Evaluation of Structural and Functional Behavior of Battery Charger for Low/High-Frequency Motions in NPP

Earthquake damage to electrical systems degrades their performances and disrupts their normal functioning. Furthermore, it disrupts nuclear power plant (NPP) operations. NPPs in South Korea have been designed based on the Regulatory Guide 1.60 (RG 1.60) design spectra; however, the Gyeongju earthquakes in South Korea were of high frequency, with magnitudes of 5.1 and 5.8. Therefore, the seismic performances of electrical systems (high-frequency sensitive) must be evaluated to consider low- and high-frequency motions. In this study, to ensure the operation of NPPs in South Korea, the seismic performance and dynamic characteristics of the battery charger (BC) in the electrical subsystem were evaluated experimentally. Seismic tests of the BC were performed to consider low frequencies, high frequencies and a combination of both. The dynamic characteristics of the inside and outside of the cabinet, depending on the input motions, were evaluated and compared based on the tests. Moreover, the acceptance criteria for relay contact chatter were evaluated using the measured output signal during the seismic tests. From seismic test results, the peak acceleration of CRS at the top location (A6) was 1.31 times larger than that of UHS and 1.51 times than that of RG 1.60 and it increased rapidly with increasing PGA levels. Contact chatter was not observed under a peak acceleration of 3.4 g on the installed relay of the panel; however, the relay chatter for more than 2 ms dropped below the reference voltage 46 times. The major components of the electric cabinet were significantly affected by high-frequency motion