多环电网方向保护整定计算中形成有向简单回路的新方法

在高压或超高压电网的距离保护和零序保护的整定计算过程中，首先要确定全网的最小断点集(MBPS)，然后在断点集的保护安装处打开断点，使得全网变为辐射网络。其中，多环复杂电网中有向简单回路的确定是求解最小断点集的关键，也是其必要步骤之一。为了最大限度地减少多环复杂电网中有向简单回路的计算复杂性，该文提出了一种保护依赖度和主／后备保护依赖集的新概念：将所有有向简单回路的形成过程归结为环网中所有保护依赖度大小的比较和保护依赖集的不完全深度优先搜寻过程。通过比较保护依赖度的大小来确定每次方向回路搜索的起始点，并通过对保护依赖集的深度优先搜索来确定所有有向简单回路。该方法能统一处理环网中的‘T’形接线、辐射线路等保护的配合问题。算例表明该方法简单有效，显著地降低了计算的复杂性，可方便地应用于高压或超高压电网的距离保护和零序保护的整定计算。     

基于改进教与学优化算法的最小断点集求解

对继电保护装置开展合理的整定计算工作是保障电网安全稳定运行的重中之重。环网继电保护整定过程中可能出现“死锁”问题导致整定无法进行,需要寻找网络最小断点集(Minimum Break Point Set, MBPS)以解开“死锁”。实际工程中,由于电网运行状态或评价角度的改变,被选作最优断点集的一组MBPS应当更新。针对该问题,致力于寻找一种能够快速高效地找到网络拓扑中尽可能多组MBPS的方法,为更新当前最优断点集提供可能。将寻找MBPS的问题归结为求解一个0-1整数二次规划问题,引入教与学优化算法,并对算法进行一定改进以提升搜索性能。与其他启发式算法相比,该算法只需要设置较少的超参数,可行性较高;并且收敛性好,能够以较少的迭代次数得到全局解;同时,该算法一次独立计算能够得到足够多组MBPS,为在工程实际中结合电网运行参数确定环网最优断点集提供条件。通过算例验证了该方法的有效性。     

最小断点集的简化计算与组数扩充

为简化最小断点集的计算,通过割节点对电网进行分割。在每个子网中,根据主后备保护配合关系,形成了保护配合矩阵,并对矩阵进行化简以降低保护配合矩阵的维数,通过动态调整保护配合矩阵得到子网的最小断点集。将最小断点集的分布规律引入到计算过程中,扩充最小断点集的组数。算法在降低计算量的同时可得到多组最小断点集。通过算例验证了所提出方法的简易性和实用性。     

一种适用于继电保护在线整定的极小断点集求取算法

复杂环网中继电保护在线整定的顺利进行依赖于极小断点集的快速求取,但现有极小断点集求取算法在算法复杂度、断点集维数及计算效率等方面还存在不足。对此,提出了一种适用于继电保护在线整定的极小断点集求取算法。该方法基于图论中基本割集矩阵与基本回路矩阵的固有关系,将复杂环网的断点集求取问题转换成了基于基本割集矩阵的基本回路断点集求取问题。通过动态调整基本割集矩阵,逐步计算得到网络极小断点集。算例分析表明,所提算法能够在有效的时间内求得网络极小断点集,大大降低了问题的复杂性。     

基于网络化简和配合关系的最小断点集计算方法

基于保护主后备配合依赖关系有向图,提出了通过有向图化简计算保护配合最小断点集（MBPS）的新方法。定义了配合依赖关系有向图化简操作的顺序和原则,按照优先级顺序将保护分类,根据保护后备依赖度最大原则从具有较高优先级的类中选择候选断点,将化简过程中得到的自环顶点选为断点。所述方法适用于环网全网配合和同段配合中MBPS的计算。     

一种求解复杂环网保护配合最优断点集的新方法

为确定复杂环网保护配合中的最优断点集,引入了4个指标作为最优断点寻找的评判依据,建立了寻找最优断点集的数学模型。基于细菌群体趋药性算法的基本原理,提出了计算最优断点集的新方法。较已有的计算断点集方法,所述方法可以快速地找出最优的最小断点集。算例分析证明了该方法的有效性和实用性。     

