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8th World Conference on Photovoltaic Energy Conversion; 527-532, The energy rating IEC 61853 Standard series “Photovoltaic (PV) module performance testing and energy rating” provides a standardized measure of the performance of PV devices considering real working conditions of ambient temperature and irradiation, representative of worldwide reference climates relevant for PV installations. The Climatic Specific Energy Rating (CSER) parameter defined in the standard could serve as a tool for the comparison of PV technologies and devices. The scope of this paper is the validation of the ability of the CSER to differentiate between PV technologies and devices of the same technology, evaluating how much of the observed differences are due to uncertainties in the estimation chain or input data other than the result of the intrinsic behavior of the considered devices. Ten devices representative of commercially available PV devices have been analyzed. The observed differences, higher than the associated uncertainty in the estimation of the CSER parameter, indicates the ability of the standard to differentiate between different technologies and devices of the same technology. Furthermore, the variability in the estimated performance depends on the climatic conditions.

8th World Conference on Photovoltaic Energy Conversion; 731-734, A double-sided solar simulator based on an existing large-area long pulse flash solar simulator and a low-cost LED-based rear bias light has been developed at European Solar Test Installation (ESTI) (Joint Research Centre, European Commission) for studying and validating the double-side indoor testing approach for current-voltage (I-V) characterization of bifacial modules. “Self-reference” methodology is applied using an accredited reference values (ISO/IEC 17025) obtained by single-side illumination. The proposed approach and prototype LED simulator for full size modules has demonstrated adequate performance in comparison with the single-side measurements based on a commercial Class AAA simulator using validated standard methodology. The electrical performance expressed in similar current-voltage (I-V) curves and power output reveals the suitability of the method for characterization of bifacial devices. The LED bias light source could be classified as a “Class C” solar simulator. The analysis of different representative bifacial PV devices available on the market shows different electrical behaviour according to their bifaciality factor.

38th European Photovoltaic Solar Energy Conference and Exhibition; 371-374, Emerging photovoltaic (PV) technologies like organic (OPV) and dye-sensitized (DSC) devices are rapidly evolving and considerable research effort has addressed various approaches to increase their efficiency, reaching in the last years promising values. Examples of large area DSC modules for outdoor installation have been showcased by different manufacturers and proposed for multiple applications. Here we present an indoor calibration of a large area DSC PV device, at standard test conditions (STC), through I-V measurements and the determination of the spectral responsivity following the procedures described in IEC 60891 and 60904 standards. Initial measurements have focused on the analysis of the module time response to light stimulus and on the necessary pre-conditioning step to ensure a reliable calibration at steady state conditions. Then the electrical performance was measured at STC, at irradiances from 100 W/m2 to 1000 W/m2 (at 25 °C) and for temperatures from 10 °C to 50 °C (at 1000 W/m2).

38th European Photovoltaic Solar Energy Conference and Exhibition; 594-601, This work presentsthe comparison of measurement resultsfor four types of encapsulated high efficiency (HE) c-Si solar cells measured by ten laboratories based in Asia, Europe and North America utilizing a wide range of voltage sweeping methods, which include well-established procedures that represent good industry practice, as well as recently introduced ones that have not been verified yet. A proficiency test was employed to examine the consistency of results and their corresponding uncertainties. The results of all participant laboratories generally remained well within [−1; 1], thus indicating consistency between the measured values and the reference values within stated measurement uncertainties. A preliminary analysis revealed that differences remained within ±1.15% in PMAX and within ±0.35% in VOC for all participants and methods applied. Essentially this work forms the basis to validate all applied methods and their stated measurement uncertainties.

37th European Photovoltaic Solar Energy Conference and Exhibition; 1126-1129, This work reports on the classification of the APOLLO large-area steady-state solar simulator at the European Solar Test Installation and a wide range of measurement procedures implemented for the characterisation of electrical performance of PV devices. The simulator is class AAA and allows measurement of electrical performance over a wide range of irradiance and device temperature (e.g. power matrix). Furthermore, bi-facial PV devices as well as emerging PV technologies can be measured and last not least linearity.

