Lightning Protection Zones (or LPZs) are central to the IEC 62305 approach to lightning protection. The idea is to limit lightning-induced current and voltage surges entering a structure by dividing the structure into a succession of risk zones (nested inside each other.) Through a careful use of shielding techniques and SPDs the effects of lightning hitting the outer zone are meant to be mitigated before they can reach the inner zones. At least that is the theory. According to IEC 62305-4 (Sect. 4.1) this LPZ concept is the basis of all lightning protection.
The IEC-branded LPZ concept has been in widespread continuous use for 20 years. Yet when Rakov and Uman searched, they were unable to find a single study containing statistical evidence confirming its effectiveness ("Lightning, Physics and Effects, Cambridge University Press" page 591). A further search in 2013 also turned up null. Apparently no study has ever vouchsafed the workability of the IEC 62305's LPZ system.
On the face of it, the LPZ system seems a logical approach to surge protection. So why, in 20 years, have there not been studies documenting its success? That question led to a deeper look into its evolution and application.
The original LPZ concept was created by an American, E.F. Vance, of the Stanford Research Institute in Menlo Park, California. Vance introduced it in 1977 in a paper entitled "Shielding and Grounding Topology for Interference Control." On the left is a diagram extracted from that paper showing Vance's risk zones. By "grounding" the outside of each shield to the inside of the adjacent shield, Vance sought to control the effect of external surges entering a facility. He also realized the need to limit the surges on the power and data lines entering the structure.
Zone 0 was the moniker Vance gave to the external environment subject to lightning strikes. Zones 1 & 2 he assigned to the areas inside the structure.
Dr. Hasse appropriated Vance's idea and transformed it into a book he titled: "EMC-Lightning Protection Zone Concept" (co-authored by Peter Hasse & Johannes Wiesinger and published by Pflaum Verlag in 1993.)
On the right you can see Vance's LPZ diagram as it appears, unchanged (except for the addition of the German translation) on p. 52 of Hasse's book. Vance's original structure and terminology were retained in the Hasse adaptation: Zone Zero continued to represent the area outside the structure; Zones 1 & 2, the areas inside the structure.
Unfortunately Dr. Hasse used the LPZ system to forward his 10/350 waveform idea by insinuating the idea that all lightning impulses in Zone Zero should be characterized by a 10/350 waveform. Click here to see how Hasse's 1993 LPZ book injected the 10/350 waveform into the LPZ concept.
In so doing, he nullified the potential success of what might have become a very workable approach to lightning protection. The complications caused to the LPZ system by the 10/350 waveform include the defects of the spark gaps, plus the quagmire of "SPD coordination" both of which are dealt with elsewhere on this web.
By the time his LPZ book was published in 1993, Dr. Hasse was a formidable presence in the IEC lightning protection committee, TC 81. It took him less than two years from the publication of that book to get his LPZ concept imported in its entirety into the IEC 61312-1 standard.
On the left is the LPZ diagram from IEC 61312-1. The 10/350 waveform was made an integral part of it. Click here to see the Hasse 10/350 lightning parameters as they appeared in the 61312-1 standard.
Thus can be seen, that in a single flash of lightning, Dr. Hasse succeeded in getting both his 10/350 waveform AND his LPZ concept imported into the IEC international lightning protection standard.
The most recent LPZ diagram from IEC 62305 is shown on the right. Its purpose is ostensibly to mitigate the impact of incoming lightning. But some believe the function of the IEC LPZ system has more to do with stipulating which structural and surge protective devices are to be deemed "proper" and thus regulating their use. For example, IEC 62305 insists that direct lightning must be characterized by a 10/350 test waveform and therefore only spark gap "lightning arrestors" may be used in Zone Zero. Other types of SPDs are banned.
There are three major problems with this approach. The first two are technical and are documented throughout this web, namely: 1) the 10/350 waveform does not represent actual lightning, and 2) the spark gap "lightning arrestors" have many intrinsic flaws.
The third major problem could be a legal one. The way the LPZ system has been implemented in standards may constitute a violation of European Union Competition Law. (See FAQ page.)
In case anyone is taking this "personally" please accept the fact that this website is not meant to be a rant on any particular person, company or committee. Its entire object is to improve the state of lightning protection. And though it may take courage to stand up and speak, it takes just as much courage to sit down and listen.