NB/T 10199-2019Fluids for electrotechnical applications - Unused natural esters for transformers and similar electrical equipment (English PDF)

3.1 Natural ester

Vegetable oils extracted from seeds or oils extracted from other suitable biological materials are mainly composed of triglycerides.

3.2 Potentially corrosive sulfur

The presence of organic sulfur compounds in transformer oil may lead to the formation of copper sulfide.

3.3 Unused natural ester

Unused natural ester delivered by the supplier.

Note 1. The liquid has not been used, nor has it come into contact with electrical equipment and unnecessary equipment during its manufacturing, storage and transportation.

Note 2. Manufacturers and suppliers of unused natural esters will take all reasonable precautions to ensure that natural esters are not affected by PCBs, PCTs, and polycyclics.

Contaminated by aromatic hydrocarbons (PCB, PCT, PCAs) or corrosive sulfur compounds; and not be contaminated by used oil, recycled oil, dechlorinated oil or other pollutants

5.1 Performance requirements

See Table 1 for the performance requirements of unused natural esters.

Note: CIGRE 436 and IEEE C57.147 provide supplementary information on natural esters used in transformers and similar electrical equipment.

5.2 Performance meaning and test methods

5.2.1 Physical properties

5.2.1.1 Appearance

Use a transparent glass container (with a diameter of not less than 10cm) to sample, and observe the unused natural ester with the naked eye (allow the However, the light penetrates the natural ester about 10cm thick) to determine whether there are visible pollutants, free water, and suspended solids.

5.2.1.2 Kinematic viscosity

The kinematic viscosity at 40°C and 100°C is measured in accordance with GB/T 30515.

Kinematic viscosity affects heat dissipation, which will cause the temperature in transformers and other electrical equipment to rise. The lower the kinematic viscosity, the easier the insulating liquid Circulation, the better the heat dissipation effect. Viscosity at low temperatures is a key factor in the cold start of transformers (poor circulation may cause hot spots to overheat). It's loaded The speed of moving parts such as pressure regulators and pumps can have a negative impact. The kinematic viscosity at the lowest cold operating temperature (LCSET) should be properly considered degree.

5.2.1.3 Pour point

The pour point is measured in accordance with GB/T 3535. The pour point is the lowest temperature at which natural esters can flow.

The crystallization of natural esters depends on time and temperature. At operating temperature, there should be no crystals in the insulating liquid. If the temperature in electrical equipment If the temperature is lower than 0°C, the thermal and dielectric properties of the natural ester equipment may be adversely affected, and preventive measures should be taken. Not sure yet Method of determining crystallization.

5.2.1.4 Water content

The water content is measured in accordance with NB/T 42140. The water content of natural ester affects its dielectric properties.

Note: Due to the medium polarity of natural esters, free water will appear in natural esters and cause deterioration of dielectric strength, and its water content is significantly higher than that of mineral insulating oils.

5.2.1.5 Density

The density is measured in accordance with GB/T 1884 or SH/T 0604.

5.2.2 Electrical performance

5.2.2.1 Breakdown voltage

The breakdown voltage is measured in accordance with GB/T 507. Due to the different nature of natural esters, the initial time needs to be set during measurement, generally 15min~30min to ensure that there are no visible bubbles in the natural ester before the measurement.

5.2.2.2 Power frequency dielectric loss factor (DDF)

The power frequency dielectric loss factor is measured at 90°C in accordance with GB/T 5654 or GB/T 21216. In case of dispute, proceed in accordance with GB/T 5654 Determination.

The power frequency dielectric loss factor is the dielectric loss caused by the insulating liquid. The high power frequency dielectric loss factor indicates that the insulating liquid is affected by water molecules, Particles or soluble polar pollutants are polluted or the insulating liquid is of poor refining quality.

5.2.2.3 Relative permittivity (relative permittivity)

The relative permittivity is measured at 90°C in accordance with GB/T 5654 or GB/T 21216. In case of dispute, the determination shall be conducted in accordance with GB/T 5654.

The relative permittivity refers to the ratio of the electrical energy stored in the insulating liquid under the applied voltage to the electrical energy corresponding to the vacuum.

Note: The typical value of relative permittivity. 2.8-3.3.

5.2.3 Chemical properties

5.2.3.1 Acid value

The acid value is measured in accordance with IEC 62021-3.The unused natural ester should be close to neutral.

Note: Natural esters may contain lower concentrations of free fatty acids, and the presence of free fatty acids will affect the acid value of natural esters.

5.2.3.2 Corrosive sulfur

Corrosive sulfur is measured in accordance with GB/T 25961 or DL/T 285. Under standard conditions, the swimming is detected by contacting copper with insulating liquid From corrosive sulfur and potentially corrosive sulfur compounds. Known corrosive sulfur compounds such as dibenzyl disulfide (DBDS) should not be detected (GB/T 32508).

