What Is Arc Flash and Why Is It Dangerous?

Let’s be honest: the risk of arc flash is still widely underestimated or misunderstood. When people hear the term electrical hazard, they often think only of electric shock. While electric shock
is undeniably dangerous, arc flash represents a completely different—
and often more devastating—threat. Unlike shock hazards, an arc flash
can release an enormous amount of energy in a split second, exposing
workers to extreme heat, explosive pressure, and molten metal. For anyone
working in the electrical industry, electrical maintenance, electrical
safety, or related fields, misunderstanding or overlooking the danger
of arc flash can have severe or even fatal consequences.

Electrical hazards are present in our daily lives, so it’s crucial to
be aware of them and take the necessary precautions to ensure we get
home safely from work.

The aim of this article is to explain how arc flash risk assessment
process looks like, from the initial contact to installing label on the
electrical panel door. But before we get into the process, let’s make
sure everyone understands what it’s all about.

Electrical Hazards vs Electrical Risk – Key Differences

These terms may sound similar, but for those who regularly work in the
electrical sector, it’s essential to know the definition. An electrical hazard is the source of the potential to cause harm, for example, damaged equipment that could cause a short circuit or an arc flash. On the other hand, an electrical risk is the likelihood and severity of
harm when a person is exposed to an electrical hazard.

Types of Electrical Hazards in the Workplace

When it comes to electrical hazards, the list is longer than we think.
Below are some examples of electrical hazards:

• Electric shock
• Arc flash hazard
• Arc blast
• Electrostatic discharge
• Electrical fires
• Electromagnetic field exposure
• Explosions in Ex areas
• Burns from hot surfaces of energized components
• Induced voltage
• Battery fires and explosions

Arc Flash: Real Risks, Real Costs

Most of the safety training focuses on shock hazards. Arc flash often gets only a slide,
maybe a warning label without important information, sometimes just a sticker for electric shock, and then everyone moves on. That’s a problem—because in terms of raw destructive potential, arc flash is in a completely different category.

Here are some numbers that tend to attract people’s attention:

An arc flash is not just an electrical fault but a violent arc flash phenomenon—a rapid, uncontrolled release of energy that resembles an explosion more than a typical electrical hazard. In milliseconds, temperatures above 19,000 °C, roughly 15 times hotter than volcanic
magma, can vaporize copper and force it to expand tens of thousands of times its original volume.

This sudden expansion generates powerful pressure waves capable of knocking workers to the ground and hurling molten metal at extreme speeds, while intense thermal radiation causes severe burns without direct contact. Blinding light, deafening noise,
and clouds of superheated gases and metal vapors further compound the danger. Unlike electric shock, proximity alone is enough to underestimate this phenomenon means overlooking one of the most destructive hazards in electrical work.

And the costs aren’t just human. A few real-world examples

• OVH SBG1 — arcing fault in a UPS battery room: €105 million loss
• Ocado warehouse, Andover UK — battery charger fault: £110 million damage + £132k fire-fighting costs
• Notre-Dame Cathedral — officially attributed to an electrical fault: €552 million reconstruction cost

The point isn’t to terrify anyone. It’s to establish that this is worth
doing properly.

Hierarchy of Controls in Electrical Safety

Hierarchy of Controls is a safety framework used to reduce or eliminate exposure to hazards in the workplace. It ranks control measures from the most effective to the least effective, helping organizations prioritize solutions that provide the highest level of protection.

Working from most effective to least effective

1. Identification: We could say that the first step is to identify the risks in the workplace. Once electrical hazards are recognized, the next step is to reduce or eliminate them through engineering controls. However, personal protective equipment is still mandatory. The question is how to correctly understand and apply this process in the workplace.
2. Elimination: No live work. LOTO. Arc quenching devices. If you can de-energize it, de-energize it. This is always the preferred option.
3. Substitution: Lower operating voltage. Arc-resistant switchgear. If you can change the system to reduce the inherent hazard, do it at design stage.
4. Engineering Controls: Physical barriers. Remote operation. Isolating people from the hazard spatially. Things that don’t depend on human behavior to work.
5. Awareness: Arc flash labels. Training. People need to know the hazard exists and understand what the labels mean. This is necessary but not sufficient on its own.
6. Administrative Controls: Electrical safety plans. Work instructions. Written procedures for how tasks get done safely.
7. PPE: The correct arc-rated clothing and equipment for the calculated incident energy. Essential, but it only protects the person already exposed to the hazard.

