Example Case: B6
To show you how this might work practically, the following section presents results from using probabilistic analysis on the B6 boundary.
On the graph above, we can see that the black region, the area in which an unacceptable outcome was present below the boundary capability limit, covers the overlap between plots almost entirely. The black region equates to a BCP index of 6.66% or 145.9 hours. To turn this region green, solutions providing additional capacity for that duration need to be considered.
Identifying additional requirements is not limited to just the black region only. We can see from the acceptable plot that there is potential for increasing power transfer beyond the peak capability level, however doing so will increase the BCP index accordingly due to the unacceptable outcomes increasing.
By evaluating BCP values beyond the boundary capability limit we can consider new opportunities for solutions and evaluate whether it may be more appropriate to use a solution that provides short duration capability rather than year-round capability or a combination of the two.
The graph below shows how the BCP index will be distributed between duration and capacity. As stated earlier in the document, at present we are unable to represent the magnitude of additional requirement. However, we can see the maximum duration requirements will be needed for. For boundary B6, we can see that no single magnitude will exceed a duration of 40 hours when transferring power at a time.
To better understand how certain network conditions influence the probability of an unacceptable outcome, we can look at scenarios on a CART diagram.
When the network sees embedded generation output across the North East of England and Central Scottish regions, there is the lowest probability of an unacceptable power transfer outcome across B6. On the contrary the highest chance of an unacceptable transfer outcome occurs when there is high embedded generation output coupled with low wind from Central Scotland and low interconnector and storage output around the B6 region. This analysis allows us to identify solutions to accommodate additional requirements to securely transfer power across the B6 boundary.
We’ve done this similarly for boundaries B2 and B4 and their results are summarised in the table below:
|Boundary||BCP Index||CART Summary|
|B2||0.92% or 20.1 hours over the winter season at chapter 3 capability value||A combination of high wind in the Argyll and Bute region, low wind in the North East of Scotland and relatively high hydro output results in the best network performance. Low wind output across the central highland and Argyll and Bute regions in Scotland results in more constrained boundary performance|
|B4||2.29% or 50.1 hours over the winter season at chapter 3 capability value||Low output from central Scotland, low hydro output and low wind output in the Argyll and Bute region, results in relatively poor network performance. Low output from Central Scotland but a high hydro output results in relatively better boundary performance.|