Choosing Surge Arresters for LV Networks

7/27/2019 Choosing Surge Arresters for LV Networks

1/1292506E.fm/2 Schneider ElectricUpdated: 21/02/02

surge arresterschoosing surge arresters for :LV networks

in function of the technicaldata for loads

#

the surge arresters level of protection (Up)depends on the installed equipment and therated voltage of the installation

#

Up must lie between:5

the full voltage of the permanent operatingconditions (Uc)5

the impulse withstand voltage (Uchoc) of

the equipment to be protected.

8/20 impulse withstand table for equipment to be protected#

general standard: IEC 60364-4

rated voltage equipment sensitivity withstand (Uchoc)of the installation

threephase reduced normal high very high

Uc < Up < Uchoc networks electronic circuit electrical household industrial industrial

devices: appliances: devices: devices:

televisions, alarms, HiFi, dishwashers, ovens motors, distribution electric

video recorders, computers refrigerators, protable cabinets, current meters,

telecommunication tools sockets, transfos. telemeters

400/690/1000 2.5 kV 4 kV 6 kV 8 kV

230/440 V 1.5 kV 2.5 kV 4 kV 6 kVshock wave shock wave shock wave shock wave

category I category II category III category IV

Uc value as in the French standard: NF C 15100 section 534

earthing systems TT TN-S TN-C ITUc value for common mode 1.5 Uo 1.5 Uo 1.5 Uo 1.732 Uo

(protection between live conductors and earth)

Uc value for differential mode 1.1 Uo 1.1 Uo 1.1 Uo

(protection between phase and neutral)

Uo: simple network voltage between phase and neutral

Uc: full voltage under permanent operating conditions

placing several surge arresters in a cascading configuration

The incoming protection device (P1) isdimensioned to run-off lightning currents at thesource of the installation, 2 cases are possible:#

if there is a level of protection (Up) too highfor the impulse withstand voltage (Uchoc) ofthe installations equipment:5

a secondary protection surge arrester (P2)placed near loads is sufficient, to lower thevoltage and make it compatible with theimpulse withstand voltage of the equipmentto be protected (see installation constraintspage 9).

Example figure 1

E: equipment to be protected with impulse

withstand of 1.5 kV

P1: incoming protection device dimensioned with Inand Imax that are sufficient enough to face lightning

currents that may appear and with a level of

protection of 2.5 kV

P2: surge arrester near equipment to be protected

with an adapted level of protection and which is

co-ordonated with P1

#

if sensitive equipment is too far from theincoming protection device(d 30 m figure 2):5

a secondary protection surge arrester (P2)placed near loads suffices, to lower the volta-ge and make it compatible with the impulsewithstand voltage of the equipment to be pro-tected (see installation constraints page 9).

Example figure 2


withstand of 1.5 kV

P1: incoming protection device dimensioned with In

and Imax that are sufficient enough to face lightningcurrents that may appear and with a level of

protection of 1.5 kV. This level of 1.5 kV is

acceptable in principle (even though there is no

margin), but the distance d is too great




Up surge arrester < Uchoc switchgearP1

P1 P2

E

E

Up:

1.2 kV

E57353

P1

P1 P2

d 30 m

E

E

E57354

servicespractical advice

Up:2 kV

Uchoc:1.5 kV

Up:

2 kVUchoc:

1.5 kV

France


2/1292506E.fm/3Schneider Electric Updated: 21/02/02


installation without a lighting conductor

(*) recommended

(1) since in the tertiary/industrial sector the cost of equipment to be protected is higher, damage

due to lightning is more significant

lightning flash density (Ng)

in function of the sitescharacteristics

installation with a lighting conductor#

if a lightning rod is planned or has already been installed on the building(or in a 50 m radius):5 choose an incoming protection device with an Imax 65 kA.

