Digital substation refers to a substation that digitizes functions and communication methods of power facilities such as monitoring, measuring, control, protection, and operation based on IEC 61850, an international standard for the purpose of intelligent power grids. Based on the intelligent operating system, efficient monitoring and control of power facilities is possible, and automatic recovery function and remote control are possible in the event of an accident, enabling rapid power failure recovery. With the development of digital technology and the expansion of the introduction of eco-friendly renewable energy and electric vehicles, the spread of direct current distribution systems is expected to expand. MVDC is a system that utilizes direct current lines with voltage levels and transmission capacities between HVDCs applied to conventional transmission systems and LVDCs from consumers. Converting existing lines in substations, where most power equipment is alternating current centric, to direct current lines will reduce transmission losses and ensure greater current capacity. The process bus of a digital substation is a communication network consisting of communication equipment such as Ethernet switches that connect installed devices between bay level and process level. For MVDC linkage to existing digital substations, the process level was divided into two buses: AC and DC, and a system that can be comprehensively managed in conjunction with diagnostic IEDs as well as surveillance and control was proposed.
디지털변전소는 전력망 지능화를 위해 감시, 계측, 제어·보호, 운전 등 변전소를 구성하는 전력설비 기능과 통신방식을 국제표준인 IEC61850 기반으로 디지털화한 변전소를 말한다. 지능화된 운영시스템을 기반으로 효율적인 전력설비의 감시제어가 가능하며, 사고 발생 시 자동 복구 기능과 원격제어가 가능해 신속한 전력 장애 복구가 가능하다. 디지털 기술의 발달과 친환경 신재생에너지 및 전기차의 도입이 확대 되면서 직류 배전시스템의 보급이 확대될 전망이다. MVDC는 기존 송전계통에 적용되는 HVDC와 수용가에서의 LVDC 사이의 전압 레벨 및 전송용량을 갖는 직류 선로를 활용한 시스템이다. 대부분의 전력설비들이 교류 중심인 기존변전소의 기존 선로를 직류 선로로 변환하면 송전 손실 감소 및 더 큰 전류 용량이 확보된다. 디지털변전소의 프로세스 버스는 베이 레벨과 프로세스 레벨의 설치된 장치 간을 연결하는 이더넷스위치 등의 통신장비로 구성된 통신네트워크이다. 기존 디지털변전소에 MVDC 연계를 위해 프로세스 레벨을 교류부와 직류부로 나누어 두 개의 버스로 구성을 하였고 감시, 제어만 아니라 진단 IED와 연계되어 종합적으로 관리할 수 있는 시스템을 제안하였다.
B. Zhao, R. Zeng, Z. Yu, Q. Song, Y. Huang, Z. Chen, and T. Wei, "A more prospective look at IGCT: Uncovering a promising choice for DC grids," IEEE Industrial Electronics Magazine, Vol.12, Iss.3, pp.6-18, 2018.https://doi.org/10.1109/mie.2018.2855216
J. Y. Han, N. H. Lee, Y. H. An, B. T. Jang, J. K. Choi, S. K. Kim, and Y. J. Lee, "A study on field demonstration of full digital substation automation system," Proceedings of the KIEE Conference, pp.571-572, 2015.
M. J. Madera and E. A. Canizales, "The GPRS communication platform and DNP protocol as the best choices to communicate the SCADA with IEDs in the EDC distribution network," 2006 IEEE/PES Transmission & Distribution Conference and Exposition: Latin America, IEEE, 2006.
L. Zeyou and C. Yunqing, "Experience of using IEC 60870-5-103 and IEC 60870-5-104 transmission protocols [J]," Automation of Electric Power Systems 4, 2003.
IEC TR 61850-1:2013(Communication networks and systems for power utility automation -Part 1: Introduction and overview.)
Y. H. Kim, J. Y. Han, N. H. Lee, B. H. Kim, N. H. Park, and J. W. Hong, "The realiztion methods of IEC 61850 based 154[kV] substation automation system in KEPCO system," The Korean Institute of IIIuminating and Electrical Installation Engineers, Vol.24, No.5, pp.86-93, 2010.
H. S. Lee, "MVDC grid and System-MVDC distribution system configuration scenario," Korean Electrical Society Workshop, pp.1-8, 2018.
Z. Ma, W. Sheng, R. Li, M. Wu, R. D. Doncker, and P. Lurkens, "Study on the feasibility of MVDC," In Proc. CIGRE 2018 Paris Session, Working Group Sub Committee C6. 31, pp.1-12, 2018.
S. Whaite, B. Grainger, and A. Kwainski, "Power quality in DC power distribution systems and microgrids," Energies, Vol.8, No.5, pp.4378-4399, 2015.https://doi.org/10.3390/en8054378
S. Y. Yun, J. I. Kim, and J. T. Cho, "Application of IEC 61850 for smart distribution management system," KIEE Summer Conference, pp.106-107, 2010.
