Wednesday, April 13, 2016

Can a Distribution Disturbance Alone Cause a Cascading BES Outage?

I freely admit I’m out of my league on this one. In my post yesterday, I stated – based on a conversation with a couple longtime reliability compliance professionals – that it was close to impossible for an outage on the purely distribution side of the grid to cause a cascading outage on the transmission side.

I continue to believe this is the case, but I did receive an email this morning from an Interested Party who has contributed to many of my posts over the years. He isn’t exactly saying that my statement was wrong, but he is pointing out conditions that might lead to a more widespread, prolonged BES outage than I’d thought possible, assuming there was an initial substantial loss of load on the distribution side. Here is what he says:

“I do not fully buy into the idea that an attack against the distribution system could not impact the BES.  Understand that the Ukraine attack was concurrently directed against four distribution companies.  There is no reason to believe a similar attack in the US would not target multiple distribution companies at the same time.  The Transmission system impact of the attack will depend upon the current operating conditions and the amount of load shed.  Even if the resultant impact is only the tripping of some generation, bear in mind that it takes a while to get generation back up after it trips.  Fossil steam plants can generally get back up within 18-24 hours of available station services power.  Renewable and GT/CT is pretty much instantaneous after allowing for grid synchronizing.  Trip a nuke and it is days before the NRC allows the unit to be restarted.  Whether fast recovery generation can restore load while the slow recovery units are brought back online will depend on Transmission congestion and total load conditions.  So, yes, there are distribution outages all the time, but they are not typically widespread except during a severe weather event that damages the Transmission and distribution infrastructure.  Rather, you typically lose a substation and inconvenience a couple thousand people until power can be restored.”

In other words (and these are mine), depending on the type of generation that would go offline during a widespread distribution system outage, there could be a substantial and prolonged impact on the transmission grid. This isn’t the same as a cascading outage, of course, but it does constitute a potential substantial effect on the BES.

The views and opinions expressed here are my own and don’t necessarily represent the views or opinions of Deloitte Advisory.

No comments:

Post a Comment