变压器差动保护分析

一 概述 电力变压器是电力系统中十分重要的设备,如果出现故障将对供电可靠性和系统的正常运行带来严重的影响,特别是大型电力变压器,更是很贵重的设备.为了避免变压器事故的扩大,要求变压器内部发生故障时应迅速切断电源,使变压器退出运行.由于变压器的过流保护、速断保护还存在一定的死区,所以规定对于大容量变压器应装设电流差动保护. 变压器的纵联差动保护,是将变压器的一次侧和二次侧电流的数值和相位进行比较而构成保护装置,是变压器的主保护之一;变压器的差动保护主要用来保护变压器绕组南部及其引出线上的相间短路,同时也可以保护变压器单相匝间短路和接地短路.     

基于波形相似度的水电站电流饱和变压器保护装置设计

为解决传统水电站电流饱和变压器保护装置保护及时率低的问题,基于波形相似度设计水电站电流饱和变压器保护装置。计算水电站电流饱和变压器保护运维动态基线,补偿水电站电流饱和变压器保护功率因数,基于波形相似度,分析水电站电流饱和变压器保护信号,采用NBC叠片式弹片,设定水电站电流饱和变压器保护装置额定电压,实现水电站电流饱和变压器保护装置设计。设计实例分析,结果表明,设计的保护装置保护及时率明显高于对照组,能够解决传统保护装置保护及时率低的问题。     

浅析变压器压力释放保护

变压器压力释放保护,作为变压器的非电气量保护,其保护原理是当油箱内有故障的时候,油箱本体上压力释放阀的微动开关动作接通变压器跳闸回路来实现对变压器的保护。即当故障点发生在变压器内部时,变压器油被汽化,产生大量的气体,同时由于变压器油箱内油的体积急剧膨胀,使变压器油箱内部压力迅速上升。当变压器油箱内部压力升高到变压器压力释放阀设定的压力时,变压器压力释放阀微动开关迅速闭合,同时变压器压力释放阀在2毫秒内立即打开,使变压器油箱内的压力急剧下降。与此同时变压器压力释放阀微动开关迅速动作闭合,使变压器跳闸出口回路接通,跳开变压器各侧断路器。从而防止了变压器故障的进一步扩大。但在现场实际运行中,经常发生变压器压力释放保护误动作的事故。本文从现场运行实际出发,对变压器压力释放保护作出一定的比较分析,为现场运行提供指导。     

数字智能变电站变压器保护方案的探讨

十二五规划以来,智能电网越来越受到国家的重视,数字智能变电站作为智能电网的重要组成部分,赋予了传统变电站新的活力。从变压器保护的可靠性出发,首先对变电站变压器保护系统进行简单介绍。列出了匝间短路和漏感两种变压器故障,对其进行诊断分析。随后对变压器继电保护系统进行了探讨,讨论了数字智能变电站变压器的主保护、后备保护和现场调试,为今后变压器保护方案的确定提供了理论基础。     

变电站变压器差动保护运行故障及防范措施研究

本文主要针对变电站变压器差动保护情况进行分析,首先解析变电站变压器差动保护的原理以及差动保护对变电站的作用,指出当前变电站变压器差动保护运行故障问题,最终提出应对防范措施。     

浅析电力变压器差动保护不平衡电流产生原因及抑制方法

电力变压器微机保护通常由电流纵联差动保护与瓦斯保护作为主保护,其最关键也是最困难的问题是如何防止变压器不平衡电流所导致的差动保护误动作。但差动保护应用于变压器时,效果并不是很理想。     

变压器新差动保护技术研究

变压器保护主要有瓦斯保护和纵联差动保护,纵差动是变压器必须采用的保护原理。可以反映变压器的各种内部相间和接地故障。文章提出了一种不受空投时励磁涌流影响的新方法,用阻抗继电器反应空投于内部故障．这种保护配置方式在内部故障时有很高的灵敏度,在外部故障时又有很强的制动作用,不反映空投时的励磁涌流．却能反映变压器空载合闸时有故障的情况．解决了变压器差动保护的难题。     

基于小波变换的变压器保护装置的研究

简述了变鹾器保护的重要性,分析了电力变压器励磁涌流产生的原因,提出了基于小波变换的变压器保护方燕,并简单介绍了基于FPGA的小波变换IP核的实现方法。使用FPGA实现小波变换,可以据高变压器保护的实时处理速度和精度。该设计能大大提高变压器保护的精确性、灵敏性和可靠性。     

变压器差动保护的应用研究

变压器作为电力系统的重要组成部分,其安全性、稳定性直接关系着电力系统的正常运行,其故障的产生甚至是造成电力事故的出现,因此,必须注重变压器差动保护的研究和探讨。文章结合实际工作经验,在简要阐述变压器差动保护保护原理的基础上,对变压器差动保护应用相关问题进行分析,可为相关工作者提供参考。     

