Abstract: A positive electrode active material includes a lithium composite transition metal oxide. The positive electrode active material is a secondary particle in which primary particles are aggregated. The primary particle includes a coating portion containing an M1 metal, and the coating portion is locally present on surfaces of the primary particles or at inter-particle boundaries of the primary particles. A preparation method thereof, and a lithium secondary battery including the positive electrode active material are also provided.

Abstract: Disclosed are a high-voltage direct current (HVDC) cable partial discharge diagnosis system and method. The HVDC cable partial discharge diagnosis system according to one aspect of the present invention comprises: a sensor provided on an HVDC cable; a plurality of HVDC cable partial discharge measurement devices for acquiring measurement result information from the sensor and detecting a partial discharge signal from the measurement result information; and an HVDC cable partial discharge diagnosis device which receives the partial discharge signal from the HVDC cable partial discharge measurement devices and diagnoses whether partial discharge has occurred in the HVDC cable, through pattern analysis of the partial discharge signal.