The tension compensation device is a critical component for maintaining constant parameters of the contact wire, such as tension, catenary height, and sag, in the overhead contact system. Its operational status directly affects the normal operation of the entire contact wire system. This paper provides a comprehensive review of existing tension compensation device state detection techniques and analyzes their shortcomings. By comparing with existing methods for monitoring cable tension, a vehicle-mounted contact wire tension compensation device state detection system based on the three-point bending method is proposed. This system can simultaneously monitor the operational status of the device at the line side and anchor section, issuing real-time warnings in case of abnormal device states and possessing significant application value. This study provides a reliable tool for railway operators to monitor the devices status and take timely maintenance and adjustment measures to ensure the normal operation of the contact wire system