An Evaluation Algorithm of Transient Grounding Impedance with Grounding Types in Distribution System

Recently, the researches on lightning and surge protection system are being actively conducted due to development of the information technology and large scale interconnection of renewable energy sources in power distribution system. Because the exsiting methods have dealt with prevention of human electric shock and equipment protection only considering reference frequency when the faults such as grounding and short-circuit are occurred, operation method of grounding impedance considering both reference and transient frequencies is being required. Therefore, this paper presents a calculation method of transient grounding impedance in rods and mesh grounding types to evaluate the transient grounding impedance in high frequency bandwidth, and proposes an evaluation algorithm to reduce the transient grounding impedance. Where, the proposed algorithm calculates grounding impedance in both reference and transient frequencies, and designs proper configuration of rods and mesh grounding types in order to meet the code of KEC. And also, this paper performs the modeling which is composed of distribution system, PV system and detecting device of transient grounding impedance using PSCAD/EMTDC S/W. From the simulation results based on the evaluation algorithm and modeling, it is confirmed that the proposed algorithm is useful tool to maintain the transient impedance and surge current within the allowable limit in KEC code. Copyright © The Korean Institute of Electrical Engineers.