Protection Characteristic Analysis And Novel Principles Research On The HV Transmission Line

In view of the scale-up of power grids and rise of the voltage levels, how to guarantee the safe and stable operation of power grid is turning to be a more and more serious challenge to power grids. In recent years, the successive blackouts in America and Europe have adequately proved the significance of searching for secure and reliable protective measures for the purpose of safety and reliability of power system operation. Therefore, a series of difficulties and issues existing in the field of protective relaying are investigated. Taking the actual operation scenario into account, in-depth studies from various aspects are conducted.In this dissertation, a novel method is put forward to analyze the performance of differential protection, which is able to evaluate any kind of percentage differential criteria under any operating scenarios. What's more, the security and sensitivity of two scalar product restraint criteria are analyzed by use of this method.In comparison with the security and sensitivity between phase current based differential criterion and fault component current based differential criterion, it can be proved that in the condition of many internal faults. The performance of fault component based differential protection is superior to the other one. At the same time, it can be disclosed that in the condition of earth faults, especially single-phase earth fault, phase current differential protection is superior to phase current based criterion in terms of integrated sensitivity. Therefore, some enhancement like zero-sequence differential compensation is worth adopting.According to the performance analysis of instantaneous-value based differential criterion, the corresponding functional relation between the multiple of operating current and initial phase angle of sampled current is disclosed. Furthermore, the study on the fuzzy operating area of instantaneous-value differential protection is demonstrated as well.During the power swing, the effective and quick blocking scheme for distance protections is required to avoid unwanted tripping. On the other hand, the rapid recognition for the three-phase symmetric fault is needed to unblock the distance protection. By studying the system frequency and the regular pattern of it during the power swing, an overall process power swing model for relay protection study is implemented. Based on this model, a novel method for power swing blocking in distance protection by means of the change rate of three-phase active power and reactive power is put forward. The simulation test results show that the distance protection can be blocked reliably in any period of the power swing by using this method. When symmetric faults occur, it can unblock the distance protection rapidly, which is immune to the influence of factors such as system parameters, fault occurring moment and fault position, etc.A novel strategy for self-adapting swing blocking meeting the engineering demands is proposed. It is proved as secure enough under any circumstance of power swings. When faults occur during the power swings, the sensitivity of this strategy is the highest among the available strategies as long as the fault resistance is not very high.In the aspect of wide-area protection study, a kind of regional protection system based on layered power system is put forward to cooperate with the existing main protection and back-up protection. The speed of this protection system is between the main protection and back-up protection, which increases the security of the whole protection system. Aiming at solving the problem of the Zone III of distance protection, as well as the overcurrent protection unwanted tripping caused by load flow transferring, a method of self-adaptive adjustment of setting is proposed. It is verified with the PSASP based simulation that this adjusting method is simple and effective, which could avoid unwanted action tripping by load flow transferring. Meanwhile, the functionality of remote back-up protection can be reserved when the faults occur on the adjacent lines. Finally, the achievements of this dissertation are concluded and the future work is prospected.