#

mount a secondary protection surge arrester Imax: 8 kA if:5

the distance between the incoming surge arrester and loads is 30 m5

the surge arresters voltage Up is too high in regards to the sensitivity of the loadto be protected (Uchoc), (see page 2).

residentiel

geographical location urban rural


Imax (kA) incoming protection 15* 15 15 15 30-40 65

Imax (kA) secondary protection if:Up too high and/or d 30 m

8 8

0.5 0.5




choice depending on the

earthing system

earthing systems TT TN-S TN-C ITdistributed IT non-

neutral distributed

neutral

class 2 test draw-out surge arrestersPRD MC 1P

Uc = 440 V 3P 3P

MC/MD 1P+N 1P+N 1P+N

Uc = 440/275 V 3P+N 3P+N 3P+N

class 2 test fixedsurge arresters

PF 30-65 kA MC 1P+N 1P+N 1P+N

Uc = 440 V 3P+N 3P+N 3P+n

PF 8-15 kA MC/MD 1P+N 1P+N 1P+N

Uc = 440/275 V 3P+N 3P+N 3P+N

PE MC 1P

Uc = 440 V 3x1P 3x1P

servicespractical advice France




in function of the technicaldata for loads

#

the surge arresters level of protection (Up)depends on the installed equipment and therated voltage of the installation

#

Up must lie between:5

the full voltage of the permanent operatingconditions (Uc)5 the impulse withstand voltage (Uchoc) ofthe equipment to be protected.

8/20 impulse withstand table for equipment to be protected#

general standard: IEC 60364-4

rated voltage equipment sensitivity withstand (Uchoc)of the installation

threephase reduced normal high very high

Uc < Up < Uchoc networks electronic circuit electrical household industrial industrial

devices: appliances: devices: devices

televisions, alarms, HiFi, dishwashers, ovens motors, distribution electric

video recorders, computers refrigerators, protable cabinets, current meters,

telecommunication tools sockets, transfos. telemeters

400/690/1000 2.5 kV 4 kV 6 kV 8 kV

230/440 V 1.5 kV 2.5 kV 4 kV 6 kV

shock wave shock wave shock wave shock wavecategory I category II category III category IV

permanent operating full withstand voltage Uc as in the IEC 60364-5-534 standard

earthing systems TT TN-S TN-C IT

Uc value for common mode 1.5 Uo 1.1 Uo 1.1 Uo 1.732 Uo

(protection between live conductors and earth)

Uc value for differential mode 1.1 Uo 1.1 Uo 1.1 Uo

(protection between phase and neutral)

Uo: simple network voltage between phase and neutral

Uc: full voltage under permanent operating conditions

placing several surge arresters in a cascading configuration

The incoming protection device (P1) isdimensioned to run-off lightning currents at thesource of the installation, 2 cases are possible:#

if there is a level of protection (Up) too highfor the impulse withstand voltage (Uchoc) ofthe installations equipment:5

a secondary protection surge arrester (P2)placed near loads is sufficient, to lower thevoltage and make it compatible with theimpulse withstand voltage of the equipment tobe protected (see installation constraintspage 9-10).

Example figure 1


withstand of 1.5 kVP1: incoming protection device dimensioned with In

and Imax that are sufficient enough to face lightning

currents that may appear and with a level of

protection of 2.5 kV




# if sensitive equipment is too far from the in-coming protection device (d 30 m figure 2):5

a secondary protection surge arrester (P2)placed near loads suffices, to lower thevoltage and make it compatible with theimpulse withstand voltage of the equipmentto be protected (see installation constraintspage 9-10).

