The last few years have seen a number of Grid Supply Points come under pressure
from the level of generation on the distribution networks exporting their power. This is
the most extreme form of the electricity network operating in the opposite way to
which it was originally designed, where sections of the network are not only supplying
their own demand but also exporting the surplus onto the transmission system.
The area of Kent being considered in this project contains only two GSPs of the >350
nationwide, and a third is being established in the area. Nevertheless, it currently
requires 34 contingency scenarios to be analysed in order to understand it fully.
The introduction of wind, solar, and the presence of interconnectors increases the
number of extremes that need to be analysed - there is no longer a simple ‘day of
highest winter demand' and 'day of lowest summer demand'. There are therefore more extremes; a greater requirement to monitor all contingencies; and a growth in the number of GSPs being affected.
Contingency analysis is a valuable tool to predict the effect of outages like failures of
overhead lines and to take actions to keep the distribution network secure and
reliable. UK Power Networks will trial for the first time the use of contingency analysis
in the GB electricity distribution network. It will also be the first trial of the
implementation on a coordinated and interfaced basis with the electricity transmission network.
The KASM project will tackle and demonstrate the value of contingency analysis
software in operational timeframes on the network in East Kent, delivering
conservatively estimated net benefits of £0.6m. Once proven successful, replication of this method across GB could conservatively provide net benefits of over £65m over the lifetime of the investment, when compared to business-as-usual approaches.
Distribution networks are designed to security standards that ensure redundancy in
components and supply points. Distributed generation such as on-shore wind and solar photovoltaic (PV) relies on an up-stream connection to export its power, and can therefore be affected by both maintenance and construction outages and outages caused by faults unless there is a redundant or alternate route for its power.
As such, there is a strong focus within Distribution Network Operators (DNOs) to find
contingency plans to avoid or shorten maintenance outages; to restore demand customers; and to maintain routes for generation in event of a fault.
This role within DNOs, starts with the network planners who design the network at the desk, and respond to new connection requests by identifying points of connection to the network.
The role continues with outage planners, who specialise in maintaining and optimising the programme of outages to best serve customers. Finally, control engineers who monitor the network in real-time, issue and manage safety permits to staff working on the network, and respond to faults by reconfiguring the network.
The set of activities described above is generally referred to as ‘outage planning’ and
‘contingency analysis’ and has been carried out by the GB DNOs for many years. However, these are now being carried out in a significantly different context, in particular taking the effects of distributed generation into account.
The UK Renewable Energy Roadmap set out a comprehensive target for 15% of the
electricity generated in the UK to come from renewable energy sources by 2020.
The targets established in 2011, were reaffirmed in 2013. A significant number of these new renewable energy sources will connect directly to the distribution network. The UK’s policy is part of the overall European Union (EU) target of achieving 20% penetration by renewable energy sources in total energy consumption by 2020. UK Power Networks’ South Eastern licence area has, for example, 100 large-scale solar photovoltaic plants with a combined capacity of 1140 MW awaiting connection to the network, which will more than double the amount of distributed generation in the area.