37th European Photovoltaic Solar Energy Conference and Exhibition; 877-882, Bifacial Photovoltaic (PV) technology is expected to acquire an increased market share of the solar PV industry in the future, due to the ability of bifacial PV modules to collect light from both the front and rear side, increasing the energy yield for a specific available area for a PV system. Accurate measurement procedures for bifacial products result in more accurate energy yield estimates, consequently improving the bankability of bifacial PV technology. This work aims to evaluate the procedures for the measurement of electrical power and bifacial parameters of bifacial solar devices, concerning to their applicability in calibration laboratories and production line environments. An intercomparison for bifacial PV cells and modules is carried out between nine different test laboratories across Europe, as part of the PV-Enerate project. The measurement procedures as described in IEC TS 60904-1-2:2019 are followed among the different test laboratories, to evaluate the applicability of these procedures. Three different types of bifacial PV cells and three different types of bifacial PV modules are measured. The intercomparison involves measurements with systems using both single and double-sided illumination conditions. The uncertainty budgets and systematic differences that these procedures result in between different laboratories are determined and discussed. Specific common mistakes are reported and improvements to the IEC TS 60904-1-2:2019 are proposed as a result of this intercomparison activity.

A round‐robin proficiency test (RR PT) on thin‐film multi‐junction (MJ) photovoltaic (PV) cells was run between 13 laboratories within the European project CHEETAH. Five encapsulated PV cells were circulated to participants for being tested at Standard Test Conditions (STC). Three cells were a‐Si/mc‐Si tandem PV devices, each of which had a different short‐circuit current ratio between the top junction and the bottom one; the remaining two cells were single‐junction PV devices made with material representative of the individual junctions in the MJ cells. The RR PT's main purpose was to assess the capability of the participating laboratories, in terms of employed facilities and procedures, to test MJ PV devices. Therefore, participants were requested to perform STC measurements of all cells according to their own procedure, which might not include external quantum efficiency measurements. The European Solar Test Installation (ESTI) of the Joint Research Centre (JRC) provided the reference calibrations against which the participants' results are compared. ESTI made also a verification of the cells performance at STC at the end of the RR PT, in order to allow a comparison between the initial stable state at which the cells were calibrated (just before circulation) and the one they had reached at the end of the RR PT. The overall results of the RR PT are here presented and discussed together with some aspects of MJ PV testing that emerged as not adequately applied or largely missing. Their full implementation is expected to improve the consistency of future results.

36th European Photovoltaic Solar Energy Conference and Exhibition; 1158-1164, Photovoltaic (PV) market is increasing year on year and the manufacturers, promoters and owners are becoming more interested in the reliability and lifetime of their modules and systems. For this reason, it is important to analyse the degradation mechanism and failures modes of PV modules that have been exposed in the field for long periods of time. Some of these defects only appear in normal operation conditions as they are not always produced in reliability or accelerating tests such as IEC 61215 and IEC 61646. This work analyses by means of detailed visual inspection, electroluminescence, thermal imaging and I-V curves using a solar simulator, the defects, failure mechanisms, performance losses and degradation under real outdoor conditions of several c-Si (HIT, back contact and polycrystalline Si) and Cu(In,Ga)Se2 (CIGS) PV modules exposed outdoor between 9 and 11 years without cleaning. The aim is to obtain a better understanding of the defects affecting different technologies and their evolution into degradation and failures. In addition to this, the effects of soiling in the performance of the modules were also studied.

