Transportable rectifier substations ensure continuous power supply for electric tram lines during network modifications
The Leipzig Public Transport Corporation (LVB) is carrying out extensive modification and replacement works to increase the rated voltage of its network from 600 V to 750 V direct current (DC). As part of the project, the rectifier substations are being upgraded and alterations made to both their structures and equipment. In order to maintain the supply of traction current to the tram lines during the modification works, ABB commissioned two transportable rectifier substations at the end of July. These mobile substations temporarily replace the existing substations and help to considerably shorten the timeframe required for the modifications.
Mobile power supply
Using transportable rectifier substations is not an everyday occurrence, and the LVB is intentionally breaking new ground here. For designing the mobile units, basic electrical, mechanical and transportation-related requirements were stipulated that had to be met in full. Detailed implementation was covered by the specification drawn up jointly by the vendor and the LVB, who wanted the transportable rectifier substations to have optimal functionality combined with minimal footprint.
Following a public tendering procedure, LVB opted for ABB’s solution. ABB has extensive expertise in building compact transportable rectifier substations for tram line applications. Close liaison between LVB and ABB as well as open and constructive collaboration during detailed planning was crucial and an important basis for successful realization of the project.
A completely equipped transportable rectifier substation essentially contains the following components: gas-insulated medium-voltage switchgear, rectifier transformer, diode rectifier, DC switchgear, station auxiliaries, instrumentation and control (I&C) and telecontrol systems, as well as an operator panel for visualization and local control from outside. The latter was one of LVB’s paramount operational requirements for sites that cannot be interconnected to the central control system. The solution chosen provides for user-friendly, space-saving and risk-free local operator control without entering the container.
Sophisticated technology in a confined space
Using transportable rectifier substations in built-up areas, with residential housing, makes it absolutely essential to comply not only with the relevant safety regulations, but also with soundproofing and emission guidelines. Compliance with these standards is a major consideration when designing the electrical equipment in the containers and finalizing the component configuration. For soundproofing, the fans have to be given particular attention: because they account for a sizable proportion of the noise emissions from a rectifier substation, they are demand-responsively controlled using frequency converters, and the air outlet vents are fitted with relatively large muffler hoods. The containers themselves are lined with sound-absorbent panels. The need to ensure optimum ventilation influences the configuration and construction of the doors, the space apportionment of the rectifier station, and also the locations of the individual systems and components inside the substation.
The biggest electromagnetic fields in a rectifier substation occur on the low-voltage side of the rectifier transformer. This means the cable routing had to be as short as possible in order to avoid electromagnetic fields between the rectifier transformer and the rectifier. This, too, influenced the layout of the container.
For selecting the individual components, the crucial factor was the space available under these defining conditions, plus their accessibility from the front for simple maintenance and repair work.
Fast completion, high quality
The two transportable rectifier substations were installed in their containers and tested at ABB’s factories, creating several advantages: the high degree of prefabrication provides more comprehensive testing options during the factory acceptance tests, with concomitant gains in terms of quality assurance, and significant time savings thanks to location-independent installation: on site, only a minor amount of structural work is needed, and weather-related delays cannot occur. All in all, transportable rectifier substations are a fast and cost-efficient option.
The containerized solution for mobile rectifier substations is designed not only for temporary use, but is also well suited as a stationary solution available at short notice - eg, at spurs for voltage support.