Guidance note
NR/GN/TEL/31106
Overview Of Electromagnetic Coupling Between Traction Systems And Telecommunications Cables
Issue 1, 6 June 2009 · Copper design & immunisation
Clause map — what each clause deals with
| 1 | Purpose | Overview of how traction current induces voltages on lineside telecoms cables |
| 2 | Scope | What the guidance covers |
| 3 | Definitions | Definitions — accessible voltage, longitudinal, transverse |
| 4.1 | Risks to telecommunications systems due to electric traction | The risks electric traction poses to telecoms |
| 4.2 | Electric Traction Systems | The UK traction systems in use |
| 5 | AC Traction - 25 kV Classic System | The 25 kV classic AC system explained |
| 5.1 | The power supply and distribution system1 | AC power supply and distribution — feeder stations |
| 5.1.1 | OHLE Dimensions | Typical OHLE dimensions |
| 5.1.2 | Normal feeding | Normal feeding |
| 5.1.3 | First emergency feeding | First emergency feeding |
| 5.1.4 | Second emergency feeding | Second emergency feeding |
| 6 | Magnetic Induction | Magnetic induction — the principle |
| 6.3 | Rail current | Rail current |
| 6.4 | Frequency spectrum of train current | Frequency spectrum of train current — harmonics |
| 6.5 | Magnetic field | Magnetic field strength |
| 6.6 | Induced voltage on lineside conductors | How voltage is induced on lineside conductors |
| 6.6.1 | Longitudinal voltage and common mode voltage | Longitudinal and common-mode voltage |
| 6.7 | Transverse voltage | Transverse voltage |
| 6.7.1 | Psophometric transverse voltage | Psophometric (noise) voltage |
| 6.8 | Line transients | Line transients |
| 6.9 | Electrification faults | Electrification faults and their effect |
| 6.10 | System resonance | System resonance |
| 7 | AC electrification systems | The four AC electrification variants |
| 7.1.1 | Rail return | Rail-return systems |
| 7.1.2 | Return-conductor-only systems | Return-conductor-only systems |
| 7.1.3 | Return conductor and booster transformers | Booster transformer systems |
| 7.1.4 | Autotransformer system | Autotransformer systems |
| 7.2.1 | Control of hazardous potentials | Controlling hazardous potentials — the induced voltage limits on telecoms cables and how they are met (the test limits themselves sit in NR/L2/TEL/31107) |
| 7.3 | Factors affecting induced voltages on telecoms cables | Factors affecting induced voltage |
| 7.4 | Immunisation of lineside cables | Immunisation — what it means |
| 7.4.1 | Physical separation | Physical separation from the track |
| 7.4.2 | Limiting cable length | Limiting cable length (sheath gaps, sectioning) |
| 7.5.1 | Mutual screening conductor | Mutual screening conductor |
| 7.5.2 | Return screening conductor | Return screening conductor (RSC) |
| 7.5.3 | Self-screened cable | Self-screened cable |
| 7.5.4 | Comparison of electrification systems and screening | Comparison of systems and screening effectiveness |
| 8 | DC Traction Electrification | DC traction overview |
| 8.1 | Third rail DC traction electrification | Third-rail DC |
| 8.2 | Fourth rail DC traction electrification | Fourth-rail DC (LU) |
| 8.3 | Overhead DC traction electrification | Overhead DC (trams/metro) |
| 8.4 | Undesirable effects in DC electrified areas | Problems DC causes for telecoms |
| 8.5 | Control of undesirable effects in DC electrified areas | Controlling DC effects — touch potentials |
| 8.6 | DC leakage current | DC leakage current and corrosion |
| 9 | High voltage AC cables | Induction from HV AC power lines |
| 10 | VL and VT tests on telecoms cables | VL and VT commissioning tests |
| 10.1 | Longitudinal voltage (VL) | Longitudinal voltage measurement |
| 10.2 | Transverse voltage | Transverse voltage measurement |