Research On Setting Calculation Of Distance Relays And A Regional-Area Backup Protection Scheme For Transmission Lines

The protective relaying system plays a vital role in the power system.One of the keys to guarantee the reliability of protective relaying system is the accurate and reasonable relay setting.With the expansion of power system,the network topologies and operation modes are becoming more and more complex,which increases the difficulty of setting for traditional backup relays.The problems in the traditional backup relays,such as the overlong delay of relay action and the imperfection in relay coordination,become more serious.However,the developing power system demands better performance of the protective relaying system.To solve these problems,a practicable way is to use wide-area information to improve the performance of the backup protection system.The improvement and simplification of the setting calculation for distance relays are studied in this thesis.And a regional-area backup protection scheme based on the distance relays in local and neighboring substations is also proposed to improve the performance of backup protection system.Major outcomes of this research work include:1)The concept of source contribution coefficient is proposed.Based on the soure contribution coefficient,a novel method for source mode selection in relay setting calculation is proposed.Unlike traditional ways,this method does not include the process of permutation and combination.It is able to improve the calculation speed with high accuracy.In addition,the formula to calculate the variation of infeed coefficient after single-branch outage is deduced based on the sparse-oriented compensation method.And the corresponding selection method of single outage branch is proposed.2)The problems existing in the setting calculation of distance relays are analyzed.The hierarchical wide-area protection system is studied.Then,the concept and framework of regional-area protection system are proposed.On this basis,a novel setting method of zone-2 distance relays,along with a regional-area local backup protection scheme,is proposed.The complexity of setting calculation can be reduced and the speed of zone-2 distance relays can be improved.The simplified setting method of zone-2 distance relays combined with the regional-area backup relaying scheme is able to satisfy the requirement of selectivity,sensitivity and speed at the same time.3)A novel regional-area backup protection scheme with adaptive time delay is proposed.In this scheme,the simplified setting of the zone-2 and zone-3 distance relays is taken into account.The information from distance relays in neighboring substations are utilized to determine the time delay of local zone-2 and zone-3 distance relays.It is able to provide both the local and remote backup protection for transmission lines.4)The general design procedure of wide-area backup protection logic is analyzed.An optimization model for undetermined parameters is introduced,and the corresponding computation method based on particle swarm optimization is proposed.After using this method,the efficiency of solving undetermined parameters can be improved,and the inspection and correction of wide-area backup protection logic can be easier.