EN 50300:2004

SLOVENSKI STANDARD
01-junij-2004
Low-voltage switchgear and controlgear assemblies - General requirements for
low-voltage substation cable distribution boards
Low-voltage switchgear and controlgear assemblies - General requirements for low-
voltage substation cable distribution boards
Niederspannungs-Schaltgerätekombinationen - Allgemeine Anforderungen an
Niederspannungsverteilungen in Netzstationen
Ensembles d'appareillage à basse tension - Règles générales pour les tableaux de poste
basse tension
Ta slovenski standard je istoveten z: EN 50300:2004
ICS:
29.130.20 Nizkonapetostne stikalne in Low voltage switchgear and
krmilne naprave controlgear
29.240.99 'UXJDRSUHPDY]YH]L] Other equipment related to
RPUHåML]DSUHQRVLQ power transmission and
GLVWULEXFLMRHOHNWULþQHHQHUJLMH distribution networks
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN 50300
NORME EUROPÉENNE
EUROPÄISCHE NORM April 2004
ICS 29.130.20
English version
Low-voltage switchgear and controlgear assemblies –
General requirements for low-voltage
substation cable distribution boards

Ensembles d'appareillage à basse tension - Niederspannungs-
Règles générales pour les tableaux Schaltgerätekombinationen –
de poste basse tension Allgemeine Anforderungen an
Niederspannungsverteilungen in
Netzstationen
This European Standard was approved by CENELEC on 2004-03-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,
Switzerland and United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2004 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 50300:2004 E
Foreword
This European Standard was prepared by the Technical Committee CENELEC TC 17D, Low-voltage
switchgear and controlgear assemblies.
The text of the draft was submitted to the formal vote and was approved by CENELEC as EN 50300 on
2004-03-01.
This European Standard is to be used in conjunction with EN 60439-1:1999.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2005-03-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2007-03-01
__________
– 3 – EN 50300:2004
Contents
Page
Introduction.4
1 General .4
2 Definitions .5
3 Classification of ASSEMBLIES.6
4 Electrical characteristics of ASSEMBLIES .7
5 Information to be given regarding the ASSEMBLY .7
6 Service conditions.7
7 Design and construction.8
8 Test specifications .11
Annex A (normative) Cross-sections of conductors .21

Figures
Figure 101 – Typical enclosure mounting arrangements for mechanical strength tests .22
Figure 102 – Testing arrangement for the verification of resistance to static load .22
Figure 103 – Sandbag for test to verify resistance to shock load .23
Figure 104 – Diagram of test to verify resistance to shock load.23
Figure 105 – Diagram of test to verify resistance to torsional stress .24
Figure 106 – Diagram of test to verify impact force withstand.24
Figure 107 – Diagram of test to verify mechanical strength of door .25
Figure 108 – Striker element for test of resistance to impact by sharp edged objects .25

Tables
Table 101 – List of additional verifications and tests .12
Table 102 – Axial load to be applied to the inserts .16
Table A.1 – Minimum and maximum cross-sections of copper and aluminium
conductors suitable for connection (see 7.1.3.2).21

