How to Make High Voltage DC Power Transmission?

In 1870, the first direct current (DC) was developed by Thomas Alva Edison. We know that electricity is a flow of electrons. If electrons flow inversely (if starts from the battery ‘’+’’ terminal to the load and back to the battery ‘’- ‘’ terminal) which called DC or direct current. However, there are two main types of transmission systems AC transmission systems and DC transmission systems. However, in this journey, we will try to learn about when DC transmission is required, how to make high voltage DC power transmission, why DC transmission is required, and others.

What is High Voltage DC Power Transmission (HVDC)?

HVDC stands for high voltage direct current. If High voltage DC (50KV, 100KV, 300KV or more) is transferred over a long distance (2000 Km, 3000 Km, 5000 Km or more) through overhead or submarine cable to meet the load demand. This power transmission system is called high voltage DC power transmission system. Many large countries (USA, Russia, Canada, China, India) use the HVDC power transmission process to send power over a very long distance to minimize power losses and economic considerations.

How to Make High Voltage DC Power Transmission?

To transmit the power in a very long distance some losses and drawbacks appeared. For this reason, a high-voltage DC (HVDC) transmission system is used. In that case, some common improvements can be followed, such as efficiency, stability, low power losses, high transmission capacity, and others. However, let’s try to figure out how to make high-voltage DC power transmission, how to transmit it, and how does HVDC transmission system works. In this stage, we have referred to some crucial steps to make it clear perfectly.  

1. Power Generating Station

We know that our entire power network is an AC (alternating current) system. That’s why AC power is generated in the power station. It is noted that for a long-distance DC transmission, high-voltage DC power cannot be generated in the electrical power plant due to commutation problems. AC power is generated and sent to the nearer electrical substation or generation substation to convert AC power into DC power to transmit over a long distance.  

2. Converting Stations or Rectification Station

A converting substation or converting station is used to convert the power from AC to DC or DC to AC. To convert high voltage AC power into high voltage DC power. In that case, rectifiers, converters, harmonic filters, and synchronous condensers can be used. Let’s see an example, suppose in a three-phase three-wire system a 400KV output power is obtained from the output of the transformer.

This power is converted into a 2-wire 400KV HVDC with the help of a rectifier, converter, or synchronous condenser. And sent to the destination through a 2-wire HVDC transmission system. It is noted that the converting substation is only used to convert AC to DC, it is not the right one. This type of station can be used to convert DC to AC power.

3. DC Transmission Line

High-voltage DC transmission lines can be run in two main ways: overhead DC transmission and underground DC transmission. Indeed, most HVDC transmission lines are connected to bipolar converters. For this reason, the HVDC transmission line has two terminal conductors: a positive terminal and a negative terminal.

This two-wire HVDC transmission system runs over a long distance in another converting station. Whereas this HVDC power needs to be converted into AC power for use. Because our entire electrical network system is AC system.

4. DC to AC Inversion station

Indeed, both converter and inverter or inversion stations work for the conversion and inversion of electric power. In short, a conversion or inversion station has a rectifier and inverter. Whenever HVDC power comes to the inversion or inverting station invert DC power into AC power using an inverter.

It is noted that the inverter has some controlling and switching electronic devices, such as Thyristor, IGBT, and other semiconductor devices. This high-voltage AC power is transferred to the grid system and transmitted to the different substations through the transmission line.  

5. HVDC Transformers

HVDC transformer converting transformer is a type of transformer. It plays an essential role in the converting station. HVDC transformer is different from some other commercial transformer. There are three main configurations of a converting transformer, such as

  • Three-phase 2 winding system.
  • Single phase 2 winding system.
  • Single 3 winding system.

Transformers provide isolation and impedance matching between the converter equipment and the grid. High-voltage DC transformers are also used in the converter stations to match the voltage levels between the AC grid system and the HVDC transmission system.

HVDC Configuration System

HVDC configuration system refers to AC power generation and conversion into HVDC. This power is inverted into HVAC systems for commercial or residential use. Indeed, there are three main types of HVDC configuration, such as

  • Mono polar link
  • Bipolar link
  • Homopolar link

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