now here's a question, when converting voltages for DC transmission lines, do they step it up with a standard AC transformer before rectification or does the voltage get boosted on the DC side after the rectifier, or as part of the rectifier?
pretty much still need AC to make massive changes in voltage right?
there are losses on DC lines as well. P=i^2R regardless if it is AC or DC, but with DC you normally have less I because your V is higher.
stations have losses if they are stepping up/down AC voltage and if they are inverting/rectifying between AC and DC. I bet the losses are less in an pure AC facility than a DC/AC
so anything long distance and high voltage is DC. that is plain wrong, there are 735 kV AC transmission lines and AC transmission lines span the country.
and hydroquebec's 735kV lines also get affected by solar storms leading to grid instability and are the reason no other grids are connected to it except by DC. Hydroquebec had done a lot of interesting things though, they have named all their assets (lines, switches, etc) random strings so there is no confusion as to exactly which you are referring to. people can't memorize circuits and line numbers by pattern and then accidentally refer to the wrong one.
However, it wasn’t until the HydroQuebec Power Grid blackout in Quebec, Canada, in March of 1989 that the world truly realized the extent to which solar storms can impact the economy. The solar storm induced a nine-hour blackout which affected 6 million customers and ultimately cost this power company more than $10 million — putting the cost of this disaster in the same category as hurricanes and earthquakes (and this does not include the estimated cost to its customers, which was in the tens — if not hundreds — of millions of dollars) (Windows to the Universe Team, 2000). Additionally, Public Service Electric and Gas in New Jersey suffered serious damage to two of its transformers. It cost PSE&G eight million to replace the transformers and the cost of replacement energy during the time the transformers were taken out of service was approximately $16.8 million, so the net cost for PSE&G was over $24 million. Together, this single space weather storm cost Hydro Quebec and PSE&G more than $30 million. Comprehensive real-time protective space weather prediction services could have significantly reduced damages and costs. Hydro-Quebec’s solution to the blackout was to install devices that block solar storms created geomagnetically-induced currents from traveling through its transmission lines. Unfortunately, this solution is extremely complex and expensive ($1.2 billion) (Quinn, 2000).
It was soon realized that the key to protecting vulnerable high tech systems is the ability to forecast solar storms and to take appropriate measures to avoid (or at least minimize) potential damage before they strike the Earth.
Thanks to data from new sensors and improved forecast models, NOAA’s SEC forecasters were able to alert electric power customers 40 minutes before a solar storm hit the Earth on May 2, 1998. In response, electric power utilities were able to successfully divert power and increase safety margins on certain parts of the grid to avoid stress on the power system.
Researchers have found that local electricity prices in the northeast increase in response to the regionalized effects of solar storms. Specifically, in research supported by the National Science Foundation, Forbes and St. Cyr (2004) note that space weather disrupts the system that transmits the power from where it is generated to where it is distributed to customers. In examining the determinants of the real-time electricity price in the market over the period June 1, 2000, through Dec. 31, 2001, they concluded that solar storms (over this period) increased the wholesale price of electricity by approximately 3.7 percent or approximately $500 million over the 19 month sample period.
welcome to the real world, where building the perfect system costs more than it is worth and there are physical limitations to what is possible!
What % change would you expect the system to be able to handle? Generators are physical spinning machines with inertia, and the mechanical source turning them can also have inertia. You can't stop them on a dime, that power has to go somewhere.
Take one of the 17 generators at the hoover dam. 2GW total capacity there, maybe 111 MW per machine. Power = head x flow x 9.81 111 MW = 221m x flow x 9.81 you have 51,000 litres per second of water moving through the turbine.
That water is going through the turbine at 85mph and can't be stopped instantly if there is a sudden huge drop in demand.
When the electrical load on a generator drops suddenly and the mechanical power in doesn't change, the machine accelerates. If it accelerates indefinitely it flies to pieces, so yeah, they shut them down if they accelerate past a certain speed.
