摘要
多次短路会逐渐积累绕组机械损伤,最终导致电力变压器损坏。然而,目前缺乏一种量化评估方法来评估此类损伤,这对电网的安全运行构成了威胁。因此,该文提出一种考虑绕组的非线性特点和累积过程的电力变压器绕组短路累积机械损伤评价方法,为评估绕组短路对电力变压器的影响提供了新的途径。该方法采用阻尼比和可靠性损失系数作为特征量,通过指数型曲线来模拟绕组机械弱化过程。同时考虑变压器的初始承受短路的能力、短路电流幅值和故障次数等影响因素,量化了短路损伤与绕组动态机械寿命之间的关系。此外,通过对一台110 kV电力变压器进行多次短路破坏性试验,验证了该评价方法的正确性。最后,阐述了提出的评价方法适用于不同的校核控制方法,并强调了控制阻尼比在减少累积损伤方面的积极作用。
Multiple short circuits can gradually accumulate mechanical damage to the windings,leading to the failure of power transformers.However,a quantitative assessment method is lacking to evaluate such damage,and grasping the mechanical state of the transformer winding after a short-circuit impact is challenging.The cumulative damage of windings caused by multiple short circuits is still an urgent problem in the industry,which poses a threat to the secure operation of power grids.Therefore,this paper proposes an evaluation method for assessing the accumulated mechanical damage caused by short circuits in power transformer windings,considering the nonlinear characteristics of windings and the cumulative process.Firstly,the method utilizes the damping ratio and reliability loss coefficient as features.Exponential curves are used to simulate the mechanical weakening process of windings.Additionally,the initial short-circuit withstanding capability,short-circuit current magnitude,and the number of faults are considered.The influence of a short circuit on the mechanical performance of the winding is theoretically analyzed,the number of times that it can withstand a current impact is calculated,and the residual mechanical life coefficient is predicted.The correctness of this evaluation method is validated through destructive short-circuit tests on a 50 MVA/110 kV power transformer.This three-phase,three-winding,differential-designed transformer provides six sets of short-circuit test data.The end of the test is determined by gradually increasing the loading current and the relative change rate of the impedance.122 short circuit tests are implemented,ranging from 8 times to a maximum of 33 times.All the windings are disassembled after short-circuit tests.Several significant deformations are observed,consistent with predicted failure forms.Moreover,no secondary insulation breakdown or internal short circuit faults caused by mechanical damage are reported.Taking multiple short circuit tests as an example,the dynamic curve of winding mechanical life is obtained,and the dynamic ability of transformer winding to withstand short circuits in operation is characterized.By analyzing critical parameters of the evaluation method,it is found that the influence deviation of different checking systems on cumulative effect evaluation results is less than 1%,and the influence of the damping ratio on the cumulative effect is more than 10%.Therefore,this method is suitable for different checking algorithms.Process control and auxiliary strengthening measures can enhance the withstanding ability for short circuits and reduce cumulative damage or winding destruction.In a word,the method provides a quantitative calculation method for evaluating short-circuit cumulative mechanical damage.Moreover,this method can better describe the winding mechanical state after short circuits,which can provide a reference to transformer design,operation,and maintenance.
作者
欧强
罗隆福
李勇
杨贤
周腊吾
Ou Qiang;Luo Longfu;Li Yong;Yang Xian;Zhou Lawu(College of Information Engineering Southwest University of Science and Technology,Mianyang 621010 China;College of Electrical and Information Engineering Hunan University,Changsha 410082 China;Electric Power Research Institute Guangdong Power Grid Co.Ltd ,Guangzhou 510080 China;College of Electrical and Information Engineering Changsha University of Science and Technology,Changsha 410114 China)
出处
《电工技术学报》
EI
CSCD
北大核心
2024年第8期2578-2590,共13页
Transactions of China Electrotechnical Society
基金
国家自然科学基金项目(52061130217)
中国南方电网有限责任公司研究开发项目(036100KK52200045)资助。
关键词
电力变压器
短路
累积损伤
可靠性
评价
Power transformer
short circuit
cumulative damage
reliability
evaluation
