Electrical treeing and tracking in polymeric interfaces in cable joints in DC networks

高压系统在现代世界中无处不在，现在是所有电力网络的一个组成部分。它们对可再生能源的传输和系统内连接至关重要。高压系统的使用现在在公共交通系统和大型电动汽车，特别是船舶和飞机上变得越来越普遍。高压直流线路也变得越来越重要，无论是对于理想的洲际网络，还是对于点对点的连接，例如一些已经达到+/-800千伏，延伸到中国各地。最近，英国政府宣布了一项计划，到2030年，30%的电力生产将来自海上风电场，这也将增加对高压直流海底电缆的依赖，并对其可靠性给予额外的重视。这里描述的项目支持高压直流连接及其可靠性的需求，因此有助于EPSRC的研究主题：能源网络，能源应用材料，基础设施和城市系统。高压聚合物电缆及其接头（接头和终端）失效的一个关键机制是电树生长。这种降解采取分叉的形式，类似于植物树的小管。这种树木在绝缘层上的生长会导致灾难性的故障，这在交流系统中已经得到了广泛的研究。然而，人们对直流系统中的树形系统知之甚少。特别是，很少有关于接口和关节中这些区域对树形/跟踪的脆弱性的工作。电能质量在直流老化中的重要性是公认的，但没有量化。同样，使用局部放电分析来理解交流树的生长过程也变得越来越容易理解，但对于直流树的生长却不是这样。这里提出的研究问题是，“在直流聚合物绝缘中，稳态电能质量对树木生长的作用是什么？”该项目将研究在控制电能质量的直流条件下树木的生长和初始化。这项工作将主要是实验性的，建立在高压电压实验室已有的专业知识基础上。这项工作的一个关键特点是，在实验室中使用的直流电压将比以前在这种情况下实现的更高。这是具有挑战性的，但将大大增加我们将实验室工作应用于实际应用的能力。特别是，将详细考虑接口上的树初始化。聚乙烯和硅胶系统将被研究。PD测量，包括光学和电学，将被用来理解放电在直流树生长过程中的作用。因此，将考虑使用PD作为资产管理工具。

High voltage systems are ubiquitous in the modern world and are now an integral part of all electricity power networks. They are critical in the transmission of renewable energy and intra-system connections. The use of high voltage systems is now becoming more prevalent in mass-transit systems and large electric vehicles, notably ships and aircraft. HV DC links are also becoming more important both for aspirational intercontinental networks, and for point-to-point links of which some have now reached +/-800 kV, stretching across China for example. Recently the UK government announced a plan for 30% of electricity production to come from offshore windfarms by 2030, which will also increase dependence on HVDC sub-sea cables and place additional importance on their reliability.The project described here underpins the need for HVDC connections and their reliability and so contributes to EPSRC's research themes of: Energy Networks, Materials for Energy Applications, and Infrastructure and Urban Systems.A key mechanism for failure of high voltage polymeric cables and their fittings (joints and terminations) is electrical tree growth. Such degradation takes the form of bifurcated, tubules which resemble botanical trees. The growth of such trees across the insulation leads to catastrophic failure and has been widely studied for AC systems. However much less is known concerning treeing in DC systems. In particular, there is little work concerning interfaces and the vulnerability to these areas in joints to treeing/tracking. The importance of power quality in DC ageing is well-established, but not quantified. Similarly the use of partial discharge analysis for understanding progression of AC tree growth is becoming better understood, but that is not the case for DC tree growth. The research question asked here then is, 'what is the role of steady state power quality on tree growth in DC polymeric insulation?'.This project will study tree growth and inception under DC conditions with controlled power quality. This work will be largely experimental building on the expertise already available in the HV voltage laboratory. A key feature of this work is that higher DC voltages will be used in the laboratory than has been achieved previously in this context. This is challenging, but will add substantially to our ability to take laboratory work and apply it to real applications. In particular, tree initiation at interfaces will be considered in detail. Polyethylene and silicone systems will be studied. PD measurements, both optical and electrical, will be used to understand the role of discharges in the progression of DC trees. Consequently, the use of PD as an asset management tool will be considered.