What Is a DC Block?

It is mainly composed of converter stations (rectifier stations and inverter stations), DC lines, AC-side and DC-side power filters, reactive power compensation devices, converter transformers, DC reactors and protection and control devices (see DC The basic components of a power transmission system). The converter station is the core of the DC transmission system, which completes the conversion between AC and DC.

DC transmission

[Word]: DC transmission

[Zhuyin]: zhí liú sh diàn

[English abbreviation]: DC

[Definition]: Will be issued by the power plant

Compared with AC transmission, DC transmission has the following advantages:

When the same power is transmitted, the cost of the DC line is low,

The development of DC transmission is also limited by some factors. First, the DC transmission

Transmission of electrical energy by direct current. People's application and understanding of electrical energy first began with DC. French physicist and electrical technician M. Deppler to install 3 horsepower in Miesbach coal mine in 1882

In the 1930s and 1950s, people explored the use of various devices to construct

DC transmission is mainly used in 5 aspects:

Long-distance high-power transmission;

Contacting different frequencies or the same frequency instead of running synchronously

On February 21, 2014, a domestically produced DC submarine cable with the highest single-voltage level and the longest length was laid into the sea in Zhoushan, marking the world's first five-terminal flexible DC power transmission demonstration project to enter a later stage of tackling.

Settled in Zhoushan, the world's first five-terminal flexible DC transmission demonstration project, using ± 200 kV DC voltage, constructing a converter station in Dinghai, Laoshan, Laoshan, Yangshan, and Sijiao, and constructing an AC 220 kV transmission line 21.8 Kilometers, AC 110 kV transmission lines 9.99 kilometers; construction of 141 kilometers of DC cable transmission lines. After the project is completed, it will greatly improve the stability of the island's power grid, provide strong energy protection for the spanning development of the archipelago's new area, and provide a model for new energy access and island development nationwide and worldwide.

It is reported that the entire flexible DC project is planned to complete submarine cable construction in April 2014; system live debugging and testing will be carried out in May; and five stations will be fully completed and put into operation in June. ^[2]

On July 4, 2014, after the successful completion of 168 hours of trial operation, the world's first five-terminal flexible DC power transmission projectZhoushan, Zhejiang ± 200 kV five-terminal flexible DC project was officially put into operation, marking the country's standing on the world's flexibility Commanding heights in the field of DC transmission. ^[3]

A few days ago, the world's first five-terminal flexible HVDC transmission project, the Zhoushan Five-terminal Flexible HVDC Transmission Demonstration Project in Zhejiang, began a comprehensive 90-day overhaul. This is the first comprehensive "physical examination" of the project in one year. ^[4]

On November 11, 2015, the Xiamen Xiamen Flexible DC Transmission and Transformation Project successfully completed the no-load step-up test on a unipolar line, marking the success of the world's first ± 320 kV flexible DC cable withstand rated voltage test. ^[5]

On December 17, 2015, Xiamen's ± 320 kV flexible DC transmission technology demonstration project, the world's highest voltage class and largest transmission capacity flexible DC project, was officially put into operation. ^[6]