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However, if direct current is used, the cable capacitance is charged solely when the cable is first energized or if the voltage stage modifications; there is no such thing as a extra present required. HVDC is less reliable and has lower availability than alternating current (AC) programs, vaportry primarily attributable to the additional conversion equipment. The equipment was moved to the Soviet Union and was put into service there as the Moscow-Kashira HVDC system. Multilevel converters have the advantage that they permit harmonic filtering tools to be decreased or eliminated altogether.

A significant downside of HVDC systems using line-commutated converters is that the converters inherently devour reactive power. The development of upper rated insulated-gate bipolar transistors (IGBTs), gate flip-off thyristors (GTOs), and integrated gate-commutated thyristors (IGCTs), has made HVDC programs extra economical and dependable. When a fault develops in a line, with earth return electrodes installed at each end of the road, approximately half the rated power can proceed to stream using the earth as a return path, vapeamong (https://www.vapeamong.com/) operating in monopolar mode.

Even higher powers might be achieved by connecting two or more twelve-pulse converters in series in each pole, as is used in the ±800 kV Xiangjiaba-Shanghai mission in China, which uses two twelve-pulse converter bridges in each pole, every rated at four hundred kV DC and vapenever (resources) 1,600 MW.

Pulse-width modulation (PWM) is normally used to enhance the harmonic distortion of the converter. Voltage distortion is not a problem in its own proper, since customers do not connect directly to the DC terminals of the system, vapenever so the main design criterion for the DC filters is to make sure that the harmonic currents flowing within the DC strains don't induce interference in nearby open-wire telephone strains.

It is vitally costly to offer harmonic filters able to suppressing such harmonics, so a variant identified because the twelve-pulse bridge, consisting of two six-pulse bridges in series with a 30° part shift between them, is nearly all the time used. Converter transformers for LCC HVDC schemes are quite specialized due to the high levels of harmonic currents that circulate by them, vapingper and since the secondary winding insulation experiences a permanent DC voltage, which affects the design of the insulating structure contained in the tank.

The shunt capacitors are normally connected on to the grid voltage but in some instances could also be related to a decrease voltage via a tertiary winding on the converter transformer. This configuration ended in 2014 when poles 1 and a pair of once more have been rebuilt to work in bipole and pole three (LCC) works in bipole with a brand new pole 4 (VSC). Early LCC techniques used mercury-arc valves, which were rugged but required excessive upkeep.

Like mercury arc valves, vaperather thyristors require connection to an external AC circuit in HVDC functions to show them on and vapereason off. The final HVDC system to make use of mercury arc valves was the Inter-Island HVDC link between the North and South Islands of recent Zealand, which used them on one of its two poles.

Since then, all mercury arc methods have been either shut down or transformed to use strong-state units.