Fact Check on High Voltage Power Lines

I am working on a piece of fiction and would like to fact check one of the scenarios in the story dealing with high voltage power transmission lines in the 500+KV range.

In the story a group designs and builds a harpoon gun like device which launches a steel cable that is connected to a ground rod over a high voltage power transmission line.
The steel cable crosses all 5 of the 500KV lines and connects them directly to earth ground.

Now the question is what would happen in reality if this was done. Would the cable vaporize due to the extreme voltage or would they succeed in causing a major blackout? If it did succeed about how long would it take to reset the system to restore power? (for example the equivalent of flipping a circuit breaker or would more serious work need to be done once the short to ground was located?)

In this story a totalitarian government has taken control which uses its information gathering technology to systematically oppress it's citizens so the 'rebels' hatch a plan to unplug 'The Beast', possibly by using several of these devices at key locations.

Some other reference links related to this work of fiction:

Link 1

www.energy.vt.edu...

And, no I have no plans on acting on any of this information other than to work on this fictional story, so there is no need to kick in my door at 3am and cart me off with a black hood over my head

eb




[edit on 28-3-2009 by Razmear23]

[edit on 28-3-2009 by Razmear23]

Originally posted by Razmear23


Now the question is what would happen in reality if this was done. Would the cable vaporize due to the extreme voltage or would they succeed in causing a major blackout? If it did succeed about how long would it take to reset the system to restore power? (for example the equivalent of flipping a circuit breaker or would more serious work need to be done once the short to ground was located?)

I

It depends on how big the cable is. The larger the cable is, the better the chance of success is. I don't know how long it would take to restore power. If I had the time and knew how to put pics on here, I would show you a better way and it would take a lot longer to repair.

reply to post by Razmear23


Truth is most likely nothing would happen the power lines are insulated they are not bare wires. and as far as repairing most power companies could have new lines strung in about 2 to 3 hours. The other part interupting power in one area may not bring down the grid power lines are so interconnected that power will probably still make it to areas of the grid. I would advise you how to take out an entire grid but i think we best not talk about that here.

reply to post by dragonridr


High power lines ARE bare wire. The reason is that the insulation used on wire conducts electricity at about 600 volts, I think, and would be useless. I agree that the grid is so interconnected that it would be hard to disrupt power for a large area.

If you did this the protective relays would open and the line would go off line.
The steel cable would vaporize and spray molten steel all over.

I suggest that you research an outage that occured on the western grid in the late 90's early 2000's. It blacked out most of the western US for a day.

Good point i was thinking about after substations once it enters into neighborhoods it goes to shielded cables before that its usually aluminum lines. It would also depend on if they were using direct current or Alternating depending where on the grid you were and how your electric company decided to use there electricity.

reply to post by dragonridr


1) The lines are NOT insaulated whatsoever.
2) The current actually forms an electromagnetic field outside the metal periphery to propagate not through but around the cable, so insulation would serve no point at all.
3) If you doubt these facts, you are up to a hell of a lot of reading and study.

Peace

reply to post by Razmear23


I think one could do just as well if not better with multiple strands of aluminum foil.

Thanks for the replies so far.
The 550 KV (550,000 volt) lines are all DC current. If they were AC there would be no way to keep the cycles in synch over a distributed network.

One of the major US blackouts was caused by one of these transmission lines being grounded out, (Id have to re-google it to remember which one) so I think the main flaw in the scenario would be if the steel cable would melt or not.
Back in the whaling day they used harpoon guns with pretty hefty steel cables, so I would assume that a big enough wire could be launched the 500 feet or so needed to clear the power lines at about a 45degree angle.

Because there seemed to be some confusion over what type of power lines I'm referring to, these are the big towers that carry power very long distances. The second link in the original post shows a state map to give you an idea of the network.

The power grid is very interconnected, but that does not mean that power is more likely to continue flowing when one section goes down, it's exactly the opposite as when one section fails the others get overloaded and trip off line to prevent system damage. I believe this is called a cascade effect.

