The Energy Measurement System is intended for metering for billing and may also be used for metering for energy management, e.g. energy saving. This part of EN 50463 gives general descriptions and requirements for the complete Energy Management System and also requirements for all devices implementing one or more functions of the energy Measurement System and applies to newly manufactured Energy Measurement Systems for use on-board railway traction units, 90 powered by a.c. and/or d.c. supply voltages as listen in the EN 50163.