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PROCEDURE AND REQUIREMENTS FOR INSTALLATION OF
ELECTRICAL EQUIPMENT
Heading
Designation
Cables
MBE 301
Version
3 en
Content
1
1.1
1.2
2
2.1
2.2
2.3
3
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
3.10
Designation
GENERAL...................................................................................2
Scope ...........................................................................................2
Prerequisites ................................................................................2
INSTALLATION REQUIREMENTS.........................................2
General Requirements .................................................................2
Requirements from Nuclear Regulations ....................................2
Standardisation ............................................................................3
INSTALLATION ........................................................................3
General ........................................................................................3
Lowest Installation Temperature for Various Cable Classes.......3
Smallest bending Radius for Cables when Installed ...................4
Max Tensile Force when Cables are Pulled Out .........................4
Laying Cable Out .........................................................................4
Allocation of Cables on Ladders, in Ducts in the same Sub and
Class ............................................................................................4
Laying Out Single Phase Cable ...................................................5
Optic Cables, Coaxial Cables and Computer Network Cables ...5
Cable Anchorage .........................................................................5
Temporary fire seals during installation work .............................6
Version
MBE 301
2016-03-08 (533580557)
Date
3 en
Replaces
2003-10-28
2 en
MBE 301
1
GENERAL
1.1
Scope
Version 3 en
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MBE 301 covers handling and installation of cables.
1.2
Prerequisites
Documents which specify the sub, class, the route the cable shall take, and the cable
type.
2
INSTALLATION REQUIREMENTS
2.1
General Requirements
Cables are an important part of the electrical installation, and it is therefore important
that cables are handled and treated correctly for reliable performance.
It is important that cables are handled with consideration given to their physical
properties to avoid impairing their desired performance, i.e. lowest installation
temperature, smallest bending radius and the tensile force to which they may be
subjected to. It is also important to protect the cable from being crushed and from sharp
objects, which could puncture the sheath and damage the insulation around the
conductors. If there is any risk that water could penetrate into the ends of the cables, the
ends should be sealed. Note that there is a general requirement for end sealing on some
types of cables, to maintain the level of insulation.
Cables must not be subjected to pressure, such as excessively hard clamping, pressure
against cable ladders etc. This causes the insulation material of the cable to cold flow,
which could cause the insulation to fail. This can cause a loss of signals or, in power
cables; an arc could occur and cause a fire.
If power cables have to be laid so that cooling is prevented, such as transitions through a
fire cell wall with insulating sealant, ambient temperature above 25C or where cables
have to be installed with closer spacing than the specified installation practice permits,
the responsible designer must be contacted to ask for new dimensioning of the cable
area.
Cables should not normally have joints along their lengths. If it is necessary to join a
cable, this must be done inside a junction box and must be documented.
2.2
Requirements from Nuclear Regulations
The minimum requirement for marking is at both ends of the cable and by wall
transitions, on each side of the wall transition. When a cable laid outside the main cable
route (secondary route), the marking may need to be supplemented so that it is easy to
see whether the separation between safety classified and operation classified cables is
satisfactory.
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Standardisation
Swedish standard SS 424 14 38 specifies general requirements for cable installation in
buildings and applicable sections. The standard complies with the Swedish National
Electric Regulations, ELSÄK-FS, and covers all types of cables up to power cables
rated for 24kV.
3
INSTALLATION
3.1
General
Cables and cable routes shall belong to the same sub and cable class unless otherwise is
specified. Non-conformance may only occur if a safety analysis is carried out and it is
found to be risk free. Cable routes, main cable routes and secondary cable routes are
covered in MBE 201. Clamping of individual cables on walls etc is treated as a
secondary cable route. Installation shall be done so that there is no risk that the cable
could be damaged by crushing, abrasion or wear, such as when covers and doors are
opened or in other circumstances which, could cause this type of damage.
Cables, conductors and spiral hoses shall be installed with protection against being
trodden on, either by considering the position or by providing extra protection.
Cables and conductors which pass through holes with sharp edges must be protected by
glands or spiral hose couplings.
Sharp edges or corners shall be provided with edge protection.
Cables and conductors shall be laid so that they are accessible for inspection.
When cables are installed on ladders or ducts, the cables shall be installed parallel.
Cutting corners etc. is not permissible.
Cables shall be cut with a cable cutter.
Cable installation on ladders and ducts in main cable routes shall be done in accordance
with the cable list/cable card.
Examples of cable cards and node drawings are found in MBE MI 3001.
Cables not documented in a cable schedule, must not be installed on cable ladders or in
cable ducts. Such cables shall be documented on a plan drawing and shall be installed in
tubes or clamped on walls.
3.2
Lowest Installation Temperature for Various Cable Classes
Cables with PVC insulation and sheaths do not just get stiff in cold weather; there is
also a risk of cracking if they are subjected to bending or impacts. Care must be taken
when they are taken out of an unheated store and if laid outdoors in cold weather. The
lowest temperature for handling and installing cables is noted in MBE MI 3002.
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Smallest bending Radius for Cables when Installed
The smallest bending radius, which a cable should be subjected to, depends on the type,
temperature and the number of times it is bent and straightened. Guidelines for various
types of cables see MBE MI 3003.
