Abstract: Primary-secondary integrated switchgear is a core piece of equipment for the intelligent transformation of medium and low voltage distribution networks, and the reliability of its measurement transmission and transformation directly determines the monitoring accuracy and fault disposal capability of the distribution automation system. Fully identifying the failuer modes of the measurement and transformation system helps in formulating targeted preventive and improvement measures, thereby reducing the risk if failure. A failure characterization index system for switch measurement transmission and transformation is established covering the acquisition, communication and protection links. The failure mechanisms such as measurement distortion, communication bit errors and protection maloperation caused by the coupling of multiple factors including electromagnetic interference, extreme temperatures and mechanical vibration, as well as the key identification difficulties in each link, are analyzed. A hierarchical failure mode identification method based on FMEA is proposed, and four main types of failure modes existing in the measurement transmission and transformation links of the equipment are identified through RPN quantitative scoring. This research can provide key technical support for the condition perception and predictive maintenance of primary-secondary integrated switchgear.