Analysis of the Causes of High-voltage Drop-out Fuse Failure and Lead Burning

High-voltage Drop-out Fuse Failure

As one of the important equipment of power distribution lines, high-voltage drop-out fuses often have poor contact and lead blown accidents, which affect crude oil production. In response to this problem, an improved plan is proposed to change the fixed static contact bolts into a polygonal shape, and the fuse adopts a double-lead wiring method. After implementation, the problems of high-voltage drop-out fuse failure and lead blown were effectively resolved.

Since Henan Oilfield's exploration and development in 1972, the oilfield power grid has developed rapidly. At present, 54X 6-10kV power distribution lines and more than 2500 power distribution transformers have been built, which are responsible for the power supply tasks of oilfield production and living. Due to the needs of oilfield production, the distribution of the power grid presents the characteristics of many points, long lines, and wide areas. The difficulty of operation and maintenance has increased, and the factors affecting the safe operation of the power grid have increased. The number of trips accounts for more than 30% of the total number of trips. Therefore, it is more important to do a good job of analyzing the failure of the high-voltage drop-out fuse and find a solution to the problem .

Example of failure

 2000205, when the operation of wells 9 to 15 in Jianghe Oilfield was completed, when the maintenance electrician put the transformer high-voltage drop-out fuse, the contact of the drop-out fuse was poor, which caused fire, resulting in a short circuit between phases, which caused a serious main line of the Jianghe East Main Line. Burns, a power failure on the 6kV Ⅱ busbar of the substation, a load dump of 10 MW, and more than 300 oil wells were shut down. 2002211, the workover of the shallow 6 oil well in Shuanghe Oilfield was completed. After the maintenance electrician sent the high-voltage drop-out fuse insurance, the inspection was correct. When the oil well motor was started, the upper contact of the drop-out fuse was arced, the contact was burned, and the lead was burned. The quick-break protection of the Wunan Main Line tripped, causing 60 oil wells to stop production. Similar situations have occurred in other lines, causing great losses to crude oil production.

Reason analysis

1) Frequent operation of the drop-out fuse with load causes the contact to burn out and the lead wire to burn out. Oil field 6-10kV distribution transformers are distributed in fields and villages, not only for oil well production, but also for the power supply tasks of nearby villagers. Insufficient investment in advance and management can not keep up, resulting in imperfect low-voltage protection facilities (partially stolen or destroyed), coupled with irregular user wiring, more potential accidents, affecting the normal power supply of low-voltage lines. In the event of a power failure in the user line, individual users operate the drop-out fuse with load, causing the contacts to arc due to the interruption of the current, resulting in a power failure of the line.

2) The quality of the product does not meet the requirements. This is also one of the reasons for the failure of the high-voltage drop-out fuse. In recent years, with the continuous development of the national economy, the rapid development of township and village enterprises has been driven. Some township and village enterprises are engaged in the production of electrical equipment. Due to the lack of technology and strict quality management system, some unqualified products have entered the oilfield market. Analysis of the problems with the drop-out fuse. The reason for the loosening of the fixed nut of the static contact of the fuse is that the spring cushion is poor in elasticity. After the nut is tightened, the spring cushion is flattened or broken, which cannot prevent loosening. The static contact fixing screw of the drop-out fuse is under the action of the lead swing or external force during operation, the contact contact is poor, which affects the operation of the equipment.

3) The management of oil well high-voltage electrical installation projects needs to be improved. Nearly 100 new oil wells are built and put into production each year, and they are distributed in different oilfield blocks. The construction is carried out according to normal conditions, and the cycle is long, which affects the completion of crude oil production. Therefore, the construction unit Hurrying to make progress and neglecting the quality of installation, the high-voltage drop-out fuse was put into operation without careful debugging, leaving hidden dangers of accidents.

4) Environmental factors This is also one of the reasons that affect the safe operation of equipment. The high-voltage drop-out fuse of 6～10kV distribution transformer runs in the field and is affected by wind, rain and environmental pollution, which makes fasteners, washers and contacts oxidize and rust, increase contact resistance, reduce electrical conductivity, and cause high voltage drops. Type fuse contact hair heat and burn out, causing the fuse on the lead wire to burn out and other faults.

Measures Taken

3.1 General Management ① It is necessary to clarify the operating authority of the high-voltage drop-out fuse, not only to clarify the responsibilities and obligations of the management unit, and to confirm the qualification of the operator, so as to standardize the operation and avoid human factors causing operating errors. ② Strengthen power management, especially: while increasing investment in low-voltage protection facilities, implement segmented and dedicated management of power supply to villagers near the oilfield, standardize operation, avoid the random operation of high-voltage drop-out fuses, and reduce equipment and line failures rate. ③ Strictly control the quality of electrical equipment procurement and construction. In recent years, the oilfield material supply department has implemented online bidding and adopted methods such as the use of units to check the revenue database, which effectively eliminated substandards. · 182 · Mar. 2007 High Voltage Engineering Vol. 33 No. 3 Products enter the oilfield market; the supervision responsibility system is implemented for the electrical installation engineering construction, and the power supply department organizes the acceptance before the completion and commissioning to ensure the product quality and construction quality. ④Improve the quality of power grid maintenance. According to production needs, the oilfield arranges power grid maintenance in the spring of each year. In accordance with the maintenance process regulations, while doing a good job in defect processing, the focus is on the maintenance of drop-out fuses, mainly the replacement of burnt static contacts and spring washers. , Dynamic and static contact debugging. According to statistics, the workload of replacing the static contact of the drop-out fuse in the maintenance station accounts for more than half of the entire workload, which reduces the line failure rate.

3.2  Specific measures. After the above measures are taken, the problem of poor contact and heating of the drop-out fuse contact and the blowout of the lead has not been effectively solved. Then analyze the structure of the drop-out fuse: the drop-out fuse is made of copper, A combination of aluminum conductors and porcelain parts, the static contact and the porcelain part are connected by screws, and there is no limit device. Under the action of external force, the upper and lower contacts are misaligned, which affects the contact. For this reason, the static contact of the drop-out fuse The structure and leads are improved as shown in the figure: ①The fixed static contact screw is designed as a polygonal shape, in which the height of the prismatic part is the same as the thickness of the static contact copper plate, and the upper part is equipped with a fastening nut and washer to make the upper static head fixed screw The problem of loose contact and poor contact of conductive parts has been effectively solved. ②As shown in Figure 3, in order to prevent or reduce the problem of frequent blowout of the upper lead, the drop-out fuse wiring adopts double leads, which are connected to the fixed contact fixing screw and the terminal of the drop-out fuse to avoid heat and burnout of the contact. lead. After the above improvements, implemented in the oil field 6-10kV power distribution network, the drop-out fuse lead blowout failure was significantly reduced, and the number of line trips caused by this was reduced by more than 25%, achieving good economic and social benefits.

Conclusion In recent years, oilfield 6-10kV power grids have repeatedly encountered poor contact of the static contact of the drop-out fuse and blown-out faults of the lead wires, which caused frequent line trip accidents, which seriously affected the safe operation of the oilfield power grid. In response to this problem, improvement measures are proposed. After the measures are implemented, the effect is very obvious, which greatly improves the reliability and economy of 6-10kV grid operation, and has good economic and social benefits.