“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.”