An adaptive scheme for parallel-line distance protection

This paper describes an adaptive protective relaying scheme for parallel-line distance protection. The scheme adjusts its operation based on the availability of input signals to achieve an optimal distance protection performance on parallel transmission lines influenced by the mutual coupling effect. When available, zero sequence current from the parallel line is used to fully compensate the mutual coupling effect. The zero sequence current ratio is used to avoid possible false operations on healthy lines, which may result from such compensation. When the parallel line's zero sequence current is not available, the line operating status is used instead to select the proper zero sequence current compensation factors in impedance calculation. Default zero sequence current compensation factor is used when both the parallel line's zero sequence current and line operating status signals are not available. The performance of the scheme has been verified on a simulated network and the results are presented     

An adaptive approach in digital distance protection

Adaptive distance protection can be obtained by forming an adaptive control system, and rules about information, functions, and time sequence must followed in its design. Three adaptive methods are suggested to deal with the following problems: (1) the effect of frequency variation, (2) the effect of fault resistance in single-phase-to-ground faults, and (3) the effect of power swings in power systems. A prototype of digital distance protection has been designed and tested on a 500 kV dynamic power system model. Tests results show that the performance of distance protection can be improved by the adaptive methods     

A new approach for calculating zone-2 setting of distance relays and its use in an adaptive protection system

This paper presents a method for calculating zone-2 setting of distance relays without causing coordination problems. The proposed method is based on the impedance seen by distance relays when faults are simulated on the reach of zone-1 of primary relays for the maximum and minimum generation outputs of the power system. It is shown that the proposed method increases the reach of zone-2 relays without causing coordination problems. The proposed method is modified for use in an adaptive protection system. It is shown that further improvements can be achieved when settings are calculated using the proposed method and the prevailing system conditions. Measures to alleviate the impact of communication failure are discussed. The proposed method and its adaptive version were applied to an existing power system and some results are reported in the paper.     

11型微机相间距离保护做远后备的优越性及重要性

对常规相间距离保护和微机相间距离保护进行了比较,详细分析了微机相间距离保护阻抗特性与常规相间距离保护的不同之处,并用具体例子进行计算分析.通过计算分析剖析了微机相间距离保护做相邻元件后备保护的优越性及重要性.     

An expert system for the back-up protection of a transmissionnetwork

A back-up protection scheme for a transmission network is described in the paper. The back-up protection uses an action factor-based expert decision system (referred to as the BPES) to provide optimal fault clearance for faults located anywhere on the protected network. To achieve an optimal response, the BPES needs to know the topology of the network and the operating response of existing protection relays. Based on this information, the expert decision system will try to identify the feeder that contains the fault and which circuit breakers need to be tripped to clear the fault     

基于数据驱动的线路保护定值自适应整定方法研究

为了提高配电网供电可靠性,在配电自动化系统中,通过对线路开关的控制,实现配电网故障自动隔离与恢复供电。然而配电网拓扑复杂,线路重构后配电负荷和运行方式的改变,使得线路上的开关保护定值需要相应的调整,而传统联络开关无法解决这一难题。采用具有智能互联功能的联络开关,基于数据驱动思想,设计了一种线路保护定值自适应整定工作机制。智能联络开关作为线路的智能中枢,能够根据获取的分段开关遥测、遥信等数据,应用自适应整定工作机制来计算保护定值,实现线路重构后开关保护定值与配电负荷和运行方式的自动匹配。算例分析和工程实例验证了方法的有效性和适用性。     

An adaptive approach in distance protection using an artificial neural network

All relay settings are a compromise. Adaptive relaying accepts that relays that protect a power system may need to change their characteristics to suit the prevailing power system conditions. This philosophy has a wide range of applications covering many protective schemes. Here we consider a two-terminal transmission line, confirm that fault resistance and the location of faults can produce erroneous relay function and finally suggest ways to ensure the generation of the correct signal for relay operation. Retaining the microprocessor based framework, we show how artificial neural networks (ANNs) can be used effectively to achieve adaptive relaying for the above-mentioned problem. Adaptive relaying covers a large number of applications and the characteristics of relays vary widely, so the philosophy of adaptive relaying must vary accordingly. A modified multilayered perceptron model employs an additional node in the input layer. This additional input facilitates changes in the relay characteristic. The desired change in the quadrilateral relay characteristic is achieved by making appropriate changes in the thresholds and weights of the hidden layer neurons. A multiparameter adaptive scheme assumes that the additional input of the phase angle is available. Simulation results using ANNs for the different applications of adaptive relaying mentioned above are presented and discussed.     

