The detailed planning demonstrated that as part of a further project – the new construction of a 220 kV GIS plant in Gösgen – a new pipe system needed to be created for the 220 kV cable outlets. This enabled the cable connection to be construction directly from the Gösgen substation to the substation structures of the unused 220 kV line section from Gösgen to Flumenthal rather than running it via the existing piping through the residential neighbourhood as originally planned. This reduced the length of the lines by around 400 metres. Since the new cabling is running exclusively through property belonging to the system operator, it was authorised by the Federal Inspectorate for Heavy Current Installations (ESTI) in a simplified process.
Execution of construction and assembly
After the rough scheduling, the tender documents of the civil and underground engineering and cable works were established. The wiring system and component parts were supplied by Nexans Suisse SA and the execution of the civil engineering works were delegated to Kummler+Matter EVT AG. The construction of the new conduit blocks in Gösgen was extremely difficult. The excavations down to a depth of almost five metres were additionally complicated by water seepage (springs, mill stream), pressure of the mountain and solid rock.
Checking, commissioning, completion
The cable works were completed on time – including cable checks and impedance measurements for the new cable sections. The new 50 kV line was put into operation on 19 August 2011 after the phase control and voltage check and handed over to the grid control centre in Olten (ZNL). Completion of the documentation and the approval of the final report by AVAG marked the conclusion of the project.