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

世界范围内发电和输电系统的变化导致了新的高压输电系统的安装，而交流输电技术将基于直流输电。高压直流输电系统中固体聚合物绝缘材料的使用越来越多，这就提出了一个问题，即高压直流输电元件的可靠性和耐久性是否至少与交流系统一样好。与交流输电系统相比，高压直流输电系统中长期使用固体聚合物绝缘材料的经验较少。高压元件的使用寿命主要由其绝缘决定。对于交流电压应力，已经发展了一种方法，用它可以确定固体绝缘材料的使用寿命作为电场强度的函数。这种方法目前还不适用于直流电压应用，这使得几乎不可能估计绝缘系统的寿命。其中一个原因是在直流电压作用下绝缘系统中会形成空间电荷，这对绝缘的寿命有很大的影响。因此，应该开展一项研究项目，以开发一种新的方法来加速确定聚合物绝缘材料的寿命，作为直流电压应力和绝缘材料中空间电荷形成的函数。为此，典型的聚合物绝缘材料将在直流和交流电压下老化到失效，因此将使用空间电荷测量技术来研究直流电压。为了能够同时研究几种聚合物绝缘材料，将使用两种不同的方法来检测和定位绝缘内部的空间电荷，每种方法适用于不同硬度的材料。这项在两个独立研究所进行的平行调查，每个研究所使用一种空间电荷测量方法，将能够比较不同绝缘材料的性能以及不同测量方法的适用性和重复性。此外，由于更广泛的测试结果，该程序允许在增加统计安全性的情况下进行评估，特别是在可以验证相应其他研究所的结果的情况下，因为将在两个实验室调查不同和相似的绝缘材料和测试序列。因此，可以更精确和可持续地发展假设和方法，从而最终还将对不同电压应力的研究进行相互比较，以检验直流电压下的使用寿命是否可以与交流电压的使用寿命近似。

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.