基于压力特征的变压器数字式非电量保护研究

In this project, in allusion to the defects of transformer's conventional mechanical non-electrical protection, principles as well as implementation technologies of transformer's digital non-electrical protection will be studied. Firstly the mechanism of the formation of both fault gas and pressure wave source in transformer tank will be studied, and then the mathematical models considering the pressure wave's spreading behavior coupled in gas, liquid and solid medium field will be built. Further the multi-physical direct coupling analysis software COMSOL Multiphsics will be utilized for the simulation and calculation of dynamic variation of pressure in transformer tank after the failure. In the meanwhile, transformer tank internal faults dynamic test platform will be established to verify the simulation results. The influence factors on pressure characteristics, such as the fault energy density, fault location, duration and transformer tank internal structure, etc. will be researched. Additionally, combined with the simulation data and dynamic test data, the pressure distribution and variation rule in transformer tank will be analyzed. According to the transient pressure amplitude, pressure variation tendency and steady pressure characteristics vary in different conditions such as internal/external faults and the abnormal/normal operation conditions, action in trip or in signal transformer non-electrical protection principle and comprehensive protection criterion will be put forward, protection setting calculation principle and method will be researched, and the simulation data and dynamic test data will be used to verify the correctness and effectiveness of this protection and its algorithms. According to the internal pressure distribution characteristics of each type of transformer tank internal faults, the number of pressure sensor and the optimization layout scheme of these pressure sensors installation position will be studied. Based on these above work, transformer non-electrical protection rely laboratory prototype on the basis of characteristics of tank internal pressure will be researched and developed.

本项目针对电力变压器机械式非电量保护动作可靠性不足的问题，研究数字式非电量保护原理及实现技术。分析变压器油箱内部故障气体及压力波震源产生的机理，建立压力波在气、液、固介质多场耦合传播的数学模型，在COMSOL Multiphysics环境下建立实际变压器几何模型及数学模型接口，计算分析变压器各类运行状态下油箱内部瞬时压力分布云图及变化规律；研究故障能量密度、故障点位置、故障持续时间等因素对压力特征的影响，依据油箱内外故障、非正常运行等状态下瞬时压力幅值、压力变化趋势、压力波振动频率等特征的差异，提出绕组匝间、匝地故障动作于跳闸及发热、局部放电故障动作于信号的变压器数字式非电量保护原理及保护判据，研究保护整定计算原则及方法；综合考虑压力分布特征、经济性、可实现性等因素，提出变压器压力传感器安装数量及位置的优化布置方案，开发基于压力特征的变压器数字式非电量保护实验室样机。

针对电力变压器机械式非电量保护动作可靠性不足的问题，项目依据油箱压力产生物理机理建立了内外部故障压力计算多场耦合模型，研究了变压器内、外部故障油箱内压力升高的瞬态物理过程及压力特征差异，提出了基于油箱压力变化特征的变压器非电量保护原理。主要研究工作及成果包括：.1）建立了变压器内部故障电弧能量模型、故障压力震源模型及油箱内部故障压力波传播模型，提出了油箱瞬态力学模型、声固耦合模型及其计算方法，仿真分析了变压器箱体在内部压力冲击下压力幅值、分布特征，得到故障能量、油压幅值以及油箱应力大小之间存在正相关性的结论；.2）研究了变压器外部短路故障过程中涉及的电路拓扑、瞬态漏磁场、结构力场、声流场之间的耦合关系，建立了以绕组振动为震源、绝缘油及固体构件为介质的压力波传播的多场耦合模型，在综合考虑计算复杂度与结果精度的前提下提出了多场耦合模型的计算方法，分析了外部短路冲击下油箱内不同位置的瞬态压力变化特征；.3）搭建了变压器外部故障油箱内部非电量测试实验平台，研究了压力、油流测量方法及传感器布置方案，通过外部故障试验获取了变压器油箱内部瞬态压力、油流变化数据，结合仿真数据分析了瓦斯继电器在外部短路冲击下误动的原因；.4）根据油箱内、外故障条件下油箱内部压力特征差异，提出了基于油压的变压器非电量保护原理，构建了采用压力幅值、压力变化量特征的非电量保护判据及整定方法，对比分析了多传感器与单传感器保护判据动作性能，提出了变压器数字式非电量保护构成方案，仿真、试验数据表明保护方案能够可靠、灵敏、快速切除变压器内部各类故障；.5）针对变压器内部故障压力冲击下发生油箱形变、破裂甚至引发爆炸、火灾的事故，研究了采取故障快速切除、油箱冲压结构设计、压力释放阀配置等变压器本体减压防爆措施，利用多场耦合模型分析了各项措施对油箱内部压力、箱体应力的瞬态变化的影响，验证了防爆减压措施的有效性。