Abstract: The busbar measurement and control device, as a secondary equipment for collecting and transmitting the voltage and frequency of the 500 kV busbar in substations, plays an important role in the power monitoring and control system. According to the actual case of 500 kV busbar measurement and control device transformation, the article analyzes the impact of three different retrofit schemes for two bus measurement and control devices on the monitoring busbar voltage and frequency of the main station. It also introduces the key points and steps of implementing the optimal retrofit scheme, which reduces the risk of power grid retrofit and has been practically applied on site.