适用于任意拓扑结构变更的最小断点集更新方法

电网拓扑结构变更后快速更新最小断点集是提高在线整定计算速度的关键方法之一。文中提出了一种适用于任意拓扑结构变更的最小断点集更新方法。该方法根据线路投退和母联开关开合后简单回路变化的特性,推导了断点的演化规律,并将此规律映射为保护关联矩阵的相关计算,从而实现了最小断点集的快速更新。同时,在任意拓扑结构变更的情况下,该方法均能保证更新后的断点集为最小(或极小)断点集。以某省级电网500kV线路网络为算例,结果表明了所述方法的正确性和有效性。     

确定复杂环网保护配合关系有向简单回路的新方法

复杂环网保护配合关系中所有有向简单回路的确定是求解最小断点集的关键步骤。文章提出了一种基于图论理论确定复杂环网有向简单回路的新方法,引入层间隔回路判断原则,通过搜索简化后的网络节点邻接矩阵,同时利用保护配合关系的对称性,无需回溯便可快速确定全网所有有向简单回路。该方法形成的网络矩阵规模较小,计算流程简单直观。算例结果证明了该方法的正确性和实用性。     

基于配合依赖关系图计算环网方向保护最优配合顺序的新方法

提出了基于保护主后备配合关系,利用保护配合依赖关系有向图节点邻接矩阵计算环网方向保护最优配合顺序的新方法。根据节点入度最大的原则逐步选择断点,根据节点出度为0的原则确定保护配合顺序,通过对节点邻接矩阵简单的行列化简运算逐步计算大规模复杂环网最小断点集和确定全网保护最优配合顺序。该方法简单直观,大大降低了问题的复杂度和计算量。     

适应网络变结构的最小断点集更新算法

提出一种在网络变结构情况下利用虚拟断点集快速更新最小断点集的新方法。该方法首先根据静态网络拓扑形成包含保护关联矩阵、最小断点集、保护相对顺序表以及断点相关元素集的网络初始信息库。当网络结构发生变化后,首先判断变结构类型,再根据网络初始信息库确定虚拟断点集,在此基础上,重构保护关联矩阵,利用其部分元素计算新增或可删除断点...     

一种新的基于图论确定所有最小断点集方法

在复杂环网的继电保护整定计算过程中,必须确定方向过流保护和距离保护的整定配合顺序,而整定计算的起点即断点的确定尤为重要。利用图论方法确定了一些旨在降低求取最小断点集问题复杂度的原则,如网络分割、最少断点数的确定、不考虑相邻保护、对称、无平行线网络选择断点等原则,并利用这些原则提出了逐步求取网络所有最小断点集的方法。算例表明该方法降低了计算最小断点集问题的复杂度,且具有一定的有效性和通用性。     

基于配合关系计算复杂环网保护最优配合顺序的新方法

基于保护主后备配合关系,引入并定义了保护配合主依赖度和后备依赖度的概念来描述保护之间的配合依赖关系,提出了通过动态调整保护主依赖度和后备依赖度逐步计算复杂环网最小断点集和确定全网最优配合顺序的新方法,根据保护后备依赖度最大的原则选择候选断点和主依赖度为0的原则确定保护配合顺序,同时给出了详细的算法流程和算例分析.该方法简单直观,计算量小,只需利用基本的配合关系,完全不需要形成全网所有有向回路,有效解决了多环复杂网络中方向保护全网最优配合问题.     

Time coordination method for power system protection byevolutionary algorithm

A typical industrial power network may consist of hundreds of pieces of equipment and even more protection relays to protect the system are required. Each protection relay in the power network needs to be coordinated with the relays protecting the adjacent equipment. The overall protection coordination is, thus, very complicated. A new concept of protection coordination by time is introduced in this paper to formulate all the system relays and system equipment operation into a set of optimization equations and constraints. Its purpose is to search for an optimal protection setting to minimize the system disturbance time as well as the time of interruption of the power supply. An evolutionary algorithm is applied as a constraint satisfaction optimization tool to search for the optimal relay setting. This method can find the best protection relay coordination, which cannot be achieved by traditional methods. This is the most significant achievement of the paper     

基于蚁群算法的环网方向保护配合最小断点集计算

利用复杂环网方向保护最优配合中最小断点集（MBPS）的启发性知识,将MBPS的计算问题等价为0-1整数规划问题。基于蚁群优化算法基本原理,构造了适用于MBPS问题的启发信息计算公式,改进了更新信息素浓度的计算方法,提出了计算MBPS的新方法。相对于其他计算MBPS的算法,所述算法所需迭代次数较少,通过一次计算即可同时获得多组最优解。     

