Insulation fluids are used in many types of high voltage equipment: capacitors, cables, switches, transformers etc. The fluids usually perform two main functions, i.e. electrical insulation and cooling. Some extra functions are arc extinguishing in switchgear and protection of the internal solid insulation from moisture in the environment.
Why transformer oil filtration is important
Due to massive use of transformers in the power industry, transformer oil is the most important of all electrical insulation fluids. The heat and electricity, as well as oxygen from the environment and the transformer construction materials all impact the oil during use. These processes result in contamination with particulate matter, water, gases, acids, sludge and decomposition products as well as other substances which degrade the performance of the oil. Contaminated oil cannot reliably protect the transformer from electric breakdown and efficiently dissipate heat from components parts. Therefore, it is important to monitor the condition of the oil and maintain it as specified in standards and regulations. Transformer oil filtration is a part of a larger process of oil purification to restore the oil’s vital parameters and performance.
Transformer oil filtration basics
In general case, transformer oil filtration involves separation of suspended particles from the oil by passing the oil through a porous barrier. To reduce the amount of impurities before filtration, the fluid is kept in settling tanks, then the bottom sludge is drained carefully.
Transformer oil can be filtered in screen presses. The oil is pushed through the filtration medium, usually paper or cardboard. Due to the large number of capillaries in this material, particles larger than 10-15 micron are captured. It should be noted that filtration can be performed both before filling a transformer with fresh oil (to remove impurities after transportation and storage) and after having used the oil in the transformer for some time.
The process above has several limitations:
- long settling time;
- low filtration throughput;
- the need to replace filter media often;
- possible contamination of oil with cellulose fibers which reduce its dielectric strength.
GlobeCore Transformer oil filtration technology
GlobeCore has developed the CMM units for transformer oil filtration. In these units, the oil passes is sucked by a pump through an inlet filter and then goes to one or both filtration sections. Each section is equipped with a coarse and a fine filters. After filtration the oil is pumped out of the unit.
The advantages of GlobeCore CMM units are:
- two filtration sections allow filter change simultaneously with oil filtration;
- 25, 5 and 1 micron filter elements can be installed;
- a magnetic separator is installed in the filter vessels for effective removal of metal particles;
- small size and simple filter element replacement.
GlobeCore also offers other CMM modifications, which include Fuller’s earth as a special adsorbent. It does not remove solid particles like mesh filters, but it traps water, sludge and aging products from the oil. After saturation, the adsorbent can be reactivated inside the unit (by cleaning out the pores) and can be used for up to 300 reactivation cycles. This is the equivalent of several years of transformer oil filtration equipment operation..