自并励汽轮发电机相间短路后备保护配置与整定的探讨

与传统三级励磁方式不同,自并励发电机励磁电源通过励磁变取自发电机机端,机组发生相间短路时,随着机端电压的短路降低,励磁电源跟着衰减,尤其在机端发生三相短路时,励磁电源很快衰减至零,致使发电机提供的短路电流很快衰减至零,这就要求发电机后备保护的原理配置、定值整定与三级励磁方式的发电机有所不同。该文并对常见的几种用于自并励发电机相间短路后备保护的保护装置进行了原理分析,并提出相关的整定方法。     

自并励汽轮发电机相间短路后备保护配置与整定的探讨

与传统三级励磁方式不同,自并励发电机励磁电源通过励磁变取自发电机机端,机组发生相间短路时,随着机端电压的短路降低,励磁电源跟着衰减,尤其在机端发生三相短路时,励磁电源很快衰减至零,致使发电机提供的短路电流很快衰减至零,这就要求发电机后备保护的原理配置、定值整定与三级励磁方式的发电机有所不同.该文并对常见的几种用于自并励发电机相间短路后备保护的保护装置进行了原理分析,并提出相关的整定方法.     

一种适用于光伏场站送出线的自适应距离保护改进方案

由于光伏场站的弱馈性,当送出线路发生经过渡电阻短路时,传统距离保护可能无法正确动作。而自适应距离保护方案在一定程度上解决了区内故障保护拒动的问题,但存在区外故障误动的可能。首先分析了区外故障时自适应距离保护误动的原因,进而提出了一种自适应距离保护的改进方案。在现有自适应距离保护的动作特性基础上,引入线路的短路阻抗,根据区内、外故障下线路短路阻抗的大小差异,构成保护的辅助判据,以甄别可能引起现有自适应距离保护误判的区外故障。该方法仅依靠光伏侧电气量近似求取线路短路阻抗值,与现有自适应距离保护相互配合实现区内、外故障正确判别。最后通过PSCAD仿真验证了改进方案的有效性。     

An adaptive scheme to prevent undesirable distance protection operation during voltage instability

An adaptive algorithm to prevent undesirable distance protection operations during voltage instability is proposed. The algorithm is based on mathematical logic blocks and uses the rate of change of voltage as an additional relay criteria to increase the relay security with respect to voltage instability. Studies are based on simulations using two different test systems; a 15-bus system developed by the authors and the Nordic32 system. The investigation shows that undesirable zone 3 distance relay operations can be the difference between a blackout and a recovering system during voltage instability. However, simulations have shown that the adaptive algorithm may save the system from a collapse. Although the algorithm prevents mal-trips due to voltage instability, the reach of the distance relay will not be restricted.     

含光伏电源配电网的自适应距离保护

含光伏电源(PV)的配电网,因光伏电源的短路电流特性造成距离保护分支系数的不确定性,进而导致保护的拒动或误动。针对该问题,根据故障时的复序网络提出基于保护安装处的正序和负序电流的自适应分支系数计算,并以此为基础确立了距离保护Ⅱ段阻抗整定值。以某地区配电网为例通过PSCAD/EMTDC加以仿真,证明了在单相接地故障及相间短路故障情况下该整定方法的准确性与方便性。     

基于感受阻抗的相间距离保护整定计算方法

在分析传统相间距离保护速动段、配合段整定计算方法局限性的基础上,针对传统整定方法整定多端线路存在的不足,提出了基于感受阻抗的相间距离保护整定方法,并给出了通用的整定计算公式。该方法不受网络拓扑结构的影响,解决了整定线路、配合线路为多端线路时传统相间距离保护整定方法存在的问题,能有效提高多端线路上相间距离保护的保护范围及灵敏度,对于普通线路同样适用。通过算例,比较分析了传统整定计算方法和基于感受阻抗整定计算方法的定值性能,验证了所提方法的有效性。     

