As the core equipment of the power system, the operational reliability of transformers directly impacts the safety and stability of the power grid. During routine maintenance, handover acceptance, and preventive testing, various professional testing instruments are utilized to conduct comprehensive inspections on key indicators such as insulation, windings, tap changers, oil quality, and voltage ratio. Different instruments have their respective functional focuses, collectively forming a comprehensive system for assessing the condition of transformers.

The DC resistance tester is primarily used to measure the DC resistance of transformer windings and serves as a crucial instrument for assessing internal defects within the windings. Through testing, issues such as inter-turn short circuits in the windings, poor soldering of leads, loose connectors, poor contact of tap changers, and abnormal gear positions can be quickly identified. By analyzing the three-phase resistance imbalance, hidden dangers in the conductive circuit can be accurately identified, preventing equipment overheating, increased wear, and even burnout failures during operation.

The transformation ratio and group tester is used to detect transformer transformation ratio errors, wiring group, polarity, and three-phase balance. It can determine whether the winding turns are correct, whether the tap changer position is accurate, and whether the high and low voltage wiring is correct. It effectively avoids problems such as voltage deviation, excessive excitation current, and increased no-load loss caused by abnormal transformation ratio. It is a necessary test item for newly commissioned and post-maintenance transformers.

The integrated transformer ratio and DC resistance tester integrates dual functions of transformer ratio testing and DC resistance testing, enabling the completion of two key tests with a single device. It reduces the number of on-site wiring and instrument switching, enhancing testing efficiency. It is suitable for rapid detection, on-site inspection, and emergency repair acceptance of distribution transformers, and is currently a widely used comprehensive testing instrument in operation and maintenance sites.

The insulation resistance tester (megohmmeter) is used to detect the insulation performance of transformer windings against ground and between windings. By measuring the absorption ratio and polarization index, it can determine whether the insulation is affected by moisture, dirt, aging, cracking, or has local defects. As a basic instrument for insulation testing, it can quickly screen for serious insulation hazards and ensure that the insulation strength of equipment meets operational requirements.

The power frequency voltage withstand test device (test transformer) is a destructive testing equipment that applies a specified high voltage to the transformer to test its insulation withstand strength. It can effectively identify issues such as weak insulation points, mechanical damage, and local defects. It serves as a crucial basis for determining whether the transformer can be safely put into operation and is widely used in handover tests and preventive tests.

The contact resistance tester (loop resistance tester) primarily measures the contact resistance of transformer bushing conductive rods, lead connectors, busbar lapping points, and disconnector contacts. Utilizing the high-current micro-ohm measurement principle, it accurately determines whether connectors are oxidized, loose, or poorly contacted, thereby preventing heat generation and burnout due to excessive contact resistance during operation.

The transformer oil chromatographic analyzer analyzes dissolved gases in insulating oil, and determines the presence of latent faults such as overheating, discharge, inter-turn short circuit, core overheating, and insulation aging within the transformer based on the content and ratio of gases such as methane, ethylene, acetylene, hydrogen, and carbon monoxide, thus achieving early fault warning.

In summary, various testing instruments play their respective roles and complement each other in transformer testing, comprehensively assessing equipment status from multiple dimensions such as insulation, conductive circuit, transformation ratio, oil quality, and internal faults. Proficiently mastering the functions and applications of various instruments is an important foundation for improving the quality of transformer maintenance and ensuring the safe and stable operation of the power grid.