1. Preparation before the experiment

Environmental confirmation: Good weather, ambient temperature≥+5℃, air humidity ≤80%.

Ensure that the testing conditions meet the standards and reduce environmental errors.

Equipment status confirmation: Ensure that the tested equipment has been powered off, grounded and discharged, and switched to maintenance status.

Ensuring personal and equipment safety is a prerequisite for safety.

Preliminary insulation inspection: Measure and record the insulation resistance of the tested equipment.

Preliminary assessment of insulation condition to avoid damage to instruments caused by poor insulation.

Sample pretreatment: Clean the surface of the sample, remove dirt and moisture. For liquid (such as oil) samples, it is necessary to let them stand and control the temperature（±1℃) and standardized sampling.

Reduce surface leakage current interference and ensure measurement accuracy.

2. Wiring and Instrument Settings

Choose wiring method: Select according to the grounding condition of the test sample. Positive connection method: insulation of the test sample to ground; Reverse connection method: The test sample is grounded (at this time, the instrument bridge body is at a high potential and needs to be operated on an insulation table).

Adapt to different sample structures, special attention should be paid to safety when reversing.

Instrument grounding: The grounding terminal of the tester and the test object must be reliably connected to the grounding grid. For large capacitance samples, the grounding points of the instrument and the sample should be separated.

Prevent voltage counterattack and ensure the safety of personnel and instruments.

Select test parameters: Select the corresponding wiring method and test voltage level in the instrument menu. When there is significant interference, priority should be given to using the inter frequency measurement mode.

By operating the instrument in the correct mode, cross frequency measurements can effectively resist interference.

3. Testing and Data Recording

Start testing: After confirming that the wiring is correct and personnel have been evacuated, start the testing. The instrument automatically balances, boosts, and measures.

Obtain the dielectric loss factor（tanδ) And capacitance（Cx）The numerical value.

Exception handling: If timeout occurs during testing, try lowering the voltage and retesting; If the test sample is short circuited, the instrument should automatically protect it.

Dealing with special situations such as large capacitor test samples or equipment crashes.

Recording and retesting: Recordingtanδ value, capacitance, test voltage, environmental temperature and humidity. If necessary, reset the instrument and retest the same device.

Form a complete test report, and retesting can verify the reliability of the results.

4. Recovery after testing

Safe discharge and disconnection: After the test is completed, turn off the instrument power first and disconnect it noticeably220VAfter testing the power supply, fully discharge the test sample through the grounding rod, and finally remove the wiring.

Prevent residual charges from causing electric shock and ensure the safety of subsequent work.

On site cleaning: Clean up the site, collect the instruments and testing lines.

Keep the work site tidy.

Introduction to core measuring instruments

Traditional Xilin bridge：Classic AC bridge, regulated byR3TheC4Realize balanced calculationtanδ. The principle is intuitive and often serves as a benchmark. But the operation is cumbersome, the balance needs to be manually adjusted, and the anti-interference ability is weak.

Digital automatic tester：Automatic measurement using techniques such as vector operation and digital waveform analysis. High degree of automation, easy operation, and anti-interference (such as frequency measurement) Functionality is the mainstream choice for on-site testing.

Key precautions and safety requirements

Safety first, strictly prevent electric shock: all operations must be carried out after confirming the power outage. When using the reverse connection method or the built-in boosting device of the instrument, a safe distance must be ensured, and the high-voltage lead must be kept away from the human body and low-voltage lines. It is strictly prohibited to touch any live parts during testing.

Ensure reliable grounding: The grounding of instruments and test samples must be firm and reliable. Poor grounding may result in inaccurate instrument protection, measurement, or the generation of hazardous potentials.

Pay attention to test samples and interference:

Test condition: Ensure good insulation at the low voltage end of the test sample, which is crucial for the measurement accuracy of small capacity and low loss test samples.

Anti interference measures: On site interference (such as electric and magnetic fields) can seriously affect the results. If using power frequency（50Hz）The measurement data is unstable and must be switched to different frequency measurement mode. In addition, keeping the test line short and firm, keeping hands and body away from the test sample, can also reduce errors.

Standardize instrument operation:

Preheating: Before precision measurement, the instrument should be preheated by about30Minutes to reach a steady state.

Exception handling: Do not suddenly cut off the power during testing to avoid overvoltage. Long term no results may be due to excessive capacitance or system failure of the test sample. The device should be shut down and the voltage should be reduced before attempting again.