How to Choose Insulating Oil Testers? A Complete Guide to Dielectric Strength vs. Dielectric Loss & Resistivity

Both types of equipment are used for testing the electrical properties of insulating oil, but their test parameters and applications differ. Below is a separate explanation:

1.Insulating Oil Dielectric Strength Tester

Main Test Items:

• Breakdown voltage of insulating oil (dielectric strength).

• Measures the voltage at which the oil sample is electrically punctured by gradually increasing the applied voltage.

Purpose:

• Evaluates the oil’s ability to withstand electric fields.

• Determines whether the oil contains moisture, impurities, bubbles, or other factors affecting insulation performance.

• This is the most basic and commonly used test for insulating oil in power systems.

Applicable Scenarios:

• Routine maintenance of oil-immersed equipment such as transformers, reactors, and capacitors.

• Periodic preventive testing.

2.Insulating Oil Dielectric Loss & Volume Resistivity Tester

Main Test Items:

• Dielectric loss factor (tgδ): Indicates the dielectric energy loss in the oil.

• Volume resistivity: Reflects the oil’s resistance to leakage current.

Purpose:

• Provides a more detailed assessment of oil aging, moisture content, and dissolved impurities.

• Can detect potential problems that may not be revealed by dielectric strength testing alone.

• Offers an in-depth evaluation of both oil quality and equipment insulation condition.

Applicable Scenarios:

• Situations with high requirements for equipment safety and reliability.

• Acceptance testing of new oil or post-maintenance evaluation of critical equipment.

• Further diagnosis of abnormal oil samples.

How to Choose?

• Basic Monitoring: If only routine, periodic testing is needed → Dielectric Strength Tester is sufficient.

• In-depth Diagnosis: If a comprehensive assessment of oil condition (aging, moisture, impurities) is required → Dielectric Loss & Volume Resistivity Tester is recommended.

• Comprehensive Application: Many power companies use both devices together, first screening with the dielectric strength tester, then confirming with the dielectric loss/resistivity tester. Combined use can build a complete insulating oil testing system, from basic to advanced, providing the most reliable protection for the safe operation of power equipment.