IEC Lighning Design
IEC Lighning Design
(OP)
I need to perform lightning design based on IEC 62305. The part-2 of this standard is risk assessment which is very complicated calculations. I don’t want detailed calculations. Is there a short way to perform approximate risk assessment calculations? If I know the number of lightning flashes per year, and the dimensions and height of the structure; then can I perform some approximate quick calculations for lightning risk assessment?






RE: IEC Lighning Design
RE: IEC Lighning Design
Also I changed the parameters many times in this software, but I always got the same result that lightning system is required. Even if I set the flash density as minimum, structure as non-metal & non-flammable, and building as unoccupied; still I get the same result that lightning protection should be installed. Do you have some idea under what conditions the lightning protection is “not” required?
RE: IEC Lighning Design
Using that specific calculator, I venture a guess that there will be no situation where it will indicate that the offered product is not needed. That is similar to walking into an auto dealership and asking them if you need a car.
RE: IEC Lighning Design
RE: IEC Lighning Design
RE: IEC Lighning Design
Alternatively, Furse have a time-limited trial version of their StrikeRisk software available as a free download which might be adequate for your needs.
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RE: IEC Lighning Design
The problem is that some part of the plant is hazardous. So I have to set the fire-risk as “explosion”. This increases the calculated-risk dramatically and lightning-protection of level-2, level-3, and even level-4 is not enough. So I have to use the most stringent lightning-protection (which is metal-roof with natural-down-conductors.)
The fact is that only a small part of the building (about 10%) is hazardous. Do I still need to take the whole building as hazardous?
RE: IEC Lighning Design
If you are reasonably certain that you need a LPS anyway, then ScottyUK’s link is probably a good place to start, as this should indicate what Lightning Protection Level you require according to IEC 62305.
As there are several different levels of lightning protection allowed for in IEC 62305, if you have a definite requirement to ensure that your installation is compliant with this standard then you will most probably end up having to carry out a risk assessment using IEC 62305 part 2 anyway. This will prove that the Lightning Protection Level you have selected is adequate - no protection, LPL IV, LPL III, LPL II or LPL I, going from the lowest to the highest level of protection. I’m not sure if there’s any simple way out of this other than to do the risk assessment as per the standard, unless other posters have spotted some loophole?
When carrying out a risk assessment using IEC 62305 part 2, you do have the option of assuming as a starting point that you have no dedicated lightning protection installed. If your risk assessment shows that the various risk levels are below the limits, then this can be used to justify that no special measures are required. However, you would need to be quite sure that you are not being over-optimistic with your input data!
If the level of risk is above the applicable limits, then you need to repeat the risk assessment using the next (higher) level of lightning protection until the residual risk is below the limits (i.e. go from no protection to LPL IV, then LPL III, etc. until you get something that works). You then move onto the second stage of the process and carry out your rolling sphere analysis to make sure that your lightning protection structures provide the necessary coverage (e.g. using a sphere radius of 60m for LPL IV, 45m for LPL III etc.).
I agree that the risk assessment methodology in the standard is fairly messy. Whether you use a risk assessment tool like the one ScottyUK linked to or whether you build an Excel spreadsheet to do this yourself, you still need decent input data for the risk assessment, or have some acceptably conservative values to use in cases where you don’t have good data… not easy!
IP
RE: IEC Lighning Design
The Furse risk-assessment software link by ScottyUK is very useful. If I set the fire-risk as “low” or “ordinary”, then there are no problems because the least stringent lightning-protection (Level 4) is enough.
The problem is that some part of the plant is hazardous. So I have to set the fire-risk as “explosion”. This increases the calculated-risk dramatically and lightning-protection of level-2, level-3, and even level-4 is not enough. So I have to use the most stringent lightning-protection (which is metal-roof with natural-down-conductors.)
Actually only a small part of the building (about 10%) is hazardous. Do I still need to take the whole building as hazardous?
RE: IEC Lighning Design
RE: IEC Lighning Design
The main question is the roof. Because the lightning protection level on the roof depends on the nature of the area inside the roof (hazardous or non- hazardous).
It is easy to break down the internal area into zones, but how to break down the roof into zones?
RE: IEC Lighning Design
What do you really want?
RE: IEC Lighning Design
A small part of the building is hazardous which means that the most stringent lightning protection level (level 1) will be required for this part. The remaining part of the building is non-hazardous (which means that the least stringent lightning protection level (level 4) will be required for this part. This is easy.
The main question at this time is about roof. The lightning protection level on the roof depends on the nature of the area inside the roof (hazardous or non- hazardous). Should we have to provide the most stringent lightning protection level (level 1) for the whole roof?
RE: IEC Lighning Design