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Electrical Noise - People most commonly
associate electrical noise with interference that can be
seen on your TV or heard as static on your AM/FM or HAM radio.
You'vet probably
experienced watching
TV when someone in the kitchen started using a blender or
mixer. The TV screen became "snowy" and the audio portion
developed static. This particular problem is easy to identify.
Unfortunately, many
of the things that can cause electrical noise are out
of site. Actually, almost anything that uses electricity
can cause electrical noise that produces the symptoms
of audio or video interference (i.e., a flourescent light
could have a faulty ballast, a motor may have a loose
connection, a furnace may have a faulty control, etc.).
The sources for interference can come from inside your
home, your neighbor's home, or somewhere on the electric
utilitiy's system.
Another type of electrical
noise is the kind which disrupts data lines and affects
performance of electronic equipment. It is generally not
heard or seen but is characterized by the presence of
unwanted low level electrical signals on the power line.
Electrical noise of this type can be caused by bad grounding
or picked up from nearby equipment (walkie-talkies, cell
phones, arcing devices, etc.). It is especially likely
to occur if there is an inadequate or improper equipment
ground or when an equipment cable is unshielded or improperly
terminated. Although not as harmful as transients, noise
can cause performance problems and data disruptions in
electronic equipment.
- Flicker - Voltage variation large
enough and long enough that it can be seen as a change in
electric light source intensity. It usually results from adding
and removing large power loads, like spot welding and starting
motors. If the voltage variation is severe, it may cause problems
with sensitive loads.
- Harmonics - Harmonics are primarily
the result of the today's modern electronic equipment. Today's
electronics are designed to draw current in "pulses" rather
than in a smooth, sinusoidal manner as older, non-electronic
equipment did. These pulses cause distorted current waveshapes,
which in turn cause distortion of the voltage. Current and
voltage harmonics can cause such problems as excessive heating
of wiring, connections, motors, and transformers and can cause
inadvertent tripping of circuit breakers.
- Outages - These are the longer term
events (several seconds to hours) caused by external factors
such as trees, car accidents, animals in contact with lines,
operation of utility protective equipment, and weather conditions.
Interruptions and long-term outages can cause costly lost
production time.
- Voltage Sags - Sags are momentary (typically
a few milliseconds to a few seconds duration) under-voltage
conditions and can be caused by a large load starting up (such
as a air conditioning compressor or large motor load) or operation
of utility protection equipment. Sags often appear as flickering
lights and can cause equipment shutdown. A sag of just a few
milliseconds can mean a complete blackout to some sensitive
equipment.
- Voltage Swells - Swells are momentary
(typically a few milliseconds to a few seconds duration) over-voltage
conditions which can be caused by such things as a sudden
decrease in electrical load or a short circuit occurring on
electrical conductors. Voltage swells can affect the performance
of sensitive electronic equipment, cause data errors, produce
equipment shutdowns, and may cause equipment damage.
- Voltage Transients - A transient
(sometimes called impulse) is an extremely fast disturbance
(millionths of a second to a few milliseconds) evidenced by
a sharp change in voltage. Transients can occur on your electric,
phone, or even cable TV lines. They can be caused by such
things as lightning, trees falling on power lines, ice and
snow, and cycling equipment ON and OFF. Transients can originate
from inside or outside your home. Equipment, such as air conditioning,
pump motors, photocopiers, and even electric hand tools can
all cause transients when cycled on and off. These impulses
are similar to lightning strikes but are much smaller. However,
because they can occur frequently, they can slowly cause electronic
equipment to break down.
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