I know electricity seems like an on/off perfect thing where you can plug in whatever you want where ever you want and it just works, but that is only because what you are plugging in is insignificantly small compared to what is powering it.
I think american super conductor did the superconductor grid in new york city. it has definitely been done before and is a proven technology.
P(three phase)=root(3)*I*V(phase to phase) cos theta
for a 500 kV AC transmission line, with power factor.8 5x10^9=root(3) I (500x10^3) 0.8
I = 7216 Amps per phase.
I don't think they make cables big enough to carry 7000 amps.
Say you can get 1000 amps on a cable. you are going to need 7 500 kv circuits. with 2 circuits per tower you are going to need 3.5 500kV transmission lines and all the shit on either end to handle 7 different circuits.
so 1 DC superconducting circuit might in fact be cheaper, especially over such a short distance.
Looks like I was wrong on that one. It is funny reading my post now, I state that they definitely have to take cash by law but I really have/had no idea and was talking out my ass.
one advantage of all this openness is that people can come up with new and unexpected uses for devices. Maybe the board has a mini-pci slot on it and they want to swap in a mini-pci card that does something totally different.
People have added memory to their linksys WRTs... I'm trying to say when the software is open, the hardware can be modified and extended too.
he reason for keeping drivers closed isn't about revealing inner workings of your chip
one reason is that an open source driver could allow the user to use a frequency not allowed by the spectrum governing body where they live. The ISM bands are not exactly the same everywhere.
Broadcom may not be able to sell a radio that can transmit outside of the ISM in north america with an open source driver because it would then require a license from the FCC.
indeed, it appears that even with openwrt you are stuck with kernel 2.4: https://forum.openwrt.org/viewtopic.php?id=22016 The thing I understand for many of the targets that are Broadcom is that their drivers are impossible to get. You only get the binaries for the driver and they only work in 2.4.
So, if they did not release the source for the Broadcom drivers, you can't easily port it, unless you use b43 which is the reverse-engineered drivers.
* WPA and WPA2 are not working. * SAMBA support is not present. * NAS can be accessed only through command line using utilities such as ftp * and No GUI support to access NAS is available till now. The patches and the script in this release are based on
I mean, no WPA? stuck with WEP so basically a totally unsecured network. in 2009.
I'm on my second R series. The first one was an R51 and lasted over 2 years on the road and lots of days on construction sites or in oily dusty industrial settings. The LCD started to get vertical lines on it which were multiplying. I always used to pick it up by the LCD though. It is still going strong (nearly 4 years old now) with an external monitor and ubuntu.
I'm on an R61 now and I think it is pretty solid as well. Runs ubuntu great.
I agree with another poster though that the software lenovo loads on with the default XP install absolutely cripples it. what the f are they thinking?
people who own patents have to license them on fair, reasonable and non discriminatory terms. They can't prevent other people from licensing it by charging more than it is worth.
that is what i thought too. 80% efficient! Its not like wires are 100% efficient.
I'm more interested in this type of technology for charging all the various devices with batteries without having to have the right assortment of cables and adapters.
I've been using chrome on linux for months. it is way faster than firefox in every way and flash works just as good as it does in opera or firefox.
The developer tools don't seem totally finished, but for the most part are a replacement for firebug for my purposes.
there is an annoying regression right now where select drop downs don't hide after you've made the selection but that is fixed in webkit and chromium trees so I'm just waiting for the next dev release to trickle down...
Slashdot Mirror
now here's a question, when converting voltages for DC transmission lines, do they step it up with a standard AC transformer before rectification or does the voltage get boosted on the DC side after the rectifier, or as part of the rectifier?
pretty much still need AC to make massive changes in voltage right?
there are losses on DC lines as well. P=i^2R regardless if it is AC or DC, but with DC you normally have less I because your V is higher.
stations have losses if they are stepping up/down AC voltage and if they are inverting/rectifying between AC and DC. I bet the losses are less in an pure AC facility than a DC/AC
so anything long distance and high voltage is DC.
that is plain wrong, there are 735 kV AC transmission lines and AC transmission lines span the country.
and hydroquebec's 735kV lines also get affected by solar storms leading to grid instability and are the reason no other grids are connected to it except by DC. Hydroquebec had done a lot of interesting things though, they have named all their assets (lines, switches, etc) random strings so there is no confusion as to exactly which you are referring to. people can't memorize circuits and line numbers by pattern and then accidentally refer to the wrong one.
