Article on U.S. power grid stability. 1

I found this article quite interesting. I hope this link works for everyone.

http://scitation.aip.org/content/ai...+11-15+August+&dm_i=1Y69,2Q68J,E1NQZ8,9XSG6,1

The article states that as transmission lines get longer the capacity goes down. Is this due just to resistance losses, just as for extension cords?

 

[FPelec]

HV and EHV ac transmission lines are generally not limited by joule losses: angular stability and voltage drops are generally the costraints dictating the maximum loading.

http://www.nerc.com/docs/pc/spctf/Application_of_Line_Loadability_IEEE.pdf

Si duri puer ingeni videtur,
preconem facias vel architectum.

 

[cranky108]

We've all known in the industry that power production close to the load is more stable then having power production far away. However NIBY (not in my back yard) has the population convenced that it is better to have power production out of sight, or where it make a great fishing spot. This is the way the North East is arranged where the power production is not close to the load.

There are also problems in over populated areas of trash and other waste removal. Well guess what, it's a problem created by people, and it tskes people to fix it, and the population isen't willing to accept the solutions being offered. Those people selling the latest and greatest solar panels, and wind farms aren't selling energy stability, and the population believes that is what is being offered.

Don't hold your breath on smart grid solutions either yet. They will help some, but I doubt they will fix every thing.

Notice that the US dosen't have an energy policy, it has a global warming policy, and without leadership, or vision we are destined to float on the sea of political fluactions.

 

[racookpe1978]

And do the best we can every day - until it really does fail.

 

[PHovnanian]

Time for another beer analogy.

Think of an AC transmission line like a flexible drive shaft, driving a gear with rubber teeth. The more power (torque) you put on that shaft, the more it twists. Likewise, for the same load, the longer shaft will twist more. The rubber teeth are: When the twist reaches a certain angular offset, they will bend and begin to slip by each other.

Power systems also have an inertia, much like rotating mechanical systems. A system that is operating steady state and then perturbed will oscillate about its new operating point. If that system was already running near its limits (the rubber teeth are about to slip) and then perturbed, the resulting transient can push it over this limit and cause it to slip out of sync. A power system running out of sync does not transmit (continuous) power. The power flows back and forth uselessly and can cause actual mechanical torque and damage in generators, motors, etc. were it not for protection equipment (breakers) opening circuits. Which in turn produce their own perturbations. And on, and on.

There. And not even a mention about beer.

 

[squeeky]

Long Power lines also suffer from capacitance as the voltage to ground are the cap plates and the air is the dielectric. There is a charging and discharging effect. The extension cord theory still holds. In Africa we are running more and more DC power lines on long distances. These are up to 500 000v positive to ground one and 500 000v negitive to ground thus giving 1 000 000v. No inductance losses only resistance. Tat this voltage the current is reletively low. They are now talking about running power from the DRC, through Namibia to South Africa as the Congo river has such huge potenital but no real industry to utilize it.

 

[cranky108]

Not that I am oposed to DC transmission, however years ago I heard a story about the negitive of a DC power line would collect ash from residents burning of trees along transmission path.

This is not to say that AC power lines are immune from collecting contamination (sea salt, and Mag cloride), but is ash also a factor with DC lines?

 

[davidbeach]

Was at the southern end of the Pacific DC Intertie several years ago. Half the yard and equipment was shiny and pristinely clean while the other half was absolutely filthy.

 

[prc]

Today UHV DC lines are there with +-800 kV to transmit 7000 MW over 2000 kms and +-1100 kV to trasmit 10000 MW over 3000 kms.China already have couple of lines at 800 kV DC and India is putting up its first 800 kV DC line to evacuate hydro power from north east of the country to Agra,near capital. This 1650km line has a tie in line said to be first time in the world. With the development of HV DC Circuit breakers( announced by ABB in 2012) UHV DC lines may come more and more in Asia, Africa and South America.ABB announced development of 525 KV DC cable that can transmit 2600 MW over 1000 kms with less than 5 % loss to evacuate renewable energy from off shore parks.Couple of 1100 KV UHV AC lines are working in China while India is planning for 1200 kV AC lines to link power intensive corridors.