Transcript Power Quality and Protection Presentation

Computer Maintenance
Power Quality and Protection
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Copyright © Texas Education Agency, 2011. All rights reserved.
External Power Problems


External power which comes from a home or office
wall outlet, is the power everyone tends to take for
granted; as long as it’s fine.
You may be surprised by the number of problems
external power can have:
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Line noise
Spikes
Surges
Brownouts
Blackouts
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Copyright © Texas Education Agency, 2011. All rights reserved.
External Power Problems
(Continued)
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Most external power problems go unnoticed,
because they are usually small enough that the
computer’s power supply can deal with them (except
for the blackout).
These problems however, can lead to reliability
problems in your computer.
When you plug your computer directly into the wall
socket, you are subjecting your computer to several
problems.
Some of these problems your computer can handle,
but over time, even unnoticed problems can take
their toll and result in major damage
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Copyright © Texas Education Agency, 2011. All rights reserved.
External Power Problems
(Continued)

You should know the kinds of problems that the PC
can experience from external power. These
problems are:

Line noise:
 Consists of small variations in the voltage of the power line.
 A small amount of noise is normal.
 If you have your PC plugged into its own circuit (unshared
line), you should have little trouble from line noise.
 If your computer shares an extension cord with an
appliance (i.e., an air conditioner), line noise will soon
cause some major problems.

The power-regulating circuits in your power supply burn out, and
any line noise passes through to the motherboard or disk drive.
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Copyright © Texas Education Agency, 2011. All rights reserved.
External Power Problems
(Continued)

You should know the kinds of problems that the PC
can experience from external power. These
problems are: (Continued)

Power surges:
 A power spike or over-voltage happens when disturbances
like distant lightning strikes, or other anomalies in the
electrical supply grid, create a voltage spike that travels
down the line and to your wall plugs.
 The surge lasts for only a few thousandths of a second, but
will cause the voltage to increase to 1,000 volts or higher.
 High voltage spikes degrade the power supply. Multiple
surges over time can destroy it.
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Copyright © Texas Education Agency, 2011. All rights reserved.
External Power Problems
(Continued)

You should know the kinds of problems that the PC
can experience from external power. These
problems are: (Continued)

Brownouts:
 Also known as under-voltage, is the opposite of a power
surge and happens when a sudden dip occurs in the power
line voltage.
 It doesn’t last too long, but it can. Usually, the power level
drops below normal levels for a time and then returns to
normal.
 They are extremely common during periods of heavy load
on the electrical system (hot afternoons/cold mornings).
 The reduced voltage level causes many devices to run
slower than normal or malfunction in other ways.
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Copyright © Texas Education Agency, 2011. All rights reserved.
External Power Problems
(Continued)

You should know the kinds of problems that the PC
can experience from external power. These
problems are: (Continued)

Blackouts:
 Occur when the power fails completely.
 Problems caused are usually more frustrating than
damaging.

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NOTE: The fluctuation of power surrounding a blackout can,
however, harm your system.
If you are in the middle of something that is not saved, or
defragging a hard drive when a blackout occurs you will
certainly have problems.
More often the damage occurs when the power returns
suddenly, usually in the form of a huge spike.
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Copyright © Texas Education Agency, 2011. All rights reserved.
External Power Problems
(Continued)

You should know the kinds of problems that the PC
can experience from external power. These
problems are: (Continued)

