of new equipments and technologies for arc flash reduction
Proper rigorous arc flash hazard studies, labeling, and use of appropriate PPE
Adherence to safety codes, standards, and recommended practices
Remote operation, avoiding human machine interface to avoid human errors during routine operation
Remote racking of circuit breakers
1.15.1 Reduction
The protection system, coordination and suitable selection of additional protective devices can reduce the arcing times. Examples are differential protection, light sensing supervised by current signature, zone interlocking, arc flash maintenance switches which bring alternative relay settings into operation.
In some cases the arc fault current can be low resulting in increased fault clearing time. For example, the fault on the secondary side of a transformer, which is used by the transformer primary protection device. Due to ratio of transformation this current will be reduced resulting in prolonged clearing time. A secondary protective relay can be applied which will transfer trip primary proactive device.
Well-planned procedures, work practices and training can avoid arc flash hazards. Remote racking, remote control panels for switching, supervisory controls can help worker for safe operation from a distance outside the arc flash boundary. Infra-red windows, partial discharge sensors can be very helpful diagnostic tools.
Arc-resistant equipment can be used.
TABLE 1.14. Measures to Protect Against Arc Flash
| Mitigation | Type | Advantages | Disadvantages | Recommendations |
| Compartmentalization (IEC type-4b or ANSI equivalent barriers and boots | Prevention | Reduces the likelihood of arc flash by compartmentalization and insulating energized parts | Equivalent to a guard on a saw. Hazard is still present. Maintenance and testing may require exposure to energized parts | It does not reduce the energy available, it does reduce the probability of a fault. Compartmentalization or change incident energy calculation. |
| Arc-resistant equipment | Containment (passive) | Protects the worker by directing energy away from the worker when required covers are on. Tested per IEEE Std. C37.20.7 | Maintenance and testing may require removal of covers. Equipment is exposed to damage and has a larger footprint. May require second migration means to stay within rated arcing duration especially at LV | This measure offers protection for specific tasks, but does not reduce available energy. This measure is recommended where active mitigation methods are not acceptable. |
| High-speed shorting switch | Active (reduction) | Fights fire with fire. Re-directs arc flash energy into the bus by creating an intentional bolted fault; may use optical, differential and current waveform recognition. | Unconventional method and requires additional equipment. | May qualify as arc resistant per IEEE Std. 37.20.7. Needs robust controls to minimize chances of nuisance operation. |
| ZSI (blocking schemes) | Active (reduction) | Communication-aided transfer trip scheme that reduces breaker trip time and amount of energy released | Requires communication wiring between breakers. Trip units or relays must be installed with ZSI capability | Recommended for LV applications. Also available with some MV relays. |
TABLE 1.15. Matrix of Sample Arc Flash Mitigation Measures
| Technology | Arc-Flash Mitigation | Incremental Commissioning Complexity | Protection for Intentional Exposure | Protection for Incidental Exposure | Foot-print | Capital Expense | Operational Expenditure | Equipment Survivability | Arc Flash Incident Energy Reduction | Typical Application |
| Prevention | Barriers | Low | Limited | Limited | No change | Low | Low | Moderate impact | None | LV switchgear switchboard |
| ANSI compartmentalization | Low | Limited | Limited | No change | Low | Low | Moderate impact | None | LV switchgear switchboard | |
| IEC-4b compartmentalization | Low | Limited | Limited | No change | Low | Low | Moderate impact | None | LV switchgear switchboard | |
| HRG | High | Limited | Limited | Increased | Medium | Low | Moderate impact | SLG fault only | 480V to 5 kV | |
| Shielding barriers | Low | Limited | Limited | No change | Low | Low | No impact | None | LV arc-resistant switchgear | |
| Adm. controls | N/A | Limited | Limited | No change | Low | Low | No impact | None | All, training requirement | |
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Containment
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