A good arc flash study informs all of these levels, not just the PPE selection.

In conclusion, when an employer implements all elements of the Hierarchy of Controls, the level of risk can be significantly reduced or even eliminated. As a result, the tasks performed by employees transition from relying on the least effective protective measures to the most effective and safest controls, leading to a substantially safer work environment.

How is it understood in the workplace?

In practice, many workplaces are familiar with PPE and administrative controls because they are easier to implement. However, higher-level controls such as elimination, substitution, and engineering controls are often underestimated or overlooked due to cost, design constraints, or lack of early planning.

Do people know about it?

While the Hierarchy of Controls is widely recognized in safety standards and professional guidance, not everyone truly understands or applies it correctly. In many cases, it is treated as a theoretical concept rather than a practical decision-making tool. Improving awareness and
application of the hierarchy is essential for managing high-energy hazards such as arc flash effectively.

Key Arc Flash Standards (NFPA 70E, IEEE 1584, OSHA)

Regarding arc flash performance, it is necessary to be familiar with and apply the relevant standards; the most important ones are listed below:

Standard	Description
NFPA 70E (2024)	Standard for Electrical Safety in the Workplace
IEEE 1584-2018	Guide for Performing Arc-Flash Hazard Calculations
IEEE 1584.1-2013	Guide for the Specification of Arc-Flash Hazard Calculations
CSA Z462-2024	Workplace Electrical Safety
EPRI TR-2011	Arc Flash Hazard Analysis Methodology
OSHA 1910.269 Appendix E	Protection From Flames and Electric Arcs
DGUV 203-077	Selection of Personal Protective Equipment for Electrical Arc Hazards

Supporting standards for the short-circuit side: IEC 60909 (general), IEC 61363 (marine and offshore). ANSI, IEEE, EN, BS standards as appropriate to the system being studied.

It is important to clarify that each country has its own standards. In general, some approach limits and protection zone requirements may change according to national regulations; however, the calculation methodology is usually the same as, or based on, IEEE 1584-2018.

Step-by-Step Arc Flash Risk Assessment Process

Here is how a proper arc flash risk assessment gets done.

Step 1: Customer meeting:

Before initiating any analysis or field visit, it is essential to clearly define and fully understand the project scope. This requires close collaboration with the client to determine the project size, identify the applicable standards, and collect all critical information necessary
to prepare an accurate and effective offer.

Step 2: Data Collection:

Before conducting an on‑site visit for data collection, all available technical information should be reviewed, and the data‑collection format prepared. During the field visit, relevant data is collected accurately, and a safety inspection is carried out. The findings are then documented in a site report that includes observations, analysis, and safety recommendations aimed at improving workplace safety.

Step 3: System Modelling:

Develop a digital twin of the electrical network using specialized software that accurately reflects the actual installed system. The electrical model shall be created with comprehensive and precise details to ensure it faithfully represents the real-world configuration, equipment
characteristics, and operating conditions.

Step 4: Electrical Analysis Calculations.

Performance an Electrical Analysis calculations based in all standards:

• Short Circuit Analysis. IEC 60909 /ANSI
• Short Circuit Equipment Evaluation
• Selectivity Analysis to find protection issues for exiting situation and provide recommendations for improvements for future adjustments
• Arc Flash Analysis – for existing situation acc. IEEE1584 -2018 / sometimes DGUV203-077, provide recommendations for improvements for future adjustments.

Step 5: Report:

The final report includes all results, analysis tables for existing and recommended situations, different scenarios configuration, recommendations, modeling data, single‑line diagrams, and equipment labeling information, compiled and delivered in appropriate formats such as Word, PDF, and Excel.

Step 6: Customer Meeting:

It is essential to hold a meeting with the client to review the report results, discuss identified issues within the electrical installation, and present the proposed recommendations developed in accordance with the Hierarchy of Controls.

Step 7: Training:

Provide technical training on arc-flash hazards, preferably conducted on-site, with online delivery as an alternative. The training covers hazard identification, arc-flash warning labels, proper selection and use of personal protective equipment (PPE), and methods to reduce or eliminate risks through engineering controls, in accordance with the report findings.

Step 8: Final & follow up:

Overall, periodic revisions should be carried out, with results updated at least every five years or following any significant modifications to the electrical system. This process may include retraining workers and updating or replacing equipment warning labels as necessary.

