10kV transformer is the most common power transformer in the distribution network. It is mainly used as an intermediate device for converting AC voltage (U) and current (I). When the AC current in the primary winding is out of date, it will produce convertible magnetic flux. The magnetic flux induces AC electromotive force in the secondary winding under the magnetic conduction of the iron core. The magnitude of the induced electromotive force is directly related to the winding turns ratio, The higher the voltage, the more the turns ratio, which is also the basic principle and work flow of power transformer transforming current and voltage. There is not only one 10kV power transformer, including s series, SC series and SCB series, with a capacity from 30KVA to 3150kva or even higher. It can be divided into oil immersed power transformer and dry-type transformer according to the insulation property. Of course, it can also be divided into ordinary transformer and special transformer according to the purpose, For example, special transformers are used in coal mines. Shiji power is a manufacturer specializing in the production of power test equipment. What are the preventive test items of 10kV power transformers? By
2.1 insulation resistance measurement
Generally, the insulation resistance standard is not specified. The insulation resistance measured by historical data is converted to the same temperature for comparison. Generally, it shall not be lower than 70% of the previous value, and the absorption ratio (R60 / R15) shall not be less than 1.3.
2.2 AC withstand voltage test
AC withstand voltage test is to check whether the insulation between phases and turns of the main insulation is good under the action of AC. the test voltage after operation is different from that of the newly installed power transformer. The ex factory withstand voltage of 10kV power transformer is 35kV, 30KV after handover and overhaul, and 28kv during operation. The above is the reference test voltage of power transformer in different periods, In practical application, the test voltage can be reduced according to the transformer, and the leakage current is generally not specified, but there shall be no significant change compared with the values over the years.
2.3 measurement of winding DC resistance
For transformers above 630kVA, the difference between the DC resistance of each phase winding converted to the same temperature (the difference between lines without neutral point outgoing line) shall not be greater than 2% of the average value of three phases; Compared with the previous measurement results, the relative change shall not be greater than 2%.
The phase to phase difference below 630kVA shall not be greater than 2% of the three-phase average value, and the line to line difference shall not be greater than 4% of the three-phase average value.
2.4 electrical strength test of insulating oil
Take the transformer oil sample in operation with a special container for oil withstand voltage test, and the average test voltage shall not be less than 20kV.
2.5 measuring insulation resistance
2500V insulation resistance tester shall be selected to measure the insulation resistance of iron core to ground, iron core to yoke beam and core bolt to iron core, and measure the absorption ratio and polarization index if necessary.
2.6 check winding voltage ratio and polarity
It is recommended to use sjbc-y full-automatic ratio group tester for winding ratio polarity, with large screen display, automatic calculation of relative error and automatic range switching. It is specially designed for star delta power transformer, with intact protection measures, true and reliable measurement data, and the three-phase ratio error is no more than 0.5%.
Shiji power is a manufacturer of preventive test equipment for 10kV, 35kV, 110KV, 220kV and 330kV power transformers. It has more than 110 on-site cases every year. It has excellent quality, accurate service and reasonable price. Welcome to consult!
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