How to protect asecondary school
against the effects of lightning?

Customer needs
This secondary school has several buildings
including:•• 2 ”day school” and ”boarding school”
2-storey buildings with lift•• 1 gymnasium: dressing rooms andsports field•• 1 half-board building: restaurant andkitchen•• 1 technical workshop and gas boiler
room•• 1 administrative building and housing for
employees.
This site must comply with the regulations forprotection against fire,it has a safety system and fire alarm likeall school establishments or holiday campswhich have sleeping areas.
It is recommended to monitor the continuityof supply of automatic detection devices
and fire alarms for all circonstances
including atmospheric voltage surges.

Environment•• Located in the suburbs of a large city, this etablishment may besubjected to atmospheric voltage surges from near or far lightning
strokes (high trees around)•• The local lightning density is moderate (0.5 < Ng < 1.6)•• It has a TN-S earthing system•• The equipment to be protected is moderately expensive, however
the establishment does not have a large budget to cover for risks(and thus replacement), sensitive devices must therefore bewell-protected: electron microscopes, measurement devices,electronic and computer equipment•• A great number of teaching devices and equipment havea reduced impulse withstand voltage (U choc y 1.5 kV) in
particuliar for lab workshops:
biology, chimistry, electronics and computer rooms require
suitable protection against lightning as near as possible to loads.
The same is true for alarm and fire detection devices.
The building, traditional construction, does not have any specialearthing device, however is in compliance with the standards in force.
•• The secondary school is supplied by a low voltage three-phase+ neutral underground line that is supplied by the local utility.
The other supply networks: gas, telecommunications and water are
undergroud as well.

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FA12A3EN

How to protect asecondary school
against the effects of lightning?
Proposed solution

Solution diagram

The main LV distribution board MSB1 installed in the technical roomin the day school building, has a Type 1+2 surge protection device for theprotection against lightning (LV withdrawable
surge arrester iPRF1 12.5r associated with a 100 A disconnection
circuit-breaker).
The main LV distribution cabinet MSB2 installed in the technical roomfor external premises, has a Type 2 device for the protection against
lightning (LV withdrawal surge arrester iPRD40 associated with a 40 A
disconnection circuit-breaker).
Secondary distribution enclosures on each floor of the otherbuildings are protected by 8 kA LV surge arresters (surge arrester iPRD8associated with a 10 A disconnection circuit-breaker).
Telecommunication, monitoring and fire alarm devices are protectedby communication surge arresters of the type:•• iPRC, for analogue telephone networks,•• iPRI 12/48 V for digital telephone and PLC networks.

MV/LV

MSB 1

NG125
80 A
iPRF1
12.5r
12.5 kA(10/350)

Customer benefits
BoardingschooliIDs type•• Incoming surge arresters: run lightning current off to the groundand limit voltage surges on equipment located in the vacinity(within a distance of 10 m max.),

day school•• Secondary surge arresters: located near sensitive loads reducethe voltage between P-E and N-E so that the rated impulse
withstand voltage remains lower than 1500 V,•• In compliance with regulations.

Recommendations•• Make sure that building frames and earths are equipotentially bonded,•• Reduce loop surfaces.
•• Make sure that surge arrester incoming cables are at a distance fromthe installations outgoing cables,•• Always associate a disconnection circuit-breaker with the surgearrester,•• If the building is fitted out with a lightning conductor, both MSB1 andMSB2 should have Type 1+2 surge arrester PRD1 25r with a high run
off capacity (Iimp = 25 kA; Imax = 40 kA) with associated disconnector
Compact NSX 100B, 100 A.

Computerequipment

Boarding
school

iC60
10 A

iC60
10A

iPRD
8 kA

iPRD
8 kA

The role of the surge arrester disconnector•• Isolate the surge arrester from the rest of the installation in casethe surge arrester’s run off capacity Imax is exceeded, following aparticularly intense lightning stroke.
If the disconnector has been activated, loads are no longer protectedagainst atmospheric voltage surges.
Replacement of the surge arrester is thus recommended.

sockets

resid. halllighting

heatingliftéclairage

mefanschneider-electric.com 3

FA12A3EN

How to protect asecondary school
against the effects of lightning?

transformer
400 kVA

MSB 2

iC60
40 A
iPRD
40 kA

guard house

KitchenExternal

iC60
10 A

iC60
10 A

iPRD
8 kA

iPRD
8 kA

boiler room

stock roomheating

lighting
administration
external
main housing

workshop

KitcheniDPN Vigi
A-SI type

Gymnasium

iDPN Vigi
A-SI type

iC60
10 A
iPRD
8 kA

ech.
nhot
water

heating

biologie

class
rooms

stockroom

stockrooms

biologylaboratories

iPRD
8 kAlighting

firesystem
PLC,
electronics

iC60
10A

ovencashregisters

lightingmech.
fanheating

hot water

schneider-electric.com 4

FA12A3EN

How to protect asecondary school
against the effects of lightning?
Standards•• International installation standard IEC 60364-4-443 and 5-443 (09/2015)•• Electrical installation of buildings NF C 15 100 of 2002•• SPD are mandatory:•• in case of overheadlines and if lightning density is Ng u 2.5•• in case of presence of lightning rod (risk of direct impact).

Products used
ProductDescription

Unity

Cat. no.

iPRF1 12.5

Type 1+2 surge protection device 12.5kA

1-

NG125N

Miniature circuit breaker 80 A

1-

iPRD40Type 2 surge protection device 40 kA

1-

iPRD8

Type 3 surge protection device 8 kA

6-

iC60N

Miniature circuit breaker 40 A

1-

iC60N

Miniature circuit breaker 10 A

6-iID s type

Residual current device, selective type1-

iDPN Vigi A-SI type

Super-imunised residual current breaker

2-

Note: number of poles of MCB should be the same as SPD.

NG125

iPRF1 12.5r

iPRD8/iPRD40/
iPRD40r

iC60

iDPN Vigi
A-SI typeiID s type

iPRCseries

iPRI

Communication networks
protectionMore information:
For information concerning the protection of your electrical installation against lightning, please check our website or contact yourlocal Schneider Electric office.

35, rue Joseph Monier - CS 30323
F-92506 Rueil-Malmaison - FRANCE
Tél : + 33 (0) 1 41 29 70 00
Fax : + 33 (0) 1 41 29 71 00
www.schneider-electric.com

Document Number FA12A3EN © 2017 Schneider Electric. All rights reserved.