ESP - Introduction

7/29/2019 ESP - Introduction

1/12Furse, Wilford Road, Nottingham, NG2 1EB Tel: +44 (0)115 964 3700 Email: [email protected] Web: www.furse.com

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What transients are and why you need protection

The information provided in these introductorypages follows the requirements for transientovervoltage (surge) protection provided by bothBS EN/IEC 62305 and the latest amendmentof the IET Wiring Regulations 17th Edition,BS 7671:2008(+A1:2011).

Transient overvoltages

Transient overvoltages are short duration, highmagnitude voltages peaks with fast rising edges,commonly referred to as surges. Often described as aspike, transient voltages can reach up to 6000 V on alow-voltage consumer network, with no more thanmillisecond duration.

Lightning strikes are the most common source ofextreme transient overvoltages where total outage of

an unprotected system can occur with damage tocabling insulation through flashover potentiallyresulting in loss of life through fire and electric shock.

However, electrical and electronic equipment is alsocontinually stressed by hundreds of transients thatoccur every day on the power supply network throughswitching operations of inductive loads such asair-conditioning units, lift motors and transformers.

Switching transients may also occur as a resultof interrupting short-circuit currents (such asfuses blowing).

Although switching transients are of a lower magnitude

than lightning transients, they occur more frequentlyand equipment failures unexpectedly occur often after atime delay; degradation of electronic components withinthe equipment is accelerated due to the continual stresscaused by these switching transients.

Transient overvoltages, whether caused by lightning orby electrical switching, have similar effects: disruption(e.g. data loss, RCD tripping), degradation (reducedequipment lifespan), damage (outright equipmentfailure, particularly concerning for essential servicessuch as fire and security alarm systems) and downtime -the biggest cost to any business such as lostproductivity and product spoilage, staff overtime,

delays to customers and sales lost to competitors.

Protection against lightning andswitching transients

BS EN/IEC 62305 takes account of protection measureson metallic service lines (typically power, signal andtelecom lines) using transient overvoltage or surgeprotective devices (SPDs) against both direct lightningstrikes as well as the more common indirect lightningstrikes (often described as the secondary effects oflightning) and switching transients.

Standards such as BS EN 61643 series define the

characteristics of lightning currents and voltages toenable reliable and repeatable testing of SPDs (as wellas lightning protection components).

Although these waveforms may differ from actualtransients, the standardized forms are based uponyears of observation and measurement (and in somecases simulation). In general they provide a fairapproximation of the real world transient.

Transient waveforms have a fast rising edge and alonger tail. They are described through their peakvalue (or magnitude), rise time and their duration (orfall time). The duration is measured as the time takenfor the test transient to decay to half its peak value.

The figures below illustrate the common current and

voltage waveforms that are used to test SPDs formains, signal and telecom lines.

Transient overvoltagedamage to the circuitboard, left, is clear tosee, but most damage

is barely visible, asbelow.

Time t (s)

SurgeVoltage(kA)

0

1

2

3

4

0 300 600 900 1200 1500

1.2/50 s Waveform

10/700 s Waveform

2

Vpeak @t = 50 s

Vpeak @t = 1.2 s

Vpeak @t = 10 s

2

Vpeak @t = 700 s

Figures 1 & 2: The common current and voltage waveforms used to

test SPDs for mains, signal and telecom lines

SurgeCurrent(kA)

0

10

20

30

0 200 400 600

2

800 1000

Time t (s)

8/20 s Waveform

Iimp @t = 350 s

10/350 s Waveform

2

Imax @t = 20 s

Imax @t = 8 s

Iimp @t = 10 s



Remote or indirect lightning flashes near thestructure (Source S2) or near a connected serviceto the structure (Source S4) of up to 1 km radiusaway (and hence far more common) are representedby the 8/20 s waveform.

Induced surges from direct lightning flashes andswitching sources are also represented by thiswaveform.

With a much shorter decay or fall time relative to the10/350 s waveform, the 8/20 s waveform presentssignificantly less energy (for an equivalent peakcurrent) but is still devastating enough to damageelectrical and electronic equipment.

Damped current

waveshape(8/20 s)

Ground Level

StructuralLPS

10/350 ssurge current

(Iimp)

Ground Level8/20 ssurgecurrent

GroundLevel

Induced Surges/Overvoltages

8/20 s surge current Strike up to 1 km away

8/20 s

Ground Level

10/350 ssurge current(Iimp)

(Iimp)

2

(Iimp)

2

BS EN/IEC 62305-1 recognises that failure of internalsystems (Damage Type D3) due to LightningElectromagnetic Impulse (LEMP) is possible from allpoints of strike to the structure or service - direct orindirect (all Sources: S1, S2, S3 and S4).