Why it is important for us to do review? 

Recommendations as per IEEE 1584.1 should be included in Arc Flash Risk Assessment. It requires evaluating project, implement recommendations, re-do calculation. Physically, it should be a separate part or chapter in our report, so end customer can see influence or our proposed improvements. Sometimes our improvements in one area may affect negatively other parts of the electrical network. This often happens when an electrical system has a lot of non-selective protection devices. 

Step #9 is not a real step. Results review is constant activity during project. It is needed to : 

• Review any data quality issues and abnormal results or errors
• Identify high incident energy locations
• Identify equipment short circuit withstand rating failed equipment (panels, breakers, etc.)
• Identify protective devices non-selective operation (very important) 
• Identify worst case scenarios or combination of it

What’s next?

Once we have it done, we need to review arc flash results and protective device coordination and assess possibilities for improvements. This is where things are starting to get more complicated. There are multiple ways to do it and it partly depends on: 

• What we would like to achieve (zero risk, reasonable approach, or budget approach) 
• What was scope of work (contract details) 
• How far we can go with recommendations (budget, technical possibilities, equipment in use)

This is a good time to have a technical meeting with customer to discuss initial findings and identify technical possibilities if it was not done earlier during scope of work discussion. To improve the situation, we can use different mitigation and elimination arc flash techniques. It usually depends on initial incident energy results and combination of solutions mentioned below. All of this should be closely discussed with customer. 

What possible solutions do we have? 

Most common solutions to reduce or eliminate arc flash incident energy are: 

• Improving protective device settings – this is usually a big step as it is compromise with selectivity study, so two (usually opposite)  requirements at the same time. 
• Exchange protective device to new type e.g. retrofit old LV breaker with new type with digital trip unit, change fuse size/type, exchange MV protection relay with digital type.
• Exchange/ retrofit LV switchgears with new type –  it may be higher separation form, arc resistant, and it will allow for further modifications.  
• Install Fibre Optic Arc Detection system – add-on to switchgear, requires some re-wiring, but most of the time is possible even for old equipment (depends on system).
• Install Arc Quenching device –  add-on to switchgear (extra panel) or comes with new switchgears if system is replaced. 
• Use ZSI (Zone Selective Interlock)  in LV breakers – requires communication wires between breakers and requires new trip unit  (sometimes trip unite change is enough in LV breaker, depends on type).
• Use ARMS (Arc Flash Maintenance Switch) function – extra functionality of some LV breaker trip units, simple solution with right trip unit. 
• CLR (Current Limiting Reactors) – specific topics, as it can make it better and worse when reducing short circuit current.  
• Programmable Maintenance Switch for MV relays –  MV version of ARMS programmed into relay with some minor wiring needed for activation by SCADA, LOTO switch etc. 

How long it takes and how to handle it on site? 

Preparing recommendations takes time, but it is well spent time. As IEEE 1584.1 recommends, it should be part of every arc flash study. 
Once we have report with information what to do, we need to implement it on the site. Improvement process can take weeks, months, or even more than a year as it depends on the size of facility.  Since this process can take a while, it is good to already use our ”existing” results and install labels and match PPE based on it.  
Upgrades or protective device settings changes should be done exactly as proposed in report. Otherwise, we can end up having different calculated results than in real situation.  Every change should be noted and evaluated as part of “as built” documentation and any changes should be implemented in the model and results updated. 

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:

What is Equipment Evaluation? 

Equipment evaluation, equipment sizing or device withstand rating verification is based on short circuit results. It verifies if short circuit rating of electrical equipment is high enough comparing to calculated short circuit current. Such calculations should be normally included in design phase however for existing installation it is recommended to verify it, especially when there is no previous design report available. 

Why is it important?

Proper sizing of equipment is crucial for safe operation under normal and faulty conditions. Cables, switchgears, breakers, transformers are design to withstand specific short circuit current in time. For proper operation of the breaker, it is critical that the breaker can withstand specific currents. If it is undersized, it can lead be damaged and pose threat to people and rest of electrical installation. 

How this relates to Arc Flash? 

It is included as a recommended step in IEEE 1584. Besides this, it is important to know that our equipment withstand rating is related with performance under fault conditions and normal operation. Constant overload or dynamic stress can cause damage to it and affect proper operation. This can lead to nuisance tripping, no tripping, thermal damage or fire etc. We can select worst case scenario out of multiple scenarios, however for experienced engineers it is easy to identify it. 

