A Foundation of Electrical Knowledge
A Foundation of Electrical Knowledge |
|
Understanding more about electricity and how electricity works will assist with being able to respond to emergency situations in which electricity is involved.
Electricity begins with physics. It is important to start with a few definitions, so that the main concepts are clear. There are essentially three different units of measure used to quantify electricity:
|
It is often helpful to use an analogy to visualize and better understand the definition of an abstract electrical concept. In this case, we will use the analogy of water to better clarify the definitions of volts, amps and Ohms. |
When you are dealing with emergency situations that involve electricity, it is important to have knowledge about the terms that you may hear associated with these types of emergencies. Different electrical situations will involve different degrees of voltage and amperage. An electrical circuit is a completed path from the source of generation, through work and returning to source.
Current flows in a circuit because there is a difference of voltage between two points. "Ground" or earth, will provide a return path to short cut the circuit (short circuit). Contact with ground and any voltage will cause current to flow. It is common to say, "electricity is always searching for a path to ground." Insulators have a high degree of resistance to electrical current and tend to hinder the flow of electricity. Conductors transmit electricity very well and have a very low resistance. The electrical system uses both conductors and insulators in the distribution of electricity.
Some materials are sort of between insulators and conductors. These materials are called semi-conductors and have some characteristics of the two classifications. Semi-conductors have the ability to conduct large amounts of electricity, depending on the conditions. Variable conditions might include the presence of moisture or the presence of contaminants in the material. Wood and earth are good examples of semi-conductors. It is important to remember that VERY FEW materials are non-conductive when voltage is extremely high.
Although it is true that electricity will take the easiest path to ground, in fact, electricity takes ALL paths to ground, not just the easiest path. It is important that you do not become part of one of these paths!
As emergency responders, you know very well that when you arrive at the scene of an emergency, you very quickly must assess what is going on and determine the best course of action for doing what needs to be done to protect yourself and others. Different types of emergency responders have completed different types of education and training. Although the labels and jargon may differ, the basic emergency action principles are the same for all emergency responders in terms of conducting a risk assessment.
Protective Actions are those steps taken to preserve the health and safety of emergency responders and the public during an incident. As emergency responders, you are used to being the ones called to the scene of an accident or emergency. However, where electricity is involved, you need to be aware that you can and should contact the local power supplier. Most local power suppliers have an emergency number that is made available to the dispatch units for emergency responders. There is nothing wrong with calling for additional assistance. The BEST course of action is to contact the local power supplier to have trained and equipped technicians dispatched to the scene of the accident, to assist with controlling the electrical hazards.
One essential premise to remember when dealing with an emergency situation involving electricity is that the involved victims should only be approached and examined IF they are clear of the source of electricity or IF the source of electricity has been made safe by the local power supplier personnel. Involved victims may be still energized. If this is the case, getting too close to the victim may mean transfer of the electrical energy. Electricity seeks all paths to ground. When electricity flows to ground in an uncontrolled fashion, the electricity is released into the ground and ripples out from the contact area. One of the primary priorities when dealing with electricity is to not expose oneself to risk while trying to eliminate the danger!
|
Once again for our metaphorical thinkers out there, picture in your mind a serene and calm body of water (probably NOT the Atlantic Ocean). When a stone is dropped into the body of water it ripples out from the stone. As the ripples get further away from the stone, the ripple gets weaker. In the same way, as electricity ripples out from the source on the ground, it starts out in pools very strong around the source, but then gradually diminishes. Knowledge of this ground surface gradient can save your life. You do not have to be in DIRECT contact with the source of the electricity to be harmed by the electricity. It is best to stay at least 8 meters away from areas where electricity is accidentally in contact with ground. This relates to both touch potential and step potential. |
|
|
Step Potential: Step potential occurs when your feet are apart, near areas where electricity is going to ground. Your feet can be at two different voltages. For example, if one foot is nearer the point of contact where the voltage is strongest and the other foot is further away from the point of contact, the voltage difference between the two points could cause electricity to flow through your body. This is why it is so important that when you are around an area where electricity has come into contact with the ground that you stand with your feet extremely close together. The only safe way to move would be by taking small shuffling steps or by hopping with your feet together to keep the voltage approximately the same at both feet (note: shuffling would be safer than hopping as there is less chance of falling). |
|
Touch Potential: Touch potential is similar and occurs when different parts of your body contacts objects at different voltages and your body becomes 'part of the circuit'. This could happen if a person were to touch something that is energized with a hand or arm while standing on something at a different voltage or connected to ground. This difference in voltage between the contact points causes electricity to flow through your body. |
Although many emergency responders are required to wear protective footwear, this type of personal protective equipment is usually NOT designed to provide protection from electricity. No matter how fancy or snazzy your protective footwear, footwear must NEVER be relied upon to provide protection from electricity.
It cannot be emphasized enough that you MUST ensure that victims are clear of electricity before proceeding with your assessment of the victim.
|
This section has examined some of the basic characteristics of electricity. This knowledge will be important to you in making informed decisions with regards to emergency situations involving electricity. |
|
|
|
| - College - | - Course - |