To ensure continuous operation of critical systems evenin the event of a direct strike, SPDs are essential andare suitably deployed, based on the source of surgeand its intensity using the Lightning Protection Zones(LPZ) concept within BS EN/IEC 62305-4.

A series of zones is created within the structureaccording to the level of threat posed by the LEMPwith each zone to have successively less exposure tothe effects of lightning - for example LPZ 0A (outsidethe structure) where the threat of lightning currentsand fields is most severe being more onerous thanLPZ 3 (within the structure) where the threat of

lightning is considerably reduced such that electronicscan be safely located within this zone.

Lightning currents as a result of direct lightning strikesare represented by the simulated 10/350 s waveformwith a fast rise time and long decay that replicates thehigh energy content of direct lightning.

Direct lightning can inject partial lightning currentsof the 10/350 s waveform into a system where astructure with a structural Lightning ProtectionSystem (LPS) receives a direct strike (Source S1) orwhere lightning directly strikes an overhead serviceline (Source S3).

Figure 3: Illustration of lightning current flow from a direct strike to a

structure (Source S1)

Figure 4: Illustration of lightning current flow from a direct strike to anearby service (Source S3)

Figure 5: Illustration of lightning current flow from a direct strike nearthe structure (Source S2)

Figure 6: Illustration of lightning current flow from lightning flashes

near connected services (Source S4)

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Table 1: Standardized test waveforms with peak currents used to test

SPDs at each LPZ boundary

SPD location/LPZ boundary

LPZ 0/1 LPZ 1/2 LPZ 2/3

Typical SPD

installationpoint

Service Entrance

(e.g. Maindistribution board

or telecom NTP)

Sub-distribution

boardor telecom PBX

frame

Terminal

Equipment(e.g. socket

outlet)

Mains Test

Class/SPD Type1I/1 II/2 III/3

Surge test

waveform

10/350 current 8/20 current Combination

8/20 current and

1.2/50 voltage

Typical peak

test current

(per mode)

25 kA2 40 kA 3 kA (with 6 kV)

Signal/Telecom

Test Category1D13 C23 C1

Surge test

waveform

10/350 current Combination

8/20 current and

1.2/50 voltage

Combination

8/20 current and

1.2/50 voltageTypical peak

test current

(per mode)

2.5 kA 2 kA (with 4 kV) 0.5 kA (with 1 kV)

1 Tests to BS EN 61643 series2 Peak current (per mode) for a 3 phase SPD to protect a TN-S mains system3 Test category B2 10/700 voltage waveform (also within ITU-T standards)

up to 4 kV peak also permissible

Furse, Wilford Road, Nottingham, NG2 1EB Tel: +44 (0)115 964 3700 Email: [email protected] Web: www.furse.com

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What transients are and why you need protection

Figure 7 illustrates the basic LPZ concept defined byprotection measures against LEMP as detailed inBS EN/IEC 62305-4.

Equipment is protected against both direct andindirect lightning strikes to the structure andconnected services, through the use of SurgeProtection Measures (SPM), formerly referred to as aLEMP Protection Measures System (LPMS).

To achieve this reduction in LEMP severity, fromconducted surge currents and transient overvoltages,as well as radiated magnetic field effects, successivezones use a combination of shielding measures,bonding of incoming metallic services such as waterand gas and the use of coordinated SPDs (furtherdetails can be found in the Furse Guide to BS EN 62305Protection against Lightning).

Given that the live cores of metallic electrical servicessuch as mains power, data and telecom cables cannotbe bonded directly to earth wherever a line penetrateseach LPZ, a suitable SPD is therefore needed.

The SPDs characteristics at the boundary of each givenzone or installation location need to take account ofthe surge energy they are to be subject to as well asensure the transient overvoltages are limited to safelevels for equipment within the respective zone.

Types of SPD

BS EN/IEC 62305 deals with the provision of SPDs toprotect against both the effects of indirect lightningstrikes and high-energy direct lightning strikes.

G Direct lightning strikes are protected by lightningcurrent or equipotential bonding SPDs (Mains Type1 SPDs & Signal/Telecom SPDs to Test Category D)

G Indirect lightning strikes and switching transientsare protected by transient overvoltage SPDs (MainsType 2 and Type 3 SPDs and Signal/Telecom SPDs to

Test Category C)

Lightning current or equipotential bonding SPDs

Lightning current/equipotential bonding SPDsare designed to prevent dangerous sparking causedby flashover.

Flashover is caused when the extremely high voltagesassociated with a direct lightning strike breaks downcable insulation. This can occur between the structuralLPS and electrical services and presents a potential firehazard and risk from electric shock.

