Lavspenning/Kabler/Open specification for metallic track-side cable

Open specification for metallic track-side cable

1 Scope

1.1 Purpose

The purpose of the technical specification is to provide guidance for the production, test procedures and delivery of products according to stated requirements. The technical specification contains technical and functional requirements to be fulfilled.

The cables shall provide capability to transfer power and/or data signals to external safety facilities. The cables shall be free of halogens. The cables shall withstand relevant loads that may be present in normal operation of safety facilities for railways.

The specification is an open specification as the actual number and type of cable elements is left undefined for the actual design of a cable.

The electrical parameters, such as characteristic impedance, capacity, phase velocity, crosstalk parameters etc. are left for final design of the cable.

2 Electrical parameters and requirements

To be defined.

3 Mechanical structure and requirements

a) The cable shall be free of halogens (less than 0,5 % halogens).

3.1 Cable core filling compound

a) All residual space in cable elements (i.e. single insulated lead, twisted pair, star quad or Dieselhorst-Martin quad) shall be filled with Vaseline.

3.2 Cable elements

a) The cable elements shall be one of either single insulated lead, twisted pair, star quad or Dieselhorst-Martin quad, see Figur 1.

b) If a cable element is provided with both an optional screen and an optional reduction lead, the screen and the reduction lead shall be in electrical contact with each other.

Figur 1: Cable elements

3.2.1 Single lead

a) Construction of a single lead:

• the single lead shall be made of annealed copper
• the single lead may be solid or stranded
• the single lead may be tinned

The cross section area and the construction of the single lead is to be defined.

3.2.1.1 Insulation

a) The single lead shall be insulated as depicted:

• the insulation material shall be a polymer, likely to be polyethylene or polypropylene.
• the insulation of polyethylene or polypropylene may be foamed (0 % to 20 %) or shall otherwise be solid.

The outer diameter of the insulated lead is to be defined.

3.2.2 Single insulated lead

a) A cable with single insulated leads shall be arranged in a layer structure.

b) The insulation of the single lead shall have a solid colour as depicted in Tabell 5.

3.2.3 Twisted pair

a) The twisted pair consists of:

• two insulated leads
• an optional screen of either:
  • metal foil (i.e. aluminium, copper, tinned copper, etc.) or
  • metal braid (i.e. aluminium, copper, tinned copper, etc.)

b) The two insulated leads shall be twisted with a defined lay length.

c) If more pairs are contained in the same cable group or the same cable core, the twisted pairs should have different lay lengths.

d) The insulation of the leads in a twisted pair shall have a solid colour as depicted in Tabell 2 for a group or Tabell 3 for a layer structure.

An optional reduction lead may be added to the optional screen. The design of the optional screen and the optional reduction lead is to be defined.

3.2.4 Star quad

a) The star quad consists of:

• four insulated leads
• an optional screen of either:
  • metal foil (i.e. aluminium, copper, tinned copper, etc.) or
  • metal braid (i.e. aluminium, copper, tinned copper, etc.)

b) The four insulated leads shall be twisted with a defined lay length.

c) If more star quads are contained in the same cable group or the same cable core, the twisted star quads should have different lay lengths.

d) The insulation of the leads in a star quad shall have a solid colour as depicted in Tabell 2 for a group or Tabell 3 for a layer structure.

An optional reduction lead may be added to the optional screen. The design of the optional screen and the optional reduction lead is to be defined.

3.2.5 Dieselhorst-Martin quad

a) The Dieselhorst-Martin quad consists of:

• two twisted pairs, each of them with or without an optional screen
• an optional screen of either:
  • metal foil (i.e. aluminium, copper, tinned copper, etc.)
  • metal braid (i.e. aluminium, copper, tinned copper, etc.)

b) The two twisted pairs in a Dieselhorst-Martin quad shall have different lay length and should preferable be revolved in different directions.

c) The two pairs shall be twisted together to form the Dieselhorst-Martin quad.

d) The insulation of the leads in a Dieselhorst-Martin quad in a shall have a solid colour as depicted in Tabell 2 for a group or Tabell 3 for a layer structure.

An optional reduction lead may be added to the optional screen of the Dieselhorst-Martin quad. The design of the optional screen(s) and the optional reduction lead are to be defined.

3.3 Number of cable elements in a cable

a) A cable should only contain one type of cable elements, either
* single insulated leads
* twisted pairs
* star quads or
* Dieselhorst-Martin quads.

The number of cable elements in a cable is to be defined.

3.4 Cable core structure

The cable core may be arranged in one or more group(s), see 3.4.1, or in layer(s), see 3.4.2.

a) The number of twisted pairs in a group shall be limited to 10.

b) The number of star quads or Dieselhorst-Martin quads in a group shall be limited to 5.

c) The number of cable elements in a layer structure will typical be:

• 1 (in the centre) + 6 (in layer 1) + 2*6 (in layer 2) + … + n*6 (in layer n) or
• 3 (in the centre) + (3 + 6) (in layer 1) + (3 + 2*6) (in layer 2) + … (3 + n*6) (in layer n)

d) All cable elements in a group (regardless of construction of the cable elements) should have individual lay lengths to minimize the crosstalk noise in the cable.

e) Similar principle for the lay lengths should be applied for the two consecutive neighbouring cable elements (i.e. twisted pair, star quad or Dieselhorst-Martin quad) in a layer.

f) Statistical methods should be applied to optimize all the lay lengths for optimum crosstalk performance of the worst performing pair combination.
Informative reference: Holte, N., A crosstalk model for cross-stranded cables, Sintef, Trondheim, 1982. (ELAB rapport STF44FB2204)

The structure is to be defined.

