This Recommendation provides guidelines for electrical safety and lightning protection requirements for medium voltage power electronic converter systems, which has medium voltage input with rated system voltages from 1 000 V AC up to 36 kV AC and low voltage output with rated voltages up to ±400V DC, used in ICT data centre, telecommunication centre, or other application environments. With the development of big data and cloud computing technology, the quantity and total capacity of the data centres and telecommunication centres together with ICT equipment power densities are increasing rapidly. In this condition, it was found that the traditional power distribution equipment and power systems had the disadvantages of low energy efficiency, high energy consumption, high maintenance difficulties, high cost in lots of existing data centres and telecommunication centres. In order to solve the problems above, it is necessary to develop a new structure of whole power system, which may be powered directly by medium voltage and based on power electronic conversion. From the perspective of electrical safety and lightning protection, there are lots of differences between the data centre and telecommunication centre powered by traditional low-voltage AC and that of powered by medium voltage. This Recommendation will be focused mainly on electrical insulation, partial discharge, electrical safety, resistibility and lightning surge protection.