Design of 23kV 50MVA class HTS Cable in South Korea

Abstract

The world first commercial project for the superconducting applications is already starting in South Korea. The first step of the project named SSS (Superconducting Smart platform Station in South Korea) is to operate AC 23kV 50MVA class HTS cable system in the power grid of Korea Electric Power Corporation (KEPCO) in order to increase the power capacity and realize the stable operation. The above HTS cable system will connect two substations between ShinGal and HeungDuk. Total length of the HTS cable is approximately over 1km including 2 sets of the normal joint box and 2 sets of the termination which are the out-door type accessories. Before performing the type test, various preliminary tests with the short cores were performed to confirm design of the HTS cable. To meet the design goals, the HTS layers of the core consist of the two conducting and one shield layer. The characteristics of the HTS wire is the non-magnetic 2nd generation wire. It can reduce the magnetization loss caused by itself and adjacent the HTS wires. The measured AC loss is around 0.3 W/m at 1,260 Arms and increasing trend of AC loss by operating current is the well fitted of simulation results. In case of short-circuit test, experimental temperature is approximately 77K and increased maximum temperature is under 92.8 K which is enough below the boiling temperature of LN2 at gage pressure 6.7bar.(g). A 70-meter-long the HTS cable including unit the test samples and an 85-meter-long LN2 return pipe will manufacture and installed for the type test at KEPCO Power Training Center in Gochang, South Korea. The type test procedure is following the Cigre TB538 and KEPCO standard those are including the 20 cycles load test, voltage tests such as AC withstand and impulse, repeated cooling process three times as prequalification quality test and visual inspection after disassembling. In the third quarter of 2018, LS Cable&System will supply and install AC 23kV HTS cable system in South Korea.