Liquid Dielectrics

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Liquid Dielectrics


liquids whose specific electric resistivity is more than 1010 ohms-cm. In an electrical field, both liquid and solid dielectrics are characterized by their polarization and dielectric losses; in strong fields, breakdown occurs. The electrical conductivity of liquid dielectrics is brought about by the ions formed as a result of the dissociation of the intrinsic and extrinsic molecules of the liquid. The breakdown of a liquid dielectric in a strong electric field is associated primarily with impurities contained in the liquid.

Liquid dielectrics are of great importance in electrical engineering and laboratory practice. They have a higher electric strength, dielectric constant ε, and thermal conductivity than air or other gases at pressures close to atmospheric pressure. Therefore, the permissible operational voltage of electrical devices is increased if the air is removed from fibrous or other porous insulation and the resulting voids are then filled with a liquid dielectric. An analogous effect may be achieved by potting with a liquid dielectric such parts as transformer casings, capacitors, or units of radio components or by impregnating with a liquid dielectric the paper insulation of capacitors and high-voltage power cables. Impregnation of the paper insulation of a capacitor with liquid dielectric results in a significant increase in capacitance.

Electrically insulating mineral (petroleum) oils are the most widely used type of liquid dielectrics. Their chemical composition is a mixture of various hydrocarbons, with ε ≈ 2.2–2.4 and a low dielectric loss angle δ (after a thorough cleaning and at normal temperature, tan δ < 0.001).

Chlorinated hydrocarbons with an asymmetric molecular structure (in the USSR, sovol and sovtol} are polar dielectrics with high values of ε (3–6), which exhibit a characteristic dependence of ε and tan δ on temperature and frequency. Synthetic liquid dielectrics (organosilicon and organic fluoride liquids) are also widely used.


Skanavi, G. I. Fizika dielektrikov (Oblast’ slabykh polei). Moscow-Leningrad, 1949.
Skanavi, G. I. Fizika dielektrikov (Oblast’sil’nykh polei). Moscow, 1958.
Brown, W. F. Dielektriki. Moscow, 1961. (Translated from English.)
Balygin, I. E. Elektricheskaia prochnost’ zhidkikh dielektrikov. Moscow-Leningrad, 1964.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
The mass fraction of nanoparticles in base fluids shows high thermal conductivity, but it is not beneficial to the insulation properties of liquid dielectrics. Thus, the insulating nanomaterials can ensure or even improve the insulation performance of liquid dielectric, and nanoparticles with high surface area, such as two-dimensional materials, are good choices for thermal fluids.
The heating and cooling responses can more intuitively illustrate the heat transfer efficiency of liquid dielectrics. Figure 14 shows the thermal responses of vegetable oil and nano-oil under DC and AC electric fields for cycling up to 80[degrees]C for three times, and the infrared thermal images are shown in Figure 15 at first heating and cooling responses.
A moisture meter with distributed type MT in the form of SICR makes it possible to measure the moisture content of emulsions based on nonpolar liquid dielectrics with lower limit of 10 [cm.sup.3]/[m.sup.3] without preliminary calibration operations.
Using dielcometry for the calculated determination of the volume moisture content W of emulsions is based on the dependence of the dielectric constant [[epsilon].sub.eml] of a homogeneous emulsion of the <<liquid nonpolar dielectric-water>> type on the moisture content and permittivity e[[epsilon].sub.nld]u of an anhydrous nonpolar liquid dielectric. Moreover, this dependence can be obtained both experimentally (by the method of preliminary calibration of moisture meters using <<reference>> emulsions) and analytically, in the form of a functional connection, the values of the volume moisture content W and the dielectric permittivities [[epsilon].sub.eml] and [[epsilon].sub.nld].
The presented laboratory experimental system allows for assessing the mechanisms of electrical discharge propagation in liquid dielectrics under high voltage lightning impulse.
(1) Liquid Dielectrics Lab, Department of Electrical and Electronics Engineering, National Engineering College, K.R.Nagar, 628 503, Kovilpatti, Tamilnadu, India.
N, "Measurement of complex permittivity of liquid dielectrics", Microwave and Optical Technology Letters, 34, (2002), 240-243,
Measuring the moisture content of the nonpolar liquid dielectrics is important for many practical applications, such as: electrical engineering, chemical industry, food industry, in the military and aviation equipment.
Monitoring of liquid dielectrics is achieved by examining various critical parameters like acidity, BDV, viscosity, volume resistivity, loss tangent and Dielectric constant.