Example: 
We have low voltage switchgear rated 2000A 50kA/1s 105kA peak. If we do not know peak value, it is good to check in IEC 61439 table 7 for details.

We calculated two values in two scenarios: 

1. Ik” ≈Ith=46,45kA and Ip=100,5kA it is at the end of rating but can be accepted. In practice, it is good to keep 5-10% safety margin. 

2. Ik” ≈Ith=53,38kA and Ip=119,44kA – this switchgear rating is too low, and we need to look for higher short circuit rating or verify short circuit study input data first.  

When comparing short circuit results with different equipment, IEC 60909 comes with help and indicate which values to compare: 

Summary of equipment evaluation using SKM Power Tools

Below is an example of summary of equipment evaluation for switchgears and panel boards made with use of SKM Power Tools in this case. It can look different for other software’s like ETAP, CYME, EasyPower, DigSilent however core values should be similar. Such verification gives a very useful overview and directly indicates possible rating issues.  

In specific cases it is necessary to verify X/R or R/X of network and network time constant if not known as it affects results. Especially when local generation exists on site, This is very visible in marine and offshore installations. We need to keep in mind also renewable sources, battery storage systems, (DR) UPS-es with bypass in our calculations.

What Is Selectivity Analysis in Arc Flash Studies? 

It can be also called Protective Device Coordination (PDC), Selectivity Study, Discrimination Study. It is usually mandatory analysis for new electrical installations but also applies for upgrades, retrofits, or major electrical installation modernizations. Protective Device Coordination is a proper selection and settings of protective devices in order to isolate only faulted branch or place. If made properly, it will limit damage to installation itself and connected devices. A very important part of Selectivity Analysis is to eliminate fault as close as possible to the source of fault without affecting operation of the system. 

Why Is Selectivity Analysis Important for Arc Flash?

Non-selective protection system can increase damage to the equipment, extend and expand downtime and costs related. In some cases it can lead to dangerous situation especially related with safety   like fire, shock hazard, automatic disconnection or arc flash etc. In some cases it may not react at all, and obviously we don’t want it. 

How Does Selectivity Analysis Affect Arc Flash Results? 

Arc Flash calculation requires us to determine protective device tripping time.  In previous steps, we already modelled all necessary protective devices like: 

• LV fuses 
• LV breakers (ACB, MCCB, MCB) 
• MV breakers with protection relays (electromechanical, digital) 
• MV fuses 
• and specific protection schemes like differential protection, fibre optic arc detection, arc quenching devices, arc flash reduction maintenance switches, etc.

Arc flash and selectivity requirements are usually contradictory, and it requires compromise in some situations. In order to lower arc flash incident energy, tripping time need to be as low as possible (faster tripping). On the other hand, standard selectivity requirements are pushing tripping time higher (slower tripping).  There are hardware solutions that can overcome this problem, but they are not always available or feasible (due to cost, retrofit possibility or technical issues).  

Selectivity and Arc Flash? 

Arc Flash analysis itself doesn’t require the system to be selective, however it is very useful to perform such analysis. This step is important as it allows us later to provide tailor made recommendations for improvements of selectivity and arc flash. Protective device coordination is a much bigger topic, and it is very often omitted in arc flash analysis leading to identification of only existing situation while good practice is to focus on possible improvements. In order to do it right, we need to identify system issues like: 

• wrong settings of protective devices  
• non-selective areas 
• under protected equipment like cables, transformers, switchgears, and motors 

 The best way is to split analysis in two parts: 

• first step is providing information for “as build” or “existing” situation 
• second step is providing recommendations for selectivity and arc flash improvements 

Below sample of two TCC’s for existing and recommended selectivity for transformer branch. 

Selectivity Analysis Findings and Observations 

Left TCC shows a partially selective system, and it can be seen that MV relays are set with definite time settings, which is very common practice. There are few areas which can be discussed here: 

• Overlapping overload LV and MV settings may lead to MV side nuisance tripping, which we don’t want as it will de-energize the complete system and access to MV substation may be restricted or not possible. 
• MV and LV side transformer cables are not protected properly against short circuit currents 
• Transformer short circuit protection can be improved for primary and secondary faults 
• Overall arc flash results for 11kV and 415V switchgears can be improved  

Arc Flash Results Comparison – Existing vs Recommended 

Component	Existing IE cal/cm2	Recommended IE cal/cm2
BUS-11kV	18.2	6.18
BUS-LV 415V	11.1	2.4

 
It needs to be noted that in some situations it is a compromise. This means that in order to improve arc flash results, we will sacrifice selectivity and vice versa. This doesn’t happen very often and nowadays, we can use communication based protection solutions, interlocking schemes, arc flash maintenance switches to name a few.   

