In the complex electromagnetic environment of UHV substations, it can accurately extract weak signals with an error controlled within ±0.0001. Multi-spectrum diagnosis: In addition to measuring power frequency tanδ, it can also perform frequency domain dielectric spectroscopy (FDS) scanning. By analyzing the dielectric loss curves at different frequencies, it can more deeply determine the aging degree and moisture content of insulating paper (which is not possible with traditional single-frequency testing). Wireless synchronization and cluster testing: Supports wireless synchronization of multiple instruments, simultaneously performing three-phase testing on the high, medium, and low voltage sides of large transformers, greatly reducing power outage time. AI-assisted diagnosis: Built-in big data model automatically compares historical data and data from similar equipment, directly providing conclusions of "normal", "caution", or "abnormal" and possible fault types (such as "suspected moisture" or "suspected partial discharge"). Miniaturization and lithium battery power: The whole machine weight is generally reduced to below 5kg, with built-in large-capacity lithium batteries, 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 with 35kV and above, winding tanδ < 0.5% - 0.8%). Equipment in operation: If the tanδ value increases sharply with temperature, it usually indicates moisture in the insulation. If the tanδ value significantly increases (exceeding 30% of the initial value or the absolute value exceeds the standard), 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 mean internal short circuit in the insulation (capacitance increases) or disconnection/moisture evaporation (capacitance decreases). 6. Operation precautions Safety first: Testing involves high voltage (usually 2kV-10kV, or even higher). High-voltage test safety regulations must be strictly implemented, with fencing and dedicated supervision. Full discharge: Before and after testing, the test object must be fully discharged, especially for capacitive equipment, as residual charge can be as high as several thousand volts. Surface cleaning: Dirt and moisture on the surface of the test object can cause surface leakage current, leading to inflated tanδ measurement values. Clean the surface or use a shielding ring before testing. Temperature recording: tanδ is greatly affected by temperature. The temperature of the test object must be accurately recorded and converted to 20°C according to regulations for comparison. 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-type breakdown or severe moisture Not sensitive to slight moisture or 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, need to pay attention to interference and temperature effects
