High Voltage Strike Attachment Test

Disregarding the cloud electrification mechanisms, a lightning discharge starts with the attachment processes. For a downward initiated strike, the attachment process begins with the descending downward leader. When this leader reaches within vicinity of the grounded structures, upward leaders are formed from exposed surfaces, and the quest is then to determine the origin of the upward leader that reaches the downward leader first. The junction between the downward stepped leader and the upward successful connecting leader then defines that the lightning current will flow into the origin of the leader.

The strike attachment test exposes the structure in concern (antennas, wind turbine blade and other installations and structures exposed to direct strikes) to the electric field preceding the attachment. This will develop connecting leaders from the structure, and by photographing the process in different configurations, it can be investigated whether only the intended attachment points – the installed air termination system – are exposed. If the structure is struck outside the installed air termination system, the test method and associated analysis will suggest where further air termination systems are to be installed.

The strike attachment test is performed according to IEC 61400-24 and is documented with a test report containing pictures and test results.