Practical System Modelling

Once our model is ready, we can create short circuit scenarios. This depends on system, but most often in Europe we will use IEC 60909 or local harmonised versions.  Since we know that our focus is on arc flash analysis, equipment evaluation and protective device coordination, we need more than one scenario.  

For a simple industrial system, this will require creating at least two scenarios: 

• Minimum short circuit current  (Utility min short circuit power, no motors etc.) 
• Maximum short circuit current (motors contribution, C=max, etc.) 

For complex systems, multiple scenarios are needed due to possible system configuration. This involves:

• Parallel source operations (PV, Generator, Utility) 
• Parallel transformers (closed or open tiebreaker) 
• MV ring operation (open or closed) 
• Motor contribution (big motors separately modelled, VFD with bypass etc) 
• Generator mode (emergency operation, normal operation) 
• UPS mode (bypass or normal) 
• System specific configurations (Open, closed breakers, test lab modes etc) 

Short circuit results depends on all of those factors. Additionally, it makes difference if we calculate fault close or far from generator which is affected by AC decaying component.  IEC 60909 representation gives clear overview of this behaviour. 

Short circuit analysis will be used to identify worst cases. This means minimum and maximum short circuit currents.  Results of this study will be used for further calculations, so it is important to validate it. 

How results can look like? 

It can be summarized in table which helps to find right data. Additionally, it is nice to show partial results on a single line diagram (keep it readable). Some examples below:  

As mentioned earlier, it could be that scope of work contains part of the network and the rest is not included. While this is fully understood from cost point of view, it may have big influence on end results. Since we are looking for short circuit current which will lead to (usually) the longest tripping times and highest incident energy, it is important to be not too conservative. Narrowing analysis to part of installation can end up with not realistic results and over/under sizing PPE, leading to wrong conclusions and costly recommendations. This is something we would like to avoid.  

How we use short circuit results? 

• Equipment evaluation will use maximum short circuit results to compare withstand rating of equipment like cables, switchgears, breakers, transformers etc 
• Protective device coordination (selectivity analysis) require both maximum and minimum, sometimes scenario specific results for protection settings calculations 
• Arc flash analysis requires worst case combination (min, max, etc)  in relation to protection scheme  

Coming back to partial short circuit calculation, It is site specific and requires recommendation from a power system engineer for each project to make it right (see scope of work kick-off discussion).  

Common issues related to short circuit data  

Typical situations: 

• we have previous short circuit study, but it lacks min max values and was too general missing short circuit sources especially generators and motors 
• we don’t have study, but our scope of work is limited, so a big part of the system won’t be included in short circuit study  
• no main transformer data or hard to get (the same for utility data)  
• ring topology with multiple short circuit paths (for large sites) 
• parallel operations for utility and other sources (situation for part of system modelling).

How System Modelling Fits into Arc Flash Analysis

This step is beginning of engineering part. Nowadays, it is common and reasonable to use power system software to perform analysis.  Most common in use are SKM, ETAP, Easypower, DigSilent, CYME and others. It still can be done by hand or with use of Excel, however complexity of electrical systems will make it not efficient and costly. CAE software is a great and helpful tool, but it is only as good as the person that is using it. We need to remember that what comes IN goes OUT. Proper modelling is a must. 

System modelling requires us to establish few areas: 

• System topology and operations modes 
• System prospective short circuit current  
• Equipment data 
• Electrodes configurations (new from 2018) 
• Required scenarios   
• Assumptions  

System topology and scope of work 

Once we collected all the data or enough data, modelling can be started.  It can vary from one software to another, but a common part is to create a digital model as base for further modifications and adjustments. In Step 1 we focused on scope of work and here is why. We can evaluate: 

• complete system (in electrical terms) 
• part of the system  

Complete system study allows to determine multiple scenarios and finding min and max short circuit current. If we evaluate part of the electrical system, we need precise data about short circuit current in the evaluated part. It is very common for short circuit studies to focus only on max values for equipment sizing. The first tricky thing behind arc flash is that max current doesn’t always lead to the highest incident energy. 

