Masatoshi Noritake

Development of plug and socket-outlet for 400 volts direct current distribution system

This paper reports test results and reviews of the developed DC plug and socket-outlet. The developed item can be applied to the 400 Vdc power to improve energy efficiency in telecommunication sites, data centers, commercial buildings, and smart energy. There are some safety issues to use the 400 Vdc power. The set of plug and socket-outlet has a unique mechanism which based on combination of a permanent magnet and mechanical contact in the limited small space. That should solve the problems such as both arc extinction and protection against electric shock known as critical DC power issue for a long time.

Verification of 380 Vdc distribution system availability based on demonstration tests

In recent years, higher voltage direct current (HVDC) distribution systems have been developed to reduce power consumption in telecommunication buildings and data centers. Thus, a demonstration test has been conducted to determine the energy efficiency, power stability, and safety of the HVDC system. The demonstration test was conducted in an in-service data center. The test results show that the HVDC system is 5.8% more efficient than the existing AC system. It was also found that servers that were altered for HVDC use could reduce the power consumption by up to 7%. According to the results of simulations including the effect of air conditioning, HVDC system could reduce the total power consumption by 15%. These test results also show that the HVDC system has no problem in operation in terms of power stability and safety.

Evaluation results of power supply to ICT equipment using HVDC distribution system

In recent years, Higher Voltage Direct Current (HVDC) distribution systems have been proposed to reduce power consumption in telecommunication buildings and data centers. NTT FACILITIES and NTT Data conducted verification tests of a HVDC distribution system at a Tokyo data center from January 29 to October 30, 2009. This paper summarizes the results of studies on HVDC distribution systems obtained so far, describes verification tests based on those results, and examines the test results. The verification tests were conducted with the cooperation of domestic and international ICT equipment vendors. We measured the energy savings and stability of the power supply involved long-term powering of ICT equipments (servers and storages) with an HVDC system. The test results show the superiority of the HVDC distribution system over the existing AC system. These test results also validate the HVDC system specifications proposed by the NTT group for standardization. These results may develop the current vigorous discussion of international standardization for HVDC distribution systems.

A study of the safety of the DC 400 V distribution system

Recently, higher voltage (here we assume about 400 V DC) direct current (HVDC) distribution systems have been recommended to reduce the power consumption of telecommunications buildings and datacenters. However, safety measures for these systems have not yet been established. There are many potential hazards with electricity, such as electric shocks, burns, and fires. Ventricular fibrillation caused by electric shocks is especially dangerous. Preventing electric shocks is important for any HVDC distribution system. We report the effect of “direct current” and “higher voltage”, characteristics of HVDC systems, on the human body via electric shocks.

Development of energy management system for DC microgrid for office building:-Day Ahead operation scheduling considering weather scenarios-

In recent years, distributed generators (DG) with renewable energy (RE) are introduced to electric power systems for saving CO2 emission. Installation of DGs in user-side leads to the local demand and supply system, called microgrids (MGs). Since the some of DGs work in DC, advantages of DC supply system over the AC might be emphasized The authors are investigating the merits of DC microgrid (DCMG) using the actual DCMG for an office building. Operation of the DCMG is organized by an energy management system (EMS). This paper proposes an optimal scheduling algorithm implemented in the EMS. Simulation using the actual demand data shows that the proposed scheduling algorithm can save 0.3 % CO2 emission during the simulation terms.

Demonstrative research on DC microgrids for office buildings

This paper reports the experimental study of a DC microgrid for an office building that is now being constructed in Obihiro City, Hokkaido, Japan. The objective of this study is to develop a self-sustained distributed energy system by combining distribution energies, batteries, and appliances with DC power. This new DC energy system not only reduces the environment load and improves energy efficiency but also forms a community energy system that can become independent from utility grids and resistant to natural disasters. We have found that compared with AC power supply, the DC system, which uses power generated by solar panels as is, increases the efficiency by 3.2 percent and decreases commercial power to be purchased by 4.2 percent.

Characteristics of 400 V dc plug and socket-outlet for DC distribution systems

This paper reports test results and reviews for the developed plug and socket-outlet applied to the 400 V dc power systems expected to improve energy efficiency in communication sites, data centers, commercial buildings, and smart energy systems. However, there are some safety issues to use 400 V dc power. The plug and socket-outlet has a unique mechanism based on combination of a permanent magnet and mechanical contacts in the limited small space. The mechanism should solve the problems such as both arc extinguishing and protection against electric shock known as critical DC power issue for a long time. The results of an investigation of inrush current also are reported, including current size, effects and testing methods, as one problem in the construction and operation of 400 V dc power distribution circuit.

Development of 400 Vdc plug and socket-outlet for DC distribution system

This paper reports test results and reviews for the developed plug and socket-outlet applied to the 400 Vdc power systems expected to improve energy efficiency in communication sites, data centers, commercial buildings, and smart energy systems. However, there are some safety issues to use 400 Vdc power. The plug and socket outlet has a unique mechanism based on combination of a permanent magnet and mechanical contacts in the limited small space. The mechanism should solve the problems such as both arc extinguishing and protection against electric shock known as critical DC power issue for a long time.

Consideration of inrush current on DC distribution system

In recent years, 380Vdc distribution systems have been expected to be one of the energy saving solutions for telecommunication buildings and data centers. However, DC distribution systems have various problems. In this paper, We report the results of an investigation of inrush current, including current size, effects and testing methods, as one problem in the construction and operation of 380Vdc power distribution circuit.

Overcurrent protection for high voltage direct current (HVDC) distribution systems

A consideration of short-circuit protection in high voltage direct current (HVDC) distribution system is written in this paper. There are some types of energy sources in HVDC system, and the behavior of short-circuit current is affected by the way to rectify. Therefore, it may be more complicated to protect short-circuit in HVDC system than it is in AC system. In this study, a protection technique that can apply to HVDC system using a MCCB (Molded case circuit breaker) as a protection device is reported.