Transmission risks
or imbalance is detected, the circuit is immediately broken and will stop conducting electricity, preventing damage to equipment and the people using it. The latest connected energy sensors, which combine protection and communications, allow the health of the load, supply network and protective infrastructure to be continuously monitored, viewed and diagnosed to ensure a reliable, efficient and safe installation.
Arc faults
‘Arc faults’ are actually frequently caused by human error or ageing installations; for example, they can be due to loose terminals or cable damage. When they occur, a localised hot spot is established that carbonises insulating materials and this acts as a conductor which enables currents to run through them in the form of an arc of electricity. The arcs cause further burning that produces more carbon, which in turn conducts increased current. Arc faults create a vicious circle that can quickly snowball into a fire hazard. In many environments, arc faults are almost impossible to avoid or prevent. However, with the latest tools and technology, they can be safely managed by operators. The latest generation of arc fault detection devices (AFDDs) mitigate the risk of electrical fires caused by electrical arcs resulting from faulty or worn electrical appliances and circuits. Such devices continuously monitor circuits for fault related electrical arcs. Upon detection,
they break the circuit and prevent the arc from doing further damage. AFDDs should selectively distinguish between distortions that occur during normal operation and potentially dangerous arcs occurring in faulty equipment. If a rise in current exceeds the capacity of its
cable, the components are likely to overheat with the potential to cause a fire. In the extreme case of a short circuit, the sudden release of a large amount of energy can even lead to an explosion.
Leakage currents
Since the very beginning of electrification, fuses and circuit breakers have been instrumental in preventing these hazards, but a new generation of solutions is taking protection to the next level. By combining protection with enhanced communications, organisations can continuously monitor and diagnose the health of their loads. When electrical insulation becomes
degraded, or where there is excessive moisture or corrosion present, electrical currents can leak towards the ground or neighbouring conductive elements. Indeed, the majority of electrical faults in low voltage installations are caused by earth insulation failures. In a dusty and humid environment, an insulation failure between line conductors and the earth can lead to an arc fault and start a fire. In fact, tests have shown that fires can be started even in a fault current as low as 300mA.
FOCUS
www.frmjournal.com OCTOBER 2019
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