If you have any more effective scenarios for my fictional rebels, please feel free to share.

eb
.

get a few guys over the radio (in your story) to blast some pilars in various ares since not everybody would have the cable launcher to unleash havoc...
However i doubt the NWO would suffer much. I would guess regular citizens would take most of the hit alongside industry.

Also destroying 2-3 pilars in a raw would make repais time consuming.

Originally posted by waterdoctor
If you did this the protective relays would open and the line would go off line.
The steel cable would vaporize and spray molten steel all over.

I suggest that you research an outage that occurred on the western grid in the late 90's early 2000's. It blacked out most of the western US for a day.

I'm not so sure about that - about the cable vaporizing. People/animals can vaporize, but not the cable unless it was a small cable (like bailing wire). Assuming the cable is the same gauge as the power lines, then if the cable were to vaporize what would prevent the power lines from vaporizing?

People vaporize because their body provides large resistance to the circuit, which the power lines laugh at and POOF. But a large enough cable wouldn't provide that same level of resistance, it would just provide a conduit to the ground.

However, the OP states that all 5 power lines would be bridged together as well as to the ground, so you'd want a cable that could handle that much power. My guess is that the last substation would break the circuit. The power line people would then have to fly a helicopter down the line to find out what the cause was before they could even attempt to start it back up.

If you were to do this and wanted to maximize delay to the fix, you'd want it to be in the most remote location possible, during the worst weather possible. If it's cold and snowy/windy/rainy it makes everything more difficult to assess (helicopters can't fly well in a storm).

Also, in a bad weather scenario, they might initially blame the fault on weather.

But if I were writing this book and the freedom fighters/terrorists (depends on plot!) were smart and wanted to cause a lot of problems, they would blow a series of towers up and down the line. That would take a VERY LONG TIME to fix. A lot longer than removing cable lying on top of some power lines.

This a all common sense, though, right?

Very good points Harry.
In this fictional world with 'Total Information Awareness' purchasing the materials needed to blow a row of towers down is a bit more complicated, which is why the 'rebels' resort to Yankee ingenuity to make these compressed air powered portable cable launchers. The design has the cable spooled separately from the launcher so it can be reloaded and used multiple times.

Regarding bad weather, snow and rain... I would assume the risk of using this device would increase greatly if the ground was wet or covered with snow. Running a half million volts to ground probably isn't the safest thing to do in the desert, doing it on snow covered ground might just be a suicide mission for these rebels.

eb


[edit on 29-3-2009 by Razmear23]

Originally posted by Razmear23
The 550 KV (550,000 volt) lines are all DC current. If they were AC there would be no way to keep the cycles in synch over a distributed network.

Power grids and distribution lines work on AC, not DC, because DC cannot be stepped up or down, though all the electronic devices work on DC, the conversion is done using the rectifier present in the electronic device itself.

reply to post by Razmear23

That makes sense, about the explosives. But I would argue that getting a cable large enough to short the circuit without vaporizing would be a very HEAVY cable. If you go out to where these large high tension lines are, some are over hundred feet high (higher in some places) and cover a lateral distance of another hundred or so feet. Those lines are thick, so with the length, to "unwind" a cable on a spool would require more than the force of the launcher could provide, because the launcher would only provide force at the beginning of the launch. After the launch the spool would "tug" backwards because there would be the weight of the cable plus the energy to get the spool rotating (which includes the weight of hundreds of feet of cable). The spools would have to be motorized and timed with the launch to unwind quickly. That would take a very sophisticated piece of equipment. Add to that that as soon as the first cable touches a line, the spool equipment will get fried, so it's a use-once-and-lose-the-equipment type of situation.

Not to mention, that amount of cable would be VERY difficult to purchase in a society such as the one you describe without setting off some red flags. You can't just buy some down at Home Depot. And if they get the cable on the black market, then they should be able to get some form of explosives or acid to corrode the towers.

Heck, they could even create some sort of cutting mechanism to cut through the towers. Or, wait, I just thought of this: they wouldn't need to have a cable connect to the ground because the towers are grounded, so if they could create some method of shorting the lines to the towers, then...

I'm just playing devils advocate here, so I hope you take my comments as constructive (destructive!) criticism.

