Why myths or half-truths are bad?

When I started with arc flash, it took some time even for an electrical engineer to sort out what is important when it comes to an arc flash analysis.  It was harder since you can find quite some arc flash myths going around, which are not helpful. In the worst case, it can cause someone death or severe health issues. To give you perspective, it can be like driving a car with seat belts made of paper without knowing it. Misconceptions created around electrical safety makes it harder to transfer knowledge as people believe it is not needed. Living in safety bubble is comfortable as you do not need to do nothing extra, any safety plans, any risk assessments just find proper excuse or justification to existing situation. This unfortunately is a debt you take on someone else personal safety.   

How to find out that you are living in a safety bubble? 

If you find below myths suitable or true, do me a favour and make step outside of it and check it again. My colleagues from US taught me a very useful lesson: If you do not know if the decision is good or bad, imagine yourself explaining your decision in court after accident. 

Understanding Arc Flash Myths 

Let s start with the most common spells I hear people saying. Below what I found till now and a bit more:

1. Arc Flash Risk Assessment is not needed – ❌ NOT TRUE
   It is hard to call it obligatory in all EU countries, but it is necessary. In EU, we have EN 50110 (harmonised in each country under local norms)  which identify arc flash as a hazard and requires risk measure. If personal safety is not enough for someone, keep in mind that like in UK there are huge fines and prison sentence already happening.  
2. We got PPE APC1 and APC2 we are covered – ❌ NOT TRUE
   Very common in Europe but If PPE selection was done just out of blue it is not safe as it should be. Usually, it looks like this PPE Class 1 for LV installation and PPE Class 2 for MV and everything we’re afraid of. Does not matter what you use if it is not based on proper numbers it just creates a safety bubble, and it will be too late when flash accident will verify it. 
3. Arc Flash is only for big switchgears – ❌ NOT TRUE
   IEEE 1584 indicates that we can expect sustainable AC arc flash down to 240V AC with 2000A available short circuit current. Quite low and in practice it usually means that analysis is going down to 230V 63A MCB (Miniature Circuit Breaker) or 100A fuse.  
4. We don’t work live; we don’t need arc rated PPE – 🔶 HALF TRUE
   It is great if company can completely reduce live working to zero.  What about measurements, live maintenance, proving dead checks? After we de-energize the system, we need to prove no voltage. This point requires PPE and if you think different check THE MARK STANDIFER STORY (it is on YouTube). Till now, all companies I saw do some tasks on live equipment. 
5. Arc Blast is deadly –  🔶 HALF TRUE
   There was misconception in the past that above 40 cal/cm² arc related pressure blast is so big it can kill people. It was related with fact that previously every location above 40 cal/cm² was called dangerous and no live work was allowed due to lack of PPE rating. Till now there is no fatal accident recorded due to arc blast. Arc blast exists but with proper PPE it can be handled if needed (yes you can estimate it if needed). Also, for Power System Engineer, it should be possible to lower energy below 40 cal/cm² in most projects. 
6. Low cal/cm² can be ignored – ❌ NOT TRUE
   It cannot be ignored and should be addressed properly. Sometimes people tend to ignore low level arc flash locations with below 4 cal/cm² assuming it is not that bad as 40 cal/cm². Energy of 4 cal/cm² may sound small, but it will cause 3^rd degree burns the same way as 40 cal/cm². Difference can be surface of burns or your chance to survive it.  
7. 400V AC is safer than 11kV – ❌ USUALLY NOT TRUE
   I believe this comes from electrocution point of view. Medium voltage sounds more dangerous than low voltage, but when it comes to arc flash, it is counterintuitive. It all depends on electrical system design, protection setting and few more things.  Most of the time, low voltage switchgears are identified with much higher arc flash incident energy than medium voltage switchgear supplying it. This is an effect of much higher short circuit currents at LV level in general, arcing current/bolted current ratio that can reach even 38% of bolted fault short circuit current and extended tripping times which are caused by it. 
8. New switchgear is safe – 🟡SHOULD BE TRUE
   It all depends on what you buy. Assuming your switchgear is not arc resistant or IAC, technically there is no big difference from arc flash point of view. Imagine that you had old panel identified with 35 cal/cm2. Now it was 1:1 replaced, and protective settings were replicated (very common). What is the difference now? It is still 35 cal/cm2. What can or should change are better covers to lower risk of initiating arc flash or electrocution, motor operated breakers, better form of separation and improved protection units. Such solutions are usually driven by arc flash risk assessment combined with selectivity, short circuit, and equipment analysis, otherwise it is hard to see direct improvement.  Just having new switchgear is not enough to say it is safe, and we do not worry about arc flash any more. Keep in mind that live maintenance, measurements, or voltage check is done with doors/ covers open.