Effects of high voltage & current on a large volume of water

For a book that I’m writing, i need to know how to describe the following, if the situation described is ever possible, otherwise I'll have to come up with another scenario.

A surge of high voltage electricity at a gas-insulated switchgear creates a flashover whose Breaker Current Failure Detectors have been deactivated so that the arc is sustained during 37 seconds. The whole installation is secret so it is located underground.

There is a steel tank of water close-by whose capacity is 34 million litres buried 65 meters deep into the ground. It is three quarter full. The ground is rock but if the material matters (it probably will) this can be changed in the scenario. (distance between switchgear and tank should be less than a kilometre). The electricity is diverted into the tank.

The questions are:

How intense should the current be to flash the water into steam, burst the tank and produce a mini earthquake on the surface?

Could it also produce a steam geyser that lasts for a couple of minutes?

Corollary effects will collapse houses on the surface and injure a small population due to steam burns.

Thanks a lot for your answers. I apologize in advance if my request is too farfetched. My formation is not physics. I'm just looking for some believable situations.

Last edited by a moderator:


Science Advisor
Homework Helper
Hallo Eric, :welcome:

Heat needed to evaporate water (from 100 C water to 100 C steam) is about 2 kJ/kg. You have 3/4 * 34 = 25 million kg of water so you would need 50000000000000 Joules ( 5 x 1013 ) just to evaporate the water. That's a lot.

A big lightning strike is 10000000000 Joules ( 1010 ) so you'd need the energy of 5000 of them.

Or, to come back to your 37 seconds: per second you need 1.5 x 1012 Joules, i.e. one and a half million volts discharging with one million amperes.

Other terms: one ton of TNT is 4 109 Joules, so you'd need 12 kiloton of the stuff. Half a Fat Man

On the bright side: I personally wouldn't feel cheated at all when such a spectacle evolves on a movie screen.
Thank you so much BvU for your answer,
I think I'm getting closer to visualize this. But the energy needed is fantastic! Is there any hardware that could withstand this voltage and amperage without frying or vaporizing before the 37 seconds have passed? I mean to continue discharging electricity without failing?

I really appreciate this,
This is of huge help to me.


Science Advisor
Homework Helper
Well, I don't know of a way to store so much energy (except with a truckload of tnt or a nuclear device). On the other hand: why do you think it's necessary to evaporate all the water ? Heating it up until the vapour pressure rips the tank apart (google steam boiler explosion - e.g. here ) creates a hefty bang too (the rest of the water suddenly experiences a lower pressure and flashes (=evaporates), thus gaining tremendously in volume.

But 65 m of earth isn't easily stirred, I suppose.
I'm sure you're right. I probably set the parameters out of ignorance. Let's rephrase :
The event take place some 800 years into the future.
The location is a planet orbiting an F9 star.
It's a runaway greenhouse effect world. The only inhabitable areas are the flat tops of a few very high Tepuis (about 40 miles high). (See Landis's proposal about colonizing the clouds of Venus as a basis for the logic behind floating cities in high atmosphere). Those Tepuis are the result of geological stress induced by the flyby of a superdense object early in the formation of the planets in the accretion disk of the star.
Those tepuis are now isolated reservations for intelligent species of the galaxy. A kind of Vault against genocide.
They are controlled and monitored by AIs.
A couple of those AIs battle for control.
All AIs were interconnected at an earlier stage for energy sharing.
The production of energy is geothermal.
At the surface of each Tepui, there is a small settlement of each species whose numbers is artificially maintained low to avoid overpopulation and their technology is artificially maintained at a basic level.
The location of the base is usually underground (depth is not set at a mandatory 65 m, it can be adapted following your advice), directly below or not far from the main settlement on the surface.

In this case, one of the AIs manages to reestablish a high voltage connection with the powergrid of its archenemy.
This last diverts the attack to the main tank.
The Switchgear is gas-insulated. It's ultra-high voltage so it's upwards of 400 KV.
The Breaker Current Failure Detectors have been deactivated.
The flashover will be sustained as long as possible if it is relevant to the result.
The current is diverted into the main water tank directly, not through the intermediary of a resistance.
The effect must provoke a mini earthquake, destroy the tank, a part of the base and a part of the settlement. It must also burst through the surface and provoke a geyser whose high is .....? and duration is ....?

Do I need all the power you described or can it be described in another way with less power?

Thank you again, your advice is invaluable!



Science Advisor
Homework Helper
Nice story, nice setting, but more or less: End of my wits :smile:

I'll try and refer you to someone who kows a bit more about such things, only I don't know who has explosion expertise, so it may go via-via. @Chestermiller: how can we help Eric further here ?
Thank you very much for your help BvU. Pending.

Want to reply to this thread?

"Effects of high voltage & current on a large volume of water" You must log in or register to reply here.

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving