Specifications

V-I characteristics
T4.46
GE Power Controls
Comfort Functions
SPD-technology
Table 3 shows the various technologies that can
be applied to protect an installation or equipment
against overvoltages. Their respective main
characteristics are also shown. To protect a mains-
power distribution system from overvoltage surges, only
Zinc-Oxide-Varistor (or more in general the Metal-
Oxide-Varistor, in short the MOV), Gas-Tube and Spark-
Gap technologies are used.
SurgeGuard SPD’s
Class 2 SurgeGuard devices all have MOV-
technology inside. Besides the MOV’s, each phase
is also equipped with a thermal fuse in order to take
the device of-line in case the MOV breaks down and
becomes a short-circuit (i.e. after thermal runaway).
In addition, all devices have an optical fault-
indicator and some have a voltage-free contact for
distant reporting. This contact reflects the status of
the thermal fuse, and thus indirectly also the status
of the MOV. Once the indicator turns red or the
contact has switched over, the SurgeGuard should
be replaced as soon as possible.
The class 1 SurgeGuard devices are based on
spark-gap technology. As a spark gap can never
turn into a short-circuit, the class 1 devices don’t
have a thermal fuse and as a consequence neither
an auxiliary contact nor an optical status indicator.
T4
Device
type
Ideal device
Zinc oxide
varistor
Zener
Growbar
(zener + SCR
Combination)
Spark
gap
Triggered
spark
gap
Selenium
Silicon
carbide
varistor
Leak-
age
Zero
to
low
Low
Low
Low
Zero
Zero
Very
high
High
Follow
on I
No
No
No
Yes
(latching
Holdin I)
Yes
Yes
No
No
Clamping
voltage
Low
Moderate
to
low
Low
Low
High
ignition
voltage
Low clamp
Lower
ignition
voltage
Low clamp
Moderate
to
high
High
Energy
capability
High
High
Low
Medium
High
High
Moderate
to
high
High
Capacitance
Low
or
high
Moderate
to
high
Low
Low
Low
Low
High
High
Cost
Low
Low
High
Moderate
Low
to
high
High
High
Relative
low
Response
time
Fast
Fast
Fast
Fast
Slow
Moderate
Fast
Fast
Characteristics and features of transient voltage suppression technology (table 3)