Czech Embassy in Tokyo
Shibuya is most probably the busiest district in Tokyo with many department stores, restaurants, bars, and music clubs. It is also the place where the Czech Embassy together with the Czech Centre are located. The Czech Centre is a government-funded institution which opens a dialogue with Japanese public and media, and represents the Czech Republic in Japan. It organises activities and events focused on Japanese public, supports exchange projects, and cooperates with renowned cultural institutions across the country. In 2010, architect Jaroslav Kačer created the project for reconstruction of the building, part of which are also building technologies. Domat Control System won the contract for the turnkey supply of the building control system.
There is 26 air handling units in the building, from those supplying offices and exhibition rooms to exhausts from technical rooms. The fans are mostly controlled by variable speed drives according to air quality or to a constant value depending on the operation mode. In the air ducts there are more than 140 fire dampers which are monitored and displayed in the SCADA. Heating and cooling is provided by a system of 16 heat pumps, connected in groups: three outdoor units for apartments, and one for the embassy and the Czech centre each. The domestic hot water is heated by two boosters, which are heat pumps in principle. The boosters are independent units communicating with the control system over analogue and digital signals.
The control system is installed in 8 panels interconnected in an industrial Ethernet network. In the control room there is a PC with RcWare Vision SCADA software. This means that the system topology is a standard one, like at other similar sites. Twenty six water meters are integrated over M-Bus together with 39 power meters for consumption metering in apartments in 2nd to 5th floors. The M-Bus to RS232 converter is connected to the network over a RS232/Ethernet terminal server.
What is definitely worth noticing is the power grid system in Japan: for historic reasons, the norteastern part of the country uses 50 Hz frequency while the western part operates with 60 Hz. This bifurcated power system is a holdover from the 19th century when local power distributors, working with DC current, moved into AC. Some of them imported the equipment from what later became AEG, using 50 Hz, while local power providers in Osaka brought in 60 Hz generators from the United States, supplied by the predecessor of General Electric Company. The grids grew, with 60-Hz power generation emanating from Osaka and 50 Hz electricity spreading out from Tokyo, until eventually the entire country was wired. The frequency frontier is delineated by the Fujigawa and Itoigawa rivers. A very important part of the infrastructure are frequency converter stations which enable connecting the two systems together and increase grid stability. Nowadays, three stations operate with combined capacity of about 1 GW, and works are in progress to increase the capacity.
Tokio itself uses two separate power grids, apparently for the sake of higher power safety in case of blackouts and natural disasters. One of them, Power, is used for power appliances, operating with three-phase 200 V / 50 Hz current with interesting connection where one phase represents the neutral line at the same time. Line-to-line voltage and line-to-ground voltage are thus the same, 200 V. In the panels there are three phase conductors plus PE. The second network is called Light – for illumination – with one-phase 100 V / 50 Hz power, using 1 phase conductor + N + PE. The control panels had to be designed accordingly together with power supply for the control system. For the Domat engineers, it was a very interesting experience not only from the technical point of view, but also because they learned about everyday life in Japan.