Originally posted by peacejet

Originally posted by Razmear23
The 550 KV (550,000 volt) lines are all DC current. If they were AC there would be no way to keep the cycles in synch over a distributed network.

Power grids and distribution lines work on AC, not DC, because DC cannot be stepped up or down, though all the electronic devices work on DC, the conversion is done using the rectifier present in the electronic device itself.

The local distribution lines are AC current, but the long distance 500KV (and up) transmission lines are mostly HVDC.
Here is an example with a good description of how it works.
en.wikipedia.org...

eb

reply to post by Razmear23


Looking at that wiki photo of the DC towers:
upload.wikimedia.org...
upload.wikimedia.org...

They are held up by 4 guy wires on a monopod like base. Cut the guy wires, down the tower goes. Seems like the easiest method to me. Forget the launchers man, don't you watch Myth Busters? Getting things to fly with cables and explosive amounts of energy is just messy and bound to fail in some way.

[edit on 29-3-2009 by harrytuttle]

[edit on 29-3-2009 by harrytuttle]

reply to post by harrytuttle


I also wondered what would happen if a cable was launched so that it just crosses several of the wires, eliminating the grounding part of the problem. I would assume that would also cause some havoc, but not sure what the downstream effects would be. It would certainly cut down on weight and ensure reusability of the launcher.

There is probably a better conductor for the cable, but then you are getting into rarer elements like tungsten which would raise more flags.

Regarding 'shopping at Home Depot', that's the general idea I'm going for, using items that would be readily available. I've bought steel cable from Home Depot to make tow lines for 4 wheeling and they have spools of the stuff there.

eb

I'm a Transmission Operator for an electric company and am very familar with high voltage transmission lines. In your hypothetical scenerio the most likely outcome would be a lockout of that section of the line. The protective relays at the nearest substations (near is relative, could be a hundred miles or more in the West) would see the event as a phase-to-phase fault and/or a ground-to-phase fault. Depending on the number of times that were set for retry, the breakers may wait a few seconds and attempt to close again. Many companies do not allow auto-reclosing on high voltage lines. At any rate, auto-reclosing or not, the event would be over in a few seconds and the line would be dead. A transmission line can usually survive a transient phase-to-phase fault, like one encountered during high winds, but not a multi-phase and ground-to-phase that happened simultaneously as you described.

How long the line would be out before it's inspected and re-energized would depend on how remote it's location. The exact location of the fault is known almost immediately, down to a few hundred meters usually. A line crew would be dispatched within 10-15 minutes. Arrival would depend on the remoteness. In the Western grid it could easily be 2-3 hours.

Thieves in South Africa have been tripping out transmission lines in a manner almost exactly as you describe so that they may steal the conductor.

The vast majority of transmission lines are AC. The few DC used are mostly short ties between seperate grids and are not particularly vulnerable.

There is a lot of redundancy in the electric system in North America. Probably 1/3 of the transmission lines are removed from service after peak every night and than placed back in service during the morning peak. Your fictional group would not likely cause an electrical outage in the sense that customers would lose service. But they would temporarily disrupt that particular transmission path.



[edit on 29-3-2009 by RKWWWW]

reply to post by RKWWWW


Thanks for the info RKW. I always thought the high tension lines were DC so thanks for correcting me there.

"The Beast" in this story lives in Virginia and is a parallel to the real N S A.
The rebel's goal is to knock it offline for 12 to 24 hours to provide cover for a separate operation by launching multiple 'harpoons' at key locations to temporarily cripple their operations.

Remember this is fiction, so I have some poetic license with the effects of these grounding harpoons, but I'd still like to have some basis in reality for the after effects of the operation.

Thanks again for all the info provided in this thread.

eb

reply to post by Razmear23


actually, going by the wiki article, only two 500KV power transmission paths in the Western United States are HVDC, and the rest are AC. I'm pretty sure that except for Sweden, most of the world uses HVDC almost exclusively. I believe there are around 120 HVDC power transmission systems in use in the world, which represents a small fraction of the number of power transmission systems on the whole.

en.wikipedia.org...

High voltage DC is barely a footnote in the article on electric power transmission, and it mentions using it to transfer power between different electrical grids.

So, yeah, what RKWWWW said.