Lightning Efficient Counterpoise Configurations for Transmission Line Grounding

Abstract

Different configurations of counterpoises are often used to reduce the resistance and impulse impedance of the transmission line grounding. However, there are no general rules for an actual design. This paper analyses the performance of several configurations of counterpoises under typical lightning current impulses. The basis is a parametric analysis derived from time responses of 11,386 test cases for each configuration with parameters in broad ranges computed using a rigorous electromagnetic model based on the method of moments. The contributions of the paper are: Simple formulas for the resistance, impulse impedance, and effective length of counterpoise configurations are derived from and verified by the simulation results; a configuration with an 8-leg counterpoise bent parallel to the line is proposed, which extends the effective length and is efficient in high resistivity soil; and the method does not depend on the different lightning current impulse waveform representations based on Heidler, CIGRE, and double-exponential formulas, since the results can be easily converted. A simple procedure is provided to compare the capabilities and limitations of counterpoise configurations. New formulas and procedures make up a general and straightforward method for analyzing the optimal design, considering the cost-effective and best protection against lightning.