Blackstart Training Gives System Control Operators a Peek at “Nightmare Scenario”

(BENSON) — It’s a nightmare scenario no one ever wants to see:  The entire western power grid is down.  No one knows why.  All anyone knows is that no power is flowing.

Getting the power back on in this situation is called “blackstart,” and it would take a huge and highly coordinated effort by every utility in the state to get the system up and running again.

It’s why a sophisticated “blackstart training” exercise involving all utilities that could be affected is held annually, and that includes AzGT transmission and generation personnel, who are the key people who would be tasked with restoring power.

If it actually happened, the priority for everyone would be to ensure power was being delivered first to the Palo Verde Nuclear Generating Station near Tonopah in western Arizona, and AzGT system control manager Jimmie Jones said the reason is simple: to prevent a meltdown.

“The priority is to build what is called a cranking path and get startup power to Palo Verde Nuclear Generating Station to give them safe shutdown power.  That’s the number one goal.  Palo Verde has to be in a safe, stable mode before we’re even considered,” Jones said.  That power would be imported from the Glen Canyon and Hoover dams.

However, that doesn’t mean we’re sitting in the dark forever.  The control centers have their own generators, which would go online automatically in the event of a major crash.

A “cranking path” would be established from GT4 to the Unit 2 and 3 motor control centers, “then we would build from there to start the rest of Apache,” Jones said.

You might think operators would be moving as fast as they can at all the various emergency and backup control areas, frantically trying to restore power.  Nothing could be further from the truth.

“We follow the restoration plan slowly and methodically,” Jones said.

“We start by getting the system set up for restoration by opening breakers all along our system, getting it to what we call ‘stripped.’

“That way, we don’t miss something.  If we miss something and power is suddenly restored and we pick up too much load, we crash the island,” Jones said.

It’s possible a crash would impact the system all the way back to the Tucson “island,” causing it to crash in a classic domino effect.

Jones’s way to putting that in perspective is an understatement, to say the least.

“That would not be a good thing,” Jones said.

The impact of making a mistake is greater during a blackstart event for one simple reason: the system is already unstable.

“The entire western grid is interconnected and stable during normal operation, but this situation is not normal and we would be in these islands,” Jones said.

All of the “islands” have to be carefully interconnected and if one is “out of balance,” where load and capacity don’t match, it could bring them all down.

“It’s very important we coordinate with the Balancing Authorities that are tying the islands together, as well as the reliability coordinators looking at the whole, big picture.  They see it and they give permission to tie the islands together,” Jones said.

Restoring power at Apache and delivering it to the transmission system in a real blackstart event would take hours, if not a day or more.  Jones said he hopes we never have to actually find out.

But if we do, he says, we’re ready—thanks to a sophisticated blackstart training simulator and dedicated operators who have sampled the “nightmare scenario.”

Fast Facts:

North American Electric Reliability Corporation (NERC) requires all system operators to have 32 hours of emergency operations training annually.

In a real blackstart event, three “cranking paths” would be created to deliver power to Palo Verde Nuclear Generating Station—primarily from hydroelectric generators on dams.