Operation modes 

When system model is ready, attention is needed for scenarios, proper standards for calculations and adjusting analysis options. While software generally helps, it is only tool that can be used good or bad.  We are following mostly IEEE 1584 method for calculating arc flash in AC systems. This for European market requires some adjustments: 

• short circuit analysis method acc. IEC 60909 
• busbar gaps to follow IEC 61439 and IEC 62271-1 (recommended) 
• working distance is another topic, however IEEE 1584 standard options are reasonable  

Scenarios

Our base model is ready, so it is time to create scenarios.

We need to keep in mind that our arc flash analysis focus is to identify and provide recommendations for improvements. This means that scenarios need to take into account :

• Short circuit study results 
• Protective device coordination (selectivity) 
• Arc flash analysis results 
• *Load flow study (if included) 

Optionally, depending on our system we can consider: 

• BESS system connected 
• PV/WIND, etc. system connected 
• UPS, RUPS, DRUPS systems  
• CLR (Current Limiting Reactor) in operation 
• Specific switching arrangements (parallel transformers, multiple generators, etc.) 
• Protection specific functions modes (ARMS, arc fibre optic detection, arc quenching devices, differential protection, etc.) 

Equipment and configuration 

Data retrieved from site visit, documentation and provided sources need to be carefully implemented into digital model. Sometimes it requires verification of database and validation of available models for errors. Those issues have different weight, and it is related with installation size.  Most recommended is to use data verified by site visit, especially for settings of protective devices. Electrode configurations are a new topic from latest 2018 release of IEEE 1584, and it will be discusses separately in next chapter. 

Assumptions 

From my experience so far, assumptions are almost impossible to avoid but need to be minimised. This happens because often it takes too much time to retrieve data from: 

• utility operator  
• locations that can’t be de-energised due to ongoing process (sometimes it can take months to get the data) 
• restricted access to locations (eg. transformer rooms or utility switch rooms) 
• old equipment (missing data sheets, etc.) 

Usually some reasonable assumptions can be made based on experience. It is always project specific, but some general assumption list can be made, like: 

• transformer short circuit voltage/impedance rating 
• fuse types and tripping curves  
• low voltage breakers types and settings (similar model based) 
• system short circuit power  (depends on configuration, sometimes it has little effect for end results) 
• induction motors data 
• switchgears and panels ratings 
• cable lengths and type (this is tricky and requires results review).

Arc Flash analysis STEP BY STEP #3

Arc Flash Analysis Step by Step #3: Site Data Collection

Every arc flash analysis requires accurate input data — and site data collection is one of the most critical steps in the entire process. Unlike other power system studies where conservative assumptions are acceptable, arc flash analysis demands reasonably precise data. Why? Because the highest short circuit current doesn’t always lead to the highest incident energies. This is especially important for Low Voltage installations, which are often underestimated compared to High Voltage systems — when in reality, LV hazard levels are frequently higher. 

Why Accurate Data Collection Matters in Arc Flash Analysis

It is important to be accurate when collecting data, and data needs to be based on up to date documentation to reflect existing installation. Very often there is big discrepancy between what is on the drawings and what is in reality. While some facilities maintain documentation very well, others not always. It is very good practice to verify documentation vs as-build reality. This means site visit for data verification and data collection.  Key reason for such decision are: 

• Lack of expertise on site 
• Lack or limited documentation and related difficulties (system mapping) 
• No available staff for arc flash data collection support 
• Independent engineer opinion vs employee  

What Affects Arc Flash Analysis Data Collection?

Every installation is different and data collection also. It depends on: 

• type of business sector e.g. chemical, oil & gas, industrial, automotive, BESS, PV & WIND, marine 
• system size and voltage range (AC, DC, LV, HV, big or small system)  
• available documentation and drawings 
• local support (skilled electrician, engineers, etc.) 

Who Can Perform Arc Flash Analysis Data Collection? 

Since we are talking about low and medium voltage systems, it is required for such person to be certified or authorised electrician or engineer. Data collection can be an elevated risk process since it requires access to electrical switchgears, cabinets and machines. Very often, some covers need to be removed in order to retrieve the right data. It is good to arrange: 

• introduction meeting with technical team 
• provide general plan and if needed to arrange work permits 
• follow site specific safety rules  

 

What Data Is Required for Arc Flash Analysis?

