IEC 62858:2019

IEC 62858 ®
Edition 2.0 2019-10
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Lightning density based on lightning location systems – General principles

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IEC 62858 ®
Edition 2.0 2019-10
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Lightning density based on lightning location systems – General principles

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.020; 91.120.40 ISBN 978-2-8322-7497-2

– 2 – IEC 62858:2019 RLV © IEC 2019
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms, definitions, abbreviated terms and symbols . 6
3.1 Terms and definitions . 6
3.2 Abbreviated terms and symbol . 8
4 General requirements . 8
4.1 General . 8
4.2 Stroke-to-flash grouping . 9
4.3 Minimum observation periods . 9
4.4 Observation area . 9
4.5 Grid cell size . 10
4.6 Edge effect correction . 10
5 Validation of lightning location system performance characteristics . 10
Annex A (informative) Determination of lightning density for risk calculation . 12
Annex B (informative) Ground strike points (GSPs) explanations and calculation
methods . 13
Bibliography . 14

Figure A.1 – High resolution full climatology (HRFC) N data. 12
t
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LIGHTNING DENSITY BASED ON LIGHTNING LOCATION SYSTEMS –
GENERAL PRINCIPLES
FOREWORD
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– 4 – IEC 62858:2019 RLV © IEC 2019
International Standard IEC 62858 has been prepared by IEC technical committee 81:
Lightning protection.
This second edition cancels and replaces the first edition published in 2015. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
Two informative annexes are introduced dealing with the determination of lightning density for
risk calculation (Annex A) and ground strike point calculation methods (Annex B).
The text of this International Standard is based on the following documents:
FDIS Report on voting
81/627A/FDIS 81/634/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
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INTRODUCTION
International standards for lightning protection (e.g. IEC 62305-2) provide methods for the
evaluation of the lightning risk on buildings and structures.
The lightning ground flash density N , defined as the mean number of lightning flashes to
G
ground per square kilometre per year, and the ground strike point density N , defined as the
SG
mean number of ground strike points per square kilometre per year is are the primary input
parameters to perform such an evaluation (see Annex A).
In many areas of the world N is derived from data for risk evaluation are provided by
G
lightning location systems (LLSs), but no common rule exists defining requirements either for
their performance or for the elaboration of the measured data.

– 6 – IEC 62858:2019 RLV © IEC 2019
LIGHTNING DENSITY BASED ON LIGHTNING LOCATION SYSTEMS –
GENERAL PRINCIPLES
1 Scope
This document introduces and discusses all necessary measures to make reliable and
homogeneous the values of ground flash density, N and ground strike point density, N ,
G SG
obtained from lightning location systems (LLSs) in various countries. Only parameters that are
relevant to risk assessment are considered.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 62305-1, Protection against lightning – Part 1: General principles
IEC 62305-2, Protection against lightning – Part 2: Risk management
3 Terms, definitions, abbreviated terms and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62305-1 and
IEC 62305-2 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1.1
cloud-to-ground lightning
CG
discharge that is comprised of one or more cloud-to-ground lightning strokes that propagate
from cloud to ground or vice versa and lead to a net transfer of charge between cloud and
ground
Note 1 to entry: This note applies to the French language only.
3.1.2
cloud lightning
IC
discharge occurring within or among thunderclouds (intracloud), or between thunderclouds
(intercloud), or between cloud and air, without a ground termination
Note 1 to entry: This note applies to the French language only.
3.1.3
first return stroke
first stroke to ground of a cloud-to-ground lightning discharge

Note 1 to entry: The stepped leader and attachment process precede the first return stroke.
3.1.4
subsequent stroke
subsequent stroke to ground that follows a previous (return) stroke in the same flash
Note 1 to entry: A subsequent stroke is preceded by a dart leader and may or may not have the same ground
strike-point as any previous (return) stroke in the same flash.
3.1.5
multiplicity
number of first and subsequent strokes in a cloud-to-ground lightning flash
3.1.1
ground flash density
N
G
-2 -1
mean number of cloud-to-ground flashes per unit area per unit time (flashes x km x year )
3.1.2
ground strike-point density
N
SG
mean of the number of strike-points to ground or to ground based objects per unit area per
-2 -1
unit time (strike-points x km x year )
3.1.3
lightning sensor
device t
...