Siemens has completed a major project with Drax Group to upgrade the infrastructure in the iconic Cruachan pumped hydro storage Power Station with greener technology. Replacing equipment that was over 30 years old, the project included the UK’s first installation of four modern Siemens generator circuit breakers that do not depend on the sulphur hexafluoride (SF6) gas commonly used in switchgear.
Cruachan underground pumped hydro storage plant, also known as the Hollow Mountain, supplies up to 440 megawatts of flexible, on-demand electricity to the National Grid from four reversible turbines and has played a critical role in stabilising the UK’s electricity system throughout the Covid-19 pandemic.
SF6 gas has traditionally been used in circuit breakers due to its good insulation capabilities but is classed as a greenhouse gas. Siemens’ innovative non-SF6 generator breakers use vacuum technology instead, making them safer and more environmentally friendly. There is no risk of gas leakages and no need for costly maintenance carried out by specialist engineers. Built from materials that are completely recyclable and hermetically sealed, the vacuum circuit breakers also have fewer moving parts, reducing wear and significantly boosting reliability. Each vacuum interrupter has a mean time to failure of 77,000 years and can run through 10,000 operating cycles before a service is required – for Cruachan, that equates to ten years of maintenance-free operation.
Cruachan Power Station provides fast, reliable power to the National Grid, as well as the flexibility to absorb excess power - meaning it can start generating or pumping electricity within less than a minute, as well as providing system support services to maintain secure supplies of electricity and support more renewables like wind and solar to come onto the grid. Using a generator circuit breaker simplifies Cruachan’s operational procedures, synchronizing the load and avoiding extensive damage inside the transformer.
“With Cruachan playing a vital role in supporting the growth of wind power in Scotland and enabling further decarbonisation of the grid, it is only right that the infrastructure inside the power station is also environmentally friendly,” explains Ian Kinnaird, Drax’s Head of Hydro. “Working closely with Siemens, we retrofitted a first-of-its-kind solution that uses innovative vacuum circuit breaker switching instead of SF6 gas. Not only has this removed any potential environmental impact and health and safety concerns caused by the previous, outdated switchgear - the new generator breakers are practically maintenance free, reducing costs. It’s a really neat solution.”
Ross Fraser, technical manager, Power & Utilities, Siemens adds: “Cruachan Power Station is contracted to provide reliable, clean electricity to the grid, so it is paramount that the technology installed is dependable, safe and sustainable. Siemens vacuum circuit breakers are built on more than 40 years of engineering experience and have proven their reliability in installations all over the world, so we are delighted that Drax chose this solution for the UK’s first implementation inside a hydro power station. The project was certainly unique as we were working 1km underground at the heart of Ben Cruachan mountain, but by working very closely with the Drax team, we achieved a quick turnaround and had the first unit fitted in under 12 months during planned maintenance downtime.”
The generator circuit breakers were installed after being transported through a narrow, one-kilometre long tunnel that leads deep into Ben Cruachan mountain. The work had to take place over the course of two years during planned maintenance downtime to reduce disruption to this critical national infrastructure.