Analysis of Effect of System Configuration and Parameters on Energization Overvoltage in 330kV Hybrid OHL-Cable System

The increasing tendency in the application of power cables in EHV(Extra-High Voltage) underground cables has resulted in plenty of OHL(Overhead Line)-Cable hybrid systems in urban areas of China. It is expected that the transient characteristics of a hybrid OHL- Cable system is significantly different from a pure OHL or cable system. Energization overvoltage are among the severest overvoltage stressing insulations of EHV power system components. Therefore, studying energization overvoltage is of great importance of technical operation and reliability of the OHL-Cable hybrid systems. Switching a hybrid system requires careful risk assessments, mainly considering cable proportion, line configurations and sheath-bonding method. The study is carried out for different cable proportions and line configurations in the case to identify how cable proportion and line configuration in the 330kV hybrid system influences the overvoltage due to noload energization. In addition, this paper analyzes the effect of sheath-bonding method on the amplitude and frequency characteristics of induced overvoltage in 330kV hybrid OHL-Cable system to identify the optimal sheath- bonding method in 330kV hybrid system. The study is carried out on a distributed frequency-dependent parameter model of the Xi'an 330kV grid in ATP-EMTP. The study shows that the large energization overvoltage in hybrid line can be lower by increasing cable proportion and adopting the line configuration that overhead line in front and cable behind. Besides, the sheath-bonding method—cross-bonding and directly grounding can reduce the sheath overvoltage due to energization in the 330kV hybrid OHL-Cable system.