And Now, More Wind!

Continuing from where I left off after Why wind power is not the (only) answer . . . .

Earlier today I was thinking about where I would go when I came back to the topic of energy future stuff. Then I heard about another new wind farm just approved for construction, over on the west coast.

Hearing about new wind farms is not unusual, but this announcement was a big deal because of its size. Apparently, this new facility will have a capacity of 845MW, which is substantial even by large coal and hydro plant standards. Let me clarify it further: When completed, this new project will reportedly be the largest single wind farm installation in the world, according to its Wikipedia entry.

These things are scary deals for dispatchers. 845MW is about on par with a nuclear plant's output (a point not lost on whoever wrote the announcement I saw), that is a lot of MWs to come from a single location.

The greenies are probably pretty happy about this. And there is no doubt that when those 845MWs are being generated, there will be less MWs coming from pollution-producing plants, so its not all bad.

But folks, it's just not that simple.

If you recall from earlier tutorial posts, there are three major AC interconnections in North America: Eastern (gigantic), Western (fairly big), and Texas (diminutive). The stability of an interconnection is relative to its size in terms of generation capacity and load. The loss of 1,000MW barely causes a burp in the east, while in the west that same loss sets off a few dispatch center alarms and wakes people up. In Texas, the loss of 1,000MW will shake the dust off the rafters and maybe crack a window or two, so to speak.

Texas is where I am going with this. Texas produces more wind power than any other state, with nearly 9,500MW of installed wind capacity. Iowa is a distant second with a little more than 3,500MW installed. But Iowa is in the rock-solid eastern grid. It isn't accurate or relevant to compare wind power by state, anyway, since power grids are not impressed or influenced by state boundaries, right? It has to be done by interconnection.

Presently, the eastern interconnection has about 17,500MW of installed wind power. The western interconnection has a bit more than half that much at about 11,000MW, which is loosely proportional to its strength relative to the east. That's not much more than Texas has all by itself in its tiny little AC grid.

Good for Texas, right? Not so fast. A little over two years ago, the entire Texas grid came perilously close to blacking out. Why? Mainly, because of all of its installed wind power.

From Reuters:

Loss of wind causes Texas power grid emergency

A drop in wind generation late on Tuesday, coupled with colder weather, triggered an electric emergency that caused the Texas grid operator to cut service to some large customers, the grid agency said on Wednesday.
HOUSTON
Wed Feb 27, 2008 8:11pm EST

Electric Reliability Council of Texas (ERCOT) said a decline in wind energy production in west Texas occurred at the same time evening electric demand was building as colder temperatures moved into the state.

The grid operator went directly to the second stage of an emergency plan at 6:41 PM CST (0041 GMT), ERCOT said in a statement.

System operators curtailed power to interruptible customers to shave 1,100 megawatts of demand within 10 minutes, ERCOT said.

(read the rest)

You may not have heard about this when it happened, but it was a very big deal in power dispatcher circles, I can assure you. The article goes on to state that the output of wind power dropped from 1,700MW to 300MW in a very short time, while customer demand increased from 31,200MW to 35,500MW.

Do the math. The little Texas grid lost 1,400MW of generation even as demand increased by 4,300MW. That rapid swing knocked them out of balance by a staggering 5,700MW! Their other resources have enough work cut out for them regulating demand, but picking up that lost wind output nearly created the next big blackout story since the eastern blackout of 2003. The only thing that saved them was dumping over 1,000MW worth of customer load (blacking people out) to make up the difference that their other plants weren't able to cover.

Why did this happen? Well, forecasting wind is still a very inexact science. And even when you know where and when the wind will get you, you still have to have adequate regulation to work around it. They got burned on the forecast and for sure couldn't regulate adequately.

If you keep adding wind generation that makes MWs at the whim of the weather, your regulation demands that need to respond to the scheduled whim of the consumer will also increase to either stay out of the wind's way, or cover for it when it's gone, and eventually you will not be able to keep a decent balance with your other power plants at all. Ergo: brownouts, blackouts, and of course, egregious wear and tear on the overtaxed power plants used for regulation.

