Fatal Case Study of Electrocution

That's not what the're designed for....

The severity of shock depends on voltage,duration,leakage/fault current,body resistance, PPE,Earth Fault Loop Impedance etc

Electricity doesn't necessarily kill; it's the ground that we need to watch.

I'm sorry for your loss.

I'm not an engineer, but my guess would be, that he conducted electricity,and the RCCB didn't know to trip. Humans are just bags of salt water.

If the designer followed a 40 amp RCCB with a 60 amp MCB, one wonders if he got the rest of the design right.

Did the wires that killed the careless welder go through the RCCB??

The answer is in the question itself. He had touched both the live wires without any linkage to earth. Probably he was wearing shoes. The burn marks on the body may provide clue about how the shock had gone through his body. If it happened as suspected above, RCCB will not trip. The breaker ratings are very poorly selected, to say the very least and the poor guy may have paid for with his life for somebody else mistake.

RCCB trips on current differences between energized and return conductors, i.e. it detects leakage to earth, not supposed to be there, possibly by a human body touching a leaky equipment. This wasn't the case for the poor guy, he obviously made conduct between phases. Too much confidence can get you very much dead. Seen it happening many times, and many more times not happening just by luck, including of course incidents I got myself in. RIP. S.M.

I am sorry for your loss.

A GFI "should" protect a person from unbalanced shocks, but it looks like he completed a circuit from the output to ground. The Ground Fault Interruptor did not detect an unbalanced load, but rather a simple load, which it is designed to allow through.

Of course, that is a guess which assumes all equipment is working properly otherwise.

The equipment should be packed up without anybody touching, or changing anything, and be subjected to a forensic exam. It will be crime scene evidence until your coroner releases it. That might be your job, I recommend that you get independent assistance from a licenced electrical engineer to examine the equipment to find out if the GFI was faulty or mis-installed.

If your task is to be the engineer in charge of the plant, then your task is to determine if there is some underlying intrinsically dangerous situation which has been found by this tragedy, and to rectify it so that it never happens again. Start here, and get on site expertise in on it. Hide nothing. Cover up nothing. Now is the time, for the sake of the family, to find out the truth, and determine how to make things safe for other workers.

Again, my condolences on the loss of an employee who was just doing his job. Such tragedies MUST be used to make things better for all.

If current flows from phase to ground GFCI should trip,but not trip if current flows from phase to neutral. In work places the employer should ensure workers wear PPE like shoes,gloves etc

The tragedy here is that the worker would most probably have been wearing his shoes. If he was bare foot he would have had at least half a chance of surviving the shock because ELCB would / could have tripped. He would not have been wearing any insulating gloves though. Just bad luck and karma.

Although the other issues raised are mostly still valid, it's really all much simpler than that.

An RCCB with 30ma sensitivity is NOT meant for personnel protection, it is only for equipment protection against damage from arcing ground faults. He would have been in cardiac arrest before the 30ma threshold was attained even if the fault caused a current flow imbalance with respect to ground reference (which as mentioned, may even have never happened given the nature of the fault). Here in the US, personnel protection cannot excede 6ma, I believe it is similar for IEC regulations. But 6ma is unrealistic for something like a welder. That's why you have safety protocols on tasks involving the use of electricity.

Sorry for your tragedy, learn from the mistake.

5ma RCDs are used in children's wards in hospitals

The tripping current of RCD(mA) and the value of earth fault loop impedance(ohms),when multiplied(mAxohms/1000)should not exceed 50V,the safe touch voltage for adults. That's why BS recommends RCD of 30mA in consumer units(for a group of circuits) in homes and offices for many lights and sockets. In US 6mA is used for a single GFCI.

Just an annoying side issue from a grammar Nazi.

"Fatal case of electrocution" is redundant. Electrocution alone means it was fatal, electrocution means death by electric shock. If he had not died, it would be just an electrical shock. So saying "fatal electrocution" is the same as saying "death by electric shock death".

Sorry about the incident, but he should have known better than to work on circuits that are still activated. I've known electricians who will work on live circuits and it's just a matter of luck that they didn't get electrocuted. I'm sure some did. My son does this and it drives me crazy. Sometimes there is a need to work on live circuits, like on hi tension lines, but they are equipped with the proper safety gear to do so. No one else should ever work on live circuits.

Never rely on a RCD, 2% of them fail.It is only there to reduce the chances of a fatal electric shock.