Earth Leakage Protection

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Schneider Electric

DITED198106enART 07120

M9D

P15

en

The low voltage technical newsletterprotection

earth leakage

1

How to protectpersons andequipment?

TechnologyAn electromechanicalor an electronic relay?

/ p. 5

PracticalEarthing systems

/ p. 7

TipsInstallationsrecommendations

/ p. 10 - 11

The SchneidersolutionsFrom the residual current relaywith separate toroid to the residualcurrent circuit-breaker: all the lowvoltage protection solutions

/ p. 14 - 23

We do more with electricity

L’électrocutionA few milliamps suffice to seriously harm the human body. Electrocution canoccur either by direct contact with an electric cable or a live device, or byindirect contact, if the person touches an accidentally energised metal part.

The physiological reactiondepends on:■ the contact voltage■ the type and duration of thecontact■ the age and vulnerability ofthe subject.

installation standardsin each country for K(normally 0.6)).

Electrodynamicwithstand capacityShort-circuit protectionmust be provided bythe short-circuitprotection deviceplaced upstream.However, it isaccepted, when the

Practical

A few installation tips

2

All electrical installations produce current flows. Even small flows present non-negligiblerisks which can cause serious damage.

Fire30% of fires inindustrial and domesticbuildings are the resultof an electrical fault, themain cause of which isdeterioration of a cableinsulator due tooverheating oraccidental knocking.

23protectionearth leakage

Current ratingChosen according tothe current flowingthrough it.■ if the residualcurrent circuit-breakeris placed downstreamof a circuit-breaker andon the same circuit,the rated currents ofboth devices are atmost the same: Ib > Ia.■ if it is placed

upstream of a group ofcircuits, its ratedcurrent is chosen sothat:Ic = K(Id + Ie + If + Ig).K is the “coincidence”factor which takesdevice efficiencyand power intoaccount, as well astheir utilisation andextension factors(comply with applicable

residual current circuit-breaker and thedownstream short-circuit protectiondevices are in thesame switchboardproduced according tostandards, that theshort-circuit currentwithstand of theresidual current circuit-breaker may also beprovided by the

■ ID/RCCB/FI■ 4 poles■ rating: 25 to 100A■ voltage rating: 400 VAC■ sensitivity: 30 to 1000 mAinstantaneous or selective S

■ ID/RCCB/FI■ 2 poles■ rating: 25-80 A■ voltage rating: 230 VAC■ sensitivity: 10 to 500 mAinstantaneous or selective S

■ ID/RCCB/FI■ 2 or 4 poles■ rating: 100A and 125A■ voltage rating: 230/400 VAC■ sensitivity: 30 to 300 mAinstantaneous or selective S

downstream short-circuit protectiondevices.In this case,coordination isnecessary between theshort-circuit protectiondevice and the residualcurrent circuit-breaker.

Equipements électriques :

The riks

earth leakage current ≥ 500 mA + load current

overcurrent

insulator temperature rise

the insulator melts and strips the conductor

accident

LoaddestructionSome electrical devices deteriorate overtime and may present insulation faults.Insulation faults have many causes:■ heat generated by device operation■ overcurrent■ aggressiveness of the environment■ material wear and loss of tightnessApart from load destruction, there is a riskof electrocution and fire.

and their consequences

Electrical equipment:

1 A cardiac arrest

75 mA irreversible cardiacfibrillation threshold

30 mA respiratory paralysisthreshold

10 mA muscular contraction(tetanisation)

0,5 mA very slight sensation

Enclosure installation datamain device function Vigi module DPN Vigi ID

incomer ■ ■ ■

single-phase outgoer ■ ■ ■

other outgoer ■ ■ ■

■ ■ ■breaking capacity function of associated 3000 A - 4500 A must be obtained by cascading

circuit-breaker (3 kA à 25 kA) or 6000 A with upstream circuit-breaker

max. rating 125 A 40 A 125 A

3

How does earth leakage protection work? P. 4

Detection / Measurement / Tripping

An electromechanical or an electronic relay? P. 5

Two different technologies

Coordination of residual current devices P. 6

Coordination of earth leakage protectionsCoordination of overcurrent protections (of residual current circuit-breakers)

Choosing the right protection P. 8

Protection by residual current circuit-breakerProtection by one-piece phase neutral residual current deviceProtection by an earth leakage module combined with or built into a circuit-breakerGround fault protection built into a power circuit-breaker

Installation recommendations P. 10-11

How to make a reliable installation?Protection against indirect contactProtection against the risk of fireHow to protect loads?

Schneider low voltage earth leakage protection P. 12-13

Installation recommendation: an exemple of a solution

The product pages P. 14-23

How toprotectpersonsandequipments?When confrontedwith the riskof electrocution,destructionof loads and fire,two different butcomplementaryapproaches enableimplementationof effective protection.

1Prevention:prevent the faultfrom occuringThis approach mainlyconcerns new electricalinstallations. Technicalprogress and applicationof strict standards area major assetfor the commissionningof efficient, reliableinstallations.

2 Action: detectand neutralisefaults.

Contentsearth leakage protection

22

Technical data■ nuisance tripping:All the multi 9 residual current devices are immunised by aninterference suppression device which removes the risk of nuisancetripping caused by:■ sudden voltage variations (atmospheric overvoltages, deviceswitchings),■ or by current variations (highly capacitive circuits).

The “ si ” range is designed to maintain optimum safety and continuityof supply of networks in installations disturbed by:■ extreme atmospheric conditions,■ loads generating harmonics,■ transient switching currents.

■ The residual current circuit-breakers meet current standards:IEC 1008, EN61008.

Operating principleIn addition to leakage current detection, the residual current circuit-breaker can be used to open, close or isolate a circuit. It has noshort-circuit or overload protection, and as such must be protected byan upstream circuit-breaker.Its main function is to protect a set of feeders, each equipped withcircuit-breakers.Use of the residual current circuit-breaker is recommended to provideearth leakage protection of an existing installation, already equippedwith circuit-breakers.Consequently, particularly used for domestic, tertiary and smallindustrial applications, its advantage is that it can provide completesafety of sensitive circuits at a low cost, for example in a kitchen orbathroom, a shop where there are risks for customers, damp workingpremises and premises with an aggressive environment.

Residual current

Thesolution:The Schneiderrange of earthleakage protectionproducts.

circuit-breakers

protectionearth leakage

4

Leakage current risksAll LV electrical installations have earth leakage currents. Due partly to conductor capacitance, theyincrease when class 1 devices or motors with limited insulation are used.An occasional earth leakage current greater than merely 500 mA can generate a sufficient overcurrent for theinsulator to heat, melt and start stripping the conductor.The leakage current flowing through the damaged insulator creates an electric arc the intense heat of whichignites the insulator and starts a fire.

The principle of Schneider’s earth leakage protection is based on a system performingthree successive functions virtually instantaneously: detection of a leakage current,measurement of this current and trip opening of the faulty circuit.

DetectionA current transformer is used whose primary windings are thephase(s) and the neutral of the circuit to be protected. The windingdirection is such that the load and neutral currents cancel oneanother out. The appearance of a leakage current destroys thisbalance and generates a current at the secondary winding known asa residual current.

