Operation and Maintenance:

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

①Whether the rated current of the fuse device matches the melt and load current values ​​properly, and adjustments must be made if the matching is not appropriate.

②Each operation of the fuse must be careful and not careless, especially the closing operation, the moving and static contacts must be in good contact.

③Standard melt must be used in the melt tube. It is forbidden to use copper wire and aluminum wire instead of melt, and it is not allowed to use copper wire, aluminum wire and iron wire to tie up the contacts.

④ For newly installed or replaced fuses, the acceptance process must be strictly checked and the quality requirements of the regulations must be met. The installation angle of the fuse pipe must reach an inclination angle of about 25°.

⑤After the melt is blown, it should be replaced with a new melt of the same specification, and the blown melt should not be connected and then inserted into the fuse tube for continued use.

⑥ The fuse should be inspected regularly, and no less than once a month at night to check for discharge sparks and poor contact. If there is a discharge, it will be accompanied by a hissing sound. Arrange for treatment as soon as possible.

(2) The fuse should be checked for the following contents during the power failure during the spring inspection:

①Whether the static and moving contacts are in good agreement, and whether there are burn marks.

②Whether the rotating parts of the fuse are flexible, whether there are abnormalities such as rust and rotation failure, whether the parts are damaged, and whether the spring is rusted.

③Whether the melt itself has been damaged, whether it has become loose and weak due to excessive heat and elongation after long-term electrification.

④Whether the arc extinguishing tube for gas production in the tube is burned after repeated actions, whether it is damaged or deformed after sun and rain, and whether the length is shortened.

⑤Clean the insulator and check for damage, cracks or discharge marks. After disassembling the upper and lower leads, use a 2500V shake meter to test the insulation resistance should be greater than 300MΩ.

⑥Check whether the upper and lower connecting leads of the fuse are loose, discharged, or overheated.

The defects detected in the above items must be carefully checked and repaired.

Failure analysis:

Cause Analysis

The fuse is abnormally blown. The fuse blows and causes the tube to drop. In theory, the fuse protection has played a role. However, it can be clearly seen from the statistical graphs of previous years that abnormal fusing has time and climatic rules, which are reflected in the July to August of each year. The temperature is high, the electricity load is large, and the distribution transformer load rises quickly. Fuse tube failure occurs frequently. This shows that the fuse is abnormally blown. The reasons are as follows: (1) The fuse capacity and the distribution transformer capacity are not properly configured and fail to meet the technical standards for fuse configuration. (2) The quality of the fuse is not close, and the fusing characteristic is relatively poor.

It can be seen from the statistical charts of previous years that there is no special time rule and climate rule for the fuse tube drop due to rolling damage, but from the analysis of the broken position of the fuse body, it is found that one is two fuses. The second is the fuse at the corner of the metal casting at both ends of the fuse tube. The reasons for the broken fuse are:

(1) When the bolt is tightened, the end of the fuse will revolve and break the strand along with the rotation of the bolt.

(2) Due to the concave and convex sharp edges at the corners of the metal castings at both ends of the fuse tube, after the fuse is fixed and tightened, after a period of operation, affected by mechanical vibration, the fuse is cut and broken.

When the fuse loosening fuse is used on the drop-out fuse, it is under stress for a long time. When replacing the fuse, if it is too tight or too loose, after a period of operation, due to the influence of natural environment, mechanical vibration and long-term force, the fuse will be pulled out in an over-tight state, or The fuse is elongated and loosened compared to the original replacement, causing tube drop failure. The reasons are:

(1) When replacing the fuse, the adjustment force is inappropriate.

(2) The fuse is loosely pulled out, which mainly means that the fuse body is pulled out from the crimping place with the multi-strand tail wire. Such problems are the product quality problems of the manufacturer.

(3) The drop-out fuse has been in operation for a long time, especially if the load is small for a long time, and the fuse tube has the phenomenon that the fuse is broken due to water ingress and moisture.

Device defect

(1) The product process is rough, the manufacturing quality is poor, and the elasticity of the contact spring is insufficient, resulting in poor contact and spark overheating.

(2) The manufacturing of the rotating shaft of the molten tube is rough and inflexible, which makes the angle of the molten tube fail to meet the requirements of the regulations, especially the size of most of the equipped molten tubes does not meet the requirements of the regulations. The fuse tube cannot fall down quickly after fusing, and the arc is cut off and extinguished in time, causing the fuse tube to burn or explode; the fuse tube is short in size, difficult to close, poor contact contact, and sparks.

(3) The rated breaking capacity of the fuse is small, and its lower limit is less than the three-phase short-circuit capacity of the protected system. 10kV outdoor drop-out fuse is divided into three types, namely 50A, 100A, 200A. The upper limit of the breaking capacity of the 200A drop-out fuse is 200MVA, and the lower limit is 20MVA. According to its ability to interrupt the capacity, it is not difficult to see that the arc cannot be extinguished in time after the melt is blown in the case of a short-circuit failure, and it is easy to burn or explode the fuse tube.

(4) Some new switch fuse tube size does not match the size of the fixed contact part of the fuse, and it is easy to loosen. If it encounters external force, vibration or windy weather during operation, it will accidentally move and fall, which not only reduces sales Electricity, and it is difficult to guarantee the power supply reliability index.

The existence of the above-mentioned defects not only increases the workload of the maintenance personnel, but also promotes the improper use of the maintenance personnel (especially agricultural electricians), completely losing the protection function of the drop-out fuse, and short-circuiting in the line Only the scope of the power outage can be expanded, and the 10kV outgoing main circuit breaker of the substation will be tripped, causing power outages across the entire line.