Introduction
The clauses of this standard supplement, modify or replace clauses in EN 60439-1:1999, Low-voltage
switchgear and controlgear assemblies - Part 1: Type-tested and partially type-tested assemblies.
Where there is no corresponding clause or subclause in this standard, the clause or subclause of the
main document applies without modification.
In view of the fact that this publication is to be read in conjunction with EN 60439-1, the numbering of
its clauses and subclauses correspond with the latter.
Subclauses, figures and tables which are additional to those in EN 60439-1 are numbered starting
from 101.
1 General
1.1 Scope and object
This standard gives supplementary requirements for low voltage switchgear and controlgear
assemblies for public distribution transforming sub-stations. They are stationary, type tested
assemblies (TTA) for installation in places where only authorised persons have access for their use,
however, outdoor types may be installed in situations which may be accessible to the public.
They are connected to the low voltage terminals of distribution transformers by means of connecting
bars, rods or cables and are for use in low voltage public three phase systems.
Individual components such as fuses and switching devices complying with other standards, shall also
comply with the supplementary requirements of this standard.
The object of this standard is to state the definitions and to specify the service conditions, construction
requirements, technical characteristics and tests for Substation Cable Distribution Boards. Network
parameters may require type tests at higher performance levels.
NOTE Where local regulations and practices permit, a Substation Cable Distribution Board to this standard may be used in
other than public networks as agreed between the manufacturer and the user.
1.2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
EN 60068-2-11:1999 Environmental testing -- Part 2: Tests - Test Ka: Salt mist
(IEC 60068-2-11:1981)
EN 60068-2-30:1999 Environmental testing -- Part 2: Tests - Test Db and guidance: Damp heat,
cyclic (12 + 12 hour cycle) (IEC 60068-2-30:1980 + A1:1985)
EN 60238:1998 Edison screw lampholders (IEC 60238:1998)
EN 60269-1:1989 Low-voltage fuses -- Part 1: General requirements (IEC 60269-1:1986)
EN 60439-1:1999 Low-voltage switchgear and controlgear assemblies -- Part 1: Type-tested
and partially type-tested assemblies (IEC 60439-1:1999)

– 5 – EN 50300:2004
and partially type-tested assemblies (IEC 60439-1:1999)
EN 60445:2000 Basic and safety principles for man-machine interface, marking and
identification - Identification of equipment terminals and of terminations of
certain designated conductors, including general rules for an alphanumeric
system (IEC 60445:1999)
EN 60446:1999 Basic and safety principles for man-machine interface, marking and
identification - Identification of conductors by colours or numerals
(IEC 60446:1999)
EN 60529:1991 Degrees of protection provided by enclosures (IP Code) (IEC 60529:1989)
EN 60695-11-10:1999 Fire hazard testing -- Part 11-10: Test flames - 50 W horizontal and vertical
flame test methods (IEC 60695-11-10:1999)
EN ISO 3231:1997 Paints and varnishes - Determination of resistance to humid atmospheres
containing sulfur dioxide (ISO 3231:1993)
EN ISO 4892-2:1999 Plastics - Methods of exposure to laboratory light sources - Part 2: Xenon-arc
sources (ISO 4892-2:1994)
EN ISO 6506 (series) Metallic materials - Brinell hardness test (ISO 6506 series)
ISO 4628-3:1982 Paints and varnishes - Evaluation of degradation of paint coatings -
Designation of intensity, quantity and size of common types of defect –
Part 3: Designation of degree of rusting
ISO 9223:1992 Corrosion of metals and alloys - Corrosivity of atmospheres - Classification
2 Definitions
For the majority of the definitions required in connection with this standard see Clause 2 of EN 60439-1.
For the purpose of this standard the following additional definitions shall apply.
2.1.100 Additional general definitions
2.1.101
substation cable distribution board (SCDB)
ASSEMBLY for stationary installation connected directly or through an incoming circuit to a distribution
transformer. The ASSEMBLY contains busbars connected to the incoming circuit to enable electrical
energy to be distributed to one or more outgoing circuits which may have current breaking and/or
switching devices for the protection and isolation of the outgoing cable or overhead line. It is installed,
operated and maintained solely by skilled persons
2.1.102
SCDB - indoor (SCDB-I)
substation cable distribution board (SCDB) for installation indoors, generally without an enclosure, or
outdoors, in a weather protected enclosure. It comprises structural parts which are suitable for
supporting busbars, a group of functional units, with fuses or switching devices and other ancillary
devices, for the purposes of protecting, controlling and/or connecting one or more outgoing circuits fed
from one or more incoming circuits

