The dielectric strength of transformer oil is expected to be

A liquid dielectric is a A good liquid dielectric should have high Liquid dielectrics are The electrical properties tend to be strongly influenced by dissolved gases (e.g. Some examples of dielectric liquids are Overview of common liquid dielectrics Name Dielectric constant Max. breakdown strength ( MV⁄ cm) Properties 1.0 Flammable. Common type of n- 1.1–1.3 Flammable. Used in some capacitors. n- Flammable. 4.7 High dielectric constant. Flammable. Refined and dried castor oil is used in some high voltage Hatcol 5005 synthetic ester 3.2 High dielectric constant. Fire Resistant. Biodegradable PCB replacement. Low temperature fluidity. 2.3–2.8 (-20) [ clarification needed] 1.0-1.2 More expensive than hydrocarbons. Less flammable. 1.75 >0.16 More expensive than hydrocarbons. Non flammable and non toxic. High °C. 1.8 >0.16 More expensive than hydrocarbons. Non flammable and non toxic. Low 7.4 >0.01 More expensive than hydrocarbons. Higher Dk compared to other perfluoroalkanes. Non flammable and non toxic. Low °C. Formerly used in transformers and capacitors. 78 :503 High thermal capacity, good cooling properties. Low electrical conductivity when free of ions. 2.28 :503 1.1 Toxic, flammable. 2.4 Cryogenic. Highly flammable with combustible materials. 1.43 :498 1.6-1.9 Cryogenic. Used as coolant with many low-temperature sensors and 1.0 Cryogenic. Flammable. 0.7 Cryogenic. Used with Liquid 1.10–1.42 Cryogenic. See also [ ] • References [ ] • ^ a b c d e f g h i Naidu, S.; Kamaraj...

In this paper, the dielectric characteristics of the power transformer oil are enhanced by dispersing newly synthesized nanoparticles. Two nanocrystalline powders, barium titanate (BaTiO 3) and nickel ferrite (NiFe 2O 4), are synthesized via the tartaric acid precursor method. The change in the crystal structure, crystalline size, and microstructure of the synthesized nanoparticles as a function of annealing temperatures are characterized using X-ray diffraction and transmission electron microscope. These nanoparticles are mixed with the transformer oil considering different concentrations such as 25, 50, and 75 mg/l where the sonicator is used to disperse the nanoparticles in the oil samples. The dielectric breakdown strength is tested based on IEC standard. The results confirm the efficiency of the NiFe 2O 4 than BaTiO 3 for enhancing the dielectric characteristics of the power transformer oils. • Katiyar A, Dhar P, Nandi T, SirishaMaganti L, Das SK (2016) Enhanced breakdown performance of Anatase and Rutile titania based nano-oils. IEEE Trans Dielectr Electr Insul 23(6):3494–3503 • Ibrahim ME, Abd-Elhady AM, Izzularab MA (2016) Effect of nanoparticles on transformer oil breakdown strength: experiment and theory. IET Sci Meas Technol 10(8):839–845 • Sima W, Shi J, Yang Q, Huang S, Cao X (2015) Effects of conductivity and permittivity of nanoparticle on transformer oil insulation performance: experiment and theory. IEEE Trans Dielectr Electr Insul 22(1):380–390 • Cavallin...

The final part of the basic oil quality assessment trio (along with Moisture & Acidity) is the Breakdown Voltage Strength otherwise known as the BDV. The BDV is an important factor in understanding the quality of the oil and is affected in many ways. Often there is a direct correlation between a high moisture content and a reduced breakdown voltage so the two should be viewed together to understand what is causing the reduced BDV. First let’s look at the test itself. The BDV is determined by using a piece of laboratory equipment which is specifically designed for the task, a BDV Tester. The testing is carried out in accordance with IEC 60156: Insulating liquids – Determination of breakdown voltage at power frequency – Test method. In short the test measures the dielectric strength of an oil sample by applying a steadily increasing voltage to the electrodes until breakdown of the oil occurs. The issues or points of note The BDV of an oil is inherently variable and is dependent on what aligns between the 2.5mm gap between the electrodes during that specific voltage application. The methodology tries to elevate the variation by carrying out the test six times and gives the average kV which is the one you see on your oil reports. The size of the test cell…well it’s large! The test cells usually require 350 – 400ml of oil to cover the electrodes and to perform the test on the oil. When the oil samples are typically 500ml sample bottles it doesn’t give much room for manoeuvre. T...