基于零序电流分布的自耦变压器电流保护分析

文中基于自耦变压器零序电流的分布特点,探讨了自耦变压器零序电流保护的构成及整定原则,重点分析了自耦变压器零序差动保护。     

Application of block pulse functions for digital protection ofpower transformers

The author describes an application of block pulse functions for digital protection of power transformers. Digital relay algorithms are developed to extract fundamental and second-harmonic components. These components are then used for harmonic restraint differential protection of transformers. In comparison with the algorithms based on the Walsh and Haar functions, the proposed method is computationally simple and can be used with any sampling frequency. It is concluded that offline testing of the method with simulated inrush and internal fault current data clearly indicate that the method can provide fast and reliable trip decision. The method is suitable for microprocessor-based protective relays     

考虑变压器励磁涌流影响的保护整定

在大型变压器空载冲击过程中,由于励磁涌流和负序电压的存在,如果定值整定不得当,会导致差动保护,复压过流保护等误动作,影响设备的正常运行。为了保证定值整定的正确性,在此通过对励磁涌流产生的原因和特点进行理论分析,结合变压器冲击过程中实际数据以及大型变压器冲击过程中由于定值整定不舍理造成保护误动作的实例,对变压器冲击过程中相关定值整定的原则进行了探讨。在定值的整定过程中要考虑励磁涌流的幅值、谐波含量和衰减时间以及负序电压的幅值和衰减时间的影响。     

不同制动判据差动保护的比率制动特性的测试方法

比率制动特性纵差保护作为电力系统中发电机、变压器等重要设备的主保护之一,其动作的可靠性对保证电力系统的安全运行至关重要,结合发电机纵差动保护和变压器纵差动保护的构成原理,提出了采用三路测试仪对两种常用的不同制动判据的纵差动保护比率制动特性的实用测试方法,实际应用表明该方法可靠、有效。     

Application of Walsh Functions for Microprocessor-Based Transformer Protection

The paper presents the application of Walsh functions for digital differential protection of power transformers. A digital differential relay impelementing the Walsh algorithm is simulated using a personal computer. The algorithm shows good response in terms of speed and accuray.     

从一起触电事故谈配电系统的安全措施

针对一起10 kV配电变压器高压侧避雷器爆炸引起的低压侧用户电击死亡事件,分析了触电事故的原因,提出了保证配电系统和人身安全的有效措施。     

A Cascade Multilevel Inverter Using a Single DC Source

1. INTRODUCTION A cascade multilevel inverter is a power electronic device built to synthesize a desired AC voltage from several levels of DC voltages. Such inverters have been the subject of research in the     

Direct-coupled gyrator suitable for integrated circuits and time variation

A direct-coupled gyrator circuit which can be easily realised in integrated-circuit form is described. Since the gyrator action extends to d.c., it is practicable to realise d.c. transformers by cascading two such gyrators.     

Bracing for the geomagnetic storms

As solar activity moves toward an 11 year peak, utility engineers are girding for the effects of massive magnetic disturbances. The nature of the geomagnetic disturbances is examined. The way in which geomagnetically induced current (GIC) affects power systems is explained. Virtually all power equipment, operation, and protection problems due to GIC are traceable to two direct effects: the half-cycle saturation of power transformers and the half-cycle saturation of the current transformers used with protective relay systems. Of the two, the former, with its numerous secondary effects, has been the more serious. As an example, a blackout due to solar disturbances, which happened to the Hydro-Quebec system in Mark 1989, is described. The factors that make power networks especially vulnerable today and the difficulty of predicting episodes are considered     

Cascaded H-bridge multilevel inverters with discrete variation of DC sources

This paper presents a new voltage regulation structure for multilevel inverters using discrete variation of DC sources. In the proposed method, discrete variation is achieved based on multi-tap transformers for applications where the DC sources are isolated and supplied by three-phase transformers, e.g., medium voltage (MV) motor drive applications. Moreover, by utilising the new solution, the number of required DC regulators is reduced significantly, for applications where the optimum modulation index with variable DC sources is used which suffer from large number of required converters. In addition, this paper proposes a new algorithm for optimising the switching angles, turn ratios of the multi-tap transformers and DC sources to maintain the voltage distortions at the standards levels for a wide range of output voltage regulation. To verify the feasibility of the new solution, a laboratory prototype is implemented based on a 2-cell cascaded H-bridge (CHB) multilevel inverter with unequal DC sources (with 9-level operation) while the proposed structure can be applied for other CHB multilevel inverters and switching strategies.     

New active input current shapers to allow AC-to-DC converters withasymmetrically driven transformers to comply with the IEC-1000-3-2

Four new topologies of active input current shapers (AICSs) for converters with symmetrically driven transformers (such as half-bridge, full-bridge and push-pull) have been proposed. This paper analyzes the extension of the use of these new AICSs topologies to converters with asymmetrically driven transformers. Using some of these topologies, the size of AICS inductors can be reduced and even integrated in a single magnetic core. As in the case of other converters with AICS circuit, the new topologies allow line current harmonics to be reduced and thereby to comply with the IEC 1000-3-2 specifications, whilst maintaining all the features of standard DC-to-DC converters (e.g., fast transient response). Finally, the proposed topologies have been experimentally tested