2.1.103
substation cable distribution board - outdoor cable connected (SCDB-CCO)
cubicle type substation cable distribution board (SCDB) for outdoor installation which is independently
mounted and connected to the distribution transformer by means of cables
2.1.103.1
SCDB-CCO - ground mounted
SCDB-CCO suitable for outdoor installation at or slightly above ground level in a situation which may
be accessible to the public
2.1.103.2
SCDB-CCO - pole mounted
SCDB-CCO suitable for outdoor installation above ground level on a pole
2.1.104
substation cable distribution board - outdoor transformer mounted (SCDB-TMO)
cubicle type substation cable distribution board (SCDB) for outdoor installation, which is suitable for
fixing to the low voltage flange of a distribution transformer
2.1.104.1
SCDB-TMO - ground mounted
SCDB-TMO which is suitable for fixing to the low voltage flange of a ground mounted distribution
transformer
2.1.104.2
SCDB-TMO - pole mounted
SCDB-TMO which is suitable for fixing to the low voltage flange of a pole mounted distribution
transformer
2.2 Constructional units of ASSEMBLIES
2.2.1
section (see Figure C.4)
Not applicable.
2.2.2
sub-section
Not applicable.
2.2.3
compartment
Not applicable.
3 Classification of ASSEMBLIES
Delete:
- the conditions of installation with respect to mobility (see 2.5.3 and 2.5.4);

– 7 – EN 50300:2004
4 Electrical characteristics of ASSEMBLIES
4.101 Rated current (of a SCDB)
The rated current of a SCDB is that stated by the manufacturer as the rated current of the incoming
circuit. If there is more than one incoming circuit, the rated current of that SCDB is either, the arithmetic
sum of the rated currents of all incoming circuits that are intended to be used simultaneously, or the
rated current of the main phase busbars, whichever is the lower value. This current shall be carried
without the temperature rise of the individual parts exceeding the limits specified in 7.3 when tested
according to 8.2.1.
5 Information to be given regarding the ASSEMBLY
5.1 Nameplates
Replace t) by u) in the third paragraph.
Add to the list at end of the subclause:
u) rated current of the SCDB as defined in 4.101 of this standard.
Nameplates may be placed inside enclosures of SCDB provided their intended place provides good
legibility and visibility when the door is open or the cover is removed.
NOTE Further information may be included by agreement between the user and the manufacturer.
5.2 Markings
Add at the end of the subclause:
It shall be possible to identify the circuit designation of each functional unit in a position clearly visible
from the front of the ASSEMBLY when the door(s), if any, giving access to the operating face, are
open.
In the case of removable fuse-carriers which are specific to a fuseway, a label shall be placed on the
fuse-carrier as well as on the fuse-base, to avoid incorrect interchanging of the fuse-carrier.
6 Service conditions
6.2 Special service conditions
6.2.8 Exposure to heavy vibration and shocks
Add the following note:
NOTE Exposure to traffic vibration is a normal service condition for all ground mounted types of SCDB.

7 Design and construction
7.1 Mechanical design
7.1.1 General
Add the following paragraphs at the end of the subclause:
Design requirements
The insulating materials used for enclosures, barriers and other parts shall have a resistance to
abnormal heat and flame in accordance with 8.2.102.
A metal frame or enclosure shall incorporate a suitable earth terminal of an appropriate size to provide
a connection for an external protective conductor, except in case of protection by total insulation.
When the SCDB does not have the means of measurement incorporated, it shall be possible, by the
use of a portable instrument, to readily and safely measure the voltage in all phases of incoming units
and on both sides of all current breaking and/or switch devices of outgoing units, also the current in
one phase of outgoing units. During this operation all live parts of the SCDB shall be protected
sufficiently to retain the required degree of protection in accordance with 7.2.1.5. Instructions
concerning the procedure to be adopted shall be provided by the manufacturer.
NOTE 1 The type of protection required for measuring may be subject to agreement between the user and the manufacturer.
NOTE 2 Provisions for current measurements in more than one phase or in the incoming units may be agreed between the
user and the manufacturer.
If the switchgear is to be connected to live reserve power, for example a standby generator, the
switchgear's connecting device shall be designed so that the connection can be made with the live
parts having a degree of protection IP1X according to EN 60529.
NOTE 3 An alternative degree of protection may be applied, subject to agreement between the user and the manufacturer.
For a SCDB which is expected to feed overhead cable lines, outgoing units shall be designed in such a
way that an attached cable(s) can be earthed at the termination(s).
Protection against corrosion
The materials or coatings shall be subject to agreement between the user and the manufacturer and
shall be sufficient to pass the appropriate tests of 8.2.103.
Mechanical strength
The mechanical properties of the enclosure of a SCDB-CCO or a SCDB-TMO shall comply with
8.2.101.
In the case of a SCDB-I, a torsionally rigid frame construction shall be provided which is sufficiently
rigid to avoid any permanent distortion during installation. The frame together with its mounting shall be
sufficiently rigid to prevent distortion during the operation of its main circuits.
Parts of a SCDB-CCO intended to be embedded into the ground shall withstand the stresses imposed
during installation and normal service.