MeasurementAn electromechanical relay is used which compares the electricsignal to a pre-set limit: the tripping threshold, also known assensitivity.

■ a permanent magnet holds in the “ closed ” position a swivel plateconnected to a tripping mechanism.

■ opposite this, an electromagnet supplied by the residual current,and a taut spring have a joint effect on plate opening.

As long as the strength of the permanent magnet (defined accordingto required system sensitivity) is greater than that of the spring andthe electromagnet, the circuit is closed.

TrippingAs soon as the residual current is high enough to cancel the effect ofthe permanent magnet, the spring causes the plate to swivel whichthen strikes the trip opening mechanism of the faulty circuit.

earth leakage protection work

Howdoes

detection

outgoingcurrent

returncurrent

current variation = 0

S N

current variation

measurement

= 0

tripping

current variation ≠ 0

SN

Detection

Measurement

Tripping

21

PracticalIn the IT earthingsystem, there is aneed to providedetection ofovercurrent on theneutral conductorof all circuits,causing breakingof all live conductors,including the neutralconductor.This protection is not

necessary if:■ the neutralconductor is

protected againstshort-circuitsby a device placedupstream;■ the circuit is partof final circuits,of buswaysof the same type,of identical or verysimilar cross-section, and if theassembly is

whose ratedresidual currentis at most equalto 0.15 timesthe acceptablecurrentin the conductor withthe smallest cross-section.

N

residualcurrentdevice

plug lighting heatingsystem

DPN DPN DPN

L1L2L3

N L1 L2 L3

N

DPN DPN

Residual current device or residual current circuit-breaker

L1L2L3

N L1 L2 L3

protected by anearth leakageprotection device


■ Declic Vigi■ rating: 6 to 32 A■ voltage rating: 230 V CA■ breaking capacity: 3000 A

■ DPN Vigi■ rating: 6 to 40 A■ voltage rating: 230 V CA■ breaking capacity: 6000 A


incomer ■ ■ ■






Residual current

5

Schneider proposes two technologies: electromechanical and electronic. The technologicalchoice depends on the specific features of your installation. In compliance with thestandard, Schneider recommends:■ a residual current device with electromechanical relay for unmonitored distribution(domestic applications and equivalent).■ a residual current device with electronic relay for monitored distribution (applicationsbenefiting from a maintenance service).

S N

tripping

outgoingcurrent

returncurrent


The residual currentdevice withelectromechanical relayThis device operates without anyauxiliary source of supply. The energysupplied by the toroid energises anelectromagnet whose moving part ismaintained in the closed position by apermanent magnet.■ fault current energy is the direct cause oftripping. This is the most reliable technologyas it works regardless of fault origin.■ user safety is top priority, and should notbe dependent on quality of the network(public/private), installation age, the neutralsystem chosen or the mechanism reset.

The residual currentdevice with electronicrelayThis device operates with an auxiliarysource of supply. The electrical energysupplied by the toroid is amplified by theelectronic board, in turn supplied by asource dependent on network voltage.Fault detection causes the breakingdevice to trip. These devices may becompletely independent, built into ormounted on the breaking device.■ high setting dynamics ensuring continuityof supply■ a solution that can be used on all feedertypes irrespective of their rating.

An electromechanicalrelay

or an electronic relay?

electronicrelay

S N

tripping

leakagecurrent

20

DPN Vigi

Technical da taThe DPN Vigi one-piece residual current devices provide:■ complete protection of final circuits (overcurrents and insulationfaults)■ protection of persons against indirect contact (30 or 300 mA) ordirect contact (30 mA for socket feeders).■ protection of electrical installations against the risk of fire (300 to500 mA)■ with the 30 mA sensitivity, total vertical discrimination if they areinstalled downstream of a 300 mA S selective residual currentdevice (ID, Vigi, etc.)


■ the DPN Vigi meet current standards: IEC 1009 - EN 61009

Operating pr incipleThe residual current device combines the circuit-breaker and residualcurrent circuit-breaker functions in the same device.It thus provides complete protection against short-circuits, overloadsand insulation faults.Such versatility means it can advantageously be used in allapplication types.The main application of this device is the protection of faults and thusto guarantee increased continuity of supply (horizontaldiscrimination).Consequently, for special circuits and distant loads, each level can beprotected by a suitable residual current device according to itsposition and degree of risk.

devices


6

The term “ coordination” refers to the behaviour of 2 series-connected devices in electricalpower distribution in the event of an overcurrent or ground fault downstream. Theseprinciples are recognised and defined in installation standard IEC 364 and productstandards (IEC 947, etc.).Coordination of earth leakage protections must take place at circuit opening device level(for overcurrents) and at earth leakage protection device function level (for insulationfaults).

Coordination

Coordination of earth leakageprotectionsThis is performed by discrimination, circuit selection or acombination of both. Discrimination guarantees continuity ofsupply when a fault occurs, as it prevents the upstream devicefrom tripping when the fault is eliminated by the trippeddownstream device.■ discrimination may be at three or even four levels, when theinstallation includes a main LV switchboard, secondary switchboardsand final distribution switchboards.■ the final distribution switchboard normally contains the automaticbreaking function in order to provide protection against indirectcontact and additional protection against direct contact. Schneideroffers a wide choice of discrimination and sensitivity possibilities, thusenabling total coordination.(For example: after calculation of correct discrimination between Aand B, tripping of A is delayed: only B will trip, and de-energisation oflines 1 and 3 will be avoided).

A

B

1 2 3

Coordination of overcurrentprotections (of residual currentcircuit-breakers)One of the factors influencing the choice of circuit-breaker mustbe coordination with the short-circuit protection device installedupstream.As the residual current circuit-breaker has a limited breaking capacityand short-circuit current withstand, it must be protected againstshort-circuits developing downstream (electrodynamic protection)and overloads.The residual current circuit-breaker can be protected against short-circuits by the circuit-breaker (placed downstream in the sameswitchboard).Coordination of Schneider products offers integrated, automaticdiscrimination.Choice of a Schneider solution ensures perfect coordination ofyour protection system.

ID 2P 80 A

C60N 2P

20 kA

NC100H 2P

220 V CA

19

of residual current devices

Practical

A commonrangeof auxiliariesThe electrical auxiliaries allow remote tripping and indicationof circuit-breakers. They are mounted to the left of the circuit-breaker.



incomer ■ ■ ■



■ ■ ■

breaking capacity function of associated 3000 A - 4500 A must be obtained by cascadingcircuit-breaker (3 kA à 25 kA) or 6000 A with upstream circuit-breaker


■ Vigi C60Electromechanical earth leakage module■ instantaneaous 10 to 500 mA■ selective 300 to 1000 mA S■ rating up to 63 A

■ Vigi NC100Electromechanical earth leakage module■ instantaneaous 30 / 300 / 500 mA■ selective 300/1 000 mA S■ rating up to 100 A

■ Vigi NC125Electromechanical earth leakage module■ adjustable sensitivy (300 mA - 3 A)instantaneaous or selective S■ rating up to 125 A

■ Vigi NG125Electromechanical earth leakage module■ instantaneous : 30-300-500 mA■ selective : 300-500-1000 mA S■ delayed :1000-3000 mA R■ rating up to 125 A

7

Practical

The earthing systemsTT system

In the TT system, the sensitivity of the earth leakage protectiondevice against the risk of direct contact for protection of personsmust be:■ 30 mA maximum■ calculated according to standard IEC 364 or chosen bydiscrimination, for protection against indirect contact.

