HOW DID IT HAPPEN?
Super cell storms with cyclonic winds ripped more than 20 transmission towers in SA's north out of the ground, bringing down three major transmission lines. Lightning also caused damage to energy infrastructure with 80,000 strikes hitting the state over a short period. It's believed that when the transmission lines came down, the frequency of the grid dropped to a point where an automatic shutdown was triggered, but investigations are ongoing.
DID RENEWABLE ENERGY PLAY ANY ROLE?
Energy experts say no. "It's basically just unlucky in terms of both timing and location. It could happen in NSW, it just so happens it happened to be in the state with the most political discussion around renewable energy recently," Dylan McConnell, a research fellow at the Melbourne Energy Institute at the University of Melbourne told AAP. He says that even if SA's two coal power stations had been operating (they're now closed) they wouldn't have helped because they're on the other side of where the infrastructure was damaged.
SO WHY ARE POLITICIANS TALKING ABOUT RENEWABLE ENERGY TARGETS?
Several politicians, including Prime Minister Malcolm Turnbull and federal Energy Minister Josh Frydenberg cited the "instability" renewables bring to an electricity system. Michael Brear from the Melbourne School of Engineering says there is some instability but it's manageable.
"It's important that ... we don't confuse what is a very unusual situation with what is normal operation of a system when things are operating perfectly as has been happening in Adelaide in the days prior," Professor Brear says
WHAT IS INSTABILITY ANYWAY?
What they're probably referring to is how an electricity grid is managed for frequency. Demand and supply have to be kept equal in the grid and that's monitored by keeping it at a set frequency (in Australian it's 50 hertz). When demand increases - for example when you switch on any appliance - and supply doesn't increase to match it the frequency drops. Normally when that happens, the energy company will turn on more generators (in simple turns) and there is a whole market in place to cope with this.
Brear says coal and gas power plants have turbines that can be controlled to spin at 50 hertz but wind turbines spin at their own speed, meaning the grid frequency needs to be managed elsewhere.
HOW CAN A RENEWABLE ENERGY TARGET CHANGE THINGS?
Turnbull and Frydenberg have slammed state governments for setting "aggressive" and "unrealistic" renewable energy targets of 40-50 per cent, much higher than the federal government's target of 23.5 per cent. But Brear says the renewable energy investment in SA has mostly been attracted there by the federal government's target.
"The discussion about state versus federal energy policies is an entirely separate discussion to what happened yesterday," he says. "But of course good policy is always desirable and a good national policy is always better than a good state policy."