– 9 – EN 50300:2004
Ease of operation and maintenance and safety
All parts of the SCDB shall, as far as practicable, be readily accessible and replaceable without
extensive dismantling. The conditions for interchangeability of parts of the SCDB may be subject to an
agreement between the user and the manufacturer.
The design shall be such that the cables can be readily connected from the front.
If necessary, the protective conductor shall have a safely and easily accessible link to permit
disconnection when testing the circuit.
Locking arrangements shall be provided on a SCDB-CCO or SCDB-TMO to secure the door(s) and
prevent unauthorised access. The fixings of any other covers etc. which are removable for installation
or maintenance operations shall only be accessible while the door(s) are open.
NOTE The top cover or other appropriate surface of a SCDB-TMO may be designed to be removable in order to facilitate the
installation and maintenance operations.
7.1.2 Clearances, creepage distances and isolating distances
7.1.2.1 Clearances and creepage distances
Add at the end of the subclause:
Specific creepage distances shall be subject to agreement between the user and the manufacturer.
7.1.3 Terminals for external conductors
7.1.3.2 Replace paragraphs 1 and 2 by the following paragraphs:
In the absence of a special agreement between the user and the manufacturer, terminals shall be
capable of accommodating cables having copper or aluminium conductors from the smallest to the
largest cross-sectional area corresponding to the appropriate rated current (see Annex A, Table A.1).
Incoming circuits:
The design of a SCDB-I shall permit the use of incoming connections of either bare or insulated bars or
single-core or multi-core cables.
Outgoing circuits:
The terminations shall be located so that adequate spacing is provided and to facilitate terminating the
phase conductors of a cable irrespective of their lay.
7.2 Enclosure and degree of protection
7.2.1.2 Not applicable.
7.2.1.3 Replace the subclause by:
When a SCDB-CCO or SCDB-TMO is installed in accordance with the manufacturer’s instructions and
in an area which may be accessible to the public, its enclosure shall have a degree of protection of at
least IP33D according to EN 60529.
NOTE For the purposes of this subclause the enclosure of a SCDB-CCO or SCDB-TMO is defined in note 2 of subclause 3.1
of EN 60529. The note in subclause 13.3 of this stated publication does not apply for a SCDB-CCO or SCDB-TMO.

