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EQOS Energie exchanges an overhead line mast in a reservoir

5. September 2019
  • Special project in the Black Forest region for the customer NetzeBW requires helicopter deployment

EQOS Energie was commissioned by energy provider NetzeBW to exchange a 110-kV overhead line mast situated in the middle of the Baden-Württemberg-based Schwarzabruck reservoir. For the exchange of the entire mast, both 110-kV circuits must be switched off. The challenge of this project is its special location: within the reservoir of the Schwarzatalsperre dam, 15 metres from the lakeshore. The base of the mast had been mounted in 2018, in parallel to the maintenance work at the dam. At that time, the entire lake was drained, which was the only way to facilitate the fitting work. Since then, the mast has only been accessible via a narrow footbridge.

Heavy loads require helicopter deployment

A helicopter is used for the assembly of the upper mast parts, since the typical approach of using a lorry-mounted crane is impossible due to the special circumstances. During the exchange, the EQOS Energie experts will first remove the conductors and the ground wire in order to “free” the old mast. “The new mast parts with a total weight of about 20 tonnes will be pre-assembled and laid out section by section at the helicopter landing site 500 metres away. The loads of up to five tonnes, which are hard to move, require an appropriate aircraft and a high level of expertise for the work to be performed. Therefore, EQOS Energie has subcontracted with a specialised company to fly the loads from and to the assembly site,” said Dieter Walber, head of the Luxembourg profit centre in the Overhead Line Construction business unit at EQOS Energie.

Pre-assembly to be performed on land

During last year’s work, the foundation of the dam was substantially reinforced. For this purpose, a total of 400 cubic metres of concrete were used, which had to be transported to the basin of the reservoir by about 40 concrete-mixing lorries. As part of this process, EQOS Energie installed the new base of the mast. o avoid any delays during flight deployment for the current mast exchange, the connecting elements on the old mast were also replaced with new ones in 2018. This way, it can be discounted that connections are impossible or difficult to undo while the helicopter hovers over the mast. During the operation, the EQOS Energie fitters will first climb the mast and attach the holding ropes to enable the helicopter to fly the old sections to the landing site. After the disassembly of the mast, the new parts will be flown in and directly installed. In the last step, the conductors and the ground wires will be reinstalled.


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