IEC 62793 pdf download.Protection against lightning – Thunderstorm warning systems
1 Scope
This International Standard describes the characteristics of thunderstorm warning systems and evaluation of the usefulness of lightning real time data and/or storm electrification data in order to implement lightning hazard preventive measures. This standard provides the basic requirements for sensors and networks collecting accurate data of the relevant parameters, giving real-time information of lightning tracks and range. It describes the application of the data collected by these sensors and networks in the form of warnings and historical data. This standard applies to the use of information from thunderstorm warning systems (systems or equipment providing real-time information) on atmospheric electric activity in order to monitor preventive measures. This standard includes: • a general description of available lightning and storm electrification hazard warning systems; • a classification of thunderstorm detection devices and properties; • guidelines for alarming methods; • a procedure to determine the usefulness of thunderstorm information; • some informative examples of possible preventive actions. The following aspects are outside the scope of this standard: a) lightning protection systems; such systems are covered by the IEC 62305 series; b) other thunderstorm related phenomena such as rain, hail, wind; c) satellite and radar thunderstorm detection techniques. A non-exhaustive list of situations to which this standard could be applicable is given below: • people in open areas involved in activities such as maintenance, labour, sports, competitions, agriculture and fisheries or situations where large crowds gather; • wind farms, large solar power systems, power lines; • occupational health and safety prevention; • sensitive equipment such as computer systems, emergency systems, alarms and safety equipment; • operational and industrial processes; • storage, processing and transportation of hazardous substances
3 Terms, definitions and abbreviations
3.1 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 .1 alarm information indicating that the target or the surrounding area is likely to be affected by thunderstorms and the accompanying lightning related events 3.1 .2 cloud-to-ground lightning CG electric discharge of atmospheric origin 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 3.1 .3 coverage area CA area where a given warning equipment has a sufficient detection efficiency and/or accuracy to give a warning 3.1 .4 detection efficiency DE percentage of cloud-to-ground discharges (flashes or strokes) that are detected and located by a sensor or a network Note 1 to entry: As cloud-to-ground flashes are often composed of several strokes, there is a difference between flash detection efficiency and stroke detection efficiency. A flash is reported (detected) if at least one stroke (first or subsequent) is detected and therefore flash detection efficiency is always equal or higher than stroke detection efficiency. 3.1 .5 dwell time DT time that an alarm is sustained after all warning criteria are no longer met 3.1 .6 effective alarm EA alarm where a lightning related event occurs in the surrounding area during the total alarm duration 3.1 .7 time to clear TTC time between the occurrence of the last lightning related event in the monitoring area and the time when the alarm is released 3.1 .8 failure to warn FTW occurrence of a lightning related event in the surrounding area for which no alarm occurred 3.1 .9 failure to warn ratio FTWR ratio of failure to warn with respect to the total number of situations with lightning related events affecting the surrounding area 3.1 .1 0 false alarm FA alarm not followed by lightning-related events within the surrounding area 3.1 .1 1 false alarm ratio false alarm rate FAR ratio of false alarms to the total number of alarms 3.1 .1 2 field strength meter FSM device for continuous monitoring of the atmospheric electrostatic field associated with thunderstorms EXAMPLE: Field mill. 3.1 .1 3 cloud lightning IC discharge occurring within or among thunderclouds or between thunderclouds and air and which does not have a ground termination 3.1 .1 4 lead time LT time between the start of an alarm and the effective occurrence of the first lightning related event in the target area 3.1 .1 5 lightning flash electric discharge of atmospheric origin consisting of one or more strokes Note 1 to entry: This discharge may occur within or between clouds, between the clouds and air and between a cloud and the ground. 3.1 .1 6 lightning related event LRE CG lightning flash to or near the structure to be protected, or to or near a line connected to the structure to be protected
IEC 62793 pdf download
