Figure 7. Voltage Transient
+208 Volts rms
-208 Volts rms
0
Amplitude is
typically double
the line voltage
or greater and
less than one
cycle in duration.
+208 Volts rms
-208 Volts rms
+208 Volts rms
-208 Volts rms
Swell
Swell
Normal
Normal
Sag
Sag
PXL Series Installation
and Operation Manual
Instruction Manual
Page 8 Effective: January 2006
4.3 Common Causes of SPD
Problems
4.3.1 Voltage Regulation
4.3.2 Temporary Overvoltage
(TOV)
SPDs are applied to electrical systems to
mitigate surges, transients, impulse or
spikes. By definition, surges are random
high magnitude short-term voltage
disturbances. These high impulses can
cause havoc to electronic devices if no
protection is applied.
- Voltage Transient. This
image represents a transient voltage
surge on the 60 Hz AC sine wave. The
transient is very short in duration but very
high in magnitude from the nominal AC
line voltage. Tests have shown that the
greater the amplitude of the surge
voltage, the greater the risk of damage
occurring to downstream electronic
systems. Additionally, voltage transients
originate from variety of sources,
externally form lightning and utility faults,
and internally generated from switching
loads, electronic power supplies, etc.
Problems associated with voltage
regulation are more commonly
understood since these events happen
over very long time periods. Voltage
surges should not be confused with
voltage regulation problems. By definition,
voltage surges occur in the microsecond
range and voltage regulation is defined as
having a duration of 1 cycle to many
cycles or even hours. Voltage regulation
can only damage an SPD if the voltage
rises near or above its MCOV (maximum
continues operating voltage).
Full detailed explanations can be found in
the IEEE (Institute of Electrical and
Electronics Engineers) publication often
referred to us as the “Emerald Book”.
TOV or swells are 60 Hz voltage events
that can occur from 1 cycle to a few
seconds. See Figure 10 - Line Voltage
Swells (TOV) and Sags. The normal AC
sine wave in reference to the swell and
sag clearly illustrates the difference in the
types of events. TVSS or SPDs are
devices that shunt surge events -
microseconds events. TOV will often last
for cycles and fail MOV-based SPDs.
See Figure 7
4.4 Troubleshooting
The PXL is a rugged suppression device.
In the unlikely case that the indicator
lights change status, audible alarm or
remote alarms are activated. First contact
our Application Engineers at (800) 809-
2772 (option 4, sub-option 2). They will
help determine the cause of your problem
and direct you to the warranty process if
applicable.
Figure 8. Line Voltage Swells (TOV) and Sags
4.4.1 PXL Power System
Troubleshooting Guide
Improper installation of the SPD at site is
the most common application problem.
Please follow these instructions carefully
for proper SPD operation.
Effective 01.06
IM 01005001E
information visit: www.eatonelectrical.com
