Understanding Standby Power

The Standby Power systems we supply are used to support mainstream IT and communications infrastructures from the home office to the international Data Centre.

When mains power goes off, the Standby Power system will operate either by generating power from fuel or by using stored power. Most often, generated power comes from a diesel generator, and stored power from a UPS with lead-acid batteries. But there are lots of options. Generators can also be powered by natural gas or petrol, (or aviation fuel, if it's a gas turbine), or hydrogen in the case of Fuel Cells. Stored power can also come from NiCad batteries and flywheel systems.

Before conventional generators reach operating power, there's a delay. Modern electronic equipment is susceptible to even momentary power loss. For that reason a conventional generator, on its own, is insufficient to support a computer-based system. The 'typical' Standby Power system for a computer room incorporates both a battery-powered UPS (to bridge the gap whilst the generator starts) and a diesel generator to provide the extended runtime that may be required.

Of course 'typical' Standby Power installations rarely exist, and we're often called upon to configure solutions where noise, or weight, or footprint, or heat output, or exhaust fumes (or lots of other things) would cause a problem.

Power Quality Issues

A loss of power, even momentarily, can cause IT systems and sensitive equipment to crash. A UPS maintains power by switching instantaneously to batteries in the event of a power failure, or even just a dip in power (a brownout). They also condition the power supply to reduce unwanted spikes and harmonics. They are designed to correct a variety of power problems, such as:

1. Power failure - The total loss of power. Causes electrical equipment to stop working.

2. Sags - Transient under voltage, can be caused by switching of heavy loads such as air conditioning or industrial machinery. Can cause IT hardware to lock-up, fail or re-boot.

3. Surges - Relatively short duration (from milliseconds to seconds) of high voltage. Power surges could be caused by the shut-down of a generator or other industrial motor on the local supply circuit. Will cause systems to crash, can cause components to wear and degrade over extended periods.

4. Brownouts - Under voltage for an extended period of time (milliseconds to seconds, minutes, hours or days). Will cause overheating in motors. Prolonged and frequent brownouts cause equipment to malfunction or not work at all.

5. Spikes - Very brief, but high energy bursts (lasting only a few milliseconds). Spikes are typically caused by lightning or malfunctions in the power supply. Will damage sensitive solid-state components and destroy data in digital equipment.

6. Line noise - Distortions superimposed on the power waveform. Causes electro magnetic interference.

7. Frequency variation - Deviation from the nominal frequency. Causes motors to increase or decrease speed.

8. Switching transient - Instantaneous under voltage. May cause erratic behaviour in some equipment: memory loss, data error, data loss and component stress.

9. Harmonic distortion - Multiples of power frequency superimposed on the power waveform. Causes excess heating in wiring and fuses.

Selecting the right UPS

• For non-critical applications, an off-line UPS will normally resolve Power Quality Issues 1. to 3. above.
• Higher level power protection, resolving Issues 1. to 5. above, will require a line interactive UPS.
• Complete protection for mission critical systems, resolving all the Issues in 1. to 9. above, will require on-line double conversion UPS technology.

For an overview of the different technologies, see UPS Technologies.

Some UPS allow a controlled shut-down of IT servers whilst others may be used in conjunction with another Standby Power source (such as additional batteries, a generator or fuel cell) to allow all or part of the facility to continue operating for very significant periods.

Your need, when the power fails:

Below, we've listed some scenarios along with possible solutions. Please scroll through to find a question that applies to you - please click on the links to show possible solutions.

Just enough up-time to shut my servers down cleanly

Two or three hours should bridge most supply interruptions

Constant ongoing power, with no break and high reliability

Constant ongoing power, with no break and very high reliability. No power-downs permitted, even for preventative maintenance.

All my equipment will tolerate a 30 second break but I'd like to get started again quickly

I need long runtimes and no break, but I'm on the 14th floor with nowhere to put a generator