Can this be mitigated by putting the cables under ground? Just curious, since it’s a huge debate here at times because of the massive cost of doing so.
Germany needs a connection from the coast into the south and most of it as of now will be build under ground.
This article explains some issues with underground high tension cables [0]:
> Laying a 380-kV high-voltage line underground poses a number of risks. The electrical behaviour of underground cables differs from that of overhead high-voltage lines. This results in a loss of transmission capacity. To compensate for this loss, additional devices (e.g. coils) have to be installed at various points along the route.
> The combination of cables and coils creates resonance similar to a radio where multiple jammers continuously change frequency. Cables and coils can cause disruption locally, jeopardising the stability of the entire grid. In addition, it is easier for Elia to identify faults and carry out maintenance on overhead lines.
I had always heard that underground is workable for local areas but the really high voltage long-distance lines are hard to insulate undergound (on pylon towers they are not insulated at all).
There are significant inductive losses with having AC under ground - dirt is conductive enough you end up with induced current (inductive losses) in it. Same with seawater.
It’s doable; but for longer distance runs when buried or under seawater, it’s usually more economic using DC which doesn’t have that issue.
High voltage DC is effective above ground, too. At high enough voltage, it's actually cost effective and has fewer electrical losses than the AC equivalent. China has been doing some cool investments on high voltage DC in the past 15 years or so. We're talking 750 kV and above IIRC.
HVDC is the grid's distant future if the future is mostly solar. Why bother inverting to AC if everything making the power is fundamentally changing over to DC?
Easy: because DC voltage conversion is way harder.
You can't really build a "grid" out of HVDC, because you can't easily convert between what the solar plants produce (a few hundred volts), what the local distribution grid needs (a few thousand volts), and what is needed to get that power across the country (tens of thousands of volts). On the other side you need to convert back down to a city-level distribution grid, down to a street-level distribution grid, and in your home down to whatever your equipment needs.
DC-DC conversion is significantly more expensive, more failure-prone and less efficient than AC-AC conversion. Why bother with a bunch of expensive active electronics when a simple transformer can do the job even better? Besides, who's going to pay to retool the entire country? Just because a solar panel produces DC and your computer needs DC doesn't mean it's viable to use DC for the entire chain.
HVDC is excellent for long-distance transmission lines, especially when power almost always flows in a single direction. Want to hook up a solar plant in the desert to an urban area 1000km away? Use HVDC! Replacing the entire grid grid with it? Probably not the best idea.
This. AC generation is also way easier to reliably engineer at high power than DC.
Remember, early generators from Edison’s company were DC. They caught fire _constantly_. Obviously technology has caught up since then but AC power generation and distribution is simpler engineering overall. Use HVDC where you need it and it is cost effective to do so.
>>Can this be mitigated by putting the cables under ground?
Yes, it can (apparently), since these are mostly indirect effects of atmospheric vibrations (aka 'wind'). The vibration itself isn't usually the root cause of a blackout — but it sets off a chain reaction that leads to one (line contact/short circuit; conductor breakage; overcurrent & load shedding; protection system malfunction or overreaction, etc.)
It's vastly more expensive to put cables underground, and high voltage cables underground is in the realm of Bad Ideas because you're putting a high voltage physically near the electrical ground (the earth's crust), which adds cost, reduces reliability, and poses a serious danger to all living things near the line.
Sure, there may be exceptions that might make it worth while. However, if long distance high voltage underground wires was practical and cheap, you would see deployed much more often.
> poses a serious danger to all living things near the line
That is always the case for the various failure modes of any high voltage line (and all the related equipment).
That said, you have it exactly backwards. Above ground lines are much easier to inadvertently come into contact with. Once faulted the breaker trips within a matter of milliseconds. It's the initial contact that's deadly.
Germany needs a connection from the coast into the south and most of it as of now will be build under ground.