Loeriesfontein Wind Farm, in the Northern Cape, has been making use of a mobile transformer to allow for an early connection to the grid for commissioning of the turbines, prior to the energisation of the Helios substation, which is the permanent grid connection.
The mobile transformer will do two things, firstly, it will provide a temporary supply to the project, to mitigate the risk that Eskom transmission is delayed with energisation of Helios. Secondly, it will allow for early grid code testing of Loeriesfontein Wind Farm, which will ultimately increase the chances of early operations, ahead of the Commercial Operations Date.
“We have worked very closely with Eskom to supply and operate the mobile transformer, which is typically used by the Utility to temporarily connect to substations during maintenance or unplanned shutdowns to allow continued use of substations. Mobile transformers are not normally used to connect Wind Farms to the distribution system,” explained Kevin Foster, Country Construction Manager for Mainstream Renewable Power.
The Helios substation energisation is on track for September 2017, at which point the Loeriesfontein Wind Farm will be able to commence with final grid code testing prior to commercial operations.
CONCO is responsible for the electrical component of the balance of plant works, including the engineering, procurement and construction of the medium voltage collector system, substation, overhead line connection and the temporary transformer.
How the transformer fits into the plant:
Each wind turbine is connected to a step-up transformer which boosts the generating output of the wind turbine generator from 690 V to 33 kV. These transformers are located at the base of the wind turbine. From here the cables throughout the wind farm bring the 33 kV current from the step up transformers to convene at the substation where the main transformer is situated. The main transformer at the substation increases the voltage further from 33 kV to 132 kV – the voltage required to transfer the power to Eskom.