Yoshizumi Serizawa

Concept design for a Web-based supervisory control and data-acquisition (SCADA) system

Rapidly advancing hardware and software technologies have made it possible to develop a new generation of supervisory control and data-acquisition (SCADA) system. The Web-based SCADA system described here consists of intelligent RTUs, each of which has a modularized hardware architecture and supports HTTP protocol, and a distributed master station, which has a Web server/browser structure and decomposes the SCADA functions into multiple sets of Web site components. Both the hardware design and software development for this Web-based SCADA system have been carried out in accordance with well-proven architecture modules, allowing the system to benefit from numerous available technologies and giving it added flexibility and scalability.

Transmission delay variations in OPGW and overhead fiber-optic cable links

Round-trip transmission delays in a 128.5-km optical ground wire (OPGW) link and 12.5-km and 12-km overhead fiber-optic cable links were measured to clarify the effect of meteorological conditions, dominantly atmospheric temperature, on the delay variation. Transmission delays measured at 5 a.m. can be well expressed only in terms of atmospheric temperature along the links, while those at 1 p.m. can be expressed using four meteorological parameters of atmospheric temperature, sunshine duration or solar radiation, wind speed and precipitation. The coefficients of delay variation with respect to atmospheric temperature range approximately from 60 to 100 ps/km//spl deg/C where the cable links are more affected by temperature than the OPGW link, and delays in the daytime vary more than in the nighttime due to solar radiation. The results could be used for estimating the increase of cable temperature due to solar radiation and for designing fiber-optic time transfer networks effective for power system protection.

SDH-based time synchronous system for power system communications

As precise time information is particularly useful for power system communications, a time transfer system using terrestrial fiber optic digital networks, or SDH (synchronous digital hierarchy)-based time synchronous networks, is proposed in addition to radio- or satellite-based time dissemination systems such as GPS (Global Positioning System). In the system, auxiliary synchronizing equipment is attached to existing networks composed of SDH transmission equipment and digital clock supplies, and not only frequency but also frame phase or time is synchronized. Experimental time synchronizing devices showed potentially satisfactory performance; synchronization errors between two devices were of the order of sub-microseconds.

ATM transmissions of microprocessor-based current differential teleprotection signals

This paper describes prudent considerations for applying asynchronous transfer mode (ATM) transmissions, which can provide broadband and multimedia communications as well as flexible, efficient and wide-area networks, to microprocessor-based current differential teleprotection systems. As both functions of current data transmission and simultaneous sampling among remote terminals are required for the telecommunication systems, measures against cell losses and cell delay variations in ATM network elements such as terminal adapters and switches are proposed for the present delay-sensitive teleprotection systems. Allowable system configurations are examined under severe delay constraints in Japan. A new concept of an ATM-native teleprotection system employing time synchronous systems such as GPS is also proposed.

Present and future ICT infrastructures for a smarter grid in Japan

This paper first provides a vision of a future power delivery and utilization grid in Japan, and reviews the present information and communication technology (ICT) infrastructure for existing power grids. Based on this vision and review, future ICT infrastructure to cope with the significant penetration of photovoltaic generation, legacy communication equipment and aged power assets is proposed for wide-area monitoring and emergency protection and control, demand area secure communications, and ad-hoc and plug-and-play sensing for maintenance. This will enable the renovation of ICT infrastructure for a future Japanese smarter grid.

Examination on the applicability of IP-related communications to teleprotection systems

This paper preliminarily examines the applicability of Internet protocol (IP)-related communication technologies such as IP and MPLS (Multi-Protocol Label Switching) routers and L2 (Layer-two or Ethernet) switches to existing teleprotection systems. The teleprotection systems concerned include microprocessor-based current differential teleprotection with data communications of instantaneous current values or phasors, directional comparison teleprotection, and special or system-wide protection. Taking account of the performance limitations of IP-related telecommunication networks, fully redundant L2 switch networks are indispensable, as is an external timing synchronization scheme for current differential teleprotection. Based on the analyses, a new concept for modernizing teleprotection system associated with L2 switch networks, time synchronization and modular devices is proposed.

Study on Delay Time Evaluation for Carrier Relay System Using IP Communications Technology

The transmission devices of carrier relay system use exclusive transmission devices and do not use IP (Internet Protocol) communications technology. But the IP communications technology has made remarkable advances recently and is used in the world. If Internet technology can adapt for the transmission device of carrier relay system, electric power company can construct the integration network for power protection and control system which includes carrier relay system. In this report, we will assume the network configuration using Internet technology for the transmission devices of a carrier relay system and show that the transmission devices using Internet technology satisfy the carrier relay specification, such as delay time and differential delay time.