How and why - are 'rolling blackouts' used?

What are they anyway?

Someone told me that the (nuclear?) facilities will probably commence, as some kind of a safeguard...in the future...

-- Anonymous, February 11, 1999

Answers

Diane, here's a definition of both a rolling blackout and a cascading outage, compliments of a Keith Karolyi post from last year:

"A Cascading power outage is when a problem in one part of the transmission or generator system affects another system causing it to fail. Example: generator fails, load on other generators rises until they are overloaded and the safety system trips shutting them down. The shutdown places greater burden on adjacent generating systems which could experience the same overload/shutdown sequence.(a cascade) A rolling blackout is something a power producer or distributor does on purpose in order to reduce the load on an overburdened system. (Example: Customers served by various substations are taken off line one or more substations at a time for a predetermined amount of time before being turned back on and another group of customers being blacked out.)This enables the power company to "ration" available power and prevent a total shutdown due to overload Hope this helped Keith

-- Keith Karolyi (keithk2@worldnet.att.net), September 15, 1998."

-- Anonymous, February 11, 1999

Diane,

Here's a pretty simple explanation of a "rolling blackout" scenario:

Say a power company has 1000 customers, but only has access to enough available electricity to supply 750 customers. We'll divide the customers in to four groups of 250.

X = thems that gets power

	Group A	Group B	Group C	Group D
6AM	X	X	X
12PM		X	X	X
6PM	X		X	X
12AM	X	X		X

 

Any place on the above matrix that doesn't have an X has power cut off for a period of time. Then, the blackout rolls to the next group on the list. In this manner, all customers "share the pain", but only for 6 hour increments. Hence, the term, "rolling blackout".

-- Anonymous, February 12, 1999

Utilities have had to develop plans to prevent blackouts when load exceeds generation for years before Y2K was an issue. This is a normal, everyday consideration in the utility business. Rolling outages is actually the last line of manual intervention. The first step is to keep the voltage up by placing capacitor banks on the system Next step involves placing peaking generation on the sytem (combustion turbines, high cost/mwh fossil units). The next action is implement a 5-10% reduction in system voltage. This slight voltage reduction causes no harm to customer equipment and unless you have a voltmeter attached to you outlets you would never know it is happening. The next step is to turn off power to industies that have volunteered to do this in exchange for discounted rates. Then comes the final manual interventions, involuntary rotating outages. There are other protections to prevent widespread grid crashes that operate automatically (this protection is totally non-date aware at my utility - I don't know the percentage of the total grid's frequency protection that uses embedded chips, but I'd venture to say that it is extremely low by percentage).

Hope this helps

-- Anonymous, February 12, 1999

(deep breath) THANK you for these answers & explainations.

First line of defense - got it. SO much better - this 'news' - is to me...

So basically it's like Yourden's recent comments, that I've thought myself all along anyway: We'll be like a Third World country! Learn to get humble, *truly* spiritual? [Alotclosertothearth]

(Well it's about time anyway!)

gdbls&drms/db

-- Anonymous, February 12, 1999

Christmas 1989

A strong cold front came through South Florida, and people turned on their heat. FPL (Florida Power and Light) seemed to be caught totally unamware that A: Cold fronts come through in December, and B: That people would turn on the heat.

This resulted in rolling blackouts for 2 days. What we heard from the media was that these would be 15 minutes at a time. No big deal. But in reality, on Christmas day alone, my power was cut 5 or 6 times for no less then 45 minutes each. My neighborhood was not unique in this situation.

The whining in the paper the next day were mostly tales of the Christmas Turkey taking all day to cook (if it finished cooking at all) and homes getting cold. But if it had been during the middle of a work week, it would have been much different. FPL did not announce when the blackouts would affect various areas. I wouldn't have wanted to be in heavy, rush hour traffic when the plug was pulled. Or on an elevator, or halfway through ringing up a weeks worth of groceries for that matter.

I hope that if we do have planned blackouts, the electric companies will be a little more forthcoming that FPL was. It's a lot easier to plan around a known event, then being caught offguard with your turkey in the oven...lol.

-- Anonymous, February 14, 1999