Table 1, above, details the standardized testwaveforms with peak currents used to test SPDstypically located at each zone boundary.

Boundaryof LPZ 2(shielded room)

Boundaryof LPZ 1(LPS)

Antenna

Electricalpower line

Water pipe

Gas pipe

Telecomsline

Mast orrailing

LPZ 2

B

B

B

B

LPZ 1

Criticalequipment

Equipment

SPD 1/2 - Overvoltage protection

Connected service directly bonded

SPD 0/1 - Lightning current protection

Equipment

LPZ 0

Figure 7: Basic LPZ concept - BS EN/IEC 62305-4



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Transient overvoltage SPDs

Transient overvoltage SPDs are designed to protectelectrical/electronic equipment from the secondary

effects of indirect lightning and against switchingtransients. SPDs should be installed at sub-distributionboards and at equipment level for critical equipment.

BS EN/IEC 62305 refers to the correct application oflightning current and transient overvoltage SPDs as acoordinated set where the service entrance lightningcurrent SPD handles the majority of surge energy andprevents flashover whilst the downstream transientovervoltage SPDs ensure equipment protection bysufficiently limiting the overvoltages.

For further information, please refer to the FurseGuide to BS EN 62305 Protection Against Lightning.

BS EN/IEC 62305-2 Risk Management is used to

evaluate the required level of lightning protectionmeasures necessary to lower the risk of damage to aparticular structure, its contents and occupants to adefined tolerable level.

If the risk evaluation demands that a structural LPS isrequired, then lightning current or equipotentialbonding SPDs are always required for any metallicelectrical services entering the structure.

These SPDs are necessary to divert the partial lightningcurrents safely to earth and limit the transientovervoltage to prevent possible flashover.

They are therefore an integral part of the structural

LPS and typically form the first part of a coordinatedSPD set for effective protection of electronicequipment.

Table 2: General indication of system impairments, of which manufacturers of transient overvoltage protectors should provide details

Protectors for mains supplies Protectors for data lines

Parallel protectorsIn-line

protectors

Low frequency

protectors

Network

protectors

Radio frequency

protectors

Nominal operating voltage

Maximum operating voltage

Leakage current Nominal current rating

Max continuous current rating

In-line impedance

Shunt capacitance

Bandwidth

Voltage standing wave ratio

If the risk evaluation shows that a structural LPS isnot required but there is an indirect risk, anyelectrical services feeding the structure via an overheadline will require lightning current SPDs typicallyinstalled at the service entrance, with coordinatedtransient overvoltage SPDs downstream to protectelectronic equipment.

In order to provide effective protection, a transientovervoltage protector/SPD must:

G be compatible with the system it is protecting

G survive repeated transients

G have a low let-through voltage, for allcombinations of conductors (enhanced SPDs toBS EN 62305)

G not leave the user unprotected, at the end of its

life, andG be properly installed

IMPORTANT

The primary purpose of lightning current orequipotential bonding SPDs is to prevent dangeroussparking caused by flashover to protect against theloss of human life.

In order to protect electronic equipment and ensurethe continual operation of systems, transientovervoltage SPDs are required. BS EN/IEC 62305-4specifically states that a lightning protection system

which only employs equipotential bonding SPDsprovides no effective protection against failure ofsensitive electrical or electronic systems.



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Compatibility

The protector must not interfere with the systemsnormal operation:

G mains power supply SPDs should not disrupt thenormal power supply such as creating followcurrent that could blow supply fuses, or cause highleakage currents to earth

G SPDs for data communication, signal andtelephone lines should not impair or restrict thesystems data or signal transmission

Survival

It is vital that the protector is capable of surviving theworst case transients expected at its installationpoint/LPZ boundary.

More importantly, since lightning is a multiple event,the protector must be able to withstand repeatedtransients.

The highest surge currents occur at the serviceentrance (boundary LPZ 0A to LPZ 1). For buildings witha structural LPS, the lightning current SPD could besubject to as high as 25 kA 10/350 s surge currents permode on a 3-phase TN-S/TN-C-S mains system (up to2.5 kA 10/350 s per mode on a signal or telecom line)for a worst-case lightning strike of 200,000 A.

However, this 200 kA level of lightning current itself isextremely rare (approx. 1% probability of occurring)

and the peak current the SPD would be subject tofurther assumes that a structure is only fed with onemetallic service.

Almost all structures have several metallic servicesconnected to them such as gas, water, mains, data &telecoms.

Each service shares a portion of the lightning currentwhen the protected building receives a strike, greatlyreducing the overall current seen by any single service,and as such any SPD fitted to the electric service lines.