Within the European FP7 project CHEETAH, a thin-film tandem solar cell round-robin proficiency test was conducted between 13 testing laboratories, plus the European Solar Test Installation (ESTI) of the European Commission's Joint Research Centre as reference laboratory. The purpose of this RR was to compare testing facilities and procedures of the involved partners against the reference measurement by ESTI. In total, five cells were measured. Three tandem devices (a-Si:H/μc-Si) and a single-junction device representing the top (a-Si:H) and the bottom (μc-Si) cells, respectively, were provided by one partner. All cells (with active area of 1 cm2) were mounted in a standardised housing with connection sockets for I-V measurements and a Pt-100 temperature sensor. The cells were initially stabilised and calibrated at ESTI and afterwards circulated. The characterisation was done by I-V measurements at Standard Test Conditions and EQE measurements. ESTI checked and re-calibrated the cells at the end of the RR before and after further stabilization. Here we report on some preliminary I-V measurement results. A number of acquired or conversely still necessary improvements are discussed for the organisational point of view along with some measurement requirements that are still missing or that are not sufficient at many participating laboratories.

35th European Photovoltaic Solar Energy Conference and Exhibition; 1363-1367, The interest on bifacial c-Si PV modules has increased in the last years since they can increase the performance in comparison to traditional PV modules. However, one of the main issues to correctly measure bifacial modules is still a lack of standardisation. High-efficiency PV modules such as bifacial ones may have a significant internal capacitance which can result in I-V measurement artefacts due to transient effects when measured with short pulse durations in conventional pulsed solar simulators and lead to inaccurate output power measurements. Furthermore, the calibration of PV modules requires the measurement of their I-V characteristics at Standard Test Conditions (STC), which involves a curve translation, requiring among others the internal series resistance Rs of the module. Rs influences the module maximum power Pmax, indicating in some way the quality of the device. This work analyses the capacitive effects on commercially available bifacial PV modules measured with conventional pulsed solar simulator, their influence on the output power accuracy and the variation of internal series resistance of the front and rear side of the module.

35th European Photovoltaic Solar Energy Conference and Exhibition; 912-916, The PV market is currently dominated by crystalline silicon based technologies. However, the emerging thin-film technologies show the potential to compete with them in the future, due to the improved efficiencies and increased lifetime reached. Examples of printed large-area OPV modules have been produced by different companies. There is a clear need of guidelines and protocols on how to perform a reliable calibration of these devices. In this work we present a practical example of a calibration of a large-area OPV module performed indoor under a solar simulator following the procedures described in IEC 60891 and 60904 standards. Preliminary results about a power matrix measurement study performed indoor with the same OPV module under a steady-state large-area solar simulator are also presented.

33rd European Photovoltaic Solar Energy Conference and Exhibition; 1544-1547, Results from calibrations to determine the power conversion efficiency of photovoltaic (PV) devices can differ if they are obtained using different calibration methods or different facilities. However, every calibration value has a measurement uncertainty. The consistency of the calibration results around the world is a major task of metrology institutes and calibration laboratories and is ensured by regular comparisons. However, one important parameter of performance measurements of PV devices is the short-circuit current under standard test conditions ISTC. Therefore, the ISTC of an ensemble of reference solar cells were calibrated at the Joint Research Centre (JRC), at the Physikalisch-Technische Bundesanstalt (PTB) and at Centre for Renewable Energy Systems Technology (CREST) of Loughborough University (LU, United Kingdom). The determined ISTC of CREST and PTB are consistent within the uncertainties. Additionally, the spectral responsivities of the reference solar cells were determined at the facilities of JRC and PTB and the results discussed.

