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Eaton’s Guide toSurge SuppressionProduct Focus

What You Need to KnowAbout Surge ProtectionDevices



Eaton’s Guide to Surge Suppression:What You Need to Know About Surge Protection Devices

Table of ContentsSummary of Applicable UL and IEEE Standards

for Surge Protection Devices . . . . . . . . . . . . . . . . . . . . . . . . 2High Resistance Grounding and Wye or Delta

Surge Protection Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Surge Current per Phase (Industry Denition). . . . . . . . . . . . . 8Facility-Wide Surge Suppression . . . . . . . . . . . . . . . . . . . . . . . 9Debunking the Surge Current Myth,

“Why Excessive Surge Current Ratings are not Required” . . . 10Surge Arrestor vs. Surge Suppressor . . . . . . . . . . . . . . . . . . . 12Benets of Hybrid Filtering in Surge Protection Devices. . . . . 14Factory Automation (PLCs) and Their Need for

Surge Suppression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Surge Protection Devices with Replaceable Modules. . . . . . . 17Why Silicon Avalanche Diodes are Not Recommendedfor AC Powerline Suppressors . . . . . . . . . . . . . . . . . . . . . . . 18

Surge Protective Device Frequently Asked Questions . . . . . . 20

Why Eaton?As a premier diversied industrial manufacturer, Eaton Corporationmeets your electrical challenges with advanced electrical controland power distribution products, industrial automation, world-classmanufacturing, and global engineering services and support.Customer-driven solutions come in the form of industry-preferredproduct brands such as Cutler-Hammer , MEM , Holec ,Heinemann Powerware and Innovative Technology .

Eaton has an extensive family of Surge Protective Devices (SPD) forany facility or application. Using our Cutler-Hammer, Powerware andInnovative Technology branded products will ensure that the qualityof power required to maximize productivity in today’s competitiveenvironment will be supplied in the most reliable, safe and cost-effective manner. Eaton has developed specic surge protectionsolutions for commercial, industrial, institutional, telecommunication,military, medical and residential applications — both for NorthAmerica and throughout the world.

Cutler-HammerEaton’s Cutler-Hammer SPDs are designed to be fully integrated intonew switchgear and new panels for the closest possible electricalconnection. When installing a surge suppressor, it is important tomount it as close to the electrical equipment as possible in order tokeep the wiring (lead length) between the electrical equipment and

In addition to the extensive integrated SPD offeCutler-Hammer SPD product line includes a wisurge current ratings, monitoring features and eoptions. The Cutler-Hammer SPDs are availableCutler-Hammer electrical wholesalers.

For information on Eaton’s Cutler-Hammer SPDplease visit www.eaton.com/tvss.

PowerwareLightning and other transient voltage and curreena are harmful to most UPS equipment and element connected to the UPS. For example, the trthe critical load via an unwanted activation of aswitch bypass path around a UPS. Therepractice that both the input circui t to the UPS UPS bypass circuits (including the manual mcircuit) be equipped with effective Category “device, as specied in IEEE Std. C62.41-199connections should be employed for this protIEEE RECOMMENDED DESIGN/INSTALLA1100-1999.

Eaton's Powerware surge protective devices caninto Power Distribution Units (PDUs) and are ddemanding needs of the same mission-critical aties that utilize Powerware Uninterruptible PowPowerware surge protection devices are availabof surge current ratings, monitoring features and

For information on Eaton’s Powerware SPD prowww.powerware.com/tvss.

Innovative TechnologySince 1980, Innovative Technology products hadifcult electrical transient problems for businement and defense sectors. Innovative Technologtechnologies protect electrical, data, telecom cirequipment from the effects of lightning-inducedswitching transients, and internally generated el

As a part of Eaton’s electrical business since 20Technology SPD products are even better positistate-of-the-art customer solutions. Innovative Tare designed to be the most rugged and durable Based on extensive proven eld performance, Inwas the rst to offer a 20-year full replacement engineers around the world recognize Innovativleader in the SPD industry. A leading research cof over 10 000 users rated Innovative Technolo



Summary of Applicable UL and IEEEStandards for Surge Protection Devices

TABLE 1. STANDARD DESCRIPTIONS

UL 1449 does not require a maximum surge current test.

Underwriter Laboratories — UL 1449 (Revision 7-2-87),“Transient Voltage Surge Suppressors (TVSS)”

UL 1449 is the standard for all equipment installed on the load side of

the AC electrical service and throughout the facility for AC distributionsystems. This includes both hardwire and plug-in products. To obtaina UL Listing, the suppressor must meet the required safety standardsand pass a duty cycle test. In addition, UL conducts a Let-ThroughVoltage test on the suppressor and assigns a Suppressed VoltageRating (SVR). UL 1449 ratings represent a component rating and notthe actual let-through voltage of the electrical distribution system(i.e., UL 1449 does not include the effects of installation lead lengthand overcurrent protection) A duty cycle test is based on a 26 shot

Notes

1. UL 1449 Second Edition does not test a suppressoimportant test waveforms such as the IEEE Cat. C

entrance surge (20 kV, 10 kA) or the B3 RingwavekHz), the most common type of transient inside a

2. UL does not verify the TVSS device will achieve manufacturer’s published surge current ratings. Nprovides the guidelines for product specication.

3. Plug-in products are tested differently and cannot compared to hardwired devices.

STANDARD(CURRENT REVISION DATE) PURPOSE OF STANDARD/COMMENTS

UL 1449 (1987) —Transient Voltage Surge Suppressors

1. Safety test (constructed of approved components in a safe manner).2. Suppressed Voltage Rating (let-through voltage using the IEEE C62.41 C1 test wave).

Other IEEE recommended waveforms such as the C3 and B3 Ringwave are not tested by UL.

UL 1449 (2nd Edition 1996) 1. Additional Safety tests. Test for other standards used to improve safety of products.2. Surge Test. Let-through voltage tested at lower current than 1st Edition.

10 kA (IEEE Cat. C3) used for the first time, however, it was used only to see if products fail safely.UL 1449 (2nd Edition 2007) 1. Stringent new safety requirements. New tests subject TVSS units to prolonged AC overvoltage condi

ensure safe failure modes.2. UL label changes to the wording of the short circuit current rating.3. New Testing at 10, 100, 500 and 1000 amperes and system voltage were added to ensure the units fail i

UL 1449 (3rd Edition 2009) 1. TVSS will now be referred to as SPD (Surge Protective Devices).2. UL 1449 is now ANSI/UL 1449.

3. Addition of four types of SPDs to cover Surge Arrestors, TVSS, Surge Strips and component SPDs.UL 1283 (1996) —Electromagnetic Interference Filters

This safety standard covers EMI filters connected to 600 V or lower circuits. The UL 1283 is a safety staninclude performance tests such as MIL-STD-220A Insertion Loss or Cat. B3 Ringwave Let-Through Volt

UL 497, 497A, 497B Safety standard for primary telephone line protectors, isolated signal loops and surge protection used ondata lines. No performance tests conducted for data/communication lines.

IEEE

C62.41.1 (2002) IEEE Guide on the Surge Environment in Low-Voltage AC Power Circuit s.This is a guide describing the surge voltage, surge current, and temporary overvoltages (TOV) environmen[up to 1000 V root mean square (rms)] ac power circuits.

IEEE C62.41.2 (2002) IEEE Recommended Practice on Characterization of Surges in Low-Voltage AC Power Circuits. This d the test waves for SPDs.

IEEE C62.45 (2002) Guide on Surge Testing for Low Voltage Equipment (ANSI). This document describes the test methodoIEEE Emerald Book Reference manual for the operation of electronic loads (includes grounding, power requirements, etc.).NEMA

LS-1 NEMA Technical Committee guide for the specification of surge protection devices including physical anoperating parameters.

NEC

National Electrical Code Articles 245, 680 and 800.NFPA

780 Lightning Protection Code recommendations for the use of surge protection devices at a facility service en



UL 1449 (1996 & 2007 2nd Edition)

Underwriters Laboratories Standard for Safety for Transient VoltageSurge Suppressors (UL 1449) is the primary safety standard forTransient Voltage Surge Suppressors (TVSS). This standard covers allTVSS products operating at 50 or 60 Hz, at voltages 600 V and below.

The UL 1449 safety standard was rst published in August of 1985.As TVSS products have evolved in the marketplace, the standard hasbeen updated to ensure the continued safety of the increasing sizes,options and performance of new TVSS designs. The second editionof UL 1449 was published in 1996. The second edition of the UL1449 TVSS standard was revised in February 2005 and requiredcompliance by February 9, 2007. All TVSS products manufacturedafter February 9, 2007 must comply with the February update tothe standard. A third edition of UL 1449 was published in Septemberof 2006 with compliance required by October of 2009. This articlerelates to the latest revision of the second edition of UL 1449,which is currently in effect and is acceptable until October of 2009.

To obtain a UL listing, a suppressor must pass a series of testsdesigned to ensure it does not create any shock or re hazardsthroughout its useful life. Each TVSS product is subjected to thefollowing electrical and mechanical tests: Leakage current, tempera-ture, ground continuity, enclosure impact, adequacy of mounting,and many others. Each test evaluates a different function or potentialfailure mode of a TVSS. To obtain UL certication, the TVSS unit mustpass all tests. Two of the most signicant tests performed on a TVSSare the measured limiting voltage test and a series of abnormal

overvoltage tests.The Measured Limiting Voltage test is used to assign each TVSS aSuppressed Voltage Rating (SVR), which appears on all UL certiedunits. This rating takes the average let-through voltages of three6000 volt, 500 ampere combination wave impulses (IEEE 62.41 catC1 test waves) and rounds up to the next highest standard SVR classset by UL. The standard SVR classes are 330, 400, 500, 600, 800,1000, 1200, 1500, 2000, 2500, 3000, 4000, 5000 and 6000 V. Forexample, a 401 V average let-through voltage is rounded up to a 500V SVR. The test is conducted with 6 inches of lead length, (length ofwire from TVSS to test equipment connection point). Let-through

voltages are signicantly affected by lead length. Therefore, a 6-inchlead length is used to standardize the test. The SVR value allowssome comparison from one TVSS to another, but does not representan expected eld installed let-through voltage since actual installedlead length will vary from installation to installation.

The last major series of tests are the abnormal overvoltage tests.The purpose of these tests is to ensure that the TVSS will not createa shock or re hazard even if the unit is misapplied or subjected to

In addition to successfully passing all applicableTVSS units must be suitably and plainly markeinclude name of the manufacturer, a distinctive electrical rating, Short Circuit Current Rating (Sdate or period of manufacture. The TVSS must

the words “Transient Voltage Surge Suppressor”able to be additionally marked immediately follwith the words “(Surge Protective Device)” or “

The best way to verify that particular TVSS unita search on the UL Web site at www.ul.com. Thgory for TVSS is UL category code “XUHT.” Ana vendor’s listing is to call UL at 1-847-272-880provides a user with the condence their TVSS a shock or re hazard during use.

UL 1283 Electromagnetic Interference Filte

Surge suppressors must be listed (or recognizedThose devices employing an EMI Filter can alsolisted under UL 1283 to ensure the lter compodesigned to withstand the required duty cycle anments. UL 1283 covers EMI lters installed on,600 V or lower circuits. These lters consist of inductors used alone or in combination with eacunder this requirement are facility lters, hardwdevices. UL 1283 reviews all internal componeninsulating material, ammability characteristicsleakage current, temperature ratings, dielectric w

overload characteristics.

Note: UL 1283 does not include performance MIL-STD-220A insertion loss test to determinethe lter at the desired frequency (i.e., 100 kHz power systems) or the Let-Through Voltage testB3 Ringwave.

UL 1449 (2009 3rd Edition)

UL 1449 Third Edition is now ANSI/UL 1449. designation helps the standard gain relevance inbrings it closer to the IEC standards. By becomidard” and forming a “Voting Committee,” the stconformance to NAFTA. This revision changesTVSS devices, from TVSS to Type 2 Surge ProtThe SPD is used as an umbrella designation andsurge protective products. The “TYPE” designabe determined based on the installation locationsystem. Some examples are Surge Arrestors (TyConnected TVSS (Type 3 SPD) and a new categ




Data/Communication Line Protectors (UL 497, 497A, 497B)

UL 497 is the safety standard for single or multi-pair Telco primaryprotectors. Every telephone line provided by a telephone operatormust have an UL approved T1 protector (gas tube or carbon arrestor)in accordance with Article 800 of the NEC. A primary protector isrequired to protect equipment and personnel from the excessivepotential or current in telephone lines caused by lightning, contactwith power conductors and rises in ground potential. UL 497Aapplies to secondary protectors for communication circuits.Secondary protectors are intended to be used on the protectedside of telecommunication networks (it assumes primary protectorsare in place) that have operating rms voltage to ground less than150 volts. These protectors are typically used at the facility incomingservice or other areas where communication circuits require protec-tion. UL 497B applies to data communication and re alarm circuitprotectors (communication alarm initiating or alarm indicating loop cir-cuits). This includes most dataline protectors in the electrical industry.

ANSI/IEEE C62.41 (2002) Recommended Practice onSurge Voltages in Low Voltage AC Power Circuits (ANSI)

This document describes a typical surge environment based onlocation within a facility, powerline impedance to the surge and totalwire length. Other parameters include proximity, type of electricalloads, wiring quality and geographic location.

The document only describes typical surge environments and

does not specify a performance test. The waveforms included inthe document are meant as standardized waveforms that can beused to test protective equipment. Any statement where a manufac-turer advertises that its “protector meets the requirement of,”or is “certied to IEEE C62.41," is inappropriate and misleading.

Two selected voltage/current waveforms (see Figures 1

and 2

)are identied as representative of typical electrical environments:

1. Combination Wave: A unipolar pulse that occurs most oftenoutside a facility (e.g., a lightning strike).

2. 100 kHz Ringwave: An oscillating waveform that occurs most

often inside a facility.

FIGURE 2. RINGWAVE

The amplitude and available energy of the standard wadependent upon location within a facility.

As shown in Figure 3

, locations are classied into t

Category A: Outlets and Long Branch Circuits

All outlets at more that 10 m (30 ft.) from Category

All outlets at more than 20 m (60 ft.) from Category

Category B: Feeders and Short Branch Circuits

Distribution panel devices.

Bus and feeder distribution.

Heavy appliance outlets with “short” connections toservice entrance.

Lightning systems in large buildings.

Category C: Outside and Service Entrances

Service drops from pole to building.

Runs between meter and panel.

Overhead lines to detached building.

Underground lines to well pump.

The Category C surges can enter the building at the servSPDs must be sized to withstand these types of surges winstalled at switchgear or service entrance switchboardvariable used to classify the environment of a power diis Exposure. As shown in Figure 4

, IEEE has delevels that characterize the rate of surge occurrence ver

10000

8 000

6 000

8000

6 000

4 000

2 000

0

-2 000

-4 000-1 0 0 1 0 2 0



FIGURE 3. IEEE C62.41 LOCATION CATEGORIES

Isokeraunic maps provide a good baseline for evaluating lightningoccurrence within a region. Discussions with local utilities and othermajor power users combined with power quality surveys are usefulfor measuring the likely occurrences from load switching and powerfactor correction capacitors.

For each category and exposure level, IEEE has dened the testwaveform that should be used by a specier when determiningperformance requirements. For example, most SPDs installed at the

main service panel after the meter are in a Category C environment.Table 2

details the C62.41 test waveforms for Categories A, B and C.

In the C62.41 (2002) document, special waveforms have beenidentied to addresses large banks of switching capacitors or theoperation of fuses at the end of long cables. These situations warrantthe consideration of additional waveforms whose energy is greaterthan those stipulated for Category A, B and C environments.

Many speciers are confused about the recommendations contained

Category A– Long branch circuits– Indoor receptacle

Category B

– Ma jor f eeders– S hort branch circuits– Indoor ser vice panels

Category C– O utdoor o verhead lines– S er vice entrance

10

10

10

10

1

Number of Surges per YearExc ee din g Surge C res t of A b ici ssa




IEEE C62.45 (2002) — Guide on Surge Testing for EquipmentConducted to Low Voltage AC Power Circuits

This document provides appropriate surge testing guidelines forequipment survivability, methods of test connection, surge couplingmode denitions, testing safety requirements and various theories ofsurge suppression techniques. The intent is to provide backgroundinformation that can help determine if specic equipment or a circuithas adequate withstand capability.

An important objective of the document is to call attention to thesafety aspects of surge testing. Signal and datalines are notaddressed.

TABLE 2. IEEE C62.41 CURRENT/VOLTAGE WAVEFORMS FORVARIOUS EXPOSURE LOCATIONS

IEEE Std. 1100 (2005) Emerald Book Recommended Practicefor Powering and Grounding Sensitive Electronic Equipment

This publication presents recommended engineering principles andpractices for powering and grounding sensitive electronic equipment.This standard is the recommended reference book for facility-widepower quality solutions. The scope of this publication is to:“recommend design, installation and maintenance practicesfor electrical power and grounding of sensitive electronic processingequipment used in commercial and industrial applications.”The following sections apply to surge protection devices:

Chapter 3 (particularly 3.4.2 and 3.4.3).

Chapter 4 (particularly 4.2 and 4.4).

Chapter 8 (particularly 7.2).

Chapter 9 (particularly 8.6).

NEMA LS-1

This document is a specication guide for surge protecfor Low Voltage AC Power applications (less than 1000document identies key parameters and evaluation prospecications. NEMA employed established referencesIEEE and UL guidelines. The following parameters arethe LS-1 document:

Maximum continuous operating voltage (MCOV).

Modes of protection.

Maximum surge current per mode.

Clamping voltage (A3, B3 Ringwave, B3/C1 Impul

EMI noise rejection (insertion loss).

Safety UL approvals (including UL 1449, UL 1283

Application environment.NEMA LS-1 (and other organizations) do not recommeJoule ratings or response time as a performance criteria

National Electrical Code (United States):NEC — Article 280, 285, 645 and 800 Surge Arre

Note: The adequacy section of the code clearly statescompliance with the code will not ensure the proper eqperformance. This fact is often overlooked by end userconsidering electrical designs from a low bid perspectiv

Article 280 covers the general requirements, installatioments and connection requirements for surge arrestors premises wiring systems.

Article 285 covers the general requirements, installatiorequirements, and connection requirements for transiensurge suppressors (TVSS) permanently installed on prewiring systems.

Article 645 covers Electronic Computer/Data Processinand references NFPA 75.6.4 regarding the Protection oComputer/Data Processing Equipment.

Article 800 reviews Protection requirements (800-31), Protector requirements (800-32) and Cable and Protect(800-40) for communication circuits.

National Fire Protection Association (NFPA) —780 Lightning Protection Code

NFPA 780 is the code for lightning protection systems athe protection requirements for ordinary structures, mis

CAT. LEVELVOLTAGE(KV)

0.5 µ S X 100 KHZRING WAVECURRENT (A)

1.2 X 5 µ S (V)8 X 20 µ S (A)COMBINATION WAVECURRENT (KA)

A1A2A3

LowMediumHigh

236

70130200

———

B1B2B3

LowMediumHigh

246

170330500

123

C1C2C3

LowMediumHigh

61020

———

3510



High Resistance Groundingand Wye or Delta Surge Protection Devices

In today’s manufacturing facilities, ground faults can wreak havocon production and process equipment. These manufacturing facilitiesmay have a high resistance grounding (HRG) system. In a HRGsystem, a resistance, which is connected between the neutral ofthe transformer secondary and earth ground, is used that effectively

limits the fault current to a low value current under ground faultconditions. Usually, the current is limited to 10A or less. As a result,the system will continue to operate normally even under the groundfault condition.

Figure 5 depicts a system that has a resistance grounding scheme.In the case where surge suppression is required for a 3-phase,4-wire, wye system with a neutral ground resistance (NGR), a3-phase, 3-wire, Delta SPD will want to be specied and used.

In a wye system, the neutral and ground are both located at thecenter, as shown in Figure 6 . If the neutral is bonded to the ground,the system will remain unchanged under fault conditions.

In the case where the neutral is not bonded to ground and a faultcondition is present, the ground will ‘move’ towards the phase thathas the fault. Figure 7 shows a fault condition on phase C. The resultis phase A to ground and phase B to ground are now at line to linevoltage instead of line to neutral voltage. If a 3-phase, 4-wire, wyeSPD was installed in an application where the neutral was not bondedto ground and a fault condition occurred on one of the phases, theresult would be SPD failure.

In today’s electrical systems, with many different grounding systemsand various voltages, determining which SPD voltage conguration to

specify can by confusing. Following are several helpful guidelines tofollow when specifying SPDs:

Only apply a wye (3-phase, 4-wire) congured SPD if the neutral isphysically connected to the SPD and if the neutral is directly andsolidly bonded to ground.

Use a Delta (3-phase, 3-wire) congured SPD for any type ofimpedance (resistive, inductive) grounded system.

Use a Delta (3-phase, 3-wire) congured SPD for a solidlygrounded wye system where the neutral wire is not pulledthrough to the SPD location.

Use a Delta (3-phase, 3-wire) congured SPD if the presenceof a neutral wire is not known.

FIGURE 5. RESISTANCE GROUNDING SCHEME

FIGURE 6. WYE SYSTEM

A

R

C

Ground

A

C

NeutralG r o u n

A



Surge Current per Phase(Industry Denition)

Engineers/speciers routinely install TVSS devices at the serviceentrance and key branch panels to protect sensitive microprocessorloads such as computers or industrial control devices from damagingsurges and noise. These devices are available in a wide range of sizesto meet different application requirements. Suppressors located at

the facility’s service entrance must handle higher energy surges thanthose located at branch panels.

TVSS devices are classied by the unit’s maximum “surge current”measured on a per phase basis. Surge current per phase (expressedas kA/phase) is the maximum amount of surge current that can beshunted (through each phase of the device) without failure and isbased on the IEEE standard 8x20 microsecond test waveform.

As per NEMA LS-1, TVSS manufacturers are required to publishthe level of surge protection on each mode. A Delta system canemploy suppression components in two modes (L-L or L-G). For WYEsystems, shunt components are connected L-G, L-N and/or N-G.

How to Calculate “Surge Current per Phase”The per phase rating is the total surge current capacity cogiven phase conductor. For example in a WYE system, Lmodes are added together since surge current can ow parallel path. If the device has only one mode (e.g., L1-“per phase” rating is equal to the “per mode” rating becthere is no protection on the L1-N mode.

Note: N-G mode is not included in the surge current pcalculation.

Almost all suppressor manufacturer’s follow this conveHowever, there are some companies who attempt to cauconfusion by inating their surge current ratings using amethod for calculating surge current per phase. As showcorrect mode and phase ratings are displayed.

TABLE 3. EXAMPLE OF WYE SYSTEM —MODES OF PROTECTION PER PHASE (KA/Ø)

SummarySurge current per phase (kA/phase) has become the stanparameter for comparing suppression devices. Most repmanufacturers publish surge current ratings on a per moper phase basis. Some suppression manufacturers may current ratings or make up their own method to calcularatings. Avoid manufacturers who do not clearly publisindustry standards-per phase and per mode surge capab

MODEL L-N L-G NG

120 kA per Phase TVSS 60 60 60



Facility-WideSurge Suppression

As recommended by IEEE (Emerald Book 1992), TVSS units need tobe coordinated in a staged or cascaded approach. IEEE provides thefollowing recommendations:

“... For large surge currents, (transient) diversion is best accomplishedin two stages: the rst diversion should be performed at the serviceentrance to the building. Then, any residual voltage resulting fromthe action (of the suppression device) can be dealt with by a secondprotective device at the power panel of the computer room (or othercritical load). In this manner, the wiring inside the building is notrequired to carry the large surge current to and from the diverter atthe end of a branch circuit. ”

“... proper attention must be given to coordination of cascaded surgeprotection devices. ”

Figure 8 demonstrates the effectiveness of a suppression systemwhen used in a two-stage (cascaded) approach.

As demonstrated, the two-stage approach ensures that both typesof disturbances are suppressed to negligible levels at the branchpanel (<150 V Let-Through). This prevents high energy transientsfrom damaging components and ensures that fast low level ring-waves will not degrade or disrupt the operation of downstreammicroprocessors.

This ensures the system performance meets the following IEEE(Emerald Book, 1992) recommended performance:

“ While electromechanical devices can generally tolerate voltages ofseveral times their rating for short durations, few solid-state devices

can tolerate much more than twice their normal rating. Furthermore,data processing equipment can be affected by fast changes involtages with relatively small amplitude compared to the hardware- damaging overvoltages. ”

FIGURE 8. FACILITY-WIDE PROTECTION SOLUTIOBOOK RECOMMENDS A CASCADE (OR 2-STAGE)

Stage 1 Protection(Ser v ice Entrance )

St(B

480 V 2 77 V

S y s te m Te s t Para m eter s :

IEEE C6 2 .4 1 an d C6 2 . 4 5 te s t p roce du480 V m ain entrance p ane ls ;

100 f eet o f entrance w ire ;

480 / 2 08 V d is tri b u tion tran s f or m er ; a

2 08 V b ranc h

2 0,000 V

In pu t — h ig h energtran s ient d is tu rb ancIEEE Categor y C3 Im2 0

,000 V : 1 0

,000 A

B e s t ac h ie v a b lep er f or m ance w ith s ing l

at m ain p ane l (1000 V a

T w o -s tage (cac h ie v e s b e s(le ss th an 1 5

2 5 u ST im e (M icro s econ d

5 0

T V SS



Debunking the Surge Current Myth,“Why Excessive Surge Current Ratings are Not Required”

When Will it Stop?It seems that every year surge suppressor manufacturers areincreasing the surge current ratings of their devices. For example, awell known TVSS manufacturer has made the following recommen-dations to the consulting community for main panel surge protection:

TABLE 4. MANUFACTURER RECOMMENDATIONS

The same model has changed surge ratings three times in lastseveral years! In fact in 1998, the company also introduced a unit thatis theoretically rated to 650,000 A per phase. The above exampleillustrates how some manufacturers use irrelevant justications topromote the sale of a premium priced suppressor.

We believe it is time to debunk the game and present the factson what is an acceptable level of surge current for service entrancelocations.

Why Stroke Current is Not Related to TVSS Surge CurrentThe stroke current associated with lightning is not related to asuppressor’s surge current rating. It is physically impossible to havethe energy associated with a lightning stroke travel down the ACpower conductors.

Figure 9 is a graph published by the IEEE Std. 1100 (the EmeraldBook) and by the ANSI/IEEE C62.42 committee responsible forsurge protection devices. The IEEE lightning research provides thefollowing conclusions:

Stroke current is related to the lightning strike (traveling betweena cloud and earth or between clouds).

50% of recorded direct lightning strokes are less than 18,000 A.

.02% of the strokes could have a surge current of 220 kA.

An unusual event was recorded that had a stroke of approximately450 kA; however, this is a controversial measurement.

TVSS MythA TVSS manufacturer may suggest a “one in a million” lightning

Reality“Stroke current” has no relationship to the “surge curreconducted on the AC power distribution system. There ireason to specify a surge suppressor having 400 kA/phacurrent rating.

DiscussionIn Florida (worst case in the U.S.), there are six groundkm 2 (IEEE C62.41). A facility occupying one acre wildirect strike every 40 years. Based on the percentages ithe facility will experience one stoke exceeding 200 kA800 years.

“ The crest current magnitude of an actual lightning striwidely. Typical surges conducted or induced into wire lwould be considerably smaller because of the availabilipaths. As a result, protectors at the termination of thesenormally not designed to withstand the full crest currenstrokes. ”

— quote from IEEE C62.42 1992, Paragraph 3.1.1

When lightning hits the earth, a powerline or facility, menergy ashes to ground or is shunted through utility suThe remaining energy that is induced on the AC powercalled surge current (measured in kA). The surge currensuppressor is a small fraction of the lightning stroke cu

Based on available research, IEEE recommends using t10 kA combination wave as the representative test for ilightning surges at service entrance locations. Above ththe voltage will exceed BIL ratings causing arcing in thor distribution system.

In summary, low voltage wiring (<600 volts) is not capconducting the lightning stroke currents as presented inEngineers should not use lightning stroke current as a mspecifying suppressors having a rating over 400 kA/pha

YEARRECOMMENDED SURGECURRENT RATING (KA/PHASE)

1993 250 kA/phase1994 350 kA/phase1995 >500 kA/phase2006 >1000 kA/phase

Distribution of Lightning Stroke Currents

Stroke Current (kA)250

200

1 50

1 00

(Sour ce : IEEE St d . C62 . 42 - 1 99 2 , Pa ra gr ap h 3

(0 . 02 ; 220 )



Why is 250 kA/Phase an Acceptable Rating?The above discussion proves that 500 kA lightning stroke current cannot exist on the AC powerline. If IEEE recommends testing serviceentrance TVSS units to 10 kA, why do many suppliers, including us,suggest a 250 kA/phase device be installed? The answer is reliability,or, more appropriately, life expectancy.A service entrance suppressor will experience thousands of surges ofvarious magnitudes. Based on statistical data, we can determine thelife expectancy of a suppressor. A properly constructed suppressorhaving a 250 kA/phase surge current rating will have a life expectancygreater than 25 years in high exposure locations.

Note: A 400 kA/phase device would have more than 100 years —well beyond reasonable design parameters.

Should a suppressor fail, it is most likely due to temporaryovervoltage (TOV) on the utility powerline; e.g., when a 120 Vcircuit rises to 200 VAC or greater. A larger sized suppressor willnot protect against TOV.



Surge Arrestor vs.Surge Suppressor

The use of surge protection devices (surge suppressors) is growingat over 20% per year. Suppressors are now routinely installed at theservice entrance and key down-stream panelboard or MCC locationsto provide clean power to solid-state loads. Currently, there is someconfusion between the application of surge arrestors and surge

suppressors — especially in industrial facilities, water treatmentplants and other areas where arrestors were predominately used.This section explains the differences in performance and applicationbetween the two technologies.

The Evolution of Surge/Lightning ArrestorsIn the past, when non-linear or solid-state devices such as comput-ers, PLCs and drives were not yet in use, relays, coils, step switches,motors, resistors and other linear loads were the standard. Utilitycompanies and end users were concerned with how to protectelectrical distribution systems from lightning surges. Their objectivewas to ensure that voltage surges did not exceed the basic insulationlevel (BIL) of the conductor wires, transformers and other equipment.Consequently, arrestors were developed for use in low, medium andhigh voltage applications at various points in the transmission anddistribution system. The fact that these devices created a “crowbar”between the phase conductor and ground did not matter to theseloads if it cleared within a few cycles.

Arrestors are still used in the electrical industry primarily alongthe transmission lines and upstream of a facility’s service entrance.Arrestors are available in various classes depending upon their with-stand capability (e.g., station vs. distribution class). At the service

entrance location on low voltage systems (600 volts and below),surge suppressors are now replacing the use of arrestors.

The Evolution of Surge Protection Devices (also called TVSS)In today’s computer age, the use of solid state (nonlinear) loadsis increasing dramatically. Research by Utilities and other groupsestimated that 70% of utility loads are consumed by electronicequipment such as drives, PLCs, computers, electronic ballasts,telecommunication equipment, etc.

Modern day electronic equipment is getting faster, smaller, moreefcient and very complex. These improvements have been made in

all microprocessor-based equipment over the years, and this progresswill continue.

The trade-off in faster speed and lower cost is that the microproces-sor loads are becoming increasingly more susceptible to the effectsof transients and surges.

As a design objective, the IEEE Emerald Book (and thecurve) recommend reducing 20,000 volts induced lightdisturbances down to two times nominal voltage (< 330To achieve this level of performance, surge suppressorsdeveloped. Since the mid-1980s, these devices have be

the preferred choice for protecting loads within any facLightning arrestors were designed to protect the electrition system and not the sensitive solid-state equipmenteffects of lightning.

As in Table 5 , lightning arrestors have a high let-throthe key performance factor for protecting electronic loaIEEE Category C3 test wave (20 kV, 10 kA), the let-thris typically over 1200 volts (on a 120 VAC system).

This is satisfactory for insulation protection on transforpanelboards and wiring. For VFDs, computers, PLCs a

sensitive equipment, however, the solid-state componendamaged or “upset” by these surges. Using suppressorsservice entrance and key branch panels, the surge will breduced to under 100 volts.

Note: If a TVSS and lightning arrestor are both used aentrance switchboard, the TVSS will do all of the workon” earlier and shunt most of the surge current.

Many water treatment plants, telecommunication facilitschools and heavy industrial plants utilize TVSS insteaarrestors to provide protection against the effects of lig

switching, switching electric motors, etc. New suppresscan now be integrated into motor control buckets, switcother distribution equipment, providing more effective and eliminating installation problems.

When selecting a suppressor, look for a quality device hthe following features:

Low let-through under IEEE Category B3, C1and C

Independently tested to the published surge current(per phase).

Includes internal fuses.

Includes internal monitoring features (for both openMOV failures).

Includes electrical noise ltering (55 dB at 100 kHz

Small footprint design for more effective installatio

Listed under UL 1449, UL 1283, and CSA



TABLE 5. DIFFERENCE BETWEEN ARRESTORS AND SUPPRESSORS

DESCRIPTION

SURGE ARRESTOR SURGE SUPPRESSOR

480 V (277 V L-N) 208 V (120 V L-N) 480 V (277 V L-N) 208 V (12

Let-Through Voltages(based IEEE test waves):Cat. C3 (20 kV, 10 kA)Cat. C1 (6 kV, 3 kA)Cat. B3 (6 kV, 500 A, 100 kHz)

>1500 V>1200 V>1500 V

>1000 V>1000 V>1000 V

900 V800 V200 V

Internal Monitoring Capabilities(identify internal failure and activateremote alarm or lights)

NO NO Yes (most quality devices)

EMI/ RFI Filtering NO NO Yes (most quality devices)Internal Fusing (overcurrent protection) NO NO Yes (most quality devices)Design Gapped MOV Gapped MOV MOV / Filter (hybrid)

Interrupts Power (crowbar) Yes (typical 1/2 cycle) Yes (typical 1/2 cycle) NoFailure Explosive Explosive Trips Breaker / FuseWarranty Limited Limited 5 years or more

(on most quality devices)Life Expectancy Limited

(throw away devices)Limited(throw away devices)

>25 years(if sized appropriately)

B f H b id Fil i



Benets of Hybrid Filteringin Surge Protection Devices

A surge suppressor (TVSS device) prevents harmful surge voltagesfrom damaging or disrupting sensitive electronic equipment.There are two types of suppression devices:

1. “Basic Suppressor” Devices — Transient suppressors that useonly voltage dependent components such as Metal Oxide Varis-tors (MOVs) or silicon avalanche diodes (SADs).

2. “Hybrid Filter” Devices — Hybrid devices that employ a parallelcapacitive lter circuit in addition to MOVs. Since these productsare able to eliminate low amplitude transients and high frequencyEMI/RFI noise, they are widely specied for commercial, hospitaland industrial facility construction projects. See Figure 10 .

Unfortunately it is often difcult to distinguish between “hybridlter” and “basic suppressors” when reviewing the performancespecications provided by the manufacturer of either type of device.In addition, specifying consultants are often unsure of the practical

benets offered by the lter components. This section describesthe differences between the two technologies when installed inan electrical distribution system.

A “hybrid lter” protects sensitive electronic equipment againsthigh amplitude lightning impulses, low level ringing transients andEMI/RFI noise disturbances. In comparison, “basic suppressors”do not have lter components and can only suppress high voltagedisturbances. Table 6 summarizes the key differences between thetwo technologies.

a) Ringing Transient Suppression

Studies performed by ANSI/IEEE and other organizations indicatethe oscillatory ringwave is the most common type of transientwaveform occurring within a facility’s electrical distribution system.Normal impedance characteristics of a low voltage distributionsystem create ringing oscillatory waves at frequencies between50 kHz and 250 kHz.

Internal transients at these frequencies are common and can resultin damaged integrated circuits, system lock-ups, reboots or otheroperational problems. To model this ringing effect, ANSI/IEEE C62.41(2002) recommends testing all suppression devices to the 100 kHzRingwave (Category B3; 6000 V, 500 A waveform). See Figure 11 .

Published let-through voltages are then used to comparesuppression performance.

FIGURE 10. BASIC SUPPRESSOR AND HYBRID FILTER

FIGURE 11. RINGWAVE

TABLE 6. COMPARISON OF SUPPRESSOR TECHNOLOGIES

6,000

4 ,000

- 4 ,000

2 ,000

- 2 ,000

0

0 1 0 2 0

Ringwave (Cat. B3 , 6000 V 1 00 kHz)

TVSS PERFORMANCE CRITERIA HYBRID FILTER BASIC SUPPRESSOR

Repetitive Surge Withstand Capability Longer Life Expectancy Limited Life



Figure 12 illustrates the superior performance of a “hybrid lter”suppressors when tested to the standard IEEE B3 Ringwave. Filtercomponents provide a low impedance path at higher frequencies(e.g., 100 kHz) allowing impulses to be shunted away from sensitiveloads, at any phase angle along the 60 Hz AC sine wave. This “sine

wave tracking” feature suppresses disturbances at much lowerlevels than possible with a “basic suppressor” (nonltered device).

Without a lter, the MOVs are able to clamp the transient only oncewhen the voltage exceeds the “turn on” point of the MOV. As shownin Figure 12 , the MOV let-through voltage is signicantly higherdue to the impedance associated with wire lead lengths and theMOV operating characteristics. This is over 3 times the let-throughvoltage of the TVSS Filter. As a result, the level of protectionprovided is limited.

b) EMI/RFI Noise Attenuation

Filters remove high frequency EMI/RFI noise associated with loadssuch as:

Variable speed drives.

Photocopiers.

Large UPS.

Arc welders.

SCR controlled loads.

Light dimmers.

These types of noise generating loads are found in almost everyfacility. IEEE denes noise as disturbances less than 2 times peakvoltage (e.g., less than 340 V peak on 120 V systems).

The key performance lter testing standard is the MIL-STD-220A,50 Ohm insertion loss test. Manufacturers should publish noiseattenuation levels measured in decibels (dB) obtained at 100 kHz.Test data based on computer simulations such as SPICE programs

are not reective of actual environmental condinot acceptable for comparing lter performancepublished dB ratings at frequencies over 1 MHzfor panel “hybrid lter” products. Above 1 MHdoes not travel on the conductor (i.e., it is radiat

the atmosphere).For premium performance, the lter attenuation at 100 kHz (based on MIL-STD-220).

Note: Have the suppressor supplier provide acensure this level of ltering is being provided.

c) System Noise/Suppression Capability“TVSS Filters” installed at the service entrance meet with the IEEE recommended approach to fPlease see Facility-Wide Surge Suppression on

additional information.In addition, a system-wide suppression design pnormal mode and common mode noise attenuatgreater than a stand-alone device.

Summary“TVSS Filters” offer signicant benets that enquality within a facility. This section illustrates ware now the most commonly specied suppress

Manufacturers may offer misleading claims andaccurate performance standards. Engineers shousuppression device chosen offers sufcient ringnoise attenuation and provides coordinated facimanufacturers claiming to offer sine wave tracknents must support these claims by submitting tspectrum analysis. Without these submittals, it isuppressor will be supplied rather than the requ

Input Wave: IEEE B3 Ringwave(6000 V, 500 A, 100 kHz)

No F ilte r

P oor F ilte r

Qua lity F ilte r (55 d B at 100 kHz)( V

o l t

s )

600

4 00

2 00

Factory Automation (PLCs) and



Factory Automation (PLCs) andTheir Need for Surge Suppression

End users often ask us why our surge protection is necessary forprotecting process control systems. Most people assume that pro-grammable controls and automation equipment are fully protectedfrom power disturbances. As the following section explains, PLCmanufacturers and service technicians recommend the use of

surge suppressors and lters to prevent downtime and equipmentdamage due to surges and electrical line noise.

A major study on how power disturbances effect process controlsystems has been conducted by Dranetz Technologies and PowerCetcorporation. Results of the study indicate that impulses, surges andelectrical noise cause the following equipment problems:

Scrambled memory.

Process interruption.

Circuit board failure.

Ac detection circuits cause false shutdown.

Setting calibration drift.

Power supply failure.

Lock up.

SCR failures.

Program loss.

Digital/Analog control malfunction.

“ Sensitivity to electrical interference varies dramatically from onesystem to another, depending upon grounding conditions, equipmentsensitivity, system design and quantity of electronic equipment inthe area. ”

--Dranetz Field Handbook For Power Quality Analysis, 1991

Facility downtime and repair costs associated with these powerquality problems represent a growing concern for engineers andmaintenance staff. Power protection is now widely recognizedas an important factor in the design of process control systems.Major PLC manufacturers such as Allen-Bradley and Siemens provide the following recommendations:

1. Allen-Bradley SLC500 Operational Manual 17Series A

“ Most industrial environments are susceptible to sients or spikes. To help ensure fault free operatiotion of equipment, we recommend surge suppresson power to the equipment in addition to isolation“ Lack of surge suppression on inductive loads mato processor faults and sporadic operation. RAM ccorrupted (lost) and I/O modules may appear to bor reset themselves. ”

2. Siemens AG. Automation Group EWA 4NEB 8“ Measures to suppress interference are frequentlywhen the controller is already in operation and recnal has already been affected. The overhead for su(e.g., special contactors) can often be considerablyobserving the following points when you install yThese points include :

Physical arrangements of devices and cables.

Grounding of all inactive metal parts.

Filtering of power and signal cables.

Shielding of devices and cables.

Special measures for interference suppression

3. Allen-Bradley Publication 1785-6.6.1

“ Electromagnetic interference (EMI) can be generated inductive loads such as relays, solenoids, motor startersare operated by ‘hard contacts’ such as push buttons orswitches. Following the proper wiring and grounding prthe processor system against the effects of EMI. Howevcases you can use suppression networks to suppress EMsource. ”

Regardless of the manufacturer, electronic equipment ito power disturbances. This results from two contributi

1. Processors themselves are increasingly complex w

chip density and lower operating voltages.2. The growing use of disturbance generating loads s

able frequency drives, capacitor banks, inductive wide variety of robotic equipment.

Eaton’s series type TVSS lters were developed exclusprotection of automation equipment used in industrial eWith up to 85 dB of noise attenuation and outstanding suppression these products are well suited for the prote

Surge Protection Devices



Surge Protection Deviceswith Replaceable Modules

A Surge Protective Device (SPD) design that is offered by severalmanufactures is known as a modular design. Modular designs includeparts that can be replaced in the eld. The most common replaceablemodule version is a metal box with replaceable surge componentshoused in a smaller plug in plastic box.

In an SPD, the most commonly used surge suppression componentis an MOV (Metal Oxide Varistor). The MOV becomes a conductivecomponent when the voltage across it exceeds a certain level knownas the maximum continuous operating voltage (MCOV). Oncethe voltage exceeds MCOV, the current is allowed to ow throughthe MOV, which then passes the surge to ground. For SPDs thatare modular, the MOVs are built into these plastic boxes which areavailable for eld replacement if the internal MOV was damaged.

Some SPD manufacturers promote modular design to minimize theirproduction costs. Plus, the use of modules create an “aftermarketbusiness” for the SPD manufacturer. However, there are a number ofpotential technical aws with modular designs.

If one module is damaged, the remaining undamaged modulesbegin to compensate for the lost module. Resulting in stress tothe undamaged modules. This may lead to a second failure beforethe rst module is replaced.

Many failures result in unacceptable damage to the interior ofthe metal box. Replacement of the modules is not sufcient to getthe unit back to operating condition. These failures requirereplacement of the complete unit.

A damaged module may also cause unbalanced protection, inwhich the surge current is not equally shared across the MOVs.Most manufactures match the performance of the MOVs toachieve the specied performance. A new module will not bematched to the modules already in the product.

Many manufacturers of modular designs utilize “banana” pinconnectors instead of low impedance bolt-on connection or leads.During high surge currents, the mechanical forces can rip theseconnectors out of their sockets. And because many environmentalconditions can degrade these connectors as they rely solely onspring force to keep the connection.

Performance specications can be misleading. Often thepublished suppression ratings are for the individual module andnot for the entire SPD unit. Some manufacturers have designedmodular products just for this reason. It is important to get theSVR (UL’s surge voltage ratings, markings required on all UL Listedproducts) ratings and surge current ratings for both the moduleand for the complete product.

Another aspect to look at closely is theoretical sIn order for accurate theoretical surge current radesign criteria that must be considered.

1. Integrity of Internal Wiring

Low-end surge suppression devices may use smcircuit traces or wires, which cannot handle the Exposure to a large transient the modules can suproduct cannot survive, can leave downstream l

Most of the time these potential wiring decienSPD and hidden from the customer or specifyin

2. Equal Current Sharing to Each MOVThe SPDs internal wiring must ensure that eachcally balanced. In other words, a suppressor maensure the following performance criteria are m

Integrity of rated surge performance.All surge paths must achieve the rated surge

Life expectancy.

The total device must meet its lifetime performaA possible result to SPDs that do not share surgpremature failure. Premature failure is a commodesigns since “newer” and “older” modules do nsame MOV voltage and therefore experience a rcurrent capacity.

The Clipper Power System, Visor Series (CPS) are designed to utilize the benets of ground placonstruction of suppressors. The electrical founSPDs employ a multi-layer, low impedance Surg

Since power surges and electrical line noise are disturbances, the current travels on the surface oskin effect. The surge plane design provides theducting area without the drawbacks of heavy gafrequencies, the impedance (self and mutual indcopper plane is signicantly lower than even larbus bars.

Since all MOVs attached to the plane are at the sthe MOVs are electrically matched, surge currenStress on the MOVs is reduced because each Mand equal proportion of the total surge, resultinglife expectancy compared to devices that do notcurrent sharing.

Features of the SurgePlane include:

Why Silicon Avalanche Diodes



Why Silicon Avalanche Diodesare Not Recommended for AC Powerline Suppressors

A Surge Protection Device (SPD), also called a TVSS device, is usedto protect semi-conductor loads from powerline transients. SPDs areinstalled in the AC power system at the service entrance and panel-boards, and sometimes at the load. SPDs are also required on datacommunication lines to prevent ground loops and induced surges,

which can damage equipment.In AC power applications, over 95% of SPDs use Metal Oxide Varis-tors (MOV) because of their high-energy capability and reliable clamp-ing performance. For added performance, hybrid designs (MOVs andcapacitive lter) are typically specied.

A small number of SPD manufacturers still promote the use of SiliconAvalanche Diodes for AC applications. These companies attempt toscare customers into buying a premium priced unit by publishingmisleading information about MOV surge components. The followingsection summarizes the marketing claims and technical insightsregarding SADs suppressors.

Three SAD Myths and RealityMyth Number One : SADs have a faster response time (e.g., 5picosecond compared to 1 nanosecond for MOVs). The faster SADresponse time results in improved SPD performance.