Opto cables, coaxial cables and computer network cables should be bent as in the
manufacturer’s instructions.
3.4
Max Tensile Force when Cables are Pulled Out
When pulled out, the maximum permissible tensile force in the cable is calculated in
accordance with the table in MBE MI 3004.
3.5
Laying Cable Out
Before the work of laying out the cable starts, the cable route should be clean and tidy. It
is also important to ensure that there is no risk that the cable could be damaged by other
activities performed at the same time as laying out, such as mechanical installation work
with welding, cutting etc.
Temporary markings shall be applied to the cable in conjunction with laying out.
Cables can be laid out in two ways:

By carrying out the cable, which is cut to the correct length after having been
wound off a cable drum mounted or suspended on some form of bearing, which
permits the drum to rotate.
 By pulling out the cable from a cable drum mounted or suspended on some form of
bearing which permits the drum to rotate. The cable should then be allowed to run
on rollers, laid along the cable path. The maximum tensile force must be checked
with a calibrated slipping clutch in the winch, a serial connected strain gauge
(calibrated scale or dynamometer), series connected breakable links or other checks
which effectively prevent the tensile force from exceeding the permissible value.
It is preferable to connect the winch directly to the conductors.
It is important that the rotation of the cable drum should be connected so that no jerks
occur when the cable is fed.
The location of cable reels to be put along the cable route and how the winches should
be used are noted in MBE MI 3102.
3.6
Allocation of Cables on Ladders, in Ducts in the same Sub and Class
If not otherwise specified in the design documents, the cables should be mounted as
follows
Class 1
Cables are only laid in one layer on the ladder. At least 30 mm spacing between the
cables and 10 mm between the cable and the sides of the ladder.
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Class 2
Cables are normally laid in one layer on the ladder.
Cables with conductor areas of 95 mm² or above shall be laid with at least 30 mm
spacing between the cables and 10 mm between the cable and the sides of the ladder.
Cables with conductor areas less than 95 mm² shall be laid without spacing, but not
tightly packed. Cables can be laid tight packed and in two or three layers for
components with intermittent operation, such as actuator motors.
When cables are installed vertically, of less than 95 mm², two layers are permissible
however, if cable clamps are used with packing between the cables.
Class 3
Cables can be laid in several layers in cable ducts.
Class 4
Cables can be laid in several layers in cable ducts.
Class 5
Only for neutron flow measurement. Special documentation is needed.
Class 6 (optic cable)
Can be laid in several layers in cable ducts
3.7
Laying Out Single Phase Cable
Single-phase cables shall be laid in three phase delta groups in accordance with MBE
MI 3104.
3.8
Optic Cables, Coaxial Cables and Computer Network Cables
The mechanical characteristics of optic cables are low weight, low permissible
mechanical loading and reduced ease of handling at low temperature.
The cable shall be laid so that it is not subjected to such pressures that its transmission
properties (ability to transmit optical signals) are affected. Plastic tie wraps shall be
used. The ends of optic cables should be sealed to avoid piercing and eye injuries.
Coaxial and computer network cables have similar mechanical properties to optic cables
and shall be handled in the same way. They must also be fixed with plastic tie wraps.
3.9
Cable Anchorage
When installed in an environment with severity A, cables shall be tied with tie wraps.
When installed in an environment with basic severity B or C, cables shall be tied with
plastic coated stainless steel wire. Exceptions shall be made for optic cables etc, as in
3.8.
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Clamps with a metal pressure plate can be used for metal armoured cables, power cables
and installation cables, and control and telecom cables with diameters greater than 20
mm.
Class 1 and 2
In horizontal installation or if the cable runs dip less than 30° from the horizontal plane,
cables shall be tied at each third rung of the ladder
On vertical ladders and horizontal ladders on edge, or if the cable runs dip more than
30° from the horizontal plane, cables shall be tied every other rung of the ladder.
Class 3, 4 and 6
In horizontal installation, or if the cable runs dip less than 30° from the horizontal plane,
cables shall be laid loose and parallel to each other and with the cable duct.
In vertical and horizontal ducts on edge, or if the cable runs dip more than 30° from the
horizontal plane, cables shall be tied every other anchorages of the duct.
Generally
Cables who lays vertical installation or with dip more than 30° shall be fixed starting
from the bottom, and continuing upwards, so that each fixing point bears the weight of
its section of cable.
Stainless steel clamps shall be used to clamp cables direct to walls and ceilings.
Recommended clamping distances etc. for fixing cables are specified in MBE MI 3005.
Consideration to the change in length of cables, depending on temperature variations in
operation, only needs to be given for stiff power cables which are installed in long
straight lengths. 1 mm/m of cable can be used as a guideline
In floor and wall transitions, the cables shall be well separated and parallel as far as
possible. This makes it easier for future hole drilling, cable installation and subsequent
sealing after changes. When sealed with module seals to make a pressure-tight joint, it is
a requirement that the cables should be parallel and at right angles to the seal.
Power cable with single conductor used for three phase transmission should be anchored
shown in MBE MI 3104.
3.10
Temporary fire seals during installation work
When work with cable installation is in progress through fire cell walls, temporary seals
shall be used until permanent seals are installed. See MBE 102 chapter 4.14
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