基于广域保护系统的距离后备保护整定方案

电网中发生潮流转移现象后,受影响的输电线路会承受大量的转移负荷,进入过负荷运行状态。距离保护后备段的整定要求躲开线路正常运行时的最小负荷阻抗,因此潮流转移带来的线路过负荷将会对距离保护后备段带来显著影响。针对这一情况,提出了一种能够应对潮流转移情况的距离后备保护整定方案。该方案基于广域保护系统,利用WAMS可测幅值与相角的特点快速计算线路的视在阻抗值。然后根据线路视在阻抗的变化幅度确定线路所承受的转移负荷比例,针对线路不同的过负荷状态进行与之对应的后备保护整定值调整,既防止过负荷线路上的后备保护发生误动,又使后备保护保有正确识别短路故障的能力。最后将整定信息与负荷波动情况上传至调度中心,为调度中心进行负荷控制提供辅助决策,并依据调度中心的决策进一步调整后备保护的整定值,直至线路恢复正常的负荷输送状态。以新英格兰10机39节点系统为样例,采用BPA仿真验证了该方案的有效性。     

基于感受阻抗的相间距离保护整定计算方法

在分析传统相间距离保护速动段、配合段整定计算方法局限性的基础上,针对传统整定方法整定多端线路存在的不足,提出了基于感受阻抗的相间距离保护整定方法,并给出了通用的整定计算公式.该方法不受网络拓扑结构的影响,解决了整定线路、配合线路为多端线路时传统相间距离保护整定方法存在的问题,能有效提高多端线路上相间距离保护的保护范围及灵敏度,对于普通线路同样适用.通过算例,比较分析了传统整定计算方法和基于感受阻抗整定计算方法的定值性能,验证了所提方法的有效性.     

配电变压器过流保护配置分析及完善方法

随着国民经济的迅速发展 ,电力需求日益增加 ,安全可靠供电显得越来越重要。用户对电能质量及年可靠供电时间有了更高的要求 ,除了提高配电网系统自动化水平外 ,对现场常用Y Y0 接线和Δ Y0 接线的配电变压器 ,选择适应系统特点的继电保护装置显得更为突出。由于诸多城市小区智能楼宇的兴起 ,大型厂矿企业等用电大户基本上都应用这两种方式供电 ,致使传统的熔断器和继电器保护上下级之间的电流定值难以配合 ,常常造成短路容量增加。该文通过对不同接线方式配电变压器的分析 ,进行模拟现场实验 ,确定出在使用上述配电变压     

配电变压器过流保护配置分析及完善方法

随着国民经济的迅速发展,电力需求日益增加,安全可靠供电显得越来越重要.用户对电能质量及年可靠供电时间有了更高的要求,除了提高配电网系统自动化水平外,对现场常用Y/Y0接线和Δ/Y0接线的配电变压器,选择适应系统特点的继电保护装置显得更为突出.由于诸多城市小区智能楼宇的兴起,大型厂矿企业等用电大户基本上都应用这两种方式供电,致使传统的熔断器和继电器保护上下级之间的电流定值难以配合,常常造成短路容量增加.该文通过对不同接线方式配电变压器的分析,进行模拟现场实验,确定出在使用上述配电变压器时,在保持传统低压配电系统的过流保护的同时,又能使保护装置快速有效的动作,这样使事故率大大降低,提高了供电质量.     

含UPFC线路的自适应距离保护研究

UPFC作为典型的FACTS元件,可以灵活地调节系统的功率传输,但也会造成线路参数变化,影响传统保护的动作,研究含有UPFC的输电线路对传统距离保护产生的影响.针对加入UPFC后造成的阻抗增量,提出两种自适应解决方案,使保护整定值成为可变的阻抗圆,随故障后UPFC状态变化而变化,使得距离保护能正确动作.