1. NEMA LS-1 and IEEE committees do not mention the use ofresponse time as an SPD specication. All SPDs have sufcientresponse time to “turn on” and shunt surges. The response timeof an MOV is 1000 times faster than the time it takes for a surgeto reach full current (i.e., 8 microseconds). Response time is notan appropriate criteria to use when specifying SPDs.

2. The response time for a SAD device is equivalent to that of anMOV device. Response time of the device is affected more bythe internal wiring/connection than the speed of the SAD (orMOV). For example, a SAD may react in 1 picosecond but theinternal wiring and connecting leads within the SPD add induc-tance (about 1 to 10 nanohenrys per inch). This inductive effect isthe dominating factor in overall response time — not the SADreaction time.

3. Note that hybrid lters (MOVs combined with capacitive ltering)react the fastest because the capacitors activate instantaneously

to any high frequency surge.Myth Number Two : MOVs degrade resulting in short lifeexpectancy of the SPD and unsafe failures. SADs do not degradeand are safer to use.

Life expectancy of SADs is much lower than that of an MOV(see Figure 13 ). A single SAD will be damaged by a surge under1000 amperes. Given that IEEE C62.41 requires SPDs to withstand

d h f b l

FIGURE 13. SILICON AVALANCHE DIODES HAVE LIMITEDENERGY CAPABILITY

MOVs are rated from 6500 A to 40,000 A, making themfor AC power systems.

Quality SPDs often parallel MOVs to achieve surge curexcess of 250,000 A per phase. These results can be verindependent testing at lightning labs. At these ratings, toperate effectively for over 25 years in IEEE classiedenvironments.

Paralleling SADs is more difcult than with MOVs. Supparallel SADs require a signicant amount of componereduce the overall device reliability.

Given the limited energy ratings of SADs, these devicerecommended for panelboard or switchboard applicatiohybrid designs using MOVs and SADs do not achieve synergies. In high-energy applications for example, theweak link because the SADs and MOVs cannot be coorwork together.

Failure mode. SAD manufacturers claim that their unitsdegrade. Rather than degrade, the SAD fails in a short cmuch lower energy levels than a MOV. A properly consuppressor will not degrade, even when exposed to thohigh-energy strikes. Ask your supplier to provide indepto guarantee the device achieves the published surge cu(and thus the required life expectancy). Degradation prexist with the very inexpensive surge bars. These devicemanufactured offshore and are poorly constructed utiliz

t d MOV Th l lit d i h ld t b

Small MOV (20 mm)La rge S AD ( 5 kW )

S AD F a ilu re

S i licon Av ala nch e Diod e : Not e 52 S ADs ae q ui v al e nt s u rge c u rre nt ra t in g a s th e 1 sillu st ra t e d . F o r a co m p le t e d e v ic e , a s ig n in u m b er o f S ADs a re re q ui re d .

11001 010

1 00

200

3 00

4 00

500

6 00

7 00

V o

l t a g e

( V

)

S u rge C u rre nt ( A)



Myth Number Three : SADs provide tighter clamping than MOVs.

When exposed to IEEE dened test waveforms and UL 1449 testresults, both MOV and SAD devices have the same SuppressionVoltage Ratings. Accordingly, UL does not regard SAD devices asproviding any better clamping than MOV based SPDs.

SummaryThere are a number of myths in the SPD industrSPDs, it is important to evaluate the performancunit and not compare individual internal elemenSPD construction methods and internal wiring/f

critical to overall performance. Independent testcomparing the performance of these units.

Based on the proven track record of performancsuppressors are highly reliable. That is why almstill employ MOV components. For service entrlocations, SADs are not recommended because energy capability. SADs are primarily used to pcommunication wires.

TABLE 7. COMPARISON OF COMPONENTS USED IN SURGE PROTECTION DEVICES

SPD COMPONENT ADVANTAGES AND DISADVANTAGES

Metal Oxide Varsior (MOV) Highest energy capability, excellent reliability and consistent performance, better mechanical conneccomponents. Non-linear clamping curve gradually degrades over repeated use (only at high surge leve

Silicon Avalanche Diode (SAD) Flatter clamping curve, excellent reliability and consistent performance. Very low energy capability, eSelenium Cells Moderate to high-energy capability. Very high leakage current, high clamping voltage, bulky, expensivGas Tubes High-energy capability, very low capacitive (requirement for data line applications). Unpredictable and

“crowbar” to ground (unsuitable for AC systems), expensive.Hybrid SPD MOV/Filter is most common hybrid; incorporates the advantages of other components while overcom

with each individual component (achieves long life expectancy, faster response, better clamping perfowith hybrid SPDs using MOV and SAD, or devices using selenium cells (inability to have the various

Surge Protective Device



gFrequently Asked Questions

1. What are surges (also called transients, impulses, spikes)?An electrical surge (transient voltage) is a random, high energy,short duration electrical disturbance. As shown in Figure 14 , it has avery fast rise time (1 – 10 microseconds). Surges, by denition, aresub-cycle events and should not be confused with longer duration

events such as swells or temporary overvoltages.High-energy surges can disrupt, damage or destroy sensitive micro-processor-based equipment. Microprocessor failure results from abreakdown in the insulation or dielectric capability of the electronics.

Approximately 80% of recorded surges are due to internal switchingtransients caused by turning on/off motors, transformers, photocopi-ers or other loads. The IEEE C62.41 surge standard has created theCategory B3 ringwave and the B3/C1 combination wave to representhigher energy internal surges.

Externally generated surges due to induced lightning, grid switching

or from adjacent buildings account for the remaining recorded surges.The Category C3 combination wave (20 kV, 10 kA) representshigh-energy surges due to lightning. Refer to the CPS Technote#1 for more information on IEEE surge standards.

FIGURE 14. AN EXTERNALLY CREATED ELECTRICAL

SURGE CAUSED BY INDUCED LIGHTNING

2. Why is there a need for Surge Protective Devices?In the coming years, electronic devices will represent half of theelectrical demand in the United States. Electronics, consist of micro-processors which rely on digital signals: fast on/off coded sequences.Distortion on the power or signal lines may disrupt the sensitive sig-nal sequence As electronic components become smaller and more

Microprocessors can be “upset,” “degraded” or “damagsurge events. Depending on the magnitude of the surgeconguration and the sensitivity of the load. Taresults of a major survey conducted by Dranetz on the esurges on different microprocessor equipment.

TABLE 8. SUMMARY OF MAJOR SURVEY RESULTON THE EFFECTS OF SURGES ON DIFFERENTMICROPROCESSOR EQUIPMENT

Source: Dranetz Handbook for Power Quality

Other references for the recommendation of surge protdevices includes:

IEEE Emerald Book (Std. 1100)

FIPS 94

IEEE C62.41

Manufacturers (Allan-Bradley, Motorola, other sup

NEMA LS-1NFPA 780

As a design objective, the IEEE Emerald Book (and thecurve) recommends reducing 20,000 volt induced lightdisturbances down to two times nominal voltage (< 330To achieve this level of performance, surge suppressorsoped. Since the mid-1980s, surge protective devices mo

IMPACT TOELECTRONICLOADS

IMPULSE 4X IMPULSE 2

Circuit Board Failure Yes YesData Transmission Errors Yes YesMemory Scramble Yes YesHard Disk Crash Yes —SCR Failure Yes —Process Interrupt Yes YesPower Supply failure Yes —Program Lock-up Yes Yes



3. Where do I need an SPD? Why do I need to implement a2-stage approach?As recommended by IEEE (Emerald Book 2005), SPDs should becoordinated in a staged or cascaded approach. The starting point isat the service entrance. (Service entrance protection is also required

by NFPA 780.) The rst surge diversion occurs at the serviceentrance, then any residual voltage can be dealt with by a secondSPD at the power panel of the computer room, or other critical load(see Figure 16 ). This two-stage approach will reduce 20,000 voltinduced lightning surges well under 330 volts peak as recommendedby IEEE and CBEMA.

4. Is there a difference between a TVSS andNo, Underwriters Laboratories (UL) uses the teSurge Suppressor (TVSS), while NEMA, IEC aProtective Device (SPD). An SPD/TVSS is a de(reduces in magnitude) transient voltages.

5. How does an SPD work?The design goal is to divert as much of the transaway from the load as possible. This is accomplthe energy to ground through a low impedance psuppressor).

Metal Oxide Varistors (MOVs) are the most relitechnology to reduce transient voltages. Under nMOV is a high impedance component. When susurge (i.e., voltage is over 125% of the nominalthe MOV will quickly become a low impedanceaway from loads. The MOV reaction time is nan1000 times faster than the incoming surge.

In AC power applications, over 95% of SPDs uVaristors (MOVs) because of their high-energy clamping performance. For added performance ancy, a lter element is used in conjunction with

Silicon Avalanche Diodes (SADs) are frequentlyor communication surge protectors. They are nofor use in high exposure AC applications due tocapabilities.

Selenium cells were once used in surge applicatoutdated technology. They were used in the 1920in the 1960s by the more efcient silicon and Mcompany continues to use selenium enhanced suas a marketing ploy to create confusion with engcells are metallic rectiers (diodes) having a mavoltage of 25 Vdc. Many selenium plates are stato create sufcient voltage breakdown for use inWhen mounted in parallel with MOV componeno performance, cost or application advantagesexpensive and add considerable space (which m

more difcult). There are no patents on selenium6. What criteria are important when specifyA specication should focus on the essential peinstallation and safety requirements. A number tions contain misleading criteria that does followother recommended performance standards.

