Fault Location and Auto-Reclose for Hybrid Lines Based on the Application of FOCT
Hybrid lines have been widely adopted for their flexibility and reliability.Most faults on over-head lines are temporary and auto-reclose should be initiated after the clearance of the faults to keep power supply, whereas most faults on underground cables are permanent that auto-reclose should be blocked to prevent further damage to cables.Therefore it is the key issue to distinguish the section in which the fault occurs and whether it is a permanent fault.The conventional solution to discriminate the fault section on hybrid line is based on the impedance measurement, however the measured impedance based on voltage and current at one side is not accurate enough to determine the fault section, especially for the fault near the junction as well as high impedance fault, it is possible that fault section is distinguished incorrectly, which might cause the closing on cable permanent fault.After the clearance of the fault, protection relay should give the information of fault location, but the fault point based on the measured impedance is quite difficult to define.The conventional solution for fault location of protection relay is generally based on the measured impedance, which supposed the same parameter along the whole line, but because of the parameter difference between overhead line and cable, the fault location is very difficult to calculate accurately.So it will take long time for maintenance to find the fault point.A new solution is proposed in this paper.By the installation of optical current transformer (OCT) at the junction where cable is linked with overhead line, the current value via optical cable is sent to protection relay installed in substation.After the obtainment of current at both sides, the relay in substation will synchronise the currents of both sides, then based on the philosophy of differential current, the fault section can be discriminated.If the fault location is confirmed in cables, then auto-reciose will be blocked and corresponding signal will be issued.After the discrimination of fault section, the fault location can be calculated accurately according to the parameters of overhead line and cables respectively as well as the voltage and current from both sides.Finally, the RTDS simulation test is established and implemented on different voltage levels; cases are studied and evaluated with various fault locations and fault impedances.The test results prove that this method can effectively distinguish the fault location properly as designed.Because of the flexibility and reliability and safety of flexible optical current transformer (FOCT) system, this solution presented in this paper can be used for all similar system.What is more, the installation of FOCT does no affect to primary equipment due to the flexibility and simplicity of FOCT system,and will not disconnect the running system.Thus, the severe damage to cables and impact to power systems due to the permanent fault are avoided , the problem of fault location caused by the different parameters of cable and overhead lines is solved The solution of FOCT system including FOCT, MU and protection relay.The disadvantage of FOCT system is the requirement of communication channel from MU to protection relay, which will increase the investment.
Auto-reclose Fault location Fault section Hybrid line Integrated current differential protection Optical current transformer
Jun Shen Xiaotong Zhu Liguo Xu Geming Liu Qingchun Zhao Jun Zhao
NR-Electric, China
国际会议
南京
英文
175-180
2015-09-21（万方平台首次上网日期，不代表论文的发表时间）