UFES

An internal arc fault is a severe and highly dangerous event that occurs when an electrical breakdown inside a switchgear causes an uncontrolled arc to form between energized conductors. This arc generates an enormous release of energy in a very short time -posing serious risks to both equipment and personnel. Some key characteristics and consequences of an internal arc fault include: 

• Extreme energy release: Arc power can reach up to 40 megawatts, comparable to the output of a small power plant. 
• Ultra-high temperatures: The arc plasma can exceed 20,000 °C (35,000 °F) – hotter than the surface of the sun. 
• Rapid pressure buildup: Within milliseconds, the internal pressure in the switchgear enclosure can spike, potentially rupturing panels or doors. 
• Intense light emission: The arc produces light levels over 2,000 times brighter than a typical office environment, which can cause temporary or permanent eye damage. 
• Severe acoustic stress: The resulting sound pressure can exceed 140 decibels, comparable to a jet engine at takeoff, with risk of hearing loss. 
• Explosive byproducts: The arc releases not only heat and pressure but also plasma, metal fragments, and toxic gases, making it a compound hazard. 

ABB’s Ultra-Fast Earthing Switch (UFES) is an advanced protection device designed to drastically reduce the damage and danger caused by internal arc faults in low- and medium-voltage switchgear. It serves as an active arc fault mitigation system, operating much faster than traditional protection devices. The operating principle of UFES goes as follows: 

• Continuous monitoring: The UFES system uses current transformers (CTs) or current sensors in conjunction with optical arc flash detectors to continuously monitor for early signs of an arc fault. 
• Ultra-fast activation: When an arc is detected, the UFES controller triggers the device in less than 1 millisecond – faster than the arc can fully develop. 
• Immediate earthing (grounding): Upon activation, the Primary Switching Elements (PSEs) create a low-impedance path to ground in less than 1.5 milliseconds. This effectively diverts the arc energy away from the fault location. 
• Fault extinguishing: By grounding the fault current  in less than 4 milliseconds for the entire operating sequence, UFES eliminates the arc before it can reach full intensity. This prevents the destructive effects typically associated with internal arc events – extreme heat, pressure, light, sound, and toxic emissions – effectively protecting equipment and personnel. 

ABB’s UFES offers a powerful and proactive approach to internal arc fault protection, delivering several key benefits that enhance both safety and system performance: 

• Maximum personnel protection: By extinguishing arc faults within milliseconds, UFES drastically reduces the thermal, acoustic, and pressure impact on operating staff and nearby personnel. 
• Minimized equipment damage: The rapid grounding of fault energy prevents severe damage to switchgear, reducing the risk of costly repairs and extended downtime. 
• Increased uptime and operational continuity: Fast arc suppression helps avoid long interruptions in power supply, supporting higher system availability – especially important in critical facilities. 
• Applicable in new and retrofit installations: UFES can be installed in both greenfield projects and existing switchgear, offering flexibility for system upgrades. 
• Compliance with arc fault protection standards: Helps meet or exceed internal arc classification requirements defined by IEC and ANSI/IEEE standards. 
• Supports sustainability and energy efficiency: By preserving equipment and reducing unplanned outages, UFES contributes to longer asset life cycles and more stable power distribution. 

ABB’s UFES is designed with ease of operation and maintenance in mind. While it performs an extremely fast and technically advanced function, its integration and upkeep are straightforward for qualified electrical personnel. 

Ease of operation: 

• UFES operates automatically in response to arc detection, with no need for manual intervention during fault events.
• It integrates seamlessly with standard protection systems and switchgear automation, ensuring intuitive coordination within existing infrastructure. 

 Ease of maintenance: 

• Modular design allows for quick replacement of the Primary Switching Elements after operation, with minimal downtime. 
• Maintenance procedures follow standard best practices and require no special tools or operator qualifications beyond those used in conventional switchgear service. 

ABB’s UFES and arc-resistant switchgear both aim to address the risks of internal arc faults, but they do so in fundamentally different ways – and in many cases, UFES offers an important advantage.  

Arc-resistant switchgear is designed to contain the effects of an arc fault after it occurs. It uses reinforced enclosures, pressure relief channels, and other passive measures to direct hot gases and fragments safely away from personnel. While effective, this approach still allows the arc to fully develop before it is cleared, which means a significant level of damage, heat, and downtime are often unavoidable. 

In contrast, ABB’s UFES is an active arc fault mitigation system that detects the early signs of an arc and extinguishes it almost instantly – within less than 4 milliseconds. Instead of merely containing the explosion, UFES prevents it from escalating, offering far superior protection for both equipment and personnel. 

What makes UFES especially practical is that it can be installed in both new and existing switchgear systems. It is designed with flexible integration in mind, making it ideal for brownfield retrofits where upgrading to arc-resistant switchgear may be physically or financially impractical. With proper planning, UFES can often be added to existing panels, providing a major safety upgrade without requiring full equipment replacement.