Purpose of filtering transformer oil

The purpose of filtering transformer oil (insulating oil) is to remove moisture, gas and impurities in the oil, improve the dielectric strength of the transformer oil, protect the paper insulation in the oil, and improve the physical and chemical properties of the insulating oil to a certain extent.

Most distribution transformers are installed in the open air. The insulating oil (transformer oil) is affected by external impurities, contact with the air, and the high temperature of the equipment itself during operation, which gradually deteriorates the quality of the transformer oil. The deteriorated insulating oil (transformer oil) can not play the role of insulation and cooling well as it should.

In order to prevent the safe operation from being affected due to the deterioration of transformer oil quality, the regular oil samples of the power distribution in normal operation should be tested and analyzed, and the oil should be treated accordingly according to the analysis results. The inspection period for the oil chemical supervision of power distribution operation is stipulated to be at least once every 3 years.

Routine inspection items include acid value, water-soluble acid, flash point, breakdown voltage, appearance. It should be noted that if the equipment is often loaded with a relatively high load, the number of inspections should be increased on the basis of the specified test period; if some indicators of the inspected items are obviously close to the controlled limit value, the number of inspections should also be increased; The quality of running oil varies greatly with the degree of aging and impurities contained in it. Generally, a single test item cannot be used as the basis for evaluating the oil quality status. 

A comprehensive analysis should be carried out based on the measured main characteristic indicators.

1.       Acid value

The limit value is greater than 0.1mgKOH/g. There are four possible reasons for exceeding the limit value: overload operation; consumption of antioxidants; incorrect oil supplement; oil is contaminated. If the acid value exceeds the limit value, the following countermeasures can be taken: investigate the cause, increase the number of tests, determine the antioxidant content and add it appropriately, purify and regenerate the transformer oil, and change the oil if it is economical and reasonable.

2.       Water-soluble acid

The limit value is less than 4.2. There are two possible reasons for exceeding the limit value: oil aging; oil is contaminated. The following countermeasures can be taken for the water-soluble acid exceeding the limit value: increase the number of tests and compare with the acid value to find out the cause. Carry out Transformer Oil Regeneration and oil purification treatment, if economical and reasonable, you can do oil change treatment.

3.       Breakdown voltage

The limit value of breakdown voltage is less than 20KV. There are two possible reasons for exceeding the limit value: excessive water content in the transformer oil; contamination by impurity particles in the transformer oil. The following countermeasures can be taken for the breakdown voltage exceeding the limit value: find out the cause, carry out vacuum oil degassing treatment, plate and frame pressure oil filter machine or replace with new transformer oil. Generally, the breakdown voltage of the oil after DVOP double-stage vacuum transformer oil filtration treatment is required to be greater than 75KV, and greater than 60 KV after VOP single-stage vacuum transformer oil filtration treatment.

4.       Flash point

The limit value is less than 130℃, Or 5℃ lower than the previous test value. There are two possible reasons for exceeding the limit value: the equipment has a local overheating fault; wrong oil supplement. The following countermeasures can be taken for the flash point exceeding the limit value: find out the cause and eliminate the fault; carry out the degassing treatment with vacuum Transformer Oil Purifier, or carry out the oil change treatment.

5.       Appearance

If the oil is opaque by visual inspection, there are visible impurities or suspended matter. Or the oil color is too dark, the oil appearance is abnormal. The possible reasons for the abnormal appearance are: the oil contains moisture, fiber, carbon black and other solids. The following countermeasures should be taken for oil with abnormal appearance: If the oil is fuzzy, turbid and whitish, it indicates that the oil contains water, and the water content should be checked. If it is found that the oil contains carbon particles, the oil is black, or even has a burnt odor, it may be that there is an internal arc or partial discharge fault. It should be combined with other tests to investigate the cause and eliminate the fault. If the oil color is dark and the color of the oil changes significantly, attention should be paid to whether the aging of the oil is accelerated, which can be combined with the acid value test and analysis of the oil, or strengthen the monitoring of the operating temperature of the oil.

PureTech Oil Filtration is a professional and experienced manufacturer of Transformer Oil Filtration Machines and Transformer Oil Regeneration plants. Model DVOP Double-Stage High Vacuum Transformer Oil Filtration Machines are popular and highly praised by our clients because of its remarkable and outstanding effect in removing water, gas and impurities from transformer oil. According to different voltage levels and flow requirements, we have single-stage and double-stage different flows to meet the different needs of customers.

Contact us for more information about vacuum transformer oil filtration machines and transformer oil regeneration plants.

01 Vacuum Transformer Oil Filtration Machine (Double-stage)

02 Vacuum Transformer Oil Filtration Machine (Single-stage)

03 Vacuum Transformer Oil Regeneration Plant (Double-stage)

04 Trailer-mounted Vacuum Transformer Oil Filtration Machine

05 Plate and Frame Oil Filter Machine (Filter Paper type)

06 Portable Oil Filter Cart/ Portable Oil Filling Machine

PureTech Oil Filtration

Email: sales@cqpuretech.com

Tel: +86 17815389416 (whatsapp)

Web: www.cqpuretech.com