【作者】 薛士敏；

【导师】 张艳霞； 贺家李；

【作者基本信息】 天津大学 ， 电力系统及其自动化， 2005， 硕士

【摘要】 随着电网的发展将出现更多的超高压和特高压输电线,研究新的保护原理,使线路故障能够快速、准确的切除,是保证电网安全稳定运行的关键。由于电流互感器饱和和线路分布电容电流等因素的影响,使得在外部短路时产生很大不平衡电流,可能造成电流差动保护装置误动作,因此必须采取制动措施。目前各种制动原理都不能既保证在外部短路时有很强的制动作用,而内部短路时又能保证很高的灵敏度。为此有些保护采用了复杂的折线式制动特性,这将使保护复杂化且整定困难。本文所提出的微机自适应方向纵差保护原理的制动特性随对端的电流的增大呈非线性增强,内部故障时制动量转化为动作量,充分保证了外部故障时的安全性和内部故障时的灵敏性,可解决这一难题。该原理是国内外首创,原理中制动系数(大于1)可以选择得很大,没有任何限制。同时,提高制动量,并不影响内部故障时保护的灵敏度,相反的可增加保护的灵敏性。文中分析了其判据和动作特性,并对该原理与其他典型的带制动特性的原理进行了详细的比较,通过比较充分体现了该原理的优越性。通过大量仿真试验证明了此新原理在500KV和750KV的特高压输电线路上都具有良好的性能。K′′/K′利用该原理编出了一套微机分相电流差动保护程序。利用本原理的保护装置在本端CT断线时不会误动,此时对端保护不起动也不会误动,为了防止此时发生外部故障使保护误动,可以经延时闭锁本端保护并通过通道闭锁对端保护。此保护程序中设有多种工作方式(即“或门”出口方式、“与门”出口方式和远方跳闸方式),可以根据不同的系统要求采取不同的工作方式,这样大大增加了保护装置的可靠性;采用采样值差动和本原理相结合,以加快保护动作;采用零序过流保护作为后备保护,同时用以解决高过渡电阻接地故障时主保护灵敏度不足的问题。按此原理研制的装置通过了用保护测试仪进行的测试。更多还原

【Abstract】 More extra-high voltage (EHV) and ultra-high voltage (UHV) transmission lineswill appear with development of power system in China. Study of new protectionprinciple is an important approach to ensure quick and correct switching off faultsand to maintain power system stability. On account of influence of currenttransformer saturation and distributed capacitive currents of the protected line, greatunbalance current will be produced during external faults and make protection tomal-operation, so that some restraining measures must be adopted. There are manyrestraining principles proposed, but at present, they can’t assure strong brakingeffect during external faults as well as high sensitivity during internal faults.Therefore some protections adopt complicated restraining characteristic of polygonalform,it makes protection complicated and difficult to select proper settings for it.Restraining characteristic of microprocessor-based adaptive segregateddirectional current differential pilot protection principle proposed in this paper putsforward a nonlinear restraining characteristic, the restraining quantity increases withincrease of the current of other side nonlinearly and will change into operatingquantity during internal faults. This assures sufficient security during external faultsand sensitivity during internal faults and resolves the aforementioned problem. Thisprinciple is original and firstly proposed in this paper.Values of restraining factorin this principle can be selected as any big values without any restricts.At the same time, increase of restraining quantity does not impact on sensitivityduring internal faults , just the contrary, it increases protection sensitivity. In thispaper the criterion and operating characteristics of it are analyzed and compared withother principles in detail.The comparison shows the advantage of the new principle.Many simulation studies of the protection on EHV and UHV transmission lines500kV and 750kV show the correctness and advantage of the new principle.K ′′ /K′A microprocessor-based segregated current differential pilot protection programhave been worked out based on the new principle. This protection will not mal --operate during CT circuit breaking at one side, at the same time the protection at theother side will not start , so the protection will not mal-operate as a whole. Theprotection can be blocked with a time delay by using the communication channelfor the purpose to prevent the protection from mal-operation owing to external faults.In the protection program three working modes are considered such as output trippingcommand through AND gate, OR gate or transfer trip by communication channel inorder to increase reliability and the flexibility.The program is developed based both on sampled values and on phasors usingthis new principle. Directional overcurrent protection of zero-sequence was used asback up protection, it ensures sufficient sensitivity of protection during ground faultthrough high intermediate resistances.更多还原