Ruihua Song

Electro-magnetic Analysis for 750kV Double Circuit Compact Transmission System When Applying Controllable Shunt Reactor

Presently, CSR has not been applied into 750kV power grid through the worldwide. Based on a planning 750kV double circuit compact transmission project in China, this paper researches some electromagnetic issues such as power frequency overvoltage, secondary-arc current and recovery voltage, and load rejection switching surge characteristics of this system when applying controllable shunt reactors (CSR for short) by EMTP program. Aiming at suppressing the electromagnetic issues below the relevant standards, a kind of operating control strategy for 750kV CSR is put forward in this paper. Thereby, it makes CSR to be able to settle the contradiction between suppressing overvoltage level and improving reactive power equivalence performance effectively, which is helpful to enhance system stability and operation economical efficiency. Because of the merits, CSR has good foreground in EHV and UHV power grid in and abroad.

Mechanism and Mitigation of Power Fluctuation Overvoltage for Ultrahigh Voltage Half-Wave Length Transmission System

A new type of overvoltage phenomenon in half-wave length transmission line (HWLL) is caused by power fluctuation (PF). This paper defines this phenomenon as PF overvoltage (PFO), which belongs to the temporary overvoltage category. The amplitude of PFO is generally high, the duration time is long, and the coverage on HWLLs is wide in the case of single-phase transient fault, when the transmission power is large. This will pose a new problem for ultrahigh voltage (UHV) half-wave length ac transmission (HWACT). First, we analyze the unique transmission characteristics of HWLLs with incident and reflected wave theory. Next, according to the application scenario of HWACT in China, we construct a plant-to-grid UHV half-wave length transmission system. Then, based on a large number of electromagnetic transient simulations on the system using electromagnetic program, we obtain the PF characteristics of the UHV HWLL. Furthermore, the mechanism and characteristics of PFO are described by the characteristics of transmission and PF. Finally, we propose the mitigation measures of PFO for UHV HWLL, which include configuring metal oxide arresters differentially along HWLLs, closing high-speed grounding switches during the fault period, generator tripping after a fault, and shortening the reclosing time.