Definition of electrode line and characteristics of bipolar and monopolar systems
An electrode line is utilized in a few excessive-voltage direct-cutting-edge (HVDC) electricity transmission structures, to attach the converter stations to remote floor electrodes. The floor electrode is separated from the converter station so that cutting-edge returning thru the floor electrode does now no longer reason corrosion of elements of the station Veteran Energy Rates in touch with the earth.
The connection to the floor calls for a mainly designed floor electrode. The electrode is typically positioned numerous tens of kilometers from the converter station as a way to keep away from viable issues or corrosion inside the converter station grounding machine. The electrode line may be implemented, relying upon the area of the electrode, as floor cables, as overhead lines, or as an aggregate of floor cable and overhead line.
In bipolar transmission, a couple of conductors are used, every at an excessive capacity with appreciation to the floor, in contrary polarity. Since those conductors ought to be insulated for the total voltage, the transmission line fee is better than a monopole with a go-back conductor. However, there are some blessings to bipolar transmission that can make it an appealing option. This reduces earth go back loss and environmental outcomes. When a fault develops in a line, with earth go back electrodes mounted at every cease of the line. About 1/2 of the rated electricity can retain to go with the drift the use of the earth as a go back direction, running in a monopolar mode. Since for a given overall electricity score, every conductor of a bipolar line contains the handiest 1/2 of the cutting-edge monopolar lines, the fee of the second conductor is decreased in comparison to a monopolar line of the identical score. In very negative terrain, the second conductor can be carried on an unbiased set of transmission towers, so that a few electricity might also additionally remain transmitted even though one line is damaged. A bipolar machine can also be mounted with a metal earth go-back conductor.
In a monopole configuration, one of the terminals of the rectifier is attached to the earth floor. The different terminal, at an excessive voltage relative to the floor, is attached to a transmission line. The earthed terminal can be related to the corresponding connection on the inverting station via a conductor. If no metal go-back conductor is mounted, cutting-edge flow withinside the earth (or water) among electrodes. This association is a sort of single-twine earth go-back machine. The electrodes are typically positioned a few tens of kilometers from the stations and are related to the stations through a medium-voltage electrode line. The layout of the electrodes themselves relies upon whether or not they’re positioned on the land, at the shore, or at sea. For the monopolar configuration with earth go back, the earth cutting-edge go with the drift is unidirectional, and because of this, the layout of one of the electrodes (the cathode) may be particularly simple, even though the layout of the anode electrode is pretty complex. For lengthy-distance transmission, earth go back may be appreciably inexpensive than options the use of a committed impartial conductor, however, it could cause issues consisting of Electrochemical corrosion of lengthy buried metallic gadgets consisting of pipelines.
Underwater earth-go back electrodes in seawater might also additionally produce chlorine or in any other case affect water chemistry. An unbalanced cutting-edge direction might also additionally bring about an internet magnetic field, that can affect magnetic navigational compasses for ships passing over an underwater cable. These outcomes may be removed with the setup of a metal go-back conductor among the ends of the monopolar transmission line.