The small value of the fault current makes use of the earth leakage protection device necessary for protectionagainst indirect contact:■ either at the incoming end of the installation■ or by groups of equipment, if the load frames are not all connected to the same earthing connection or in orderto ensure better circuit separation.

IT SystemIn the IT system, the neutral conductor is not earthed.This “ isolated neutral ” system does not connect the neutralconductor to the earth, but is fitted with a protective conductorwhich ensures equipotentiality of frames with one another to earthpotential.

■ 1st fault: the user must be warned by the tripping of an indicator. The first fault does not present a risk forpersons.■ 2nd fault: this fault is dangerous:■ if the conductor frames are connected to the same earthing connection: it causes the circuit-breakers or fusesto trip.■ if the conductor frames are not connected to the same earthing connection: an RCD MUST be used.

TN-S SystemThe sensitivity of an earth leakage protection depends on theapplication. Schneider recommends the use of values that are:■ either defined by default■ or calculatedThe use of a residual current device in TN-S allows earlydetection of faults and detection of impedant faults withoutwaiting for the short-circuit to occur and the risks for equipmentthat it implies (equipment destruction, cable deterioration, fire,etc.).

This is also an advantage for electromagnetic compatibility as, when a fault occurs, the TN-S system lets veryhigh currents flow in the PE, device frames and structures.These currents become permanent if they are not sufficient to trip the overcurrent protection, and revealdifferences in potential between frames.

18

with a circuit-breaker

Operating principleWhen combined with a circuit-breaker, the earth leakage moduleoffers an additional earth leakage function.A simple auxiliary, it does not have an internal tripping mechanism.Its relay transmits a mechanical tripping order to the circuit-breaker,just like any other auxiliary.Upgradability of electrical circuits is thus ensured through theaddition of an earth leakage module at any time and on any circuit-breaker.The range of (Vigi) earth leakage modules offers a wide choice innumber of poles (2P, 3P, 4P), currents (25 to 125 A) and sensitivities(10 to 3000 mA).This guarantees that a Vigi module can always be combined with acircuit-breaker, whatever its rating, breaking capacity and trippingcurve.Its capacity to be adapted and upgraded make this range ideal forindustrial and large tertiary applications.


The “si” range is designed to maintain optimum safety and continuityof supply of networks in installations disturbed by:■ extreme atmospheric conditions,■ loads generating harmonics,■ transient switching currents.

■ The C60 Vigi module meet current standards: IEC 1009EN 61009

Earth leakage modu-les

L1L2L3N

PERn

combined

L1L2L3NPE

Rn


Practical

Vigicompact and safetyThe Vigicompact range offers a particularly reliable earth leakage protection:■ the power supply is three-phase.It is designed to operate:– with a missing phase,– with a voltage drop of up to 80 V on 2 phases (at this voltage level, the insulation fault is no longer dangerous,50 V as in IEC 364).■ the unlocking mechanism is mechanical:It is installed inside the case.Addition of an auxiliary release ensures there is no reduction in reliability.■ compliance with product standard IEC 947-2 appendix B guarantees users Vigi module proper operation testing:– after a short-circuit fault– in extreme supply voltage conditions– in disturbed environments according to the requirements of standards IEC 801-2 to -5 and IEC 255.

8

Protection of persons and equipment against direct and indirect contacts, insulationfaults and the risk of fire is provided by earth leakage protection devices: residual currentcircuit-breakers or residual current devices

Protection by a one-piece phaseneutral residual current deviceThe phase neutral residual current device provides completeprotection of final circuits, and its main features make itparticularly advantageous.It is used in housing and the tertiary sector.

■ it provides complete protection of final circuits (overcurrents andinsulation faults)■ it protects groups with only 1 to 3 loads■ it is mainly used for TT earthing systems■ it operates in single-phase circuits

Choosing

* requires additionalprotection to the short-circuit protection device.

Type of protection SensitivityProtection of persons 30 mAFire protection 300 to 500 mALoad protection 30 A *Cable protection 250 A *

Protection by residual current circuit-breakerThis device is recommended to provide earth leakage protectionof an existing installation equipped with a number of circuit-breakers or fuses.The residual current circuit-breaker is used in housing as wellas in the tertiary sector and industry.

■ it provides earth leakage protection for an outgoing circuit■ it meets residual breaking capacity needs (I∆m as in standardIEC 1008)The residual current circuit-breaker can be used in all neutralsystems.

17

■ Vigicompact NS100/250The releases areinterchangeable thermal-magnetic or electronicmodules.The earth leakage protectionfunction is performed directlyby adding the Vigi module tothe circuit-breaker case.

Protection typescomplementary protection fire ground fault protectionprotection against protection protection of equipment:against direct indirect motor, cablecontact contact

Vigi ME para NS 100 ■ ■❃y NS160 N/H/LVigi MH para NS 100 ■ ■ ■❃ ■y NS250 N/H/LVigi MB para NS 400 ■ ■❃ ■❃y NS630 N/H/LT option ■❃on NS400/NS630(*)

T option(*) STR55 UECompact NS400 / NS630 The GPF protection is of the “residual” type, with a threshold Ih and a time delay th

Ih Adjustable from 0,2 In to Inth 4 indexes

60 ms 140 ms 230 ms 350 ms

■ Vigicompact NS400/630The releases are interchangeablethermal-magnetic or electronic modules.The earth leakage protection function isperformed directly by adding the Vigimodule to the circuit-breaker case.

* made without using Vigi products.

the right protection


9

Protection by an earth leakage modulecombined with or built into a circuit-breakerThe ability of such systems to be adapted and upgraded makethem ideal for industrial and large tertiary applications.

■ complete protection of the installation from the main LVswitchboard and on the various subdistribution feeders (overcurrentsand insulation faults).■ discrimination of protection devices guaranteed by an extensiverange of settings and time delays irrespective of the Schneider earthleakage protection devices installed downstream■ protection of equipment (motors, cables, etc.) ensured up to 250 A.

Ground Fault Protection built intoa power circuit-breakerThis protection is necessary on power networks operated usingthe TN-S system when fault loop impedance is not controlled. Itis ideal for industrial applications and the large tertiary sector.

