First Responders & Electrical Hazards

>> Engine 501, 502, 503, Ladder 510, and rescue 513 respond to report of a house fire at 13075 Nelson. 13075 Nelson; corner of Nelson and Elm Grove Road. Time out 9:46.

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>> Okay Bob let's go. 501 in route to a possible house fire 13075 Nelson.

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>> Dispatch we're at 13155 Nelson. Looks like we have an electric substation here. Notify the electric company; there is smoke visible.

>> First responders arriving at an emergency scene soon realize that appearances can be deceiving. Even the most routine calls like this apparent house fire can turn into a real challenge. When it involves electrical facilities you've got to be prepared for anything and everything. The purpose of this program is to increase your awareness of electrical hazards so that you'll know how to safely deal with them during an emergency. Electricity performs so quietly and efficiently that we tend to take it for granted. We shouldn't. Never underestimate its potential dangers. Variables like human error or foul weather can produce unpredictable and highly dangerous electrical hazards in a split second. That's why first responders must never attempt to remove fallen wires, disconnect electrical services, or enter substations unescorted. Electrical utility employees are the only people properly equipped, trained, and authorized to deal with high voltage power equipment. In this program I'd like to cover several key points regarding electricity, its inherent dangers, and measures that must be taken to ensure your safety and the safety of those around you.

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First let's establish a framework of understanding about the principles of electricity. For our purposes an electrical system can be loosely compared to a water system. Water in a pond or a vessel will stay at rest until it's connected to pipes and a pump. The pump builds up pressure, prompting the water to move through the pipes which direct it to specific end uses. Now notice that we're using a closed system; that is the water is directed back to the source for recirculation. If it weren't we would eventually run out of water. An electrical system is similar in that a generator, like a water pump, is used to gather free electrons and build up a pressure potential, which is measured in terms of voltage. This pressure allows electrical current to flow along the wires of the system for distribution, and ultimately back to the source. Since the source of free electrons is the earth it is considered to be at zero potential. Now here's the most important thing to remember about electrical systems. Like water, which is continually seeking its lowest level, current in an electrical system flows from higher potential to lower potential without exception. It's always seeking the quickest path to the ground, which is at zero potential, and it doesn't discriminate between paths to take. It aggressively attempts to return to its source, and it will unless it's prevented from doing so. The ceramic insulators on power lines are one means of prevention. Understanding the concept of potential difference is critical to your safety. Electricity will take any and all conductive paths to return to its source. Thinking back to our water system analogy we realized that it takes pipes or hoses to direct water from one point to another. Objects that allow the passage of electrical current are known as conductors. We're surrounded by conductive objects, many of which none appear at all like wires. For example, water. Water is an excellent conductor of electricity. Attempting to extinguish a fire involving energized electrical equipment with a water stream is like attacking with a bare wire; it could be a fatal mistake. Dwelling on water for a moment, remember that the human body is mostly water and is therefore an excellent conductor. Other familiar objects, such as tree branches, pipe poles, and ladders are potential conductors as well. Remembering that electricity is always seeking to return to its source one can readily understand that if we allow a conductive object to come into contact with the electrical system while we are in contact with the earth an electrical current will flow through our bodies causing serious injury or death. Electrical current is always seeking its lowest potential, the ground. It will take the easiest conductive path to get there.

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Now that we understand the basics let's go on to learn more specifics about electrical systems and how you might encounter them in emergency situations. In order to efficiently distribute electricity to an entire service area the voltage leaving the power plant is extremely high, generally hundreds of thousands of volts. Now spotted along the transmission lines are substations. These are used to redirect the flow of energy and reduce it to lower voltages for smaller substations and to ultimately deliver the current to the end user. Although most substations are utility owned not all of them are. They can be found in a great variety of locations, shapes, and sizes. Most often they stand alone, surrounded by wire fences, but they can also be found atop buildings or deep within structures, mounted on concrete pads, or buried in underground vaults. One property common to all substations though is high voltage. For public safety they're highly secured areas. No one other than authorized personnel are allowed to enter and the warning signs should be taken seriously by everyone, including all types of first responders. Once inside the security enclosure high voltage electrical equipment is most likely within arm's reach.

>> Dispatcher, engine 35; it's 10:23. We've got smoke showing inside the substation at 306 South 116th Street. We request a full assignment, the police for crowd and traffic control, and also the services of the electric company.

