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  • What is the purpose of DC resistance testing for transformers?

    The DC resistance of the transformer refers to the DC resistance value of each phase winding. The purpose of measuring the DC resistance is to check whether there is an inter-turn short circuit inside the three-phase winding;
    Because if there is a short-circuit between phases in the transformer, the short-circuit current value is very large, it is easy to burn the transformer, the phenomenon of the fault is also obvious, and the appearance is easy to judge; however, if a short-circuit occurs between the winding turns of one of the phases, the short-circuit current If the value is very small, the automatic transformer protection will trip. However, it is difficult to see whether the transformer itself is faulty from the appearance of the transformer. By measuring the DC resistance of each phase and comparing the resistance values of the three phases, it is easy to determine whether an inter-turn short-circuit occurs inside: the resistance value is large, and the possibility of inter-turn short-circuit failure is great; if it is basically similar, this can be ruled out. The possibility of a failure.

    In summary, the purpose of measuring the DC resistance is to determine whether the transformer has an inter-turn short circuit or whether the line falls off, so as to facilitate troubleshooting.

    Panel display of GDZC-Series DC resistance tester
    GDZC-series transformer winding resistance tester Intelligent loop DC resistance power analyzer

  • What service can our company provide you?

    Pre-sale Service:
    1. The professional sales team will reply to the inquiry in real time;
    2. Customize suitable solutions according to the needs of different customers;
    3. Provide product technical parameters/operation manuals and evaluation reports, etc.;
    4. During the global 
    COVID-19, video factory inspections are supported.
    After-sale Service:
    1.From the date of purchase within one year instrument, is a product quality problem free repair replacement, lifetime supply of maintenance and technical services.
    2.Technical Support
    (1)Our technical team supports our customers at all time with our long experience, expert advice and the unlimited spirit and always be for providing the best customer service.
    (3)Training how to install the machine,you can arrange your engineer to our company to get free training.
    (4)If necessary, we can also arrange our engineer to your company for training and commissioning at your cost.
    3.The instrument has found anomalies or malfunctions please contact us to arrange the most convenient treatment options.

  • Why do transformers need tan delta and power factor tester?

    Its function is to check the overall moisture/aging of the transformer, and to find dust and serious local defects on the windings. The measurement results of the dielectric loss factor are often affected by surface leakage and external conditions. Measures should be taken to reduce and eliminate this effect (for example, using the inter-frequency method/frequency conversion method to resist interference).
    The measured dielectric loss factor value refers to the reference standard of the measurement together with the casing. However, in order to improve the accuracy of the measurement and further detect the sensitivity of the defect, if necessary, a decomposition test can be carried out to determine the location of the defect.
  • Why do we need to filter transformer oil?

    Transformer Oil Purifier

    Transformer oil is the main insulation and cooling medium of oil-immersed transformers, and its electrical strength and chemical composition directly affect the performance of the transformer. The insulation strength will decrease If the oil contains a small amount of moisture and impurities; and if the oil is in contact with oxygen, it is easy to oxidize and deteriorate at high temperatures. Therefore, the transformer oil should be filtered when the transformer is installed.
    To prevent the safety operation from being affected by the deterioration of the oil quality, the regular oil samples of the power distribution system in normal operation should be tested and analyzed, and the oil should be processed according to the results of the analysis. The inspection period for the oil chemical supervision of power distribution operation is stipulated to be at least once every 3 years.
    The main parameters to measure the quality of transformer oil are: acid value, water-soluble acid, breakdown voltage, flash point, density, viscosity, pour point, interfacial tension, etc.

    Our ZJA Series Transformer Oil Purifier is suitable for purifying all kinds of transformer oils.
    Get more information:
  • Influencing Factors of Transformer Insulating Oil Breakdown Voltage Test

