So, how did YOUR day start?
Diddy-bopping down the road on the way to work this morning, I’m just past the half-way point on my eighteen mile drive and the cellphone rings. I recognize that it’s a call from a work number, but I don’t recognize whose number it is.
Me: “Hi! This is me! what’s going on?
Him: “This is Fred (not really, but you know…). You know that if I call you this early, it’s not anything good.
The guy on the other end is the operations director for our little plant. He’s not one of my “I just called to shoot the bull” buddies, so he’s right. It’s probably something bad.
Him: “Are you in town today?”
Me: “Yeah. I can give you about an eight-minute ETA to the office. Why? Is there a problem?”
Him: “Yeah. There was a fire in the big utility company substation.”
Okay. That substation is there for one reason only: US. It has four transformers. We use all of them. Now I’m concerned.
Me: “What kind of fire?”
I know the substation. Nothing in there burns EXCEPT the thousands of gallons of oil filling those transformers. This isn’t sounding good at all. But he did say “was a fire” instead of “is a fire”.
Me: “Do we know what burned?”
Him: “The transformer farthest to the east.”
Me; “That one feeds the expansion project.”
Him: “Drive by there and see if you can get a look.”
Me: “I’ll do better than that. I’ll walk in and see what’s going on. I used to work with those people.”
And so that’s what I did. The substation is directly across the road from my office. I pulled up off the driveway into the substation, grabbed my hard hat, and got out. I immediately recognized several of the utility company people already there, former co-workers. The firefighters were still hosing down the failed transformer, but they stopped and started rolling up hoses.
I walked around the scene surveying damage and looking for the precipitating event. Here’s the overview:
Clickus for biggus.
And another.
It’s sad little thing. for those who like to know such things, this is (was) a 230 kV-34.5 kV, 50 MVA transformer. That’s enough power for a good-sized town.
Looking at the damages caused by the blast, it appears that a high voltage bushing failed. Bushings are the things that allow us to get high voltages into steel boxes without (usually) any sparks. This one appears to have failed. When this happens in this situation, millions of watts of energy are suddenly released, in this case inside the confines of the bushing. The case of the bushing is porcelain over an inch thick. It shattered just as well as if it had been packed with black powder explosive, throwing pieces at high velocities. These pieces shredded everything in the vicinity. I found porcelain pieces fifty yards away from the transformer, like this one:
How would you like that one bouncing off your punkin head?
Here is a close-up view of the high voltage bushings. The one that **I** think failed is in the middle, showing its foil layers. It apparently blew up in the general direction of the one on the left. the porcelain on the left bushing just fell straight down on top of the transformer. The bushing on the right appears intact but smoked up. You can see the high voltage cable on the top of the right bushing. The same cable is blown off the center bushing.
Anyway, it’s pretty much a big mess, but it’s not MY mess. It belongs to the power company, and I doubt that they’ll have this one replaced in six months. They don’t keep these things on a shelf somewhere. If you call in an order today, you’ll be doing good to get one in six months. So we’ll see what happens.
Fortunately we engineered the power system to where this transformer’s sister will be able to carry the entire plant load by itself, but now I’m wondering. You see, these rolled out of the same plant at the same time. I’m hoping this little hoo-hoo was just a fluke, but now I have something to think about…
Hopefully the company has insurance for such things. Or warranties. I get the impression that these things are NOT cheap.
I’m pretty sure it only takes a scratch on one of those bushings to make that happen. Used to drive me crazy when the linemen would toss them into a crate to return to the storeroom, because unless they were scratched, obsolete, or in someway compromised, they’d get used over and over again. They arrive new packed in all kinds of comfy materials.
Once you let the smoke out of one of those, you’ve really got problems!
Is it too badly damaged to repair/rewind? Most of that looks like cosmetic damage, unless the bushing failure caused enough fault current to shift the transformer windings. (IOW: “That’ll buff out!”) A new 50MVA transformer must still be running 27+ weeks delivery.
I watched the process of placing one of those critters into a new substation. It involved a few step, with the most notable being building a railroad spur to the substation.
Is there any possibility lightning had something to do with this?
Matt– The utility company says the transformer is under warranty
Scarlett– They’re actually pretty hardy as long as they’re treated right. You seem to know some of the tricks with them. This thing has been in service for a year, so it’s sort of a surprise.
Kevin– it depends on the integrity of the bottom of the bushing. If it popped and let combustion and fault byproducts into the windings, it’s very hard to get them clean. Relays operated and the fault cleared in 3 cycles. I’m thinking that the windings didn’t see a lot of current. You’re right about the time frame. If we expedite, it’s six months.
Jess– Yeah, they’re a pretty big deal to install or to disassemble for moving. We have a railway spur nearby and they can truck it the short distance to the substation. I don’t blame lightning unless it weakened the insulation. There were no active storms this morning but we had a couple of good ones in the last couple of days.
MC
I used see a large spare insulator everyday outside my trailer at a nuke construction site. It was a pretty thing. Never found out why it was sitting there, on a stand in the open, all by itself.
A few years ago I was about to turn in one night when the lights went out, then came back on. Looked to be a fault that cleared on a reclose. It was a very windy night.
The next day I asked one of the local elec techs about it. The wind blew a MYLAR BALLOON between the 12 kv bushings of the transformer at the local substation, just so happens I’m on that circuit.
The pictures were impressive, blew the crap out of the bushings, I’m surprised it reclosed and stayed. When they saw the damage they took the transformer off line.
Talk about memories…
My old man was in management w/ local power company (Transmission & Substation) {I was honored with his Westinghouse Relay School pencil} — he got calls in the middle of the night “The transformer blew up”. The calming question was “Is the fire out?” because most were just oil burps or overpressure when small tubs would open up. He always hated having to run the oil-dryer… Another good lesson w/ his interns was how many tankers to STORE the oil versus HAUL the oil. In the dark ages, Westinghouse documented his procedure for swapping pumps out on live (large) tubs, too, they swore it couldn’t be done until they watched his crews do it.
Hope your sweetie’s as calm as my mom (she always answered the phone — often dealt with the problem and they didn’t even bother the old man, or she told them who to call)!
Glad nobody was in range — hope the tank integrity wasn’t violated and it gets back in service ASAP!