The electricity system operator (ESO) at National Grid has launched a new tender for reactive power adsorption to limit voltage in the Mersey region over a 9-year period starting in April 2022.
The ESO said it is the longest duration over which it has ever procured reactive power services.
Reactive power refers the ‘wattless’ power required to push active power around the electricity network. Raising reactive power on the network increases the voltage, whilst lowering it does the opposite. To keep voltage levels within operational limits, the ESO instructs generators and other asset operators to either absorb or produce reactive power.
The announcement follows an earlier “pathfinder” tender for reactive power services in the Mersey region, which was issued in October. Applicants to the latest tender will need to make a technical submission on 13 December 2019 and a commercial submission on 21 February 2020.
Contract winners will receive availability payments but not utilisation payments. They will need to be on call 24/7 and will be penalised if they are unavailable. The minimum unit size is 15MVAr, or 5MVAr for individual components within an aggregated unit.
The ESO also announced earlier this week that a solar farm in East Sussex operated Lightsource BP has been successfully used to provide reactive power services overnight as part its Power Potential project with UK Power Networks (UKPN).
The trial, which was conducted at the beginning of November, required Lightsource to upgrade the invertors at the solar farm to allow it to convert active power from the grid into reactive power. It marked the first time a solar farm connected to the distribution network had been used for voltage control.
The Power Potential project aims to create a reactive power market for distributed energy resources in the South East.
Speaking to Utility Week, ESO project lead Biljana Stojkovska said the trial with Lightsource and UKPN sought to demonstrate that a solar farm is technically capable of providing reactive power services; more specifically, that it is able to change its voltage set point from one value to another within two seconds.
She said the wider Power Potential trial will begin in early 2020 and conclude in October. The market will begin operating around April or May. If things go smoothly, then the ESO will then start rolling out similar markets across the country.
Stojkovska said voltage control is “one of the most critical elements” of the ESO’s work to make the power grid ready for zero carbon operation by 2025: “The network actually needs quite a lot of voltage control, not only for high-voltage situations when demand is low, but also in the cases when we have unexpected outages on the system and voltage goes low.”
She said concerns over the latter prompted the Power Potential project: “The South East is a very sensitive part of the transmission system and we have a dynamic voltage control problem there…
“What is characteristic in the South East is we have very variable and intermittent generation. We have a lot of interconnectors coming, we have two big offshore windfarms and we have embedded generation connected to the distribution network.”
She said the situation that “really worries” the ESO is when there is an outage on an important transmission line between Kemsley and Canterbury in Kent. This forces electricity from these sources to be transmitted through a long circuitous route around the region, lowering voltage on the network.
Earlier this month, the ESO launched its first ever tender for inertia.