When performing an arc flash study, often one of the goals is to provide recommendations to reduce the incident energy below some value such as 8 cal/cm^2. This can sometimes be accomplished by methods such as changing protective device settings, maintenance switches, alternate protective schemes, remote operation etc. The list goes on.

This weeks question:

Has your company / client used methods to reduce the prospective incident energy / arc flash hazard?

• Yes
• No
• We are thinking about it

As always, comments are encouraged.

One problem I've found with outside consultants is a tendency to just want to run the numbers and not even bother looking at the results. Simultaneously there's a tendency internally to just accept the results at face value in house and not pay any attention to the consequences of those decisions.

I am an outside consultant that has spent that majority of arc flash study time working with system protection settings or distribution system configurations to achieve workable results. I agree with Paul that this is often overlooked.

An unexpected benefit of such work is consistency and reliability improvements achieved by normalizing equipment arrangements, sizing and protective settings. Prior to arc flash analysis it seemed any 'flavor of the week' was acceptable causing very mixed results.

We have 17 stone aggregate quarries and have strived to keep all arc flash hazards below 8 cal/cm2. At each location during the arc flash analysis, we have found one or more instances where we exceed 8 cal/cm2 and need to do some mitigation. We have changed fuse sizes and types, adjusted CB settings, split loads to multiple transformers etc. We have been successful in mitigating all but a select few, which enables our electrical techs to be safe in class II arc flash clothing. One extra benefit of the arc flash analysis work has been raising the awareness of all the techs and plant personel so that the amount of hot work that is performed is much much less then 10 years ago.

We are working on arc flash mitigation. I am new to arc flash issues. Our toughest problems are old MLO switchboards. As I understand it, device settings mitigate load side only. Device settings help load side, but for many places the older breakers do not have enough adjustment and some switchboards have fused switches. Line side connections can only be mitigated by engineered mechanical methods? I am pushing for more engineered mitigation (barriers, etc.).

Upstream adjustments.

Yes. The specific application I had in mind was utility owned equipment upstream. If we are providing the upstream equipment (greater than 600 volt) we can address the arc flash mitigation methods upstream.

Ron that would work. What would happen if the utility company changes their upstream distribution configuration? I dont believe there is a procedure requiring the provider to keep its client informed of any changes. This could affect your arc flash results in the future.