It depends on specific facility profile and amount of documentation, however some general list can be made. If documentation is good enough, It is good practice to prepare a list of all (known) necessary information’s needed. What we can expect to identify and collect: 

• System operation modes  (normal mode, generator mode, emergency, etc.) 
• Utility fault data, three-phase and single line-to-ground short circuit power, X/R ratios at the power delivery point 
• Utility feeder(s) protection settings, relay type, CT ratio 
• All available documentation for old equipment (generators, relays, breakers) 
• Single line diagrams copy (if on paper only), even old are useful 
• Switchgear, switchboards data (short circuit withstand rating, nominal current, busbar gap, dimensions) 
• Cable data, type, length, conductor material, amount per phase 
• Generator data current decrement curves as per manufacturer tests, nameplate data  
• Transformer data, transformer type, winding connection, voltage ratio, rated power, short-circuit impedance (nameplate data) 
• Motors data  >37kW nameplate and control system type (VFD, DOL, SS, etc.) 
• Medium voltage protective relays type, manufacturer, settings, and CT ratios. 
• Low voltage circuit breakers data and trip unit type and settings 
• LV and MV fuses size and type 

Specific data for AC and DC system analysis

• type of system grounding (for protection and short circuit study) 
• BESS:  battery energy storage system type, designed power, batteries configuration, physical gaps between “+ and –” electrodes, DC protection type and settings 
• PV: inverter type, short circuit specification, configuration of modules connected, topology, DC protection type and settings 
• WIND: generator data sheet and type, converter data and protection type, system topology and min max wind generators connected 
• DC systems – verify electrode gap (min max), short circuit protective device, system voltage  (model range check), DC source type for short circuit study 
• UPS: configuration and working modes (external by-pass, electronic by-pass), power or battery package, UPS short circuit behaviour (current and voltage)  

Example of data collection summary

Site visit and data collection activities need to be performed according to site safety rules. It also requires a site authorised person to accompany the engineer during data collection and allow access to all necessary equipment, switchgears, and switch rooms. Data should be collected and documented as it serves later as a reference point for any assumptions and comments. Good practice is to transfer all the information’s later back to the customer for further use and upgrades. It can look like this example below.

Defining the Scope of Work

In the initial phase before arc flash analysis, it is important to identify scope of work.
Below, I highlighted the few most common things that will have the biggest impact: 

• Customer specific targets (system retrofit, specific safety issues, modernization, etc.).
• Which part of installation? (Complete system or part only.) 
• System voltage LV, MV, or HV.
• AC only or AC & DC.
• Type of facility (test lab, marine, data centre, industrial, etc.).
• Type of DC installation (BESS, UPS, UPSaaR, DRUPS, DC motors, DC generators, etc.).  
• Operation scenarios, possible system configurations.
• Related customers procedures (EHS, arc flash corporate rules).
• Any other relevant information.

Where to Find the Input Data? 

Our next step is to have a kick-off discussion between a Power System Engineer and a customer. This is so far the easiest way to explain important details and identify scope of work for arc flash analysis. To assess scope of work, we need information which can be found in: 

• Documentation (previous studies, load schedules, instructions).
• Single Line Diagrams with MV and LV network data.
• Any excel load lists, motors lists.
• EHS instructions or procedures.
• Site specific requirements and documents.

What are limitations for arc flash analysis? IEEE 1584, EPRI and OSHA 1910.269 models.

It is very good if installation falls into IEEE 1584 model range, which is:

• 208 V to 600 V: 500 A to 106 000 A (AC)
• 601 V to 15 000 V: 200 A to 65 000 A (AC)

Above 15kV we will follow EPRI or ArcPro (OSHA 1910.269) based guidance up to 800kV system range, however supply voltage above 15kV for industrial application happens only in specific situations. Practical rules for arc flash evaluation limits looking from protective device perspective is to start from (or stop at):

• LV circuit breaker  ≥63A 3P (MCB, MCCB)
• LV fuse ≥ 100A 
• LV Motors  ≥  50HP (37kW) 
• MV system up to 15kV (*>15kV EPRI / ArcPro OSHA 1910.269) 
• DC systems up to 1000VDC

What If Electrical System Documentation Is Missing?

