Fault analysis and of the hottest 110kV and above

2022-08-09
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Fault analysis and treatment of 110kV and above voltage transformer

due to the problems of manufacturing quality and poor sealing of the oil conservator, its poor insulation may cause an explosion, which is manifested in the fact that the upper cover plate of some oil conservators is thin, the welding is poor, the flange box edge is thin, the pitch is large, and the processing technology is not fine, resulting in rough and unequal joint surfaces. In addition to improving the pulverizing level and capacity of metal powder, if the quality of the sealant pad used is not good, it will deteriorate and lose elasticity after long-term use, and even crack, causing water leakage and moisture, but in the metallurgical industry

the installation of the moisture absorber is unreasonable. If it is out of repair for a long time, and the silica gel fails, when the temperature suddenly changes and the humidity increases, the moisture will enter the transformer, resulting in the decline of insulation and the moisture entering the transformer body. 1 Temperature control of extruder host: water forming breakdown

there are problems in the body design, material selection and processing technology, such as 110kV and above voltage transformers, which mostly use enameled wire. Some winding processes are not strict, the coil is deformed, the wire turns are crossed and overlapped, the tightness is different during winding, or the insulation thickness between layers is uneven, which may cause inter layer or inter turn short circuit and cause transformer explosion; The quality of selected materials is not good, such as 220kV capacitive structure current transformer. If the insulation performance of the selected cable is poor, it is easy to cause faults. For example, the water absorption of the material used to support the insulation board of the voltage transformer is large, and without oil immersion treatment, the insulation performance is poor, which is also easy to cause breakdown and cause faults

the support plate of the voltage transformer body is poor in quality, cracks during operation, partial discharge occurs, and then expands to breakdown in pairs

the core structure of cascade voltage transformer is defective, and the clamping screw has suspended potential or the screw has sharp angle, which causes partial discharge; For the voltage transformer with double cores, if the distance between the two cores is not enough, it may also cause creepage flashover and cause faults during operation

oil leakage from the outgoing terminal of the transformer or poor insulation of the outgoing terminal board may also cause faults

in addition to the lax control of manufacturing, material selection, design and factory test, the transformer fault is also directly related to the untimely operation and maintenance, the untimely handling of problems found, and the disrepair for a long time

when TPV is used in automobile sealing system

II. Insulation test method for detecting transformer fault

1. Partial discharge and overheating faults of transformer can be judged by oil chromatographic analysis

2. when the transformer is poorly sealed and damped, if the measured value of insulation resistance decreases, it means that the whole or part of the winding is damped or degraded. For capacitive current transformers, if the insulation resistance of the end screen to the ground is less than 1000m Ω, the Tg of the end screen to the ground shall be measured δ, When the value exceeds 3, there may be water at the bottom of the transformer, and attention should be paid to the comparison and comprehensive analysis with the data of the transformer over the years

3. Compare the main insulation capacitance of capacitive current transformer with the initial value. If the difference is more than ± 5%, find out the reason. When the water is damp, because the dielectric constant of the water is greater than that of the insulation material of the transformer, the measured capacitance is greater than that when the water is not damp; When the capacitor element is broken down due to partial discharge, the capacitance will increase due to the reduction of the element, so measuring the capacitance of the end screen is an important method to monitor the insulation of capacitive current transformer

4. use TG δ Diagnose the insulation state of the transformer

(1)tg δ The analysis should pay attention to the monitoring standard and pay attention to its growth rate. For example, the Tg of a capacitive current transformer is measured δ Is 1.4% (the standard of the code is 1.5%), the Tg of the transformer was measured two years ago δ It is 0.41%, and its growth value is 3.4 times, but if it is considered that the measured value does not exceed the standard, it will not be paid attention to, and the result will inevitably lead to the fault of mutual inductance 2S, and the author even believes that the mutual inductance TG δ The growth rate of is more important and critical than its absolute value. In addition, for this kind of transformer, the dielectric loss and insulation resistance of the main screen and the end screen can be compared to judge the degree of moisture. For example, Tg of the main screen of a current transformer δ= 0.3%, insulation resistance r=5000m Ω, Tg of end screen to secondary and ground δ= 4.1%, insulation resistance r=150m Ω, indicating that the outer insulation is damp, but the moisture does not enter the main insulation, and there is water at the bottom of the box after lifting the core

(2)tg δ Relationship with temperature. For oil paper insulated transformer. tg δ The relationship with temperature depends on the comprehensive performance of oil paper. A good insulating oil is a non-polar substance, and the Tg of oil δ It is mainly conductive loss, which increases exponentially with the increase of temperature. Paper is a polar medium, and its TG δ The loss decreases with the relaxation of the dipole, so the Tg of the paper δ The Tg of oil paper insulation decreases with the increase of temperature in the range of -40 ~ 60 ℃ δ There should be no change, and temperature conversion is not necessary. When the temperature rises to 60 ~ 70 ℃ and above, the growth of conductivity loss is dominant, TG δ It will increase with the increase of temperature. At this time, it is necessary to carry out temperature conversion, rather than simply using the conversion method of oil filled equipment

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