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.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
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.
Big Data and IIoT value; Monitoring Big Data; Robotics safety standards and programming; Learning about PID
Motor specification guidelines; Understanding multivariable control; Improving a safety instrumented system; 2017 Engineers' Choice Award Winners
Selecting the best controller from several viewpoints; System integrator advice for the IIoT; TSN and real-time Ethernet; Questions to ask when selecting a VFD; Action items for an aging PLC/DCS
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.
Motion control advances and solutions can help with machine control, automated control on assembly lines, integration of robotics and automation, and machine safety.
This article collection contains several articles on the Industrial Internet of Things (IIoT) and how it is transforming manufacturing.

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

Future of oil and gas projects; Reservoir models; The importance of SCADA to oil and gas
Big Data and bigger solutions; Tablet technologies; SCADA developments
SCADA at the junction, Managing risk through maintenance, Moving at the speed of data
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
click me