However, it wasn’t until the HydroQuebec Power Grid blackout in Quebec, Canada, in March of 1989 that the world truly realized the extent to which solar storms can impact the economy. The solar storm induced a nine-hour blackout which affected 6 million customers and ultimately cost this power company more than $10 million — putting the cost of this disaster in the same category as hurricanes and earthquakes (and this does not include the estimated cost to its customers, which was in the tens — if not hundreds — of millions of dollars) (Windows to the Universe Team, 2000). Additionally, Public Service Electric and Gas in New Jersey suffered serious damage to two of its transformers. It cost PSE&G eight million to replace the transformers and the cost of replacement energy during the time the transformers were taken out of service was approximately $16.8 million, so the net cost for PSE&G was over $24 million. Together, this single space weather storm cost Hydro Quebec and PSE&G more than $30 million. Comprehensive real-time protective space weather prediction services could have significantly reduced damages and costs. Hydro-Quebec’s solution to the blackout was to install devices that block solar storms created geomagnetically-induced currents from traveling through its transmission lines. Unfortunately, this solution is extremely complex and expensive ($1.2 billion) (Quinn, 2000).
It was soon realized that the key to protecting vulnerable high tech systems is the ability to forecast solar storms and to take appropriate measures to avoid (or at least minimize) potential damage before they strike the Earth.
Thanks to data from new sensors and improved forecast models, NOAA’s SEC forecasters were able to alert electric power customers 40 minutes before a solar storm hit the Earth on May 2, 1998. In response, electric power utilities were able to successfully divert power and increase safety margins on certain parts of the grid to avoid stress on the power system.
Researchers have found that local electricity prices in the northeast increase in response to the regionalized effects of solar storms. Specifically, in research supported by the National Science Foundation, Forbes and St. Cyr (2004) note that space weather disrupts the system that transmits the power from where it is generated to where it is distributed to customers. In examining the determinants of the real-time electricity price in the market over the period June 1, 2000, through Dec. 31, 2001, they concluded that solar storms (over this period) increased the wholesale price of electricity by approximately 3.7 percent or approximately $500 million over the 19 month sample period.
welcome to the real world, where building the perfect system costs more than it is worth and there are physical limitations to what is possible!
What % change would you expect the system to be able to handle? Generators are physical spinning machines with inertia, and the mechanical source turning them can also have inertia. You can't stop them on a dime, that power has to go somewhere.
Take one of the 17 generators at the hoover dam. 2GW total capacity there, maybe 111 MW per machine.
Power = head x flow x 9.81
111 MW = 221m x flow x 9.81
you have 51,000 litres per second of water moving through the turbine.
That water is going through the turbine at 85mph and can't be stopped instantly if there is a sudden huge drop in demand.
When the electrical load on a generator drops suddenly and the mechanical power in doesn't change, the machine accelerates. If it accelerates indefinitely it flies to pieces, so yeah, they shut them down if they accelerate past a certain speed.
I know electricity seems like an on/off perfect thing where you can plug in whatever you want where ever you want and it just works, but that is only because what you are plugging in is insignificantly small compared to what is powering it.
37,000 MW for 25 million citizens? that seems reasonable to me.
Ontario has peak loads of 26,000 MW for 13.5 million citizens.
the new interconnect should help prevent this behaviour as it will allow the transfer of power between regions where it was previously not possible.
I think american super conductor did the superconductor grid in new york city. it has definitely been done before and is a proven technology.
P(three phase)=root(3)*I*V(phase to phase) cos theta
for a 500 kV AC transmission line, with power factor .8
5x10^9=root(3) I (500x10^3) 0.8
I = 7216 Amps per phase.