33rd European Photovoltaic Solar Energy Conference and Exhibition; 1354-1358, Results from traceable calibrations of PV reference cells are compared. Two primary calibration methods were used, namely the differential spectral responsivity (DSR) method at the Physikalisch-Technische Bundesanstalt (PTB) and the direct sunlight method (DSM) at the European Solar Test Installation (ESTI). Furthermore, secondary calibrations were also made at ESTI against the World Photovoltaic Scale (WPVS). The calibration of c-Si reference cells is well established. Here we investigate the extension to filtered c-Si reference cells. Calibrations were performed on three cells. One unfiltered c-Si reference cell was used for control, confirming the good agreement in the calibration of such devices reported previously. Furthermore, two filtered c-Si PV reference cells were calibrated using the same methods. The agreement between the methods is studied and possible sources for discrepancies are investigated. The spectral mismatch correction is identified as crucial factor. The variation in the spectral mismatch correction with variation in measurement of spectral responsivity is found to be within uncertainty limits, whereas the measurement of spectral irradiance of the simulator can contribute much larger uncertainties due to artefacts in the spectral region around 1050 nm. A correction of the measured data alleviates the effect, so that the equivalence of all methods is demonstrated.

33rd European Photovoltaic Solar Energy Conference and Exhibition; 1432-1437, The interest on the n-type crystalline silicon bifacial PV modules has increased in the last years since they can increase the performance in comparison to traditional PV modules. As the PV modules are generally sold according to the nominal power output and efficiency under standard test conditions STC, the lack of standards for bifacial modules leads each manufacturer to claim different amounts for the "added value" of the bifaciality that makes it difficult for customers to directly compare between bifacial manufacturers. In this work, we have compared the electrical performance of framed and frameless c-Si bifacial modules from 5 different manufacturers utilising rear covers of different reflectivity and different measurement methods such as a single-sweep flash simulator, the so-called multi-flash (MF) method, a largearea steady state sun simulator and under natural sunlight for the accurate measurement of the module parameters. It was observed that depending on the measuring method, some modules presented STC front power out of the tolerance range given by the manufacturer. The design of the module also plays an important role on the rear power contribution.

33rd European Photovoltaic Solar Energy Conference and Exhibition; 11-17, The international standard IEC62670-3 "Photovoltaic Concentrators (CPV) Performance Testing – Part 3 - Performance Measurements and Power Rating" sets the guidelines for power measurement of a CPV device, both under indoor and outdoor conditions. When measuring under outdoor conditions, the acquired data have to be filtered “a posteriori”, in order to select only those points measured with ambient conditions close to the Concentrator Standard Operating Conditions (CSOC). The most stringent requirement to be met is related to the three Spectral Matching Ratios (SMR), which have all to be within the limit of 1.00 ± 0.03. SMR are usually determined by the ratio of the currents of component reference cells set to monitor the outdoor spectral ratio conditions during the CPV device power measurements. Alternatively the SMR can be calculated from measured spectral irradiance if the spectral responsivities of the junctions are known. Experience demonstrates that obtaining real world data meeting these strict conditions is very difficult in practise. However, increasing the acceptable range would make the entire filtering process less appropriate from a physical point of view. Given the importance of correctly measuring the SMR, an estimate of their associated measurement uncertainties is needed to allow a proper assessment of the validity of the 3% limit. In this study a Monte Carlo simulation has been used, to allow a preliminary estimation of the propagation of uncertainties for SMR measured with a calibrated spectroradiometer. The method consists of applying both random and wavelength correlated errors to the measured spectra and to the spectral responsivities of the three CPV cell junctions, accordingly to the measurement uncertainties of the European Solar Test Installation (ESTI). The experimental data used in this study have been acquired during clear sky conditions in May 2016, at ESTI's facilities in Ispra, northern Italy (45°49N 8°37E ). Several considerations are then inferred in the case of SMR measured with component reference cells.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 1130-1135, In this work we propose a procedure for the calibration of slow responding PV devices which allows for an accurate evaluation of their response time and, consequently, for a reliable calibration fulfilling all requirements specified in the standards (IEC 60891 and IEC 60904 series). The application of this procedure to the case of three dye-sensitized solar devices (one single cell and two mini-modules) is presented. The spectral responsivity (SR) measurements were performed at 1 Hz chopping frequency. The low chopping frequency resulted from an analysis of the device time response. To ensure reliable electrical characterization, current-voltage measurements were performed using different sweep-times in both the forward and reverse direction. By comparing these measurement results, a reliable evaluation of the appropriate sweep-time for I-V characterization was determined. Combining appropriate SR and I-V measurements yielded a calibration of these devices according to the IEC 60891 and IEC 60904 series of standards.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 1701-1710, Progress in production and installation of high-efficiency (HE) photovoltaic (PV) modules has made the accuracy of their power rating and hence calibration increasingly important. This work presents the comparison of measurement results for eight HE c-Si PV modules performed at six European and Asian laboratories over a wide range of measurement methods, which include well established procedures that represent good industry practice, as well as recently introduced ones that have not been verified yet. A preliminary analysis revealed that differences in PMAX remained within 1.5% for all participants and methods applied. Furthermore, the results obtained through steplike methods like DragonBack® and dynamic IV are compared to the standard procedures, which foresee long-pulse solar simulators, multi-flash method or measurement under natural sunlight. The high correlation of deviations between ISC and PMAX shows that differences can be largely attributed to reference irradiance measurement. The SR comparability of measurements is also examined showing an agreement within 4% for all participants in the range of 400-1100nm.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 1724-1729, Bifacial PV modules have shown the potential to increase the performance of traditional photovoltaic module architectures using relatively conventional silicon manufacturing techniques. Bifacial modules can produce additional energy from the rear surface of the module, collecting not only light incident on the front surface but also sunlight scattered or reflected from the ground or environment onto the rear surface. To assess their performance and quality, PV modules are characterized using international standards to rate the modules in terms of output power and efficiency. However, at present, no specific standards exist for bifacial modules. Furthermore, these modules are often characterized by a high efficiency and an increased capacitance and the measurement with standard pulsed solar simulators may be affected by strong measurement artefacts resulting in increased or reduced maximum power. This work presents the indoor characterisation of bifacial c-Si PV modules under varying irradiance levels using different methods such as a single-sweep flash simulator, the so-called multi-flash (MF) method and a steady state sun simulator for the accurate measurement of the module parameters. The effect of different rear surface coverings, from matt black painted wood to gloss white card and the differences among the characterisation method are also investigated.