Data-mining model based adaptive protection scheme to enhance distance relay performance during power swing

The paper presents a data-mining model based adaptive protection scheme enhancing distance relay performance during power swing for both compensated and uncompensated power transmission networks. In the power transmission network, the distance relays are sensitive to certain system event such as power swings, which drive the apparent impedance trajectories into the protection zones of the distance relay (zone-3) causing mal-operation of the distance relay, leading to subsequent blackouts. Further, three-phase balanced symmetrical fault detection during power swing is one of the serious concerns for the distance relay operation. This paper proposed a new adaptive protection scheme method based on data-mining models such as DT (decision tree) and RF (random forests) for providing supervisory control to the operation of the conventional distance relays. The proposed scheme is able to distinguish power swings and faults during power swing including fault zone identification for series compensated power transmission network during stress condition like power swing. The proposed scheme has been validated on a 39-bus New England system which is developed on Dig-Silent power factory commercial software (PF4C) platform and the performance indicate that the proposed scheme can reliably enhance the distance relay operation during power swing.     

New coordination approach to minimize the number of re-adjusted relays when adding DGs in interconnected power systems with a minimum value of fault current limiter

The presence of DGs in power networks tends to negatively affect relays coordination. Adding fault current limiters FCLs is one of the possible solutions to mitigate negative impacts of DGs addition on protection systems. Traditional schemes have estimated the minimum value of FCL to restore relays coordination when adding DGs without resetting of any relays. That minimum value of FCL in such case is called a critical value, where below this value the relays coordination will be lost.Nowadays, designing FCL to simultaneously achieve two conflicted objectives of good performance and low cost is considered a great challenge. The paper introduces a new scheme to determine to what extent we could decrease FCL impedance value below its critical value with re-adjusting the original settings of only one adaptive relay to get relays coordination. Decreasing FCL value below its critical value will reduce the cost especially for superconductivity FCL. The proposed scheme can determine the location of that selected relay to be an adaptive one and estimate its re-adjusted new settings to be applied when DGs are added while inserting the reduced value of FCL.Actually the proposed scheme can be applied for any networks irrespective of the number of added DGs and their capacities; while having an adaptive relay is the only requirement to implement it.The proposed approach is implemented and effectively tested on the large well-known interconnected IEEE-39 bus test system with 84 relays. Its results are compared with other approaches where, no re-adjusted relays settings are applied. A noteworthy advantage of the proposed scheme is the ability to implement a reduced FCL value than the critical value, by adjusting only one relay settings in the whole network. The proposed scheme may also be extended to re-adjust settings of more than one relay and get further reduced value of FCL. Furthermore, it is also shown that a more optimum value of the total operating time of all primary relays for near end faults is achieved when applying the proposed method rather than other traditional schemes.     

A comprehensive method for break points finding based on expert system for protection coordination in power systems

Interconnected power systems are multi-loop structured. In such networks, the determination of settings for all overcurrent relays can be carried out in different forms and may be quite complicated. The main problem for coordination is the determination of starting points, i.e. the location of starting relays in the procedure for settings, which is referred to as break points. In this paper, a powerful approach based on expert system is applied. The rules of the expert system include network configuration, protection systems, fault levels, etc. The method is applied to two networks with different configurations, pilot protection and other protection systems. From the obtained results, it is reviled that the new method is efficient, accurate, comprehensive and more optimal than the previously used graph theory.     

A novel algorithm to determine minimum break point set for optimum cooperation of directional protection relays in multiloop networks

Determining minimum break point set (MBPS) is necessary before setting distance protection relays or zero-sequence protection relays in multiloop extremely high voltage power networks. Determining directional simple loops (DSLs) and relative sequence groups (RSGs) is the prerequisite of traditional algorithms which are used to determine MBPS. In order to reduce the CPU time and complexity of calculating MBPS, a new concept named as protection relay dependency dimension (PRDD) is presented for the first time in this paper. By comparison of PRDD in a multiloop network, the MBPS can be determined, and the process of comparisons will not stop until the MBPS of the multiloop networks is discovered. In the meantime, the RSG could be easily determined by means of judging whether the primary protection relay set of a protection relay is null or not. The new algorithm leaves out those laborious steps, such as determining all of the DSLs and RSGs. Some examples are given to illuminate the novel algorithm presented in the paper to be simple and effective.