Example figure 2


withstand of 1.5 kV

P1: incoming protection device dimensioned with In

and Imax that are sufficient enough to face lightningcurrents that may appear and with a level of

protection of 1.5 kV. This level of 1.5 kV is

acceptable in principle (even though there is no

margin), but the distance d is too great




Up surge arrester < Uchoc switchgear

P1

P1 P2

d 30 m

E

E

E57354

Up:1.2 kV

E

E

P1

P1 P2

E

E

Up:

1.2 kV

E57353


Up:

2 kV

Up:

2 kV

Uchoc:

1.5 kV

Uchoc:

1.5 kV

Export





installation without lighting-rod#

the following table determines the maximum current of the surge arrester(s) to be installed

according to geographic situation and lightning stroke density of the site to be protected.#

mount a secondary protection surge arrester Imax: 8 kA if:5

the distance between the incoming surge arrester and loads is 30 m5

the surge arresters voltage Up is too high in regards to the sensitivity of the load to be protected(Uchoc) (see page 5).

residential

geographical location urban rural


Imax (kA) incoming protection 15* 15 15 15 30-40 65

Imax (kA) secondary protection if:Up too high and/or d 30 m

8 8

(*) recommended

tertiary/industrial (1)

continuity of supply of the not necessary partial mandatory

operation

consequence (financial) low high very high

of a lightning stroke on

equipment to be protected


Imax (kA) incoming protection 15 15 30-40 15 30-40 65 30-40 65 65

Imax (kA) secondary protection if: 8 8 8 8 8 8

Up too high and/or d 30 m

(1) since in the tertiary/industrial sector the cost of equipment to be protected is higher, damage due to

lightning is more significant

0.5 0.5





Installation with lightning rod#

presence of a lightning rod on the building or in a radius of 50 m can cause a direct lightningstroke generating a rise in potential of the frames and of the earth network. Part of thelightning current rises in the electrical installation through the earthing electrode then theearthing strip.#

to protect the loads, it is then necessary to install at the incoming side of the switchboard,a PRF1 class 1 test surge arrester with a very high drain-off capacity (limp 20 kA) and ableto arc and then conduct the lightning current to a remote earth referenced at O V, while alsoensuring a level of protection of 4 kV maximum between phase/neutral and earth.#

as this level of protection is too high, another surge arrester must be added in cascade, sothat residual voltage at the terminals of the second surge arrester lmax = 30-40 kA (PRD40,PF30, PE40 or STM) is compatible with the impact withstand voltage of the equipment to beprotected (impact U < 1.5kV)#

finally, if the loads to be protected are more than 30 m from the incoming protection, a fineprotection surge arrester lmax 8 kA will be installed (PRD8, PF8, PE8, STD) as close aspossible to the loads.

E91263

if d4

30 m

incomer end protection secondary protection


E91007





earthing system(PRF1)


neutral distributed

neutral


PRF1 2x1P 2x1P

4x1P 4x1P 3x1P


earthing system

(PRD and ST offer)


neutral distributed

neutral

class 2 test draw-out surge arresters

PRD MC 1P

Uc = 275 V

MC 3P

Uc = 440 V 3P


Uc = 440/275 V 3P+N 3P+N 3P+N


STH-STM MC 1P+N 1P

FORBIDDEN

Uc = 275 V 3P+N 3P

STD MC 1P

Uc = 275 V 3P


Uc = 440/275 V 3P+N 3P+N 3P+N


earthing system(PRD, PF and PE offer)


neutral distributed

neutral

class 2 test draw-out surge arresters

PRD MC 1P

Uc = 275 V

MC 3P

Uc = 440 V 3P


Uc = 440/275 V 3P+N 3P+N 3P+N


PF 30-65 kA MC 1P+N 1P+N 1P+N

Uc = 440 V 3P+N 3P+N 3P+N

PF 8-15 kA MC/MD 1P+N 1P+N 1P+N

Uc = 440/275 V 3P+N 3P+N 3P+N

PE MC 1P

Uc = 440 V 3x1P 3x1P

servicespractical advice Export




choosing a disconnectioncircuit-breaker

class 1 test surge arresters After having chosen the surge arrester(s)needed to protect the installation, theappropriate disconnection circuit-breaker is

to be chosen from the opposite table:#

its breaking capacity must be compatiblewith the installations breaking capacity#

each live conductor must be protectedexample: a 1P+n surge arrester must becombined with a 2P disconnectioncircuit-breaker (2 protected poles).

disconnectionPRF1 fuse circuit-breaker

Iimp: 60 kA 125 A Max. compact NS160HgL (22 x 58) TM125D Max.

class 2 test surge arrestersmax. lightning disconnection circuit-breakerdischarge current rating curve

8-15-30-40 kA 20 A C

65 kA 50 A C

installation constraintsclass 2 test surge arrester

the 50 cm rule in the switchboardConnections must be as short as possible.