Back to today's announcement: The statement indicated that the new Oregon facility is about equal to a nuke plant. The uneducated will rejoice. That's one less nuke or two less coal plants that won't have to run or be built! Hardly. You will rarely get the full capacity from the wind farm except when you have the occasional high sustained winds, and you already know that those high winds aren't going to make appointments to only show up when energy grid demand is high. You'll still need power from somewhere else when the wind is not blowing. So, announcement writers who are supposed to be unbiased: Don't imply it is "equal to a nuclear power plant", because it is anything but.

I'm sure you all get it by now. Wind power is a great source of instability on the AC grid. I'll stop beating that drum so much going forward. Next time I talk about future energy, I'll try to address other renewable sources generating buzz as of late. And there's much more to come after that.

360° Walkaround Fail

You Make the Call

With my apologies to the Happy Medic's "You Make the Call" series.......

One of the many relatively important substations in your area is one which, if entirely lost, would probably dump a sizable chunk of the regional grid and make the national news.

This station has five 345kV lines, four 230kV lines, and nine 115kV lines, interconnected to each other in the yard by two 345/230kV transformers, two 230/115kV transformers, and one 345/115kV transformer. It serves no load directly, but is a major waypoint for very large amounts of bulk power going to important places.

During a routine inspection about nine months ago, the 345/115kV transformer was found to have elevated and near-dangerous levels of combustible gas forming in its interior.

(A $0.02 explanation of a transformer: Major substation transformers are roughly the size of a small delivery truck, and contain a large iron ring around which coils of wire are wrapped, with differing numbers of coils on each side in proportion to the voltage change. The coil and windings are immersed in cooling oil.)

Since the 345/115 bank was producing combustible gas, the dispatcher had it immediately removed from service and electrically isolated by opening the switches to it on both sides.

Experts and technicians were called in to do extensive testing on the transformer. Replacing it would cost around $2 million for a new unit plus labor costs, so repair is by far the preferred alternative. After months of study, they cannot determine for sure why it was producing the gas. The transformer was flushed, inspected thoroughly again, and filled with new clean oil.

Two days ago, the district manager arranged to have the transformer energized from one side only (no energy flow through it) to test it again. It was energized for most of a day. One of the substation operators there reported that the transformer was making a sound similar to marbles rattling mixed with a heavy buzz. Normally transformers hum at 60Hz, but the sounds reported off this bank are not typical. Still, it closed in OK without tripping, and combustible gas tests came back with levels low enough to not raise concern, though only one day of being energized probably wouldn't yield useful results anyway.

The district manager wants to put it back in service right away, as months of maintenance on other jobs have been put off. These delays have cost substantial $$$$ in subsequent delays of other coordinated projects pre-arranged with other utilities before this all came up. Additionally, the district manager reports some of the deferred maintenance issues are becoming critical. Getting this transformer back will strengthen the area grid enough to resume all of those postponed jobs.

The maintenance planning desk has approved the return-to-service procedure and it has landed on your dispatch desk, scheduled for today on your shift.

Do you do the job? Ask for additional testing? Refuse the job? Any special precautions?

You make the call.

Despite the Best Made Plans

We were bouncing reminisces of epic power company failures around recently, and keeping with the Happy Medic's Rule of Threes, I will share with you the three that stuck out as worth passing along. Unlike HM's threes, though, my stories often go too long, so you only get one tonight.

Now, it should be recognized that lots of stuff goes wrong all the time, of course, but we usually can play by the seat of our pants and get out of it without many people knowing. That's the whole point of why we're here and what we get paid for doing. But heaven help the dispatcher on the desk when the stars align, whether its his fault or not, because big fun ensues.

Episode 1: When "Preferred" is not Preferable

A 69kV subtransmission loop had a fairly good-sized community fed off of the end of one side next to the normal open switch that kept the loop from being tied through. If you've been reading here for a while, you remember that normal-open loops are good, because a fault anywhere in the loop only takes out half of it instead of the whole thing, and once you find and isolate the problem, you can serve the customers on the remote end of the bad section from the other side until affairs are settled.

Problem was, in this case, the entire loop was fed through some rough terrain and there were frequent outages, relatively speaking. Each time the thing tripped, it would take a few hours to find the problem and then switch in the city from the other side. The city was a pretty squeaky wheel, and eventually pushed us to install an automatic throwover switch.

