Determination of Dielectric Strength of Insulating Oil

Determination of Dielectric Strength of Insulating Oil

Overview

Insulating oil is an important liquid insulating medium, widely used in high-voltage electrical equipment such as transformers, oil circuit breakers, oil-filled cables and power capacitors. It functions for insulation, heat dissipation and arc extinction. During long-term operation, insulating oil is prone to deterioration under the effects of oxygen, high temperature, humidity and impurities, which degrades its insulation performance and directly endangers the safe operation of electrical equipment.

Experimental Purpose

Testing the dielectric strength (breakdown voltage) of insulating oil can accurately judge the insulation quality of oil samples and evaluate the operational safety status of equipment. The test is carried out in accordance with GB507-86 Determination of Dielectric Strength of Insulating Oil and IEC-156 standards, using the SH125A insulating oil breakdown voltage tester.

Experimental Samples and Instruments

- Test sample: Insulating oil to be tested

- Test instruments:

1. SH125A insulating oil breakdown voltage tester

2. Special insulating oil cup, suede cloth, cleaning reagents and other accessories

Operation Procedures

1. Clean the oil cup, adjust the electrode gap to 2.5 mm, place the magnetic stirrer inside, and fill with an adequate amount of test insulating oil.

2. Place the oil cup steadily into the high-pressure chamber of the instrument, cover the high-pressure hood and close the safety switch; connect the power supply and ensure reliable grounding.

3. Preset test times, stirring and standing time via the instrument panel, then enter standby mode after setting.

4. Press the Test key; the instrument automatically completes stirring, standing, pressure rising, breakdown detection and data recording.

5. After the test, the instrument automatically calculates and displays the average value and supports one-click printing of test reports.

Data Analysis and Result Evaluation

Nine dielectric strength tests were performed on insulating oil with the SH125A tester under the standard electrode gap of 2.5 mm. The minimum breakdown voltage was 35.4 KV, the maximum 43.5 KV, and the average 39.8 KV. All measured values exceed the national qualified standard of ≥35 KV.

The test data show small fluctuation and good repeatability, proving the instrument features high measurement accuracy and stable performance. The tested insulating oil meets the requirements of GB507-86 and IEC-156 specifications with qualified insulation performance, and can be safely applied to various high-voltage electrical equipment.