■ protection of cables and equipment up to 1200 A■ discrimination of protection devices ensured by time delay■ protection complies with NEC (National Electrical Code - USA)

16

Vigicompact

Technical data■ complies with IEC 947-2■ immunity ensured as in IEC 255 and IEC 801-2 to -5, i.e.:protection against nuisance tripping due to transient overvoltages,lightning strokes, device switchings on network, electrostaticdischarges, electrical radio waves.■ unaffected by A class DC components as in IEC 755■ operation up to -25°C■ sensitivity adjustable from 30 mA to 30 A according to ratings■ adjustable time delay (4 indexes)■ test by simulation of an insulation faultIntegration of the Vigi module in the circuit-breaker does not changeits safety features:■ class II insulation on the front face■ isolation with positive break indication

Operating principleThe Vigicompact range is ideal for the protection of powerswitchboard feeders and/or incomers. The threshold settingpossibilities enable protection of many industrial and tertiaryapplications (protection of persons and equipment, motors, cables,etc.).The time delay possibilities allow total discrimination withdownstream distribution, thereby guaranteeing continuity of supply forusers.The Vigicompact range offers a reliable solution:Three-phase supply without auxiliary supply source,Measuring and tripping system built into the circuit-breaker case.The Vigicompact range is immune to nuisance tripping and is notaffected by DC components (A class device as in IEC 947-2recommendations, Appendix B).

Residualcurrent devices


Practical

An easy-to-install rangeThe VIGIREX devices provide installation solutions■ mounting on a symmetrical rail or plate, or surface mounting■ the toroids are installed directly on cable, symmetrical rail, devices, etc.■ power supply safety is guaranteed by:— a LED on the front face— a contact for remote transfer: the VIGIREX relay permanently monitors the toroid/relay connection.

Installation

10

Why do we need to provide protectionagainst indirect contact?This type of contact is just as dangerous as direct contact, which iswhy faulty devices must be isolated as soon as the fault occurs.

The sensitivity of residual current devices, placed at the incomingend of the switchboard for indirect contact protection, will be adaptedto foreseeable ground fault currents. In practice, the threshold will begreater than 500 mA in order to prevent nuisance tripping and allowdiscrimination.

Verification of residual current device sensitivity necessarily takesinto account the maximum value of the earthing connection byapplying the formula: Id < UL/Ra,

Id: fault current;UL: limit safety voltage as in standard IEC 364;Damp places: UL = 25 VGeneral case: UL = 50 VRa: total resistance of the ground fault loop.

How to make a reliable installation?■ The physiological studies defined by standard IEC 479 havedetermined the risks linked to the flow of electric current in thehuman body.- Compliance with the thresholds set by standard IEC 479 ensures anoutstanding level of safety while yet maintaining good continuity ofsupply.- 30 mA is the respiratory paralysis threshold: this corresponds to acurrent that can flow through the body without risk of ventricularfibrillation (in other words without cardiac arrest). This level is placedat the asymptote of a curve such that if this current persists for aninfinite time, the risk of ventricular fibrillation in the population is non-existent in 95% of cases. This limit is accepted for adults andchildren.

The thresholds determine the sensitivity of the earth leakageprotection devices:■ 30 mA maximum for complementary protection of persons againstdirect contact,■ 10 mA for “additional protection”, if necessary, of hand-helddevices (no standard as yet) and surface sockets.The 30 mA sensitivity in the table is a good compromise ensuringcircuit protection without generating nuisance tripping.

recommendations

15

Protection types

■ RH10A-RH10AP ■ RH320A-RH320AP ■ RH328A-RH328AP

■ OA type split toroids■ Split toroids forrenovations andextensions■ detect leakagecurrents and transmita proportionalto the associated load.

complementary protection fire ground fault protectionprotection against protection protection of equipment:against direct indirect motor, cablecontact contact

RH10A ■ ■ ■❃RH10APRH320A ■ ■ ■❃RH320APRH328A ■ ■ ■❃ ■ ■❃RH328APT option ■❃on Masterpact,Compact C (*)

* made without using Vigirex products.

T option(*) Masterpact STR38S / STR58 U / STR68 U Compact C STR45 AE / STR55 UEGPF protection is of the “residual” type, GPF protection is of the “residual” type,with a threshold Ih and a time delay th with a threshold Ih and a time delay th

Ih Adjustable from 0,1 In to In (where Ih < 1200 A) Adjustable from 0,2 to 0,6 Inth 4 indexes 4 indexes

0,1 sec. 0,2 sec. 0,3 sec. 0,4 sec. 0,1 sec. 0,2 sec. 0,3 sec. 0,4 sec.

■ A type closedtoroids■ Closed toroids fornew works andextension signal■ detect leakagecurrents and transmitsignal proportionalto the associated load.


11

How can loads be protected?In the TN-S system, an insulation fault causes high leakage currentswhich may degenerate into short-circuit currents. These currentsmust thus be eliminated as quickly as possible in order to avoid:

■ overheating of cables

■ perforation of insulators

■ deterioration of loads

The introduction of earth leakage protection devices prevents thesehigh short-circuit currents from occurring.

Protection thresholds are left for users to determine, but Schneiderrecommends they be set between 500 mA and 30 A with or withouttime delay. When only cables require protection, thresholds may beincreased up to 250 A.

Ground Fault Protection: for American type networks, the aim is tomonitor fault loop impedance at the incoming end of the installationand to limit stray currents up to 1200 A.

Schneider recommends the installation of ground fault protectiondevices set to the lowest possible threshold. Total discrimination ofthese devices is ensured by using the various downstream protectiondevices.

What protection can be providedagainst the risk of fire?Standard IEC 364 makes provision for protection against the risk offire caused by the flow of fault currents in the busways. The value ofresidual current device sensitivity ensures protection against this risk.

Fires are created by:

■ deterioration of the insulator■ appearance of overheating in the cables■ creation of a leakage current through the insulators

In order to protect against fire, Schneider recommends installing aresidual current device with a sensitivity threshold of at least 300 mA.

14

Vigirex

Technical dataThe VIGIREX relay range is ideal for operation with 100 A to 6300 ACompact and Masterpact circuit-breakers. It is designed:■ for AC networks up to 1000 V, 50, 60 and 400 Hz frequency■ in compliance with:– installation standards: IEC 364, particularly paragraphs 4 and 5– product standards: IEC 755, IEC 947-2 and applicable nationalstandards (VDE 664, NF-C 61-141, etc.).■ The functions performed:The VIGIREX range boasts 6 devices and 8 toroids covering allapplications.The VIGIREX relays are designed for protection of persons andequipment, for prevention and for protection of applications: motor,cable, generator, etc.

Operating principleThe VIGIREX range is the ideal solution for guaranteeing safety ofpersons and equipment for applications requiring a high degree ofinstallation flexibility: renovation, rack mounting, motor protection,industrial control, generator, etc.The many available settings, thresholds and time delays guaranteeexcellent continuity of supply.The VIGIREX range is designed to ensure optimum safety: “failsafe”safety of power supply, pilot light, monitoring continuity of themeasurement circuit, etc.The VIGIREX relays are immune to nuisance tripping and areunaffected by DC components - A class device as in IEC 947-2recommendations - Appendix B. Preventive maintenance is possibleas an option thanks to its insulation drop indicator light.

