ABB provides turn-key generator circuit breaker retrofit for Kemijoki Oy

ABB customer, Kemijoki Oy, is one of the most important players in Finland’s renowned carbon neutral electricity system – responsible for balancing half of the country’s grid output – as well as being the leading provider of hydro and regulating power in the colder North and East of the country. Operating 20 power plants, Kemijoki can adjust the production of safe and secure hydropower by the second, providing essential energy for Finland’s increasingly clean grid.

The plants – Matarakoski completed in 1995 and Kelukoski in 2001 – both have an 11 MW output and power some 10 000 family homes between them. They had been running on their original SF6-based HPA circuit breakers and despite being technically competent, the aging circuit breaker were no longer in line with Kemijoki’s strict environmental diversification program or the latest global Dual Logo Standard. Lack of available spare parts was also becoming an issue for breakers that had been in commission for around 30 years.

However, completely overhauling the existing switchgear operation was not financially sustainable and downtime had to be at the absolute minimum because of the key part Kemijoki hydropower plays in the country’s energy security and production.

ABB Electrification Service team was able to provide a retrofit solution that saw downtime reduced to hours rather than weeks, ensuring the power was kept on without any disruption.

A customised 12 kV version of the market leading MV VD4G vacuum circuit breaker family was specified, which clears potentially harmful short-circuit faults in tens of milliseconds, thereby preventing severe damage and lengthy plant downtime. Resin-insulated vacuum interrupters guarantee higher protection of the core components and it is a complete asset protection solution that safely masters fault conditions with delayed current zeroes and severe transient recovery voltages.

Jarkko Virtanen, Vice President, Electrical and Machinery Technology at Kemijoki Oy, said: “Good operational preconditions at the river are a prerequisite for cost-effective hydropower production, so ABB made it very easy for us with a plug-and-play model that we did to instruction to save valuable time, money and resource.

“Compared to a full overhaul of the complete medium voltage switchgear, we saved almost a month of downtime with the retrofit – taking just hours rather than several weeks – and in an industry where 24/7 power output is expected that’s a lot of vital energy production and lost revenue saved. We also have a much more reliable operational procedure, because it handles the currents much better, and cost effectively extends the lifecycle of our generator applications by at least another 20 years.”

Sixten Holm, Business Development Manager for ABB Electrification Service division in Finland, added: “We have a long-standing and collaborative partnership with Kemijoki Oy and it works because we know and trust each other. They welcomed the input and expertise of our Service Division and together we arrived at a solution that brings much higher plant reliability and meets stricter safety standards.

“VD4G represents ABB’s optimum solution for generator applications where the highest possible protection is needed, especially in case of critical short-circuit conditions, while the retrofit’s smaller footprint provides a cost-optimised solution that saves valuable and essential time during site commissioning.”

Now that a successful blueprint is established, retrofit solutions are planned for other power plants, while the open switchgear system of Kemijoki’s larger and more heavy-duty power plants are being considered for the latest in DPA pressure breakers.

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