Previously, we have discussed about Physical Access Controls, the next issue is related to Environmental Controls. The first concern in data center environmental factor is electrical power. Electrical power is the lifeblood of computer systems. Unstable electrical power supply is the number one threat to consistent operations. At a minimum, the data center should have power conditioners and an uninterruptible power supply. Generally, power failures can be grouped into four distinct categories, based on the duration and relative severity of the failure:

• Total failure (blackout) A complete loss of electrical power, which may span from a single building to an entire geographical area and is often caused by weather conditions (e.g., storm, earthquake) or the inability of an electrical utility company to meet user demands (e.g., during summer months)
• Severely reduced voltage (brownout) The failure of an electrical utility company to supply power within an acceptable range. Such failure places a strain on electronic equipment and may limit their operational life or even cause permanent damage.
• Sags, spikes and surges Temporary and rapid decreases (sags) or increases (spikes and surges) in voltage levels. These anomalies can cause loss of data, data corruption, network transmission errors or physical damage to hardware devices (e.g., hard disks or memory chips).
• Electromagnetic interference (EMI) Caused by electrical storms or noisy electrical equipment (e.g., motors, fluorescent lighting, radio transmitters). This interference may cause computer systems to hang or crash as well as damages similar to those caused by sags, spikes and surges.?

Different types of electrical power conditions and its solution

Emergency Power Shutoff

Electricity is both an advantage and a hazard. The national fire-protection code requires an emergency power off (EPO) switch to be located near the exit door. The purpose of this switch is to kill power to prevent an individual from being electrocuted. The EPO switch is a red button, which should have a plastic cover to prevent accidental activation. The switch can be wired into the fire-control system for automatic power shutoff if the fire-control system releases water or chemicals to disable a fire.

Uninterruptible Power Supply

The uninterruptible power supply (UPS) is an intelligent power monitor coupled with a string of electrical batteries. The UPS constantly monitors electrical power. A UPS can supplement low-voltage conditions by using power stored in the batteries. During a power outage, the UPS will provide a limited amount of battery power to keep the systems running. The duration of this battery power depends on the electrical consumption of the attached equipment. Most UPS units are capable of signaling the computer to automatically shut down before the batteries are completely drained. Larger commercial UPS systems have the ability to signal the electrical standby generator to start.

electrical power for data center

Standby Generator

The standby generator provides auxiliary power whenever commercial power is disrupted. The standby generator can be connected to the UPS for an automated start. The UPS will signal the generator that power is required, and the generator will start warming up. After the generator is warmed up, a transfer circuit will switch the electrical feed from commercial power to the generator power. The UPS will filter the generator power and begin recharging batteries. The standby generator can run for as long as it has fuel. Most standby generators run on diesel fuel or natural gas:

• Diesel generator A diesel generator requires a large fuel-storage tank with at least 12 hours of fuel. Better-prepared organizations will store at least three days worth of fuel and as much as thirty days of fuel. Simple power failures will typically be resolved within three days. Power failures due to storm damage usually take more than one week to resolve. Smart executives would never trust the business to hollow promises from a fuel delivery service. When power stops, attitudes will flare because the business has been shut down. More fuel storage is cheaper than the outage or expense of a court battle with your supplier over late fuel delivery.
• Natural gas generator Natural gas–powered generators have the advantage of tapping a gas utility pipeline directly or using a connection through a storage tank. The natural gas generator does not require a fuel truck to refill its fuel tank. The local natural gas pipeline provides a steady supply of fuel for an extended period of time. The natural gas supply is a good idea in areas that are geologically stable.

Dual Power Leads

The best way to prevent power outages is to install power leads from two different power substations. It would be extremely expensive to just pay someone to run special power cables. Instead, the location of the building housing the computer room should be selected according to area power grids. Power grids are usually divided along highways. Careful location selection will place your building within a quarter-mile of two power grids. This makes the cost of the dual connection affordable. Dual power leads should approach the building from different directions without sharing the same underground trench. A construction backhoe is extremely effective in destroying underground connections.

Power Transfer System

The power transfer system, known as a transfer switch, provides the connection between commercial power and UPS battery power in the generator. The transfer switch may be manual or computerized. It is not uncommon for the power transfer switch to fail during a power outage. Therefore, manual power-transfer procedures should be in place. Automated power-transfer switches may not be able to react to a pair of short power failures occurring within the same 30-minute window. After the first power failure, the generator will come online to produce electrical current. After commercial electrical power is restored, the power switch will transfer back to commercial electricity. At the same time, the generator will receive a signal to begin cooling down and finally shut off. If another power outage occurs during the generator cooling period, the power transfer switch will cycle to generator power while the generator is not producing electrical current. This condition may be resolved by increasing the battery capability of the UPS and adjusting generator start and stop times.

Source:  CISA® Study Guide Second Edition (chapter 7) by David L. Cannon

Picture taken from: digitalrealtytrust

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