Residual currentrelays with separate toroid


12

motor

I ∆n = dependson earthing connection resistance

N123

compressorband saw

fixed substationI∆n = 300 mA

lathe planing machine

MasterpactM32

TransformerMain LV switchboard

Vigirex

MasterpactM16Vigirex

Generator set

Vigirex

Vigi CompactNS 160H

CompactC 801

I∆n = 1 A100 mS

I∆n = 30 A500 mS

I∆n = 250 A500 mS

I∆n = 10 A300 mS

TN-S

TT

13

Earth leakage protectionin power low voltage■ Residual current relayswith separate toroid: Vigirex p. 14-15■ Residual currentdevices: Vigicompact p. 16-17

Earth leakage protectionin final low voltage■ Earth leakage modules combinedwith a circuit-breaker: Vigi p. 18-19■ Residual currentdevices: DPN Vigi p. 20-21■ Residual currentcircuit-breakers: ID/FI/RCCB p. 22-23

N123

I∆n = 300 mA

10 A 16 A 32 A10 AI∆n = 30 mA

I∆n 30 mA

machine arealighting

≤ I∆n 30 mA

≤

sockets for hand-helddevices

airextractors

grinder

Installationrecommendations


12

motor

I ∆n = dependson earthing connection resistance

N123

compressorband saw

fixed substationI∆n = 300 mA

lathe planing machine

MasterpactM32

TransformerMain LV switchboard

Vigirex

MasterpactM16Vigirex

Generator set

Vigirex

Vigi CompactNS 160H

CompactC 801

I∆n = 1 A100 mS

I∆n = 30 A500 mS

I∆n = 250 A500 mS

I∆n = 10 A300 mS

TN-S

TT

13

Earth leakage protectionin power low voltage■ Residual current relayswith separate toroid: Vigirex p. 14-15■ Residual currentdevices: Vigicompact p. 16-17

Earth leakage protectionin final low voltage■ Earth leakage modules combinedwith a circuit-breaker: Vigi p. 18-19■ Residual currentdevices: DPN Vigi p. 20-21■ Residual currentcircuit-breakers: ID/FI/RCCB p. 22-23

N123

I∆n = 300 mA

10 A 16 A 32 A10 AI∆n = 30 mA

I∆n 30 mA

machine arealighting

≤ I∆n 30 mA

≤

sockets for hand-helddevices

airextractors

grinder

Installationrecommendations


11

How can loads be protected?In the TN-S system, an insulation fault causes high leakage currentswhich may degenerate into short-circuit currents. These currentsmust thus be eliminated as quickly as possible in order to avoid:

■ overheating of cables

■ perforation of insulators

■ deterioration of loads

The introduction of earth leakage protection devices prevents thesehigh short-circuit currents from occurring.

Protection thresholds are left for users to determine, but Schneiderrecommends they be set between 500 mA and 30 A with or withouttime delay. When only cables require protection, thresholds may beincreased up to 250 A.

Ground Fault Protection: for American type networks, the aim is tomonitor fault loop impedance at the incoming end of the installationand to limit stray currents up to 1200 A.

Schneider recommends the installation of ground fault protectiondevices set to the lowest possible threshold. Total discrimination ofthese devices is ensured by using the various downstream protectiondevices.

What protection can be providedagainst the risk of fire?Standard IEC 364 makes provision for protection against the risk offire caused by the flow of fault currents in the busways. The value ofresidual current device sensitivity ensures protection against this risk.

Fires are created by:

■ deterioration of the insulator■ appearance of overheating in the cables■ creation of a leakage current through the insulators

In order to protect against fire, Schneider recommends installing aresidual current device with a sensitivity threshold of at least 300 mA.

14

Vigirex

Technical dataThe VIGIREX relay range is ideal for operation with 100 A to 6300 ACompact and Masterpact circuit-breakers. It is designed:■ for AC networks up to 1000 V, 50, 60 and 400 Hz frequency■ in compliance with:– installation standards: IEC 364, particularly paragraphs 4 and 5– product standards: IEC 755, IEC 947-2 and applicable nationalstandards (VDE 664, NF-C 61-141, etc.).■ The functions performed:The VIGIREX range boasts 6 devices and 8 toroids covering allapplications.The VIGIREX relays are designed for protection of persons andequipment, for prevention and for protection of applications: motor,cable, generator, etc.

Operating principleThe VIGIREX range is the ideal solution for guaranteeing safety ofpersons and equipment for applications requiring a high degree ofinstallation flexibility: renovation, rack mounting, motor protection,industrial control, generator, etc.The many available settings, thresholds and time delays guaranteeexcellent continuity of supply.The VIGIREX range is designed to ensure optimum safety: “failsafe”safety of power supply, pilot light, monitoring continuity of themeasurement circuit, etc.The VIGIREX relays are immune to nuisance tripping and areunaffected by DC components - A class device as in IEC 947-2recommendations - Appendix B. Preventive maintenance is possibleas an option thanks to its insulation drop indicator light.

Residual currentrelays with separate toroid


Practical

An easy-to-install rangeThe VIGIREX devices provide installation solutions■ mounting on a symmetrical rail or plate, or surface mounting■ the toroids are installed directly on cable, symmetrical rail, devices, etc.■ power supply safety is guaranteed by:— a LED on the front face— a contact for remote transfer: the VIGIREX relay permanently monitors the toroid/relay connection.

Installation

10

Why do we need to provide protectionagainst indirect contact?This type of contact is just as dangerous as direct contact, which iswhy faulty devices must be isolated as soon as the fault occurs.

The sensitivity of residual current devices, placed at the incomingend of the switchboard for indirect contact protection, will be adaptedto foreseeable ground fault currents. In practice, the threshold will begreater than 500 mA in order to prevent nuisance tripping and allowdiscrimination.

Verification of residual current device sensitivity necessarily takesinto account the maximum value of the earthing connection byapplying the formula: Id < UL/Ra,

Id: fault current;UL: limit safety voltage as in standard IEC 364;Damp places: UL = 25 VGeneral case: UL = 50 VRa: total resistance of the ground fault loop.

How to make a reliable installation?■ The physiological studies defined by standard IEC 479 havedetermined the risks linked to the flow of electric current in thehuman body.- Compliance with the thresholds set by standard IEC 479 ensures anoutstanding level of safety while yet maintaining good continuity ofsupply.- 30 mA is the respiratory paralysis threshold: this corresponds to acurrent that can flow through the body without risk of ventricularfibrillation (in other words without cardiac arrest). This level is placedat the asymptote of a curve such that if this current persists for aninfinite time, the risk of ventricular fibrillation in the population is non-existent in 95% of cases. This limit is accepted for adults andchildren.

The thresholds determine the sensitivity of the earth leakageprotection devices:■ 30 mA maximum for complementary protection of persons againstdirect contact,■ 10 mA for “additional protection”, if necessary, of hand-helddevices (no standard as yet) and surface sockets.The 30 mA sensitivity in the table is a good compromise ensuringcircuit protection without generating nuisance tripping.

recommendations

15

Protection types

■ RH10A-RH10AP ■ RH320A-RH320AP ■ RH328A-RH328AP

■ OA type split toroids■ Split toroids forrenovations andextensions■ detect leakagecurrents and transmita proportionalto the associated load.

complementary protection fire ground fault protectionprotection against protection protection of equipment:against direct indirect motor, cablecontact contact

RH10A ■ ■ ■❃RH10APRH320A ■ ■ ■❃RH320APRH328A ■ ■ ■❃ ■ ■❃RH328APT option ■❃on Masterpact,Compact C (*)

* made without using Vigirex products.

