Glad you asked.

700 miles on the car this week.

Tuesday I slid down to a station deep in Cajun country to help a new technician with the task of swapping out a bad battery on his station UPS.  It’s like the little UPS you can buy for your computer – ties to the utility power and if the utility drops, it provides power for whatever’s plugged into it.

In our case, the station control system and safety systems are plugged into it.

Ours is a little bigger.  Here’s the battery we took out.

That’s an Exide FTC-21P.  Two volts, 1680(!) amp-hours, 303 pounds.  Our UPS has twelve of ’em, like this:

Twenty-four volts, feeds to the station inverter and will carry everything we need for twelve hours.

We hope we don’t need it to run off the batteries that long, because when the utility power stops, we automatically start the station generator, which can carry the entire station until it breaks.  It’s fueled by natural gas, something we have inexhaustible amounts of.

this is it – 150 KW.  Waukesha engine, KATO generator, three-phase 480 volts out.  We had it down for annual maintenance when i was there:

As MY generators go, this is a smaller one.

Next day, off to a site north of Houston.

Batteries?  The tech there is testing his.  His bank has 60 two-volt cells.  This test setup monitors the voltage of EACH cell while a load is applied, watching for the first of the sixty to drop below 1.75 volts.  How long this takes is compared to the manufacturer specification, and if we’re 80% or less, we’re getting a new bank.  Why not just the bad cell?  They’re ALL the same age.  Critical equipment.  We won’t press our luck.

It’s routine for us, but ‘routine’ around electricity means there are many dangers involved.  We practice safe work habits.  One is that you don’t wear jewelry when working around electricity.   This is why:

There!  Aren’t you glad you asked?

Transformer died almost a month and a half ago. We had a lot of fun locating a somewhat adequate rental unit, due to the station’s designers choosing an oddball voltage – 6900 volts, for the station’s power system. We finally located ONE, but it’s only 2/3 the capacity of the dead one. Still, 2/3 of a transformer is better than no transformer at all.

So the next step is to get the old transformer out of the way and off to the shop in Minnesota. first we have to prep it for travel. That means removing a lot of external things like bushings and radiators. Here’s a ‘before’ picture:

And an ‘after’:

Remainder of the story is below the fold: Continue reading Take me away… →

Here’s the transformer I’m whining about. The high voltage leads are disconnected from the bushings on top for testing, as are the low voltage (4160 volts) you see in the compartment on the side.

Clicking gets you the full sized version.

Not me.  I mean that poor transformer I talked about yesterday.

This morning I was on the road to a little station in the East Texas Piney Woods.  There I met a tech who knew how to get to a remote station that is so far back in the woods that they can’t get commercial power.  They self-generate, and the two generators we OWN there are dead.  They’re using a rental and they need a new, permanent installation.  I got pictures and data.  Gonna be fun at the office tomorrow.

Following that trip, I swung south to the station with the tripped transformer.

If I’ve tested one transformer in my life, I’ve done several hundred, and this one I knew to be bad.  We had to have test data to prove it.  A testing contractor sent out some technicians and some expensive test equipment.  They were working when I got there, but before I showed up, one of them had pulled samples of the transformer’s oil.

Oil?  Yes, most of those big square tanks are filled with oil, a highly refined, pure hydrocarbon oil roughly the same as diesel fuel.  As a matter of fact, diesel engines will run quite well on it.

the oil’s in there for two reasons – cooling and insulation, and it fills the tank almost to the top.  On my transformer, as is that case with many of them, the space in the tank that’s not filled with oil is filled with nitrogen.

Flammable?  The oil IS mildly flammable – like diesel fuel, but there’s no oxygen – remember that nitrogen?  and temperatures of a transformer do not normally get anywhere near the ignition point.

Stuff happens, though.  Somewhere along about the wee hours of Sunday morning, the 138,000 volts inside the tank found a way out of its designed paths.  It faulted.  For a few cycles – seven or so, 34.5 MEGAWATTS – the power of 34,500 microwave ovens – was released inside that tank, under the oil.

My protective devices noted the fault after about three cycles and operated the circuit breakers to remove power from the transformer.  From the time the relay said ‘trip’ to the time the current stopped was three cycles –  a twentieth of a second.  During that time, the temperature of the oil, all 3572 gallons of it, rose fifty degrees C, topping out at 80 C.

If the relays and breakers had NOT cleared the fault, well…

But everything worked as designed.  Another thing about that oil – it’s a hydrocarbon and how it acts under high temperatures is a known thing.

We had a whopping big arc – lots of high temperature- in the oil, so those oil samples were rushed to a lab that specializes in analysis of the dissolved gases in the oil. The released energy takes the long hydrocarbon chains of the oil and cracks them into shorter chains, gases.  Analysis of the amount of gases found in the oil can tell us a lot about what happens inside the transformer.

This sample told us what I’d already seen from external data – big fault inside the transformer.

So it’s dead.  A year and a half old, and deader’n Hillary Clinton’s presidential hopes.

We’ll get the manufacturer to come out and pronounce a benediction and it’ll likely go away, possible for repair, maybe to make room for a replacement.  I don’t know if the manufacturer will give a root cause for the failure – they’re not on my list of favorite people – but one can hope.

0539 and I’m on the road to my station south of Houston. This one’s been running a year of so, a couple of 4500 horsepower pumps handling natural gas liquids. The tech was concerned that the protective devices on the 4160-volt power system might not have been set up properly. My goal for the day was to use a computer program to download the settings from those protective relays to my computer and do a quick analysis.

I got this act down pat. A laptop, the proper software, a serial cable and a null-modem adapter, and in an hour and a half I’m finished. I do a cursory examination of the files and conclude that the relays have been properly set. I spend a bit of time explaining a few things to the technician who ‘owns’ the site.

We have a project to tie the various protective relays into the station’s control computers so that power system parameters can be easily monitored. We discussed some of how that’s going to work. I know how my end works, and we’re hiring an eminently competent compan to do the installation. I expect no problems. Of course, it’s the same company that left the loose endss hanging that we fixed last week at another station. We’ll watch a bit closer this time.

Then it’s back on the road for a two and a half hour drive back home.

You can see interesting things running around Houston’s periphery. I saw THIS:

Well it might not have been that one, but it was one just like it, slipping in and out of view through the low overcast, landings somewhere south of the Sam Houston Parkway.