A study on automatic fault isolation of closed loop system in power distribution system

This paper describes the protected coordination algorithm that needs to be newly defined in changing the operation of the distribution line of the existing Open Loop or Radial system to the close loop system. The power is supplied to the load from a single power supply, and when a fault occurs, the direction of the fault current is also generated in one direction. Therefore, when a fault occurs in the protection coordination, the fault removal and recovery were performed by overcurrent protection coordination between devices as a one-way fault. However, environmentally-friendly and future-oriented power sources such as solar power and wind power generation of power distribution lines have increased, and the power source of lines has been multiplexed. Therefore, in case of fault, bi-directional failures are more likely to occur, and it is necessary to expand the safety of the system through new study on bi-directional fault and protection coordination. We have introduced communication-based system in protection coordination, and underground lines have already been applied to actual systems. In addition, the existing system is operating in a ring type communicated structure between devices through optical lines and wireless communication, so it is more economical by increasing the utilization of the operating system rather than investing in a new system. And because there are many extra core wires due to the characteristics of the optical fiber communication, it is utilized to secure the communication speed and maximize the optical wire utilization rate, and we had developed a dedicated communication module and terminal device. However, in the case of overhead lines which is composed many main and branch lines, and it is difficult to define fault and protection coordination for auto separation of fault sections. We have developed a protected coordination algorithm using 1:1 direct communication between protection devices for the close loop system operation of the overhead line. Also, The Device has function is fast response speed of fault and operation of various fault situations. It also defines various and unusual fault cases like blocking operation failure due to machinery and communication problem. So it has been improved in applicability to the actual system. This algorithm proved stable operation through experiments on actual distribution line of KEPCO PTC(Power Testing Center), Gochang, Republic of Korea. The application of this algorithm is expected to increase the acceptability and utility of the track and to utilize the stable power operation in the future energy market where various energy sources are developed.