Power islands get remote control

Tepco supplies power to the offshore-Tokyo islands of Ooshima and Kozushima and some smaller islands in the same area from diesel power generation equipment that it owns and operates. To raise the efficiency of its operations Tepco decided to install a remote control and monitoring system on Ooshima to control the diesel generators, electrical systems and common auxiliaries on Kozushima. Communication between the systems is by microwave transmission. Mitsubishi received the order for a system based on its Diasys Netmation product and installation was completed in mid-2003. It has now been running for a year and Tepco's evaluation has given it a high rating in terms of reliability and the flexibility to deal with problems as they arise. There is a plan to extend the system to cover two smaller islands a little further out to sea.

Function

Control and monitoring of the Kouzushima power station can be carried out from two stations installed at the Ooshima power plant. This includes the diesel power plant’s basic functions, including circuit breaker, voltage and frequency control and synchronisation, as well as supervision of plant conditions, alarms and outage displays, display of total output and main process data of the plant, trend displays, supervision of working values for the generators and engines (pressure and temperature), and operating auxiliary equipment.

The communication line is duplicated. One is Tepco's house line at 96 kbps and the other is the NTT’s (Japanese telephone company) dedicated line at 128 kbps (32 kbps is used for maintenance of the system). The condition of the diesel generators and ITV images can be monitored from a large PDP display.

The controller

The system has CPUs at the monitored station on Kouzushima island. The operator CPU installed at the monitoring station calls up the necessary data when required to the display. Data streams are minimised to ensure the fastest response over the low speed communication line and to endow the network with some operational security where an unstable communication infrastructure is being used. Data storage and control can continue automatically even in the event of a communication failure.

Diasys Netmation is MHI's total plant control system. It is based on communications technologies such as the Internet and intranets. In addition to the operator stations found in central control rooms, browser-based operator stations are also available, so plant operation and monitoring are possible from any location, such as a laptop or an office desk; and plant monitoring is possible from remote locations using telephone landlines. The system is protected by a firewall.

The system uses general information technologies, such as IP protocol communication, Windows etc, so that proprietary products such as PCs can be utilised, thereby helping to lower capital costs. Moreover, system expansion, and integration with office automation are simplified while a high level of redundancy can be incorporated.

The system permits all the instrumentation and control equipment of not the plant's primary machinery and equipment, as well as its water treatment facilities, coal storage facilities, and other peripheral equipment and services, as well as the creation of human interface displays, to be managed from a single database.

It also retains existing Diasys series features, including the flexibility and expandability necessary to tailor it to any kind of plant.