1. POWER TRANSFORMERS
The main objective of our work is to do qualified diagnostics that is carried out on a nominal loaded transformer. The real technical status and the necessary scope of repair works as well as the necessity of modernization can be determined.
The diagnostics is based on the following input data:
· Determination of moisture content and hard insulation by the method of desorption and by measuring of transformer model;
· Standard and non-standard electric measurement of the main characteristics of the insulation;
· Full scope of physicochemical analysis of transformer oil;
· Gas chromatography of dissolved gases in the oil (the analysis is done in the Russian Scientific Electric Institute of Moscow).
· Thermovision of the transformer at different loading;
· Determination of the status of the insulation using the electric method by measurement of partial discharges both in nominal stationary mode and in load variation;
· Measurement of tg d at nominal voltage at different modes of loading;
· Liquid chromatography for determination of polymerization level of insulating paper;
· Measurement of noise and vibration of the machines as a whole unit and of its separate components and details;
· Liquid chromatography for determination of polymerization level of insulating paper;
· Measurement of noise and vibration of the machines as a whole unit and of its separate components and details;
The repair works are carried out on site by a company's team consisting of high qualified Bulgarian and foreign (from Russia and the U.S.A.) specialists.
We use modern methods for treatment of main insulation, which are analogous to the methods of companies Micafil, National Industry, Hedrih.
The drying of insulation is done through injection of special cleaning hot transformer oil under deep vacuum and for each transformer a particular scheme is worked out depending on its design and diagnostics` results.
All operations are fulfilled by a high- technology thermovacuum installation of Micafil Company, type VH 121 RS made after our special order.

2. HIGH-VOLTAGE BUSHINGS FOR TRANSFORMERS
We carry out full scope diagnostics using some of the above-mentioned diagnostics` methods and we are able to assess with high precision the rest lifetime and the probability of failure.
We replace high-voltage bushings and the new ones are chosen and delivered after we have made full electric calculations of the electric field of the bushing and structure of the transformer.
We have at our disposal a design and technological documentation of all Russian bushings installed in Bulgaria manufactured by the Moscow Plant Isolator.

3. ON LOAD TAP CHANGERS (OLTC)
One of the most qualified teams in diagnostics, repair works, rehabilitation and replacement of on load tap changers of power transformers works in our company.

4. DIAGNOSTICS AND REPAIRS OF HIGH-VOLTAGE ENGINES, HYDRO-GENERATORS AND TURBO-GENERATORS
The diagnostics of high-voltage engines, hydro-generators and turbo-generators is performed in accordance with both commonly adopted traditional methods which are regulated by standards and Norms and following up-to-date methods such as measurement of the level of partial discharges at different voltages and temperatures, study change of DDF (tg d) and ? tg d at different voltages and temperatures.
Combination of the two methods gives the opportunity to determine the real technical status of worked insulating system (windings) and to set the quality of the manufactured new ones.
Our company has reach experience in controlling and manufacturing high-voltage sections of different design. We designed, produced and delivered more than 1800 PCs sections of 6 kV for the needs of TPP Varna. We supervise regularly the manufacturing process of section at the site of the Central Repair Base in Sofia.
DIT - M Ltd. in the area of insulating work together with the Russian Scientific Electric Institute worked out new type insulation system for high-voltage rotating machines used for repairs and with high quality as regards dielectric strength and moisture capacity. It is a phenomenon fact that manufactured sections keep for a time their elasticity and after placing they polymerize (themselves). In this state the sections are superb thermosetting insulation.
Experts from our company took part in restoration work of turbo-generators` windings at TPP Russe-East using copper and replacing the insulating system. Insulating elements were produced (stator wedges, insulating boxes to the front parts). For that purpose were prepared technical documentation and instrumental equipment.
In the area of hydro-alternators together with the Russian Scientific Electric Institute, DIACS JSC Rosenergoatom and the American Company IPDD, which is a subsidiary of Westinghouse, was worked out restoration technology for the insulation of the winding stator with use of all old insulating materials.
A number of studies of turbo-generators of a power capacity 6, 25, 30, 60, 165 and 200 MW and voltage up to 18 kV were performed. Residual life of the machines was determined. Concrete technical decision regarding life elongation of insulating systems and raising their reliability was recommended.
In co-operation with the German Company THYSSEN GmbH carry out reconstruction and modernization of banding and centering rotors` rings of turbogenerators. Such work was carried out for the first time at TPP Varna on turbo-generators type TBB - 210 - 2A.