7.2.1.6 Not applicable.
7.3 Temperature rise
Add the following note:
NOTE 2 User network parameters may require additional tests and particular characteristics to be agreed between the user
and the manufacturer.
7.4 Protection against electric shock
7.4.2.2.3 Add at end of a):
A reliable locking device shall be provided on outdoor enclosures which prevents access by
unauthorised persons. Doors, lids and covers of a ground mounted type of SCDB-CCO or SCDB-TMO
shall be so designed that, after they are locked, they do not open due to subsequent moderate ground
settlement, nor due to traffic vibrations.
7.4.2.3 Protection by obstacles
Not applicable.
7.4.5 Operating and maintenance gangways within ASSEMBLIES
Not applicable.
7.6 Switching devices and components installed in ASSEMBLIES
7.6.1 Selection of switching devices and components
Add at the end of the first paragraph:
Fuses shall comply with the general requirements of EN 60269-1 or with the relevant National
Standard where there is established practice to use such a National Standard.
7.6.1.101 Earthing and short-circuiting means
The outgoing units in a SCDB shall be so constructed that they can be earthed and short-circuited in a
secure manner by means of a device(s) recommended by the manufacturer, which ensures the
manufacturer's indicated degree of protection (IP code) is maintained for all parts of the assembly. This
requirement for an earthing and short-circuiting means is not applicable if it could cause a safety
hazard arising from the system conditions and/or operational practice.
7.6.5 Identification
7.6.5.1 Identification of the conductors of main and auxiliary circuits
Replace first paragraph with:
With the exception of the cases mentioned in 7.6.5.2, the method and the extent of identification of
conductors, for example by arrangement, colours or symbols, on the terminals to which they are
connected or on the end(s) of the conductors themselves, shall be agreed between the user and the
manufacturer and it shall be in agreement with the indications on the wiring diagrams and drawings.
Where applicable, the identification according to Table 1 of EN 60445 and EN 60446 shall be applied.

– 11 – EN 50300:2004
8 Test specifications
8.1 Classification of tests
Replace the note by:
NOTE Verifications and tests to be performed on a SCDB are listed in EN 60439-1, Table 7 column TTA. Additional tests to be
performed on a SCDB are listed in Table 101 of this standard.
Add after the note:
The parameters of the user network may require additional tests that should be agreed between the
user and the manufacturer.
8.1.1 Type tests (see 8.2)
Add to the list:
h) verification of mechanical strength (8.2.101);
i) verification of resistance to abnormal heat and flame (8.2.102);
j) verification of corrosion and ageing resistance (8.2.103).
Replace the penultimate paragraph by:
The order for carrying out the tests and the number of samples to be tested may be changed subject to
an agreement between the user and the manufacturer.
8.2 Type tests
8.2.1 Verification of temperature-rise limits
8.2.1.1 General
Delete the last paragraph.
Table 101 – List of additional verifications and tests
Number Characteristics to be Subclause Requirements
checked number
12 Mechanical strength 8.2.101
12.1 Structural strength 8.2.101.1 Verification of:
12.1.1 Static load withstand 8.2.101.1.1 Static load withstand - type test
12.1.2 Shock load withstand 8.2.101.1.2 Shock load withstand - type test
12.1.3 Torsion stress withstand 8.2.101.1.3 Torsion withstand - type test
12.2 Impact strength 8.2.101.2 Verification of:
12.2.1 Impact force withstand 8.2.101.2.1 Impact resistance to steel ball - type
test
12.2.2 Impact force withstand 8.2.101.2.2 Impact resistance to steel ball and
force from hemispherical steel body
12.3 Door strength 8.2.101.3 Withstand moment - type test
12.4 Metal inserts strength 8.2.101.4 Resistance of metal inserts to axial
load - type test
12.5 Resistance to mechanical 8.2.101.5 Impact resistance to sharp-edged
shock impacts induced by objects - type test
sharp-edged objects
13 Insulating materials, 8.2.102 Verification of resistance to:
enclosures and barriers
13.1 Resistance to abnormal heat 8.2.102.1 Thermal stress - type test
13.2 Verification of flammability 8.2.102.2 Flammability category - type test
category
13.3 Dry heat test 8.2.102.3 Thermal stress - type test
14 Verification of resistance to 8.2.103 Verification of resistance to corrosion
corrosion and ageing and ageing - type test
NOTE 1 Tests 2, 3, 4, 7, 12.4 and 13.3 shall be conducted, in sequence, on the same sample; all other tests
may be conducted on separate samples at the discretion of the manufacturer.
NOTE 2 Test numbers 12 and 14 do not apply for an indoor type substation cable distribution board (SCDB-I).
NOTE 3 This table is an extension of Table 7 of EN 60439-1.

8.2.1.3 Temperature-rise test using current on all apparatus
Replace the first sentence of the second paragraph with:
For this test, the inc
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