Superimposed impulse voltage testing on extruded DC-cables according to IEC CDV 62895

Summary

As HVDC applications rise in the area of energy supply, there is a need for an appropriate HVDC testing of power transmission cables with extruded insulation and their accessories (new IEC CDV 62895 Ed. 1.0 “High Voltage Direct Current (HVDC) power transmission cables with extruded insulation and their accessories for rated voltages up to 320 kV for land application – Test methods and requirements”). The type and prequali-fication tests on HVDC cable systems include the superimposed impulse voltage test, during which several switching and lightning impulses are applied on the HVDC cable which has been energized for multiple hours by a DC voltage. The DC voltage shall be maintained during the application of the impulse voltage. This test condition poses a technical challenge to the test setup, since the DC source and the impulse voltage gener-ator have to be protected from each other. Neither must the DC voltage be present at the impulse voltage generator nor must the impulse voltage have any influence on the DC voltage generator. The superimposed impulse voltage test on HVDC cables is a compo-site test according to IEC 60060-1 Ed. 3.0 which requires suitable coupling and protection elements in combination with suitable converting devices and recording instruments. For the impulse side, the coupling and protection is possible with either a spark gap or a ca-pacitor. For the DC side, the coupling and protection is realized by a damping resistor. The pros and cons as well as the design aspects of the coupling and protection devices are introduced. A possible smart solution for the capacitive coupling by using spare ca-pacitor stages of the impulse voltage generator is discussed. Additionally the revision of IEC CD 60230 Ed. 2.0 “Impulse tests on cables and their accessories” is commented with respect to the proposed test setups and the measuring system for the superimposed im-pulse voltage test.

Additional informations

Authors

JI

Keywords

Superimposed Impulse Voltage Test, HVDC Cables with extruded insulation, IEC 62895, High Voltage Testing