Safety Devices

These devices are mainly effective for general electrical work and may not prevent an arc flash incident from occurring.

Warning Indicator Light

For safety, all metal on machines should be tied to ground (a wire fastened from the metal to a copper rod driven into the earth). Thus, if a wire should come loose/break and touch any metal surface, current will flow (be shorted) to ground, tripping a safety device in the cabinet. If the metal parts of a machine were not tied to ground and a "live" or "hot" wire were to touch the metal, then the machine would become "live". If a person were to touch the machine, they would complete the circuit to ground (through their body) and could be electrocuted.

Some electrical panels are equipped with ground indicator lights:

  • Dimly lit Indicator Lamps indicate that the circuit is properly grounded.
  • A possible ground fault problem exists if:
    • One Lamp is bright and the other is dim or out, indicating that the circuit is going to ground somewhere outside the panel.
    • Both lights are out.

 

Current Limiting Fuses/Circuit Breakers

Current limiting fuses and circuit breakers, when operated in the current limiting range, operate extremely fast to reduce the arcing current and diminish the energy levels produced.

  • Only help mitigate hazard if current is high enough to blow or trip.
  • Do not mitigate the duration (cycle times) of arc flash.

 

Ground Fault Circuit Interrupters (GFCI)

An electrical wiring device that disconnects a circuit whenever it detects that the flow of current is not balanced between the phase ("hot") conductor and the neutral conductor.

  • The presumption is that such an imbalance may represent current leakage through the body of a person who is grounded and accidentally touching the energized part of the circuit.
  • A shock, possibly lethal, is likely to result from these conditions; GFCIs are designed to disconnect quickly enough to prevent such shocks.

 

In NFPA 70E 21015 Article 110.4(C)(2) Maintenance and Construction (GFCI) Protection:

  • GFCI protection provided for operating or using tools related to maintenance and construction activity 125-volt, 15-, 20-, or 30-ampere circuits.
  • Greater than 125-volt, 15-, 20-, or 30-ampere circuits either GFCI protection or an assured equipment grounding conductor program.

When to Use

Ground fault circuit interrupters should be used any time electrical equipment is used around moisture. This would include the use of electrical power tools outdoors or in damp locations.

How to Use:

  • Before use, test and reset to verify proper operation.
  • Always follow manufacturer's recommendations.

 

Infrared Scans

Infrared cameras are one of the tools used to identify problems in electrical systems by detecting the IR wavelengths generated by heat. An infrared camera can be used to identify a failing component prior to a complete failure which can cause electrical system shutdown, equipment damage and bodily injury. Although they can be used to inspect electrical components at a distance, they do require a direct line-of-sight to record accurate images which often requires a qualified worker, wearing appropriate PPE and trained for the task, to open the enclosure to gain access.

Infrared Window

An infrared window installed on an electrical cabinet or panel may eliminate the risks of performing a live inspection it allows the infrared camera a direct line-of-site access to the interior components without having to open the enclosure. This provides an safe alternative to having a qualified person open doors or remove access panels, a source of triggering an arc flash event.

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Figure 1: Ground Indicator Lights on Electric Panel

 

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Figure 2: Class J Fast Acting Current Limiting Fuses in AMTEC Simulator Electrical Panel

 

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Figure 3: Panelboard Mount and Portable GFCIs

 

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Figure 4: Using Infrared Device to Troubleshoot at a Distance

(workers may use FR level clothing outside the Limited Approach Boundary)