Research On Key Technologies In Operation Of Local Distribution Network With High Temperature Superconducting Cable

As the rapid development of the national economy,urban load density is increasing.In large city,there are countless pipeline of transportation,energy and communication,and land price is extremely high.Conventional power distribution systems have faced the bottleneck of high-density power distribution.High temperature superconducting(HTS)cable,for its high-density power transmission capability,can provide a new technical approach for increasing the power distribution density of the distribution network in large cities.However,in addition to the technical problems of the superconducting cable itself,there are also several technical problems in the protection of superconducting cable and the load deployment of the distribution network when introducing superconducting cable into the distribution network.When a short circuit fault occurs in distribution network,a fault current that is dozens of times the rated current may flow through the HTS cable,which seriously threatens the safe and reliable operation of the HTS cable.The short circuit current distribution of the system after the HTS cable is connected to the power grid should be studied.In order to improve the economy of the distribution network with superconducting cable,the load allocation should also be optimized.In response to the needs of introducing superconducting cable into a local distribution network in Shenzhen,this paper analyzes and studies the transient and steady-state characteristics of local distribution networks containing HTS cable.Through the analysis of transient characteristics,a safety protection plan for HTS cable is proposed.In the steady-state analysis,an optimization plan for power distribution is proposed.The main works completed and the main results obtained are as follows:(1)According to the access plan of superconducting cable,a model of the Shenzhen local distribution network is built.The second-generation HTS tape and tri-axial HTS cable are mathematically modeled.The HTS cable model constructed is used for simulation in the power system model.(2)The short circuit current of the distribution network after the superconducting cable is connected is analyzed theoretically.The protection strategy of the short circuit fault between phases is introduced.The fault duration time is studied.The short circuit current distribution of system is verified by simulation,and the thermal stability of the HTS cable is researched.To cope with the excessive temperature rise of the HTS cable during fault process and the insufficient breaking capacity of the switch,a current limiting scheme with reactor is proposed,and the current limiting effect is verified.(3)The steady-state safety of the distribution network under the normal operation mode of is studied,and preventive solution against risks of overload and large voltage deviation are proposed.The power flow transfer under the N-1 operation mode is analyzed and a cross-section power flow control strategy is proposed.Based on the discrete particle swarm optimization(DPSO),the reactive power distribution of distribution network is optimized to improve the economics of grid operation.