Long term improvements of all power transformers insulating system characteristics

Technology

VIMAP R2000 ON-LOAD power transformer oil-cellulose insulating system revitalization technology is based on the use of synthetic adsorbents. We began the development of our adsorbent technology in the early 1990’s, and presented our initial results at the DOBLE Conference (Boston, MA) in 1994. At that time, the utilization of synthetic adsorbents for reclamation of transformer mineral oils was an unknown technology. The technology of the time concentrated on the use of natural adsorbents such as Fullers earth, bleaching earth, bauxite and other infusion earths.

Considering that all cellulose and oil degradation products are polar our goal was to develop adsorbents with characteristics (such as proper pore diameter and developed activated surface) which could guarantee a high adsorption capacity of all polar molecules, including water. It was equally important to develop adsorbents that could be reactivated without losing adsorption capability. Further researches results and VIMAP R2000 ON-LOAD technology were presented at the CIGRE Paris 1996 and CIGRE Paris 2002 conferences.

Our research and development of adsorbents, their production and reactivation as well as their effect on insulation quality have continued to this day. We have engaged recognized University and Institutional laboratories and conducted numerous field tests.

Synthetic adsorbents remove all polar molecules from oil, including water, that result from the oil-cellulose degradation process.

Granulated adsorbents bind polar water molecules, acids, peroxides, furans, furaldehydes, ketones etc… and permanently bind these molecules on the activated surface pores whose diameter is precisely adapted to the diameter of the adsorbed molecule.

VIMAP R2000 ON-LOAD process is very simple and is based on the continuous recirculation of oil from the transformer through columns containing granulated adsorbents, where the polar molecules are bound.

Normally, the oil is pumped from the transformers lowest point (bottom valve), and is returned to the dilatation- condenser vessel.

The entire process is non-invasive and takes place optimally under defined flow at low pressure (cca. 1-2 bar). Insulation revitalization process is performed on site without interrupting transformer operation (on-load). During on load revitalization process numerous safety precautions are undertaken which guarantee safe and reliable transformer operation. This process is completely closed and independent of weather conditions.

During the on-load process while the the transformer is energized the core is heated and constantly maintains a solid insulation temperature higher than the temperature of the oil. reclamation of the oil, i.e. removal of oil degradation products, creates an imbalance between polar molecules in the cellulose and in the oil, which in conjunction with a temperature difference accelerates the transfer of polar molecules from cellulose to oil. Simply stated, initially all polar molecules in contact with adsorbents are removed, then during the extended process they pass from the cellulose to oil, thus deeply purifying and dehydrating the cellulose.

Saturated adsorbents can be reactivated a minimum of several hundred times via the VIMAP REACT2000 process, by which the complete oxidation of emitted harmful gases is achieved. Only CO2 and H2O, which are harmless for the environment, are emitted into the atmosphere. This makes VIMAP R2000 ON-LOAD technology environmentally more friendly then traditional thermo-vacuum and oil-spray technology.

In addition, VIMAP equipment is characterized by its modularity, therefore it can be adapted/optimised to any transformer size and location, because one VIMAP system is combinable with a varying number of adsorbent columns, varying pump capacities etc., depending on the requirements.

Advantages of VIMAP R2000 ON-LOAD technology over conventional ones:

» Most complex power transformer treatment that is possible to perform in terms of results achieved, ie. complete oil-cellulose system revitalization

» No oil evacuation from transformer

» No transformer vacuuming

» No oil overheating

» Possibility of both off-load and on-load treatment

» Low electric power consumption

» Zero emission

» Low price of machinery

In comparison to the oil replacement benefits of VIMAP R2000 ON-LOAD technology are numerous:

» After oil is replaced, 15-20% of old, aged oil remains in cellulose insulation and degrades characteristics of new oil. Deposits of sludge remain between radiator ribs and between windings, dissolve in new oil activating oxidation processes

» New oil has a high price and it is expensive and complicated to replace

» Large quantity of new oil is required for flushing of transformer’s interior purposes

» No disposal of used oil.

Technology