Lightning strikes:
 This spike delivers a million volts or more if it were to hit a
home or office directly.
 A strike even in your vicinity can result in a very high
voltage spike.
 A lightning strike has been known to completely destroy or
melt down every thing plugged in: computers, copiers, fax
machines, telephones, and more.
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Copyright © Texas Education Agency, 2011. All rights reserved.
Protecting Against Power
Problems
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Several levels of protection exist to protect your
computer from these external power problems.
Two types of damage can be done to the PC by
electrical forces:
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Catastrophic:
 When the device is destroyed all at once in a single event.
Degradation:
 When a device is damaged over a period of instances and
begins to fail or has intermittent problems.
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Copyright © Texas Education Agency, 2011. All rights reserved.
Protecting Against Power
Problems
(Surge Suppressor)
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Most users plug their computers into a power strip or
surge suppressor.
The primary component of a surge suppressor is a
Metal Oxide Varistor (MOV).
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The MOV protects the computer by taking the hit from
voltage spikes.
The problem with MOV is that one big spike or an
accumulation of small surges over time can knock it out.
Some surge suppressors have a light to indicate that the
MOV is still all right.
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Copyright © Texas Education Agency, 2011. All rights reserved.
Protecting Against Power
Problems
(Surge Suppressor)
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A surge suppressor reduces power problems by
absorbing spikes and surges and by smoothing out
line noise (called line conditioning)
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Not all surge suppressors include line conditioning.
Consider two main features when choosing a surge
suppressor:
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Clamping voltage:
 The voltage at which the suppressor begins to protect the
computer.
Clamping speed:
 The time lapse before the protection begins, or how much
time elapses between detection and protection.
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Copyright © Texas Education Agency, 2011. All rights reserved.
Protecting Against Power
Problems
(Surge Suppressor)
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Other things to look for:
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Energy absorption:
 Surge suppressors are rated in Joules, which measures
their capability to absorb energy
 The higher the rating, the better the protection:
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200 Joules is basic protection
400 Joules is good protection
600 Joules is superior protection
Line conditioning:
 Line conditioning capability of surge suppressors are
measured in decibels.
 The more decibels of noise reduction, the better the line
conditioning.
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Copyright © Texas Education Agency, 2011. All rights reserved.
Protecting Against Power
Problems
(Surge Suppressor)

Other things to look for: (Continued)
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Protection indicators:
 An LED indicates you are protected
 If the LED is out, get a new suppressor
Levels of protection:
 Surge suppressors have three levels of protection that
indicate the maximum number of watts the suppressor
allows to pass through to anything plugged into it. The
standard ratings are:
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500 (Good)
400 (Better)
330 (Best)
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Copyright © Texas Education Agency, 2011. All rights reserved.
Protecting Against Power
Problems
(Surge Suppressor)
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Line conditioners filter the power stream to eliminate
line noise.
Because they are usually expensive, few PC users
use a true line conditioner.
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They prefer to purchase this capability in other devices,
such as a surge suppressor.
In the event of an electrical storm or lightning strike,
power can surge up the telephone lines as well as
the power lines.

When installing a surge protector, be sure it has phone line
protection.
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Copyright © Texas Education Agency, 2011. All rights reserved.
Protecting Against Power
Problems (UPS)
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An uninterruptible power supply (UPS)
provides a constant (uninterruptible) power
stream to the computer.
Under normal conditions, it’s a surge
protector that can also handle brownout
conditions.

When the power drops below a certain level or is
disrupted completely, the UPS kicks in and
provides power for a certain number of minutes,
or even hours in some cases.
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Copyright © Texas Education Agency, 2011. All rights reserved.
Protecting Against Power
Problems (UPS) (cont.)
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All UPS units have two sets of circuits:
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One side is the AC circuit that, in effect, is a surge
suppressor.
The other side is the battery and DC to AC
conversion.
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The batteries store a DC charge that must be
converted to AC (because that’s what the PC
expects).
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Copyright © Texas Education Agency, 2011. All rights reserved.
Protecting Against Power
Problems (UPS) (cont.)
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Two types of UPS units are available:
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Standby UPS:
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In-line UPS:
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Operates normally from its AC side.
When the power drops, it switches over to its battery backup side.
Operates normally from its DC or battery backup side.
The AC side is only used in the event of a problem with the batterypowered circuits.
UPS units are often confused with a standby power supply
(SPS), or battery backup, which only supplies power when
none is available and has no power conditioning abilities.
Never plug a laser printer or monitor into a conventional PC
UPS. These devices are not critical to the operation of the PC
and draw tremendous amounts of power at startup.
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Copyright © Texas Education Agency, 2011. All rights reserved.
Summary Slide
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Introduction to external power problems
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Reliability problems
Damage problems
Line noise
Power surges
Brownouts
Blackouts
Lightning strikes
Protecting Against Power Problems
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Catastrophic damage
Degradation damage
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Copyright © Texas Education Agency, 2011. All rights reserved.
Summary Slide
(Continued)
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Protecting Against Power Problems (Surge
Suppressor)
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Metal Oxide Varistor (MOV)
Line conditioning
Clamping voltage
Clamping speed
Energy absorption
Protection indicators
Levels of protection
Phone line protection
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Copyright © Texas Education Agency, 2011. All rights reserved.
Summary Slide
(Continued)
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Protecting Against Power Problems (UPS)
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AC circuit
Battery and DC to AC conversion
Standby UPS
In-line UPS
Standby Power Supply (SPS)
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Copyright © Texas Education Agency, 2011. All rights reserved.