I don't think they make cables big enough to carry 7000 amps.
Say you can get 1000 amps on a cable. you are going to need 7 500 kv circuits.
with 2 circuits per tower you are going to need 3.5 500kV transmission lines and all the shit on either end to handle 7 different circuits.
so 1 DC superconducting circuit might in fact be cheaper, especially over such a short distance.
great stuff
Looks like I was wrong on that one. It is funny reading my post now, I state that they definitely have to take cash by law but I really have/had no idea and was talking out my ass.
stores always have to accept cash. it is legal tender, you can't not take it.
Maybe they can ask for some ID if you are using cash, but they definitely have to take cash by law for anything you can buy.
actually there are private clinics you can go to for some things
one advantage of all this openness is that people can come up with new and unexpected uses for devices. Maybe the board has a mini-pci slot on it and they want to swap in a mini-pci card that does something totally different.
People have added memory to their linksys WRTs... I'm trying to say when the software is open, the hardware can be modified and extended too.
he reason for keeping drivers closed isn't about revealing inner workings of your chip
one reason is that an open source driver could allow the user to use a frequency not allowed by the spectrum governing body where they live. The ISM bands are not exactly the same everywhere.
Broadcom may not be able to sell a radio that can transmit outside of the ISM in north america with an open source driver because it would then require a license from the FCC.
http://oldwiki.openwrt.org/TableOfHardware.html
That list has over 100 routers in it!
indeed, it appears that even with openwrt you are stuck with kernel 2.4: https://forum.openwrt.org/viewtopic.php?id=22016
The thing I understand for many of the targets that are Broadcom is that their drivers are impossible to get. You only get the binaries for the driver and they only work in 2.4.
So, if they did not release the source for the Broadcom drivers, you can't easily port it, unless you use b43 which is the reverse-engineered drivers.
and even then the product is somewhat lacking:
from http://www.myopenrouter.com/download/13853/OpenWRT-Firmware-for-NETGEAR-WNR3500L-BETA-09-18-09/
* WPA and WPA2 are not working.
* SAMBA support is not present.
* NAS can be accessed only through command line using utilities such as ftp
* and No GUI support to access NAS is available till now.
The patches and the script in this release are based on
I mean, no WPA? stuck with WEP so basically a totally unsecured network. in 2009.
i use mikrotik routerboards with ubiquity cards.
i dislike the company and i'm pretty sure they are GPL violators but in general you can get their product to meet your needs for cheap
hawaii.
there are plugs at both ends which can offer some resistance, probably more than the wire itself.
I'm on my second R series. The first one was an R51 and lasted over 2 years on the road and lots of days on construction sites or in oily dusty industrial settings. The LCD started to get vertical lines on it which were multiplying. I always used to pick it up by the LCD though. It is still going strong (nearly 4 years old now) with an external monitor and ubuntu.
I'm on an R61 now and I think it is pretty solid as well. Runs ubuntu great.
I agree with another poster though that the software lenovo loads on with the default XP install absolutely cripples it. what the f are they thinking?
people who own patents have to license them on fair, reasonable and non discriminatory terms. They can't prevent other people from licensing it by charging more than it is worth.
that is what i thought too. 80% efficient! Its not like wires are 100% efficient.
I'm more interested in this type of technology for charging all the various devices with batteries without having to have the right assortment of cables and adapters.
I've been using chrome on linux for months. it is way faster than firefox in every way and flash works just as good as it does in opera or firefox.
The developer tools don't seem totally finished, but for the most part are a replacement for firebug for my purposes.
there is an annoying regression right now where select drop downs don't hide after you've made the selection but that is fixed in webkit and chromium trees so I'm just waiting for the next dev release to trickle down...
I don't get why an average Joe needs a Core 2 Duo laptop for Word processing and surfing the web
Joe's flashtube can peg a core at 100% but he can use the other one to kill it?
4) Profit!!!!
that won't fly.
Your hot water might be a bit less hot or your pool not as clean though