Safeguarding the well-being of your technicians while working on live electrical equipment demands the implementation of arc flash mitigation measures. As stipulated by the 2020 National Electrical Code, Section 240.87, these protocols are mandatory for circuit breakers rated for or adjustable to 1200 A or higher. This article delves into various approaches to align with this specific code and ensure compliance.
Ensuring the absolute safety of your technicians from potential arc flash incidents necessitates the complete de-energization of the equipment they work on. With energized equipment, the risk of arc flash is ever-present. Instances where work can’t be executed on de-energized equipment (e.g., current testing), or when de-energizing poses greater public health risks, require a live work permit in accordance with OSHA standards.
Lock Out Tag Out (LOTO) Procedure
Even with equipment de-energized, the potential for accidental reactivation during maintenance remains. Employing a meticulous lock out tag out procedure becomes paramount in this context. This procedure entails six vital steps:
- Preparation: Thoroughly assess all types of hazardous energy that may govern the equipment.
- Shutdown: Turn off or shut down the equipment, informing affected personnel.
- Isolation: Isolate the equipment from all energy sources.
- Lockout/Tagout: Securely lock and tag the equipment to prevent transition from safe to unsafe mode, except by the individual executing the lockout. Attach the tag.
- Stored Energy Check: Neutralize or disconnect any hazardous stored or residual energy.
- Isolation Verification: Double-check the equipment’s status, ensuring disconnection from power sources, proper locking/tagging, and resolution of stored energy issues.
Releasing LOTO requires the initiator to confirm the safety of the workplace, remove personal LOTO devices, and inform relevant personnel before re-energizing the equipment.
Precise Instantaneous Override
Most circuit breakers possess a manual override for instantaneous trip settings. These settings should be adjusted to a level lower than the anticipated arc fault current. Determining the arcing current and trip curves for your device aids in setting this threshold. While many breakers arrive at sites with minimal settings, which may cause nuisance tripping due to power surges, adjustments for higher settings risk losing the “instantaneous” aspect and non-compliance with NEC Section 240.87. As a result, other methods of arc flash mitigation are often preferred.
Zone Selective Interlocking (ZSI)
ZSI involves communication between two or more circuit breakers to clear a short circuit or ground fault with minimal delay, reducing incident energy. Although slightly slower in response, ZSI offers a valid option.
Arc Flash Reducing Maintenance Switching (ARMS) with Local Status Indicator
ARMS empowers technicians to accelerate circuit breaker operation during an arc fault within the arc-flash boundary, without affecting preset settings. This switch overrides normal settings only during live work, ensuring compliance without compromising performance.
Differential relays trigger when there’s a notable difference in phasor values of similar electrical quantities, promptly interrupting upstream power to minimize arc flash risk.
Energy Reducing Active Arc Flash Mitigation System
This system briefly interrupts or diverts current flow to minimize arcing duration, enhancing upstream circuit breaker responsiveness. Despite being costlier, it’s an effective option for energized work.
Approved Equivalent Means
This open-ended provision acknowledges evolving technologies and alternative approaches. Local Authorities Having Jurisdiction (AHJs) decide compliance, fostering diligence in electrical inspection.
Validating an arc energy protection system through performance testing upon installation ensures it functions as intended, upholding safety during arc flash events.
Prioritizing technician safety and code compliance is paramount. Energy Management is dedicated to providing ample resources to ensure employee well-being and facility security.