>> If an emergency involves a substation contact the owner and wait for them to arrive. Never attempt to enter unescorted.

>> Before we can get in there to make any--

>> Fires involving substation equipment generally result in irreparable damage to the equipment, thus it's not only extremely dangerous to attack such a fire, it's generally unnecessary. A first responder at such a fire should secure the area until the owner arrives. In the interim steps should be taken to assure that the fire doesn't spread outside of the secured area. Once inside never attempt to operate any of the equipment, especially devices that otherwise appear to be switches. Unlike the common electrical switches people are used to these are not designed to be operated under load. Doing so could result in an electrical arch, flash, and explosion that can easily result in fatal injuries to yourself and anyone in the immediate vicinity. Also be aware that many pieces of substation equipment can be filled with large amounts of oil, therefore dangers of toxic smoke and explosion are always present. Remember that substation emergencies present extreme hazards to the first responder. Your first responsibility is to secure the area and protect the public while waiting for the owner to arrive. As necessary provide fire suppression to make sure that it doesn't spread to adjacent areas and facilities. Do not enter unescorted, the dangers are just too extreme.

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The majority of the electrical distribution systems involve wires mounted on overhead poles and tower structures. It's inevitable that some emergencies will involve wires that have fallen to the ground. The two most common causes are car pole accidents and foul weather. Upon arrival at the scene of a down wire it's easy to conclude that the wire is de-energized; there's no arching or sparking, therefore it must be dead; this could be a fatal mistake. Electrical systems are designed with automatic protective devices to de-energize fallen wires. Now even though these devices work safely roughly 95% of the time a first responder should always expect the unexpected. An otherwise dormant appearing wire could be that five percent that are fully energized; it's hardly a risk worth taking. Don't touch fallen wires. High voltage wires that have fallen to the ground may remain isolated, or at least sufficiently insulated from the earth so that the current flowing to the ground is not high enough to trip a protective device. If a person touches such a wire their body becomes another path to the ground. Serious injury and death can easily result. Another reason not to tamper with a down wire is a phenomenon known as back feed. Let me explain. Portable electric generators have become more affordable in recent years. They're found in many commercial, farm, and residential settings as a backup in the event of a power failure. Unfortunately it's very easy to install these units improperly or to have a proper installation simply fail. This often allows current to feed back into the electrical system.

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This can be deadly. Even the smallest of these generators can provide enough current to kill. In every situation involving wires down the first responder's initial action must be to call the local utility. If lives are in danger communicate this fact to the utility; it will have an impact on the priority of response.

>> We will be standing by until the arrival of the electric company.

>> Never attempt to move the wire on your own. Ropes, wooded, and fiberglass poles can all conduct electricity. Don't confuse your pipe poles with the insulated fiberglass sticks that you've seen the utility workers use. Even small amounts of moisture and other contaminants can turn otherwise non-conductive objects into live wires. While waiting for the utility to arrive take steps to secure the area but stay as far away as practical from the downed wire. Survey the surrounding area. Have the wires fallen on other conductive objects such as fences or guardrails? Treat these as energized too. Just because the downed wire doesn't look like a power wire always assume that it's energized at high voltages. Cable TV and telephones have been known to become entangled with high voltage lines. Similarly, never assume that a wire is insulated. Low voltage wires are initially insulated, but the effects of weather and physical damage often render the insulation useless. In every situation involving wires down the first responder's initial action must be to call the local utility.

>> And standing by until the arrival of the electric company.

>> Never attempt to move the wire on your own.

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>> Car-pole accidents should be treated just like any downed wire incident, with two important differences; they almost always involve people, and the rescue is frequently complicated by severe injuries in addition to the electrical hazard. Initial scene assessment is critical. This assessment should include the electrical hazards presented by downed wires on the vehicle or laying on the ground, low hanging wires, and other conductive objects. Stay alert. While one responder establishes contact with the vehicle occupants the other should be notifying the local utility and establishing a safety zone.

>> No you won't be electrocuted.

>> Instruct the vehicle occupants to remain calm and in the vehicle.

>> The ambulance is coming. So long as you stay in the vehicle you'll be safe.

