Deutsche Bahn supplies its electric traction units from a single-phase AC overhead line grid with a rated voltage of 15 kV and a rated frequency of 16.7 Hz. The 15 kV overhead lines are usually supplied through feeder cables and line feeders from the 15 kV bus bars in the traction current switchgear at the substations, sectioning points, paralleling points, and in transformers and rectifiers.
Substations on the central grid are supplied from the DB Energie 110 kV traction current transmission grid. The 110 kV potential of the traction current transmission grid is stepped down to the 15 kV potential of the overhead line at the substations and fed to the sections to be supplied through branches of the overhead line.
A substation on the central grid consists principally of the following:
- 110 kV outdoor switchgear
- 15 kV indoor switchgear
- Substation protection and management systems
- Substation supply system
Paralleling points (15 kV switchgear with only one circuit breaker for supplying the route by cross connection) connect the supply areas of adjacent switchgear with particularly long intervals between switchgear, with the objective of higher resilience of the lines and improved protective selectivity.
In future, the Roth substation will be used only to supply the new line with traction current. For this reason, it is being configured as a traction current block substation with 2 x 15 MVA transformers. It draws its energy from the 110 kV traction current grid through two power circuits of traction current transmission line 338 branch to Roth, which is itself supplied from traction current transmission line 420 Ebensfeld - Steibach.
The Wolfsberg substation will only be used to supply the new line with traction current. It is being built as a block substation to feed traction current to three sections of the new lined. It will be equipped with two 15 MVA transformers for this purpose.
The substation will feed traction current to three sections of the new line. It will be equipped with two 15 MVA transformers for this purpose.
Sectioning points (15 kV switchgear with two or more circuit breakers for line feed by cross connection) connect the overhead line on several sections for the purposes of feed, selective protection and potential equalisation, and supply current at 15 kV to sections of overhead line fed from one end. The purpose of using the switchgear described here is to reduce the life cycle costs demonstrably compared to the switchgear design currently in use by DB Energie.
Dörfles-Esbach sectioning point
The sectioning point forms an electrical connection between the existing Coburg - Sonneberg section and the new line, thus completing the northern loop around Coburg.
Niederfüllbach sectioning point
The sectioning point forms an electrical connection between the existing Lichtenfels - Coburg section and the new line, thus completing the southern loop around Coburg.