power failure causes and effects

Fri Aug 15 04:51:48 UTC 2003

On Thu, 14 Aug 2003 19:12:04 -0700
 Fred Heutte <aoxomoxoa at sunlightdata.com> wrote:

It looks like DC may have had a close call - the University of Maryland was
dark for about 1 hour, and I have heard several news reports here stating
that the local (DC regional) power grid just managed to 
decouple from wider East Coast grid in time to avoid a collapse here.

Regards
Marshall Eubanks

> 
> Most of the early rumors about causes of the power failure
> have proven incorrect -- fire at a New York City power plant,
> etc.
> 
> Most likely is a congestion failure in the Niagara-Mohawk
> grid, which covers a large part of New York state and has
> feeders across into Canada.
> 
> Congestion failures happen when power flows through a
> particular switching station are high, and a component
> fails either directly or because of a power surge caused by
> a failure elsewhere.  
> 
> The imbalance caused by an open or short circuit will then
> immediately spread through the rest of the grid unless action 
> is taken to disconnect, or point failures occur (resulting in fires 
> and explosions from degradation of power transmission 
> equipment, transformers, etc., not a pretty outcome at all) -- 
> or both.  In general, transmission grids are designed from a
> failsafe perspective, meaning that it is much safer to cause
> rolling brownouts or blackouts than to let key components
> such as transmission substations or power plants have a
> catastrophic failure.  
> 
> Since the entire grid has to be in sync and supply and demand 
> must be in relative parity at all times, the usual strategy in 
> these cases is to isolate the affected area, "island it" by
> shutting down power ingress and egress (tripping safety
> breakers at major crossing points), and shutting down
> power plants in the vicinity that will have stress failures
> if they don't have sufficient load to balance their output.
> 
> The problem is that power travels faster than even the
> highest-speed switching equipment can operate, so the
> surges causing a cascading failure like this afternoon's can 
> spread very quickly, like ripples in a pond.  
> 
> The weather was hot and humid but completely within
> range for the time of year, so this has to be counted as a
> "normal accident."  It's likely that whatever component
> initially failed and triggered the shutdown was within 
> its usual tolerances and simply had an ordinary breakdown.
> Of course, to spread, a massive outage like this also exposes
> other weaknesses and hidden dependencies in the system,
> which might be other physical components, software,
> operator error, etc.
> 
> The system is remarkably resilient in most circumstances,
> which is what five-nines or more is all about.  But rust never
> sleeps, and underinvestment in key transmission corridors in
> New England, New York north of Manhattan and in
> parts of the Midwest is no doubt an underlying cause.
> 
> As to the root cause of that engineering problem -- the
> answer is politics, some of it congressional, and I will say no 
> more in this forum.
> 
> Fred Heutte
> 
> Portland, Oregon
> energy policy analyst and net geek
> 