Measures to improve short-circuit resistance of power transf

The safety, economy, reliable operation and output of transformers depend on the quality of their production and operation environment as well as the quality of maintenance. The power grid is often short-circuited by lightning strike, relay maintenance misoperation or failure to operate. The strong impact of short-circuit current may damage the transformer. The calculation results of transformer short-circuit impact show that 80% of them are caused by manufacture factors, while only 10% are caused by operation and maintenance factors. Planning, production methods in the second chapter has been discussed, this chapter focuses on the operation and maintenance process should be adopted in the approach to be clarified. In the process of operation and maintenance, on the one hand, short-circuit fault should be reduced as much as possible, and then the number of impact on the transformer should be reduced. 1. In addition to the reduction of transformer loss and the improvement of insulation level, the manufacturers should also consider the mechanical strength and the ability to resist short-circuit faults of the advanced transformer. In terms of fabrication skills, since many transformers use insulated pressure plates and high and low voltage coils share one pressure plate, this construction requires a very high level of fabrication skills and the pads should be densified, after the coil is processed, it is necessary to dry the single coil under constant pressure and measure the height of the coil after it is compressed. After each coil of the same pressure plate is processed with the above skills, it is adjusted to the same height again, the specified pressure is applied to the coil with an oil pressure device during final assembly to reach the height required for planning and skill. In the final assembly, in addition to paying attention to the high-voltage coil compression, but also pay special attention to the low-voltage coil compression control. Because of the effect of the radial force, the inner coil is usually kneaded in the direction of the core, so the support between the inner coil and the core column should be strengthened, the radial dynamic stability of the coil can be improved by adding the number of supports and adopting a thicker paper tube as the coil framework. 2. The reliability of large transformer operation depends primarily on the level of its construction and manufacture skill, and secondly, it carries out various experiments on the equipment during operation to grasp the working condition of the equipment in time. In order to know the mechanical stability of transformer, short-circuit test can be carried out and the weak points can be improved. 3. Using the reliable relay maintenance and active reclosing system, the short-circuit accident in the system is something that we try hard to prevent but can not definitely prevent, in particular, 10 KV LINES DUE TO MISOPERATION, small animals into, external forces and user duties and other factors such as short-circuit incidents may be extremely large. So on the operation of transformers, the first should be equipped with reliable maintenance system for the use of DC power, and to ensure the correctness of maintenance action. In view of the poor strength of the external short-circuit of the existing transformer in operation in Hangzhou, we should see the negative elements of the active overlap or forced operation of the system after the short-circuit trip, otherwise the damage of the transformer will be aggravated from time to time, or lose the chance to recalibrate. Now some operating departments, according to the probability of whether the short-circuit fault can be eliminated instantaneously and actively, use coincidence between overhead lines (such as within 2 km) or cable lines to cancel, it may be appropriate to extend the closing interval to reduce the damage caused by unsuccessful reclosure and to test short-circuit tripping transformers as much as possible. In operation should be short-circuit current impact of the transformer record, and accounting for short-circuit current multiples. 4. The deformation test of transformer windings is carried out actively to confirm the diagnosis. After the general transformer is impacted by short-circuit fault current, the windings will be partially deformed. Even if there is no immediate damage, there may be serious risk of defects. First of all, insulation interval will be changed, solid insulation, suffered damage, resulting in partial discharge. When encountering the lightning overvoltage effect, there may occur interturn and intercake breakdown, which may lead to sudden insulation accident, or even under the normal operating voltage, because of the long-term effect of partial discharge, may cause insulation breakdown accident. Second, the winding mechanical function decline, when again short-circuit incident, will not be able to accept the huge electric power effect and attack damage incident. Because the transformer winding deformation tester is expensive, and the nature of the personnel request is high, in the production operation is not easy to spread. Therefore, in practice, the method of judging whether the winding is deformed according to the change of winding capacitance can be used as a useful compensation of frequency response method. Especially when the frequency response method does not have the conditions, the measured capacitance can be collected by cross and Longitudinal comparison, and the working condition of the transformer windings can be grasped in time, so as to reduce the probability of the accident, to ensure the safe and stable operation of the power grid. 5. It is necessary to strictly carry out the construction according to the manufacturer's specification and standard request, and strictly control the quality when using the reliable short-circuit maintenance system to carry out the installation of the transformer on site, it is necessary to adopt corresponding measures to eliminate the dangers found. The operation and maintenance personnel should strengthen the check and maintenance of the transformer to ensure that the transformer is in excellent operating condition, and adopt corresponding measures to reduce the probability of outlet and short-circuit fault. In order to prevent the short circuit fault of the system as much as possible, for the transformers which have been put into operation, the first thing is to equip a reliable DC system for the operation of the maintenance system to ensure the correctness of the maintenance action; secondly, we should try our best to make an experiment on the transformer caused by short-circuit trip. We can use the frequency response method to measure the condition of the transformer after it is impacted by short-circuit trip, this can be useful to prevent the outbreak of major incidents. Whether a transformer can accept various kinds of short-circuit current mainly depends on the transformer construction planning and manufacturing skills, and has a great relationship with Operation Management, operation conditions and construction skill level, in order to prevent the accident from happening, we should adopt some useful control methods from many aspects to ensure the safe and stable operation of the transformer and the power grid system.