Specifications

T4.44
GE Power Controls
Comfort Functions
SurgeGuard
Surge arresters
Introduction
In order to protect any type of electric or electronic
equipment such as TV’s, PLC’s, computers, or even
entire electrical installations against destructive
overvoltage surges, the installer will nowadays use
Surge Arr
esters or Surge Protection Devices
(SPD’s.)
Besides the trivial benefit of protecting the
installation and the equipment against destructive
overvoltage surges, the benefits indicated below are
less obvious but most certainly more important:
- Avoid downtime; this secondary effect on a
business may be much greater than just the cost
of the PCB which was destroyed by the surge;
- Avoid equipment lifetime reduction by avoiding
degradation of internal components due to long
term exposure to low level transients;
- Avoid disruption or malfunction; although no
physical damage is apparent, surges often upset
the logic of microprocessor-based systems
causing unexplained data loss, data and software
corruption, system crashes and lock-ups.
When comparing the cost of installing SPD’s with the
downtime cost and the cost of repairing an electrical
installation and to replace all hooked-up equipment
after a serious surge has "visited", there is no further
justification needed and the need to install SPD’s,
even in the smallest installation, becomes obvious.
Background
Disturbances
Table 1 summarises the different disturbances
causing different problems while propagating in an
electrical energy-distribution system.
Besides devices used to suppress overvoltage
transients, typically characterised by a very big
magnitude (1000’s of volts) and very short duration
(microseconds), devices for noise filtration (low
voltage, low energy, random) are also offered.
Origin of Surges
The most commonly known "field"-surge generators
are listed below:
- Electronic dimmers based on the phase-cut principle
- Motors and transformers. At startup, they are a
real short-circuit, generating a very high inrush-
current
- Welding machines
- Lightning strikes, both direct or indirect
(inductively coupled)
- Power-grid-switching by the energy-supplier.
Voltage-generation mechanism
As all surge originators are currents, the mechanism
that translates this current into a voltage is:
U = -L x (di/dt) in which:
- U = generated voltage,
- L = inductance of the conductor in which the
current is flowing,
- di = the change in current,
- dt = the time in which the current-change di took place.
As the change in current is very high, while the duration
is very short, even with a low conductor inductance,
the result of L x (di/dt) can become astronomical.
T4
Description
A planned or accidental loss
of power in a localized area
of community
A decrease (sag) or increase
(swell) in voltage
A sudden change in voltage
up to several thousand volts
(also called an impulse, spike
or surge)
An unwanted electrical signal
of high frequency from other
equipment
A distortion in the voltage due
to the power supplies in some
equipment
Problem
Temporary interruption/long-term outage
Sag/swell
Transient
Noise
Harmonic distorsion
Cause
Equipment failure, weather, animals,
human error (auto, accidents, etc)
Major equipment start-up or
shutdown, short-circuits (faults),
undersized electrical circuits
Utility switching operations, starting and
stopping of heavy equipment or office
machinery, elevators, welding equipment,
static discharges, lightning and storms
Interference from appliances, microwave
and radar transmissions, radio and tv
broadcasts, arc welding, heaters, laser
printers, loose wiring and improper
grounding
Power supplies in computers, adjustable
speed drives, and fluorescent lighting
Effect
Systems shut down
Memory loss, data
errors, dim or bright
lights, shrinking display
screens, equipment
shutdown
Processing errors, data
loss, burried circuit
boards or other
equipment damage
Noise disturbs sensitive
electronic equipment, but
is usually not destructive
(can cause processing
errors and data loss)
Overheating of motors,
transformers, and wiring
Duration
Temporary: less than 1 minute
Long-term: more than 1 minute
From milliseconds to a few
seconds
Microseconds
Sporadic
Sporadic
Disturbances in an electrical energy distribution system (table 1)