Do not exceed a distance of 50 cm, toefficiently protect electrical loads.

co-ordinating 2 surge arresters (the 10 m rule)#

In the case of an exposed site and thepresance of sensitive loads, it is recommended to co-ordinate upstream and downstream protection in a cas-cading configuration.

O-OFF

O-OFF

T

OFF

O-OFF

O-OFF

O-OFF

O-OFF

NL

MERLIN G

ERIN

C40r-275

Imax:40kA(8/20

)

In:15kA(8/20)

Up:1,2kV

Uc:275V

multi 9

PRDMER

LINGERIN

C Neutra

lr

multi 9

PRD

d1

d2

d3

PRD

d1+d2+d3

50cm

2

type

or delayed

O-OFF

O-OFF

NL

MERLINGE

RIN

multi9

PRDMER

LINGERIN

CNeutral r

multi9

PRD

O-OFF

O-OFF

NL

MERLINGE

RIN

multi9

PRDMER

LINGERIN

C Neutral r

multi9

PRD

O-OFF

O-OFF

incomerend

protection

secondaryp

rotection


E57321

E57322




installation constraints PRF1class 1 test surge arresterPRF1 surge arrester with reactor#

if the distance between the two incoming protectionsurge arresters is < 15 m, mount an L40A decouplingcoil cat. n. 16640 in series.

PRF1 surge arrester without reactor#

if the two incoming protection surge arresters are installed in separate switch-boards, more than 15 m apart, the decoupling coil is not required.

E57662

E57662

E57603

E57626

#

The 50 cm rule also applies to connection of the PRF1 surge arrester

E57602

STM STM

O-OFF

O-OFF

NL

MERLINGER

IN

multi 9

PRDMERL

INGERIN

C Neutr

al r

multi 9

PRD

O-OFF

O-OFF

limp=60k

A

Up 4kV

Uc=255V

50HzAC

Q=30As

1 6 6 2

0

MERLING

ERIN

PRF1

MERLIN GE

RIN

limp= 60

kA

Up 4kV

Uc=255V

50HzAC

Q= 30As

1 6 6 2 0

PRF1

Un 500V

50/60Hz

In40A

Ln=15H

1 6 6 4 0

MERLING

ERIN

L40A

Un 500V5

0/60Hz

In 40A

Ln= 15

H

1 6 6 4 0

MERLINGE

RIN

L40A

PF, PE

PRD, STM

NL

multi 9

PRD

C Neutra

lr

multi 9

PRD

limp= 60

kA

Up 4kV

Uc=255V

50HzAC

Q= 30As

1 6 6

2 0

PRF1

limp =60kA

Up 4kV

Uc= 255

V50HzAC

Q=30As

1 6 6

2 0

PRF1

O-OFF

O-OFF

O-OFF

O-OFF

PF, PE

PRD, STM

limp=60kA

Up4kV

Uc= 255V50

HzAC

Q=30As

1 6 6 2

0

MERLIN

GERIN

PRF1

limp =60kA

Up 4kV

Uc=255V5

0HzAC

Q=30As

MERLING

ERIN

1 6 6 2 0

PRF1

T

OFF

O-OFF

O-OFF

O-OFF

O-OFF

d1

d2

d3

d1+d2

+d350

cm

125 A Max.gL (22x58)

Compact NS 160HTM125D Max.

