2002

Miki M., Shindo T., Rakov V.A., Uman M.A., Rambo K.J., Schnetzer G.H., Diendorfer G., Mair M., Heidler F., Zischank W., Thottappillil R., Wang D.: Characterization of the initial stage of upward-initiated lightning

26^th International Conference on Lightning Protection (ICLP), Cracow, Poland, 2002 We compare the characteristics of the initial stage (IS) in natural upward lightning as observed on (1) the Gaisberg tower (100 m, Austria), (2) the Peissenberg tower (160 m, Germany), and (3) the Fukui chimney (200 m, Japan) with their counterparts in rocket-triggered lightning in Florida. All current records in Japan and some of the current records in Germany and Austria were obtained in winter, whereas all triggered-lightning data were obtained in summer. All lightning events analyzed here effectively transported negative charge to ground. The geometric mean (GM) values of the overall characteristics of the IS, duration (T), charge transfer (Q), and average current (I), for rocket-triggered lightning (T = 305 ms, Q = 30.4 C, I = 99.6 A) are similar to their counterparts for Gaisberg-tower flashes (T = 235 ms, Q = 29.6 C, I = 126 A) and Peissenberg-tower flashes (T = 290 ms, Q = 38.5 C, I = 133 A), while the Fukui-chimney flashes are characterized by a somewhat shorter GM initial-stage duration (T = 77.1 ms) and a larger average current (I = 505 A). The GM initial stage charge transfer for the Fukui-chimney flashes is 38.9 C. The observed differences in the IS duration is probably related to the difference in the lower current measurement limits: about 200 A for the Fukui data set vs. 15 to 20 A for the other three data sets. The characteristics of the initial continuous current (ICC) pulses in object-initiated (Gaisberg, Peissenberg, and Fukui) lightning are similar within a factor of two to three, but differ more significantly from their counterparts in rocket-triggered lightning. Specifically, the ICC pulses in object-initiated lightning exhibit larger peaks, shorter rise times, and shorter half-peak widths than do the ICC pulses in rocket-triggered lightning. PDF File (522 KB)

Diendorfer G., Mair M., Schulz W.: Detailed brightness versus lightning current amplitude correlation of flashes to the Gaisberg tower

26^th International Conference on Lightning Protection (ICLP), Cracow, Poland, 2002 In 1999 a digital high speed video camera was installed at the lightning experimental site at the Gaisberg tower. The camera is capable of capturing black and white images in speeds of up to 1.000 frames/s. The camera is triggered by a trigger signal derived from the lightning current measured at the tower top. In summer 2000 five flashes were recorded by the digital camera and for those five flashes time correlated current measurements (sampling rate 20 MS/s) are available. In summer 2000 the frame rate of the camera was set to 500 frames per second with a total re-cording time of 2.1 s and a pretrigger of 50 %. There-fore these data provide sufficient time resolution for investigations on the optical development of the entire flash with a total time duration of up to several hundred milliseconds. On the other hand the 2 ms expo-sure time per frame is insufficient to analyze bright-ness details of individual strokes with a pulse duration of some tens to some hundreds of microseconds only. From the gray values of the frame pixels of a single frame we calculate a summed brightness value at a given channel cross section. By doing this for all light exposed frames of a flash we can derive a plot of brightness as a function of time. Comparison of the plots of brightness versus the plots of the channel current for four flashes is shown in the paper. For all four flashes we found a very similar wave shape for brightness and current. PDF File (324 KB)

Schulz W., Diendorfer G.: Amplitude site error of magnetic direction finder

26^th International Conference on Lightning Protection (ICLP), Cracow, Poland, 2002 Lightning peak current is one of the most important lightning parameters. Lightning Location Systems infer the peak current from the peak magnetic field. The lightning peak current is calculated from the averaged range normalized signal strengths of the detecting sensors multiplied by a calibration factor [Diendorfer et al, 1998]. The accuracy of the peak current estimate mainly depends on (1) the applied calibration factor and (2) the signal attenuation as a result of finite ground conductivity along the travel path of the signal. Additionally to these two well known effects on the amplitude measurement we will show in this paper that the so called "site error" of a direction finder does not only have an influence on the angle measurement of a lightning location system but also on the amplitude measurement. This so called "amplitude site error" is a function of the angle of field incidence similar to the angle site error. PDF File (452 KB)

Diendorfer G., Hadrian W., Hofbauer F., Mair M., Schulz W.: Evaluation of lightning location data employing measurements of direct strikes to a radio tower

