FTN design & development specification (D&D)

SP FTN (D&D) 009

Network Design Manual for Copper Cable

Issue 4.5, Feb 2009 · FTN D&D specs & typical drawings

The FTN copper cable design manual: how a designer sizes, routes and immunises lineside copper sections between nodes, where cabinets and BOPs go, pair allocation and DSL limits in AC, DC and non-electrified areas.

Clause map — what each clause deals with

1	Introduction	Purpose of the manual, who does detailed copper design, and the rule that conductors run continuous point to point with no spurs.
2	Abbreviations	Acronym list (BOP, BT, DBS, DRR, SRR, FTE, RC, TSC, VL, VT etc.).
3	Glossary	Definitions of copper section, half-section, stub cable, tail cable, Db Colo cable, touch potential, return rail/conductor and node types.
4	Scope	Mandatory status of the manual; applies to non-electrified, DC and AC areas; copper only where DSL or lineside services need it.
5	Safety	Designer's duty not to import new safety hazards.
6	Connectivity and Interfaces	Interfaces with other rail projects and PTOs, expected to be at optical rather than copper level.
7	FTN Architecture	Overview of the SDH ring network and the role of copper for lineside services and DSL on non-fibred lines.
7.1	The Copper Cable Network	When stub cables are allowed (branch lines, rail return, tunnels, islands, node moves), why conductor size matters, and what a copper island is.
8	System Planning	How the manual's sections apply depending on fibre presence and traction type.
8.1	Lines With Optical Fibre Cable	Concept sketch for a fibred section: circuits on fibre, copper only for lineside services.
8.2	Lines Without Optical Fibre Cable	Concept sketch for a non-fibred section with HDSL carrying 2 Mbit/s over the copper.
8.3	Copper Islands With No Mid-Section Services	Island arrangement where no through copper is needed because nothing sits mid-section.
8.4	Copper Islands With Mid-Section Services Fed by TEH	Island arrangement using a mid-section TEH to feed services; who to tell about TEH requirements.
9	Traction Electrification Systems and Their Effects on Copper Cables	Background on how DC and AC traction supplies create interference and shock risk in telecoms cables.
9.1	DC Traction Electrification	How DC traction is fed from substations via the E&P route and why it differs from AC.
9.1.1	Third Rail DC Traction Electrification	How third rail supply and return work and how to recognise it on site.
9.1.2	Fourth Rail DC Traction Electrification	LUL fourth rail system and how to recognise it.
9.1.3	Overhead DC Traction Electrification	Tram overhead DC systems; seek technical clarification when fourth rail or overhead DC is met.
9.1.4	Undesirable Effects in DC Electrified Areas	The two effects (touch potential, noise) and four sources of them in DC areas.
9.1.5	Control of Undesirable Effects in DC Electrified Areas	Control measures: earth-free armour, gapped sheaths, isolated moisture barriers, separation, limiting HV parallel runs, screening conductors.
9.2	AC Traction Electrification	How 25 kV OHLE feeds trains via pantograph and returns through rails (figure).
9.2.1	The Power Supply and Distribution System	Feeder stations, neutral sections, boundary and mid-section TSCs, feeder section lengths and emergency feeding.
9.2.2	Rail Return AC Traction Electrification Systems	Single and double rail return, why SRR is common, and why rail return induces most into cables.
9.2.3	Return Conductor and Booster Transformers	Suppression at source using RC and BTs, their spacing, return bonds, and the effect of a BT outage.
9.2.4	Return-Conductor-Only Systems	RC without BTs is treated as rail return for design; note on where to see electrification types side by side.
9.2.5	Undesirable Effects in AC Electrified Areas	The two effects and three sources in AC areas, introducing longitudinal (VL) and transverse (VT) induced voltage.
9.2.6	Control of Undesirable Effects in AC Electrified Areas	Control measures plus the long list of parameters affecting immunisation and which ones the FTN can influence; continuous cable length is key.
9.3	Immunisation	Electromagnetic induction explained with figures showing induction from return rail and the benefit of a return conductor.
9.3.1	Physical Separation	Separation distance as an immunisation method and why it is often impractical on existing routes.
9.3.2	Limiting Length	Limiting continuous copper length via node spacing and half-sections; the maximum continuous length in RC/BT areas and who to notify.
9.3.3	Self Screened Telecoms Cables	Why older self-screened cables are not used on the FTN.
9.3.4	Separate Screening Conductors	What a screening conductor is, how it cancels induced current (figures), survey of existing ones and repair/replacement duties.
9.3.5	Electrical Testing to Confirm Suitable Immunisation	Commissioning and periodic immunisation tests and which specs govern them.
10	Survey Requirements	Pointer only: survey content moved to the survey specification.
11	Components of the Copper Network	Overview of cables, joints, cabinets and termination practice used on the copper network.
