微机控制同步电动机失步保护技术及装置的探讨

针对工矿企业里同步电动机在运行过程中，由于外界故障因素，非电动机本身原因所引起的同步电动机失步事故，一般分带励失步和失励失步两种，并分析了产生失步的原因。本文研制的微机控制的同步电动机失步保护技术及装置具有选择性、灵敏性、速动性和可靠性。其原理是以转子励磁回路中出现交变电流为判据，设置起动闭锁环节和同步振荡记忆闭锁环节。当同步电动机发生同步振荡时，失步保护装置应能迅速识别，并进行记忆闭锁；当失步运行时，失步保护装置应能灵敏、迅速可靠地动作。     

同步电动机转子失磁故障的影响分析

对同步电动机转子失磁状态进行了仿真分析,判断出同步电动机在失磁状态下容易引起间接事故。得出同步电动机失磁状态下定子电流和转速的变化情况,通过监测定子电流、转速和振动可以及时的发现失磁故障并尽快停机,避免间接事故造成的损失。     

同步电动机失步及其保护的研究

本文分析了同步电动机失步时的行为特征和国内外几种失步保护的优缺点，在此基础上提出了以检测同步电动机功率因数角及静稳边界曲线为基础的失步保护方案。     

WDH-825A微机同步电动机保护装置

介绍了最新研制成功的微机型同步电动机保护装置,该装置针对市场对同步电动机保护产品灵敏度高、动作可靠的迫切需求开发出来,在大量现场数据的基础上通过缜密的理论分析形成本装置独具特色的断电、失磁、失步三大保护判据.本保护装置采用了高可靠的硬件平台以及VLD开发技术,具有完善的保护功能的同时还具有一定的测控功能,不仅适用于同步电动机保护还适用于异步电动机保护,是一款具有高品质、高性价比的保护测控一体化装置.     

高压永磁同步电动机转子不同结构的起动性能分析

高压永磁自起动同步电动机从起动到牵入同步过程是一个复杂的机电瞬变过程.在电动机设计过程中,如何使电动机的起动性能、牵入性能以及稳态运行的过载性能达到协调统一是个不容忽视的问题.基于永磁电动机转子结构的改进,本文对高压永磁同步电动机的起动过程进行了数字仿真,研究了动态起动过程,研究了直轴同步电抗、交轴同步电抗以及两种同步电抗的比值对起动转矩、牵入转矩以及失步转矩的影响,并在分析过程中结合所得结论对一台315kW、6kV高压永磁自起动同步电动机及其改进结构进行了研究论证.仿真及试验结果表明,转子结构改进后的高压永磁同步电动机在起动过程中的几种性能上各有所长,互有得失,所得这些结论对推动高压永磁自起动同步电动机的实际运用具有指导意义.     

直流电动机中的箝位效应——兼论无刷直流电动机之实质

无刷直流电动机的出现,使得直流电动机与同步电动机的区别变得模糊了.直流电动机和同步电动机的关键,在于电枢磁动势与直流励磁的磁极之间存在着不同的特定关系.直流电动机中电枢磁动势的轴线位置是由电刷位置决定的,电刷具有箝位的功能.发生在直流电动机内的自控变频作用也是箝位效应的直接结果,直流电动机的优良控制性能与箝位效应的存在密切相关.同步电动机只有接至恒频电源才能稳定运转,同步电动机的特征是功角容易变动,在运行中经常出现转子失步,这与它不存在箝位效应有关.无刷直流电动机中的位置传感器代替了电刷的箝位功能,使得其电机本体内同样存在着箝位效应,它完全没有同步电动机的性能行为.     

同步电动机失步保护

本文阐述了同步电动机失步时的危害性、同步电动机同步和失步运行时的测量阻抗轨迹、CYR1D—BT1继电器阻抗特性分析、同步机失步模拟试验及失步保护整定原则。较详细地分析同步电动机同步和失步运行状态时的各种测量阻抗轨迹,分析结果和模拟试验十分接近;同时,CYR1D—BT1继电器阻抗特性分析结果,阻抗特性圆能和该理论相吻合。所以该理论是可行的,可作为失步保护继电器制造及失步保护整定的理论根据。     

同步电动机断电失步保护设计

同步电动机的保护设置有许多,如电流速断保护,差动保护,过载保护,单相接地保护,带励、失励失步保护等,而在工矿企业中由于断电而造成电动机失步的故障非常普遍。为了保证电动机安全,确保一些重要负荷连续运行,因此在同步电动机保护设计中,应该重视其断电失步保护的设置。     

WDH-825A微机同步电动机保护装置

介绍了最新研制成功的微机型同步电动机保护装置,该装置针对市场对同步电动机保护产品灵敏度高、动作可靠的迫切需求开发出来,在大量现场数据的基础上通过缜密的理论分析形成本装置独具特色的断电、失磁、失步三大保护判据。本保护装置采用了高可靠的硬件平台以及VLD开发技术,具有完善的保护功能的同时还具有一定的测控功能,不仅适用于同步电动机保护还适用于异步电动机保护,是一款具有高品质、高性价比的保护测控一体化装置。     

