Research On The Relay Protection Technology Adaptive To High Temperature Superconducting Cable Access

High temperature superconducting(HTS)cable has many advantages such as low power loss,large transmission capacity,small occupation space,and environmental friendliness.It provides an efficient,compact,reliable and green power transmission mode for power grid,and has great application potential in large capacity transmission and urban power grid expansion and transformation.However,the structure of HTS cable is complex,and there are major differences from traditional cable line in terms of operating conditions and fault mechanism,and the requirements for secondary systems are also more stringent.Therefore,based on the project of "research and demonstration application of key technology of superconducting transmission in urban distribution network" of China Southern Power Grid,in-depth research on the relay protection technology adaptive to HTS cable access was carried out.According to the mechanism and performance characteristics of the short-circuit fault and quench fault of the superconducting cable body,the overall construction scheme of the superconducting cable protection system based on short-circuit protection and quench protection was proposed.With fiber optic current differential protection as the main protection,phased directional phase current protection and zero-sequence current protection as backup protection,short-circuit protection can achieve fast and reliable removal of various types of short-circuit faults.Quench protection adopts a layered comprehensive protection scheme based on electrical characteristics and non-electrical characteristics of the cable port and temperature distribution characteristics along the line.For the quench fault caused by the short-circuit current impact,the electric quantity quench detection method is used to speed up the detection speed.For the quench fault caused by the abnormality of low temperature system or cable body,the non electric quantity quench detection method is used to improve the reliability and accuracy of the detection.At the same time,the technical measures such as sequential action protection and self recovery control are used to further improve the power supply reliability of superconducting cable.Aiming at the problem of local quench fault detection,according to the peak characteristics at quench heat-generating zones of the temperature waveform along the conductor layer after the local quench of superconducting cable,a local quench detection and protection method for superconducting cable based on distributed optical fiber temperature measurement technology was proposed.The method uses the fiber optic temperature measurement system to measure the temperature along the conductor layer of superconducting cable,calculates and determines the local quench heat-generating zones through multi-resolution morphological gradient technology,and carry out alarm and tripping according to the size and temperature rise of quench heat-generating zones.The simulation results show that the method has good anti-noise performance,can accurately detect and judge the quench heat-generating zones and the quench fault severity,and effectively ensure the operation safety of superconducting cable.Taking the actual engineering application of superconducting cables as the background,the equivalent model of power grid with superconducting cable was constructed,and the distribution characteristics of the short-circuit current of the power grid under different operating modes after the superconducting cable access were analyzed.On this basis,from the perspective of ensuring the selective and reliable removal of faults and reducing the impact of short-circuit current impact on superconducting cable,the configuration scheme and coordination coordination strategy of power grid protection adaptive to superconducting cable access were proposed.The research shows that compared with the traditional protection configuration scheme,the proposed scheme can effectively reduce the duration of the fault while ensuring the reliable isolation of the fault,and better guarantee the operation safety of the superconducting cable.The research conclusions have been practically applied in the engineering transformation and equipment selection of the power grid protection system.