IEC 62888-1:2018 describes the primary purpose of the Energy Measurement System (EMS), which measures energy consumption on board for applications such as energy management, energy saving, billing and others. It gives requirements for the complete EMS and also requirements for all devices implementing one or more functions of the EMS, applies to newly manufactured EMSs for use on board traction units, powered by AC and/or DC supply voltages as listed in IEC 60850.