Lightning protection, earthing and surge protection of base transmission stations
An effective lightning protection design for a telecommunication facility requires an integrated approach to a number of key factors: • Protection against direct lightning strikes • Effective earth termination network for discharge of lightning current • Integration of power supply and lightning protection earthing systems • Extensive equipotential bonding to prevent electric shock • Mitigation for ground potential rise • Prevention of conducted surges to equipment cabin • Mitigation of LEMP This paper examines the challenges and solutions in the integration of lightning protection, earthing and surge protection for a base transmission station comprising a telecom tower and an equipment cabin, taking into consideration external power source via overhead lines.
Determination of the Electric Capacitance of the Overvoltage Protective Shield of an Electric Transformer
The paper presents an approach for computing the electric capacitance of the overvoltage protective shield mounted in electric transformers. This is a valuable parameter within the high frequency equivalent electric circuit of a transformer stressed by an overvoltage wave propagation due to a lightning strike event. The finite element analysis method is applied to solve the resulting electrostatics problem.
Geomagnetic Polarity Epochs: Sierra Nevada Data, 3
Available paleomagnetic and radiometric results for about 60 igneous rocks 3.6 m.y. old or less are consistent with the following geomagnetic polarity epoch time scale: Brunhes normal polarity epoch, 0.0 to 0.85±0.15 million years; Matuyama reversed polarity epoch, 0.85±0.15 to 2.4±0.1 million years; Gauss normal polarity epoch, 2.4±0.1 to 3.35±0.1 million years; Gilbert reversed polarity epoch, 3.35±0.1 million years to (?). A brief interval of normal polarity (the Olduvai event) occurs within the Matuyama reversed epoch at about 1.9 m.y., and a brief interval of reversed polarity (the Mammoth event) occurs within the Gauss normal epoch at about 3.06 m.y. Data for twelve units from eastern California and Nevada, reported here for the first time, are particularly useful in defining the Gauss-Gilbert boundary and for recognizing the Mammoth event.