This question / discussion comes up quite often.

The working distance is defined by NFPA 70E as the distance between a person’s head and chest area and a prospective arc source.

IEEE 1584 has a similar definition: The distance between the potential arc source and the face and chest of the worker performing the task.

Even though the definition is straight forward, there can be confusion. Table 10 of IEEE 1584 lists “Typical Working Distances� which are often used for arc flash studies and are listed on the arc flash equipment labels. However, the “Typical� values may not be suitable for all tasks at a given piece of equipment. Is the person racking in a circuit breaker or are the performing voltage testing – two different distances could result.

The IEEE 1584 "typical" values can be summarized as:
Medium Voltage Equipment: 36 inches
Low Voltage Power Equipment: 24 inches
Low Voltage Distribution Equipment: 18 inches

This week’s question is about what working distance is used.

What working distance do you/clients use?
- IEEE 1584 values
- Something else
- It depends