Fair Winds and Following Seas Mr. Armstrong

So as many of you probably know Neil Armstrong passed away recently.  While it certainly is a blow, it is by no means unexpected:

I am by no means old enough to remember Neil Armstrong and Buzz Aldrin’s historic walk.  I was however lucky enough to grow up being the son of an engineer.  One of my father’s good friends worked on the Apollo program.  I will say I’m not a big fan of NASA, but I will not allow my dislike of them to taint or color the value and accomplishment of the Apollo program.

Growing up I looked at Apollo and it meant one thing to me, if I can dream it, I can build it.*  Hence my becoming an engineer.

I want to see us return in my life time.  But everyone in that program can take solace in the fact they helped inspire a bunch of people to become engineers.  No just at that time, but continuing forward even today.

So pardon me while I go give a wink at the moon.

Good bye Neil and God Speed.


*It is worth noting what sealed my decision to be an engineer was seeing the development of the Physio Control Life Pack as well as the Automatic External Defibrillator.  The fact I saw something my dad and his friends built from the ground up that at the time only had the potential to save lives and revolutionize everything.  Yup, it did exactly that.  The Apollo program’s impact though was no slouch either.

Electricity is Dangerous….

Weer’d had an incident recently in his “Gun Death?” files that centered around a downed power line.

There, she saw a white SUV on the grass of a house. Water spewed from the broken hydrant – about 2,000 gallons per minute – and downed power lines carrying a charge of 4,800 volts lay along the ground, charging the water around the exposed wires.

Most people understand that electricity is dangerous but often they don’t understand how dangerous.  I started the power series and I keep meaning to go back and continue it, and one of these days I will.  For now though I’m going to try and explain just the specifics to try and help people understand what is going on.

To start off with, if you are in a vehicle and it strikes a power pole or a power distribution box.  Stay In Your Vehicle!  Your vehicle will actually help protect you from the voltages.  If you can, back away from the downed conductors and then call 911. In the incident of hitting a power distribution box, odds are the line will fault and a breaker will open.  However, be advised that doesn’t mean your safe.  The majority of faults in the distribution system are momentary.  Because of this fact there is an auto reclosing circuit which will reclose the line and energize it.  The fault will remain and the circuit will open again.  Usually after the 3rd shot failed they will lock out the re-closer.  Still, stay in your vehicle, don’t risk it unless there is a more pressing danger to your life such as a vehicle fire.  If you do need to leave your vehicle, use my notes at the bottom.

Now, if you see someone get in an accident with a power pole or distribution box, keep your distance!  If you see the line arching or sparking, keep your distance as much as possible.  Immediately call the utility and they can de-energize the lines.  While the power company wishes to clear faults when they occur on the power system there is a particular kind of fault that is very hard to detect.  Not only is it hard to detect, but it becomes exceedingly difficult when you’re in the distribution system.

Detecting this fault is difficult because there is not a lot of current involved which is one of the big items that is watched for protection.  The reason there is less fault current, especially at the distribution level is the distance from generation and the fact it is in parallel with numerous other loads.  Especially the further you get down a distribution line.

What is confusing in this case is the combination with water with the fault.  Normally high impedance faults are found on things like asphalt or in the desert on dry sand.  Where the ground itself isn’t a good conductor.  In this case water is an excellent conductor, however I suspect that the water was mainly on asphalt which was acting as an insulator and this fault was way down the distribution line.

So here’s basically what I figure happened.  When the line went into the water, all the water was basically at a potential of 4800 volts.  The water would have a low impedance so there wouldn’t be much of a voltage drop across it.  However, there is a massive drop between the water and the actual earth ground.  As someone stepped into the water they bridged a circuit with their body, especially if they stepped off of grass over a curb into the water.

Your body and electricity don’t really mix.  It takes only a mere 11mA to stop your heart, it isn’t voltage that kills you, it’s the current.  Your bodies natural resistance tops out at around 100 kilo ohms at the skin, if it’s dry and you’re not sweating.  Internally it’s only about 300-1000 ohms.  If you get your skin wet the resistance drops.

With dry skin if you were to grab on to a 4800V line you would get 48mA through your body approximately, that would be more than enough to kill you, though that would depend on the exact path taken through the body.  Wet, the current will be easily measured in Amps.  If some how it doesn’t stop your heart, odds are you will be lit on fire as your body will be dissipating approximately 27 kW of energy.

So everyone please listen to me, stay away from downed conductors.  Yes people may be injured, people may need help, but it will do no good for them for you to injure yourself in the process.  In fact it will divert resources from helping them to helping you.

Now if some how you find yourself near a downed conductor, do not walk towards it or away from it!  Do the following:

  • Keep both feet as close together as possible.  This will keep your feet at approximately the same electrical potential and will limit current flow.
  • Hop both with both feet away from the downed conductor.  Again, do not walk.  At most shuffle.  See there’s a reason they made you learn the bunny hop in PE in school!
  • If you need to exit a car.  Jump clear of the vehicle without touching the vehicle and the ground at the same time.
  • Keep your arms held tightly to your sides.

The explanation of this is think of the ground as a high impedance resistor.  Over a resistor is a voltage drop.  The further the distance on the ground from one point to another the bigger the voltage drop.  Your body has a much lower resistance than the ground, and if you step, that difference in potential will form a circuit through your body.  If you are not comfortable hopping, then shuffle away.

The Correct Statement Regarding Most Things in the Real World…

I’ve been in internal training this week and will be for the remainder of the week.  Now while this is listed as “internal” training, it’s merely a class dedicated to company employees for this presentation.  Normally this class is given to our customers and people who use our products in the power system.

I got home tonight and saw the following on twitter and proceeded to laugh hysterically.