T option(*) Masterpact STR38S / STR58 U / STR68 U Compact C STR45 AE / STR55 UEGPF protection is of the “residual” type, GPF protection is of the “residual” type,with a threshold Ih and a time delay th with a threshold Ih and a time delay th

Ih Adjustable from 0,1 In to In (where Ih < 1200 A) Adjustable from 0,2 to 0,6 Inth 4 indexes 4 indexes

0,1 sec. 0,2 sec. 0,3 sec. 0,4 sec. 0,1 sec. 0,2 sec. 0,3 sec. 0,4 sec.

■ A type closedtoroids■ Closed toroids fornew works andextension signal■ detect leakagecurrents and transmitsignal proportionalto the associated load.


9

Protection by an earth leakage modulecombined with or built into a circuit-breakerThe ability of such systems to be adapted and upgraded makethem ideal for industrial and large tertiary applications.

■ complete protection of the installation from the main LVswitchboard and on the various subdistribution feeders (overcurrentsand insulation faults).■ discrimination of protection devices guaranteed by an extensiverange of settings and time delays irrespective of the Schneider earthleakage protection devices installed downstream■ protection of equipment (motors, cables, etc.) ensured up to 250 A.

Ground Fault Protection built intoa power circuit-breakerThis protection is necessary on power networks operated usingthe TN-S system when fault loop impedance is not controlled. Itis ideal for industrial applications and the large tertiary sector.

■ protection of cables and equipment up to 1200 A■ discrimination of protection devices ensured by time delay■ protection complies with NEC (National Electrical Code - USA)

16

Vigicompact

Technical data■ complies with IEC 947-2■ immunity ensured as in IEC 255 and IEC 801-2 to -5, i.e.:protection against nuisance tripping due to transient overvoltages,lightning strokes, device switchings on network, electrostaticdischarges, electrical radio waves.■ unaffected by A class DC components as in IEC 755■ operation up to -25°C■ sensitivity adjustable from 30 mA to 30 A according to ratings■ adjustable time delay (4 indexes)■ test by simulation of an insulation faultIntegration of the Vigi module in the circuit-breaker does not changeits safety features:■ class II insulation on the front face■ isolation with positive break indication

Operating principleThe Vigicompact range is ideal for the protection of powerswitchboard feeders and/or incomers. The threshold settingpossibilities enable protection of many industrial and tertiaryapplications (protection of persons and equipment, motors, cables,etc.).The time delay possibilities allow total discrimination withdownstream distribution, thereby guaranteeing continuity of supply forusers.The Vigicompact range offers a reliable solution:Three-phase supply without auxiliary supply source,Measuring and tripping system built into the circuit-breaker case.The Vigicompact range is immune to nuisance tripping and is notaffected by DC components (A class device as in IEC 947-2recommendations, Appendix B).

Residualcurrent devices


Practical

Vigicompact and safetyThe Vigicompact range offers a particularly reliable earth leakage protection:■ the power supply is three-phase.It is designed to operate:– with a missing phase,– with a voltage drop of up to 80 V on 2 phases (at this voltage level, the insulation fault is no longer dangerous,50 V as in IEC 364).■ the unlocking mechanism is mechanical:It is installed inside the case.Addition of an auxiliary release ensures there is no reduction in reliability.■ compliance with product standard IEC 947-2 appendix B guarantees users Vigi module proper operation testing:– after a short-circuit fault– in extreme supply voltage conditions– in disturbed environments according to the requirements of standards IEC 801-2 to -5 and IEC 255.

8

Protection of persons and equipment against direct and indirect contacts, insulationfaults and the risk of fire is provided by earth leakage protection devices: residual currentcircuit-breakers or residual current devices

Protection by a one-piece phaseneutral residual current deviceThe phase neutral residual current device provides completeprotection of final circuits, and its main features make itparticularly advantageous.It is used in housing and the tertiary sector.

■ it provides complete protection of final circuits (overcurrents andinsulation faults)■ it protects groups with only 1 to 3 loads■ it is mainly used for TT earthing systems■ it operates in single-phase circuits

Choosing

* requires additionalprotection to the short-circuit protection device.

Type of protection SensitivityProtection of persons 30 mAFire protection 300 to 500 mALoad protection 30 A *Cable protection 250 A *

Protection by residual current circuit-breakerThis device is recommended to provide earth leakage protectionof an existing installation equipped with a number of circuit-breakers or fuses.The residual current circuit-breaker is used in housing as wellas in the tertiary sector and industry.

■ it provides earth leakage protection for an outgoing circuit■ it meets residual breaking capacity needs (I∆m as in standardIEC 1008)The residual current circuit-breaker can be used in all neutralsystems.

17

■ Vigicompact NS100/250The releases areinterchangeable thermal-magnetic or electronicmodules.The earth leakage protectionfunction is performed directlyby adding the Vigi module tothe circuit-breaker case.

Protection typescomplementary protection fire ground fault protectionprotection against protection protection of equipment:against direct indirect motor, cablecontact contact

Vigi ME para NS 100 ■ ■❃y NS160 N/H/LVigi MH para NS 100 ■ ■ ■❃ ■y NS250 N/H/LVigi MB para NS 400 ■ ■❃ ■❃y NS630 N/H/LT option ■❃on NS400/NS630(*)

T option(*) STR55 UECompact NS400 / NS630 The GPF protection is of the “residual” type, with a threshold Ih and a time delay th

Ih Adjustable from 0,2 In to Inth 4 indexes

60 ms 140 ms 230 ms 350 ms

■ Vigicompact NS400/630The releases are interchangeablethermal-magnetic or electronic modules.The earth leakage protection function isperformed directly by adding the Vigimodule to the circuit-breaker case.

* made without using Vigi products.

the right protection


7

Practical

The earthing systemsTT system

In the TT system, the sensitivity of the earth leakage protectiondevice against the risk of direct contact for protection of personsmust be:■ 30 mA maximum■ calculated according to standard IEC 364 or chosen bydiscrimination, for protection against indirect contact.

The small value of the fault current makes use of the earth leakage protection device necessary for protectionagainst indirect contact:■ either at the incoming end of the installation■ or by groups of equipment, if the load frames are not all connected to the same earthing connection or in orderto ensure better circuit separation.

IT SystemIn the IT system, the neutral conductor is not earthed.This “ isolated neutral ” system does not connect the neutralconductor to the earth, but is fitted with a protective conductorwhich ensures equipotentiality of frames with one another to earthpotential.

■ 1st fault: the user must be warned by the tripping of an indicator. The first fault does not present a risk forpersons.■ 2nd fault: this fault is dangerous:■ if the conductor frames are connected to the same earthing connection: it causes the circuit-breakers or fusesto trip.■ if the conductor frames are not connected to the same earthing connection: an RCD MUST be used.

TN-S SystemThe sensitivity of an earth leakage protection depends on theapplication. Schneider recommends the use of values that are:■ either defined by default■ or calculatedThe use of a residual current device in TN-S allows earlydetection of faults and detection of impedant faults withoutwaiting for the short-circuit to occur and the risks for equipmentthat it implies (equipment destruction, cable deterioration, fire,etc.).

