Tag Archives: oil reclamation

Quality Assurance: Methods of transformer oil testing

Quality of transformer oil is tested in several stages of its use. Regular control of the oil’s quality is a part of the process of servicing electric equipment. The main parameters of oil and its purity indicate transformer condition.

The ability of the oil to maintain its original properties during operation of electric equipment is referred to as oil stability. If the equipment has not defects and operates without failures, the parameters of new oil change very slowly. New transformer oil has light color and complies with regulations, which define the oil’s dielectric strength and other properties. In use, stability of the oil decreases and notable changes occur, the color changes to dark.

Poor oil quality is indicated by high ash content, increased acidity and presence of low molecular acids. Acidic sludge forms in contaminated oil, which disrupts cellulose insulation and reacts with the metals of the transformer’s internal components.

Oil tests can identify the beginning of oil degradation.

The main physical and chemical properties tested are the oil’s dielectric strength, dissipation factor, flashpoint, color, solid, water and gas content as well as acid number.

Dielectric strength is one of the most important indications of oil stability and this is often the first test performed. It is calculated as an average of five breakthrough achieved in a standard discharger with two electrodes at 2.5 mm distance. Six breakthroughs are achieved in the test and the last five are averaged. If the oil is fresh, the lowest allowable breakthrough voltage is 30 kV. In some transformers, that is as good as needed.

Decreasing dielectric strength indicates contamination of the oil by gas, moisture, cellulose fibers or other particulate matter.

A similar process is used to calculate dissipation factor. The oil’s ability to neutralize energy, prevent breakthroughs and cool the transformer is characterized by the oil’s quality and purity, or acidity. In general, increased dissipation factor means degradation of the oil’s dielectric capabilities.

The color of transformer oil changes from light yellow to cloudy brown under the influence of temperature, contaminants and current. The color is not in itself an indication of any specific problem, but dark color is usually an indication of aged oil.

The presence of solid particles and the acid number of the oil are related. Unsolved materials accumulated in the oil in the form of sludge or suspended particles (fibers, dust, solved paint, metal particles, ash etc) degrade the oil’s dielectric properties and promote oil oxidation. The more particles are present in the oil, the faster the oil ages. The acid number is expressed as milligrams of KOH required to neutralize all acids in a gram of oil and indicates the degree of oil aging. Normal acid number is 0.25 mg KOH/g, while the limit of contaminant content is 515 ppm.

Moisture and gas content in transformer oil is tested thoroughly, because water and air are some of the main “catalysts” of oil aging process.

Moisture content is measured as amount of hydrogen when reacting the oil with calcium hydride in a certain time. Gas content is measured by an absorptiometric analyzer or a chromatographer.

Flashpoint and setting point are indications of general fire safety of the oil and its ability to operate in adverse temperature conditions.

Therefore, the advantages of testing and analyzing transformer oil before starting electric equipment and during regular maintenance, allow to determine the equipment’s efficiency, operation conditions and possibility of malfunctions. If the purity and quality regulations are followed, the facility is safe from failure and downtime of equipment and related repair costs.

Reclamation of oil

Oil reclamation today is a very interesting and important subject. Oils can be reclaimed in a number of ways by different equipment and to varying extent.

Oil reclamation equipment developed and built by GlobeCore varies widely in terms of applications and reclamation degree:

  • oil regeneration
  • heat and vacuum purification of oil,
  • purification of oil by adsorbents
  • drying of transformer windings,
  • dehydration of oil,
  • degassing of oil,
  • reactivation and preparation of sorbents, including full regeneration of MINERAL oils with color lightening.

The following is a brief list of GlobeCore’s equipment for oil reclamation and other applications.

  • Themovacuum oil purification units, mobile oil plants: СММ-0.6; СММ-0.7(Р); СММ-0.6; СММ-1.0; СММ-1.7; СММ-2.2; СММ-4.0; СММ-4.3 and some other models;
  • Comprehensive oil restoration units, including heating, nitrogenation, drying and filtration of insulation oils: UVM-3, UVM-4, UVM-5, UVM-5М, UVM-6,  UVM 10-10, UVM 10-10В, UVM 10-10Л, UVM 10-10М, UVM-12Б, UVM-12Б1, UVM-12Б2, UVM-12Б3, UVM-14Б У1, UVM-14Б1, UVM-14Б2, UVM-10-3, UVM-10-3Е, UDV-2М, PDV-Е and other range.
  • units for purification, drying and removal of solids from transformer and turbine oils – MCU-2-U1, MCU-4-U1, MCU-4С-U1,  MCU-4А,  MCU-4СА,  MCU-4C, MCU-4CF, MCU-4CS,  MCU-4CSA, MCU-А, MCU-С, MCU 4Р-N, MCU 4Р-NС, MCU 4Р-NA, MCU 4Р-NСА,  BC-N, MCU-7, FSM-2, FSMB-110М etc;
  • Sorbent regeneration systems– BR, PS-1, PS-1А,  PS-1Е, BRPS, MCU-4Р-BR, zeolite drying cabinet
  • Systems and vacuum sections for drying of solid insulation of power transformers – “Iney-4″, ” Iney-4М”, ” Iney-5″, ” Iney 5М”, ” Iney-6″, ” Iney-4.1″, ” Iney-4.1М”, ” Iney-4.2″, ” Iney-4.2М”, vacuum units BV-1 and BPR;
  • Units for drying of air to dew point below -50°С – “Sukhovey”, ” Sukhovey-4″, ” Sukhovey-5″, ” Sukhovey-4Е” with two independent heaters
  • transformer and transformer oil heating units: NTML, NTML-160М, NTML-80М, NTML-120М, NTML-200М, NTML-240М, NTML-150Е, for parameters of processed oil: solid content no more than 5 (10) ppm, filtration from 5 to 20 micron
  • oil filtration systems – FUM-P, FUM-А, customized drying and solid removal systems for mineral oils up to 50 m3/hour capacity, purity class from 7 toо 11, filtration ratios from 20 to 2000, filtration fineness 1, 3, 5, 10, 20 and 40 micron;

The full range of GlobeCore products is presented in the attached file, and can also be seen in the company’s website at www.globecore.com

The company has a global dealership network, and the products are supplied to more than 80 countries. Certified explosion protection option is available. Production certified as per ISO 9001 – 2000.