The key operating points list for the measurement standards of relative permittivity, dielectric loss factor, and DC resistivity of liquid insulation materials in GB/T 5654-2007 is as follows:

Core testing steps

Sample preparation: Clean the electrode and oil cup with anhydrous ethanol or petroleum ether to remove oil stains and impurities, and ensure surface cleanliness after drying. Let the oil sample stand in the laboratory environment until its temperature approaches the ambient temperature.

Electrode installation: Assemble the dried and cooled electrode cup (without adding oil), measure the capacitance and dielectric loss values of the empty cup as background values.

Test execution: Apply a specific frequency (usuallyMeasure the current and applied voltage in the oil sample using an AC voltage of 50 Hz and amplitude, and calculate the dielectric loss factor (tan δ) of the oil.

Key precautions

Temperature control: The testing temperature must be strictly controlled within23 ± 2 ℃, humidity controlled at 50 ± 5% RH.

Electrode cleaning: The cleaning of the electrode cup is the most critical step, and all components must be cleaned with appropriate solvents, then rinsed with anhydrous ethanol, and finally fully dried in an oven.

Environmental control: Avoid testing in flammable gases, high temperatures, humidity, or corrosive environments.

Equipment calibration: Regularly followJJG series metrological verification regulations calibration equipment.

Safety Specifications

Operators are required to wear insulated gloves.

Ensure good grounding before testing.

After testing, the high-voltage output terminal needs to be discharged.

The equipment should be equipped with overcurrent protection device (in case of breakdown)Cut off the power within 0.05 seconds.

The electrode cup cleaning steps in GB/T 5654-2007 standard are as follows:

Disassembly and preliminary cleaning: Disassemble the various components of the electrode cup and clean all parts with organic solvents such as petroleum ether or n-hexane to remove oil stains and impurities.

Deep cleaning: Rinse several times with anhydrous ethanol to remove residual petroleum ether and other water-soluble impurities.

Boiling treatment: Place the cleaned parts inBoil a 5% solution of trisodium phosphate in distilled water for 5 minutes, then rinse several times with distilled water.

Final processing: Boil the components in distilled water at leastAfter 1 hour, take it out and dry it in an oven at 105-110 ℃ for no less than 1 hour.

Assembly and inspection: Assemble when all components have cooled down to not be hot to the touch, and clean with the oil sample to be tested before use2-3 times.

After cleaning, it is necessary to check whether the electrode cup is dry and clean, and measure the capacitance of the empty cup (the standard value should be40 ± 1pF) to ensure no residual impact on the test results.