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Testing Treatment Of Transformers Insulating Oil

August 13,2017.

1. The acceptance of the new transformer oil

Acceptance of new transformer oil should be GB2536-1990 transformer oil acceptance.

The test items are temporarily: appearance, pour point and pour point, flash point (closed), breakdown voltage, dielectric loss factor, moisture and other items.

2. The new transformer oil treatment

New transformer oil in the transport and storage process, can be mixed with mechanical impurities, moisture and other harmful substances, from GB2536-1990 transformer oil and GB/T 7595-2000 can also be seen, the new transformer oil acceptance after passing can’t be used directly, To the corresponding treatment of the new transformer oil, the transformer oil performance indicators in line with GB / T 7595-2000 in the transformer oil quality standards in operation before the oil quality standards can be filled into the use of electrical equipment. Transformer oil treatment methods are mainly filter, and some dehydration degassing, oil treatment and other processes. Now there are sets of transformer oil treatment system, one can complete the transformer oil filtration, degassing, dehydration, purification process.

3. The transformer oil storage

The newly purchased transformer oil and the treated oil are stored separately. In order to prevent the filter of a good transformer oil mixed with impurities, suction and suction, etc., to filter a good transformer oil vacuum storage, that is stored in a vacuum tank in order to always add to the electrical equipment. Due to the degree of contamination of the transformer oil is different, it is possible to filter the transformer oil can’t meet the standard, the need for secondary filtration, therefore, in the process of filtering the transformer oil to test, there may be applied to the middle tank, filter once Of the transformer oil into the middle of the tank, the second filter of qualified oil into the qualified tank.

4. Transformer oil testing

According to GB2536-1990 transformer oil and GB/T 7595-2000 in the transformer oil quality standards, combined with the actual situation, to be carried out about the transformer oil test, test items:

① appearance.

② pour point, pour point.

③ closed flash Point.

④ acid value.

⑤ breakdown voltage.

⑥ dielectric loss factor.

⑦ water.

⑧ chromatography analysis.

5. The transformer oil sampling

5.1. Sampling

Implementation of standards: GB / T7597-1987 DL / T1452-2005

Sampling tools: tea grinding glass bottle 500ml, 1000ml

Metal small mouth seamless container 350ml 100ml glass syringe

Sampling tool requirements: drying at 105 ° C

5.2. Sampling volume:

Cylinder oil: ≤ 10 barrels all > 10 barrels of about 10% to 20% mixed evenly

Tanker: the bottom of the sample, take 2 copies, 1 for the test, 1 backup, 1 reserved for more than 3 months

5.3. Sampling rules:

Bad weather (rain, snow, fog, windy days are not outdoors sampling), inevitably do not pollute the oil

The container should be dry, the container mouth with a clean cotton cloth wipe, release part of the oil rinse sampling port and catheter

Start sampling to allow oil to flow along the container wall, to avoid bringing more air casing, the transformer must be sampled when the power outage

For special tests, please use a special test

The need to use the syringe must check the sealing performance of the syringe

Each sample should have an accurate mark

6. Transformer oil test

6.1. Appearance

Test method: visual inspection

Quality standards: transparent, no impurities or suspended solids

New oil is generally light yellow, China's production of transformer oil, especially the No. 45 transformer oil, due to cut the lower temperature of the fraction, and the use of excessive refining and antioxidant process, the appearance of the color lighter, almost colorless. Transformer oil in operation, affected by the environment and their own oxidation of resin and other factors, the color will gradually deepen. Transformer oil color of the rapid changes in the oil is usually generated when the arc caused by carbon.

6.2. Pour point, pour point

Testing method:

Solidifying point:

Implementation of the standard: GB / T 510

Method of operation: the test sample installed in the test tube, and cooled to the expected temperature, the test tube tilted 45 ° after 1min, observe whether the flow of liquid.

Calculation and judgment: When the test tube tilted 45 ° angle after 1min, the liquid does not flow the maximum temperature, that is, the freezing point.

Precision: The same operator repeated the difference between the two results should not exceed 2.0 ℃.