Note: Corrosive sulfur compounds do not naturally exist in vegetable oils or other natural esters. Tests prove that additives are non-corrosive and will not cause potential Cross contamination of corrosive oil.

5.2.3.3 Additive content

The content of antioxidant additives is determined in accordance with IEC 60666 or other appropriate methods.

Additives include antioxidants, metal deactivators, pour point depressants, etc. Antioxidants slow down the oxidation of natural esters, reducing gel and acidity The formation of substances, such as 2,6-di-tert-butyl-p-cresol (DBPC), also known as BHT, can also use other antioxidants. Total additive The amount should be less than 5% (mass fraction).

Upon mutual agreement, the supplier shall declare the general types of all additives, as well as the concentration of antioxidants and passivators. Initial of additives The type and concentration can be used for the supervision and maintenance guidance of natural esters in transformers and similar electrical equipment during operation.

5.2.3.4 Furfural content

2-furaldehyde and related compounds are measured in accordance with NB /SH/T 0812.

Furan compounds, including 2-furaldehyde, are degradation products of kraft insulation paper. These compounds are usually not found in unused natural esters. in.

Note: There may be traces of certain furan compounds in unused natural esters.

5.2.4 Oxidation stability characteristics

The oxidation stability of natural esters can be determined with reference to the method described in NB /SH/T 0811.

Due to easy oxidation, unused natural esters are only suitable for airtight equipment.

Note 1. The oxidation stability characteristics relate to the performance of natural esters under high electrical stress and temperature conditions in long-term operation. GB/Z 1094.14 lists natural The allowable operating temperature of the ester.

Note 2. For natural esters, see Appendix A for the methods that can be adopted by NB /SH/T 0811 after modification.

5.2.4.1 Total acid value

The total acid value is determined in accordance with 10.3.4 of NB /SH/T 0811.

5.2.4.2 Kinematic viscosity

For the determination method of kinematic viscosity, see 5.2.1.2.

5.2.4.3 Power frequency dielectric loss factor (DDF)

After the oxidation stability test, the dielectric loss caused by the water produced by oxidation and the soluble polar compounds in the natural ester should be measured. See 5.2.2.2 for the method.

5.2.5 Health, safety and environmental characteristics

Note: It involves the safe handling of natural esters and the minimization of adverse effects. Including flash point and ignition point, polycyclic aromatic hydrocarbons (PCA) and PCBs/PCBs (PCBs/PCTs).

5.2.5.1 Ignition point and flash point

The flash point is measured according to GB/T 3536, and the flash point is measured according to GB/T 261.

5.2.5.2 Polychlorinated biphenyls (PCBs)

The concentration of PCBs is determined in accordance with SH/T 0803, and the total concentration should not be greater than 2mg·kg-1. Unused natural esters should not contain PCBs.

Note: PCBs and related compounds can only be present in unused natural esters due to cross contamination.

5.2.5.3 Biodegradability

The degree of biodegradation is measured in accordance with GB/T 21856, GB/T 21802 or GB/T 21801.

Compared with petroleum-derived mineral insulating oils, natural esters have better environmental compatibility.

Note: According to the tested biodegradability, natural esters can be classified according to IEC 61039.

5.2.5.4 Toxicity

Unused natural esters should be non-toxic, and the supplier should provide tests to prove that the product is non-toxic.

Note: The toxicity of natural esters can be evaluated by related test methods, such as referring to the Ames test or other appropriate methods, such as OECD 201-203.

A.1 Overview

Natural ester adopts NB /SH/T 0811 similar accelerated aging test method to evaluate oxidation stability. Put the natural ester sample to be tested With solid copper catalyst, a constant volume of air is blown into the natural ester at 120°C for 48 hours. By measuring the volatilization of natural esters after oxidation Evaluate its anti-oxidation ability by generating acid value, oil-soluble acid value, sludge formed, kinematic viscosity and dielectric loss factor. And will accelerate oxidation The parameter values obtained afterwards are compared with the performance values before accelerated oxidation.

A.2 Test conditions

The accelerated aging duration is set at 48h, and other test conditions such as the amount of natural ester, the length and diameter of the copper wire catalyst, and the oxidation temperature The temperature and oxidant (air) flow rate should be exactly the same as the NB /SH/T 0811 test method.

A.3 Accuracy

The accuracy values obtained after 48h oxidation through the comparison test of commercial natural esters are shown in Table A.1.The relative reproducibility of each parameter is based on Results obtained by participating laboratories. The value reported in Table A.1 is basically consistent with the value reported for mineral insulating oil in NB /SH/T 0811.

A.4 Repeatability (r)

Repeated values given by the same laboratory at the 95% confidence level.

A.5 Reproducibility (R)

Repeated values given by different laboratories at the 95% confidence level.