Loss of communication on a wind farm can sometimes be due to a defect of the optical fibre. These cables are sometimes buried directly into the ground without any protection (reinforcement or sheath). The risk of communication incidents increases then. A rupture of the optical fibre can be caused by pests (rodents) and in a lesser extent by crushing due to ground movements.
When communication with the plant is interrupted, the first step is to identify the cause. If it is due to a rupture of the optical fibre, an analysis via reflectometry has to be performed in order to locate and characterize the defect. This technique based on the reflection of waves will allow identifying if the cable is damaged on a single location or several, and if the rupture of the cable is total or only partial.
Once the defect has been localised, a trench is dug to reach the communication cables in order to access the damaged section. However, as the optical fibre is frequently buried with high voltage cables, the shutdown of the wind farm or a part of it is necessary.
The defective section is then replaced with a brand new fibre, connected to the existing cable through junction boxes. Reflectometry tests are then carried out again in order to control the effectiveness of the repair.
In order to minimise production losses (caused by unidentified wind turbine downtime due to the absence of communication) a long term and profitable solution has to be implemented. Greensolver recommends either to install protective sheath or a steel-reinforced optical fibre – at least on the sensitive areas of the wind farm – in order to reduce the risks of a new rupture of the optical fibre.