CIGRE Session 2002, Paris, France, 2002 A Lightning Location Systems (LLS) provides large scale information for lightning strikes to ground. In addition to the event time and strike point position, the LLS gives estimates for the lighting peak current. For the end user of LLS data it is important to know the technical limits of the applied network in terms of detection efficiency, accuracy of the stroke location and peak current estimate. To establish a ground truth reference for comparison of natural lightning current parameters and the data of ALDIS (Austrian Lightning Detection & Information System), a telecommunication tower on Gaisberg near the city of Salzburg (Austria) was instrumented for direct lightning current measurement. Since the start of the tower experiment in 1998 we have recorded more than 200 lightning flashes to the tower. Based on the analysis of the current waveforms nearly all of them are so called upward initiated discharges. GPS time synchronization of both data sets allows a precise correlation of individual events measured at the tower and reported by the lightning location network. PDF File (459 KB)

Bernardi M., Pigini A., Diendorfer G., Schulz W.: Long term experience on lightning acquisition in Italy and Austria and data application to the improvement of lightning performance

CIGRE Session 2002, Paris, France, 2002 Lightning location systems (LLS) are in operation in Italy and Austria since about 10 years. The two networks are running in collaboration, sharing sensors data, since the beginning. The importance of this collaboration is shown, analyzing the behavior of the two networks as standing alone or as cooperating. In particular a detailed analysis is run on a set of data, evaluating the importance of the other network sensors in the calculation of lightning and in the efficiency and accuracy of the final results. The application of LLS data to improve the lightning performance evaluation of transmission and distribution lines is analyzed. Lightning density at ground is a key factor for performance evaluation of transmission lines. More accurate and detailed maps than those standardized may be derived by LLS, indicating that standardized values (average values for an area) are not sufficiently accurate to describe the situation of a given territory. The use of LLS data to correlate faults and lightning is discussed. In particular, for MV lines, one of the problems discussed is the necessary accuracy in lightning location. PDF File (318 KB)

Diendorfer G., Schulz W., Mair M.: Response of different types of lightning detection sensors to tower strikes in Austria

17^th International Lightning Detection Conference (ILDC), Tucson, Arizona, 2002 Lightning strikes to the instrumented Gaisberg tower are often detected by different types of sensors (IMPACT, IMPACT ESP, LPATS III, LPATS IV) installed in Central Europe as part of the EUCLID network. In this paper we present results of an analysis of the response of the different sensor types to lightning discharges to the radio tower. During the two years 2000 and 2001 we have successfully located 310 strokes to the tower with amplitudes in the range from 2 kA to 35 kA. For some of the strokes with higher peak currents reports from more than 30 sensors are available. The field propagation path from the tower site to the different sensors is mainly over flat terrain to the north and over mountains to the south. This arrangement allows evaluating the effects of attenuation to the peak fields measured by the sensors. PDF File (862 KB)

Schulz W., Diendorfer G.: EUCLID network performance and data analysis

17^th International Lightning Detection Conference (ILDC), Tucson, Arizona, 2002 In fall 2001 six European network operators together with Global Atmospherics Inc. (GAI) founded EUCLID (EUropean Cooperation for LIghtning Detection). Currently the EUCLID network consists of 12 LPATSIII, 17 LPATSIV, 33 IMPACT and 25 IMPACT ES/ESP sensors. Due to the fact that the network configuration is very inhomogeneous it is important to monitor and compare the performance in the individual areas of the network. In this paper we will present the current EUCLID network configuration and also a detailed performance analysis. We will further show some drawbacks of the interconnection which small individual networks do not face. Further first results of lightning parameter variations within the EUCLID network are presented. PDF File (1,3 MB)

Diendorfer G.: EUCLID - Technical Structure and Performance of the European wide Lightning Location System

International Conference on Grounding and Earthing & 3^rd Brazilian Workshop on Atmospheric Electricity, Rio de Janeiro, Brazil, 2002 EUCLID - the EUropean Cooperation for LIghtning Detection was formally founded in 2001 as a cooperation among operators of lightning location networks in several countries in Europe. Currently the EUCLID network is a composite network utilizing about 100 Vaisala-GAI sensors. Data exchange between the countries is on a cooperation basis. It is also an objective to have a common European forum for discussion, maintenance, technical solutions, and network optimization. The EUCLID network provides lightning data for Europe with homogenous quality in terms of detection efficiency and location accuracy. PDF File (1,1 MB)