An auto throwover switch is actually two switches, mounted up on one or two power poles, and equipped with PTs (potential transformers, that detect voltage) on either side of the customer's tap. One switch is open, the other is closed on the preferred source side. If the preferred source goes dead, the PT on that side calls to the other one and says "Yo, I'm dead over here, how about you?" The other PT says "I'm fine over here, my Xbox is still on!", and the throwover switch scheme, overhearing the conversation, opens up on the dead side and then closes in on the live one, picking up the customers after just a short delay. Instead of being out hours, now the occasional interruption lasts about five seconds.

Important: a throwover switch is motor-operated, and motors require.... electricity.

The best implementation is to mount a poletop transformer right there to serve a charger for the switch's 12VDC battery.. Except in this case, someone went cheap and decided to just go with a transformer straight to an inverter to serve the 12VDC switch motors, supplying the throwover scheme right off the 69kV and saving the cost of batteries.

They put it all together, tested it, works great. Now we just have to wait for the next outage and show those guys how cool this is!

Within a few weeks, a storm blew through, and the preferred side faulted as reliably as ever. The guy on duty pulled up the customer's substation display on screen to observe when the feeders picked up again upon the throwover executing its beauty. Nothing. Waiting.... tick tick tick, still nothing. Of course, you saw this coming, right? The engineer designed the throwover to be fed off the preferred side (after all, it was preferred). When the preferred side went dead, the PTs would have liked to have had their discussion abotu who still had a working Xbox, but the switch motors had no power and were helpless to throw.

Oops. Two hours out. Again.

The next day the throwover source was moved to the alternate side, and a few months later, it also got batteries like it should have had in the first place.

Watch for Episode 2: The Important Sign in a week or so. Episode 3 involves a backup generator at a power plant, but I haven't thought up even a bad name for it yet.

Keeping It Real

Just minding my own business, hobnobbing through the Station 53 area, when the tones dropped for a medical fairly close to my location.

When I'm not on a shift, I don't just jump every call, because the duty crews generally have enough help along, but this was a COPD patient with difficulty breathing or speaking. Don't have to think twice, as in my location I'll be first in and can start getting the ducks aligned before the cavalry arrives.

It's a pretty routine call, really. The guy is not in great shape, but he's not circling the drain just yet, either. I don't carry a full med kit in my car (though I probably should since I do drop in now and then), but I'm not doing any procedures that create an exposure situation. I mean, common sense here.... if I met the guy on the street, I would not put on gloves to shake his hand. I'm just writing down information and getting the most basic of vitals.

Engine 53 arrives with more help than I expected. Three cadets are along for the ride. Fresh, a little uneasy, but wanting to be in it. Remember that feeling?

I let the E53 guys move in and take over while I rattle off the patient info and high points that I've gathered, and take up a position by the cadets. I like teaching, keeping them involved. Any time I get asked to do something, I walk one of them through it. When Medic 97 arrives, I take a cadet out to the ambulance to show him how to remove the cot, lower the wheels, lift the hook. It's all new to him. I make him do it all so it is hands on.

I like teaching. I like feeling confident, in the know, and showing the new guys how its done.

Back inside, I am asked to get a blood sugar reading. I grab the glucoscan kit, and am twisting off the lancet cover, when the captain taps me on the shoulder.

Gloves, he says, eyebrows up.

Holy crap. I was totally in tunnel vision, and never grabbed gloves when the guys arrived. I know better. I sheepishly hand the kit to the next guy and step aside to get gloves on.

One of the medics asks me to change out the cannula, and go high flow. I grab the NRB, hook it up, check the LPM and go to place the mask.

Holy crap. I grabbed a ped mask and didn't check it. The medic gives me a look. I get another mask. I know better.

We get the patient on the cot and head outside. I see my truck with the flashers on, positioned to be visible from the road to draw in the other units. The Medic is really close to me.

Holy crap, I nearly blocked their good access. I am constantly riding people about making sure to leave lots of room for the ambulance to get in and out. They managed, but my truck could have been spotted a lot better.

I like teaching. I like teaching the new guys what to do. Well, they learned some things today. I cashed in a few too many examples of how NOT to do things.

Didn't affect patient care, but it's good to get a little smackdown on your confidence to remind you of things now and then.

I was due, apparently. All that confident, self-righteous power dispatcher attitude is hard to swallow back down. Keeping it real reminds me that I am not all that and a bag of chips, either.