We have two options: 

1. Wait for documentation update (longest).
2.  Arrange site visit for system estimation (fastest).

System estimation visit goal is to do a fast review of installation and collect information’s about:

• size of the electrical system
• condition of the installation
• type of the equipment
• amount of the equipment

Lack of documentation is an obstacle, but for experienced engineer after such visit it should be possible to provide reasonable estimation on cost and general follow-up plan. Missing documentation is less comfortable situation for installation owner, thus it is good to have flexible approach and provide support.

Single line diagrams mapping – A Smart Alternative

If no or little documentation exists, it is necessary to made it. Since arc flash analysis requires some specific data to be collected, it is a good idea to arrange data collection with system mapping. What is system mapping? It is simply creating single line diagram of the system (MV to LV feeders). This process and can take days or weeks depending on system size. It has an important additional value as it can be combined with data collection for arc flash analysis. Thus, it will save time and money providing valuable system overview and all details necessary for further analysis. 

What Is an Arc Flash Risk Assessment?

Arc flash risk assessment is the foundation of improving electrical safety in industrial and commercial installations. Arc flash incidents are among the most severe hazards in electrical installations, with potentially catastrophic consequences for people, equipment, and infrastructure. This series aims to deepen your understanding of arc flash phenomena, provide a systematic knowledge framework, and guide you through the essentials of a thorough risk assessment in this domain. Let’s begin!

The Essentials of Arc Flash Risk Assessmen

Performing a proper Arc Flash Risk Assessment requires precise calculations and adherence to established guidelines. Depending on the region, these include:

• IEEE 1584 – Guide for Performing Arc-Flash Hazard Calculations (global),
• NFPA 70E – Handbook for Electrical Safety in the Workplace,
• DGUV 203-077 – (Germany),
• Experimental methods and engineering best practices.

This article outlines a comprehensive process to help you understand what goes into a detailed and professional assessment.

How Does an Arc Flash Risk Assessment Project Work?

The following steps for a typical project give us an idea of what we should expect. Of course, the requirements can be expanded depending on the particular installation or specific customer requirements.

The standard IEEE 1584.1 outlines the necessary components of an arc flash risk assessment report and specifies mandatory documentation. A superficial analysis that merely provides a table of results, without actionable insights, is of little value. Below is a structured, 16-step process to ensure a reliable and actionable outcome.

The 16-Step Arc Flash Risk Assessment Process

1. Define the Scope of Work – Collaborate with the client to establish the scope, typically covering everything from the connection point to overcurrent protection rated at 63A in a 400V network.
2. Data Collection – Conduct on-site inspections and review electrical documentation, network schematics, and operating descriptions.
3. Model Creation – Develop a model of the electrical installation using advanced software (e.g., SKM, ETAP, CYME, Easypower).
4. Short-Circuit Current Analysis – Perform calculations based on standards (IEC 60909, ANSI, IEC 61660, etc.) for various operational scenarios.
5. Selectivity Analysis (Current State) – Prepare protection device characteristics and documentation.
6. Equipment Short-Circuit Rating Assessment – Verify the durability of switchgear and breakers against calculated short-circuit currents.
7. Arc Flash Analysis (Current State) – Calculate arc flash incident energy and determine PPE requirements for all switchgear under the current setup.
8. Results Review – Identify recommendations to improve selectivity, reduce arc flash energy, or highlight equipment that exceeds its short-circuit capacity.
9. Selectivity Analysis (Recommendations) – Propose adjustments to protection device settings and medium-voltage (MV) protections to enhance selectivity.
10. Arc Flash Analysis (Recommendations) – Recalculate based on proposed settings or technical solutions.
11. Reporting – Compile all results, recommendations, modeling data, single-line diagrams, and informational labels in formats like PDF or Excel.
12. Training – Provide introductory training on arc flash risks, either on-site or via teleconference.
13. System Labeling – Supply and install informational labels on analyzed switchgear.
14. PPE Selection – Assist in selecting appropriate Personal Protective Equipment (PPE).
15. Report Presentation – Discuss the report findings and technical solutions with the client.
16. Updates – Regularly update results every five years or after significant system upgrades.

Why a Thorough Arc Flash Analysis Matters

Superficial assessments may offer quick results, but often leave clients with insufficient insights and unresolved risks. A comprehensive analysis, supported by actionable recommendations and system improvements, ensures both safety and efficiency.

In the following articles, we’ll dive deeper into each phase of the process, offering practical solutions to enhance electrical safety and mitigate arc flash risks.