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WG C4.407 Lightning Parameters for Engineering Applications

 

Scope, deliverables and proposed time schedule:

Background: Traditional lightning parameters needed in engineering applications include lightning peak current, maximum current derivative (di/dt), average current rate of rise, current risetime, current duration, charge transfer, and action integral, all derivable from direct current measurements. Distributions of these parameters presently adopted by CIGRE are based on measurements by K. Berger and co-workers in Switzerland. There also exist more recent direct current measurements obtained using instrumented towers in Austria, Germany, Russia, Canada, and Brazil, as well as those obtained using rocket-triggered lightning. Further, modern lightning locating systems report peak currents estimated from measured magnetic field peaks. There is urgent need to evaluate these new experimental data to determine the limits of their applicability to various engineering calculations. Evaluation should include both instrumental and methodological aspects. Possible geographical, seasonal and other variations in lightning parameters, as well as the need to extend the list of traditional parameters to include, for example, characteristics of continuing currents and M-components should be examined. Additional lightning parameters to be analysed in view of availability of new data include number of strokes per flash, interstroke interval, number of channels per flash, relative intensity of strokes within a flash, return-stroke speed, and equivalent impedance of the lightning channel. More detailed information about less frequent, but potentially more destructive positive and bipolar lightning flashes is needed.

Scope:

The scope of the working group includes the following:

  • Evaluation of current measurements on instrumented towers
  • Evaluation of current measurements for rocket-triggered lightning
  • Evaluation of the procedures used to estimate lightning currents from measured fields, with emphasis on those implemented in lightning locating systems
  • Inclusion of additional lightning parameters (e.g., characteristics of continuing currents, return-stroke propagation speed, equivalent lightning channel impedance, etc.) that are presently not on the CIGRE list, but needed in engineering applications
  • Further characterization of positive and bipolar lightning discharges
  • Characterization of upward lightning discharges
  • Search for any geographical, seasonal and other variations in lightning parameters
  • Preparation of a reference document “Lightning Parameters for Engineering Applications” based on the current understanding of lightning processes and taking into account limitations of various measuring techniques
Convener: V. Rakov (USA)

Publication: TB549: LIGHTNING PARAMETERS FOR ENGINEERING APPLICATIONS (Published: 2013-08)