Mineral oil is used in transformers as liquid insulation and coolants. Owing to their function, the dielectric properties must be well maintained so that heat transfer and chemical stability is present throughout the operations.

Ageing of transformer oil

Ageing of the transformer denotes ageing of the entire insulation, especially the oil. Decrease of dielectric strength and premature failures owe themselves to the humidity and foreign particles which affect the interfacial tension of the oil.

A colour index close to 3 does not determine the quality of the oil, since more than two or three parameters confirm the oil degradation. Repeated and frequent oil sampling is required to avoid damages and repairs.

When the transformer oil is degraded, ageing occurs and performance suffers a setback. Heat, oxidation and moisture aggravate the ageing process and the used transformer oil must be replaced with new one.

Such replacement is not only costly but also drastically affects the ecosystem. Effectiveness of adsorbent technology using fuller’s earth and reclamation process is gaining popularity whose results are widely lauded. Even though the lifespan of a transformer is 20 to 30 years, a well-maintained transformer can last up to 50 to 60 years.

Reclamation of transformer oil

Reclamation is a process of restoring the “as good as new” value of transformer oil by removing acid, sludge and oxidation products and curbing the ageing rate of the oil. Though oxidation is the main reason for ageing, oil temperature, metals like copper and iron have a role in the aging process.

Reclamation is inevitable when neutralization number, interfacial tension and dissipation factor are far from the prescribed values. The soluble and insoluble contaminants are removed by combining the chemical and physical processing which is an efficient and cost effective method to restore transformer oil.

Deposition rates of contaminants depend on the size of particles and difference of density between them. Centrifugation followed by dehydration reduces gas to water content and oil passes to the adsorbent treatment where oil is subjected to selective retention of contaminants.

Hering’s unbeatable German precision

Hering’s line of products for transformer maintenance include transformer oil purification systems, regeneration systems, PCB removal systems, vacuum transformer drying ovens, waste oil recycling plants, reactivation clay polishing system, TIDO series online transformer insulation drying and degassing systems and ISODRY series online transformer insulation drying systems.

Hering’s robust design is easy to operate and maintain and is custom made. The modules can be shipped in a 40 ft container thus reducing shipping and handling costs.

Hering is committed to fighting transformer oil deterioration and trains clients in online and offline oil processing and transformer drying activities. They customize the systems according to client requirements so that the benefits are optimized.