Transient overvoltages caused by the secondary effectsof lightning are considerably more common (lightningflash near a connected service up to 1 km away from

the structure) and therefore are unlikely to havecurrents exceeding 10 kA 8/20 s.

Let-through voltage

The larger the transient overvoltage, the greater therisk of flashover, equipment interference, physicaldamage and hence system downtime.

Therefore, the transient overvoltage let through theprotector (also known as the voltage protection level

Up of the SPD) should be as low as possible andcertainly lower than the level at which flashover,interference or component degradation may occur.

Transient overvoltages can exist between any pair ofconductors:

G phase to neutral, phase to earth and neutral to

earth on mains power suppliesG line to line and line(s) to earth on data

communication, signal and telephone lines

Thus, a good protector (enhanced SPDs toBS EN 62305) must have a low let-through voltagebetween every pair of conductors.

Enhanced performance SPDs - SPD*

BS EN 62305-2 details the application of improvedperformance SPDs to further lower the risk fromdamage.

The lower the sparkover voltage, the lower the chanceof flashover causing insulation breakdown, electricshock and fire.

SPDs that offer lower let-through voltages furtherreduce the risks of injury to living beings, physicaldamage as well as failure and malfunction of internalsystems.

All Furse ESP protectors offer such superior protectionand are termed as enhanced performance SPDs (SPD*)in line with BS EN 62305.

Enhanced SPDs can also satisfy more than one testclass/category by handling both high-energy partiallightning currents of 10/350 s waveshape whilstoffering very low let-through voltages.

Such enhanced SPDs may be suitable for changing alightning protection zone from LPZ 0A right through toLPZ 3 at a single boundary or installation point.

As such they provide both technical and economicadvantages over standard SPDs.

End of life

When an SPD comes to the end of its working life itshould not leave equipment unprotected.

Thus in-line protectors should take the line out ofcommission, preventing subsequent transients fromdamaging equipment.

SPDs for data communication, signal and telephonelines and protectors for low current mains powersupplies are usually in-line devices.

Where SPDs are installed at mains power distributionboards it is usually unacceptable for these to suddenlyfail, cutting the power supply.

Consequently, to prevent equipment being leftunprotected, the SPD should have a clear preend-of-life warning, which allows plenty of timefor it to be replaced.

How to get effective protection



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Installation

The performance of SPDs is heavily dependent upontheir correct installation. Thus, it is vital that SPDs are

supplied with clear installation instructions.The following is intended to supplement the detailedguidance given with each product in order to give ageneral overview of installation.

This should not be viewed as a substitute for theInstallation Instructions supplied with the SPD. Copiesof these are available separately on request.

Installing parallel connected SPDs for mainspower supplies:

G SPDs should be installed very close to the powersupply to be protected, either within thedistribution panel or directly alongside of it (in

an enclosure to the required IP rating)

G Connections between the SPD and phase(s), neutraland earth of the supply should be kept very short(ideally 25 cm or less, but no more than 50 cm)

G SPD performance is further enhanced by tightlybinding connecting leads together (simply usingcable ties or similar), over their entire length

G For safety and convenient means of isolation, thephase/live connecting leads should be suitablyfused using HRC fuses or switchfuse, MCB or MCCB

Installing in-line SPDs for data, signal, telephoneor power:

G SPDs are usually installed between where cablingenters or leaves buildings and the equipment beingprotected (or actually within its control panel)

G The installation position should be close to thesystems earth star point (usually the mains powerearth) to enable a short and direct connectionto earth

G In-line, or series, connected SPDs generally haveconnections marked line and clean.

The line end of the SPD should be connected to theincoming or dirty line (from where the transientis expected).

The clean end of the SPD should be connected tothe line or cable feeding the equipment

G Cables connected to the SPDs clean end shouldnever be routed next to dirty line cables or theSPDs earth bond

G Unless ready-boxed, SPDs should be installedwithin an existing cabinet/cubicle or in anenclosure to the required IP rating

Note: further information on the satisfactoryinstallation of SPDs on mains power supplies, tomeet the requirements of IET Wiring Regulations17th Edition, BS 7671:2008(+A1:2011), can be foundon page 288.

How to apply protection

Transient overvoltages are conducted into the sensitivecircuitry of electronic equipment on power and data

communication, signal and telephone lines. Protectionis recommended for:

G all cables which enter or leave the building (exceptfibre optic)

G the power supply local to important equipment

G electronic equipment outside the main building(s)

Protect incoming and outgoingelectrical services

Lightning strikes between clouds or to ground (andobjects upon it) can cause transient overvoltages to be

coupled on to electrical cables, and hence into thesensitive electronic equipment connected to them.

