Cables are often the last component considered during system design even if in many situations cables are the true system’s lifeline: if a cable fails, the entire system may stop. Cable reliability is therefore extremely important, then a cable system should be engineered to last the life of the system in the installation environment for the required application. Environments in which cable systems are being used are often challenging, as extreme temperatures, chemicals, abrasion, and extensive flexing. These variables have a direct impact on the materials used for cable insulation and jacketing as well as the construction of the cable. Using a systematic approach will help ensure that designer select the best cable for the required application in the installation environment. This lessons will provide students main guidelines for perform this approach.

1. Angelo Baggini, angelo.baggini@unibg.it, Bergamo University - Engineering Department
Via Marconi 5, 24044 Dalmine (BG) – Italy
Leonardo Energy Academy
Power Quality
Principles of Cable Selection

2. Introduction
Cable sizing vs Cable selection
Cable sizing is the
process of selecting
appropriate sizes for
electrical power cable
conductors.
the process of
selecting appropriate
sizes for electrical
power cable
conductors
Cable sizing is the
process of selecting
appropriate sizes for
electrical power cable
conductors.
the process of
selecting the
appropriate type of
cable

3. Main topics
Main cable classification
Cable parts
Types of conductors
Insulation
Filler
Sheat
Screen
Armour

4. Main cable classification
(Rated voltages)
U0/U (Um)
U
U0
Um is the highest volage for the equipment i.e. the highest value of the phase-to-phase voltage
(r.m.s. value) for which the equipment is designed in respect of its insulation as well as other
characteristics which relate to this voltage in the relevant equipment Standards. Under normal
service conditions specified by the relevant apparatus committee this voltage can be applied
continuously to the equipment.

5. Main cable classification
(by voltage)
Low voltage power (and control) cables
up to 0.6/1 kV (Um = 1,2 kV)
Medium voltage power cables
1,8/3 kV (Um = 3,6) – 18/30 kV (Um = 36 kV)
High voltage power cables
26/45 kV (Um = 52 kV) – 220/380 kV (Um = 420 kV)

6. 1.1. LV Cable & Wire anatomy
CONDUCTOR
• Solid
• Stranded
INSULATION
SHEATH

7. 1.1. LV Cable & Wire anatomy
CONDUCTOR
• Solid
• Stranded
INSULATION
SHEATH FILLERS
BEDDING
CONCENTRIC PE
CONDUCTOR OR
ARMOUR OR
SCREEN

8. 1.1. LV Cable & Wire anatomy
CONDUCTOR
• Solid
INSULATION
(MgO)
SHEATH CONCENTRIC PE
CONDUCTOR

9. 1.1. MV and HV Cable anatomy
CONDUCTOR
INSULATION
SCREEN
SHEATH
CONDUCTOR
SCREEN
INSULATION
BEDDING
SCREEN
ARMOUR

10. 1.1. MV and HV Cable anatomy
CONDUCTOR
INSULATION
SCREEN
SHEATH
CONDUCTOR
SCREEN
INSULATION
BEDDING
SCREEN
FILLERS
SCREEN
ARMOUR

