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Fighting fire: how modern circuit protection and IoT connectivity protect end users and their installations

Introduction

Electrical installations can deteriorate with age, this can often depend on environmental factors such as heat and humidity, as well as damage during use and corrosive chemical reactions.

Home Office figures suggest there were 27,621 accidental dwelling fires between 2017 and 18, 34 percent of which were caused by ‘misuse of equipment or appliances’. These dangers are real and apparent and installations must always be treated with caution.

Only technology can prevent electrical fires

Fortunately, technology provides many ways to protect against the worst effects of electrical fires. It’s impossible for building and facility managers to monitor all parts of a circuit at once, so organizations should look to solutions that actively hunt for faults and intervene to protect users from harm and mitigate hazards.

Arc faults

‘Arc faults’ are often caused by human error or aging installations. For example, they can be due to loose terminals or cable damage. When these occur a localised hot spot is established that carbonises insulating materials.

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) mitigates the risk of electrical fires caused by electrical arcs resulting from faulty or worn electrical appliances and circuits.

These 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 that occur in faulty equipment. As an example, Schneider Electric DIN rail Acti 9 iARC module:

Continuously monitors circuits for fault-related electrical arcs. Upon detection of such arcs, it breaks the circuit

 Selectively distinguishes between harmless arcs that occur during normal operation of a switch, plug or motor and potentially dangerous arcs that occur in faulty equipment or cabling

 Monitoring the status of these circuits provides knowledge about the health of the installation and in addition targets any follow up activity following the detection of an arc fault

Leakage currents

When electrical insulation becomes degraded, or where there is excessive moisture or corrosion present, electrical currents can leak towards the ground or neighboring conductive elements.

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. Indeed, test have shown fires can be started even is a fault current as low as 300 mA.

The dangers are well known to regulators. The IEC 60364-4-42:2010 (clause 422.3.9) makes it mandatory to install highly sensitive residual current devices (RCDs) in increased fire-risk locations. In the UK, the BS7671 standard requires installations to have RCD protection provided by a tripping current (IΔn) that does not exceed 300mA wherever an increased fire risk exists.

Earth leakage circuit breakers can be used in lieu of traditional overcurrent-only breakers at no additional footprint, while increasing safety. The option of just enabling an alarm instead of tripping, can also avoid disruptions by limiting downtime.

Since 2019, Schneider Electric are offering Earth Leakage Moulded-Case Circuit-Breakers (NSX ELCBs) with integrated RCD protection, either in “trip” version (breaker tripping for a leakage current over threshold, e. g. 300 mA ) and in “alarm” version (breaker sending an alarm for a leakage current over threshold, but no trip).

Arc flashes

When a short-circuit occurs between the live parts of a system, the current travels through the air or nearby gases. This releases a large amount of energy in a fraction of a second, taking the form of heat, sound, light and pressure waves. This type of fault, normally described as an ‘arc flash’, poses a significant fire risk.

Personal protective equipment is crucial for workers where arc flashes are involved, but faster-acting devices are also key to mitigating them in the first place, enhancing safety. To reduce the severity of arc flash hazards workers are exposed to, arc flash energy levels must themselves be reduced.

Schneider Electric Masterpact MTZ air circuit breakers (ACBs) with the “Energy Reduction Maintenance Settings” digital module provides new answer to the Arc Flash hazard reduction problem. The ERMS function, when engaged, allows the Micrologic X control unit to operate faster.

Should an internal arc fault occurs downstream to Masterpact MTZ , the reduced fault clearing time allows a decrease in the amount of energy generated by the electrical arc, and can limit the risk of injury.

The power to know

When designing or implementing an electrical installation, safety should always be front of mind. Specifiers and installers should be aware of the dangers of arc flashes, faults, and current leakage, preferring smart solutions that monitor proactively and intervene automatically to prevent and limit the damages of an electrical fire.

Through analysis and monitoring of real-time data, IoT-connected devices not only tell you when exactly there is a problem but where the source of the issue is. This ability to anticipate and react quickly to hazards limits damage and protects contractors, engineers and end users from harm. Through connected product and edge control software – offered by Schneider Electric solutions such as EcoStruxure – circuits may be monitored to safeguard the health of the installation while making it more reliable, efficient and safe.

AlessandroDeDanieli has not written a bio yet…

11 Mar 2019, 12:03