with the new specifications melt can not melt the fuse link up again after the tubes into melting continued use.

⑥  should periodically conduct inspections of the fuse, at least once a month night-time inspections to detect sparks and access to undesirable phenomenon, there are discharge, will be accompanied by the sound of hissing, it is necessary as soon as possible arrangements. 

(2) maintenance outage in the spring when the inspection should fuse to do the following checks:

①  static and dynamic contact exposure is consistent, close well, whether it has burn marks. 

②  rotating parts fuse is flexible, it has rust, rotational flow problems and other abnormalities, parts for damage, spring has rust. 

③  melt itself whether there was damage, whether the heat after a long period of power has become lax unable to stretch too much. 

④  After repeated melting pipe gas pipe moves with the arc tube is exposed to the sun and rain after the burn, and whether the damage deformation, the length is shortened. 

⑤  clean insulators and check whether the damage, cracks or signs of discharge, apart the upper and lower lead after the shake table test with 2500V insulation resistance should be greater than 300MΩ . ⑥  check the fuse wire to connect the upper and lower availability of loose, discharge, overheating. 

Check out the above-mentioned shortcomings of the project must deal with serious overhaul. Reposted elsewhere in the paper for free download.