What means existing situation? 

This step ends first part of arc flash analysis. It is called existing or as built situation as it provides information’s about incident energies and arc flash boundaries of current situation without any improvements. It is important to identify existing situation because: 

• it allows installation owner to act fast and provide temporary solutions to prevent staff from arc flash if necessary 
• implementing recommendations can take some time even counted in years, depending on size of facility, so existing results will serve as a base 
• it is a reference point for comparison of results and providing recommendations  

What standards to follow? 

We prepared base model, and now it is necessary to add arc flash related data and parameters. It is worth to mention that we are focusing on incident energy calculation and not table method. (see NFPA70E for details). Possible calculation standards and reference papers are: 

• IEEE 1584 – 2018 IEEE Guide for Performing Arc-Flash Hazard Calculations (worldwide) 
• DGUV Information 203-077 (Germany) 

Since I am focusing on European customers or locations it is also recommended to follow EN/IEC/CENELEC/VDE/BS specific standards to align our results more with IEC: 

• IEC 60909 – Short-circuit currents in three-phase a.c. systems – Part 0: Calculation of currents 
• IEC 61660 – Short-circuit currents in d.c. auxiliary installations in power plants and substations – Part 1: Calculation of short-circuit currents 
• IEC 60076 – Power transformers – Part 1: General 
• IEC 61439 – Low-voltage switchgear and controlgear assemblies – Part 1: General rules 
• IEC 62271 – High voltage switchgears 
• Local references for protection (if any) 
• IEC 60364 – selected parts  
• BS 7671 – 18th Edition The IET Wiring Regulations 
• NEN 3140/3840 
• VDE 0100 series 
• Etc. 

What Arc Flash is about? 

Our goal is to identify incident energy for modelled installation. I am writing modelled as it depends on scope of work, and sometimes it will be only part of the whole system. The most dangerous effect of an arc flash incident is tremendous temperature up to 19000 °C. This what arc flash calculation is all about. To identify how much energy can possibly be released and allows us to think in advance how to protect our life and do it the right way. 

Few words about calculation 

In most cases it will be done acc. IEEE 1584-2018 but depends on voltage level, AC or DC there are some very useful papers recommended in NFAP70E, IEEE 1584 or by equations by EPRI, ArcPro and tables by OSHA. Into this we will dive in next articles. 

How to present results? 

We have now arc flash results of our facility model for existing situation. How to present it? What to comment? To keep quality of our work it is recommended to give even brief explanation of results. Technically it is a bridge between existing situation and our future recommendations.  Depending on software or data processing tools we can present results in many forms. My recommended combinations to keep it simple and easy to read are:

• Single Line Diagram(s) – overview with Arc Flash results, e.g. Incident energy cal/cm2, AF boundary and/or AF label number (in PDF, dwg) 
• Arc Flash table – summary with all results worst scenario and/or per scenario if required 
• Colour coding – advised to use it SLD’s and tables as it is easy to find locations with higher energies (depends on how we set up colours but recommended is to follow NFPA70E) 

Some examples: 

Or by table: