Surge Suppression Tutorial
Surge Suppression Tutorial
Surge Suppression Tutorial
1, JANUARY/FEBRUARY 2007
AbstractIndustrial facilities are becoming more and more protect their equipment from surges, users are installing surge-
dependent on computer control of their processes, and as a con- protection devices (SPDs) either at the main circuit breaker
sequence, require an increase in cleanliness and reliability of for the equipment or the branch circuit breaker depending on
the electrical power supply system. Electromechanical subsys- equipment ratings. There are several SPDs available, utilizing
tems are being replaced by electronic logic. Harmonic interference, different overvoltage-protection technologies and topologies.
welding, variable speed drives, and other in plant noise have The commercially available SPDs significantly differ in terms
reliable mitigation procedures. However, lightning and other
external sourced power disturbances rank high on the list of
of their surge handling capabilities and the level of protection
uncontrollable events that have shut down facilities in recent they provide. Field experience has revealed serious safety issues
years. This paper provides an overview of the causes of power-line related to the SPD operation, particularly during its end-of-life
surges and their consequences for an industrial plant. The relevant situation.
international surge-protection standards will be briefly reviewed,
Power surges can cause failure, permanent degradation, or
and their differences will be analyzed. Different technologies uti-
lized in the implementation of various commercially available temporary malfunction of electronic devices and systems. The
surge-protection devices will be presented, followed by a compar- development of an effective SPD is of paramount importance
ative analysis. Finally, the latest trends and the most promising to manufacturers and users of industrial electronic equipment.
technologies in surge-protection systems as well as their ability Electrical surges have been studied since the 1960s [1]; how-
to overcome the problems associated with conventional protection ever, during the last decade, the issue of surge protection for
devices will be overviewed, and experimental data based on field electronic equipment is receiving more attention. Semiconductor
trials are reported. integrated circuits are much more vulnerable to failure by
Index TermsLightning protection, overvoltage protection,
overstresses compared to earlier electronic circuits.
surge protection.
Modern semiconductor technology has been widely used
I. I NTRODUCTION in many industrial applications. Industrial control systems,
variable-speed drives (VSDs), electronic measurement and
T HE TERM surge is used to describe a transient overvolt-
age on a power line that has a duration of a few microsec-
process control systems are only a few examples where in-
tegrated circuits (electronic switches, power-line carriers, mi-
onds. A transient overvoltage can exceed the insulation rating crocontrollers, memory chips, etc.) are now extensively used,
of electrical equipment causing degradation of insulation and replacing older technologies. These systems provide a better
immediate damage to the equipment. Relatively low-amplitude performance while offering additional features to the user. On
transient overvoltages applied repetitively on the equipment the other hand, these systems can be damaged from power
will reduce its mean time before failure. The result will be surges, causing partial or complete disruption of an industrial
that equipment will have to be repaired more often, increasing process, eventually leading to increased maintenance costs and
operating costs. loss of revenue due to discontinuation of the process. The
Every piece of electronic equipment found in an industrial oil and gas industry is a heavy user of sensitive electronic
environment is subjected to power surges generated on the equipment; thus, the use of surge protection is of paramount
utility grid either inside or outside of the plant and are trans- importance.
mitted to the equipment via incoming power lines. In order to Almost all manufacturers of industrial-type SPDs use metal
Paper PID-06-14, presented at the 2005 IEEE Petroleum and Chemical oxide varistors (MOVs) in their design. MOVs are composed of
Industry Technical Conference, Denver, CO, September 1214, and approved a thin disk wafer of material (metaloxide) that has a known
for publication in the IEEE T RANS ACTIONS ON I NDUSTRY APPLICAT IONS voltage breakdown characteristic. At low voltages, the MOV
by the Petroleum and Chemical Industry Committee of the IEEE Industry conducts very little current (microamperes). As the voltage
Applications Society. Manuscript submitted for review September 15, 2005 and
released for publication September 22, 2006. approaches breakdown, the MOV then begins to conduct current.
K.Samaras and A. Koulaxouzidis are with Raycap Corporation, 151 24 At voltages slightly above the break down, large currents flow,
Athens, Greece (e-mail: ksamaras@raycap.gr). effectively clamping the output voltage. This clamping feature
C. Sandberg is with Shell E&P, Palo Alto, CA 94303 USA (e-mail: allows the higher voltage levels to be shunted to ground,
chet.sandberg@shell.com).
C. J. Salmas is with the Schlumberger Edmonton Product Center, Edmonton, preventing overvoltages on equipment. Figs. 1 and 2 show the
AB T6B 2W9, Canada (e-mail: csalmas@slb.com). voltage waveform before and after an ideal SPD.
