Characterisation of Soft Magnetic Materials for Metering Current Transformers and Other Low Flux Density Applications

用于计量电流互感器和其他低磁通密度应用的软磁材料的表征

• 批准号: EP/E006434/1
• 负责人: Anthony Moses
• 金额: $ 50.93万
• 依托单位: CARDIFF UNIVERSITY
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2007
• 资助国家: 英国
• 起止时间: 2007 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FE006434%2F1
• 关键词: Characterisation; Soft; Magnetic; Materials; Metering

The current transformer is a critical component in power measurement on electrical power supply systems. Its accuracy depends on the use of a magnetic core whose magnetic characterisitics are accurately known and do not vary with operating conditions.The core is normally made from grain oriented electrical steel strip which operates at a far lower flux density (B), and at the same time over a much wider range of magnitude, than in any other large scale application. The material is assessed and graded according to its high B performance but this is not directly related to performance in the low B regime. Furthermore, it is now realised that the permeability, the most important magnetic parameter for CT accuracy, varies widely at low B even in material of the same nominal grade; this itself will give rise to inconsistent CT performance.In operation, a fault current passing through the primary winding of a CT may cause a temporary or long term change in performance which is not detectable. This uncertainty can no longer be tolerated as accountablity for power flow and losses in distribution systems becomes more critical with the advent of more expensive fuel and distributed generation in particular.A related area of growing concern is effective passive shielding of equipment such as high field medical magnetic scanners (MRIs) where electrical steel is widely used. The shielding process usually means the material is mainly magnetised to a low B level as in CT cores so unknown B-H characteristics make device modelling or comparison of material performance very questionable.The aims of the project are (i) to develop a means of testing materials at low B to an accuracy not reached previously but now believed to be essential for evaluation of CT core and shielding materials, (ii) to develop a means of predicting the low B performance from studies of Barkhausen noise, domain wall motion and measured B-H curves, (iii) to study the effect of simulated power system disturbances on CT performance, (iv) to relate the accuacy of fully assembled CTs with variablity of core material and degradation of properties caused by the core manufacturing process and (v) to develop electromagnetic models to predict B-H characteristics in the low B regime.Uk steel, core and CT manufacturers will collaborate in the work where an important aspect will be to track material through the various stages from steel production, through core winding to the final assembly and evaluation of around fifty CTs.The main outcome of the research will be a new understanding of low full density performance of engineering magnetic materials which provide manufacturers with a more reliable and meaningful foundation for their designs which will lead to improved metering CTs and greater confidence of users in the accuacy of large scale electrical power measurement.

电流互感器Transformer是电力供应系统中功率测量的关键部件。它的精度取决于使用的磁芯，磁芯的磁特性是精确已知的，并且不随操作条件而变化。磁芯通常由晶粒取向电工钢带制成，其在远低于磁通密度（B）的情况下操作，同时在比任何其他大规模应用更宽的幅度范围内操作。根据材料的高B性能对材料进行评估和分级，但这与低B性能无直接关系。此外，现在认识到，即使在相同标称等级的材料中，磁导率（CT精度的最重要磁参数）在低B时也会有很大变化;这本身会导致CT性能不一致。在操作中，通过CT初级绕组的故障电流可能会导致无法检测到的暂时或长期性能变化。随着更昂贵的燃料和分布式发电的出现，配电系统中的功率流和损耗的可解释性变得更加关键，这种不确定性不再被容忍。一个日益受到关注的相关领域是设备的有效无源屏蔽，例如广泛使用电工钢的高场医用磁扫描仪（MRI）。屏蔽过程通常意味着材料主要被磁化到低B水平，如CT磁芯，因此未知的B-H特性使得设备建模或材料性能的比较非常可疑。该项目的目的是（i）开发一种在低B下测试材料的方法，其精度以前没有达到，但现在认为对CT磁芯和屏蔽材料的评估至关重要，（ii）根据对巴克豪森噪声、畴壁运动和测量的B-H曲线的研究，开发预测低B性能的方法，（iii）研究模拟电力系统扰动对CT性能的影响，（iv）将完全组装的CT的准确性与芯材的可变性和芯材制造过程引起的性能退化联系起来，以及（v）开发电磁模型，预测低B区的B-H特性。英国钢铁、核心和CT制造商将合作开展工作，其中一个重要方面是跟踪钢铁生产各个阶段的材料，通过磁芯缠绕到最终组装，并对大约50个CT进行评估。研究的主要成果将是对低全密度性能的新认识这些材料为制造商的设计提供了更可靠和更有意义的基础，这将导致改进计量CT和提高用户对大规模电力测量准确性的信心。