3.4.1 Cable element groups

a) The ten pairs or five quads of a group shall be contained in a regular or random structure.

b) The group shall be wrapped together with a plastic tape for identification, either with a permanent written number or by colour coding as depicted in Tabell 4.

3.4.2 Cable element layers

b) The cable elements shall be arranged in a layer structure.

b) Each layer should be wrapped by a thread, a plastic tape or similar to fix the structure.

3.5 Cable core wrapping

a) The cluster of all cable elements (groups or layers) shall have an outer wrapping consisting one of the following:

• a plastic tape
• a metallic foil with an optional reduction lead
• a metallic braid

The design of the wrapping is to be defined.

3.6 Core sheath

a) The core sheath shall be solid polyethylene or polypropylene. See Tabell 1 for more details.

b) A rip cord shall be included under the core sheath.

3.7 Armouring of cable

a) Two steel tapes shall be wrapped helically over the core sheath.

b) The two steel tapes shall have an overlap of minimum 20 %. See Tabell 1 for more details.

An optional reduction lead in electrical contact with one of the steel tapes may be included.

The design of the optional reduction lead is to be defined.

3.8 Outer cable sheath

a) The material in the outer cable sheath shall be either polyethylene / polypropylene or a flame retardant, low smoke, halogen-free polymer.

b)The outer cable sheath shall be UV protected. See Tabell 1 for more details.

c) A rip cord shall be included under the outer cable sheath.

Tabell 1: Protective details for the cable

	2 mm < core diameter < 10,0 mm	10 mm < core diameter < 20,0 mm	core diameter > 20 mm
Core sheath thickness (polyethylene or polypropylene)	1,5 mm	2,0 mm	2,5 mm
Number of steel tapes (the width of tapes depend on the core sheath diameter)	2	2	2
Steel tapes thickness	0,2 mm	0,2 mm	0,2 mm
Reduction lead	(optional)	(optional)	(optional)
Outer cable sheath thickness	2,0 mm	2,5 mm	2,8 mm
Outer cable sheath polymer	polyethylene / polypropylene or flame retardant, low smoke, zero halogens	flame retardant, low smoke, zero halogens	flame retardant, low smoke, zero halogens

3.9 Fire rating

a) Cables to be installed in tunnels and exposed to fire shall have a fire rating fulfilling the requirements of classification B2CA, s1a, a1, as per Commission Decision 2006/751/EC (TSI SRT (1303/2014), 4.2.2.4). Classifications are depicted in EN 13501-6.

(Cables installed in concrete cable ducts with concrete lids are supposed not to be exposed by fire.)

3.10 Outer sheath labelling

The outer sheath shall have a permanent marking for each meter.

• cable type
• production year (four digits)
• supplier
• fire rating

3.11 Cable type notation

The cable type notation for permanent marking on the outer sheath shall be composed as follow:

• “L-# x,y iEBo-cap r” for pair cables
• “S-# x,y iEBo” for cables with single insulated leads

• # shall be substituted by the equivalent number of twisted pair (for quad elements multiply by two), or the number of single insulated leads
• x,y shall be substituted by the lead diameter in mm (y may be one or more digits)
• i shall be substituted by
  • F for solid polyethylene/propylene with Vaseline
  • M for foamed polyethylene/propylene with Vaseline
• o shall be substituted by
  • E for solid polyethylene/propylene
  • I for polymer of flame retardant, low smoke, zero halogens
• cap shall be substituted by the mutual capacitance in nF/km (only digits, no decimals)
• r shall be substituted by
  • P for twisted pairs
  • D for star quads
  • DM for Dieselhorst-Martin quads

Examples:
L-10 0,9 FEBE-55 D,
L-14 1,2 MEBI-37 DM

3.12 Identification of twisted pairs and groups

Any repeated sequence of colour code is marked with bold text in the following tables.

Tabell 2: Colour codes of twisted pairs or quads in a group
(Star quads or Dieselhorst-Martin quads)

Twisted pair cable element
Pair	1	2	3	4	5	6	7	8	9	10
Lead “a”	blue	white	yellow	grey	orange	red	white	yellow	grey	orange
Lead “b”	red	red	red	red	red	black	black	black	black	black
Quad cable element
Pair	1	2	3	4	5	6	7	8	9	10
Lead “a”	blue		white		yellow		grey		orange
Lead “b”	red		red		red		red		red
Lead “c”		green		green		green		green		green
Lead “d”		black		black		black		black		black

Tabell 3: Colour codes of twisted pairs or quads in a layer structure
(Star quads or Dieselhorst-Martin quads)

Twisted pair cable element
Pair	Previous layer	1	--	2	--	3	--	5	--	6	--	...	n	--	(next layer)
Lead “a”	(previous	blue	--	white	--	yellow	–	grey	–	white	–	...	orange	--
Lead “b”	layer)	red	–	red	–	red	--	red		red	–	...	red	--
Quad cable element
Pair	Previous layer	1	2	3	4	5	6	7	8	9	…	n-1	n	(next layer)
Lead “a”	(previous	blue		white		yellow		grey		white		…	orange
Lead “b”	layer)	red		red		red		red		red		…	red
Lead “c”	(gren)		green		green		green		green		green	…		green
Lead “d”	(black)		black		black		black		black		black	…		black

Tabell 4: Plastic tape colour codes for group numbers in a cable

Group number	1	2	3	4	5	6	7	8	9	10
colour(s)	blue	white	yellow	grey	orange	blue/black	white/black	yellow/black	grey/black	orange/black

Tabell 5: Colour codes of single insulated leads in a layer structure

Lead	Previous layer	1	2	3	5	6	7	...	(next layer)
Colour	(previous layer)	red	black	white	light blue	grey	white	...	(next layer)