Drop-out fuse and load-drawing drop-out fuse are the outdoor high voltage protective devices. They are mounted on the high voltage side of transformer and circuit. transformer or on the main or branch distribution circuits, to protect transformers and circuit against short circuit and overload and make and break load current of transformer and circuit. Hereinto, drop-out fuse is made up of insulator support and fuse tube, its static contact is mounted at both ends of insulator support, and the moving contact is mounted at the both terminals of fuse tube that is composed of inner are extingushing tube and outer phenol aldehyde laminated paper tuber or epoxy glass cloth tube. The load-drawing dropout fuse is provided with additional reinforced auxiliary contact and arc chute, which are used to make and break the load current.
When the drop-out fuse works normally, the fuse tube forms the closing position by using the tension of fuse wire. If the system has the trouble, the fault current will cause that the fuse is blown out rapidly, and occur electric ars, the arc extinguishing tube is heated by are, to decompose much gas, and produce high pressure in the tube, longitudinally blown arc is formed along the pipeline, and the arc is extinguished for rapid lengthening. After the fuse wire is blown out, the lower moving contact misses the pulling force and turns downwards, the locking mechanism releases the fuse tube to make it drop out and form the obvious breaking position. When need to draw the load, the moving contact is drawn out with the insulating rod, at this moment, the main moving and static contacts still keep contact, if need the insulation , the contact is also drawn out with the insulating rod, meanwhile, the auxiliary contact separates, thus, elextric arc presents among auxiliary contacts is also drawn out with the insulating rod, meaning , the auxiliary contact separates, thus, elextric arc presents among auxiliary contacts, and the electric arc is extinguished.
Outline and installation
Note:Other marks refer to the following situations:
a)The product that has been improved greatly, but not the developed new product needs to be distinguished from the original model, so, it is marked with A, B, C......
b)The product that is combined with other functional units under the same variety，it is expressed with the upper case letter of Chinese phonetic alphabet of functional unit, for example:
F—with load breaking device B—with arrester
c)The derived product that is applicable for the special environment conditions is expressed with the following codes and brackts, for example:
(Th)—damp-hot zone type；(TA)—dry-hot zone type；(G)—High altitude type；(W)—Pollution resistance type
1. Altitude: ≤ 1000m;
2. Ambient temperature: -40℃ ~+40℃ ;
3. Relative humidity: daily average ≤ 95％ , monthly average ≤ 90％ ;
4.Wind speed: ≤ 35m/s
5. Earthquake intensity: ≤ 8 grade;
6.Ice thickness: ≤ 20mm
7. Installation site should be no fire and explosion danger, no chemical corrosion, no serious pollution,no severe and no salt fog.