Three-phase high voltage transmission

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The three-phase high-voltage transmission, mostly high-voltage three-phase transmission ( DHÜ or HDÜ ; English high voltage alternating current , HVAC ) is the most important method of transmitting electrical energy . As a rule, three-phase alternating current with a network frequency of 50 Hz, in some countries also 60 Hz, is used in the power grid for the transmission and distribution of electrical energy, and high-voltage direct current transmission networks (HVDC) are also used in some cases .

General

Overhead line for three-phase alternating current

In Germany, the highest voltage used for three-phase high-voltage transmission is 380 kV, in other countries voltages of up to 1200 kV are sometimes used. Depending on the physical conditions of the transmission network, the star point is treated differently in three-phase high-voltage transmission within the scope of earth fault compensation . For long transmissions at high voltage, the star point is usually rigidly grounded.

High-voltage transmissions are only economical up to a certain length or distance between the generator (power station) and the consumer; The reactive power requirement and the material costs of the transmission play an important role. High-voltage direct current (HVDC) transmission is generally a more economical method for large amounts of power to be transmitted and long line lengths or submarine cables with a high capacitive load . However, HVDC cannot yet be operated in the form of a network, it is only direct End point connections between two points possible.

For this purpose, networks with three-phase high-voltage transmission can be meshed more easily and interconnected networks such as the European interconnected system can be set up, since in addition to the parameter of the node voltages, the phase position and the associated parameters of active power and reactive power are also available independently of it. With the help of phase shifts, power flows on specific lines in a meshed network can be set and controlled in AC voltage networks using special devices such as phase shift transformers or the unified power flow controller. A distinction is made between the so-called longitudinal and lateral control. The mathematical basics and methods of load flow control in interconnected networks operated with AC voltage were developed by Edith Clarke at the beginning of the 20th century .

history

The supply of electrical energy required the use of electrical generators from the start , which for physical reasons can only generate alternating voltage. Initial attempts to produce direct current from it and thus to operate the power grid failed (see current war ). The outstanding advantages of the robust three-phase asynchronous machines over all other types of electric motors were quickly recognized and three-phase networks were introduced across the board. Despite certain disadvantages, this is still state of the art.

The first transmission of high voltage by means of three-phase current was carried out in 1891 on the occasion of the international electricity exhibition under Michail Doliwo-Dobrowolski . The 175 km long three-phase transmission Lauffen – Frankfurt transmitted three-phase current with a voltage of 15 to 25 kV.

In 1912 the first three-phase high-voltage transmission with 110 kV took place between Lauchhammer and Riesa. On April 17, 1929, when the north-south line of the RWE went into operation, the first three-phase high-voltage transmission with 220 kV took place. Some of the masts of the north-south line were designed to accommodate electrical circuits for 380 kV.

However, the first three-phase high-voltage transmission with 380 kV between Ludwigsburg-Hoheneck and Rommerskirchen did not go into operation in Germany until October 5, 1957 . In 1967 Hydro-Québec in Canada carried out the first three-phase high-voltage transmission with 765 kV and in 1982 in the Soviet Union with 1200 kV.

Other methods of transferring electrical energy:

Networks

A distinction is made between the following networks in electrical energy supply:

literature

  • Adolf J. Schwab: Electrical energy systems - generation, transport, transmission and distribution of electrical energy . Springer Verlag, 2006, ISBN 3-540-29664-6 .