11. LV Cable & Wire designation
Cable Standard
H Harmonised Cable
A National Type of cable
N National unauthorized
S Special compliant
J Conforms IEC
Insulation Material
B Ethylene-propylene rubber
G Ethylene-vinyl-acetate
M Mineral
N Polychloroprene (or equivalent material)
N2 Polychloroprene for welding cables
R
Ordinary ethylene propylene rubber or
equivalent synthetic elastomer for a
continuous operating temperature of 60ºC
V Ordinary PVC
V2 PVC for temperature of 90 ° C
Z
Crosslinked polyolefins having low emission
of smoke, toxic gases and corrosive
Z1
Thermoplastic polyolefins having low
emission of smoke, toxic gases and
corrosive
Special construction
No SymbolCircular construction of cable
H
Flat construction of “divisible”
cables and cores, either sheathed
or non-sheathed
H2
Flat construction of “non-divisible”
cables and cores
H6
Flat cable having three or more
cores, according to DH 359 or EN
50214
H7
Cable having a double layer
insulation applied by extrusion
H8 Extensible lead
Conductor material
No Symbol Copper
-A Aluminium
Conductor shape
-D
Flexible conductor for use in arc welding cables to HD
22Part 6 (flexibilty different from Class 5 of HD 383)
-E
Highly flexible conductor for use in arc welding cables to
HD22 Part 6 (flexibility different from Class 6 of HD 383)
-F
Flexible conductor of a flexible cable or cord (flexibility
according to Class 5 of HD 383)
-H
Highly flexible conductor of a flexible cable or cord
(flexibility according to Class 6 of HD 383)
-K
Flexible conductor of a cable for fixed installations
(unless otherwise specified, flexibility according to Class
5 of HD 383)
-R Rigid, round conductor, stranded
-U Rigid round conductor, solid
-Y Tinsel conductor
Number and size of conductors
(number) Number, n of cores
X
Times, where a
green/yellow core is not
included
G
Times, when a
green/yellow core is
included
(number)
Nominal cross-section, s,
of conductor in mm²
Y
For a tinsel conductor
where the cross-section is
not specified
H 07 V V - F 3 G 2,5
Voltages Uo/U
01
100/100V;
(<300/300V)
03 300/300V
05 300/500V
07 450/750V
1 600/1000V
Metal Coatings (shield and armor)
C Concentric conductor of copper
C4 Copper braid shield on all the souls
C5 Copper braid shield over the souls
C7
Screen strip, wire or flat copper on all
the souls
Z2 Round steel wire armouring
Z3 Reinforcement steel flat
Z4 Steel tape armor
Z5 Braid armor of steel wires
.. ..
Insulation Sheath
B Ethylene-propylene rubber
N Polychloroprene (or equivalent material)
N4
Chlorosulfonated polyethylene or
chlorinated polyethylene
N8 Water resistant polychloroprene
Q Polyurethane
R Synthetic rubber
V Ordinary PVC
V2 PVC for temperature of 90 ° C
V5 PVC oil resistant
Z
Crosslinked polyolefins having low
emission of smoke, toxic gases and
corrosive
Z1
Thermoplastic polyolefins having low
emission of smoke, toxic gases and
corrosive

12. LV Cable & Wire designation
Cable Standard
H Harmonised Cable
A National Type of cable
N National unauthorized
S Special compliant
J Conforms IEC
Insulation Material
B Ethylene-propylene rubber
G Ethylene-vinyl-acetate
M Mineral
N Polychloroprene (or equivalent material)
N2 Polychloroprene for welding cables
R
Ordinary ethylene propylene rubber or
equivalent synthetic elastomer for a
continuous operating temperature of 60ºC
V Ordinary PVC
V2 PVC for temperature of 90 ° C
Z
Crosslinked polyolefins having low emission
of smoke, toxic gases and corrosive
Z1
Thermoplastic polyolefins having low
emission of smoke, toxic gases and
corrosive
Special construction
No SymbolCircular construction of cable
H
Flat construction of “divisible”
cables and cores, either sheathed
or non-sheathed
H2
Flat construction of “non-divisible”
cables and cores
H6
Flat cable having three or more
cores, according to DH 359 or EN
50214
H7
Cable having a double layer
insulation applied by extrusion
H8 Extensible lead
Conductor material
No Symbol Copper
-A Aluminium
Conductor shape
-D
Flexible conductor for use in arc welding cables to HD
22Part 6 (flexibilty different from Class 5 of HD 383)
-E
Highly flexible conductor for use in arc welding cables to
HD22 Part 6 (flexibility different from Class 6 of HD 383)
-F
Flexible conductor of a flexible cable or cord (flexibility
according to Class 5 of HD 383)
-H
Highly flexible conductor of a flexible cable or cord
(flexibility according to Class 6 of HD 383)
-K
Flexible conductor of a cable for fixed installations
(unless otherwise specified, flexibility according to Class
5 of HD 383)
-R Rigid, round conductor, stranded
-U Rigid round conductor, solid
-Y Tinsel conductor
Number and size of conductors
(number) Number, n of cores
X
Times, where a
green/yellow core is not
included
G
Times, when a
green/yellow core is
included
(number)
Nominal cross-section, s,
of conductor in mm²
Y
For a tinsel conductor
where the cross-section is
not specified
H 05 V V - F 1 X 10
Voltages Uo/U
01
100/100V;
(<300/300V)
03 300/300V
05 300/500V
07 450/750V
1 600/1000V
Metal Coatings (shield and armor)
C Concentric conductor of copper
C4 Copper braid shield on all the souls
C5 Copper braid shield over the souls
C7
Screen strip, wire or flat copper on all
the souls
Z2 Round steel wire armouring
Z3 Reinforcement steel flat
Z4 Steel tape armor
Z5 Braid armor of steel wires
.. ..
Insulation Sheath
B Ethylene-propylene rubber
N Polychloroprene (or equivalent material)
N4
Chlorosulfonated polyethylene or
chlorinated polyethylene
N8 Water resistant polychloroprene
Q Polyurethane
R Synthetic rubber
V Ordinary PVC
V2 PVC for temperature of 90 ° C
V5 PVC oil resistant
Z
Crosslinked polyolefins having low
emission of smoke, toxic gases and
corrosive
Z1
Thermoplastic polyolefins having low
emission of smoke, toxic gases and
corrosive

