Reasonable laziness is not a vice in practical lightning protection. E. M. Bazelyan

Laziness is naturally considered to be perhaps the most common human vice. Countless sayings and fairy tales scourge laziness.

"Laziness, open the door! We're on fire! I'd better burn than open!"

But what if we talk about reasonable laziness? Is it really that harmful in an engineer's practice? This question is quite legitimate and justified. Generally, we are talking about avoiding useless work that is costly, scientific but unable to improve the engineering solution. Here is an obvious example.

Why calculating the electrode grounding resistance with an accuracy up to the third or even the fourth decimal place, if the soil resistivity can only be measured with an error of about 10%? The computer time spent on such calculations is really pointless. It cannot improve the design quality. Reasonable laziness is beneficial here. It allows avoiding meaningless work in the design, which is rather time and resource consuming, if the initial design data are not very reliable.

The ZANDZ company has come up with an idea for this article after it a letter from a reader of the article on extended under and aboveground utilities posted on the website. It demonstrated the expediency of completely avoiding work on such utilities in a stormy environment. For this, a possibility of a real danger of heart fibrillation was demonstrated, even when the weakest lightning strikes a utility with extremely low current. The article did not claim to be anything more. In particular, it didn't need and therefore didn't raise an issue of the effect of the voltage pulse shape delivered along the utility on the human death probability due to fibrillation. The article was not aimed at solving such a task. It was only enough to know that the voltage was very low. So, a no is a no.

This is how they are mentioned in the regulatory document assessing the danger of fibrillation.

Длительность импульса, мс - Pulse duration, msec
Ток через тело человека - Current flowing through the human body
мА - mA

You can see that there are no specific calculated points on the diagram, and the scale along the axes is logarithmic, suggesting a rather low data reliability. The time range considered does not fall below 100 μs. This is not enough for estimates of at the microsecond duration typical of thunderstorm surges. In such conditions, it makes no sense to operate with time parameters other than the total pulse duration. The initial data do not allow for something more. The real shape of the affecting pulse in the regulatory document is not even mentioned, and there is nowhere to find it out. If an engineer is too active and reasonable laziness is not characteristic of them, they can come up with something new, e.g. to estimate the total duration of the affecting pulse as a result of dividing the transferred charge by the current amplitude, which seems beautiful and quite scientifical! Or you can use another estimation method, e.g. the one based on the duration of the pulse change from zero through the maximum and up to the half the amplitude. It's no worse either. Numerous other options are also possible. It's only about the calculator's imagination. Naturally, each option will lead to a different dangerous voltage value. This cannot be avoided. The uncertainty of the initial data, as shown in the figure, interferes with the specific conditionality of the calculation. You can't get more out of them. And in such conditions, laziness is unlikely to become any kind of serious disadvantage. It does not matter which pulse length parameters is used for calculation, since the dangerous effect level magnitude will be estimated reliably. And the provided initial data simply do not pretend to be more than that. They are not intended for anything else. You need to remember this well and do not clarify the information that cannot be clarified. In fact, the initial data shown in the figure are suitable for a qualitative solution only.

If you still need to clarify, don't be lazy to ask a different question: what is it planned for? This is most often needed to assess the frequency of dangerous exposure. And here again, it is useful to become reasonably lazy. Estimating the frequency of dangerous exposure requires reliable knowledge of the magnitude of the dangerous current. It is not always easy to calculate it. Take your time, don't start it. First make the most rough assessment just out of laziness. If the value of the dangerous current lies within hundreds of kiloamps, it's worth it. In this case, even a twofold change in current changes the probability of its occurrence within an order of magnitude. However, with low lightning currents, i.e. of tenths of an average value, the probability of a dangerous event will change by about several dozen percent. There is no point in such a clarification, especially the one that is not too reliable. Let your reasonable laziness help you avoid the inefficient although consuming calculations, and take you away from the computer for a walk in the fresh air.
This way, reasonable laziness can help you save your health.

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