Lightning protection zone in substation using mast

Abstract

This paper proposes zone apportionment algorithms (ZAA) to apportion lightning protection zonegenerated by mast. Mast may be used to protect equipment within substation against lightning. Lightning distance equations are used to determine striking distance to ground, object and mast. The calculation of corresponding protection zone is sophisticated especially when more masts are used. ZAA is proposedto apportion the lightning protection zone generated by 1–4 mast(s), calculate the critical protection height at each point, and create a three dimension protection volume to be visualized. Each point of equipment is laid out in substation with its height. Then, the equipment height at each point is compared with the corresponding critical protection height to determine whether equipmentareprotected or not.The risk part of unprotected equipment will emerge above the comparable protection roof and be visualized clearly. This will help engineers to understand the protection zone thoroughly and ensure that equipment are protected. ZAA algorithms are tested on a 30 m x 30 m substation protected by 1–4 mast(s)located outside substation with height of 32 m, 17 m, 14 m and 13 m, respectively. Equipment are located at the center of substation. Calculation from ZAA indicated that equipment with size 10 m x 10 m should not be higher than 10.14 m, 10.28 m, 10.26 m and 10.97 m in case of 1–4 mast(s), respectively. For larger equipment, with size 12 m x 12 m, they should not be higher than 9.31 m, 9.59 m, 10.26 m and 10.97 m in case of 1–4 mast(s), respectively. Numerical results indicated that the proposed algorithms, ZAA could identify the unprotected part of equipment correctly and produce a three dimension protection volume with emerging of the unprotected part of equipment. ZAA could verify the lightning protection correctly in all cases.