Rota Load Disconnections and the Impact on Water Supply

Rota Load Disconnections and the Impact on Water Supply

Over the past few years, the security of global energy markets has been under threat. As a result, the UK energy industry has procedures in place should a national energy shortage occur and there is not enough power to meet demand.

As a last resort, planned emergency power cuts, called ‘Rota Load Disconnections’, would occur across the UK. In this scenario, different areas of the UK would be on a rota, losing power for three hours at a time, to guarantee that customers are not unfairly impacted by outages.

Every postcode is now assigned a ‘Rota Block’ based on the geographical location and the site which supplies electricity to that postcode. Rota Blocks are labelled A to V, with letters F, O and V used for essential sites, such as hospitals, food production and airports. The sites which fall within those three letters are deemed ‘Protected’ and will not lose power in the event of a rota disconnection.

How does this impact the water industry?

Although this initially sounds like it just impacts power supply, it will also affect water supply, as the UK water industry is heavily reliant on power for both water treatment and distribution across their networks. In a Rota Load Disconnection scenario, water supply will be impacted.

The UK’s water companies can apply for inclusion of treatment works and essential assets, such as reservoirs and boosters that supply large populations, on the protected, essential-site list. However, the protected status can’t be awarded to every site, as a result this will leave most assets without power for three hours at a time, which means thousands of customers will also be without water. Not only will customers have no water supply, but the knock-on effect of these outages will put a huge strain on every aspect of the UK’s water network.

As technology has advanced, functions such as reservoir water level control, pressure monitoring and booster control have all been automated (i.e. use electrical power), with signals being sent to control rooms for monitoring. Therefore, in a power outage situation, if a reservoir’s level is automated but has no power, it could very easily overflow without network control being aware, as no signal would be sent.

Similarly, most boosters have to be manually restarted on site if a power outage occurs. If Rota Block A is switched off, for example, and a water company has 50 boosters within that block across 100 miles, the logistics of turning them back on manually would be extremely difficult to execute. Other assets would also need to be physically checked once the power is restored, as well as further issues that occurred during the outage. As outages would occur in consecutive blocks, it’s likely that another 50 boosters would immediately be switched off, causing consecutive issues that are impossible to solve with a limited workforce.

It’s easy to see how these scenarios will be extremely difficult to manage, and there’s no guarantee that turning an asset on will bring water supply back to an area if a different asset upstream/downstream is still offline.

The management and planning required for these scenarios is extensive, and water companies need to consider several factors for each rota block, including:

Network supply routes	Customer impact	Effects of rota upstream/downstream	Schedule of rota switch off
Asset characteristics	Asset impact	Number of assets per rota block	Key sites for protection status

WRc’s rota load disconnection expertise in action

WRc has analysed the factors above to create a ‘Rota Load Disconnection Customer and Asset Risk Score’ for a UK water company’s entire network. These scores detail which areas of their network are at risk and what assets cause this risk.

The datasets WRc created inform the water company’s Security and Resilience team where improvements need to be made to reinforce the network against all risks. The datasets also include a risk score for every customer on the network (~3-4 million) as well as over 1500 reservoir, booster and source sites.

The maps above show a small section of the water company’s network, detailing the type of asset that supplies their customers, along with the associated risk, based on rota schedule, customer elevation and asset characteristics (e.g. reservoir retention, protection status, booster type).