To protect the electronic equipment inside a building,all cables that enter or leave the building must beprotected. Cables leaving the building can also providea route back into the building for transients.

For each building protect incoming/outgoing:

G mains power supplies (including UPS supplies)

G data communication and local area network cables

G signal, control, instrumentation and alarm lines

G CCTV, satellite, TV and antenna cables

G telephone and telemetry lines

Protect the power supply locally toimportant equipment

In addition to installing protection on the mains powersupply as it enters/leaves the building, protectionshould also be installed locally to importantequipment. Protection at the main LV (low voltage)incomer(s) is necessary to prevent large transients fromentering the buildings power distribution system,where they could have farreaching effects.

However, where the cable run to equipment exceeds

10 metres (to BS 7671 Clause 534.2.3.1.1), transientovervoltages may appear on the mains after theprotector at the main LV incomer. These transients canresult from:

G the electrical switching of large inductive loadswithin the building

G a lightning strike to the building - as lightningcurrents flow through down conductors transientovervoltages can be induced on to nearby powercables

G the natural inductance and capacitance of longcable runs, `amplifying the voltage `let-throughthe protector at the main LV incomer

Additionally, local protection guards against thepossibility of a supply which enters/leaves the buildingbeing overlooked and left unprotected.



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When & where to protect

Protect data lines locally

Generally, the biggest risk to data, signal, telecom andnetwork wiring is associated with cables that enter and

leave the building.These should always be protected. However, datacables within a building can additionally havetransients induced on to them when loops betweendata and power cables pick up voltages from themagnetic field caused by a lightning strike.

As part of the overall SPM, BS EN/IEC 62305 advocatesthe use of metal in the structure, and a Faraday cagelightning protection system to help exclude magneticfields.

Cable management practices eliminate loops byrouteing data and power cables along the samegeneral path.

In these cases, the need for local data line protection isminimal. However, where these steps are not possible,data line protection, local to the equipment requiringprotection, should be considered.

Special product development

Whilst this catalogue focuses on our standard product

range which meets a wide variety of applications, onoccasion a customer will have a special requirementwhich needs transient overvoltage protection.

In these circumstances we have the technical capabilityin-house to design and propose a specific solution tomeet the customers special requirement.

Following our proposal, technical and performanceparameters of the SPD can be finalised, and the specialproduct manufactured to order.

Special products completed to date include:

G Low-current supply protection to industrialmicrowave ovens

G Media distribution protection (TV/Radio/DAB on19 rack)

G Integrated photovoltaic inverter protection

G Overvoltage disconnect for battery-chargerinstallations within substations

For more information about special productdevelopment, or to discuss a particular project,please contact us.

Protect electronic equipment outsidethe building

Onsite or field-based electronic equipment with mains

power, data communication, video, signal or telephoneline inputs will need to be protected against transientovervoltages. It may be helpful to think of eachequipment cabinet or cubicle as a separate buildingwith incoming/outgoing cables to be protected.

Complementary techniques

As well as the use of transient overvoltage protectors,BS EN/IEC 62305 outlines additional protectiontechniques (e.g. shielding measures), which can beused to help reduce the transient threat as part of theoverall SPM.

These are described further in the Furse Guide toBS EN 62305 Protection Against Lightning. Wherethese can be used, principally on new build orrefurbishment projects, they need to be supported bythe use of SPDs.



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Furse, Wilford Road, Nottingham, NG2 1EB Tel: +44 (0)115 964 3700 Email: [email protected] Web: www.furse.com

SPD terminology

Nominal Voltage Uo is the phase to neutral AC RMSvoltage of the mains system (derived from thenominal system voltage) for which the SPD is designed.Uo is the voltage by which the power system isdesignated - e.g. 230 V.

Maximum Continuous Operating Voltage Uc is themaximum RMS voltage that may be continuouslyapplied to the SPDs mode of protection e.g. phase toneutral mode. This is equivalent to the SPDs rated

peak voltage.

Temporary Overvoltage UT is the stated test value ofmomentary voltage increase or overvoltage that thepower SPD must withstand safely for a defined time.

Temporary overvoltages, typically lasting up to severalseconds, usually originate from switching operations orwiring faults (for example, sudden load rejection,single-phase faults) as well as mains abnormalities suchas ferro-resonance effects and harmonics.

Impulse Current Iimp is defined by three parameters, acurrent peak with a charge and a specific energytypically simulated with the 10/350 s waveform torepresent partial lightning currents.

This waveform is used, with peak Iimp current valuestated, for the mains Type 1 SPD Class I test andtypically for data/telecom SPD Test Category D.

