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Insulation degradation, assessment of loss-of-life and optimization of transformer utilization in power distribution system.

机译：配电系统中的绝缘退化，寿命损失评估和变压器利用率的优化。

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摘要

Although the incentive to load power transformers beyond their nameplate rating has always existed in the past, more recently utilities show more enthusiasm to fully utilize them to achieve greater profit in today's competitive electric energy market. One of the basic criterion, which limits the transformer loading capabilities, is the hottest-spot temperature of windings and the corresponding loss-of-life and the possibility of insulation failure. Transformer full load output limit is determined primarily by winding hottest-spot temperature. According to the IEEE Std. 057.91-1995, for the thermally upgraded paper as used today, it is limited to 110°C @ 30°C ambient temperature for a 65°C average winding temperature rise unit. Higher winding hottest-spot temperature causes degradation of the winding insulation. High temperatures decrease the mechanical strength and increase brittleness of fibrous insulation, increasing the potential of transformer failure. Gas bubbles may also form at elevated operating temperature, which may also cause the dielectric breakdown of transformer oil.; Under certain operating conditions, a transformer may be safely loaded beyond its nameplate rating. For every 1°C ambient temperature reduction (from standard 30°C) releases approximately 1% of overloading capability. The cold winter weather allows transformers to run at lower hottest-spot temperature, allowing for some overloading or saving of the insulation life. While in the summer, transformers run at higher ambient temperatures and possibly at higher than the rated hottest-spot temperature. The insulation degrades rapidly under these high temperatures and transformer life could be shortened substantially.; Utilities usually size and operate their transformers by matching the rating with the present demand and taking into consideration the future growth. Industry standard suggests transformer life expectancy to be between 20–30 years under “normal” operating conditions. In order to defer transformer replacement cost or cost of adding a second transformer under certain conditions, utilities may overload the transformer much beyond the nameplate rating and accept reduced life. The proposed research will address this very issue of economic decision based on the transformer remaining life-expectancy model and the future load growth. The probability tree structure is utilized to describe the future load growth pattern. The uncertainty of future load has been taken into account by this model. Together with probability tree model, the transformer thermal model has been employed to calculate service life of the transformer and determine when to replace an existing transformer with the new unit. The primary objective of this dissertation is to develop an optimization method to minimize the cost and select the proper transformer size for new applications and to optimize the replacement of transformer for an existing system and retrofit design. It is anticipated that the proposed method and the written computer program will help utilities in making decisions to minimize revenue requirements of the transformer over the long run to attain overall economic efficiency.
机译：尽管过去一直存在将功率变压器负载超过其铭牌额定值的诱因，但最近，公用事业公司表现出了更多的热情，可以充分利用它们来在当今竞争激烈的电能市场中获得更大的利润。限制变压器负载能力的基本标准之一是绕组的最热点温度以及相应的寿命损失和绝缘故障的可能性。变压器的满载输出极限主要由绕组最热点温度决定。根据IEEE标准。 057.91-1995，对于今天使用的热升级纸，对于平均卷绕温度上升单元为65°C，在30°C环境温度下限制为110°C。较高的绕组热点温度会导致绕组绝缘性能下降。高温会降低机械强度并增加纤维绝缘的脆性，从而增加变压器故障的可能性。在升高的工作温度下也可能形成气泡，这也可能导致变压器油的绝缘击穿。在某些运行条件下，变压器的安全负载可能超过其铭牌上的额定值。环境温度每降低1°C（从标准30°C降低），就会释放大约1％的过载能力。寒冷的冬季天气使变压器可以在较低的最热点温度下运行，从而导致某些过载或缩短绝缘寿命。在夏季，变压器在较高的环境温度下运行，并且可能会高于额定的最高热点温度。在这些高温下，绝缘层迅速退化，变压器寿命可能大大缩短。公用事业公司通常通过使额定功率与当前需求相匹配并考虑未来的增长来确定其变压器的大小和运行。行业标准建议在“正常”工作条件下，变压器的预期寿命为20–30年。为了降低变压器的更换成本或在某些条件下增加第二台变压器的成本，公用事业公司可能会使变压器超载，超出铭牌上的额定值，并缩短使用寿命。拟议的研究将基于变压器剩余寿命模型和未来负载增长来解决经济决策问题。概率树结构用于描述未来的负载增长模式。该模型考虑了未来负荷的不确定性。与概率树模型一起，已使用变压器热模型来计算变压器的使用寿命，并确定何时用新机组更换现有变压器。本文的主要目的是开发一种优化方法，以最小化成本并为新应用选择合适的变压器尺寸，并为现有系统和改造设计优化变压器的更换。可以预期，所提出的方法和书面的计算机程序将有助于公用事业部门做出决策，以从长远来看将变压器的收入需求降至最低，从而实现总体经济效益。

著录项

  • 作者

    Pansuwan, Sarunpong.;

  • 作者单位

    University of Colorado at Boulder.;

  • 授予单位 University of Colorado at Boulder.;
  • 学科 Engineering Electronics and Electrical.
  • 学位 Ph.D.
  • 年度 2001
  • 页码 209 p.
  • 总页数 209
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 无线电电子学、电信技术;
  • 关键词

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