The history of the development of the main high-voltage equipment. Part 2

Since 1880, attempts to lay power cables designed for voltage up to 200 V. The preliminary long-term experience of operation of telegraph lines was the basis for the construction of the first high-current cables. As the gutta-percha insulation used and impregnated jute. In 1882 TA Edison developed a special cable design and cable gland for the network the first central electric power station in New York. In 1884 in Vienna was laid cable with a working voltage of 2 kV.

In the late 80's and early 90-ies in the cable technology took decisive changes due to commissioning of a new type of insulation material: impregnated paper instead of jute. Paper insulation has improved voltage power cables with 2 to 10 kV. To increase the mechanical strength and the tightness of power cables as well as communication cables, lead sheathed steel cover. In 1908 came the first three-core cables for voltage of 20 kV belted and viscous impregnation. This cable was laid in Baku (all present). In 1910, in Germany between Dessua and Bitterfeld was first laid solid conductors for voltage of 60 kV. Increased distribution of power high-voltage cables (voltage 35 kV) only began after the First World War.

Cable technology developed in close cooperation with the scientific research of the electric field. The development of the theory of electrical cable engaged Russian physicist PD Voynarovsky. In 1913 Hoch-shtedter (Germany) on the basis of theoretical developments proposed cable design with shielded cores. Screening of living allowed in 1918-1919. to begin production of three-core cables for voltages up to 60 kV. However, as the growth of electric distribution networks preferential widely cheaper overhead lines.

Insulation overhead power lines was initially entirely borrowed from the telegraph lines. Initially, these were pluggable, bell-shaped glass or porcelain insulators. At the turn of 80-90-ies require reinforced insulation: a special recess in the pin insulators filled with oil - so any oil porcelain insulators. Empirically it was determined their most rational structural shape - long and thin porcelain skirts of the "Delta" (Germany). This insulator could be used for voltages of 60-70 kV. But at the beginning of the XX century. in the construction of high-voltage runs on one of the first places again popped linear problem isolation. Lack of mechanical and electrical strength of the pin insulators limited bandwidth transmission. Favorable output found in 1906 Hewlett: he developed the design of suspension porcelain insulators, which made it possible to dramatically increase the voltage of power. In 1908-1912 gg. with suspension insulators were built first line to 110 kV voltage in the US, and later in Germany. Scope pin insulators are generally limited to 60 kV was lower.

Another difficulty in the way of the introduction of high stress arose in connection with the phenomenon of corona on high voltage wires. Corona was accompanied by a significant loss of energy. The first attempts to experimentally determine the energy loss at the crown have been taken by American researcher Charles Scott in 1898 in line with a voltage of 20 kV. Further theoretical and experimental research in the years 1910-1914. VF Mitkevich conducted in Russia ,. F. Peak in America, Mr. Kapp in England. The results of these studies have shown that reducing the loss of the crown may be increasing the actual ,, or "electric", the diameter of the wire. This conclusion formed the basis for widespread steel-aluminum and aluminum wires, since the conductivity equal to the diameter of the wire is greater than copper. The use of aluminum was first taken in the United States on the electrical installation of Niagara in the late 90-ies of the last century. By 1910, aluminum wire have been widely disseminated.

At the end of the first decade of the XX century. began to use copper wires with hemp basis - harbingers of hollow wires are also used to reduce losses in the quiet bit. The conclusion that the rationality of increasing the diameter of the wires led VF Mitkevich (1910) to the idea of ​​split-wire common in today's ultra-high voltage power transmission.

Simultaneously with the construction of the first electrical installations have a problem of struggle against overvoltage. The real danger is over-voltage, induced in the air near the wires when lightning discharges. Historically, the first means of protection against atmospheric electricity were tools borrowed from the practice of lightning protection of buildings and telegraph communication lines: grounded cables, lightning rods and equipped with fusible link wire lightning rods, is the prototype of fuses.

In the 90-years, there are many types of lightning protection devices based on different principles of action: water jet grounding, gradually reduces over-voltage electrostatic origin; arrester with spark gap and forced quenching the arc, the self-inductance of the coil, proposed by the British physicist O. Lodge as filters for lightning surge currents and others.

When designing the arresters most difficult task was to secure follow current extinction of the arc, the value of which has grown rapidly with the increase of electric power stations. Much ingenuity and unsuccessful attempts of scientists and engineers from different countries has been associated with the creation of fuses.

In 1891 J. Thomson proposed construction with multiple rupture of the arc - only in 20-30-ies of XX in principle, has found full recognition. while the use of current-limiting resistors in arrester with valve properties.

Since 1896 the most common type of lightning rod arrester becomes horny proposed by the German E. Olyplegerom electrician. By 1900, he won an almost complete monopoly in networks up to 10 kV. With many enhanced arcing horns this type of lightning protection for a long time to stay in the European networks with voltage up to 50-60 kV. America took a different path.

Since 1907 there have spread aluminum arresters that meet the requirements of voltage 100- 150 kV networks. Surge possessed flawless performance and reliability of action and was only a temporary protective measure (before the start of the 20s).

During the first two decades of the XX century. did not stop the search for other means of overvoltage protection, including the effectiveness of surveyed ground wire - rope shielding theory was put forward by the German scientist C. Petersen in 1914. Check the safety properties of high-voltage capacitors and inductors. In general, overvoltage protection remains an unresolved problem. Protection against direct lightning strikes was considered quite impossible. This was due to poor knowledge of lightning and overvoltage waves propagation processes-by-wire, and the rapid obsolescence of protective equipment, the development of which has not kept pace with the rapid growth of stress and electrical installations of capacities. The situation was aggravated by the fact that in powerful networks manifested switching overvoltage. protection and has taken the wrong way of combining in a single unit from the protection against atmospheric and internal surge.

Means of protection from overcurrents also passed a long way of development, before becoming a special branch - the relay protection. Protection against short-circuit currents initially was quite primitive. By the end of the 90s of XIX century. virtually the only means of protection of electrical equipment from excessively high currents are fuses. They were reliable devices used at voltages up to 6 kV. However, fuses can not ensure the selective disconnection of damaged parts of the network, and also cope with large current interruption in the power network, thereby limiting the increase in the power of electric installations.

To replace fuses came relay. Back in the 90's began to apply first the maximum circuit breakers, then the maximum electromagnetic relays, which set up certain current value. Exceeding the set current in case of accidents caused relay operation by switching off the damaged area.

Protection improved. In the early 900s has several switch types: current, voltage, power direction. But while the questions correctly matching the current, voltage and time delays have been little studied, and it was not given yet the desired value, there were frequent non-selective tripping.

In the first and the beginning of the second decade of the XX century. New born relaying areas: devices based on the use of non-linear elements of electric circuits, and especially saturated steels. So, in 1911 in the United States were used bystronasyschayuschiesya transformers, changing accordingly the relay response time.

Shukhardin S. "Technology in its historical development"