31st European Photovoltaic Solar Energy Conference and Exhibition; 1952-1958, Accuracy and reliability in the determination of series resistance RS of PV devices is an important issue, not only in industrial production environment, because of the parasitic and power consuming nature of this intrinsic parameter, but also in measurement and test laboratories, due to its influence during the translation of measured IV curves to reporting conditions. This work follows standard IEC 60891 ed.2 (2009) for the determination of the internal series resistance and focuses on the repeatability of the result and its uncertainty. The latter is studied in particular considering a possible variation of device temperature during the I-V measurements for the RS determination. An analytical expression is derived for quantifying the additional apparent series resistance RS due to temperature variation. Experimental results confirm the derived expression. Although the standard IEC 60891 ed.2 (2009) states that a constant device temperature is required during the I-V curve measurements, it sets the limits for stability within ±2°C. Here it is found that this would lead to a deviation RS, which is comparable to RS itself. However, if the temperature variation is limited to ±0.1°C, which is achievable on pulsed solar simulators, the deviation of RS is limited to ±5%. The repeatability of RS was found to be typically better than 5%. Conservatively, simply adding the two components, the overall combined expanded uncertainty (k=2) for the determination of RS is found to be ±10%. It is recommended to revise IEC 60891 ed.2 concerning the device temperature during determination of RS.

