中性点小直流对低噪声变压器噪声影响探究

发布时间：2019-02-25 11:08

【摘要】：直流偏磁作为电力变压器运行时一个特殊工况,会造成电力变压器出现一系列问题,还会对电力系统产生一定影响。其中,变压器运行噪声的变化是最容易被识别和发现的。近几年,低噪声变压器由于其运行噪声低,对周围居民正常生活环境影响小,以及对变电站选址制约小,特别适合城市繁华地区使用等原因,越来越受到市场欢迎。随着大量低噪声变压器的投运,直流入侵对低噪声变压器的影响也越来越受到关注。本文以国内某220kV变电站两台同型降压低噪声环保变压器在运行时,出现了其中一台中性点接地的变压器噪声突然变大,若断开此接地点,另一台中性点接地,则接地的变压器噪声同样变大这一案例作为分析对象,从现场噪声试验数据和频谱特征入手,比对变压器制造厂原始出厂测试数据,并结合变电站多种运行工况下的测试数据,分析发现了这两台的变压器中性点有微小的直流电流输入。论文论证了这两台变压器中性点出现微小直流的可能性,并分析了直流电流的可能来源。首先,本文在论述变压器的多种铁心结构形式、空载性能理论依据和工程计算过程的基础上,分析了铁心材质的各项性能和选取关键,从工程制造各个环节论述了造成变压器噪声等空载性能异常的可能性,并对该变压器生产制造过程中的材料、结构和工艺等进行了分析,确认了该变压器的低噪声性能指标。接下来,从变压器铁心材料的物理性能和选用,以及变压器设计方案中铁心设计参数选取等方面探究了中性点输入微小直流造成低噪声环保电力变压器噪声异常的可能性,并假设不同的设计参数和材料选取情况下,计算出不同性能的变压器在同样工况下噪声的变化量,进一步确认了设计磁通密度较低,材料选用优良的变压器,对直流的敏感度更高。最后,列举了直流侵入对变压器和电网的其他危害,对该变压器的运行维护按照是否消除故障分成两个阶段提出了建议。第一,直流短期存在期间,变压器继续挂运行的维护和检修措施;第二,消除直流源或采取隔离措施之后一年时间内变压器的监测、维护和检修措施。依据此运行案例,本文还对变压器在工厂制造期间如何实现低噪声,从参数选型、材料选取、设计结构、工艺控制等提出了建议。
[Abstract]:As a special condition of power transformer, DC bias magnetic field will cause a series of problems in power transformer, and will also have a certain impact on power system. Among them, the change of transformer operating noise is the most easily recognized and detected. In recent years, the low noise transformer has been more and more popular in the market because of its low operating noise, little influence on the normal living environment of the surrounding residents, and little restriction on the location of the substation, especially suitable for the use in the bustling urban areas. With the operation of a large number of low-noise transformers, the influence of DC intrusion on low-noise transformers has been paid more and more attention. In this paper, during the operation of two homotypic low-noise and low-voltage environmental protection transformers in a domestic 220kV substation, the noise of one of the transformers with neutral grounding suddenly increases. If the connection is disconnected, the other will be grounded. Based on the noise test data and spectrum characteristics, the original test data of transformer factory are compared, and the test data under various operating conditions of substation are combined with the test data. It is found that the neutral point of the two transformers has small DC current input. In this paper, the possibility of micro DC in neutral point of the two transformers is demonstrated, and the possible source of DC current is analyzed. First of all, on the basis of discussing various types of core structure of transformer, theoretical basis of no-load performance and engineering calculation process, this paper analyzes the performance and selection key of core material. The possibility of abnormal no-load performance such as transformer noise is discussed from various aspects of engineering manufacturing. The materials, structure and process in the manufacturing process of the transformer are analyzed, and the low noise performance index of the transformer is confirmed. Then, from the aspects of the physical properties and selection of transformer core materials, and the selection of core design parameters in the transformer design scheme, the possibility of low noise environmental protection transformer noise anomaly caused by small DC input of neutral point is explored. On the assumption of different design parameters and material selection, the variation of noise of transformer with different performance under the same working condition is calculated. It is further confirmed that the design flux density is lower and the material is excellent. The sensitivity to DC is higher. Finally, the other hazards of DC intrusion to transformer and power network are listed, and the operation and maintenance of the transformer is divided into two stages according to whether the fault is eliminated or not. First, the maintenance and repair measures for the transformer to continue to operate during the short period of DC existence; second, the monitoring, maintenance and repair measures for the transformer within one year after the elimination of the DC source or the adoption of isolation measures. According to the operation case, this paper also puts forward some suggestions on how to realize low noise during the manufacturing period of the transformer, including parameter selection, material selection, design structure, process control, etc.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM41

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