Contamination of the transformer oil of power transformers and shunting reactors by metal-containing colloidal particles

The results of a measurement of the contamination of the oil in 66 transformers by metal-containing colloidal particles, formed as a result of the interaction of the oil with the structural materials (the copper of the windings, the iron of the tank and core etc.), and also the results of measurements of the optical turbidity of the oil in 136 transformers when they were examined at the Power Engineering Research and Development Center Company are presented. Methods of determining the concentration of copper and iron in transformer oil are considered. The limiting values of the optical turbidity factors, the copper and iron content are determined. These can serve as a basis for taking decisions on whether to replace the silica gel of the filters for continuously purifying the oil of power transformers and the shunting reactors in addition to the standardized oil contamination factors, namely, the dielectric loss tangent and the acidity number of the oil.     

An estimate of the limit state of power transformers and autotransformers

The main indicators of the limit technical state of transformers and autotransformers, for which their further use is impermissible or inadvisable, are considered. The main elements of a power transformer which determine its limit state are the windings and the cores. Important indicators for estimating the technical state of the windings is the wear of the coil insulation, the degree of mechanical fastening of the windings and, in particular, the absence of dangerous deformations. Wear of the coil insulation is estimated from the degree of polymerization and the short-circuit resistance. The cores of the transformer become damaged fairly rapidly during operation. Normalized values of the above indicators are given as well as experience in using them in the Russian Federation and the Ukraine to estimate the limit state of transformers and autotransformers. The amount of inspection in order to reach conclusions on the technical state of a transformer and temporary measures until they are replaced are indicated. __________ Translated from élektricheskie Stantsii, No. 1, pp. 44–49, 2008.     

Interrelation of surface tension,optical turbidity,and color of operational transformer oils

Measurements of the acidity, optical turbidity, surface tension, and color of transformer oil from 54 power transformers, autotransformers, and shunt reactors are reported. Changes in surface tension, optical turbidity, and color are found to obey adequate linear correlations, while the acidity has no correlation with any of these properties. Numerical criteria for the maximum permissible state (quality) of the oil with respect to optical turbidity and color are obtained. Recommendations to operating staff are provided for cases in which the criteria for optical turbidity and color are exceeded.     

Use of Static Compensators for Voltage Control at 330- and 500-kV Substations

A scheme for compensating the reactive power and controlling the voltage of high-voltage, intermediate-voltage, and low-voltage buses of 330 – 500-kV substations, which consist of static thyristor compensators (STC) on low-voltage autotransformers and controlled shunting reactors on high-voltage lines, is presented. It is shown that the STC can be created step-by-step beginning with the reactive part on substations with low-loaded lines. Results of installation of reactor groups of STC stepwise-controlled by vacuum switches at 330- and 500-kV substations are presented. Tests of the reactor groups have proved their high efficiency.     

550 kV主变压器瓦斯继电器故障分析与参数优化

瓦斯保护是变压器的主保护之一,对变压器匝间和层间短路、铁芯故障、套管内部故障、绕组内部断线及绝缘劣化和油面下降等故障均能灵敏动作。以某电站550kV主变区外故障导致瓦斯动作事件为例,通过对事故原因的分析,提出在区外故障时应考虑瓦斯保护误动的可能性,并通过仿真计算,优化了瓦斯保护整定值参数。     

Transient Processes Accompanying Connection and Disconnection of Capacitive Filter-Compensating Devices

It is shown that the operation of connection of a filter-compensating device (FCD) to the buses of tertiary windings of a converter transformer in parallel to another (earlier connected) FCD is accompanied by a transient process that virtually does not influence the operation of the converter. On the contrary, the operation of disconnection of FCD (at another connected FCD) is accompanied by a transient process that affects the operation of the converter strongly and unfavorably due to disturbing the commutation of valves and often causes locking of the converter. This is a result of saturation of voltage transformers used for controlling the converter upon connection of FCD. The effect can be eliminated by replacing 3NOM-type voltage transformers by NOM-type transformers for controlling the converter or by ungrounding at least one FCD. In addition to improving the operation of the converter these measures prevent a dangerous increase in the currents of primary windings of voltage transformers. Their efficiency has been confirmed by digital simulation and field tests of the back-to-back link between power systems of Russia and Finland.     

Improving the Reliability of Operation of Power Transformers

The special features of and experience in the operation of power unit transformers and autotransformers are described. The requirements on some parameters of power transformers are considered. An analysis of the rate of failure of power transformers used at thermal and hydraulic power plants is made for determining the components with unsatisfactory reliability and setting specific requirements on the electrical industry.     

