Researeh On New Principles Of Wide Area Adaptive Protection

In according to the change of the system operating condition, network topology and fault type, wide area adaptive protective relaying based on the wide area information can automatically adjust the protecive relaying setting in real-time so as to keep the protective relaying in the optimization state. Therefore, as an important part of the protection and control of smart grid, wide area adaptive protective relaying has broad development prospect. When power system is in normal working condition, wide area protective relaying system divides the protection zones. Once faults accur, adaptive protective relaying is in operating immediately. Therefore, wide area protective relaying system, wide area adaptive protection setting principles and fault phase selection method are studied in this paper.A circular grid formed wide area protective relaying system with overlapping coveraged protection zones is proposed in this paper. Then, the working mode of IED of this wide area protective relaying system is defined, and protection zone-division priciple and procrdure are established. Test results of IEEE-39test system and an actual68bus system in North America power system show that this wide area protective relaying system is feasible and suitable for being into practice.In this paper, two adaptive protection schemes are proposed. One is a novel wide area adaptive current protection scheme utilizing fault steady state current component. In this scheme, fault steady state network equivalent reduction is conducted by real-time network topology and system operating condition monitored by IED. Then, fault steady state current component of the related power transmission lines can be derived from fault steady state network equivalent reduction. Adaptive current protection settings criterions of zone I and zone II are established on the basis of the fault steady state current component. The regions of adaptive protection zone I and zone II which have been extended considerably are immune to the system operation condition, distributed generators connecting to the power network and the types of faults. The other is a novel adaptive voltage protection scheme based on the wide area information. In this scheme, distributed IEDs are used to storage the papameters of related transmission lines, monitor real-time bus voltage and line current and communicate with other related IEDs. On the bases of this wide area protective relaying system, adaptive voltage primary and backup protective relayings are established. The settings of this primary and backup protective ralayings can be adaptive to the system operating condition and fault type automatically. Comparing with the traditonal voltage protective relaying, the regions of this adaptive voltage primary and backup protective relayings are extented considerably.In accordance with the facts that the setting of adaptive protective relaying needs the correct results of fault phase selection, however, existing single fault phase selection method can not identify all types of fault, this paper proposes a new type of fault phase selection method based on phase current difference. This fault phase selection method firstly uses fault current measured at the protection devices setting place only to establish the fault phase selection factors(FPSF) based on the proportion relationship between the faulted phase current and the faulted line current. Then, the faulted phases can be identified fast and accurately by the FPSF in each fault types. The proposed fault phase selection method can identify any types and phases of faults in a cycle and has a high sensitivity. Furthermore, the method which has high capcbility and sufficient sensitivity to all tpyes of fault is not affected by the fault position and fault resistance and load current. It is also of interest to point out that this fault phase selection method has the capability of provide fault phase selection results for the wide area adaptive protection.