Most apprentice electricians are, understandably, scared to work on live electrical circuits. Mostly because they don’t understand the fundamentals of how current flows between two points. This article will introduce you to the multiple ways a current can flow through a human body and shock or electrocute it.
Direct Contact
The first way a person can be shocked or electrocuted is through direct contact with an energized termination or conductor. This is one of the most common scenarios for electrocution (electrical death). Many people try to work on their own lighting, receptacles, breakers, and appliances and forget to turn the power off before doing so. When they go to work on the equipment they often don’t think about what they’re touching elsewhere on their body.
If, for example, they are standing on a metal ladder that has no rubber insulation and holding the ladder with one hand, while touching a live conductor with the other hand. The metal ladder, if it is leaned against the steel of a building that steel is typically bonded to the grounding system. Which completes a circuit back to the transformer at the front of the property. In this case they get shocked. Because they’ve allowed a path from one potential, through them, to another potential. Or in simple terms, they’ve introduced themselves into the circuit and become the load.
Lighting Outlets
Another similar way people get shocked is at electrical outlets such as receptacle outlets or lighting outlets. If a person screws in or unscrews a lightbulb while a light switch is on and they allow their fingers to get inside the socket, they can get shocked when they touch both the screw shell and the bottom pin of the socket at the same time. Remember, current only flows between two different potentials. So if they had only touched one of these things, they would not have been shocked. (Assuming they weren’t also barefoot or on a metal ladder or touching something else made of metal).
Current always travels in loops, from one potential to another. This means that wherever there exists a difference of potential (a voltage), for example, between a hot and a neutral, connecting the two will create a path for current to travel between them.
Plugging In or Unplugging Cords
Many people have been shocked when plugging in or unplugging cords into receptacle outlets. Such as vacuum cleaners and extension cords.
To get shocked, the current needs to use you as a path to get from the source back to the source. Touching a single energized object is not going to shock you until you connect to another object that is at a different potential. Many people have touched their fingers to both prongs of a plug when inserting it into a receptacle. Your finger, in this case, is completing the circuit with the hot and neutral prongs of the plug when it’s being inserted. If you don’t connect two different points of potential, you don’t get shocked. But if you touch both points of potential current will flow through you to get from one to the other.
Presence of Water
One unexpected way a lot of people have been shocked is through working with faulty extension cords in wet environments. It’s always important to remember that when your skin is wet, its resistance to current flow is lower compared with that of dry skin. People can be badly injured if they get shocked when they’re wet. This is the reason electricians are required to install GFCI protection on receptacles in or near wet locations.
Faults
Another type of shock can occur from a condition that we consider a “fault”. There are two types of faults, a ground-fault, and an arc-fault. One example of a ground fault happens when an energized conductor breaks free inside of a metal appliance. Then touches the metal casing of the appliance. It could energize the entire metal frame/casing of the appliance if proper grounding is not in place which would otherwise have tripped the breaker.
In this example, if a person were to walk up and touch the appliance with their hand while standing barefoot on a concrete floor, current could travel through their entire body into the concrete and possibly injure them badly. Remember that current cannot travel if it doesn’t have two different potentials to travel between. If the person had rubber boots on, they could touch the energized metal of the appliance and not get electrocuted. This shows the importance of wearing proper PPE when working on live electrical circuits.
Static Shocks
A simple way that a person can get shocked is through static discharge. By touching an object such as metal, and then touching something else like the ground. This is a much smaller type of shock. Usually experienced after a build-up of friction. Which causes a body to build up an excess of charge relative to, say, a metal doorknob. Remember, current can only travel between two different potentials. If there’s no buildup of charge between two different objects, a static discharge will not occur.
Energized Circuits Near Wet Soil
A common way electricians get unexpectedly shocked is by kneeling down on wet soil while working on a live circuit in front of them. Many electricians who repair street lighting, or parking lot poles are familiar with this. Once you grab an energized conductor and kneel down, touching your knee to wet soil means that the current has a way to travel between you and another potential (the earth). Always use rubber pads when kneeling down and working on live circuits.