13. LV Cable & Wire designation
Cable Standard
H Harmonised Cable
A National Type of cable
N National unauthorized
S Special compliant
J Conforms IEC
Insulation Material
B Ethylene-propylene rubber
G Ethylene-vinyl-acetate
M Mineral
N Polychloroprene (or equivalent material)
N2 Polychloroprene for welding cables
R
Ordinary ethylene propylene rubber or
equivalent synthetic elastomer for a
continuous operating temperature of 60ºC
V Ordinary PVC
V2 PVC for temperature of 90 ° C
Z
Crosslinked polyolefins having low emission
of smoke, toxic gases and corrosive
Z1
Thermoplastic polyolefins having low
emission of smoke, toxic gases and
corrosive
Special construction
No SymbolCircular construction of cable
H
Flat construction of “divisible”
cables and cores, either sheathed
or non-sheathed
H2
Flat construction of “non-divisible”
cables and cores
H6
Flat cable having three or more
cores, according to DH 359 or EN
50214
H7
Cable having a double layer
insulation applied by extrusion
H8 Extensible lead
Conductor material
No Symbol Copper
-A Aluminium
Conductor shape
-D
Flexible conductor for use in arc welding cables to HD
22Part 6 (flexibilty different from Class 5 of HD 383)
-E
Highly flexible conductor for use in arc welding cables to
HD22 Part 6 (flexibility different from Class 6 of HD 383)
-F
Flexible conductor of a flexible cable or cord (flexibility
according to Class 5 of HD 383)
-H
Highly flexible conductor of a flexible cable or cord
(flexibility according to Class 6 of HD 383)
-K
Flexible conductor of a cable for fixed installations
(unless otherwise specified, flexibility according to Class
5 of HD 383)
-R Rigid, round conductor, stranded
-U Rigid round conductor, solid
-Y Tinsel conductor
Number and size of conductors
(number) Number, n of cores
X
Times, where a
green/yellow core is not
included
G
Times, when a
green/yellow core is
included
(number)
Nominal cross-section, s,
of conductor in mm²
Y
For a tinsel conductor
where the cross-section is
not specified
H 07 R N - F 3 X 6
Voltages Uo/U
01
100/100V;
(<300/300V)
03 300/300V
05 300/500V
07 450/750V
1 600/1000V
Metal Coatings (shield and armor)
C Concentric conductor of copper
C4 Copper braid shield on all the souls
C5 Copper braid shield over the souls
C7
Screen strip, wire or flat copper on all
the souls
Z2 Round steel wire armouring
Z3 Reinforcement steel flat
Z4 Steel tape armor
Z5 Braid armor of steel wires
.. ..
Insulation Sheath
B Ethylene-propylene rubber
N Polychloroprene (or equivalent material)
N4
Chlorosulfonated polyethylene or
chlorinated polyethylene
N8 Water resistant polychloroprene
Q Polyurethane
R Synthetic rubber
V Ordinary PVC
V2 PVC for temperature of 90 ° C
V5 PVC oil resistant
Z
Crosslinked polyolefins having low
emission of smoke, toxic gases and
corrosive
Z1
Thermoplastic polyolefins having low
emission of smoke, toxic gases and
corrosive

14. Cable selection
Cable construction and materials are determined by:
• Working voltage
(thickness of the insulation)
• Environmental conditions*
(composition of the outer cable jacket)
• Mechanical stresses
(conductor flexibility, form and composition of the outer cable jacket)
* temperature, fire, water, chemical or sunlight exposure

