Electrical Safety

The 5 critical faults that cause electrical fires

Electricity is something we all depend to drive the operation and comfort of our businesses and our homes. And we expect our electrical installations to be safe, protecting people from the risk of shock or electrocution, and protecting buildings from the risk of electrical fire. While local electrical safety regulations and protective technologies continue to advance, there are still many hazards existing today.

In my last post in this series I mentioned that France has an electrical fire about every 8 minutes. That’s a staggering statistic. In this post, we’ll look the reasons for these problems. First, electrical installations can deteriorate over time, causing energized conductors to become exposed or electrical equipment to malfunction. But hazards can also exist because the electrical system of a facility or home was not installed, upgraded, or maintained properly. This is why it’s important to have electrical installations thoroughly checked if you see anything of concern, like a damaged outlet.

Arc faults. Technically, an electric arc is defined as “a light electrical discharge through an insulating material, usually accompanied by the partial volatilization [vapourization] of the electrodes.” When an arc occurs across a gap, the temperature at the center can be between 5,000 and 15,000 °C, with hot gas and bits of electrode shooting out in all directions. Obviously, this can be a fire risk. But why do such arcs occur? Such ‘arc faults’ are often related to human error or aging installations. For example, they can be due to loose terminals or a crushed cable. Whenever a connection is not properly tightened or a conductor is damaged a localized hot spot occurs that carbonizes the insulating materials in the vicinity of that conductor. This carbonization acts as a conductor enabling currents to run through them in the form of electric arcs. These arcs cause more burning which, in turn, produces more carbon, conducts more current, etc. It’s a vicious circle that can quickly turn into a fire hazard.

Electrical overloads. When there’s a rise in current that exceeds the capacity of the cable it will cause it to overheat which can, in turn, cause a fire. This situation is often caused by too many loads connected to the same circuit, e.g. several energy-hungry devices on the same power strip.

Short circuits. When contact inadvertently happens between two conductors the current will take the ‘shortest’ route, from one to the other, without traveling through the rest of the circuit. This type of fault causes an increase in current and a subsequent rise in the temperature of the conductors. This can ultimately destroy the supply circuit and cause a fire.

Leakage current. When electrical insulation becomes degraded, or where there is excessive moisture or corrosion present, electrical current can leak towards earth ground or neighboring conductive elements. These conditions are often found in older, dilapidated facilities. Beyond the loss of energy, the leakage current can cause an electrical fire. However, it can also be a serious risk to human safety. For example, imagine a bare electrical cable under a wet carpet. A person walking across that carpet may either be injured by ‘electrification’ (i.e. shock) or, in the worst case, pass enough current through their body to experience a fatal electrocution.

Lightning. A typical bolt of lightning carries an electric current of 30,000 amperes (30 kA). If such a discharge travels along a power line to a facility, or if a facility is struck directly by lightning, it can cause a massive fire hazard. A lightning-induced surge of current through the facility’s electrical network can cause the deterioration of electronic equipment, and even start a fire inside of electrical devices.

As you’ve read, there are many types of electrical faults that can post serious risks. Fortunately, there are protective solutions for all of these. Schneider Electric is a leader in electrical protection, including protection against the risks of fire, shock, and electrocution. Read more electrical safety articles here on the SE Blog.


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