This paper reviews the existing testing techniques for high voltage direct current (HVDC) cable systems

following as a backbone the structure of CIGRE Technical Brochure (TB) 852:2021 ‘Recommendations for testing DC extruded cable systems for power transmission at a rated voltage up to 800 kV’ because it has a fairly similar structure to CIGRE TB 853:2021 for lapped DC cables

and especially because of the impressive spread of HVDC extruded cables experienced worldwide in the last 25 years. The review considers development tests

pre-qualification tests

extension of qualification test

type tests (with hints at IEEE 1732-2017 for space charge measurements in the qualification of HVDC extruded cables)

routine tests (with hints at IEEE 2862-2020 for routine tests of HVDC extruded cable system joints)

sample tests and after installation tests. The review also analyses CIGRE TB 853 for lapped HVDC cable systems

as these cables remain unbeaten for submarine applications at the highest sea depths. The main novelties of CIGRE TB 852 and 853 with respect to previous standards for HVDC cable systems (mainly CIGRE TB 496 and IEC 62895 for extruded cables and CIGRE Electra 189:2000 for lapped cables) are put under the spotlight—with focus on the so-called temporary over-voltage tests—together with the limits and gaps of CIGRE TB 852. The main HVDC cable system testing equipment that is usually employed for electro-thermal tests is also treated. Emphasis is given to CIGRE TB 490 to treat the peculiarities of submarine cable systems

as well as to mechanical tests

having CIGRE TB 623 as a reference

with particular focus on the special sea trial tests. An example of an innovative sea trial testing procedure is shown

which is the outcome of a fruitful partnership between a cable manufacturer and the national Transmission System Operator in Italy.