This is also an advantage for electromagnetic compatibility as, when a fault occurs, the TN-S system lets veryhigh currents flow in the PE, device frames and structures.These currents become permanent if they are not sufficient to trip the overcurrent protection, and revealdifferences in potential between frames.

18

with a circuit-breaker

Operating principleWhen combined with a circuit-breaker, the earth leakage moduleoffers an additional earth leakage function.A simple auxiliary, it does not have an internal tripping mechanism.Its relay transmits a mechanical tripping order to the circuit-breaker,just like any other auxiliary.Upgradability of electrical circuits is thus ensured through theaddition of an earth leakage module at any time and on any circuit-breaker.The range of (Vigi) earth leakage modules offers a wide choice innumber of poles (2P, 3P, 4P), currents (25 to 125 A) and sensitivities(10 to 3000 mA).This guarantees that a Vigi module can always be combined with acircuit-breaker, whatever its rating, breaking capacity and trippingcurve.Its capacity to be adapted and upgraded make this range ideal forindustrial and large tertiary applications.


The “si” range is designed to maintain optimum safety and continuityof supply of networks in installations disturbed by:■ extreme atmospheric conditions,■ loads generating harmonics,■ transient switching currents.

■ The C60 Vigi module meet current standards: IEC 1009EN 61009

Earth leakage modules

L1L2L3N

PERn

combined

L1L2L3NPE

Rn


6

The term “ coordination” refers to the behaviour of 2 series-connected devices in electricalpower distribution in the event of an overcurrent or ground fault downstream. Theseprinciples are recognised and defined in installation standard IEC 364 and productstandards (IEC 947, etc.).Coordination of earth leakage protections must take place at circuit opening device level(for overcurrents) and at earth leakage protection device function level (for insulationfaults).

Coordination

Coordination of earth leakageprotectionsThis is performed by discrimination, circuit selection or acombination of both. Discrimination guarantees continuity ofsupply when a fault occurs, as it prevents the upstream devicefrom tripping when the fault is eliminated by the trippeddownstream device.■ discrimination may be at three or even four levels, when theinstallation includes a main LV switchboard, secondary switchboardsand final distribution switchboards.■ the final distribution switchboard normally contains the automaticbreaking function in order to provide protection against indirectcontact and additional protection against direct contact. Schneideroffers a wide choice of discrimination and sensitivity possibilities, thusenabling total coordination.(For example: after calculation of correct discrimination between Aand B, tripping of A is delayed: only B will trip, and de-energisation oflines 1 and 3 will be avoided).

A

B

1 2 3

Coordination of overcurrentprotections (of residual currentcircuit-breakers)One of the factors influencing the choice of circuit-breaker mustbe coordination with the short-circuit protection device installedupstream.As the residual current circuit-breaker has a limited breaking capacityand short-circuit current withstand, it must be protected againstshort-circuits developing downstream (electrodynamic protection)and overloads.The residual current circuit-breaker can be protected against short-circuits by the circuit-breaker (placed downstream in the sameswitchboard).Coordination of Schneider products offers integrated, automaticdiscrimination.Choice of a Schneider solution ensures perfect coordination ofyour protection system.

ID 2P 80 A

C60N 2P

20 kA

NC100H 2P

220 V CA

19

of residual current devices

Practical

A commonrangeof auxiliariesThe electrical auxiliaries allow remote tripping and indicationof circuit-breakers. They are mounted to the left of the circuit-breaker.



incomer ■ ■ ■



■ ■ ■

breaking capacity function of associated 3000 A - 4500 A must be obtained by cascadingcircuit-breaker (3 kA à 25 kA) or 6000 A with upstream circuit-breaker


■ Vigi C60Electromechanical earth leakage module■ instantaneaous 10 to 500 mA■ selective 300 to 1000 mA S■ rating up to 63 A

■ Vigi NC100Electromechanical earth leakage module■ instantaneaous 30 / 300 / 500 mA■ selective 300/1 000 mA S■ rating up to 100 A

■ Vigi NC125Electromechanical earth leakage module■ adjustable sensitivy (300 mA - 3 A)instantaneaous or selective S■ rating up to 125 A

■ Vigi NG125Electromechanical earth leakage module■ instantaneous : 30-300-500 mA■ selective : 300-500-1000 mA S■ delayed :1000-3000 mA R■ rating up to 125 A

Residual current

5

Schneider proposes two technologies: electromechanical and electronic. The technologicalchoice depends on the specific features of your installation. In compliance with thestandard, Schneider recommends:■ a residual current device with electromechanical relay for unmonitored distribution(domestic applications and equivalent).■ a residual current device with electronic relay for monitored distribution (applicationsbenefiting from a maintenance service).

S N

tripping

outgoingcurrent

returncurrent


The residual currentdevice withelectromechanical relayThis device operates without anyauxiliary source of supply. The energysupplied by the toroid energises anelectromagnet whose moving part ismaintained in the closed position by apermanent magnet.■ fault current energy is the direct cause oftripping. This is the most reliable technologyas it works regardless of fault origin.■ user safety is top priority, and should notbe dependent on quality of the network(public/private), installation age, the neutralsystem chosen or the mechanism reset.

The residual currentdevice with electronicrelayThis device operates with an auxiliarysource of supply. The electrical energysupplied by the toroid is amplified by theelectronic board, in turn supplied by asource dependent on network voltage.Fault detection causes the breakingdevice to trip. These devices may becompletely independent, built into ormounted on the breaking device.■ high setting dynamics ensuring continuityof supply■ a solution that can be used on all feedertypes irrespective of their rating.

An electromechanicalrelay

or an electronic relay?

electronicrelay

S N

tripping

leakagecurrent

20

DPN Vigi

Technical dataThe DPN Vigi one-piece residual current devices provide:■ complete protection of final circuits (overcurrents and insulationfaults)■ protection of persons against indirect contact (30 or 300 mA) ordirect contact (30 mA for socket feeders).■ protection of electrical installations against the risk of fire (300 to500 mA)■ with the 30 mA sensitivity, total vertical discrimination if they areinstalled downstream of a 300 mA S selective residual currentdevice (ID, Vigi, etc.)


■ the DPN Vigi meet current standards: IEC 1009 - EN 61009

Operating principleThe residual current device combines the circuit-breaker and residualcurrent circuit-breaker functions in the same device.It thus provides complete protection against short-circuits, overloadsand insulation faults.Such versatility means it can advantageously be used in allapplication types.The main application of this device is the protection of faults and thusto guarantee increased continuity of supply (horizontaldiscrimination).Consequently, for special circuits and distant loads, each level can beprotected by a suitable residual current device according to itsposition and degree of risk.

devices


4

Leakage current risksAll LV electrical installations have earth leakage currents. Due partly to conductor capacitance, theyincrease when class 1 devices or motors with limited insulation are used.An occasional earth leakage current greater than merely 500 mA can generate a sufficient overcurrent for theinsulator to heat, melt and start stripping the conductor.The leakage current flowing through the damaged insulator creates an electric arc the intense heat of whichignites the insulator and starts a fire.

The principle of Schneider’s earth leakage protection is based on a system performingthree successive functions virtually instantaneously: detection of a leakage current,measurement of this current and trip opening of the faulty circuit.