15. Conductor/s
for carring current
CONDUCTOR

16. Number of conductors
1- Single core
1X
2- Multi-core
2X, 3X, 4X …
3G, 4G, 5G …

17. Conductor materials
The electrical and mechanical properties dependent on its alloy
Physical Property Cu Al
In electrical equipment
pure
not used pure
(too soft)
Electrical conductivity 100% 56%
Cross section for same conductivity 100% 160%
Tensile strength (MPa) 100% 45%
Tensile strength for same conductivity 100% 73%
Weight for same conductivity (kg) 100% 48%
Coefficient of expansion (°C^-1 x 10^-6) 16.06 23

18. Shape of conductor
ShapedOvalCircular

19. Type of conductor
•Solid
• manufactured from a single solid metal piece
• inexpensive
• excellent environmental and corrosive resistance
• reduced surface area
Flat strap solid piece of metal drawn into a flat conductor
•Stranded
• several small wound into a single larger conductor
• more flexible than solid wire
Flat braid flat conductor comprising several small
conductors wound together
Tinsel number of a tinsel threads (textile core with a
helical wire strip) stranded together

20. Type of stranding
Bunched - Strands are gathered together
• least expensive type of stranding as it involves the least time and labor.
• great flexibility
Concentric - Strands are arranged in a circular pattern.
• Each layer alternates direction and has an increasing lay length
• Good mechanical strength and crush resistance
Unilay - Strands are arranged in a circular pattern
• all layers are twisted in the same direction and share the same lay length.
• light weight and allows a small diameter
Rope Lay - Strands are arranged into cabled groups.
• Each group usually consists of 7, 13, 19, or 27 strands as those can be
gathered into a circular configuration easily
• Rope lay is the most flexible type of stranding

21. Insulation
separates conductors, electrically and physically, within a cable
INSULATION

22. Insulating materials
• Cross-Linked Polyethylene – XLPE
• Ethylene-Propylene Rubber – EPR
• Polyvinyl Chloride – PVC
• Tree-Retardant Cross-Linked Polyethylene - TR-XLPE
POLYMERS
NATURAL SYNTETIC
ELASTOMERS
THERMOSETTINGS
(DUROMERS)
THERMOPLASTICS
(PLASTOMERS)

23. Physical requirements
• Elongation
how far the material will stretch before breaking(%)
• Tensile strength
how much force it takes to break the insulation or jacket
• Dielectric strength
withstand breakdown voltage
• Temperature rating
range of temperatures – no degradation
• Flexibility
ability to bend
• Flammability
ability to burn, emission in case of burning
• Weatherability
ability to withstand abrasion, chemicals, water and weather
• Specific gravity
the weight of material compared to water

24. Insulation types
vs Qualitative performance characteristics
Insulation type Specific
gravity
Dielectric
constant
Dissipation
factor
Volume
resistivity
Dielectric
strenght
Flammability Temperature
range
PVC (Standard) 1.25–1.38 4–6 0.06–0.10 10^11 800–900 Good −20 to 80
PVC (Premium) 1.38 3–5 0.080–0.085 10^12 800–900 Good −55 to 105
Polyethylene 0.92 2.27 0.0002 >10^16 1200 Poor −60 to 80
Polypropylene 0.90 2.24 0.0003 >10^16 850 Poor −60 to 80
Cellular
Polyethylene
0.5 1.5 0.0002 — 500 Poor −60 to 80
Flame Retardant
Polyethylene
1.30 2.5 0.0015 >10^16 1000 Fair −60 to 80
FEP (or TFE) 2.15 2.1 0.0007 >10^18 1200 Excellent −70 to 200 (or
260)
Cellular FEP 1.2 1.4 0.0007 — 500 Good −70 to 200

25. Thermoplastics
A classification for a solid insulation material that can be
softened and made to flow by heating, extruded onto
wire and quenched in cool water to make solid again.

26. PVC
The plastic most commonly used for conductor insulation
Thermoplastic
Flexibility

Fire (not) propagation

Emission in case of fire

Temperature 70-160°C
Water


27. PE
In electrical specification point of view it is lower than PVC
Thermoplastic
Flexibility

Fire (not) propagation

Emission in case of fire

Temperature 70-160°C
Water


28. Thermosets
A classification for an insulation that is extruded onto wire and
then, when subject to heat and pressure, undergoes a chemical
change known as vulcanization, cross-linking or curing.

