2 November 2017
When the Mucomir Hydro-power station in Scotland identified the urgent need for a new Brushless AC Exciter it turned to Quartzelec, the independent engineering service provider that’s globally recognised as an expert in rotating electrical machines, to develop, implement and commission the retrofit solution.
In addition to winning the contract to refurbish an existing generator stator and rotor, Quartzelec was also contracted to design, build and commission a new AC brushless exciter to replace the old DC exciter. As the owner and operator, SSE was looking to eliminate both the dust and maintenance burden plus significantly reduce the risk of extended outage resulting from brush and commutator wear. The existing commutator was suffering badly with uneven wear issues, due in part to the intermittent loading and the humid environment at the site.
Owned and operated by SSE, the Mucomir power station is a run of the river hydro facility that’s fed from Loch Lochy. The station which has been in continuous operation since 1962 is part of the Great Glen Hydro Group and the power plant comprises a Kaplan turbine driving a 3300V, 40pole, 150rpm AC synchronous generator.
“Each project comes with its own unique requirements,” comments David Swaffield, Quartzelec’s Lead Electrical Engineer on the Mucomir Hydro-power station project. “The slow 150rpm shaft speed of this turbine, presents its own challenge for the electrical machine design which, when combined with the limited access and available footprint along with the available cooling and the limited envelope, meant this project necessitated some significant engineering and a high pole count – but we were more than up to the task.”
The brief for the Quartzelec design team was to retrofit a new AC brushless exciter solution into the existing footprint. Work began in August 2016 to characterize the available space, existing cooling circuit and fan performance curve. Then drawing on significant heritage and expertise Quartzelec has at its disposal, a 3-phase AC Synchronous generator and rotating rectifier hub could then be designed to fit into the modified exciter housing while retaining the existing mounting interfaces.
The resulting designs were then approved and fabricated over subsequent months at Quartzelec’s engineering facilities in Rugby and in June 2017 the solution was shipped to site and installed during a scheduled maintenance window. The new solution provided to the customer is a bespoke brushless exciter to meet the duty of this site, whilst retaining the original fan, shaft interfaces and housing. Critically, however, it eliminates the risk and maintenance overhead of the original brush gear.
“This is a key part of our operation here at Mucomir, so we needed a cost effective but practical solution to ensure our continued operation. We were delighted with the service and attention to detail which everyone at Quartzelec demonstrated in respect to this project,” added Angus Fraser, Lead Engineer for SSE. “Quartzelec clearly demonstrated their ability to draw on their heritage and expertise, developing a bespoke, retrofit design for this existing hydro plant ensuring the major overhaul could be successfully completed.”
Over recent months Quartzelec has seen a significant increase in demand for retrofit solutions along with preventative maintenance and inspections. This reverses the trend prevalent at the start of the last economic downturn, a decade ago, when many looked to defer upgrades and maintenance in a bid to cut costs.