DetectionA current transformer is used whose primary windings are thephase(s) and the neutral of the circuit to be protected. The windingdirection is such that the load and neutral currents cancel oneanother out. The appearance of a leakage current destroys thisbalance and generates a current at the secondary winding known asa residual current.

MeasurementAn electromechanical relay is used which compares the electricsignal to a pre-set limit: the tripping threshold, also known assensitivity.

■ a permanent magnet holds in the “ closed ” position a swivel plateconnected to a tripping mechanism.

■ opposite this, an electromagnet supplied by the residual current,and a taut spring have a joint effect on plate opening.

As long as the strength of the permanent magnet (defined accordingto required system sensitivity) is greater than that of the spring andthe electromagnet, the circuit is closed.

TrippingAs soon as the residual current is high enough to cancel the effect ofthe permanent magnet, the spring causes the plate to swivel whichthen strikes the trip opening mechanism of the faulty circuit.

earth leakage protection work

Howdoes

detection

outgoingcurrent

returncurrent

current variation = 0

S N

current variation

measurement

= 0

tripping


SN

Detection

Measurement

Tripping

21

PracticalIn the IT earthingsystem, there is aneed to providedetection ofovercurrent on theneutral conductorof all circuits,causing breakingof all live conductors,including the neutralconductor.This protection is not

necessary if:■ the neutralconductor is

protected againstshort-circuitsby a device placedupstream;■ the circuit is partof final circuits,of buswaysof the same type,of identical or verysimilar cross-section, and if theassembly is

whose ratedresidual currentis at most equalto 0.15 timesthe acceptablecurrentin the conductor withthe smallest cross-section.

N

residualcurrentdevice

plug lighting heatingsystem

DPN DPN DPN

L1L2L3

N L1 L2 L3

N

DPN DPN

Residual current device or residual current circuit-breaker

L1L2L3

N L1 L2 L3

protected by anearth leakageprotection device


■ Declic Vigi■ rating: 6 to 32 A■ voltage rating: 230 V CA■ breaking capacity: 3000 A

■ DPN Vigi■ rating: 6 to 40 A■ voltage rating: 230 V CA■ breaking capacity: 6000 A


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3

How does earth leakage protection work? P. 4

Detection / Measurement / Tripping

An electromechanical or an electronic relay? P. 5

Two different technologies

Coordination of residual current devices P. 6

Coordination of earth leakage protectionsCoordination of overcurrent protections (of residual current circuit-breakers)

Choosing the right protection P. 8

Protection by residual current circuit-breakerProtection by one-piece phase neutral residual current deviceProtection by an earth leakage module combined with or built into a circuit-breakerGround fault protection built into a power circuit-breaker

Installation recommendations P. 10-11

How to make a reliable installation?Protection against indirect contactProtection against the risk of fireHow to protect loads?

Schneider low voltage earth leakage protection P. 12-13

Installation recommendation: an exemple of a solution

The product pages P. 14-23

How toprotectpersonsandequipments?When confrontedwith the riskof electrocution,destructionof loads and fire,two different butcomplementaryapproaches enableimplementationof effective protection.

1Prevention:prevent the faultfrom occuringThis approach mainlyconcerns new electricalinstallations. Technicalprogress and applicationof strict standards area major assetfor the commissionningof efficient, reliableinstallations.

2 Action: detectand neutralisefaults.

Contentsearth leakage protection

22



■ The residual current circuit-breakers meet current standards:IEC 1008, EN61008.

Operating principleIn addition to leakage current detection, the residual current circuit-breaker can be used to open, close or isolate a circuit. It has noshort-circuit or overload protection, and as such must be protected byan upstream circuit-breaker.Its main function is to protect a set of feeders, each equipped withcircuit-breakers.Use of the residual current circuit-breaker is recommended to provideearth leakage protection of an existing installation, already equippedwith circuit-breakers.Consequently, particularly used for domestic, tertiary and smallindustrial applications, its advantage is that it can provide completesafety of sensitive circuits at a low cost, for example in a kitchen orbathroom, a shop where there are risks for customers, damp workingpremises and premises with an aggressive environment.

Residual current

Thesolution:The Schneiderrange of earthleakage protectionproducts.

circuit-breakers


L’électrocutionA few milliamps suffice to seriously harm the human body. Electrocution canoccur either by direct contact with an electric cable or a live device, or byindirect contact, if the person touches an accidentally energised metal part.

The physiological reactiondepends on:■ the contact voltage■ the type and duration of thecontact■ the age and vulnerability ofthe subject.

installation standardsin each country for K(normally 0.6)).

Electrodynamicwithstand capacityShort-circuit protectionmust be provided bythe short-circuitprotection deviceplaced upstream.However, it isaccepted, when the

Practical

A few installation tips

2

All electrical installations produce current flows. Even small flows present non-negligiblerisks which can cause serious damage.

Fire30% of fires inindustrial and domesticbuildings are the resultof an electrical fault, themain cause of which isdeterioration of a cableinsulator due tooverheating oraccidental knocking.

23protectionearth leakage

Current ratingChosen according tothe current flowingthrough it.■ if the residualcurrent circuit-breakeris placed downstreamof a circuit-breaker andon the same circuit,the rated currents ofboth devices are atmost the same: Ib > Ia.■ if it is placed

upstream of a group ofcircuits, its ratedcurrent is chosen sothat:Ic = K(Id + Ie + If + Ig).K is the “coincidence”factor which takesdevice efficiencyand power intoaccount, as well astheir utilisation andextension factors(comply with applicable

residual current circuit-breaker and thedownstream short-circuit protectiondevices are in thesame switchboardproduced according tostandards, that theshort-circuit currentwithstand of theresidual current circuit-breaker may also beprovided by the

■ ID/RCCB/FI■ 4 poles■ rating: 25 to 100A■ voltage rating: 400 VAC■ sensitivity: 30 to 1000 mAinstantaneous or selective S

■ ID/RCCB/FI■ 2 poles■ rating: 25-80 A■ voltage rating: 230 VAC■ sensitivity: 10 to 500 mAinstantaneous or selective S

■ ID/RCCB/FI■ 2 or 4 poles■ rating: 100A and 125A■ voltage rating: 230/400 VAC■ sensitivity: 30 to 300 mAinstantaneous or selective S

downstream short-circuit protectiondevices.In this case,coordination isnecessary between theshort-circuit protectiondevice and the residualcurrent circuit-breaker.

Equipements électriques :

The riks

earth leakage current ≥ 500 mA + load current

overcurrent

insulator temperature rise

the insulator melts and strips the conductor

accident

LoaddestructionSome electrical devices deteriorate overtime and may present insulation faults.Insulation faults have many causes:■ heat generated by device operation■ overcurrent■ aggressiveness of the environment■ material wear and loss of tightnessApart from load destruction, there is a riskof electrocution and fire.

and their consequences

Electrical equipment:

1 A cardiac arrest

75 mA irreversible cardiacfibrillation threshold

30 mA respiratory paralysisthreshold

10 mA muscular contraction(tetanisation)

0,5 mA very slight sensation


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Documents

Earth Leakage Protection