The following are considered essential perform

SPD

S tage 1 P rotection(S er v ice Entrance )

SPD

S tage 2 P rotection(B ranc h L ocation )

480 V 12 0 V /

2 08 VCo mpu terS en s itiv eL oa d s

S y s te m Te s t P ara m eter s :

IEEE C6 2 .4 1 an d C6 2 . 4 5 te s t p roce d u re s u s ing C3 Impu ls e480 V m ain entrance p ane ls ;

100 f eet o f entrance w ire ;

480 / 2 08 V d is tri b u tion tran s f or m er ; an d

12 0 / 2 08 V b ranc h

2 0,000 V

In pu t — h ig h energ y

tran s ient d is tu rb ance :

IEEE Categor y C3 Impu l s e2 0

,000 V

B e s t ac h ie v a b lep er f or m ance w ith s ing le T V SS

at m ain p ane l (800 V at S tage 1 )

T w o s tage (ca s ca d e a pp roac h )ac h ie v e s b e s t p o ss ib le p rotection(le ss th an 1 00 V at S tage 2 )

2 5 u S

T i (M i d )

5 0

Surge Protective Device



Frequently Asked Questions

C. Effective Filter — Noise attenuation at 100 kHz based on theMIL-STD-220 insertion loss test. The attenuation should exceed45 dB (L-N modes). Specify that insertion loss bode plots areprovided as submittals.

D. Integrated Installation — Factory installed as part of the

distribution equipment. Check to ensure the installationminimizes lead length.

E. Internal Fusing — Safety and overcurrent protection. 200 kAICinternal fusing system.

F. Reliability Monitor and Diagnostic System — Foolproof statusindication for each phase. A popular option is to include Form Ccontacts for remote monitoring.

G. Independent Testing — To ensure a reliable construction anddesign, specify that all manufacturers submit results from anindependent test lab verifying the device can achieve the pub-

lished surge current ratings (on a per mode and per phase basis).For more information on specication recommendations or a copy ofsample specication, contact Eaton.

7. What is surge current capacity?Dened by NEMA LS-1 as: The maximum 8/20 us surge currentpulse the SPD device is capable of surviving on a single impulse basiswithout suffering either performance or degradation of more than10 percent deviation of clamping voltage.

Listed by mode, since number and type of components in any SPDmay vary by mode.

The industry standard is to publish surge current “per phase”by summing modes L-N + L-G in a Wye system and L-L + L-G in Deltasystems.

Surge current capacity is used to indicate the protection capability ofa particular SPD design, and should be used on a per phase and permode basis when specifying an SPD for a given application.

Beware: Manufacturers are not required to have their units indepen-dently tested to their published surge current capacity rating. Mostpublished ratings are theoretical, and calculated by summing the

individual MOV capabilities. Manufacturer “A” may claim a rating of100 kA, but due to the poor construction integrity, the unit is unableto share current equally to each MOV. Without equal current sharing,the published surge current rating cannot be met. Speciers shouldrequest that manufacturers submit independent test reports fromlightning labs conrming the published surge ratings.

All Clipper units have been independently tested to meet or exceedtheir published surge current capacities

8. What surge current capacity is required?Surge current capacity is dependent on the application amount of required protection. What is the geographic lfacility and the exposure to transients? How critical is tto the organization (impact of downtime, repair costs)?

Based on available research, the maximum amplitude olightning related surge on the facility service entrance icombination wave (refer to IEEE C62.41). Above this avoltage will exceed BIL ratings causing arcing in the codistribution system.

Eaton recommends 250 kA per phase for service entrantions (large facilities in high exposure locations), and n120 kA per phase at branch panel locations.

If IEEE and other research species the maximum surgewhy do many suppliers, including Eaton, suggest up to

phase device be installed? The answer is reliability, or, ately, life expectancy. By increasing the kA rating of thyou are not increasing performance, but instead the lifeof the suppressor.

A service entrance suppressor will experience thousandvarious magnitudes. Based on statistical data we can delife expectancy of a suppressor. A properly constructedhaving a 250 kA per phase surge current rating will havancy greater than 25 years in high exposure locations.

Beware: Some manufacturers recommend installing

surge current ratings over 250 kA per phase. In fact, somoting ratings up to 600 or 700 kA per phase. This leveridiculous and offers no benets to customers. A 400 kdevice would have approximately 500 year life expectamedium exposure location — well beyond reasonable dters. (Eaton is forced to build higher rated units to meetspecications, however, we strongly recommend that cquestion suppliers who promote excessive ratings for creasons.)

Today’s SPDs will not fail due to lightning surges. Basedecades of experience, the failure rate of an SPD is extr

(<0.1%). Should a suppressor fail, it is likely the result temporary overvoltage (TOV) due to a fault on the utilii.e., the nominal 120 volt AC line exceeds 180 volts (forTOV will damage surge protectors and other electronicthis rare event occur, call your utility to investigate the more information on TOV problems in international enrefer to the IEEE article written by Eaton for the 1997 Iconference, Australia).



9. What is let-through voltage (clamping voltage)?

FIGURE 16. EXAMPLE OF LET-THROUGH VOLTAGES AND DIFFERENT IEEE DEFINED SURGE WAVEFORMS

Let-through voltage is the amount of voltage that is not suppressedby the SPD and passes through to the load. Figure 16 is an exampleof let-through voltage.

Let-through voltage is a performance measurement of a surgesuppressor’s ability to attenuate a dened surge. IEEE C62.41 hasspecied test waveforms for service entrance and branch locations.

A surge manufacturer should be able to provide let-through voltagetests under the key waveforms (i.e., Category C3 and C1 combinationwaveforms; Category B3 Ringwave).

Beware: The UL 1449 (2nd Edition, 1988) conducts a 500 amperelet-through voltage test. This test does not provide any performancedata and is not a key specication criterion.

Clamping voltage is often confused with let-throClamping voltage refers to the operating characOxide Varistor (MOV) component and is not usperformance of an SPD. The clamping voltage i1 mA of current passes through an MOV. Clampnot include the effects of internal wiring, fusingor installation lead length.

Let-through voltage is a more applicable test fothe amount of voltage that is not suppressed by ato an IEEE dened surge waveform and test setu

Surge Protective DeviceF l A k d Q i




10. Why is installation important? What affect does it haveon an SPD’s performance?Installation lead length (wiring) reduces the performance of any surgesuppressor. As a rule of thumb, assume that each inch of installationlead length will add between 15 to 25 volts per inch of wiring.

Because surges occur at high frequencies (approximately 100 kHz),the lead length from the bus bar to the suppression elements createsimpedance in the surge path.

FIGURE 17. ADDITIONAL LET-THROUGH VOLTAGE USING IEEE C1(6000V, 3000A) WAVEFORM (UL1449 TEST WAVE)

As one specier said, “ No matter which TVSS device you buy, it isthe installation requirements/inspection that is the most importantfactor of the surge specication.”

Published let-through voltage ratings are for the device/moduleonly. These ratings do not include installation lead length (whichis dependent on the electrician installing the unit). The actuallet-through voltage for the system is measured at the bus bar

and is based on two factors:1. The device rating (quality of the suppressor).

2. The quality of the installation.

For example, consider an SPD having a 400 volt rating (based onIEEE Cat. C1 test waveform).

Connected to a panelboard with just 14 inches of #14 wire,i t l 300 lt dd d t th l t th h lt

11. Why should suppressors be integrated into thedistribution equipment (panelboards, switchboardMost consulting speciers are now requiring the gear mintegrate the suppressor inside the switchboard, panelboIntegrated suppression offers a number of key bene ts

externally mounted applications:1. Performance — Integrating the SPD into the elect

distribution equipment eliminates the installation ensuring signicantly improved performance (mulet-through values).

2. Control — There is no chance that eld installatioincorrectly. By having the suppressor factory instalthe specier does not have to check the installationcontractor to re-install the device (a costly and timprocess). This reduces future claims and problemsengineer and end customer.

3. Reduce wall space. Integrating the suppressor elimwall space taken up by the externally mounted sup(between 2 and 3 feet!).

4. One source for warranty claims. Should a problemthe customer eliminates potential warranty conicmanufacturers.

5. Reduced installation costs. There is no contractor mounting SPDs.

The Cutler-Hammer Clipper Power System is integrated

low voltage distribution equipment.Through our innovative direct bus bar connection, we llead length between the SPD and electrical equipment. the Clipper Power System carries a UL 1449 let-througrating of 400 V.

Through our “zero lead length” direct bus bar connectia let-through voltage of 420 V at the panelboard bus baperformance advantage over traditional cable connecte

Installation Lead Length Can Increase Let-Through Voltageby 15 to 25 V per Inch

1,000

14 AWG

Installation Criteria O rderof Im portance :

1. Lead Length ó 75% Reduction2. Tw isting W ires ó 23% Reduction3 . Large W ire ó M inim al Reduction

209 V (23 % )

Loose W iring

Additional Let-Through Voltage (Additional to U L 144 9 Rating )

3 f t. Lead LengthTw isted W ires

1 f t. Lead LengthTw isted W ires

6 73 V (75% )

10 AWG

4 AWG

900

8 00

7006 00

500

400

3 00

200

100

0



FIGURE 18. INTEGRATED SPD PERFORMANCE

Some SPD manufacturers have obtained a UL procedure for installingtheir SPD into another manufacturer’s panelboard. When this occurs,the original panelboard manufacturer’s UL label (UL67) is void, as isthe warranty provided by that manufacturer. The SPD manufacturerthen modies and integrates the SPD into its panelboard, and mustassume all warranty and liability issues regarding the panelboardand SPD. In most cases, the original panelboard manufacturer’snameplate data is not removed and replaced by that of the SPD

12. What is the benet of ltering (sine wavFiltering eliminates electrical line noise and ringadding capacitors to the suppression device. (Se

FIGURE 19. INTERNALLY GENERATED RINGWAV

Note: Ringwaves typically resonate within a fabetween 50 kHz and 250 kHz.

