Successful completion of challenging electrical rotating machinery refurbishment projects has long been the hallmark of Marthinusen & Coutts, a division of ACTOM (Pty) Ltd. And it is this reputation that secured Marthinusen & Coutts the contract to complete the reassembly and recommissioning of a very large synchronous condenser in the Democratic Republic of Congo (DRC).
Marthinusen & Coutts Lead Field Services Technician, Wynand Willemse applies finishing touches to one of the SNEL 70 MVA synchronous condensers completely refurbished almost from the ground up, in the DRC.
The repair contract was awarded to Marthinusen & Coutts early last year by an international electricity equipment company currently engaged in an upgrade project on the hydroelectric power supply system for the DRC’s power utility, Société nationale d’électricité (SNEL).
Richard Botton, divisional chief executive at Marthinusen & Coutts, says that most significant about this order is the fact that it was placed on Marthinusen & Coutts by an international OEM who is a global leader in electrical engineering.
Botton says that Marthinusen & Coutts had previously repaired two of the Kolwezi power station condensers in earlier contracts a few years ago. “Part of the repair work on the third condenser had been done when the international company commissioned us to complete the job; this based on our experience and our successful complete refurbishment of the other two condensers,” he says.
The synchronous condensers are critical components of the DC/AC converter station in Kolwezi in the DRC, which converts the DC power transmitted on a 1 700 km transmission line from a converter at the Inga hydroelectric power station on the Congo River in the north. The power from the Kolwezi converter feeds the energy intensive Copperbelt in the Katanga Province.
The synchronous condensers supply the necessary reactive power, which cannot be transmitted via the DC transmission line or provided by the converter station. The inertia of the rotating assembly of the condenser provides the necessary energy to stabilise the power system in the region, which aids the overall stability of the grid.
The repair work undertaken on the 90 ton rotor of the 70 MVA condenser involved conducting a thorough inspection of the rotor forging and bare rotor by Marthinusen & Coutts’ on-site repair team. This was followed by the refurbishment of the bearings, and testing and fitting new salient poles that had been manufactured earlier by the international company to replace the original salient poles. This aforementioned company had also earlier rewound the stator as part of its portion of the repair work on the condenser.
Marthinusen & Coutts is also responsible for the balancing of the rotor. The rotor weighs 90 tons and runs at 750 rpm in a compromised installation from a foundation stiffness point of view. “Significantly, we are employing the services of arguably the top balancing specialist in South Africa who will carry out the dynamic balancing on-site,” Botton says.
In line with Marthinusen & Coutts’ policy of investing in the latest technology , the company recently acquired a Bently Nevada ADRE 408 portable vibration and balancing system which will be used for this task. Marthinusen & Coutts’ understanding of local conditions in Africa, and specifically the DRC, provides a major advantage to the customer. Skilled technical personnel from Marthinusen & Coutts’ centre of excellence in Cleveland, Johannesburg were deployed to site and the condenser is scheduled for recommissioning at the end of 2016. “The recommissioning will be overseen by our customer and SNEL officials,” Botton concludes.
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