どのように、トランス油試験が行なわれるのですか？

How is the testing of transformer oil conducted? The dielectric strength test of transformer oil is conducted using a 500mm³ standard oil cup in a 60kV AC frequency oil tester. The brass electrodes of the oil cup have a diameter of 25mm, and the surface cleanliness is as shown in Figure 92—6, with an electrode spacing of 2.5mm. Firstly, the oil cup is rinsed with the test oil for at least three times. Subsequently, the test oil is poured into the cup until it reaches 10mm below the cup’s rim, and then left undisturbed for 10 minutes to eliminate bubbles. The voltage is gradually increased until breakdown occurs, and the

How is the measurement of insulation resistance and absorption ratio conducted? Insulation resistance, denoted as R, is typically determined by applying a voltage of 2500V for 60 seconds and measuring the resulting value using a megohmmeter with a maximum range of 10000 MQ. Due to variations in the stability of insulation resistance arising from differences in product geometry, structure, material, and moisture content within the insulation, there is no standardized value for R. To provide a rough constraint on R and depict its relationship with temperature, the absorption ratio (Ro/Rs) is the ratio of insulation resistance measured during direct current application for 60 seconds and 15 seconds (for large transformers,

How is the measurement of winding resistance conducted? When measuring winding resistance, both the bridge method and voltage drop method are employed. For resistance values exceeding 100, a single-arm bridge is utilized, while for values below 102, a double-arm bridge is employed. In the voltage drop method, a power source consisting of a 2-12V battery is used, and the connections of the voltmeter and ammeter are directly attached to the terminals of the winding under test. During the measurement process, it is essential to wait for the current to stabilize before connecting the voltmeter and, prior to cutting off the power supply, disconnect the voltmeter to obtain the measured resistance

What are the common electrical tests for transformers? Conventional electrical tests for transformers are designed to identify internal faults and primarily include the following: (1) Voltage Ratio Test: Used to verify the voltage ratio and determine if there are short circuits between turns or layers, or if switch leads are connected incorrectly. (2) Winding Resistance Measurement: Employed to assess the quality of wire welding, detect winding short circuits, poor switch contacts, or incorrect lead connections. (3) Insulation Resistance and Absorption Ratio (Ro/R₁s) or Polarization Index Measurement: Utilizing a 2500V megohmmeter to measure the insulation resistance R at 60 seconds and comparing it with the insulation resistance Rs at 15 seconds,

How to conduct a pump test for oil-immersed transformers? Performing a pump test for oil-immersed transformers is an essential step in the production and maintenance processes. For transformers that have completed the assembly, especially those with a capacity of 8000kVA, voltage of 35kV and below, and equipped with an oil storage tank, a pump test must be carried out, as shown in Figure 87-1(a). For transformers with a capacity of 3150kVA, voltage of 60kV and above, the same method can be employed even after oil filling to ensure the quality during transportation and storage. During the pump test, the pump joint should be installed at the plug seat on top

How to perform oil leak repair? To achieve oil welding repair, the following measures can be taken: (1) Selection of Welding Method for Oil Leak Repair： Considering the characteristic of rapid heat dissipation in oil leak repair, arc welding should be used for repairs instead of gas welding. (2) Pre-treatment and Welding Measures for Different Oil Leak Conditions： To prevent the oil flow from extinguishing the arc and hindering the fusion of molten droplets, materials such as asbestos rope can be used to pre-seal the leak, and then welding can be carried out. This can eliminate or reduce the oil flow. For leaks that cannot be pre-sealed, such as cracks,

Can transformers be welded with oil for repair? The repair of oil leakage in transformer welding lines is a crucial task for operating personnel. If welding repairs are conducted during a power outage with oil drainage, the transformer body remains inside the oil tank. As the insulation on the transformer body is already impregnated with oil, there will still be residual oil and gas in the tank. During arc welding repairs, the oil and gas are prone to combustion due to the heat generated by the electric arc. If the decision is made to completely dismantle the transformer for oil drainage and welding repairs, it entails a significant amount of

Why is it necessary to fill nitrogen and dismantle components such as casings during transportation?   And why is it required to remove the oil storage tank and safety duct during vacuum oil injection? When the transport weight of a large transformer exceeds the carrying capacity of the transport vehicle, it is necessary to release the oil for transportation. However, once the oil is released, the core and winding inside the oil tank come into contact with the air. Although the air contains 75% nitrogen, the nitrogen in the air contains moisture. Contact with the surface of the core can lead to rusting, and contact with the winding can cause moisture

What are the characteristics of the three commonly used winding configurations in transformers? (1) Y-shaped winding characteristics: The Y-shaped winding has a winding current equal to the line current, with a larger wire cross-section, providing excellent mechanical strength. The winding voltage is equal to 1/√3 times the line voltage, resulting in fewer turns and insulation requirements. The filling factor of the conductor is large, enabling graded insulation. Due to the high filling factor, the inter-turn capacitance is higher, resulting in a uniform distribution of impulse voltage. Additionally, the neutral point can be grounded and used to achieve a four-wire system. The main drawback of this configuration is the absence of

What should be noted during the welding of leads for transformers with a voltage of 60kV and above? When welding leads for transformers with a voltage of 60kV and above, the following precautions should be taken: Before welding the leads, it is essential to wrap the base of the leads to be welded with wet asbestos rope and cover the winding with tarpaulin. The welding flux should be prepared as needed, but the usage time should not exceed 8 hours. After welding, it is necessary to remove welding flux, oxide residue, insulation scorching, and any burrs. The welding area should be covered with shielding material to prevent local discharge. If