Like a bird on a wire......

A little more about me. Since 2005 I've been flying MD-500's for a company which contracts for power companies across the country. In that capacity I have conducted numerous types of jobs which require different and increasingly demanding skill sets. This company offers services to the large utilities which provide the extreme high voltage (EHV) high tension, electrical transmission lines. Power transmission lines begin at 69,000 volts (69kv) and increase to 765,000 volts (765kv).

Your home is energized from the local distribution grid which has voltages from 440 volts to about 34,500 volts. The power pole outside your house probably has a transformer which is dropping voltage from the 1, 2 or 3 phases of a 13,500 volt line running down your street. Those local distribution lines connect to progressively larger voltage substations, fed by progressively larger power transmission lines.

Huge substations and line taps literally connect the entire United States power distribution grid into a single system. All power added to the grid, by any type of generation system, is basically available instantly throughout the entire system, at the speed of light, minus resistance and adjustments made at substations, which maintain constant voltage and prevent surges and blackouts.

The country is crisscrossed by power line structures which hold the massive 3 phase conductors safely off the ground, away from each other, and other nearby lines.The phases may never contact each other, or the ground, or there will be a failure. Every power line has a minimum distance that can be encroached upon before it will literally arc, and go to ground. 115,000 volt lines must have 3' of clearance. 14' of clearance is needed for 765,000 volt lines.

So, if a tree falls on the line, or if an insulator failed and the wires broke those clearances between themselves or each other, a massive thermal explosion will result. Anyone in the electrical path of any transmission line that has gone phase to ground will be literally blown up by the energy. Anyone nearby will be vaporized by the thermal energy of the flash alone. Anyone not vaporized will be severely burned beyond recovery, etc, etc.

These structures also have the ability to ground lightning, and to ground potential energy induced into them by the very wires they are insulting from the ground. Two parallel wires, called static, (or shield) wires run well above the conductors, and are not insulted. They are connected directly to the structure and the structure is grounded. So, the structure itself is the ground. The earth produces a magnetic field which can induce voltage into any insulated system. Solar flares from sunspots, and coronal mass ejections from the sun, can do the same. That's why they talk about solar weather and its impact on power grids and satellites.

A new pilot may conduct a forestry patrol in the helicopter. He would fly along at 40 knots or so while a forester makes notes of vegetation. Later he may progress to detailed visual inspection work in which he hovers 50-100' from every structure, for a few minutes,, while a crew on board conducts a recon of the structure hardware and condition.

After acquiring a few skills, and greater proficiency with the helicopter, the pilot will progress to actual transmission line maintenance. A helicopter can be used to drop lineman off at the top of a structure. It can be used to conduct work upon the structure, and it can be used to work on the power line itself. Wait, what? Really? How is that possible, you ask? There are two distinct and different techniques for this.

The helicopter can be bonded directly to the structure, by grounding it to the structure. You would think that because the structure is already grounded that no bonding is necessary. You'd be wrong. The helicopter carries a potential voltage just by flying through air, essentially insulated from the ground. Ask any ground man who had received a long line hook from a helicopter, and been knocked to his knees, whether or not a helicopter can pick up static electricity. The structure also carries massive potential voltages induced upon it by the wires it carries, so binding is required. These voltages are not lethal but could cause burns and if the crewman was not wearing his steel mesh suit, its possible to create a path which could stop the human heart.

The helicopter can also bond directly to the energized wires, with a couple of major caveats. One; no part of the helicopter may break electrical clearance to another phase or the ground (or structure) Two; everyone on board must wear the steel mesh suit, to ensure the potential energy flows around your body, and not through it. Tests have been conducted where a running helicopter has been energized to 1 million volts. So, essentially, after equalizing potential with the wires, the helicopter has become energized to the same voltage as wires and can be considered an extension of them. So the helicopter can never become the path to the ground or another phase. Instant death and the destruction of the helicopter is the result of breaking clearances.

From time to time I will post pictures of this type of work. I will also write a few stories about things that have happened that I find quite humorous, but required a bit of a tutorial about how this all works and why. So, I apologize for the text book explanation but it helps you get the good stuff later.

See the Youtube link for some interesting power line stuff.  http://www.youtube.com/watch?v=r_1T2_l43Xo
The video is my former company doing a movie...The guy on the platform is a dude named Spider. There are many you tube videos about some of the things I talked about here.....