Color versions of one or more of the figures in this paper are available online
at http:iieeexplore.ieee.org. This paper describes in brief the power-line surges and their
Digital Object Identifier 10.1 109/TIA.2006.887994 impact on industrial facilities with concentration on gas and
TABLE I
E QUAT IONS FOR S T ANDARD S URGE T EST W AVEFORMS
for 7 h. The short-circuit current is not limited; therefore, the problem, SPD manufacturers combine several SAD compo-
full available short-circuit current can pass through the SPD nents in order to equally share the energy of a surge event within
device. The test is considered successful if the SPD becomes the rated parameters of the SAD device. However, installations
disconnected from the ac supply by an overcurrent disconnection in locations, where frequent as well as high energy transients
device, preventing a catastrophic failure of the SPD. occur, have revealed the inability of SAD-type SPDs to with-
In 2005, UL revised this standard after receiving reports stand high energy transients without failing, while effectively
on catastrophic failure of UL listed or recognized SPD products. protecting the equipment.
The revised version of UL 1449 2nd edition standard becomes
MOV-type surge suppressors can withstand high transient
effective in February 2007. This revised standard extends the
surges, at the same time maintaining sufficiently low clamping
current range of the abnormal overvoltage testing to include
voltages to protect the equipment. For this reason, MOV-based
not only the low short-circuit current range (up to 5 A) and
SPD systems are considered to be the most effective protection
the high short-circuit current range (from 25000 up to 200 000
technology for industrial applications.
A), but also to include intermediate short-circuit currents (100,
500, and 1000 A). All UL listed or recognized SPDs sold in the There are two types of MOV-based SPDs available for
market must meet these revised safety requirements of the new industrial environments. The first one utilizes a combina-
UL 1449 2nd edition standard. tion of parallel MOVs, while the second type uses a single
MOV disk.
The first type uses commercial-type small-diameter MOVs,
which are primarily designed to protect individual electronic
IV. O VERVIEW OF SPD T ECHNOLOGIES PCBs. Individual commercial-type MOVs do not have the
A. SPD Technologies required energy handling capability to protect an electronic
equipment from intense surges. They typically consist of an
There are three basic types of components: the gas discharge MOV disk with a diameter of up to 20 mm coated with resin
tube (GDT), the silicon avalanche diode (SAD), and the to prevent moisture ingress, which deteriorates the performance
MOV. These components have significant differences in terms and shortens the life of the product. To overcome this problem,
of the principle of operation, the performance characteristics, several MOVs are connected in parallel to increase the surge
and the ability to handle high transient currents. In this current capacity of the SPD. The vast majority of SPD manu-
section, we present the main advantages and disadvantages of facturers are using parallel MOV technology. The differences
each of the above technologies with particular focus on between all these products are mainly focused on the diameter
their suitability as surge protectors for low-voltage industrial and the number of the MOVs and the casing. They are designed
control systems. to be installed in power distribution panels (DIN-rail mounted
The GDT uses specially designed electrodes fitted inside devices), or as a stand-alone permanently connected SPD
a tube filled with one or more gases under pressure. They device.
are rugged, relatively inexpensive, and have a small shunt
The application of these devices for protection of industrial
capacitance; therefore, they do not limit the bandwidth of high-
equipment revealed several problems regarding their perfor-
frequency circuits as much as other nonlinear components.
mance and safety which will be described in Section V.
However, there are three major drawbacks that prohibit their
The second type of surge protection is based on the use of a
use in low-voltage industrial applications involving sensitive
single MOV disk capable of adequately handling the energy of
equipment.
the surge event. This is achieved by utilizing an industrial grade
MOV material and by increasing the disk diameter to 80 mm.
1) They can be slow to conduct. The conduction threshold Resin coating has been replaced with an aluminum housing
depends on the rate of change of the transient voltage, which also acts as a heat sink to the MOV. This type of SPD
which is usually in the order of several hundreds of volts. technology will be described in detail in Section VI.
This level of protection is inadequate to prevent damage
in sensitive electronic systems like VSDs.
2) In some situations, they are difficult to turn off after the B. Modes of Protection
transient has ended. This phenomenon is described as the
follow current. The presence of follow current results in A typical single phase configuration of the power service
temporary disconnection of the power to the equipment includes one phase wire and one neutral wire, which sometimes
to be protected for as long as the follow current lasts. is grounded at the service entrance of an installation. There are
three modes of protection.
3) The spark, which is developed between the electrodes in
a GDT, is a violent effect. When the GDT switches from
1) Line-to-neutral (L-N)An SPD module installed between
the insulating state to the conduction state, the high value
the line and the neutral protects the equipment from surges
of dI/dt can cause problems to the equipment close to
originated mainly from disturbances generated on the
the GDT.
distribution grid. It can be caused by capacitor bank
switching, operation of transfer switches, or by the switching
SADs are semiconductor devices that can respond rapidly to on/off of nearby equipment (air conditioners, elevators,
a transient voltage surge. They clamp the transient overvoltage motors, generators, etc.).
at a relatively low residual voltage. On the other hand, they
suffer from low energy withstand capability. To overcome this
SAMARAS et al.: ELECTRICAL SURGE-PROTECTION DEVICES FOR INDUSTRIAL FACILITIESTUTORIAL REVIEW 6
Fig. 18. Power-line surges measured in a 24-h period after installing the
Fig. 17. Power-line transient overvoltages measured in a 24-h period before single-MOV-based SPDs (Site A).
installing single-MOV-based SPD (Site A).