Mechanical Impurities in Transformer Oil

1. What do mechanical impurities in transformer oil refer to? Where did it come from?

Mechanical impurities in transformer oil refer to the precipitated and suspended substances in the oil that are insoluble in solvents (gasoline or benzene), such as sand, iron particles, insulating fiber fragments, free carbon, etc., but the impurities measured by the current method also include some organic components that are insoluble in solvents, such as carbides formed after oxidation.

Impurities mainly come from the transportation and storage process of oil. If the oil container is not cleaned or the container is not tight, impurities such as rust or dust will be mixed into the transformer oil. When filtering and regenerating transformer oil, impurities may also invade the oil. For example, organic fibers can fall off the filter paper; solid insulating materials continue to deteriorate and fall off during use, mixed into the operating transformer oil; during the refining process of new oil, it may also be mixed with fuller’s earth, impurities in additives and other mechanical impurities.

2. The principle of the determination method of mechanical impurities in transformer oil and the disadvantages?

The determination of mechanical impurities in transformer oil is a quantitative analysis method. After diluting the transformer oil with a solvent, then filter it with filter paper or other filters to separate the solid suspended particles contained in the oil, then rinse all the oil with the solvent, dry and weigh (constant weight), and determine The result is expressed as a percentage.

The disadvantages are:

1). The measured impurities contain some organic components in transformer oil. The mineral particles, which are mainly composed of mechanical impurities, are still adsorbed with a considerable amount of organic matter although they are cleaned by solvent on the filter.

2). The measured results vary with the solvent used, the density of the filter holes, and the filtration speed.

3). When measuring the impurities in transformer oil which is heavy and contains a lot of jelly, alkalis insoluble in solvents are also detected as mechanical impurities.

4). The measurement environment needs to be clean, and the indoor atmospheric dust often affects the measurement results.

3. What should be paid attention to when measuring mechanical impurities in transformer oil?

1). Shake well before weighing the sample.

2). All solvents should be filtered before use.

3). The density, thickness, type and quantity of the filter paper used should be the same.

4). The clean filter paper should not be dried together with the used filter paper with precipitation in the same oven, so as to prevent the clean filter paper from adsorbing solvent and transformer oil vapor and affecting the constant weight.

5). After the specified cooling time, weigh immediately. So as not to delay the time, due to the moisture absorption of the filter paper, affect the constant weight.

6). The filtration operation should strictly follow the relevant regulations of gravimetric analysis.

7). The solvent used should be selected based on the analysis of the specific conditions of the sample and the relevant provisions of the technical standards, and should not be used indiscriminately. Otherwise, the measured results cannot be compared.

4. The conventional methods of Transformer Oil Filteration mainly include the following:

1). Plate and frame oil filter press. Filtering the mechanical impurities and a small amount of water in the transformer oil through filter paper. However, it has the disadvantage that the organic fibers on the filter paper may be mixed into the oil to cause secondary pollution. At the same time, the filter paper needs to be replaced continuously to ensure the filtering effect.

2). Portable oil filter cart. The mechanical impurities in the transformer oil are filtered through the multi-stage filter element, and it can also be used as an oil transfer device to pump the transformer oil in the oil storage tank into the transformer or pump the oil out of the transformer. The disadvantage is that the moisture in the transformer oil cannot be removed.

3). Vacuum Oil Purifier. It is currently the most commonly used transformer oil treatment plant. Combining thermal vacuum dehydration and degassing, multi-stage precision filtration technology, it can effectively remove mechanical impurities, moisture and gas in the transformer oil without affecting the components of the transformer oil itself. Thereby quickly improve the dielectric strength of transformer oil.

4). Transformer oil regeneration unit. Through the regeneration of transformer oil, the carbide and other decaying products formed by oxidation in the transformer oil can be effectively removed. It can also be used in series with a vacuum Transformer Oil Purifier, or use PureTech's transformer oil vacuum oil regeneration plant, which can achieve multiple functions of vacuum dehydration and degassing, filtering and removing mechanical impurities and Transformer Oil Regeneration on one device.

For more information on the treatment of transformer oil, please contact us.