Energy transmission by high voltage direct current - HVDC - is steadily increasing in the world, both at the highest power levels, but also at medium power, for example in connections of remote wind-parks to the main a.c. grid. Although principles for d.c. side measurements are known since long, support from metrology is not on par with the needs. An overview of available technologies and the challenges for metrology shows that advances are needed in determination of power losses in convertors, traceability for transmission line voltage measurement, power quality and d.c. side metering. Response to these challenges is given by seven national metrology institutes, one university and one industrial partner, in a project funded by the European Union under Article 169. The research will provide traceable calibrations and measurements in the assigned areas, and capability of measurement will extend to transmission line levels including 1000 kV d.c.