Research On Relay Coordination And Cooperation Of Extra-High-Voltage Transmission Lines

Complicated power network topology and changeful operating conditions bring challenges to protective relay coordination and reliable operation. It is very significative to investigate protective relay coordination and to improve the reliability and ability of cooperative operation of protective relays for protective devices to isolate faults in time and avoid great accidents. This dissertation devotes to the study of protective relay coordination and cooperation, including the research on relay coordination principles and approaches, the research on coordination automation technology and universality of relay coordination software, the research on vulnerability evaluation of relay protection system for transmission liens, and the research on wide area relay protection algorithm. Some research productions have been applied in the relay coordination software for many provincial and regional power networks, and the software improves the efficiency of relay coordination and the veracity of relay setting.The specific functions of different backup protections for grounding fault in ultra-high-voltage transmission lines are investigated to make full use of protective devices. The specific roles and functions are presented when zero sequence overcurrent relays, ground distance relays and breaker failure relays are used to isolate grounding faults. New priciples for calculating the settings of zero sequence overcurrent relays and ground distance relays are discussed based on the new presented scheme for configuring zero sequence overcurrent relays. The research makes the functions of backup relays more legible and hierarchical.New methods to calculate the settings of ground distance relay are proposed. To consider the effects of zero-sequence coupling on the grounding distance relay settings completely, a simple and applicable method to calculate the zero-sequence current compensation coefficient is proposed. A systemic method based on detecting impedance is proposed to calculate the settings of ground distance relay to overcome the shortages of all current setting calculation methods. The proposed methods are more applicable and the relay settings calculated based on the methods are more accurate. At the same time, a scheme about adaptive coordination of distance relays based on restriction conditions is discussed.On the aspect of coordination automation and intelligence technology, a method for automatic adjustment of relay coordination of transmission line protection based on sensitivity constraints is proposed. The method is implemented with two adjustment steps by introducing the concepts of the reset relay sensitivity constraint, remote backup relay sensitivity constraint and remote backup relay sensitivity transfer constraint. The relay coordination programme based on the method can adjust relay settings automatically to replace the protection engineers' work. At the same time, an approach for coordination sequence optimization is presented to guarantee the stability of relay settings in protection relay systems.The off-line mode and on-line mode of relay coordination are analyzed, and the integral framework and some key technologies are discussed. Performance of relay setting determined in the modes of off-line and on-line based on an existing power system is discussed in detail. It is show from the analysis that it will be very significative to achieve on-line relay coordination for improve the performance of protective devices.The diversity and regionality of relay coordination bring a bad effect on the development and extension of relay coordination software. To eliminate the effect, the universality of relay coordination software is deeply studied from the aspects of power system operating conditions combination, step relay setting calculation, protective device setting calculation and relay setting listing. A universal scheme of operating conditions combination based on selecting principles is proposed, while the universal scheme of step relay settings calculation based on user-defined principles is presented. At the same time, the implementation of universal step relay settings calculation software module is introduced.An approach to evaluate the vulnerability of relay protection system for transmission lines is proposed. The probability model of relay protection system unintended operation is established from the aspects of protective device and relay settings based on the characteristics of its functions composition, and the effect on power system reliable operation brought by the unintended operation of relay protection system is quantified in the form of load loss. The integrative index called vulnerability index is presented based on the probability and damage degree of relay protection system unintended operation. The index can reflect the vulnerable region of protection system very well.To take full advantage of more nodes information for the identification of faulted primary device, a wide area relay protection algorithm based on direction comparison is proposed, and the wide area protection system based on the algorithm adopts the configuration based on power substation. The Primary Devices/Direction Element associated matrices for primary devices in substation and transmission lines connected different substations are created separately according to the bus configurations and direction elements positions in power plant or substations. When a fault occurs in power network, Primary Devices/Fault Direction associated matrices are formed based on the fault direction indicated by direction elements and Primary Devices/Direction Element associated matrices, and then the faulted primary device is identified based on the above information.