The Problem in Detail
Our customer was developing a 7MW Wind Farm that was to be connected to the network at 33kV. Enspec were engaged to carry out the grid connection studies which included a P28 assessment. The aim of the P28 assessment was to accurately model the planned site and Wind Turbine transformers to allow for a voltage dip energisation comparison to be carried out against the P28 limits. This study will ensure the site can be connected as planned and that the connection agreement will be abided by.
Finding the Solution
Enspec liaised with the customer and key equipment suppliers to obtain all of the required site data. This was then used to build a representative model in PSCAD. The Long Term Development Statement for the planned connection location and DNO was used to obtain the Point of Common Coupling fault level and X/R ratio, this was also represented within the model.
Making it all Work
Once built the model was used to carry out a series of transformer energisation studies to assess the likely voltage dips against the P28 envelopes. Due to the limited number of transformers planned for the site and the expected number of times they will be energised per year, the site was assessed against the very infrequent P28 envelope.
What that means for the project now
The site was confirmed to be fully compliant with the very infrequent P28 envelope and was approved for connection by the DNO. This allowed for the site to be commissioned and energised within the planned schedule and is now generating clean electricity for the grid!