Lightning Transient Study of a Hybrid Overhead and Underground High-Voltage System

Transient overvoltages encountered by the power system equipment are mainly divided into three types: lightning surges, switch surges, and power frequency overvoltages. This paper presents a transient overvoltage study in a 345 kV hybrid overhead and underground transmission system that serves a high-tech industrial park. Based on the actual system information, the distributed parameter model is adopted to create a 345 kV transmission network in EMTP/ATP for simulations. The high- energy phenomenon and lighting surges are included in the transient study. Then, major criteria suggested by IEEE and IEC standards are used to assess the level of insulation coordination of the hybrid overhead/underground high-voltage system.