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There are many types of power problems.

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Computer glitches, lockups and hardware damage can be the result of poor power quality. Different types of problems will have different effects on the operation, or even life expectancy of equipment. Spikes, Dropouts, Power Failure or Blackout, Power sag or surge, High frequency noise, Normal and/or Common mode noise are all quality problems that affect the quality of the AC power being supplied. Knowing what these problems are, and what some of the consequences are of having these problems, can help in the process of identifying what can be done to help protect equipment. Some are caused by Lightning, Electrostatic Discharges, Ground Surges and Faulty wiring. With the explosion of computer network technology, computer systems are also susceptible to network and phone line surges, as well as the various power supply surges .

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The spike is a surge of energy superimposed on the AC line, generally of short duration. Spikes can potentially have the most serious effects on electronic equipment due to their high energy content, and the Integrated Circuits inability to absorb the energy. Many events can cause spikes, such as lightning bolts, utility grid switching, switching inductive loads on and off, and SCR (Silicon Control Rectifier) dimmers. Although properly designed equipment has some built-in spike protection, repeated hits by high energy spikes can eventually render these components useless.

Spike and Surge Protectors

By far the least expensive type of power protection, spike and surge protectors  act by cutting off voltage when it exceeds a certain level and sending it to ground.  They are relatively inexpensive, however the MOVs inside them do degrade over time. Portable units may be used to protect specific equipment but switch board mounted units offer protection to the whole facility.

A power failure is similar to a computer locking up. This will cause some frustration but generally no major problem. However if a spike damages a hard disk and the information on it is lost, this situation is a lot more serious. These surge suppressors guard against this.

This wiring diagram depicts surge protection being used in a building.

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Power Line Filters

Power line filters are designed to suppress spikes, surges, and noise before they get to the clipping level of surge protectors. Instead of clamping the voltage when it exceeds the cutoff, the power line filter limits noise and spikes to a safe level by slowing down the rate of change of these problems, thereby keeping electronic systems safer than the surge protectors can. Of course, these filters are more expansive.

Let us install the power quality equipment you need to protect your electronic equipment, including data and phone lines.

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This is where a portion of the sine wave has a lower than expected value or is missing entirely, usually for a portion of a cycle. These types of problems can be caused when large motors are started, spot welders are operated, lightning arresters conduct (during a lightning hit), or when electrical equipment fails. Dropouts can lead to failures in computers and electronic equipment , reduced life of motors and flickering lights.

Power Failure

When the duration of a dropout exceeds 1 cycle it is usually referred to as a Power Failure, or Blackout. This problem is usually the easiest to recognise.

Sag or Brownout

A power sag (or low line voltage) is a decrease in line voltage of at least 10% of the average line voltage for half a cycle or longer. The power sag is often caused by large inductive equipment, e.g. photocopy, bank of fluorescent lights. Sags can be caused by external factors as well, such as large power draining equipment used in other buildings. Sags can be particularly detrimental to electronic equipment because of the malfunctions caused by the sudden decrease of available voltage to the power supply. Relays and solenoids can chatter generating spikes (see above). Complete failure rarely occurs, however equipment lockup or lockout can occur requiring a resetting process. Often  equipment continues to operate, with the user, unaware of any problems that may have occurred.


A power surge is the opposite of a sag and is often referred to as "High Line Voltage". A surge is defined as an increase in line voltage above 253 volts (on a 230V Line) for a half cycle or longer. Like the sag, the power surge is often caused by large inductive loads being applied on the same line. Power surges can cause some of the most dangerous situations, and their resulting damage is most difficult to repair.

Uninterrupted Power Supplies (UPS)

These are the most complete power protection devices available. They operate by providing continuous, uninterrupted AC power from an isolated, regulated source regardless of the quality of the primary AC line. These power supplies are constantly supplying the system with clean AC power. Small UPSs contain built-in batteries which supply the system with DC power when a complete power failure occurs. Larger units use an external battery allowing for orderly shutdown of all systems during a power failure, or for activating backup generators. All UPSs provide very significant protection against all power problems, the better models approaching absolute protection.

Standby Power Supplies

These units differ from Uninterrupted Power Supplies in that the AC power is connected through a power line filter to the computer system. The SPS only begins to supply the computer with clean AC power when it senses a voltage interruption. These SPSs are less expensive than UPSs, however, for most small systems they can be used in place of a UPS and still gain similar benefits. The reason for this is that it takes only a few milliseconds for an SPS to switch to the alternate AC source, and most small systems do not notice this short gap without power.