    1. Although the breakdown of the oil gap during the experiment is a short moment, the process is complicated. Even if it is a cup of sample, the measured value in multiple breakdown tests is very dispersive. Each test standard stipulates that the average value of 6 tests is taken as the test result. This kind of stipulation is rare in general tests.
    2. Insulating oil dielectric strength testing equipment includes booster device, oil cup and electrode, stirring device, data output device (digital printer), timing device, etc. Abnormalities in each part will cause errors in the measurement results, so choose fully automatic The performance of the testing instrument is stable, and there are few pollution links, and the influence of human factors is basically eliminated in the measurement process.
    3. The influence of environment in the breakdown voltage test of transformer insulating oil
    Whether the transformer is sampled during operation or during installation, the insulating oil in it will be in contact with the air. During the contact process, dust and moisture will inevitably be mixed into the transformer insulating oil sample to be tested. As a result, the measured value of the breakdown voltage of the transformer insulating oil is low. Therefore, the standard for the breakdown voltage test of the transformer insulating oil should include an oil cup/dust cover and complete the test as soon as possible.
    In summary, it is necessary to formulate strict regulations and unified measurement methods for some obvious influencing factors during the experiment. It is very necessary to maintain the influence of these factors on the results at a constant level.
  • Why do we use ultra-low frequency test instead of power frequency withstand voltage test?

    The ultra-low frequency insulation withstand voltage test is actually an alternative method of the power frequency withstand voltage test. We know that when power frequency withstand voltage tests are performed on large generators, cables and other test products, due to their insulation layer presents a large capacitance, we need a large-capacity test transformer or resonant transformer to complete the testing. Such huge equipment is not only cumbersome and expensive, but also very inconvenient to use. In order to solve this contradiction, the electric power department adopted to reduce the test frequency, thereby reducing the capacity of the test power supply.
    Through many years of theory and practice at home and abroad, it has been proved that using 0.1Hz ultra-low frequency withstand voltage test instead of power frequency withstand voltage test can not only have the same equivalence, but also greatly reduce the volume and weight of the equipment, and the theoretical capacity is about one-fifth of the power frequency. The test procedure is greatly reduced, and it has more advantages compared with the power frequency test.
  • What are the factors that affect the insulation strength of SF6 gas?

    There are the following factors influencing the insulation strength of SF6 gas.
    1. The effect of uniform electric field performance. Under a uniform electric field, the insulation strength increases linearly with the distance between the contacts. If the distance is too large, duo to the uneven state of the electric filed, the insulation strength increases and saturation occurs. Under an uneven electric field, its insulation strength will even approach the air level.
    2. The relationship with stress. The insulation strength increases with the increase of gas pressure. Under the more uniform electric field, the insulation strength is affected by the thickness of vessel wall and the volume of components inside the equipment.Don't raise the gas pressure too high.Generally at 20℃, the pressure of SF6 gas chamber is 0.3~ 0.6mpa, and that of SF6 arcing chamber is 0.5~ 0.7mpa.
    3. Influence of electrode surface state. Generally, the rougher the electrode surface, the lower the breakdown voltage.The greater the electrode area is, the greater the probability of the occurrence of accidental factors will be, thus reducing the breakdown voltage
    Influence of voltage polarity. As the insulation structure of SF6 circuit breaker is in the form of slightly uneven electric field, the insulation level is often determined by the complex polarity voltage.
  • Why we need GDRZ-902 Transformer SFRA

    After the transformer is designed and manufactured, its coil and internal structure are determined. Therefore, for a multi-winding transformer coil, if the voltage level is the same and the winding method is the same, the corresponding parameters (Ci, Li) of each coil should be Is ok. Therefore, the frequency domain characteristic response of each coil is also determined accordingly, and the frequency spectrum of the corresponding three-phase coils is comparable.


    Transformer is an indispensable important instrument in power system. During transformer repair or transportation, transformer winding may be deformed. At the same time, inter-turn and inter-phase short circuit may also occur during the test of transformer. The transformer winding deformation tester is mainly used to measure various parameters of the transformer internal winding. After obtaining various accurate measurement data, the computer system compares and analyzes it to make judgments on the internal fault state of the transformer.

  • What kind of certificate can you provide?

    We can provide CE mark,ISO 9001 quality certificate, the third party calibration certificate(CNAS),factory test report.
  • What's the delivery lead time?

    For most of the products, delivery lead time is 10 days after the order is confirmed; For some customized products, please check with the sales person.
  • What's the payment term?

    For total amount below USD3,000.0, payment term is 100% T/T as deposit; For total amount above USD3,000.0, payment term is 30% T/T as deposit, the balance before delivery; The payment term is also negotiable.
  • What's the warranty period?

    Warranty period is 1 year



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