Still black in Venezuela. hz housewife flagged a very important Jo Nova post on the problems of getting up a collapsed grid.
History books will be written about this crisis. Matias Delacroix points out in Wired, that it’s very difficult to restart a decentralized grid which has been badly managed and poorly maintained. No one knows exactly what went wrong to bring it down, but fingers are pointing at the huge Guri Hydro plant, which provides a whopping 80% of the electricity.
Normally a blackstart begins with a small diesel unit to kick over a bigger turbine. Then the whole grid is gradually rebuilt bit by bit by “bootstrapping”. At all times the supply has to match the demand, so before an engineer throws the switch someone has to have already done the numbers to make sure things will stay balanced. As each new generator-load segment is added it must also match the frequency and phase set up by the original first generator. It would be dangerous to set up a bunch of little separate grids and then try to meld them together. Getting the frequency or phase wrong can cause explosions. Hence the grid must be built from one point out, and carefully. Wind or solar generators can’t be used in a black start, but a large Hydro plant should be able to do that, assuming people can open the water gates, but restarting a badly managed grid means there are many fragile failure points that don’t reboot properly. After days of darkness it must also be difficult to estimate how much load will be waiting to take new power.
There is more detail about the problems, and an UPDATE FROM THE COMMENTS
Performing a “black start” is no simple matter.
The primary problem is that everything that was connected to the grid when it crashed is still connected. So essentially, the Load is a “Dead Short” from the perspective of Generation.
Every inductive load (induction motors) takes 6 times the normal running current to start each and every one. In terms of real and imaginary (complex) power components, the Load appears to be almost purely inductive with a Real component vector of nearly zero.
Essentially, Generation must provide 6 times the power it was providing when the grid failed and that reserve simply doesn’t exist. So energizing a substation is an explosive event.
The safest / only way to restart the grid is to isolate all of the loads except residential loads and bring up the lower voltage substations (10 kV) gradually in a controlled fashion. The residential load has resistive components ( water heaters, clothes dryers, cooking ovens, etc ) that help reduce the inductive component and provide a unity power factor component to the apparent load.
Only after the lower voltage grid is stabilized can the higher voltage transmission lines and substations (110 kV to 750 + kV)be re-energized. Even so, it is a precarious dance of balancing generated power with apparent power.
When the generator is connected to the load, it “sees” a reflected wave coming back to the generator that trips the overload safeties and causes the turbine/alternator to disconnect if the apparent power exceeds safe limits. If those safeties aren’t functional, the risk is an exploding substation, alternator, sheared turbine shaft, etc.
This is a nightmare scenario. No sane person ever wants to “smoke test” a power grid by trying a black start. The ramifications are frightening.
This is specifically why keeping a stable grid operational is a lot smarter than trying to roll the dice with intermittent generation and sudden changes in loads.
Greens ought to give the situation in Venezuela a very serious consideration before destabilizing the existing grid in any location on earth.
My guess is it will take 3 to 6 months to restart the grid in Venezuela, even if things go swimmingly. If a few substations and alternators are blown out, it could take 2 years. Longer if some turbines are damaged.
Substation transformers are custom made to order. They do not exist “in stock on hand” at the power levels needed on a national grid scale. Unit substations might be available in smaller sizes, say 50 to 100 MW. But the high voltage and higher power switchgear and transformers can be a 1 to 2 year lead time item even if you have the cash to pay for them.
This is a teachable moment. Smart people will pause and reflect upon what is happening, lest it happen elsewhere. This is not a game sane people want to play. Societies melt down in a matter of days to weeks without electric power, water, food, transportation, communication, etc.
We’ve yet to see how bad this is going to get. It will get a LOT worse before it gets better.
Someone might like to explain the difference between getting South Australia up in three days while the rest of the SE Australian grid was working and recovering from a blackout in Victoria, for example.