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Question 19/5 – Power feeding systems
(New Question)


SG5 is responsible for studying ICT environmental aspects on electromagnetic phenomena and climate change. In addition, SG5 has been appointed as a lead Study Group to advance the work on ICT and Climate Change.

Along with the wide spread use of the Internet, a great deal of ICT equipment, such as routers, servers, and switches, has been installed in telecommunication centres to enable high-speed and large-scale broadband services. A DC power feeding system is commonly used inside a telecommunication centre or a Data centre because the power efficiency is higher than that for an AC power feeding system due fewer converters.

The power consumption per rack of conventional (legacy-type) equipment such as exchanges or transmission devices is about 2 kW. On the other hand, that for ICT equipment, such as routers and servers has reached over 7 kW. Therefore, the feeding current is over a hundred amperes when we use a 48Vdc power feeding system to supply power to ICT equipment. Moreover, the feeding cable must have sufficient capacity for the current, so the diameter of the cable becomes large. This situation has several disadvantages such as length limitation, voltage drop caused by cable resistance, heavy weight, and inflexibility.

However, power feeding systems in telecommunication centers, for example, are not specified in International standards. Along with the increase in energy consumption of the devices, energy efficiency of the feeding system is also an important factor in reducing the CO2 produced by ICT systems. Moreover, these disadvantages may lead to the use of many materials, such as copper and plastics, and may require significant consumption of energy to construct those systems.

Therefore, it is important to consider not only the energy consumption of the telecommunication devices, but also the validity of the energy supply to the equipment.

This work directly and indirectly contributes to a reduction in the environmental impact of ICTs, e.g., CO2 and material use.


This Question mainly focuses on the energy efficiency of the power feeding systems that are used in telecommunication networks or customer buildings. To achieve higher energy efficiency, this Question will prepare methodologies for evaluating the energy efficiency of power feeding systems including AC and DC systems, specifications on power feeding systems, safety issues for devices and service personnel, and methods for constructing an earthing and bonding system. One of the key issues is characterization of a Higher Voltage DC power feeding system, the voltage for which is around 400 V. The Higher Voltage DC power feeding system is a topic of great interest around the world because of its ability to improve the energy efficiency of the power feeding system. The standardization of its specifications is very important to promote the development of the system and improve the validity of the energy supply to the ICT system.

Study items to be considered include, but are not limited to:

  • Specification of the power feeding systems, especially for the Higher Voltage DC systems
  • Nominal voltage, operation voltage range, abnormal voltage range under fault condition, etc.
  • Safety criteria and requirements for service personnel and equipment.
      1) Protection (blocking) devices such as fuses, breakers, etc.
      2) Basic principle for safety and working practices,
      3) Requirements and criteria for protecting service personnel and apparatuses under normal and abnormal operating conditions.
  • System configuration and specification of the power feeding system
      1) Earthing and bonding system of the power feeding system
      2) Cable distribution method, basic concept (or architecture) of the power supply network
  • Methodologies for evaluating various power feeding systems such as the conventional DC system, AC system provided by commercial power networks, and Higher Voltage DC system
      1) Methods for evaluating performance of the system
      2) Calculation (or estimation) method for obtaining environmental effect of the system, validity of the energy supply system to the ICT equipment, etc
The work under this question could provide the basis for L-series Recommendations on power feeding systems.


Tasks include, but are not limited to:

  • A new Recommendation on the characterizations and specifications of the power feeding system, especially for the Higher Voltage DC system.
  • A new Recommendation on safety for humans and equipment of the power feeding system.
  • A new Recommendation on the system configuration, architecture, and cable distribution including feeding, lightning protection, EMC, earthing, and bonding of the power feeding system.
  • A new recommendation on methodologies for evaluating the performance of energy feeding and its environmental impact.



  • K-series


  • 1, 4, 6, 8, 11, 12, 14, 17, and 18/5

Study Groups:

  • ITU-T SGs 9, 13, 15, and 16

Standardization bodies:



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Updated : 2009-06-12