The connection of large amounts of new generation, most of which is intermittent renewables, in Scotland and the north will cause overloading in the northern transmission network unless appropriate reinforcements are in place. Future power transfer requirements could be more than double compared to what they are today in some scenarios.
The future energy scenarios suggest the northern transmission region could see a range of changes as shown in the graph.
All four scenarios suggest growth in low-carbon and renewable generation, in addition to new storage and interconnector developments. The connected fossil fuel generation could see sustained decline in all but the Steady Progression scenario.
Large connections could cause network issues if connected to the north region.
Presently, most of the northern transmission network is oriented for north-south power flows with connections for demand and generation along the way.
At times of high wind generation, the power flow will mostly be from north to south, with power coming from both internal boundary generation and generation further north in Scotland.
When most of this area and Scotland is generating power, the transmission network can be highly overloaded. The loss of one of the north to south routes can have a highly undesirable impact on the remaining circuits.
The highly variable nature of power flows in the north presents challenges to voltage management, and therefore automatic reactive power control switching is utilised. This helps to manage the significant voltage drop due to reactive power demands which arise at times of high levels of power flow on long circuits.
Operational reactive switching solutions are also used to manage light loading conditions when the voltage can rise to unacceptable levels. The high concentration of large conventional generators around Humber and South Yorkshire means that system configuration can be limited by high fault levels. Therefore, some potential network capability restrictions in the north can be due to the inability to configure the network as desired due to fault level concerns.
As the potential future requirement to transfer more power from Scotland to England increases, B7 and B7a are likely to reach their capability limits and may need network reinforcement. The potential future restrictions to be overcome across B7 and B7a are summarised:
- Limitation on power transfer out of north east England (boundary B7) is caused by thermal limitation for a fault on the double circuit between Harker–Hutton.
- At high power transfer, thermal limitations occur on a number of circuits within the north east 275kV ring.
- Limitation on power transfer from Cumbria to Lancashire (boundary B7a) occurs due to thermal limitation at Padiham–Penwortham circuit.
The need for network reinforcement to address the above-mentioned potential capability issues will be evaluated in the NOA 2020/21 CBA.