June 9, 2015
Sweden’s SydVästlänken will contain the world’s longest underground cable for high-voltage power transmission.
When you are above groundwater level, it’s just rainwater that you have to take care of,” says Johansson. “But below groundwater level you need more pumps. Sometimes you need a lot of pumps every 30–40 meters, while in other places it can be drier and you don’t need any pumps at all. The soil conditions can vary every second meter.
When it rains, overflow from the E4 highway runs into the trenches. “Then we’re dealing with enormous quantities of water,” says Johansson.
Project Engineer Adam Ericsson says the team has become better at placing the pumps well for optimum effectiveness.
Project Engineer Adam Ericsson says that the project team has gotten better at managing the water. “We have learned and taken the time to really place the pumps well for optimum effectiveness, and this has resulted in operational improvements.”
The base of each cable trench must be kept completely dry to protect the 14 different transmission cables that will eventually rest here. A special gravel backfill is meticulously laid, following exact specifications for the best compaction, drainage and cohesiveness. Only then can the transmission cables, tucked into sturdy tubes, be laid in the trenches, which are then refilled.
During the period of 4–8 weeks when the trenches are open, some 60 Atlas Copco generators power about 250 pumps. “We are putting extremely high demands on the pumps and generators, which are running around the clock,” says Ericsson. “It’s a tough environment outside, and the pumps and generators are running much more intensively than normal. The equipment has been under high pressure daily, but it is keeping up with the demands.”