Thunderstorm Warning Systems: IEC 62793 standard

Draft standard IEC 62793 deals with Thunderstorm Warning Systems (TWS). This standard introduces many definitions and deals with many technologies. The study concentrates on Lightning Location Systems (LLS) and local field mill detectors. Regarding LLS, the European lightning detection network is used as an example for determining its efficiency with respect to warnings of cloud-to-ground lightning in Western Europe using the definitions given by the standard. In terms of field experience, LLS have maintenance rules that are under responsibility of the LLS operator. But in case of local sensors such as field mill detectors it is crucial that maintenance is made by the user or a specialized company. Field experience in harsh environment shows that local sensor of the field mill type may give false warnings or at the opposite no warning if not properly maintained. The new draft standard IEC 62793 Ed. 1 addresses specifically tests on local sensors introduced to increase their withstanding against environment.

I. Introduction

There are basically two types of Thunderstorm Warning Systems (TWS): Lightning Location Systems (LLS) and local detectors mainly of the field mill (FM) type. New draft standard IEC 62793 Ed. 1: Protection against lightning - Thunderstorm warning systems [1], covers both. At the same time, efficiency of TWS is included in draft standard IEC 62305–2 for risk assessment. It is then necessary to take care of field experience to be sure that IEC 62793 standard will cover the need of the users. Basically a user needs an early and reliable warning. The failure to warn ratio is then an important parameter especially for risk management. A failure to warn may mean a big loss or even a personal injury. This paper will first concentrate on the performance analysis of the European lightning detection network with respect to warnings of cloud-to-ground lightning in Western Europe. In the second part of the paper we will discuss field experience, maintenance and the tests included in the draft standard for local sensors.