Insulation drying technology

CJSC SPA "TECHNOSERVICE-ELECTRO" provides all types of installation and repair work on the transformers with voltage of 35 - 750 kV. The company has a complete set of technological equipment and qualified personnel for the production of these works. Our service includes the following:

1. mounting of new power transformers of any size, including works on the conservation of the transformer equipment for long term storage,
2. overhaul and refurbishment of power transformers (autotransformers), including on-site work to replace coils and dry the paper-oil insulation,
3. modernization of obsolete transformers, including replacement and installation of new parts and components,
4. works with transformer oil oil-filled processing equipment and oil facilities with mobile units, including works on drying, purification from mechanical impurities, degassing, recovery and stabilization of oils. As well as work on drying of the sorbent, used in the operation of oil facilities and oil-filled equipment.
5. lifting work which encompasses lifting and moving of any heavy transformer equipment on site.
6. insulation drying technology.

SPA "TECHNOSERVICE-ELECTRO" performs overhauls of transformers (autotransformers) on site with a new advanced technology of washing and drying of the active part by spraying oil which contains detergents under vacuum. For each transformer we use the individual technology program of washing and drying. As a result, repair can significantly improve the insulating properties of the windings, maintain, and in some cases, increase the mechanical strength of the paper insulation and its degree of polymerization. All other known methods of drying transformers to a greater or lesser extent, lead to aging, degradation of paper insulation and loss of strength.

Flushing and drying technology developed by SPA "Technoservice-Electro" has been used successfully to restore the transformer insulation aged up to 55 years with various characters of sludge cover, dirt cover, moisture levels, and the degradation of solid insulation. Use of new technology of repairs actually allows extending the life of transformers.

Washing and drying of insulation

New technology of washing and drying of the active part of power transformers is based on the recommended in Guideline № 16363-87 circuit of drying by spraying of oil (for deep or partial vacuum).

The main difference of the new technology is the use of special flushing oil (solution), which has a higher solubility, and the use of individual technology program for each transformer. The parameters of the process of washing and drying are established basing on the results of diagnostic testing, character of sludge cover and contamination of the active part, the level of insulation characteristics, moisture content, the mechanical strength of the paper insulation and other factors.

This allows to successfully accomplish three tasks:

1. intensifying the process of extracting moisture from the solid insulation
2. effectively removing oil degradation products, iron and copper naphthenates, mechanical impurities and other sludge
3. preventing reduction of strength and accelerated degradation of the paper insulation during drying, and in some cases, even increase the degree of polymerization of paper up to 100-200 units.

Special flushing oil is prepared immediately prior to repair by entering additives and stabilizing ingredients into a clean and dry transformer oil to enhance its solvency and moisture-absorbing ability. Throughout the entire process the residual pressure in the tank, the temperature of oil and active part, the insulation resistances of the windings, physicochemical characteristics of flushing oil (breakdown voltage, tgδ, conductivity, acidity, class of industrial cleanliness, etc.) are constantly monitored. This allows to adjust the mode to achieve the optimal parameters: moisture content, degree of polymerization (strength) of the solid insulation, the insulation characteristics of the windings.

The efficiency of new technology is confirmed by the results of repair of various transformers, and laboratory tests. The proposed technique is most effective for transformers with a moist solid insulation (3%) or sludge-covered insulation (especially covered with oil degradation products, iron and copper naphthenates), as well as for aged (brittle) insulation.