With the development of smart grids and UHV technology, the dielectric loss tester is also continuously evolving: Ultra-strong anti-interference capability: In the complex electromagnetic environment of UHV substations, it can accurately extract weak signals, with error controlled within ±0.0001. Multi-spectrum diagnosis: It not only measures power frequency tanδ, but also performs frequency domain spectroscopy (FDS) scanning. By analyzing the dielectric loss curves at different frequencies, it can more deeply assess the aging degree and moisture content of insulating paper (which traditional single-frequency testing cannot achieve). Wireless synchronization and cluster testing: Supports wireless synchronization of multiple instruments, enabling simultaneous three-phase testing on the high, medium, and low voltage sides of large transformers, significantly reducing outage time. AI-assisted diagnosis: Built-in big data models automatically compare historical data and data from similar equipment, directly providing conclusions of "normal", "caution", or "abnormal" along with possible fault types (such as "suspected moisture" or "suspected partial discharge"). Miniaturization and lithium battery power: The overall weight of the instrument is generally reduced to below 5kg, with a built-in large-capacity lithium battery supporting all-weather field operations. 5. Test result criteria (reference standards) Note: Specific limits should refer to the latest national standards (GB) or industry standards (DL/T). The following are general empirical values: Newly commissioned equipment: tanδ is usually required to be very low (e.g., for transformers of 35kV and above, winding tanδ < 0.5% - 0.8%). Equipment in operation: If the tanδ value increases sharply with temperature, it usually indicates insulation moisture. If the tanδ value increases significantly (exceeding 30% of the initial value or exceeding the absolute value limit), it indicates insulation aging or deterioration. Capacitance change: If the measured capacitance changes by more than ±5% compared to the factory value or historical data, it may indicate internal short circuit (capacitance increases) or open circuit/moisture evaporation (capacitance decreases). 6. Operating precautions Safety first: Testing involves high voltage (usually 2kV-10kV, or even higher), and strict adherence to high-voltage test safety regulations is required, including setting up barriers and having dedicated personnel for supervision. Full discharge: Before and after testing, the test object must be fully discharged, especially for capacitive equipment, where residual charge can be as high as several thousand volts. Surface cleanliness: Dirt and moisture on the surface of the test object can form surface leakage current, leading to inflated tanδ measurements. Clean the surface or use a shielding ring before testing. Temperature recording: tanδ is greatly affected by temperature, so the temperature of the test object must be accurately recorded and converted to 20°C for comparison according to regulations. Correct wiring: The positive connection method and the reverse connection method must not be confused; otherwise, the instrument may be damaged or incorrect data may be obtained. 7. Differences from other instruments Table Instrument Name Measurement Object Main Function Limitations Megohmmeter Insulation resistance (R) Quickly determine whether insulation has through breakdown or severe moisture Insensitive to slight moisture and aging, greatly affected by surface leakage DC resistance tester DC resistance (R_dc) Detect conductive loop connections and inter-turn short circuits Cannot reflect the AC loss characteristics of insulating materials Dielectric loss tester tanδ & C Sensitively detect overall moisture, aging, and deterioration of insulation Relatively complex operation, requiring attention to interference and temperature effects