Evaluation of the voltage endurance curve for polymeric insulating materials under stress with high direct voltages (HVDC)

• Applicants: Professor Dr. Stefan Kornhuber; Professor Dr.-Ing. Peter Werle
• Subject Area: Electrical Energy Systems, Power Management, Power Electronics, Electrical Machines and Drives
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 464489575

Worldwide changes in the electrical power generation and transmission systems lead to the installation of new high-voltage transmission systems, which in contrast to the AC technology will be based on DC transmission.Increasing usage of solid polymeric insulating materials in high-voltage direct-current (HVDC) transmission systems raise the question whether the reliability and durability of HVDC transmission components is at least as good as that of AC systems. Long-term experience with solid polymeric insulating materials in high-voltage direct current (HVDC) transmission systems are low compared to that of alternating current systems.The service life of a high-voltage component is mainly determined by its insulation. For AC voltage stresses, methods have been developed with which the service life of solid insulating materials can be determined as a function of the electric field strength. Such a method is currently not available for DC voltage applications, which makes it almost impossible to estimate the lifetime of the insulation system. One reason for this is the formation of space charges in the insulation system under DC voltage, which significantly influence the lifetime of the insulation. Therefore a research project should be carried out with the aim of developing a new method for the accelerated determination of the lifetime of polymeric insulating materials as a function of the DC voltage stress and the formation of space charges in the insulating material.For this purpose, typical polymeric insulating materials are to be aged to failure under DC and AC voltage, whereby space charge measurement techniques will be used for the DC voltage investigations.In order to be able to investigate several polymeric insulating materials simultaneously, two different methods will be used, each adapted to materials of different hardness degrees, for detecting and localizing space charges inside the insulation. This parallel investigations in two independent institutes, each using one space charge measurement method, will enable a comparison of the behaviour of different insulating materials and the suitability and reproducibility of different measurement methods. Moreover, due to the more extensive test results, this procedure allows an evaluation with an increased statistic safety, especially as the results of the respective other institute can be verified, since both different and similar insulating materials and test sequences will be investigated in both labs. Thus hypotheses and methods can be developed more precisely and sustainably, whereby the investigations with the different voltage stresses will ultimately also be compared with each other, in order to check whether the service life under DC voltage can be approximated from the AC voltage service life span.

• DFG Programme: Research Grants