Nominal Discharge Current In is a defined nominalpeak current value through the SPD, with an 8/20 scurrent waveshape. This is used for classification ofmains SPDs (Class II test) and also for preconditioningof SPDs in Class I and Class II tests. (Note: withinBS 7671, In is referred to as Inspd).

Maximum Discharge Current Imax is the peak currentvalue through the SPD, with an 8/20 s waveshape.

Imax is declared for mains Type 2 SPDs in accordance tothe test sequence of the Class II operating duty test. Ingeneral, Imax is greater than In.

Combined Impulse Test with Open Circuit Voltage Uocis a hybrid 1.2/50 s voltage test combined with an8/20 s current.

The test is performed using a combination wave

generator where its open circuit voltage is defined asUoc, typically 6 kV 1.2/50 s for the mains Class III testand up to 4 kV 1.2/50 s for signal/telecom TestCategory C.

With an impedance of 2 , the generator alsoproduces a peak short circuit current (sometimesreferred to as Isc) at half the value of Uoc (3 kA 8/20 sfor the mains Class III test and up to 2 kA 8/20 s forsignal/telecom Test Category C).

With both voltage and current test waveforms, thecombined impulse test is designed to stress alltechnologies used within SPDs.

Voltage Protection Level Up is the key parameter thatcharacterizes the performance of the SPD in limitingthe transient overvoltage across its terminals. A lowprotection level value (also known as let-throughvoltage) is therefore particularly critical for theeffective protection and continued operation ofelectronic equipment.

The peak voltage protection level Up is declared whenthe SPD is tested with its stated nominal dischargecurrent In (or the peak current (Ipeak) of Iimp) and is alsodeclared when the SPD is subject to combined impulse

test (mains Class III test for Type 3 SPDs) as well asdata/telecom Test Categories C and B.

Common terminology and definitions

The following common terminologies, as recognised by BS EN/IEC 61643, are used throughout SPD specifications inorder to aid correct selection and are defined as follows:



Simplified product selection

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All Furse ESP products are designed to provide simplesystem integration whilst achieving highest levels of

effective protection against transients.Tested in line with the BS EN 61643 standards series, ESPprotection can be selected and applied to BS EN 62305and BS 7671 easily using the SPD product applicationtables and data sheets. Key product and applicationfeatures are represented using the following symbols:

Lightning Protection Zone (LPZ) details theboundary (to BS EN/IEC 62305-4) or installationpoint of the SPD. For example, LPZ 0A 3 signifiesthat the SPD can be installed at the service entranceboundary and create an immediate LPZ 3 suitablefor protecting electronic equipment close to the

SPD installation.Equipment further downstream of this location mayrequire additional protection, against switchingtransients for example.

Mains Test Type defines the Type of mains SPD(BS EN 61643 Type 1, 2, 3 or I, II, III to IEC 61643)tested with the respective test Class I (highenergy 10/350 s current waveform), II (8/20 scurrent waveform) or III (combined 8/20 scurrent and 1.2/50 s voltage waveform) from theBS EN/IEC 61643 series.

Where more than one Type is stated (for combined,enhanced Type SPDs), the SPD has been tested toeach respective test Class, with the results detailedon its transient performance specification.

Signal/Telecom Test Category indicates the TestCategories (as defined in BS EN/IEC 61643 series)that SPDs for signal and telecom systems have beensubject to, with the results detailed on the transientperformance specification.

Test Category D is a high-energy test typically usingthe 10/350 s current waveform. Test Category C is afast rate of rise test using the 1.2/50 s voltagewaveform combined with 8/20 s current waveform.Test Category B is a slow rate of rise test using the10/700 s waveform, also used within ITU standards.Enhanced SPDs tested with categories D, C and B

can offer up to LPZ 0A 3 protection.

Common Mode signifies that the SPD specificallyoffers protection on conductors with respect toearth. For a mains system, this would be betweenphases and earth or neutral and earth. For adata/telecom line this would be between signalline(s) to earth.

Common mode surges can result in flashover if theinsulation withstand voltage of connected wiring orequipment is exceeded. Flashover could lead todangerous sparking potentially causing fire orelectric shock risks. Equipotentially bonding Type 1mains SPDs or Test Cat D tested signal/telecom SPDs

reduce the risk of flashover by limiting commonmode surges.

Full Mode means that the SPD protects in allpossible modes; common mode ( live conductorswith respect to earth) and differential mode(between live conductors). For example, full modemains SPDs offer protection between phase(s) toearth, phase(s) to neutral and neutral to earth.

Whilst common mode protection ensures flashoveris prevented, differential mode protection is criticalto ensure sensitive electronics are protected as wellas operational during surge activity.

Enhanced SPDs (SPD* within BS EN 62305 series)have lower (better) let-through voltage orprotection levels (Up) and therefore further reducethe risk of injury to living beings, physical damageand failure of internal electronic systems.

