Two Men Electrocuted In KCK

[Wrightwood]

This article and email are worth taking a look at as a reminder of safety precautions that must be observed when working with antennas.

http://www.kmbc.com/news/16871003/detail.html

We lost another ham today, and it is a very sad event. The parties involved, were installing a Comet FIBERGLASS antenna, that came in contact with a single 7620V power line. Now how do I know what the exact voltage is? I built and maintained the substation that fed this circuit. I spent 27 yrears as a substaion technician for the Board of Public Utilities. I am still in this field. So, I feel I have some experience in what I am passing along.

In a nutshell, the location of the accident was a few blocks from the substation. The wires you see going thru the residential areas are AT MINUMUM 7200 volts from each wire to ground, and between any two of them is 13,800 volts. This is nothing to play with at any time. I have seen a fault TOTALLY vaporize 1" copper buss (which is solid). Imagine what it can do to a human.

Each wire is fed from what is called a 3 phase line. From there, it can be broken off and sent down a property line as a single wire. Those are called "laterals" Yes, you will see a device at the break out point, and this is a fuse. BUT the caution needs to be conveyed. These fuses are in the 60-100 amp range. This is at 7200 volts. On top of that, anytime a tree falls across a line, or a pole gets hit, there is a circuit on the "feeder" at the substaion that AUTOMATICALLY closes the fedder back in, and TRIES to restore the power to the area. Some of these "reclosers" can operate 2-5 times, depending on how they are set. Now from the substaion end, the protective device is set for the full fault capabilites of the line. In the case of BPU, this can be set at 600 AMPS, and multiples of that value. The protective devices are set for what is called a "time" or and "instantaneous" operation. Picture a fast blow fuse and a slow blow, and you will understand the difference in the settings. These setting are at multiple of the 600 amp value. So, if there is a direct short, then it will not trip until it reaches a value at, oh lets say, 8 times that value. So we are looking at 4800 amps. and this is at 7200 volts and lower. So, it trips, then it energizes it AGAIN. The possiblity of survival is slim and none.

Now remember how I said they were installing a FIBERGLASS antenna? Well guess what. It is metal inside. Yes, fiberglass does not radiate as we all know. Hence the metal. That is what caused the accident. They got too close to the line (remember your 'magnetic lines of flux' theory? If not, look it up on the web). There is a minimum approach area that MUST be followed. This changes for ALL voltages. This distance must NOT be broken. If it is a flashover will happen, and it is not pretty. Electricity will find the shortest path to ground. In this case it was a couple of men.

Folks, this is nothing to take chances with. In my almost 30 yrs as a ham, and 27 yrs in the power utility field, I have seen way too many "accidents." Stop, look and if it is close or SEEMS that way- DON'T. Find another place. High voltage lines are NOT forgiving. Your life depends on it. You always hear "it is the amps not the volts" well I can tell you when you get at these levels, who is going to argue what killed the person who had the accident. PLEASE ,PLEASE follow the warnings. ANYWHERE close is too close.

Stay safe, and I hope we can enjoy many more years of hamming.

Thanks Guys,
Chuck Kraly, K0XM

[kew]

Isn't there a minimum distance from a power line that must be observed when putting up an antenna or have I forgotten every thing you're supposed to know to be a Ham?

[Calindy]

People get too comfortable about their surroundings. One of my worst Paramedic runs was in the late 70's. Some painters were painting a church and when moving their scaffolding they hit the power lines. Three were dead when we got there (with their shoes blown off) and the other one was alive but VERY, VERY combative. It was in Indiana, and I was alone in the back of the ambulance (volunteer FD on scene, no men (or women to spare, it was a weekday), so I grabbed the two biggest guys there to go with me and the patient to the hospital. I will NEVER forget that scene, seeing those men lying under that huge cross on the church. We then had to make sure the scene was safe before we could go and help. Those men knew the power lines were there, they just got comfortable or were in a hurry, I am not sure. You can train and train people, but these tragic accidents will always happen. However, the more education, the better. It kinda reminds me of the people who try to beat a train (last week 3 people died doing that where my sister lives), I am pretty sure they knew better. Very sad and unnecessary...I feel for the people left behind.   

[tiltronix]

"Yes, fiberglass does not radiate as we all know."  There are dielectric antennas which focus radio energy.  Not used much in the lower frequencies, however not a bad radiator in the microwave spectrum.  It is not a good 60 Hz conductor!!!!

[clint]

Ken,

there is no minimum distance regulated anywhere in feet. The guideline is, the antenna system, that's the mast or tower and antenna at full height, should be far enough away from power lines that if it fell over it would not come in contact with the lines. In practicality if you live in an urban environment and have a real antenna put up it's difficult to do.

[kew]

The guideline is, the antenna system, that's the mast or tower and antenna at full height, should be far enough away from power lines that if it fell over it would not come in contact with the lines.

My point exactly. Since they were installing a fiberglass antenna, which is typically short, (6' or less) they had to be dangerously close to the power lines no matter the reason for being on the roof.

[clint]

There are plenty of fiberglass encased (called a radome) antennas much longer than 6'.