FIGURE 20. EMI/RFI ELECTRICAL LINE NOISE

Note: Noise is any unwanted electrical signal tundesirable effects. Noise is typically less than 2

Hybrid SPD — A device that combines the band ltering. A properly designed hybrid SPD wany SPD using only MOVs.

N

G

SPD

N

G

C PS

S ide Mounted SPD- Us ed f o r R et r o f it

Appl ica tion s

SPD Inte g r a ted intoP a ne lb o a r d sS w it ch b o a r d s , M CC s

1000

8 00

6 00

4 00

2 00

0

-2 00

2 0 8 Y/ 1 2 0 P a ne lb o a r d

(Inte g r a ted v s . S ide Mounted SPD )S ide Mounted SPD D e v ice(Ass u m in g 1 4 " Le a d Len g t h to B u s )

C lipp e r : Inte g r a ted SPD

(D ir e c t B u s B a r C onne c tion )

S u r g eE v ent

- 2 .00 0 .00 2 .00 4 .00 6 .00 8 .00 10 .00Mi cr o s e cond s

B ene f it s o f Inte g r a ted (C lipp e r ) :

- L e ss Le a d Len g t h = Lo w e r Let -T h r ou g h Vo lt a g e- E lim in a te s In s t alla tion C o s t s- L e ss W all S pac e- Fac to r y In s t all ed a nd Qu al it y Te s ted- H ig h e r P e rf o r m a n ce

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Surge Protective DeviceFrequently Asked Questions




13. Why joules and response time are irrelevant specications?Joule ratings are not an approved specication for surge protectivedevices. IEEE, IEC and NEMA do not recommend using Joule ratingswhen specifying or comparing surge suppressors because they canprovide misleading and conicting information. For example, on a 120

volt system, a 150 volt or 175 volt MOV could be used. Even thoughthe 175 volt MOV has a higher Joule rating, the 150 volt has a muchlower let-through voltage and offers better surge protection.

FIGURE 21. FILTER PERFORMANCE BASED ON CAT. B3,100 KHZ, 6000 V

Joule ratings are a function of let-through voltage, surge current andsurge duration (time). Each manufacturer may use a different stan-dard surge wave when publishing Joules. Given the confusion regard-ing Joule ratings, the power quality industry does not recommend theuse of Joule ratings in performance specications.

Response Time — All suppressors have sufcient response time toreact to surges. In fact, the MOV will react 1000 times faster than thesurge. NEMA and IEEE do not recommend using “response time” asa performance criteria when comparing SPDs.

14. Is an SPD with replaceable “modules” superionon-replaceable designs?No. Some manufacturers promote a modular design to production costs, and create an “aftermarket business” There are a number of technical aws with many modu

1. If one module is damaged, all modules should be (undamaged modules are stressed and provide unbprotection). Eaton, as well as several other manufarecommend a complete replacement, or replacememodules to ensure safety and reliability.

2. Easy to cheat on performance specications (oftenratings are for an individual module; unit ratings ar

3. Modular designs utilize “Banana” pin connectors modules rather than a low impedance bolt-on con

15. Is maintenance required for an SPD?Maintenance is not a requirement for a quality SPD. A should last over 25 years without any preventive maintgram. Note the recommendations by Dr. Ronald B. Stanauthority on SPDs) in his book “ Protection of EleOvervoltages ” page 229:

“ The protection circuit should require minimal or no romaintenance. Consumable components, such as fuses, shave an indicator lamp to signal the need for replacemeRequiring routine maintenance increases the cost of thecircuits, although the money comes from a different bu

The SPD should come with a diagnostic system that wicontinuous monitoring of the fusing system and protec(including neutral to ground) and be capable of identifyopen circuit failures. The monitoring system should alsa detection circuit to monitor for overheating (in all mothermal runaway.

400

2 00

0

-2 00

-400

-5 0 5 1 0 1 5

Time (Microseconds)

Le t-Th ro ugh Vo ltag e W ith o ut Filter

Le t-Th ro ugh Vo ltag eW ith Filter



16. What is the difference between a Surge Protectorand an Arrestor?Prior to the microprocessor revolution, most electrical devices werelinear loads, relays, coils, step switches, motors, resistors, etc. Utilitycompanies and end users were primarily concerned with preventing

voltage surges from exceeding the Basic Insulation Level (BIL) ofthe conductor wires, transformer windings, and other equipment.Consequently, lightning arrestors were developed for use in low,medium, and high voltage applications. The fact that these devicescreate a “crowbar” between the phase conductor and ground doesnot matter to linear loads, as this is cleared within a few cycles.

Lightning arrestors are still used in the electrical industry primarilyalong the transmission lines and upstream of a facility’s service entrance.Low voltage systems (600 volts and below), now have surge protectorsat the service entrance and branch panels in place of lightning arrestors.Surge protectors offer the following advantages over arrestors:

Low let-through voltage (better performance).Longer life expectancy.

Improved safety (less destructive debris if damaged).

Full monitoring capability.

Internal fusing.

Filtering capabilities to remove low level surge/noise.

17. Does an SPD give me 100% coverage for electrical loads?No! An SPD protects against surges — one of the most commontypes of electrical disturbances. Some SPDs also contain lteringto remove high frequency noise (50 kHz to 250 kHz). They do notprovide ltering against harmonic loads (third through 50th harmonicequals 180 to 3000 Hz).

An SPD can not prevent damage caused by a direct lightning strike.A direct lightning strike is a very rare occurrence; in most caseslightning causes induced surges on the power line which arereduced by the SPD.

There is no device that can prevent damage from direct lightningstrikes.

An SPD can not stop or limit problems due to temporary overvoltage.Temporary overvoltage is a rare disturbance caused by a severefault in the utility power or due to problems with the ground (poor ornon-existent N-G bond). Temporary overvoltage occurs when the ACvoltage exceeds the nominal voltage (120 volts) for a short duration(millisecond to a few minutes). If the voltage exceeds 25% ofthe nominal system voltage, the SPD and other loads maybecome damaged

AbbreviationsANSI American National Standards Institu

CSA Canadian Standards Association

EMP Electromagnetic Pulse

EMI Electromagnetic InterferenceIEC International Electrotechnical Comm

IEEE Institute of Electrical and Electronic

NEMA National Electrical Manufacturers A

RFI Radio Frequency Interference

UL Underwriter Laboratories

LEMP Lightning EMP

NEMP Nuclear EMP

ReferencesInstitute of Electrical and Electronics Engineers100-1988 Standard Dictionary of Electrical and

IEEE - C62 Collection of Guides andSurge Protection

IEEE - C62.41 Guide for Surge Voltages Power Circuits

IEEE - C62.45 Guide on Surge Testing foTo Low Voltage AC Pow

IEEE (Std. 1100) Emerald BookUL 96 Standard For Safety-Insta

for Lightning Protection

UL 452 Standard for Safety-Ante

UL 497A Standard for Safety-SecoCommunication Circuits

UL 498 Standard for Safety-RecePlugs (Including Direct

UL 544 Standard for Safety-Medi

Dental EquipmentUL 1283 Standard for Safety-Elect

Interference Filters

UL 1363 Standard for Safety-Temp(Power Strips)

UL 1449 Standard for Safety-TransSurge Suppressors

Notes





© 2007 Eaton CorporationAll Rights ReservedPrinted in USAPublication No. SA01005003E / Z5867June 2007

CSA is a registered trademark of the Canadian Standards Association.Cutler-Hammer is a federally registered trade-mark of Eaton Corporation. Allen-Bradley is afederally registered trademark of RockwellAutomation. NEMA is the registered trade-mark and service mark of the NationalElectrical Manufacturers Association.NESC is a registered trademark andservice mark of the Institute of Electricaland Electronics Engineers, Inc. NFPA isa registered trademark of the NationalFire Protection Association. Siemens is aregistered trademark of Siemens AG.UL is a federally registered trademarkof Underwriters Laboratories Inc. IEEE is aregistered trademark of The Institute ofElectrical and Electronics Engineers,Incorporated.

Eaton’s electrical business is a global leader in electrical control, power distribution,uninterruptible power supply and industrial automation products and services. Eaton’sglobal electrical brands, including Cutler-Hammer , Powerware , Holec and MEM ,provide customer-driven PowerChain Management solutions to serve the power

system needs of the industrial, institutional, government, utility, commercial,residential, IT, mission critical and OEM markets worldwide.

Eaton Corporation is a diversified industrial manufacturer with 2006 sales of $12.4billion. Eaton is a global leader in electrical systems and components for power quality,distribution and control; fluid power systems and services for industrial, mobile andaircraft equipment; intelligent truck drivetrain systems for safety and fuel economy; andautomotive engine air management systems, powertrain solutions and specialty controlsfor performance, fuel economy and safety. Eaton has 61,000 employees and sellsproducts to customers in more than 125 countries. For more information, visitwww.eaton.com.

Eaton CorporationElectrical Group1000 Cherrington ParkwayMoon Township, PA 15108United States877-ETN-CARE (877-386-2273)Eaton.com

Eaton-Guide-Surge-Suppression.pdf

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