Chemical Laboratory

Oil tests and DGA (Dissolved Gas Analysis) are carried out in ELTAS oil laboratory as a quality control of process determination of faults in transformers, condition monitorin of transformers in service, incoming quality control of oil that is used for transformers.

The test devices and measuring methods are being used; comply with national and international norms such as IEC, ISO, ASTM, VDE, BS, JIS, TSE and TEİAŞ. Test results are annotationed in accordance with international standarts by our team who are experts in their field.

The tests are being performed using the state of art devices in our lab;


The thermic, electrical and mechanical faults in transformers causes the insulation oil of transformer to be polluted, breakdown, aged and lost its properties. This oil makes the electrical insulation weak by damaging the material that is in touch and not working properly. Insulation oil must be checked regularly after transportation, storage and during in service. Oil tests must be done periodically especially when the transformer is in service. A series of test must be done of researching properties and determining the breakdown level of the oil. The following tests are carried out by ELTAS oil technician;

  • Breakdown Voltage
  • Interfacial Tension
  • Power Factor
  • Acitidy
  • Water Content
  • Density
  • Viscosity
  • Color
  • Aniline Point

Breakdown Voltage: The breakdown point is defined as breakdown voltage for the insulation oil that is between two energized electrodes under certain circumstances. It gives information about insulation class of oil. Water content, amount and type of particles affect on that measurement. (IEC 60156, VDE 0370)

Interfacial Tension: The force necessary to detach a planar ring of platinum wire from the surface of the liquid of higher surface tension, that is, upward from the water-oil interface. For the decrement of interfacial tension that transformer in service, shows dirtiness, deterioration and ageing of oil. (ASTM D 971)

Power Factor: Dielectric dissipation factor, DDF, (tan δ ) of an insulating material is the tangent of the loss angle. The loss angle is the angle by which the phase difference between applied voltage and the resulting current deviates from π/2 rad when the dielectric of the capacitor consists exclusively of the insulating material. A high value of tan δ shows dirtiness, oxidation of oil and if there is a chemical content occures in oil precisely.

Acitidy: Measurement of all acid content matter in oil is defined acitidy. Higher result of acidity means that dirtiness and ageing occurs in oil via paint, varnish and other different materials. Acidic material not only causes deterioration of oil insulation, corrosion of metal parts and damage the cellulosical parts of transformer earlier but also causes heat transfer improperly.

Water Content: Water consantration of oil must be in the lowest level. It affects directly insulation system and dielectric breakdown. It detoriates of oil power factor via stable compound with oxidation and other pollutional materials. (IEC 60814)

Density: A substance is its mass per unit volume of oil under certain temperature is defined density. The low density oil, which is lower than water and ice, must be used in cold climate area. Otherwise water and ice particles occur in oil therefore electrical discharges may happen, specially in live parts of transformer. (ISO 12185)

Viscosity: Liquids resistance to gradual deformation by shear stress or tensile stress is defined viscosity. It affects directly cooling system of transformer. Oil that has a low viscosity provides better cooling. When the temperature decreases, viscosity of oil increases so that oil circulation is getting slower and cooling is done improperly. Because of that, Low viscosity oil must be used in cold climate area. When the oil getting aged, viscosity value increases due to increment of oxidation matter. (ASTM D 445)

Color and Appearance: This test does not show us the Kema of new oil. If the oil color of a transformer in service is getting dark it shows dirtiness or/and deterioration of oil. Appearance of oil must be clean and clear. Increment of water content of oil causes cloudy appearance. If the oil of transformer in service has cloudy appearance, but breakdown voltage is normal, the reason of cloudy appearance is sludges that caused by oxidation matter. (IEC 60422)

Aniline Point: Gives information about resolvent of oil and aromotic compounds of oil. Low levels, indicates aromatic compounds higher and resolvement is even higher. (ASTM D 611)

During overheating and discharging at component of transformer and electric equipments, some gases are being produced and starts to dissolving in oil. With analysis of qualitative and quantative of the dissolved gases, important informations can be obtained such as type of fault, rating and it’s location. Fault and events that are really at small scale and only just at starting phase and growing slowly and stealthy can be only exposed by gas analysis. Making gas analysis without cutting the power of transformer, makes this method superior. Before dismounting of the transformer, growing faults and events are determined earlier. With this, necessary preventions are being taken and fault is localized, so the bigger damages are prevented earlier.
Summary, the blood analysis of a sick person and gas analysis to expose the fault have the same importance. Because of this purpose, in our oil lab , following gas analysis can be done;

  • Hydrogen - (H2)
  • Methane - (CH4)
  • Ethane - (C2H6)
  • Ethylene - (C2H4)
  • Acetylene - (C2H2)
  • Carbonmonoxide - (CO)
  • Carbon dioxide - (CO2)
  • Oxygen - (O2)
  • Nitrogen - (N2)

Every fault type producing typical gases.

  1. By using mathematical ratio methods, important informations about type, volume and location of potential fault or faults can be obtained.
  2. Electrical faults (discharge and partial discharges)
  3. Thermic faults (extreme overheatings, hot-spots)
  4. Deterioration of oil (overheating or ageing process)
  5. Deterioration of cellulose (overheating or ageing process)
  6. Disconformity between oil - paint, metal and other materials
  7. Researchable other gas occurence sources


For insulation purpose, heat transfering and giving information, three typical insulation liquid are being used in component of transformer, reactor, regulator, capacitor, electrical cable, power switchgear and other electrical equipments:

  • Mineral oils (Petrol origined)
  • Natural based oils (Natural Esters)
  • Synthetic liquids (Synthetic Esters, Silicones ext.)


  • Insulation
  • Cooling
  • Giving information
  • Arc-suppression
  • Protecting material


  1. A good insulation (Insulation)
  2. A good cooling (heat transfer)
  3. A good stability (determination, durability)
  4. Adaptation with construction material
  5. Harmlessness for human and environment health and not make fire
  6. Suitable price