PRF1

16 35 mm2

16 50 mm2




surge arresterschoosing surge arresters for :LV networks (continued)communication networks

case of earth leakage

devices

The best way to guarantee the continuity ofsupply of priority circuits, while ensuring

safety in the case of atmosphericdisturbances is to combine:#

a surge arrester that can protect sensitiveloads against atmospheric overvoltages#

a circuit-breaker with an upstream earthleakage protection device of 300/500 mAselective, to ensure total earth leakagediscrimination#

a residual current device of 30 mA and "si"type placed downstream is insensitive to thistype of disturbance.

Another solution can be foreseen: use acircuit-breaker (not earth leakage) at the

incoming end of the installation followed bya residual current circuit-breaker. The surgearrester is to be connected between the twodevices (see below).Careful, the link L must be class II.

In installations fitted out with a general earthleakage protection, it is preferable to placethe surge arrester upstream from thisprotection.However, certain power distributors do notallow intervention at this distribution level(this is for instance the case for LVsubscribers in France).It is therefore necessary to plan a selectivedevice of the

P

type, or with delayedtripping, so that when the current runs off tothe earth through the surge arrester, it doesnot produce nuisance tripping of theincoming circuit-breaker.

ID "si"30 mA

ID

30 mA

residual current

device of the2

type or delayed

disconnection

circuit-

breaker

surge

arrester

other circuits prioritycircuits

L: class II link

circuit-

breaker

combined

with RCCB

uses

residual

current

circuit-

breaker

surge arrester

disconnection

circuit-

breaker

surge

arrester

uses

high

sensitivity

selective

RCD

with the earth

leakage

protection

device of the

2

type

residual current

device of the2

type or delayed

choice depending on thecommunication network

type of network series PRC PRI 1248 V PRI 6 V

telecommunication

digital 300 Hz RTC

numeris access T0

specialised 24 V line

specialised modem line base

band 64 kbit/s

MIC line and access T2

computer

current loop 200 V

current loop 1248 V

RS 232 (12 V)

RS 485 (12 V)

current loop 6 V

RS 422 (6 V)

RS 423 (6 V)

supply 12/48 V

fire safety centralising equipment,

ELV load, intrusion centralising


E57324

E57325

E573256



end of life surge arresters for LV networksAt the end of its life the surge arrester or itscartridge is destroyed, this can be one of 2

types:#

internal end of life disconnection:5

the accumulation of electrical shockscauses the varistors to age, which translatesinto a rise in the leakage current, above 1mA there is thermal runaway anddisconnection of the surge arrester#

external end of life disconnection:5

is produced when an overvoltage is tooenergetic (lightning stroke directly on theline), above the surge arresters flowcapacity there where the varistors areplaced in solid short-circuit with the earth (or

possible between the phase and neutral)5

this short-circuit is eliminated by themandatory disconnection circuit-breaker.

surge arresters for communicationnetworksThe surge arrestor is only at the end of life inshort-circuit, following the accumulation ofelectrical shocks which causes it to age orfollowing an overvoltage that is tooenergetic.

indication PRD65r and PRD40r surge arrestersThese surge arresters include:#

a built-in NO/NC remote indication contact# a mechanical indicator on the front panelwith a power reserve:5

white: normal operation (1)5

white/red: cartridge to be replaced in thenear future (2)5

red: cartridge to be immediatelyreplaced (3).

series PRD65, PRD40, PRD15, PRD8,PE40, PE15, PE8, ST, PRC and PRI surgearrestersThese surge arresters include:#

a mechanical indicator on front panel:5

white: normal operation

5

red: surge arrester to be immediatelyreplaced.

PE65 surge arrestersThese surge arresters include:#

a mechanical indicator on the front panelwith a power reserve:5

white: normal operation

5

white/red: cartridge is to be replaced in thenear future5

red: surge arrester is to be immediatelyreplaced.

PF surge arresters

These surge arresters include:#

a built-in remote indication NC contact forthe PF65r and PF30r models#

an orange light indicator on the front panel:5

not lit: normal operation5

flashing: surge arrester to be immediatelyreplaced.

