Classification of electrical materials

A material is an object with a certain composition, structure and properties, designed to perform certain functions. Materials can have different aggregate states: solid, liquid, gas or plasma.

The functions performed by materials are diverse: ensuring the flow of current (in conductive materials), maintaining a certain shape under mechanical loads (in structural materials), providing insulation (in dielectric materials), converting electrical energy into heat (in resistive materials). Usually, the material has several functions. For example, a dielectric necessarily experiences some kind of mechanical stress, that is, it is a structural material.

Materials science — a science dealing with the study of the composition, structure, properties of materials, the behavior of materials under various influences: thermal, electrical, magnetic, etc., as well as when these influences are combined.

Electrical materials — this is a branch of materials science that deals with materials for electrical engineering and energy, i.e.materials with specific properties necessary for the design, manufacture and operation of electrical equipment.

Materials play a crucial role in the energy sector. For example insulators for high voltage lines. Historically, the first to come out with porcelain insulators. The technology of their production is quite complex and capricious. Insulators are quite bulky and heavy. We learned to work with glass - glass insulators appeared. They are lighter, cheaper and somewhat easier to diagnose. Finally, recent inventions are silicone rubber insulators.

The first rubber insulators were not very successful. Over time, microcracks form on their surface, in which dirt accumulates, conductive traces are formed, after which the insulators break. A detailed study of the behavior of insulators in the electric field of conductors of high voltage lines (OHL) under conditions of external atmospheric influences made it possible to select a number of additives that improve resistance to atmospheric influences, resistance to pollution and the action of electrical discharges. As a result, a whole class of lightweight, durable insulators has now been created for various operating voltage levels.

For comparison, the weight of suspended insulators for 1150 kV overhead lines is comparable to the weight of the wires in the distance between the supports and amounts to several tons. This forces the installation of additional parallel strings of insulators, which increases the load on the support. It requires the use of more durable, which means more massive supports. This increases the consumption of materials, the large weight of the supports significantly increases the cost of installation.For reference, the cost of installation is up to 70% of the cost of building a power line. The example shows how one structural element affects the structure as a whole.

Thus, electric materials (ETM) are one of the determinants of the technical and economic performance of each power systems.

The main materials used in the energy industry can be divided into several classes - they are conductive materials, magnetic materials and dielectric materials. The common thing between them is that they work under conditions of voltage, and therefore in an electric field.

Materials for wires

Conductive materials are called materials whose main electrical property is electrical conductivity, which is highly pronounced compared to other electrical materials. Their use in technology is mainly due to this property, which determines the high specific electrical conductivity at normal temperature.

Both solids and liquids and, under the right conditions, gases can be used as conductors of electric current. The most important solid conducting materials practically used in electrical engineering are metals and their alloys.

Liquid conductors include molten metals and various electrolytes. However, for most metals, the melting point is high, and only mercury, which has a melting point of about minus 39 ° C, can be used as a liquid metal conductor at normal temperatures. Other metals are liquid conductors at elevated temperatures.

Gases and vapors, including metallic ones, are not conductors of low electric field strength.However, if the field strength exceeds a certain critical value that ensures the onset of shock and photoionization, then the gas can become a conductor with electronic and ionic conductivity. A highly ionized gas, with the number of electrons equal to the number of positive ions per unit volume, is a special conductive medium called plasma.

The most important properties of conductive materials for electrical engineering are their electrical and thermal conductivity, as well as the ability to generate thermal EMF.

Electrical conductivity characterizes the ability of a substance to conduct an electric current (see — Electrical conductivity of substances). The mechanism of current passage in metals is due to the movement of free electrons under the influence of an electric field.

Semiconductor materials

Semiconductor materials are those which are intermediate in their specific conductivity between conductive and dielectric materials and whose distinctive property is the extremely strong dependence of the specific conductivity on the concentration and type of impurities or other defects, as well as in most cases on external energy influences (temperature, brightness, etc.). NS.).

Semiconductors include a large group of electronically conductive substances whose resistivity at normal temperature is higher than that of conductors but lower than that of dielectrics and ranges from 10-4 to 1010 Ohm • cm. In energy, semiconductors are not used directly, but electronic components based on semiconductors are widely used. This is any electronics at stations, substations, dispatch offices, services, etc. Rectifiers, amplifiers, generators, converters.Semiconductors based on silicon carbide are also produced non-linear surge arresters in power lines (surge arresters).

Dielectric materials

Dielectric materials are called materials whose main electrical property is the ability to polarize and where the existence of an electrostatic field is possible. The real (technical) dielectric approaches the ideal, the lower its specific conductivity and the weaker the delayed polarization mechanisms related to the dissipation of electrical energy and the release of heat.

Dielectric polarization is called appearance in it when introduced into the external electric field a macroscopic internal electric field due to the displacement of charged particles that make up the dielectric molecules. The dielectric in which such a field has arisen is called polarized.

Magnetic materials

Magnetic materials are those designed to work in a magnetic field by direct interaction with that field. Magnetic materials are divided into weakly magnetic and strongly magnetic. Diamagnets and paramagnets are classified as weakly magnetic. Strong magnetic - ferromagnets, which in turn can be magnetically soft and magnetically hard.

Composite materials

Composite materials are materials composed of several components that perform different functions and there are interfaces between the components.