Power quality

The quality of electrical power significantly impacts the performance of sensitive electronic equipment. These guidelines ensure that quality electrical power is provided to your data center.

Most equipment can tolerate some power disturbances or transients. However, large disturbances can cause equipment power failures or errors. Transients can come into the site on the power utility company lines but are often caused by electrical equipment installed in the building. For example, transients can be produced by welders, cranes, motors, induction heaters, elevators, copy machines, and other office equipment. The best way to prevent problems caused by power disturbances is to have transient-producing equipment on a separate power service than the one that supplies power to your information technology equipment.

Ground or earth

When used in reference to electrical power systems, Ground is a conducting connection between an electrical circuit and the earth or some conducting body that serves in place of the earth. The term ground is the most common name used, however it is also referred to as earth or terra in several international geographies. In this topic, these terms and other local language equivalents are interchangeable.

Ground is a critical component of an electrical power distribution system. A properly installed ground system allows for safe operation of equipment that is connected to the electrical power source under normal and electrical or equipment fault conditions. The life safety function of ground and grounding methods is addressed by the appropriate local and national electrical wiring codes. In the United States, this code is known as the National Electric Code or publication 70 of the National Fire Protection Association. Many countries have adopted the National Electric Code or have developed an equivalent code.

The National Electric Code and its equivalents have a primary objective to provide safe operation of electrical power distribution systems and electrical equipment installations. Compliance with these codes does not guarantee efficient operation of equipment connected to the power distribution systems. When sensitive electronic equipment is connected, there are often times when additional ground connections may be required. Typically, additional ground connections are recommended when there is a concern for high frequency or radio frequency (RF) interference, which may impact electronic circuits. These additional ground requirements will be found with the installation documentation for specific equipment. Additional ground requirements may also be recommendations from engineering or data center evaluations, reviews or surveys. Local or national codes allow for these additional grounds to be installed.

Grounding specifications

Every utility branch circuit, whether three or single phase, must contain an insulated equipment-grounding conductor that is separate from the phase and neutral conductors within the branch.

For 200 V AC through 240 V AC installations worldwide, the equipment-grounding conductor must match local electrical codes and must be green with or without one or more yellow stripes on the insulation. It is recommended that the ground wire be the same size as the phase conductor wires.

Conduit must not be used as the only grounding means. However, any conduit or cable shield must be connected at both ends in such a way that it is included in the grounding path, and in parallel with the grounding conductor it contains. Most electrical codes require that branch circuit wiring be located in the metallic conduit, or be made from shielded cable, if located under a raised floor. Even when not required by local regulations, some form of shield around the branch circuit wiring is strongly recommended as a means of reducing coupling of high-frequency electrical noise into signal and control cables.