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The lightning transient calculation is carried out in this paper for photovoltaic (PV) bracket systems. The electrical parameters of the conducting branches and earthing electrodes are represented by resistances, capacitances, and inductances. A set of formulas are derived to evaluate the electrical parameters, which are appropriate for the complicated spatial locations of the conducting branches. On the basis of the electrical parameters, the equivalent circuits are constructed for the segmented branches and electrode units in a PV bracket system. By integrating all the equivalent circuits, a complete circuit model is built for the PV bracket system. The lightning transient responses can be obtained from the circuit model. In order to confirm the validity of the circuit model, experimental measurement is made with a reduced-scale PV bracket system and the measured results are compared with the calculated ones. Then, an actual PV bracket system is used as the numerical example. The lightning transient responses are calculated for typical locations of attachment points. The distribution characteristic of lightning transient responses is also explored in the PV bracket system. INDEX TERMSModeling, lightning transient, photovoltaic, bracket system, lightning protection. the School of Electrical Engineering, Beijing Jiaotong University, where he is currently a Senior Research Fellow. He has authored six books and more than 50 articles. His research interests include high voltage insulation, lightning protection, and electromagnetic transient simulation.

A calculating method is proposed for lightning transient analysis in photovoltaic bracket systems. The circuit parameters are evaluated for the conducting branches and grounding electrodes. On the ground of the circuit parameters, the equivalent circuit model is set up for photovoltaic bracket systems. The transient calculation is made by the circuit model and the potential and current responses are obtained in photovoltaic bracket systems. The laboratory-experiment is performed on a reduced-scale photovoltaic bracket system. The results obtained from the measurement are compared with those from the transient calculation to confirm the validity of the circuit model. Then, the probability density function of lightning current is further introduced into the statistical analysis of lightning transients. By means of the transient calculations made in a large interval of lightning current amplitudes, the statistical values of the nodal potential and branch current amplitudes are calculated by probability weights. A numerical example is also given for examining the difference between the statistical and non-statistical values. The proposed method can take account of the actual randomness of lightning discharge and afford a sound basis for lightning protection design of photovoltaic bracket systems.

An exploration on the grounding characteristic of monopile foundation offshore wind turbines (WTs) is carried out in this paper by using the Grounding System Safe Analysis Software (GSSAS). A basic description is given for the structural feature of the monopile foundation. The discretization model is built for the monopile foundation by subdividing its continuous shell body into a discrete multiconductor system. The simulation computation is performed for analyzing the actual factors influencing the grounding resistance, including the seawater depth, thickness of clay layer, and resistivity of gravel layer. It is found from the simulation computation that the grounding resistance is mainly influenced by the seawater depth. Then, the result obtained from the software GSSAS is also compared with that from the software current distribution, electromagnetic fields, grounding and soil structure analysis for checking the validity of the GSSAS simulation in the exploration of grounding characteristic of offshore WTs.