By Mike Conrad, Division Chief Operations, Aptos La Selva Fire Protection District
Yes, it looks like we will have a winter this year. Rainfall totals to date are above normal, which is a great sign. However this does not mean we are out of the woods yet with the drought but at least we are headed in the right direction. It has been awhile since we have had significant rainfall so I wanted to refresh everyone on the hazards of water soaked ground, wind, trees and power lines. So for all of our safety let’s review some do’s and don’ts of electrical emergencies.
First of all there is no need to worry about Volts, Amps or Ohms that just makes things confusing. We do need to remember that the higher up the electrical pole the wires are the more voltage they carry and these electrical wires are not like an extension cord in your home they are most often bare with no insulation. Also just because a wire is located low on the pole if it is contact with a wire from high on the pole it can still care as much danger as the wire high on the pole.
All electrical systems will have fuses and circuit breakers of different types. One such device is known as a Line Restorer. The Line restorer functions much different than a fuse or breaker, it will automatically reset several times in an attempt to restore power to that circuit. As a result of this action it is impossible to determine when a down power line may be re-energized, this is the main reason we treat all down lines as energized and we do not attempt to move them.
There are four things that we must always keep in mind when we are faced with down power lines. First is what is called Ground Gradient, this is when an energized power line comes into contact with earth. At the point of contact the ground will become energized with the same voltage as in the wire, this voltage will travel away from the point of contact much like ripples in a pond and as it get further away from the point of contact the voltage decreases. The voltage Gradient can extend for a large distance from the point of contact, the amount of voltage in the line, type of ground, moisture in the soil and humidity can all affect this distance and increase it to 100 feet or more.
So first thing to remember is the ground around the power line can be energized. The second thing to think about is what’s called touch potential. Touch potential is when items like vehicles, chain link fence or other conductive materials come in contact with an energy source. If we should happen to touch such an item we would in turn complete the electrical path and at the least be shocked and at worst be electrocuted. The third thing is Step Potential, step potential occurs when we have a ground gradient around a point of contact. If we walk into this area the difference in voltage from one leg to the other will cause a path for electricity to travel and yes that path would be through us. So always stay a safe distance from any down power line.
The forth thing that you should always keep in mind if you are considering crossing over or touching a down power line, is the reason for doing it worth your life? We see it every winter people walking or driving over power lines because they have to get home to feed the bird, or they can’t be late for work and the list goes on and on. I know that limp piece of wire lying on the ground disrupting your day looks harmless enough BUT, it has the ability to change your life and the life of your family forever in a blink of an eye.
Be safe, enjoy the rain but be careful and stay a safe distance from all down utility lines. For more information please go to the PG&E web site or contact your local fire department.