Enhanced Type 1 mains SPDs (for a 230/400 Vsystem) should have a protection level Up of nomore than 1600 V whilst Type 2 and Type 3 mainsSPDs should have a protection level Up of no morethan 600 V in all modes when tested in accordancewith BS EN 61643 series. Enhanced signal/telecomSPDs should typically have a protection level Up nomore than twice the peak operating voltage of theprotected system.

Status Indication for mains wire-in powerdistribution SPDs is essential as they are installed inparallel or shunt with the supply and as such couldpotentially leave the system unprotected should theSPD fail. 3-way status indication of the SPDscondition provides simple and clear visual inspectionand further provides advanced pre-failure warningsuch that the system is never unprotected.Furthermore warning of potentially fatal neutral to

earth faults due to incorrect earthing and wiringfaults for example is provided with additionalflashing indication.

Remote Indication is an innovative feature thatfurther optimizes mains wire-in SPD protection.A parallel or shunt installed SPD has additivelet-through voltage because of its connecting leadsthat need to be kept as short as possible - ideally nomore than 25 cm. Often an SPD cannot be mountedin its optimum position without compromising thevisibility of its status indication.

Innovative remote status indication displaysovercome this by allowing the SPD to be mountedwith short connecting leads with the separate statusdisplay being conveniently mounted in a visibleposition such as the front of a power distributioncabinet providing convenient and effectiveequipment protection.




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Replaceable Protection Module indicates that theSPD component providing protection can be easilyremoved and replaced following end-of-life with anappropriate replacement module, saving on

reinstallation time and protector cost.The replaceable module includes a quick releasemechanism allowing partial removal, whichfacilitates line commissioning and maintenance.

LED Optional Indication is an additional featurewhere an SPD can be supplied with an integral LEDwhich indicates performance or fault when installedin low current DC power applications.

This enables rapid assessment and replacement ofSPDs in situations where a considerable number ofSPDs are installed.

High Bandwidth SPDs ensure the full system

frequency range of transmission signals, forprotected data communication, signal andtelephone lines, is not impaired.

Signal frequencies outside the stated SPDbandwidth may potentially be distorted causinginformation loss or corruption.

As the SPD should accommodate the characteristicsof the protected system, the stated SPD bandwidth(typically quoted for a 50 system) should alwaysexceed the protected systems bandwidth.

BX IP is an International Protection (IP) rating (toBS EN/IEC 60529) for ready-boxed (BX) SPDstypically used in dusty and damp environments.

The IP rating system (also interpreted as IngressProtection) classifies the degrees of protectionprovided against the intrusion of solid objects(including body parts like hands and fingers), dust,accidental contact and water in electricalenclosures. For example, an IP66 rated enclosureprovides no ingress of dust and therefore completeprotection against contact as well as against waterprojected in powerful jets against the enclosurefrom any direction with no harmful effects.

Unboxed SPDs should be installed withindistribution panels/cabinets or within externalenclosures to the required IP rating (such as theFurse weatherproof WBX enclosure range).

Ultra Slim 7 mm Width highlights the Slim Linefeature of our new ESP SL range which permitsinstallation in tight spaces, or multiple installationwhere a high number of lines require protection.

ATEX/IECex Approved indicates that this SPD hasundergone the relevant testing and approvalprocess defined by ATEX/IECex, and has provensuitable for use in the hazardous environment asdefined on the SPD datasheet.

Active Volt-free Contact is an essential addition tothe visual 3-way status indication.

The changeover volt-free contact is simplyconnected or linked to an existing building

management system, buzzer or light and should theSPD have a pre-failure condition, this would beremotely indicated - particularly important forremote installations where the buildingmanagement system would be connected to atelecom modem.

Active contacts further enable the SPD to alsoconveniently warn of phase loss from a powerfailure or blown fuse.

Intelligent Display iD is an innovation from Fursethat encompasses existing features of 3-way SPDstatus indication with Neutral to Earth voltagewarning but through clear easy to read text on an

illuminated LCD display.Often SPDs should be mounted on their side inorder to facilitate short connecting leads for betterprotection levels but as this compromises theposition and appearance of the status indication, itis not widely practiced.

Also available in a remote display option, the iDfeature enhances mains wire-in SPD installation asthe status indication text can easily be rotated (in90 steps, clockwise) at the push of a button to aidgood installation practice.

Current Rating indicates the maximum continuouscurrent rating of in-line SPDs for data communication,

signal and telephone lines.The SPDs quoted maximum continuous current ratingshould always exceed the peak running current of theprotected system to ensure normal system operationis not impaired.

