Mains power voltage drop to reduce usage?

Are all insulators dielectrics?

Potentially.

It seems to be a symptom of the rail industry at present that someone needs to attend in person to reboot, instead of the person who is already on-site (the driver) being able to do it (with suitable checks and authorisation first).

It's like the events leading up to the Stonehaven crash when a signaller was not able to move the points to switch the train from one track to another, but instead the train had to wait for a signal technician to drive there to move the points. Have whatever safety checks are necessary, but once those have been passed, give the person on site the authority to restart things without waiting for people to attend from elsewhere.

That's what's wrong with the rail industry: too much emphasis on process, and not on "just f-ing do it". The needs of passengers are paramount.

But they didn't know that at the time so they shed the right amount of load but because that also dropped a lot of local generation as well they were forever playing catch up. The grid didn't respond as expected when they shed the 1GW because then net shedding was only 400MW.

It took them time to realise what was happening and by then they were forced to shed even more load to regain control. They managed to rebalance the grid and get the frequency back in tolerance in under 5 minutes which isn't bad going but they had to drop off rather more load than was strictly necessary because of the way that local generation has altered the rules of the game.

If you're gonna start on that, the superconductor left without resistance.

Just what checks are needed to turn it back on because of a powercut? Clearly a driver already knows how to see where other trains are. In fact if a diesel train was oncoming, he'd be a lot safer being able to start it!

But "a signaller was not aware of any obstruction on the line." -

The same should apply to the police at a road accident.

If it's automatic it should have been a couple of seconds surely?

So the idiot in charge had never heard of local solar generation.

Then why waste your time reading them? You do know how to use a killfile, right?

No, you back down when you realise I'm correct.

Ability to form a capacitor is connected to the formation of dipoles in the material Monopoles are characteristic of conductors.

I'd say you should know why there was a power cut in the first place.

What makes you think it has anything to do with the trains. Could be something dangerous on teh track or ever a powerline down.

yes more people die in car crashes than in trians.

There must be some insulators which cannot form dipoles.

What happens if they simply lower the Pantograph? I suppose they do that eventually, when parked.

With at least a relative permittivity of unity.

Only useful if you know what a dipole is, and an insulator.

Of course taking into account, there is no such thing as a perfect insulator, and no such thing as a perfect conductor, superconductors excepted.

Certainly. Every insulator has a dielectric constant.

If you mean "is every insulator suitable for manufacturing cables and capacitors?" some aren't. Gasoline and crumpled newspaper might be poor choices.

But then, capacitive liquid level gages use gasoline as the dielectric.

A negative permittivity would be fun, but violates conservation of energy. Negative capacitors are easy; I did one as a school project but it had a battery inside.

Vacuum is a pretty good non-polar insulator. Er = 1. Insulation resistance is excellent.

Its breakdown voltage is impressive, but enough voltage gradient will rip atoms off any metal electrodes. Around 1e10 v/m as I recall.

When I tourismise, I take my car.