29th European Photovoltaic Solar Energy Conference and Exhibition; 3456-3460, The large variety of photovoltaic (PV) technologies today available on the market makes the characterization of the spectral content of the used light sources a key parameter for calibration and energy yield estimation of PV devices. The use of pulsed, artificial light sources is spread worldwide but these solar simulators have the disadvantage of producing light beams with a spectral content rather different from the Air Mass 1.5 global (AM1.5G) standard spectrum, thus requiring a careful correction of the spectral mismatch between actual and standard spectral conditions. The spectral mismatch correction factor (SMM) may be difficult to apply in the PV module calibration process if reference and calibrating devices have different spectral responsivities and/or if the calibrating device is a multi-junction one. This paper describes the comparison results on the spectral measurements of two ESTI's pulsed solar simulators performed by teams from two ISO 17025 accredited PV calibration laboratories. The two fast spectroradiometer systems of the labs, calibrated and traceable to SI units, were used for the purpose. Moreover, the impact these results may have on a multi-junction thin film PV module calibration will be analysed and reported.

28th European Photovoltaic Solar Energy Conference and Exhibition; 3649-3655, This article presents a taxonomical analysis of the sky conditions, during 2012, for two different sites: the Joint Research Centre site in Ispra (Italy, European Solar Test Installation laboratories) and the site of Brookhaven National Laboratories in Upton (NY – USA). The key parameter is the sky clearness index kT, a dimensionless ratio of the global horizontal irradiance. In the first part, a taxonomical description using daily values of kT is presented, giving a general overview of the sky conditions during the year. In the second part the analysis is performed using short-term averages of the clearness index; remarkable properties of the statistical functions are highlighted and reinforced by using a fuzzy logic method, to extract time independent and site independent subsets. In the third part, a statistical analysis of the clouds intercepting the Sun’s trajectory is given, and finally, in the fourth part, some time-dependent correlations between the irradiance and other meteorological variables are studied.

27th European Photovoltaic Solar Energy Conference and Exhibition; 3677-3683, The measurement of the IV curve at Standard Test Conditions plays a key role in performance analysis and maximum power determination of PV modules. Accredited laboratories must give the result of the measurement with the measurement uncertainty; the coverage factor and probability density function must also be specified. The major contributions to the overall uncertainties budget when measuring an IV curve indoor with a pulsed solar simulator are the optical uncertainties, the reference cell calibration uncertainty and the spectral mismatch uncertainty. In this analysis the optical measurement error has been described as the difference between the irradiance value measured by the reference cell and the effective irradiance values on the module surface. The geometrical parameters identified as source of errors have been modeled as random variables, with different probability density functions, and the resulting error function has been computed with 1 000 000 Monte Carlo trials. Particular configurations have been considered in order to identify what parameters among the set have more influence on the final uncertainty; their statistical estimates and probability density functions give informations about their propagations through the measurement system. The results of simulations with real conditions have finally been compared with the GUM method.

27th European Photovoltaic Solar Energy Conference and Exhibition; 3027-3032, A new measurement campaign which focuses only on thin film module performance was started at SUPSI at the beginning of 2011. A selection of 11 different thin film module technologies (a-Si, a-Si/a-Si, a-Si/μc-Si, CdTe, CIS, CIGS, CIGSS) have been exposed outdoors together with some crystalline silicon modules. This paper presents some results about the initial degradation of thin film modules, the stability of the efficiency curves (G) and maximum power temperature coefficient over time, the kWh/Wp inter-comparison with the modeling of the thin film module performance respect to the crystalline silicon module, and the accuracy achieved by the introduction of average photon energy (APE) for the description of spectral effects. The approach to extracting APE dependencies from outdoor data, as well as some of the main open issues to the further improvement of the energy prediction accuracy of thin film modules, are presented.

26th European Photovoltaic Solar Energy Conference and Exhibition; 3450-3453, In this work the authors report on the spectral characterization tools in use at SUPSI. Spectral irradiance data are measured with a 3-channel long range fast spectroradiometer. Spectral response measurements of single junction PV modules are performed with a setup of target area up to 2.0×2.0 m developed at SUPSI. The calculation of spectral mismatch corrections is carried out from the measured spectral responses and spectral irradiance data. In order to minimize the spectral mismatch for different photovoltaic technologies, these data are also used to make an appropriate choice for the reference cell. Preliminary results on multi-junction modules are also shown.

