The insulation resistance of a transformer is an important indicator to measure its insulation performance, reflecting the insulation condition of the transformer windings and their related insulation materials. Insulation resistance refers to the resistance value between windings, windings to ground, or windings to the core under a certain voltage, which is used to judge the integrity of the insulation layer and the safety of electrical equipment.
The insulation resistance of a transformer mainly includes the following aspects:
1. Insulation resistance of windings to ground: used to measure the insulation between the windings and the transformer casing or ground. Its insulation performance determines the leakage risk between the windings and the ground.
2. Insulation resistance between windings: When the transformer has multiple windings, measure the insulation resistance between windings (such as between high-voltage windings and low-voltage windings) to evaluate the insulation condition between each winding to ensure that there is no mutual interference or short circuit.
3. Insulation resistance of windings to the core: used to measure the insulation performance between the windings and the core to ensure that there is no leakage or short circuit between the windings and the core.
4. Insulation resistance inside the winding: This refers to the insulation performance between turns and layers of the winding. Although this part of the insulation is usually not directly measured, it is critical to the overall insulation performance of the transformer. Damage to the inter-turn insulation may cause a short circuit inside the winding.
It is pointed out that the damage of the distribution transformer is mostly caused by electrical breakdown and electrochemical breakdown, and the defects of the dielectric medium are the main causes of electrical breakdown and electrochemical breakdown. In order to avoid the damage of the insulating medium, the transformer overload should be limited and the short circuit should be prevented. In the work, the transformer field test should be done to strengthen the insulation supervision of the transformer oil; to prevent overvoltage and overcurrent, it should be installed properly. Overcurrent, overvoltage protection, periodic measurement of transformer insulation and oil temperature. In terms of operation management, it is necessary to strengthen inspection and inspection, and focus on the operation sound, oil level and temperature of the transformer, so as to detect the partial discharge defects between the layers and deal with them in time to avoid transformer damage.
According to statistics, various faults of high-voltage power grids are mostly caused by damage of high-voltage electrical equipment insulation. Therefore, understanding the insulation characteristics of equipment, mastering the insulation status, and continuously improving the insulation level of electrical equipment are the fundamental guarantee for the safe and economic operation of power systems.
As the main equipment of the power system, it is very important and necessary to maintain good insulation during operation. In order to ensure the insulation level of the transformer, a series of insulation tests are to be carried out from the manufacture of the transformer. These tests include: insulation testing of raw materials at the time of manufacture, intermediate testing of the manufacturing process, qualitative and factory testing of the product, handover test after installation on site, and insulation preventive test for maintenance operation during use. Among them, the handover test and preventive test of the transformer are the two most important tests, and the handover test not only has a judgment on the overall insulation of the transformer. It also provides basic information for preventive testing during future operations. Therefore, the infrastructure personnel must pay special attention to the accuracy and authenticity of the handover test in the infrastructure construction process. At the same time, it is necessary to understand the insulation test content and principle of the transformer in the handover test.
Kingrun series transformer JYM insulation resistance tester provides a reliable guarantee for the testing of transformer insulation resistance
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