Note: ⑴ to strictly control the cooling rate, can’t be too fast; ⑵ measured the temperature of the thermometer in the test tube position must be fixed firmly; ⑶ sample to do a test, you must reheat to 50 ± 1 ℃, do Next test. ,

Pour point:

Implementation of the standard: GB/T 3535

Method of operation: the sample after preheating, at the required speed of cooling, every 3 ℃ check the flow of a sample.

Calculation and judgment: observe the sample can flow the minimum temperature, that is, pouring point.

Precision: The same operator repeated the difference between the two results should not exceed 3.0 ℃.

Note: the same sample measured on the pour point and pour point is not exactly the same, generally pour point higher than the freezing point 1 ~ 3 ℃.

6.3. Closed flash point

Implementation of the standard: GB/T 261

Method of operation: the sample in a continuous stirring, with a very slow constant speed of heating. In the case where the provisions are temperature intervals and interruption of agitation, a small flame is introduced into the cup, and the experimental flame causes the minimum temperature at which the steam flashes on the pattern is the closed flash point.

Calculation and judgment: the effect of atmospheric pressure on the flash point of the correction, according to the following formula ⑴ or ⑵ calculated at the standard atmospheric pressure 101.3kPa or 760mmHg column flash point correction number Δt (℃)

Δt = 0.25 (101.3-P) ⑴

Δt = 0.0345 (760-P) ⑵

Precision: the same operator to determine the difference between the two results should not exceed the following values:

Flash point range (℃) Allowable difference (℃)

104 or less than 104 2

Higher than 104 6

Note:⑴ Oil cup in the amount of the sample, just to the carved line

⑵ Ignition with the flame size to be strictly in accordance with the provisions

⑶ Strict control of heating rate, not too fast or too slow

⑷ Kind of water content greater than 0.05%, must first dehydration; ⑸ in the ignition process, the first ignition, after watching the temperature.

6.4. Acid value

Implementation of the standard: GB264--83

Method of operation: 95% ethanol (neutralized) mixed with the sample, boiled for 5 minutes, then add the indicator, hot with 0.05 potassium hydroxide solution of ethanol titration.

Calculate and judge:

X = (56.1 • V • N) / G

V - Consumption of potassium hydroxide / ethanol solution volume.

G - Concentration of sample

N - Potassium hydroxide / ethanol solution equivalent concentration

Precision: The same operator repeated the difference between the two results should not exceed the following values

Range, mg KOH / g Repeatability, mg KOH / g

0.00 to 0.1 0.02

0.1 to 0.5 0.05

0.5 to 1.0 0.07

1.0 to 2.0 0.10

Note: During each titration, the time from the conical flask to stop heating to the end point should not exceed 3 minutes.

6.5. Breakdown voltage

Implementation of the standard: GB / T 507-2002

Method of operation: will be filled with samples of the sample cup into the measuring instrument, slowly boost to the sample was breakdown.

Judgment: The breakdown voltage is the maximum voltage when the circuit is automatically disconnected or manually disconnected.

Note: (1) to ensure that the sample before and after loading the sample cup can’t produce bubbles, the electrodes can’t have bubbles.

(2) During the test if the use of mixing, it must be maintained.

(3) Fill in the report should include: sample name, each breakdown voltage, electrode type, voltage frequency, oil temperature

6.6. Dielectric loss factor

Implementation of the standard: GB / T5657-85

Method of operation: the use of dielectric loss factor instrument resolution of 10-4 frequency bridge, the best use when the sample capacitance of 100pF with 10-5 resolution bridge

6.7. Moisture

Implementation of the standard: GB / T260-77

Method of operation: 100 grams of sample and anhydrous solvent mixture, the method of distillation to determine the level of oil content of water.

Precision: In the two measurements, the volume difference of the collected water should not exceed a scale of the receiver, the moisture content of the sample is less than 0.03%, that is traces, there is no water in the receiver, that the sample anhydrous The

6.8. Chromatographic analysis

Implementation of the standard: GB / T17623-1998

Method of operation: the oil sample dissolved gas, with gas chromatography separation, detection of the gas components and content.

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