Damage, through overheating, would result if itsquoted current rating were exceeded.

Low In-line Resistance states the resistance value inOhms () per line of SPDs for data communication,signal and telephone lines.

A low in-line resistance is desirable; particularly forsystems with high running currents in order toreduce any voltage drops across the SPD and ensure

normal system operation is not impaired.

Consideration should be made for additional SPDsinstalled on the same line to protect connectedequipment at each end of the line (e.g. CCTVcamera and connected monitoring equipment) asthe in-line resistance of each SPD is introduced intothe system.



Electronic systems protection Product selector

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Protect incoming and outgoingelectrical services

Well start by considering the main (office) buildingin isolation.

Incoming mains power supplies

Install protection on the incomingmains power supply at the incomingdistribution board(s).

If, as in this example, there are anyother power supplies entering thebuilding install protection on thesenear where they enter the building.

Outgoing mains power supplies

Outgoing supplies can provide

transient overvoltages with a routeback into the buildings powerdistribution system.

Install protection on supplies to otherbuildings. (Note how, if correctlypositioned, the protector at theincoming distribution board (1), alsoprotects against transients from theoutgoing supply to the UPS building).

Install protection on outgoing suppliesto site services, such as CCTV systemsand site lighting.

Protect all incoming/outgoing data communication,

signal and telephone lines (unless fibre optic).

Telephone lines

Incoming telephone lines andextensions that leave the buildinghave protectors installed on them atthe PBXs distribution frame.

In our example, there is a direct (i.e.not via the PBX) telephone line to an

alarm panel, which also needsprotecting.

Weve described in the ESP introduction how protection should be installed on all cables which enter or leave thebuilding (except fibre optic), the power supply local to important equipment and electronic equipment outside themain building(s). With the aid of the illustration we can see how this might be applied in practice.

Data & signal lines

Protectors are installed on CCTV videocables from outdoor cameras toprevent damage to the control desk.

A protector is installed at the networkhub to protect it from transients onthe between building data link.

Equipment such as our RF receiver,with antenna (or satellite) links willalso need protecting.


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Protect electronic equipmentoutside the building

Electronic equipment outside the main building in

ancillary buildings, on site or in the field should alsobe protected.

Protect outdoor CCTV cameras withprotectors on the power supply, andvideo cable (and, if relevant, telemetrycontrol line).

If the UPS is housed in a separatebuilding with a separate earth,incoming and outgoing supplies willneed to be protected. This is becausemost modern UPS systems contain

electronics that make them vulnerableto being disabled by transient overvoltages. To preventtransient overvoltage damage to the UPS it must havea protector installed on both its input and output(outgoing the building). A protector will also need tobe installed on the power supply into the mainbuilding (2).

Protection is also installed on mainspower, data communication andtelephone lines entering theneighbouring building. Additionalprotection (not shown) may be

required within this building (whetherits a computer-controlled warehouse or automatedmanufacturing operation with PLCs, drives andcomputer controls).

Product selector

(1) Mains wire-in protectors p182-195

(2) Mains wire-in protectors p186-189,192-193



(5) PBX telephone/ISDN line protection p236-237

(6) Plug-in telephone line protection, or p234-235Wire-in telephone line protection p204-205,210-211

(7) CCTV video protectors p256-257

(8) Computer network protector p238-239

(9) RF signal protector p258-261

(10) Mains wire-in protector p186-189,192-193

(11) Plug-in mains protector p200-201

(12) Protectors forlow current mains power supplies, p198-199CCTV video and p256-257telemetry lines p204-209

(13) Mains wire-in protectors p182-195(14) Mains wire-in protectors p182-195

Computer network protector p238-239PBX telephone/ISDN line protection p236-237

Product selector Electronic systems protection

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Protect the power supplylocally to important equipmentWithin the building transient overvoltages can be

injected on to the mains power supply (downstreamof the protector at the incomer). Consequently,protectors should be installed close to important piecesof equipment.

Protection is installed on the localdistribution board feeding the serversand network hub. (Note how the topfloor PC network and RF receiver isprotected by the protector on thedistribution board (2)).

The telephone PBX is protected locallyby a plug-in protector.

Mains power

RF

Computer network

Telephone line(s)

Signal line

CCTV video

This illustration is designed to demonstrate the main aspects and

individual components of an electronic systems protection solution.

It is not intended to represent an actual scheme conforming to a

particular code of practice. The drawing is not to scale.

This illustration is designed to demonstrate the main aspects and

individual components of a system of Surge Protection Measures(SPM). It is not intended to represent an actual scheme conforming

to a particular code of practice. The drawing is not to scale.

ESP - Introduction

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Transcript of ESP - Introduction