Now you may not know why I started laughing hysterically so let me explain.  You see 99.9% of the time when there is a question involving protection on a power system the correct answer begins with the following statement.

Well that depends…

For instance when protecting a transmission line, the type of protection used will depend specifically on the characteristics of the system involved.  Numerous assumptions must be made in order to create the correct solution.

In this case, the number of bullets required to stop an assailant, the correct answer is, “well that depends…”

  • What caliber was the assailant shot with?
  • What type of bullet were they shot with?
  • Where did the bullet strike the assailant?

All of these are critical for determining the number of shots required.  If it always took 2-3 shots, I doubt the .22 LR would kills as many people as it does merely by accidental discharge.  The fact is a lot of the lethality of a bullet is whether or not it connects with a major blood supply source or organ.  Penetration is what determines if a bullet is able to achieve access to a lethal area.

So, the correct answer regarding the number of shots to take down an attacker is, “It depends”.  And honestly, when it comes to modern pistol cartridges, the arguments are mainly pointless.

Now That’s Awesome

This can best be summarized as, “Because you CAN!”

Here’s his whole run from Pikes Peak in 2011.

That man has serious balls, especially when there are incidents like this have happened on the same course:

h/t to Ry on that last video.

Today has been one of those days…

Yup, I still have it.  It’s so nice when I can take one look at something and fix it without even really thinking about it.

We Need More Power!

So, we had a unique power source for field day.  A hydrogen fuel cell.


There’s a bank of lead acid deep cycle batteries under the fuel cell.  The cell basically acts as a battery tender charging the batteries and supporting the load while it is on and then turning back off when the batteries are full.


We ran a 48V DC bus (see the extension cord coming out on the left) ran that back into the communications trailer.  This decreased the I2R losses (see also here for info) from the longer cable run.  Within the trailer was a DC to DC converter that put out 13.8V for all of our communications equipment and we also had adapters to run our laptops and other equipment.


It actually was quite effective and we started with an “empty” tank and still ran for over 8 hours on it.  The calculations are we could run for over 48 hours on a single tank of hydrogen.  The cell its self has a rating of 1KW and we actually did get it up that high, however I didn’t get a picture of it.  The fuel cell was running like mad because we left it off after out thunderstorm to let things dry out.

In the mean time we kicked back into operational mode meaning 2 radios fired back up plus their associated computers and associated equipment for digital operation.  All just running off the batteries without the Fuel Cell maintaining them when necessary.

Our clue to go turn the cell back on was when the low battery alarm went off in the trailer indicating the 48V supply was starting to drop.  We did also have a 12V batter on the other side of the 48V to 12V converter in the trailer.  This was to add extra isolation for surging loads (radios).


The fuel cell worked great and was always fun when someone would brag about running off of solar.  Yeah, well we’ve harnessed the power of molecular bonds!

For those who don’t know how fuel cells work, the basic premise is that the electron from hydrogen is forced through the circuit as the proton mates with the oxygen to form water.

Now some would call this a wonderfully green technology, however that hydrogen has to come from somewhere, and most often than not it’s through electrolysis.


*Also as an aside since the wife and I were just talking about it.  If you’re a ham, do not use the term kilo-watt for phonetics.  The word you’re looking for is kilo.  Kilo-watt is very confusing because it is a compound word.  Are you saying K or KW?  Other’s do use the term watt for W, which while incorrect can further add to confusion.  Seriously, the IACO/NATO/ITU phonetic alphabet was developed specifically to limit confusion.  If your word choices were so great, why haven’t they adopted them?

You may think it’s neat and cute, but at least in the case of the wife and I, we slow way down to deal with your choice of phonetics.  I am reasonably sure that I am not the only one who has been confused by this usage.  It’s hard enough to dig phone messages out of the weeds, why add a bit of extra confusion to the conversation.  But that’s just my two cents, take it for what its worth.

We Interrupt Your Regularly Scheduled Program…

So we had a minor hiccup with field day.  Our station is currently off-line and we are sitting in the trailer chit chatting.

Now why would we all move inside?  Well this doesn’t fully show what’s wrong but probably gives you a solid idea of what’s wrong.

It was making loud noises and flashing through the sky.  It just recently stopped hailing.  We disconnected everything and lowered the stepper antenna for safety.  We’re just now slowly starting the system back up.

So this interruption was brought to you by mother nature and we are now returning back to our regularly scheduled program.

CQ Field Day

I’m spending the day doing field day with the local ham radio club.  We actually have a hydrogen fuel cell that we’re running all our radios off of.  We spent a chunk of the morning hooking and setting up antennas including a nice Stepper IR that was donated for use during field day.


It took us a lot longer than expected to set that bad boy up.  We were having SWR problems and we’ve been trying to debug the issue.  First up was checking all the connections and we discovered this in one of the connections.


That however wasn’t the problem.  The SWR was still way above 3.  What else could be the problem.  Well we bypassed the 80m tuning coil and bang, SWR dropped to 1.  I think we found the problem.  At that point it was time to grab some lunch and now I’m working on logging while my compatriot runs the radio.


I’ll be busy until late tonight.  If you’re a fellow ham and you hear KD7PH, feel free to send a shout out. We’re going to start running some of the digital modes here in a bit but were running phone now.

It is nice being able to run that Stepper IR thought anywhere between 40m and 10m.  We haven’t tried running 80m since we pulled the coil but so far if we can hear them we can work them.  All running just measly 100 watts.

We just bumped to 15 meters to see how things will run for now.  I have to say I would like to get one of those for my house, the thought of the cost though doesn’t have me running to buy one

It is nice being able to do all this in an air-conditioned trailer.  Even though storms rolled in, the heat’s still pretty high and the humidity has gone up.  It’s going to be a fun day.