25th European Photovoltaic Solar Energy Conference and Exhibition / 5th World Conference on Photovoltaic Energy Conversion, 6-10 September 2010, Valencia, Spain; 4248-4252, The operating temperature of a PV module or system is a crucial parameter for its energy output. PV modules are in fact usually rated at Standard Test Conditions (STC = 1000 W/m2, AM1.5, 25°C), but their operating temperatures are usually significantly higher. In order to have an idea of their temperature behavior- an information which may result useful in optimizing the output of a PV system under particular conditions - in the present work we have compared indoor measured temperature coefficients values of several thin film technologies (a-Si based single or multi-junctions, CdTe, CIS, thin-film silicon) with typical TCO’s of a conventional c-Si wafer-based module. With the exception of the thin film Si device (rel = -0.48 %/°C), all thin film technologies have lower values for the rel temperature coefficient for power compared to the c-Si wafer-based module (rel = -0.45 %/°C), with the a-Si single-junction (rel= -0.13 %/°C) device showing the less pronounced decrease with temperature, followed by CdTe (rel= -0.21 %/°C). The microcrystalline and CIGS device investigated in this work have TCO values for power very close (rel= -0.36 %/°C). At least for the single-junction devices, the magnitude of the power temperature coefficient seems to be strongly correlated to the band gaps of the corresponding absorber materials. TCO values presented in this work are in line with data coming from the literature and or from manufacturer’s datasheets. It should, however, be noted that for a given technology a significant spread for TCO values may exist.

23rd European Photovoltaic Solar Energy Conference and Exhibition, 1-5 September 2008, Valencia, Spain; 2818-2821, The IEC standard 60891 describes the translation of measured IV curves from the measured irradiance and temperature to the desired irradiance and temperature. The equations given are applicable for IV curves measured at an irradiance which is constant during the IV sweep. In the case of a varying irradiance during the acquisition of the IV curve, as is the case on pulsed solar simulators with a decaying light intensity, the equations have to be modified. This paper illustrates the limitations of the existing standard, proposes a solution for these cases and provides evidence of its proper functioning.

In this paper, simultaneous GPS time-stamped measurements of the electric and magnetic fields at three distances and of the return stroke current associated with lightning strikes to the Toronto CN Tower during the Summer of 2005 are reported. The lightning return-stroke current was measured using a Rogowski coil installed at a height of 474 m AGL (above ground level). The vertical component of the electric field and the azimuthal component of the magnetic field were measured simultaneously at distances of 2.0 km (Pratt building of the University of Toronto), 16.8 km (Environment Canada Building), and 50.9 km (Grimsby, ON) from the CN Tower. Preliminary discussion on the current-field relation and propagation effects is also provided.

Recently, engineering return stroke models were extended to take into account the presence of an elevated strike object, which was modeled as an ideal uniform transmission line. We show in this paper that the current distribution associated with these extended models exhibits a discontinuity at the return stroke wave front, which cannot be considered to be physically plausible. This discontinuity arises from the fact that the current injected into the tower from its top is reflected back and forth at its ends and portions of it are transmitted into the channel; these transmitted pulses, which are supposed to travel at the speed of light, catch up with the return stroke wave front traveling at a lower speed, and no current is allowed to flow in the leader region above the front. This discontinuity needs to be carefully treated when calculating the radiated electromagnetic field through an additional term in the electromagnetic field equations, the so-called “turn-on” term. We additionally derive a general analytical formula describing the turn-on term associated with this discontinuity for various engineering models. We present simulation results illustrating the effect of the turn-on term on the radiated electric and magnetic fields for an elevated strike object of height h = 168 m, corresponding to the Peissenberg tower in Germany. Finally, possible modifications to engineering models are suggested in order to eliminate this discontinuity.