DC electrical transmission growing

07/30/2010


Dear Control Engineering: It seems that using dc for electrical distribution is growing. How is this practical?

You shouldn’t expect to have your residential electrical service converted to dc anytime soon. The considerations that made utilities adopt ac almost universally over the last century continue to apply for most uses. Still, there are applications where high voltage dc is being used to great advantage. If you have to move a large amount of electric energy from point A to point B, dc may be the better choice. However, for more typical grid distribution applications, ac still does the job.

For example, ABB just completed a project in China that has pushed out the boundaries. There’s an area in southwest China near Xiangjiaba where there are hydroelectric generating units that put out a lot of power. The problem is that the power is needed in Shanghai which is about 2,000 km (1,200 mi.) away.

Ultra-high voltages require exotic switchgear.This new power line (note that the term is singular) carries 7,200 MW over that distance at 800 kV. ABB says it’s very efficient with less than 7% line loss over that distance. Once the juice gets to Shanghai, it is converted into ac for more traditional local distribution.

(You may remember that in our post last week, we discussed definitions of medium- and high-voltage. Once you’re around 800 kV, you’re definitely in the ultra-high cagegory.)

ABB has been doing a lot of research in this area and has developed the transformers, converters, and switchgear to handle these extreme levels. Earlier efforts in service include 500 and 600 kV systems, but raising the voltage increases efficiency.

Such deployments will likely become more common for applications where generating capacity is removed from consumers, such as hydroelectric and wind generation. It can even help make it more practical to locate coal-fired plants at the minehead, rather than moving coal from a mine to distant plants via rail.

--Peter Welander, pwelander@cfemedia.com 
Control Engineering



No comments
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Additive manufacturing benefits; HMI and sensor tips; System integrator advice; Innovations from the industry
Robotic safety, collaboration, standards; DCS migration tips; IT/OT convergence; 2017 Control Engineering Salary and Career Survey
Integrated mobility; Artificial intelligence; Predictive motion control; Sensors and control system inputs; Asset Management; Cybersecurity
Featured articles highlight technologies that enable the Industrial Internet of Things, IIoT-related products and strategies to get data more easily to the user.
This article collection contains several articles on how automation and controls are helping human-machine interface (HMI) hardware and software advance.
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Mobility as the means to offshore innovation; Preventing another Deepwater Horizon; ROVs as subsea robots; SCADA and the radio spectrum
Future of oil and gas projects; Reservoir models; The importance of SCADA to oil and gas
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
click me