11.1	Copper Cables	Cable types, pair counts and conductor sizes available, and reuse of existing cables.
11.1.1	Main Cables	Free-issued main cables, drum lengths, designer's duty to size pairs using survey, GOU, records and CAMS; handling cables in service.
11.1.1.1	Cable Sheath	Which sheath type is used generally and which in sub-surface stations and tunnels.
11.1.1.2	Test Specification	Pointer to the copper cable test spec.
11.1.1.3	DSL Line Attenuation Test	Sets insertion loss and NEXT limits for DSL pairs and the regenerator spacing limits by conductor size.
11.1.2	Jumper Wire	Jumper wire standard, colour code for general versus special circuits, A-leg designation, and replacing through jumpers for DSL.
11.2	Joint Closures	When copper joints are permitted, the crimp connector and heatshrink closure used, and joint bay requirements.
11.3	Distribution Cabinets	Siting cabinets and BOPs from survey, and a table of when a fast transient earth or bonding is needed based on nearby conducting bodies.
11.4	Termination Practice	Terminations are free-issued and done to the jointing and terminating spec.
11.4.1	Terminations in Environments with No Climate Control	Which termination module was selected for unconditioned cabinets after environmental testing.
11.4.2	Terminations in Environments with Climate Control	Which 10-pair IDC module is used in climate-controlled housings.
12	Accommodation	Where copper terminates at each type of site and the rules that apply there.
12.1	Core Nodes	MDF termination in core nodes, one cable per route, no cable-to-cable jumpers, sheath gapping.
12.1.1	Earthing	Pointer to the earthing details in the jointing/terminating spec.
12.2	Access Nodes	Terminations in ATEHs and REBs, no cable-to-cable jumpers, no tail distribution from ATEHs, capping and coiling cables when the node is late.
12.3	Distribution Cabinets and BOPs	Cabinet and BOP variants, pre-tailed BOPs, siting to keep tails short, through jumpering, and UP/DOWN cable to vertical A/B including mileage changes.
12.4	Repeater Housings	Housings for DSL repeaters attached to cabinets and their nominal distance from a node.
12.5	Tunnel Termination Boxes	Wall-mounted boxes in long tunnels for terminating 10-pair tails and feeding tunnel services.
13	Detailed Copper Design	The core design rules a designer applies per copper section.
13.1	General	One detailed design per copper section, based on survey data; copper only where needed.
13.2	Design Parameters to Control Undesirable Effects in DC Electrified Areas	DC rules: route side relative to traction cables, crossing clearance, armour gapping, moisture barrier continuity, earth rod exclusion zones, insulated connectors.
13.3	Design Parameters to Control Undesirable Effects in AC Electrified Areas Using Rail Return	Rail return rules: short armour lengths, isolated moisture barriers, separation, half-sections not bridged (figure), cabinet siting, earth rod zones.
13.4	Design Parameters to Control Undesirable Effects in AC Electrified Areas with Return Conductor and Booster Transformers	RC/BT rules: as rail return plus a requirement for an earthed screening conductor in the route.
13.4.7	Hot Wire Working	Why all AC-area telecoms plant is treated as live, and the working practices the design must call for.
13.5	Resilience	Successive and adjacent feeding of SPTs so some survive a cable cut; reference drawing and waiver route.
13.6	Choice of Cable Type	Pair count and conductor diameter stay constant through a section; principles for choosing them.
13.6.1	Cable Pair Count	Table of pairs needed per lineside circuit type and table mapping total pairs to cable size, with a worked example.
13.6.2	Conductor Diameter	Section length threshold for choosing 0.63 or 0.9 mm, with exceptions for mid-section signal boxes and long DSL regenerator sections.
13.7	Design Output	Detailed design document per section to the engineering spec.
13.8	Copper Islands	Conditions that must all be met before a copper island is considered, then the commercial comparison and pair sizing for islands.
14	Sections Required to Support DSL Traffic	What a DSL system and regenerator section are and the maximum regenerator sections per cable section.
15	Allocation of Cable Pairs	Standard pair allocations on new cables.
15.1	General	Why standard allocations exist and that designers must know them.
15.2	Pairs for DSL Traffic	Table of which pair numbers each DSL system takes in 50, 30 and 10 pair cables.
15.3	Immunisation Test Pairs	Last two pairs reserved as VT and VL test pairs in AC areas, with the far-end termination arrangement and near-end location.
16	Migration Phase	Circuit transfer is a later phase; design must facilitate it.
17	Directly Buried Sub-duct (DBS)	Pointer to where DBS use is set out.
18	Records	Test results and as-built records to be specified in the design.
19	Standards	List of referenced standards and FTN specs.
App A	Drawings	List of typical copper section drawings for fibred/non-fibred AC/DC lines, SPT feeding and cabinet termination.

Clause map — what each clause deals with

Standards this one points to