Arcing
Yet another way that people get shocked is through arcing components in a circuit, device, or appliance. We call unintentional arcing in a circuit, an arc-fault. A series arc-fault is an arc that happens at a loose termination. A parallel arc-fault occurs between two hot conductors, or a hot and a neutral. Arc-faults can cause fires when they occur near flammable materials. An arc can also reach through the air and find a different potential to travel through if given the right amount of voltage and a low enough resistance to the flow of current. Arcing in an appliance can be caused by a loose wire, or when debris gets caught in a spinning fan. Arcing is one of the most common causes of house fires.
Contact With Energized Equipment
Another way that people get shocked is through contact with energized power lines and equipment such as live wires, transformers, generators, and motors. In a lot of cases, it is due to an untrained person working on circuits they shouldn’t be, but sometimes faulty installations can cause this as well.
Cutting Through Conductors
We sometimes hear tragic news stories in which people have been killed by cutting live conductors in attempts to steal copper and resell it at a metal scrapyard. What these people don’t realize is that cutting the conductors can introduce them to the circuit and cause a massive amount of current to flow through their bodies, which can kill them instantly.
Arc Flash
Arc-flashing is another type of unintended and violent contact with an electrical circuit. During an arc flash, so much energy is released from a single point in an electrical circuit that it can create a fireball that can fill an entire room. So much heat can build up in a split second that it will literally turn solid metal into vapor. It’s so intense it skips liquification and goes straight to the next form of matter – a gas! The incredible amount of heat, and the speed that it takes to do this, can send a wave of intense thermal energy outward and kill someone standing nearby, in an instant.
Lightning
If lightning strikes near your house during a storm, not only can it damage the electrical components in a system, but it can travel along any metal water piping or other metal grids/structures in the ground and electrocute a person who may be touching connected metal in or near a structure. When lightning strikes, it seeks the path of least resistance to the ground. While the primary route may be the object it directly strikes, the immense energy contained in a lightning bolt can spread out and follow various secondary paths.
High Voltage Line Grounded
If a high-voltage line falls and comes into contact with the ground, it can create a voltage gradient in the nearby area due to the difference in soil consistency in an area. This means that there could be a difference in the electric potential between two points on the ground, even between two points as close as the distance between your feet. If you were to step in this area, your body might complete the electric circuit, allowing current to flow through you with possibly life-threatening consequences. This phenomenon is known as “step potential” and closely resembles “touch potential” from a normal shock.
To visualize step potential better, imagine a scenario where a lightning strike or a fault in the electrical substation creates an “electrically charged” zone on the ground. If you were to step into this zone, different parts of your body could come into contact with areas having different electric potentials. This would allow electricity to flow through your body. Seeking to equalize the potential difference, which is what leads to electric shocks.
Utility companies train their employees to use specific techniques. This includes dragging their feet or shuffling without lifting their feet off the ground. Which can minimize the risk of electric shock in areas where there might be a dangerous voltage gradient. Such as near a downed power line or in a substation with a ground fault. By dragging or shuffling your feet, you maintain a more consistent contact with the ground. Which helps minimize the potential difference between your feet and thereby reducing the risk of electric shock. It essentially ensures that the points of contact with the ground (the feet) are at nearly the same electric potential, minimizing the danger associated with step potential.
How Easy It Is to Get Hurt
The effects of electric shock on the human body can vary greatly depending on a variety of factors. This includes the duration of the exposure, the pathway the electricity takes through the body, and individual physiological differences. 20mA of current traveling through a person is enough to damage skin tissue. This is 0.02 Amperes, which is a very small amount of current. 200mA (0.2 A) is enough to cause ventricular fibrillation, a serious kind of heart arrhythmia that can be life-threatening. Anything above this threshold is enough to cause such strong muscle contraction that a heart may stop. Causing a person to go into cardiac arrest and potentially serious burns to skin tissue. This is not even 1 Ampere of current.
As you can see, there are a ton of different ways that a person can get shocked. It’s not only high current traveling through a person’s heart that is dangerous. Even small amounts of current traveling through your body can seriously injure, or possibly kill you. Knowing basic first aid for electric shock can go far. This stuff is no joke. There are people out there with scars all over their bodies from having to get skin grafts to repair burns they’ve suffered from arc flashes. So please, be very careful working on electrical circuits. Don’t work live unless you’re properly trained on how to do so. Safety always come first.
