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Despite the electrical industry’s commitment to safety by design, we still live in a world where 5-10 arc flashes occur every day. However, according to the U.S. Bureau of Labor Statistics (BLS), the frequency of fatal electrical incidents has steadily declined over recent decades.
The primary reasons for this decline include:
- Digitization – Instead of direct interaction, remote monitoring allows workers to remain outside of the arc flash boundary.
- Prevention – Controls and products are engineered to reduce arc flash incident energy (AFIE) and prevent arc flashes.
- Containment – Effective options are now available for containing arc blasts when they do occur.
When it’s too late to prevent an arc flash incident, what are your best options for isolation and containment? In this article, we’ll focus on the equipment and technology designed to do both.
#1: Isolate and contain with ArcBlok
ArcBlokTM is a passive arc flash isolation and containment solution from Schneider Electric that is currently available in the Square DTM Model 6 Arc Resistant Motor Control Center (MCC). Additional applications will launch by the end of 2022. These include ArcBlok for P-frame breakers up to 1200A in MCCs and in R-frame breakers up to 2500A available for brownfield installation in MCCs and switchboards.
ArcBlok provides 24/7 protection on the line side by fully enclosing the connectors in an ANSI/IEEE C37.20.7-2017 cable vault to reduce the possibility of accidental contact from tools, debris, or a worker’s hand. Steel barriers inside the vault provide phase-to-phase and phase-to-ground isolation, even if the steel front panel is removed. If an arc flash occurs, the vault contains, extinguishes, and redirects the AFIE to minimize damage and injury.
ArcBlok is equipped with digital thermal sensors that allow qualified electrical workers (QEWs) to access temperature readings by scanning an NFC tag on their mobile device. This helps reduce the need to open panels and don bulky PPE, since monitoring occurs outside the arc flash boundary.
#2: Model 6 Arc Resistant Motor Control Center
The Square D by Schneider Electric™ Model 6 Low Voltage MCC with ArcBlok is engineered to minimize the chances of arc flash incidents occurring, and to contain the energy if one does. It is equipped with ArcBlok to isolate line-side connectors and provides a variety of other arc containment features with the smallest footprint on the market.
If an arc flash occurs in the Model 6 MCC, the incident energy is directed through vented shelves to an arc chimney on the rear of the unit. Sealing flanges on the shelves and bottom plate contain the energy so it is channeled up the chimney and out of the vents on top of the MCC, instead of allowing it to project forward where it could harm workers and damage equipment. A plenum can also be added for more control over the exhaust pattern.
The Arc Resistant MCC is constructed from 12-gauge steel and is Arc Resistant Type 2A rated with protection on the front, sides, and rear of the enclosure. The MCC is designed with native digital tools, including sensors for remote monitoring and other connected controls that reduce the need for workers to directly interact with the equipment.
#3: Power-Zone 4 arc resistant low voltage switchgear
Power-Zone 4 arc resistant switchgear is certified arc resistant per ANSI C37.20.7. At the heart of the equipment is an ANSI Type 2B rated enclosure designed to contain arc flash incident energy on all sides, even when the panel door is open. Self-extinguishing MasterPacTTM ArcBlok Circuit Breakers reduce arc duration to limit equipment damage and risk of injury.
#4: CGBG-0 gas insulated switchgear
Gas insulated switchgear (GIS) equipment is engineered for safety. The main circuit on the CGBG-0 series of switchgears from Schneider Electric is insulated with SP6, a high dielectric, harmless gas that is 100 times more effective than air for extinguishing arcing faults. The core unit on the circuit breaker is filled with SP6 and sealed for life at the factory. Since it never needs to be opened, live parts are fully isolated to eliminate the risk of an arc flash from accidental contact.
Sealed components require zero maintenance and help ensure continuity of service since they are protected from environmental intrusions like moisture, dust, and rodents. Although the silicone-insulated busbar and line-side connectors on CGBG-0 switchgears are located outside of the gas-insulated modules, all live connections are isolated and touch proof. Plus, with a footprint that’s a fraction of the size of air-insulated switchgears, it is a cost-effective way to reduce the risk of arc flash with a lower lifetime cost than other containment solutions.
Additional arc flash safety resources from Schneider Electric
The above passive containment options add protection that dramatically reduces damage and injury if an incident does happen. Of course, the best way to reduce arc flash injuries and losses is to prevent arcing faults from occurring. This can be partially achieved by combining controls with equipment to isolate live connections and reduce AFIE. To learn more about arc flash safety, download Mitigating Arc Flash Hazards, a Schneider Electric white paper.
