I. Electrical Performance Tests
This section of tests is used to measure the insulation capacity and electrical stability of insulating oil, which is a fundamental test item for ensuring the insulation safety of power equipment. The specific sub-items are as follows:
1. Breakdown Voltage
Indicator Function: Measures the ability of insulating oil to resist electrical breakdown, being the core indicator for insulation strength, directly determining the basic insulation protection capability of the oil.
Testing Equipment: Insulating Oil Dielectric Strength Tester
Standards: GB/T 507, DL/T 429.9
2. Dielectric Loss Factor (tanδ)
Indicator Function: Reflects the energy loss of insulating oil under the influence of an electric field, enabling precise determination of the insulation aging degree and moisture content of the oil.
Testing Equipment: Dielectric Loss Tester
Standards: GB/T 5654, IEC 60247
3. Volume Resistivity
Indicator Function: Reflects the insulation resistance characteristics of insulating oil itself, assisting in supplementary judgment of the overall insulation performance of the oil, and combined with the dielectric loss indicator, it can comprehensively evaluate the oil quality status.
Testing Equipment: Can be shared with the dielectric loss tester, or a high-resistance meter can be used for testing separately
Standards: DL/T 421
II. Chemical and Physical Performance Tests
This section tests for oil deterioration, contamination, and safety hazards from a physical and chemical perspective, covering key dimensions such as oil aging, impurity content, and operational fire safety. The specific items are as follows:
1. Moisture Content
Indicator Function: Moisture in the oil significantly reduces the insulation strength of the oil, easily causing electrical faults. Therefore, moisture content needs to be strictly controlled throughout the process.
Testing Equipment: Karl Fischer Moisture Analyzer
Standards: GB/T 7600 (Coulometric Method), GB/T 7601 (Gas Chromatography Method)
2. Acid Value
Indicator Function: Directly determines the degree of insulation oil aging. A continuous increase in acid value will gradually corrode the internal solid insulation materials of the equipment, shortening the equipment’s service life.
Testing Equipment: Automatic Potentiometric Titrator
Standards: GB/T 264, GB/T 28552 (BTB Method)
3. Interface Tension
Indicator Function: Reflects the content of polar impurities in the oil and the trend of oil sludge formation. A continuously decreasing detection value indicates that the overall oil quality of the oil is gradually deteriorating.
Testing Equipment: Interface Tension Tester (Circular Method)
Standards: GB/T 6541
4. Closed Flash Point
Indicator Function: Affects the fire safety of power equipment in the field of operation. A too low flash point not only poses a fire and explosion hazard but also indicates that the oil has mixed in light distillates or there is overheating failure inside the equipment.
Testing Equipment: Closed Flash Point Analyzer
Standards: GB/T 261
5. Visual Inspection
Testing Method and Function: Through visual observation of the transparency, color, and internal mechanical impurities of insulating oil, it is the most basic and forward-looking detection step for oil entry and daily inspection.
Supporting Equipment: No dedicated detection equipment, using visual inspection method
III. Fault Diagnosis and Special Tests
This section is a targeted and in-depth detection project, mainly used to identify internal hidden faults in operating power equipment, predict potential safety risks, and meet the refined detection requirements for high-voltage and ultra-high-voltage equipment:
1. Dissolved Gas Component Content (Oil Chromatography Analysis, DGA)
Indicator Function: Detects the content and composition of characteristic gases such as hydrogen, methane, acetylene, ethylene, ethane, carbon monoxide, and carbon dioxide in the oil, accurately determining the types and severity of internal faults such as overheating and partial discharge in the transformer.
Testing Equipment: Gas Chromatograph
Standards: GB/T 17623, DL/T 703
2. Particle Pollutance Degree
Indicator Function: Detects the content of tiny solid particles in the oil. Tiny particles can easily induce local discharge faults. This indicator is crucial for the operational safety of high-voltage level power equipment.
Testing Equipment: Particle Counter Execution standards: ISO 4406, DL/T 432, DL/T 1096 (specifically adapted for equipment with voltage ratings of 500kV and above)
3. Corrosive Sulfur
Indicator function: Screen the content of corrosive sulfides in insulating oil to prevent sulfides from corroding the copper windings of the equipment and avoid problems such as winding damage and insulation failure of the equipment.
Execution standards: SH/T 0304, GB/T 25961
4. Oxidation Stability
Indicator function: Evaluate the ability of insulating oil to resist oxidation and deterioration. Combined with the detection data, it can scientifically predict the remaining service life of the oil, providing a basis for oil replacement and operation plan formulation.
Testing equipment: Rotating oxygen bomb
Execution standards: SH/T 0206, IEC 61125
Four. Key General Standards and Test Precautions
1. Core Execution Standards by Scenario
New oil acceptance: GB 2536 “Electrical Fluids – Unused Mineral Insulating Oil for Transformers and Switches”
Quality supervision of running oil: GB/T 7595 “Quality of Transformer Oil in Operation”
Preventive overall test of equipment: DL/T 596 “Procedures for Preventive Testing of Power Equipment”
2. Sampling Specification Requirements
The standardization of the sampling process directly determines the accuracy of all subsequent test data. The entire sampling operation must strictly follow GB/T 7597 “Sampling Methods for Power Oil (Transformer Oil, Steam Turbine Oil)”.
3. Differences in Stage-specific Indicator Limits
Insulating oil testing requires strict distinction among three stages: new oil, before commissioning/putting into operation, and during equipment operation. The qualified limit requirements for the same detection indicator vary significantly in different stages. Taking breakdown voltage as an example: The qualified limit value for the breakdown voltage of new insulating oil is ≥ 35kV; for insulating oil during operation of equipment with a voltage rating of 500kV, the qualified limit value is required to be ≥ 50kV. During operation and maintenance testing, it is necessary to strictly match the corresponding stage standards to determine whether the oil quality is qualified.
Post time: Jun-24-2026