14 11 12

E57214

(1)

14 11 12

E57217

(2)

14 11 12

E57215

(3)

indication by the circuit-breaker#

end of life is indicated by the opendisconnection circuit-breaker#

the best indication consists in indication ofthe continuity of protection, which is linked tothe closing of the upstream circuit-breakerthat is combined with an SD contact and

surge arrester operation indication using:

5

the transfer contact that is built-into thePF65r, PF30r, PRD65r and PRD40r surgearresters (diagram 1)5

or an EM/RM indication auxiliary(diagram 2)

diagram 1 (example PRD) diagram 2

11 12

NL

MERLING

ERIN

Imax. :65

kA

Un : 230 V

~

Uc :440

V~

In :20kA

Up:1,8k

V

multi 9

PRDMER

LINGERIN

Imax. : 6

5 kA

Un :230 V

~

Uc:4 40

V~

In:20 k

A

Up:1,8

kV

multi 9

PRD

O-OFF

O-OFF

SD

O-OFF

O-OFF

14 11

12

indicator

disconnect

ion

circuit-

breaker

surge

arrester

0.5mm

2 1.5m

m2

12VDC-

10mA

250VAC-

1A

2A

1 51 5

2 4

6O-O

FF

O-OFF

O-OFF

O-OFF

EMUn:

230Va

NL

MERLINGE

RIN

C40r-275

Imax:40kA

(8/20)

In:15kA(8/2

0)

Up:1,2kV

Uc:275V

multi 9

PRDMERL

INGERIN

CNeutral

r

multi 9

16562

RMUn : 2

30Va

250VAC-

50Hz

6VDC-

10mA

250VAC-

50Hz-5

A


surge arrestersend of life and indication

E57243

E57320


12/12

installation#

adaptable on PRD, PE, ST, PRI and PRCsurge arresters#

the EM/RM modules allow for up to 15surge arrester modules of 18 mm with a limitof 270 mm to be monitored using an opticallink#

the EM emitter is mounted to the left, theRM receiver to the right#

the RM receiver includes an NO/NCremote transfer contact for the combinedsurge arrester(s)#

supply of the EM/RM modules must beprotected by a breaking device(2 A).

technical data#

power:5

min.: 6 V DC and 10 mA5

max.: 250 V AC and 5 A#

isolation:5 between contacts: 1 kV AC5

between the contacts and the coil:2.5 kV AC.

indication#

the 2 green indicators are lit up and thered indicator is not:5

EM/RM modules: OK5

surge arrester(s): OK#

the green EM indicator is lit up,the red indicator is lit up:5

EM/RM modules: OK5

verify the status of the surge arrester(s)#

all indicators are extinguished:5

verify the supply of modules.

1 5

1 5

2 46

O-OFF

O-OFF

EMUn:

230Va

O-OFF

O-OFF

NL

MERLINGE

RIN

C40r-275

Imax:40kA

(8/20)

In:15kA(8/2

0)

Up:1,2kV

Uc:275V

multi 9

PRDMERL

INGERIN

CNeutral r

multi 9

PRD

16562

RMUn: 2

30 Va

2A

250VAC-

50Hz

6VDC-

10mA

250VAC-

50Hz-5

A

NL

EMUn:2

30Va

RMUn:2

30Va

16592

16592

opticallink

EMemitter

RMreceive

r

redfault

indicator

NO/NCcon

tactgreeni

ndicator

forcorrectoperat

ion

greenindic

ator

forcorrect

operation

PRD / PE / ST / PRC / PRI

EM RMPRD...

2 4 6

OK

PRD / PE / ST / PRC / PRIEM RM

PRD...

2 4 6


surge arrestersEM/RM remote indication modules

additionalinformation

dimensions : page 90148/2conseils pratiques : page 92506/2

E57318

E57319

E57337

Date post:	14-Apr-2018
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Choosing Surge Arresters for LV Networks

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