Synchronous Condenser

Frequently Asked Questions

• What is a Pathfinder project?

  The ESO (now known as the National Energy System Operator or ‘NESO’) Pathfinder programme is designed to help ensure the stability of the electricity network via the delivery of new technical stability services within targeted regions across England, Scotland and Wales, enabling greater volumes of renewable energy projects to be connected to the grid in the future.

• What is a Synchronous Condenser?

  A Synchronous Condenser (also called a Synchronous Compensator) is a rotating electrical machine, typically with a heavy physical mass, similar in design to an electrical motor. It operates without an engine of any form, therefore it does not produce electricity, but provides dampening to frequency fluctuations across the interconnected transmission network. Its main function is to provide grid stability services—especially reactive power support, voltage regulation, and inertia—which are increasingly important as renewable energy sources like wind and solar, themselves are less able to provide stabilising characteristics into the network.

• Does it generate electricity?

  No - a synchronous condenser does not generate power. As a result there are no additional airborne emissions or requirements for water usage.

• Why do we need this technology?

  As the share of intermittent renewables increases, and the output of conventional power plants declines, we lose inherent grid-supporting and stabilising characteristics. The NESO Pathfinder events have sought to secure specific network stability services in a cost-effective way:

  • Reactive Power Compensation (Voltage Support): Intermittent renewables such as wind and solar mostly use inverters, which to date have not offered the network the amount of reactive power required to deliver a balanced and robust network. Synchronous condensers can dynamically absorb or inject reactive power, helping maintain proper voltage levels on the grid in a reliable and targeted way.

  • Inertia Provision (Grid Stability): Traditional spinning generators provide rotational inertia, which helps resist sudden changes in frequency (e.g. during a fault or outage). Intermittent renewables, such as wind and solar, lack inertia; synchronous condensers may provide large amounts of inertia via the connection of their rotating mass into the system, improving frequency stability.

  • Short-Circuit Power Support: During faults, synchronous machines such as a Synchronous Condenser can contribute to fault current levels, aiding protection systems in detecting and isolating problems and faults within the network.

  • System Strength and Grid Resilience: In weak grid areas (common where renewables are abundant but transmission is limited), synchronous condensers improve system strength, reduce voltage fluctuations, and stabilising power flows.