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首页> 外文期刊>Elektrotechnik und Informationstechnik >Short circuit verification for a 570 MVA, 420 kV single-phase GSU-transformer by SC-withstand tests on a mock-up unit
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Short circuit verification for a 570 MVA, 420 kV single-phase GSU-transformer by SC-withstand tests on a mock-up unit

机译：在模型单元上通过SC耐压测试对570 MVA，420 kV单相GSU变压器进行短路验证

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Large generator step-up transformers in power generation plants are exposed to several kinds of stresses under service conditions. One kind of stress is caused by forces at short circuits, which can even endanger and affect the entire reliability of a power plant. According to the international standards, there are three methods to demonstrate the ability to withstand the dynamic effects of a short circuit. The first one relies only on calculation and design checks with the manufacturer's design rules for short circuits. The second one observes the performance during a conventional full-scale short circuit test and the last one involves a design comparison to a similar reference transformer which has successfully passed a short circuit test. EDF and Siemens decided to evaluate the short circuit capability of a 570 MVA single-phase GSU-transformer by comparison to a similar reference mock-up transformer designed, manufactured and short circuit tested for this purpose. The reference transformer was designed to undergo equal or similar mechanical stresses as in the real full-scale unit during a short circuit. In this paper the most significant stress types in windings are analysed, described and evaluated. Similarity criteria and constraints regarding radial and axial winding stresses are discussed in detail. The short circuit tests on the mock-up transformer were performed in two test sequences. The first one was a successfully performed "customer acceptance test" where nominal short circuit currents and stresses were applied to demonstrate the short circuit stresses in the real unit. The second test series was a "destructive test". Currents shots were increased step by step until the unit experienced a notable change in the winding reactance. The purpose of the second test was to identify the critical mechanical stresses which caused permanent winding deformations and loss of stability on the mechanical structure. Results from a visual out-of tank active part inspection and some failure modes detected after winding dismantling are presented in this paper. Frequency Response Analysis (FRA) measurements performed before and after the short circuit test series show high correlations to detected mechanical movements. A not well-known failure mode of helical windings, the so called "spiralling effect", where compressive forces tighten up the winding turns towards the inner support, are analysed. Corrective measures to prevent such effects in transformer windings are suggested. The paper presents an experimental as well as a theoretical design evaluation and calculation approach to verify the short circuit withstand capability of large power transformers unable to be tested in high-power laboratories.
机译：发电厂中的大型发电机升压变压器在使用条件下会承受多种压力。一种应力是由短路力引起的，甚至会危害并影响发电厂的整体可靠性。根据国际标准，有三种方法可以证明承受短路动态影响的能力。第一个仅依赖于计算和设计检查以及制造商的短路设计规则。第二个在常规的满量程短路测试中观察性能，最后一个与成功通过短路测试的类似参考变压器进行设计比较。 EDF和西门子决定通过与为此目的设计，制造和短路测试的类似参考模型变压器进行比较，评估570 MVA单相GSU变压器的短路能力。参考变压器设计为在短路期间承受与实际满量程单元相同或相似的机械应力。在本文中，分析，描述和评估了绕组中最重要的应力类型。详细讨论了关于径向和轴向绕组应力的相似性标准和约束条件。对模型变压器的短路测试按两个测试顺序进行。第一个是成功执行的“客户验收测试”，其中应用了额定短路电流和应力来演示实际单元中的短路应力。第二个测试系列是“破坏性测试”。逐步增加电流冲击，直到单元的绕组电抗发生明显变化。第二项测试的目的是确定导致永久绕组变形和机械结构稳定性损失的临界机械应力。本文介绍了从外观上对油箱的活动部件进行检查的结果，以及在拆卸绕组后发现的某些故障模式。在短路测试系列之前和之后进行的频率响应分析（FRA）测量显示与检测到的机械运动高度相关。分析了螺旋绕组的一种不为人所知的失效模式，即所谓的“螺旋效应”，其中压缩力将绕组匝数朝着内部支撑件拉紧。建议采取纠正措施以防止在变压器绕组中产生此类影响。本文提出了一种实验以及理论设计评估和计算方法，以验证无法在大功率实验室中测试的大型电力变压器的短路耐受能力。

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