영동권 실 계통 PMU 측정정보를 활용한 울진, 삼척 산불 시 SSR 위험성 검토

Abstract

The role of the power grid in the power system is to transmit the power produced at the power generation sites to the demand sites without interruption. When a new power source plan is established, a new power grid plan is also established so that necessary power grid construction is carried out at an appropriate time. However, the construction of a new power grid is not easy due to the problem of location selection and economic reasons. For this reason, efforts have been made for a long time to find ways to increase the capacity of the grid to avoid the construction of the new grid. A typical one of them is a method of increasing power transmission capacity by compensating the series capacitive impedance of the power transmission network. Therefore, KEPCO, in response to the delay in the construction of a new power grid for the construction of a large-scale power generation complex in the Yeongdong area, it was decided to increase the power transmission capacity of the existing power grid through series capacitive impedance. However, there is a risk that such an increase in transmission capacity through impedance compensation may cause problems such as sub synchronus resonance (SSR). In case of SSR, occured when the resonance frequency of the impedance-compensated power grid coincides with the mechanical resonance frequency of the nearby generator, and if a mechanical burden is accumulated on the generator shaft, the shaft may break. For this reason, the power authorities reviewed the risk of SSR and installed thyristor controlled series capacitor (TCSC) based on the results to avoid dangerous frequency bands by adjusting the apparent impedance of the impedance-compensated transmission line. In this way, the risk of SSR was responded to through sufficient preparation for impedance compensation. However, in the case of wild fires in Uljin and Samcheok, which occurred in March 2022, a number of transmission lines were opened, and the network topology between the compensation line and the nearby generator approached the condition of SSR, increasing the risk of resonance. This paper analyzes the risk of actual SSR based on the system configuration during wildfires in Uljin and Samcheok and the system operation information obtained through the Phase Measurement Unit (PMU) located nearby sites.