一起主变压器压力释放阀喷油原因分析及处理

介绍了水布垭电厂压力释放阀动作的原因、开关断开后的处理经过、随油温变化变压器的体积计算及油位计校验方法,提出了主变压器出现非电气故障时的防范措施。     

Reliability of power transformers and autotransformers of electric networks

The failure rate and experience of operation of power network transformers and autotransformers are analyzed. After analysis of the failure rate assemblies with elevated vulnerability to damage are determined and engineering solutions employed by the electrical industry for raising their reliability are described. __________ Translated from élektricheskie Stantsii, No. 11, November 2005, pp. 69–78.     

干式变压器在泵站中的应用

介绍了干式变压器的功能特点,总结了干式变压器在梧州防洪堤泵站中实际应用的经验,通过比较干式变压器和油浸式变压器的性能优缺点,指出了干式变压器在泵站运行管理中应注意的一些问题.     

一种水电站主变压器电能损耗计算方法

从水电站机组出力持续曲线角度进行变压器的电能损耗计算,精确计算了不同出力下变压器的铜损、铁损的比例及其影响,通过数学建模得出基于发电机出力持续曲线的变压器运行电能损耗方程。以广东惠州东江水利枢纽水电站工程为例,验证了该方法的适用性准确性,为水电站变压器电能损耗计算提供一种新的方法,供相关人员参考。     

变压器经济运行方式的分析

变压器损耗在电力系统损耗中占有相当比例,严重时甚至超过系统损耗的1/2,导致大量电能浪费。针对现状,提出了调整变压器运行方式的方案来减少损耗。根据变压器的损耗特性,分析了变压器负载率、容量等因素对变压器损耗大小的影响,提出了变压器经济容量的选择方法。     

油纸电容式电流互感器绝缘整体受潮的处理

2001年6月,高坝洲电厂220kV开关站4台油纸电容式电流互感器(CT)介损普遍迅速升高,通过预防性试验,查明其原因是CT本体绝缘整体受潮。针对该重大缺陷,采取了吊芯烘干的方法处理。     

Operation of Line Transformers Upon Attainment of Maximum Permissible Parameters of Wear of Winding Insulation

Possible mechanisms of failure of insulation of windings of line transformers after exhaustion of their service life are considered. Conditions of strength of paper insulation and conditions of operation of screw-type insulation under the action of short-circuit currents are analyzed. Recommendations are formulated for the use of line transformers with exhausted insulation life.     

蒲石河抽水蓄能电站500kV主变压器检修工艺及措施

蒲石河抽水蓄能电站500 k V主变压器在安装过程中,由于业主提供的真空滤油机存在设备制造质量问题,导致主变器在充油过程中绝缘油品指标不合格,铁芯内部受到污染,经业主要求需将主变分解拆除进行返厂检修处理。由于洞室施工空间狭小,施工方式受限制,并且主压器的分解拆除工作属于保护性拆除,变压器拆除工艺的好坏直接关系到主变压器的再次使用效果及施工质量,所以施工难度和工艺的复杂程度大大提高。     

清江流域电厂主变大修及工艺改进

介绍了清江流域电厂主变压器大修主要内容,包括高压套管及密封更换、变压器油含气量超标处理、变压器油介损超标处理、夹件放电处理,还介绍了真空注油工艺改进及一些大修中的实用技巧。     

电流互感器配置与选择的几个问题

从对电流互感器的技术要求出发，对各种保护用电流互感器的特点进行分析，提出保护用电流互感器的选择原则，额定一次电流、额定二次电流选择存在的问题和解决的方法，以及如何合理配置电流互感器，以避免出现保护的死区。     

Tuning of higher harmonic filters connected to the tertiary windings of converter transformers

The features of the tuning of filters, connected with the tertiary windings of converter transformers, is considered. It is shown that such a connection is effective, but encounters difficulties due to the fact that the tunable filters have impedances as low as the external circuits. A theory and practical methods are given on how to overcome these difficulties. Positive results, obtained when tuning the filters in the Vyborg dc installation are described. __________ Translated from élektricheskie Stantsii, No. 2, pp. 63–66, 2008.     

840 MV·A主变压器磁屏蔽故障分析及处理

某水电站1台840 MV·A主变压器在运行期间例行油色谱分析发现乙炔含量上升,影响主设备安全稳定运行。检修人员查找出故障点在上夹件磁屏蔽,并对结构进行分析,明确了故障原因是设计上的结构缺陷,提出了相应的改进设计,对该型所有主变压器的磁屏蔽进行了更换,防止了该家族性缺陷产生的安全风险。     

Regeneration of Cellulose Insulation of Windings of Long-Life Power Transformers

Main aspects of the physicochemical condition of cellulose insulation of windings of power transformers with a long-term service life are analyzed with the aim of determining criteria on the possibility of prolonging the life of the insulation by washing with surface-active substances.