>> They are in no electrical danger at this point. Why? Because they and their vehicle are at the same electrical potential as the wire. The danger arises when they or you contact the vehicle and the ground at the same time. Remember electricity is always trying to return to its source, the earth. If a person touches the car and the ground at the same time the person will become a path to the ground for the electricity and severe injury or death can result. Your best course of action is to convince the occupants that they're safest staying in the vehicle until utility personnel arrive to de-energize the wire. A firefighter's duty is to save lives, that includes your own.

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When responding to fire scenes with areal ladders, articulated booms, or water tower apparatus extra care must be exercised. Equipment should be placed so that its operation won't take it into proximity with overhead wires.

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Whenever possible equipment should be placed so that its operation will not take it into proximity of overhead wires. Most governmental agencies and utilities suggest a minimum clearance of 10 feet away from all conductors up to 50,000 volts. Above this voltage additional clearance is required. Always plan for the maximum possible clearance. The settling of an outrigger or a sudden gust of wind can allow the equipment to contact the wires. From this test area let's discuss one of the myths of electricity. After having witnessed an electrical storm many people have the mistaken notion that electricity can jump out of the wires and travel long distances through the air. Research says that it takes 10,000 volts of electricity to jump a quarter inch gap, and considering that the vast majority of electrical wires around buildings are energized at 30,000 volts or less one must, for all practical purposes, come into direct contact with the conductor in order to draw an arch. However, once the arch has started the air around it becomes ionized, thus allowing the arch to be drawn out significant distances. The point here is that once contact is made an arch will form when trying to break contact. The size of the arch is determined by how much current is flowing from the wire through the apparatus to ground. The hazards to firefighters at this point are the same as in a car-pole accident situation. Those who are on the equipment should remain where they are, while those on the ground must not approach the equipment or attempt to rescue until the wires have been de-energized.

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When a grass or a small brush fire is burning under power lines or around the base of poles use standard firefighting practices to extinguish the fire. If there is deep char around the base of the poles notify the electric utility because they're going to want to inspect the poles for possible replacement. If a downed wire is involved in the fire use a spray stream to keep the fire in check and protect the surrounding area. Never use a straight or solid stream. If the fire is near the top of the pole or in pole mounted equipment, such as transformers, oil switch gear or capacitors and it appears that the fire will not endanger life or property let it burn and quickly notify the electrical utility.

>> Dispatcher this is engine 35. We're on location. Notify the electric company we have a transformer fire.

>> The first responder's job here is to protect and guard the area. Remember once electrical equipment has caught fire it's beyond repair and certainly not worth the cost of a serious injury or a life. In rare cases where the fire must be attacked and the wires or equipment haven't been de-energized extreme caution should be exercised. First notify the electric utility. Then attack the fire using a water spray; never ever use a straight stream, and always be aware that most pole mounted electrical equipment contains oil. The danger of an explosion from excessive heat is always present, and that may spray hot oil over large areas. Maintain a cooling spray until the equipment can be de-energized. Also be sure to stay out from underneath any overhead conductors in case they fail and fall.

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Aside from the hazards discussed previously most of the electrical problems facing first responders at a structure fire are of a low voltage variety. Low voltage is generally defined as voltages below 600. Some first responders feel it's necessary to de-energize equipment where low voltage is involved, but even low voltage circuits possess dangers, potentially lethal ones. Cutting the service wires is not a recommended practice. Due to the close spacing of the conductors it can be dangerous and considering that most newer homes have underground services it may be impossible to do so. Many first responders believe that removing the electric service meter is the easiest and most full proof way to de-energize the facility. Nothing could be further from the truth. Removing the meter may or may not disconnect the energy supply. The danger lies in not knowing for sure. You see some meters have automatic devices to provide continuous service. Others don't interrupt the current flow when removed, and in some rare cases customers may have tampered with the wiring to divert current around the metering device. Most importantly the act of removing a service meter is extremely dangerous. During the course of a fire the meter glass can be exposed to extreme heat causing a buildup of explosive forces within the meter glass. Sometimes flammable vapors accumulate in the meter enclosure. Either of these or a short circuit during removal can result in tragedy.

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The first responder is faced with many challenges. Don't let live electrical equipment foil your efforts. Remember these simple guidelines; upon arrival assess the scene for hazards, especially electrical ones. Secure the area for the safety of the public and your coworkers. Contact the local utility immediately. Never attempt to move a downed wire; only authorized utility personnel have the necessary skills and equipment to do it safely. Treat all wires as if they were energized at high voltage and expect the unexpected.

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