Railway lines are different to roads, the analogy is an electricity carrying cable vs a data carrying cable.
In data lines and roads you don’t physically connect and disconnect branches, they are always connected, the cars / packets have individual control, they know where they are going.
In railways and electrical systems (and pumping systems etc) you do physically disconnect and reconnect circuits in order to direct flow.
When I was a boy it was done manually, signalman and booking boy in every signal box, and an arcane system of levers and electrically operated bells for them to communicate with others.
Of course it required a skilled human being because it was a manually operated system, even if they were working from books of rules and schedules and so on, but it was a human hand that made every single change.
Which is why during wartime and so on it was still possible to make a crippled system work after a fashion, and why it was possible to bring new elements on stream as they became available / got rebuilt / whatever.
It was the same with mains, the worst thing you can do is just switch in another generator that is out of sync with the existing circuit, massive destructive currents will flow, but the way it works is if you have 5 x 500 kw gennies running in sync, and you add a 6th, they will all keep each other in sync, once synced up, if one drops engine power it will still stay in sync, the generator will just act as a motor and spin the dead engine, in practice a relay trips that unit out of the circuit, so you do your repairs, sync it up, and put it back on line.
I’ve done this myself on boats, and syncing was done with an ordinary filament bulb that bridged the two circuits, if they were out of sync current would flow and the bulb would illuminate, and like multi engine bombers you could not manually get them perfect (hydraulic governors of the day and so on) so what you’d get is a harmonic, with the bulb waxing and waning over a few second, so one eye on the bulb, one hand on the switch, and when the bulb went out you threw the switch and the new gen set was on line and in sync.
If the bulb waxing and waning happened too fast, eg it was less than a 4 second cycle, you had issues, and you go and check / adjust the governor on the offending gen set.
It didn’t matter if you were switching between port and starboard gen sets or a gen set and shore power, it all worked the same way.
It’s crude and inelegant and 100% human hand operated, but it works.
Fundamental to all of these systems, is that being human operated, you could start from a dead system and build it back up online.
The downside of course is there are no millisecond or less reaction times, then it went to semi automatic systems with synchroscopes and cosine meters, and then it went fully auto, with a “manual” backup that is really no more than a button wired into the same auto circuits to over-ride the output of the op-amps or FGPA or whatever they use now, it’s fly by wire when it is “manual”
There isn’t really any dead in the water cold start ability any more, unless you want to start it as an isolated unit, the design always assumes that sooner or sooner still as soon as that subsystem is running, it gets connected to a master system and takes its cues from there.
Much like the internet.
And then it gets worse, because once you take the human hand out of the system and you have the ability to tweak things at will at the microsecond or less level, that is exactly what you will do, in the name of “efficiency” or “profit” or “copyright” or “law”.
It should alse be said that the challenges of adding a 2 MW generator to the grid are not the same as the challenges of adding a 700 MW genny to the grid, one will just trip out and blow up if you get it wrong, the other will cascade crash the grid itself.
But yes, the tweaking starts, why not, no obselete human meat with multi second or even multi minute response times, and an internet that was built to route around damage, is now built to be damaged from the ground up, this is afterall what firewalls and routing tables and domains and so on are.
On a purely IP based system life would in many ways be easier, once you add, for example, that fucking dweeb in mom’s basement to your block list, his packets ain’t going anywhere, sure, you have to add white listed people too, and that takes too much time to do manually, and we fucked up the allocation of IPV4 (as we are doing with IPv6) such that 18.104.22.168 and 22.214.171.124 are not necessarily geographically near to each other.
Back in the day in the UK before STD (subscriber trunk dialling) our phone number was 811, there were plenty of unused numbers below that for that village, but the 800 to 988 block was assigned to the new housing estate that we lived in, and being down towards the bottom of it, we had 811, the guy across the road was 813…
In the old films Scotland Yard was always Whitehall 1212
So there have *always* been opportunities to do everything right, from an engineering perspective, but they are never done right, because some bean counter somewhere came up with a “better” way.
As I have mentioned before, a friend who worked in the UK National power grid confided in me that there were six locations that if attacked would *inevitably* cascade fail the entire grid, and nobody knew for sure *if* they could bring it back on line, like the internet, it’s never undergone a cold start since it was first started.
So now we have discussions about a new chinese / french nuke plant being built, and limp wristed motherfuckers who claim to be tech experts whining about all the “dirty diesel” back up plants dotted around the country, not realising that they are some of the cleanest running non nuke or hydro power sources anywhere, not realising that if we do have to either segregate or cold start the grid, these “dirty diesel” plants are the only way to do it.
They won’t generate an appreciable proportion of our power needs, that is not the fucking point, before you can have a grid you have to have a clock, everything in sync, and that’s 50 Hz here in europe and 60 Hz in the yewessa, and you can’t get that clock running without “dirty diesels” and only THEN can you think about bringing the bigger stations online and only THEN can you think about putting towns and cities and industries back on line.
Which brings us to another thing, the aforementioned mate sent me a graph, grid power usage when 9/11 happened, and everyone picked up the phone or went online, and the bad news is back then in 2001 fifteen fucking years ago that sucked up 10% of the UK’s generating capacity.
Back then you’d manage grid loads by running in brownout conditions, the frequency stayed the same, but you dropped the voltage, and by the time you dropped the 220 supply to 160 lost of shit just stopped working, which was the point, but filaments bulbs still glowed, albeit dimmer and a resistance heater still worked, albeit not nearly as powerful, so people still had light and heat, but everything else shut down by itself in an undervoltage condition.
Nowadays nearly eveything works on switch mode power supplies, you can cut that 220 back to 90 and that sucker will still work and still power the device it is connected to, except it will be drawing nearly three times the curent, so your brownout will trip current breakers and turn into a blackout.
Then it’s engineers going out and kicking back online the power, sub station by sub station, maybe even pole pig by pole pig…. your neighbourhood could well be 14 days without power.
My mum had a power cut last week, line under the street went and took about 30 houses offline, no electric means no gas central heating or hot water, no cordless phone, no lights, basically nothing.
Took the power company about 18 hours to get there with a gen set, dig up the road, access the cables, splice in the genny and put everyone back online.
My mum was the only one who had a portable gas burner to make hot drinks and portable LED lighting to see if need be, the gas burner had been sat in her cupboard for 18 years, waiting for the day.
But she is in her mid 90’s, came from a different world, all the younger folk around her could do was watch the dwindling battery charge on their mobile phones as they texted everyone about how awful it was, nothing worked, not even the TV.
Dead in the water.