29. XLPE
Cross linked polyethylene is produced from polyethylene
under high pressure with organic peroxides as additives
Thermosets
Flexibility

Fire (not) propagation

Emission in case of fire

Temperature 90-250°C
Water


30. Elastomers
Polymer with viscoelasticity (having both viscosity and elasticity)
and very weak inter-molecular forces
Each of the monomers which link to form the polymer is usually
made of carbon, hydrogen, oxygen and/or silicon

31. EPR
Ethylene propylene rubber is considered a valuable
elastomer due to its useful chemical and physical properties
Syntethic Elastomers
Flexibility

Fire (not) propagation

Emission in case of fire

Temperature 90-250°C
Water


32. SiR
The macromolecules in this case consist of silicon-oxygen chains
Syntethic Elastomers
Flexibility

Fire (not) propagation

Emission in case of fire

Temperature 150-350 °C
Water


33. EVA
Copolymer used either as a thermoplastic or as an elastomer
Syntethic Elastomers
Flexibility

Fire (not) propagation

Emission in case of fire

Temperature 90-250°C
Water


34. Magnesium Oxide Insulation
White hygroscopic solid mineral It has an empirical formula of MgOand
consists of a lattice of Mg2+ ions and O2− ions held together by ionic
bonding
Flexibility

Fire (not) propagation

Emission in case of fire

Temperature 250 – 2000 (1083) °C
Water


35. Semi-conducting Screens
• consist of carbon-loaded polymer compound cross-linked with the insulation
• upper limit to the resistivity of the screens by standards:
• conductor screen 1000 m
• insulation screen  500 m
INSULATION
SCREEN
CONDUCTOR
SCREEN

36. mechanical, weather, chemical and electrical protection
Sheat
SHEATH

37. Screen - Armour
• Armour - to protect cables against mechanical damage during installation and
service - to Provide a path for fault and leakage currents
• Screen - keep electromagnetic radiation in
• types
• round or flat wires of steel or galvanised steel, copper or tinned copper,
aluminium or aluminium alloy
• Copper tape
• tapes of steel or galvanised steel, aluminium or aluminium alloy
armour of non-magnetic material has to be used on single-core cables
SCREEN
ARMOUR

38. Filler
Filler
To fill gaps in a cable for a more attractive appearance
To create and maintain a sequence or lay-up of components
To add strength to a cable

39. Ref Type
Main
Connection
Distribution
Fire control
and
Emergency
Data center HVAC
A N07V-K, H05V-K, H07V-K, H07V-R
B
FG7(O)R, RV,RV-K, U 1000 R2V,
U 1000 AR2V, (N)HXHX, (N)HXH,
NA2X2Y, NA2XY, NAY2Y, NAYY
C FM9, H07Z1-K, H07Z1-R
D
FG7OM1, H07Z1-K, FR-N1X1G1,
RZ1-K, H07ZZ-F
E
FTG10OM1, RZ1-K MICA, SZ1-K,
RZ1 FA 3Z1-K MICA
F
FG7OH2R, RZ1 C3Z1-K MICA,
RZ1 C3Z1-K, RZ1 OZ1-K, GKN, AXQJ
G
FG7ORAR, U 1000 RVFV, RZ1 FA
3Z1-K MICA, RVhMVh-K, RVFV
H
H07RN-F, H07ZZ-F,
H05VV-F
LV Typical cables
ONLY > 0,6/1 kV

40. PV Cables
Designation FG21M21 (CEI 20-91)
Conductor tinned copper wires
Insulation crosslinked elastomer halogen free - G21 (HEPR)
Sheath crosslinked elastomer halogen free - type M21
T ambient -40 / +90 °C
T max I> +120 °C
T max I>> +250 °C
Um 1,8 kV c.c. Also to ground
Life 25 years

41. Electrical vehicle felxible cable
41
Standard CEI 20-106
Electrical cables with cross-
linked insulation flame retardant ,
with rated voltage not exceeding
450 / 750V for the electric
vehicle charging

42. Thank you
| Presentation title and date
For more information please contact
Angelo Baggini
Università di Bergamo
Dipartimento di Ingegneria
Viale Marconi 5,
24044 Dalmine (BG) Italy
email: angelo.baggini@unibg.it
ECD Engineering Consulting and Design
Via Maffi 21 27100 PAVIA Italy