基于失电残余电压的永磁同步电动机失磁故障诊断研究

对利用失电残压诊断永磁同步电动机转子失磁故障进行研究。首先,对电机失电后定子绕组残余电压进行分析,讨论了定子失电残余电压的产生、性质;其次,分析了失磁故障对失电残余电压的影响,提出了利用失电残余电压诊断失磁故障的判别依据;最后,通过实验研究验证了该判据的正确性与有效性,表明基于失电残余电压诊断永磁同步电动机失磁故障方法的可行性。     

Protecting a High Horsepower Motor

Protecting the motor is obviously the most important task of protection relays regardless of the technology that they are based on. Microprocessor-based relays are capable of processing the measured data (i.e., current, voltage, and status indication) in many different ways. Registered data in the relay can be sent through a communication network to the operation/engineering headquarters for continuous monitoring or fault analysis. In addition to being used for motor protection, relays provide useful information to other departments (maintenance, planning, etc.).     

Improving existing motor protection for medium voltage motors

Motor failures and associated present-day costs are analyzed, and potential troubles generated within the plant and form the utility distribution system are documented. These troubles, their effects, and resultant motor failure modes are illustrated to determine the maximum protection desired for prolonged motor life. Limitations of older forms of motor protection utilizing induction-type overcurrent relays are presented in contrast with the desired protection. The features of several different types of current microprocessor-based relays are reviewed as eligible candidates for motor protection upgrading. An example of work performed as part of a comprehensive field retrofit is presented along with economic considerations     

快速后备保护研究

电力系统继电保护中后备保护按阶梯形配置整定，必然带来主干电网和发电厂后备保护动作时间太长、影响电网安全的问题。提出建立一种新的快速后备保护系统的思想，描述了变电站快速后备保护系统的结构和运行原理，建立了动作逻辑方程式。采用文中所述方法，变电站后备保护动作时间将小于1s，从而可大大缩短整个电网的后备保护动作时间。     

Trade-Offs in Overload Protection for Low Voltage Motors

Running overcurrent protection for motors rated 600 V or less is available in a variety of devices. Thermal overload relays, thermal protectors, magnetic and solid-state overload relays, multifunction solid-state motor protectors, and even short-circuit protective devices selected according to certain rules of the National Electrical Code (NEC) can provide varying degrees of protection. Selection of the running overcurrent protective device is based upon application requirements, cost, convenience, and performance. The advantages and disadvantages of each method of providing overload protection for three-phase low-voltage motors in a concise manner are outlined, so that an individual selecting overload protection for a motor circuit can be aware of the many considerations and select the overcurrent protective means that optimizes the concerns he feels are most important.     

无传感器汽车车窗防夹设计

无传感器汽车车窗防夹系统安装在车窗框内,通过继电器驱动直流电动机运转,其电流通过AD转换送到PIC单片机内进行处理,判断车窗是否遇到障碍物,从而实现防夹功能。     

电动机热过载保护研究

正在制定的IEC 60255-149电热继电器的功能要求和修订的DL/T 744微机电动机综合保护装置通用技术条件,均涉及到电动机热过载保护。阐述了电动机热过载的物理过程和热过载保护的构成、整定、试验和运行,并将基于电动机热模型的热过载保护与普通过流反时限保护进行定量对比分析,以便保护电动机免受热过载危害的同时,合理地利用电动机的过载能力。     

Motor bus transfer

The Motor Bus Transfer Working Group of the IEEE Power System Relaying Committee has performed a survey on industry practices for implementing automatic motor bus transfers in various power plant applications and the application of supervisory and control relays for these transfer schemes. This report summarizes automatic transfer methods for primary auxiliary buses that supply major rotating machinery loads. Fast, slow, parallel, residual voltage, and in-phase transfer methods are covered in this report. Information is also included on methods and criteria of acceptance testing of the motor bus transfer scheme     

起重机电动机的智能保护器

针对门座起重机电机过流保护继电器在实际应用中存在的缺陷,文章设计了智能型微机保护器,提高了电机过流保护的可靠性。     

新型低频减载方案的研究

在突然恶性事故情况下,电力系统产生严重的频率下降,导致系统崩溃和大面积停电。低频减载装置是一种抑制频率下降的有效方法,它依据测量到的频率值,按轮次分步骤地减掉负荷。这里介绍一种自适应型低频减载装置的方案,它依据频率和频率的变化率,动态地确定减负荷装置的动作情况。利用微型计算机实现这一方案完全可行。     

The universal overcurrent relay

A comprehensive list of nondirectional overcurrent relays would include thermal overload, inverse-time, definite time, and instantaneous relays. The list could be further classified by operating quantities including individual phase, residual, and negative-sequence current. Taken collectively and depending on the characteristic shape, pickup and time range, and dynamics, these relays span the applications for motor, feeder, and breaker failure protection. Because of the past necessity for using either discrete or specialized system relays, overcurrent characteristics for these applications may appear diverse and unrelated. However, microprocessor relay technology has advanced to where it is not only feasible, but it is of distinct economic advantage, to consider all these characteristics collectively as attributes of a universal overcurrent relay. This universal relay concept is used here to discuss the commonality, the differences, and the coordination of the elements required for feeder, motor, and breaker failure protection. The article goes on to discuss the rules for the coordination of negative-sequence overcurrent characteristics for sensitive phase-to-phase fault protection in feeders, as well as for unbalanced current protection of induction motors