ROUND UP
M
arthinusen & Coutts has successfully completed the reha-
bilitation of a 70 MW synchronous condenser for the Société
nationale d’électricité (SNEL) in the Democratic Republic of Congo.
The rehabilitation and repair of the 70 MW 11 850 Volt 750 rpm
8-pole synchronous condenser was one of the single biggest under-
takings performed by a privately owned South African company in
the DRC.
Marthinusen & Coutts
was able to leverage the capabilities
and capacities of its experienced team to provide a high quality
solution quickly and expeditiously, within the required eight month
contract specification.
The synchronous condensers work in a critical part of the dc/ac con-
verter station in Kolwezi.The power comes from Inga Power Station in
the north of the country where ac power is converted to dc.This power
is transmitted down the dc line from Inga to Kolwezi and is converted
from dc back to ac at the converter station on Kolwezi.The power is
ultimately destined for a very demanding copper belt mining sector
in the Katanga province which has limited local generation capacity.
The synchronous condenser is critical for the operation of the
converter station in that it provides a source of reactive power which
cannot be transmitted via the dc transmission line and cannot be pro-
vided by the converter. It helps to provide the necessary inertia needed
for the whole system because of the mass of the rotating assembly
of the condenser and this also aids the stability of the ac system.
The condenser has an inside diameter of 2,4 m, with a core length
of 3 m, the rotor weighs 95 tons and the stator weighs 98 tons.The
immense size and weight of the condenser made it very difficult and
expensive to transport and the best option was for meant that Marthi-
nusen & Coutts to supply an on-site solution for SNEL.The environ-
ment was very challenging, with a complete lack of facilities on site
and the team had access to neither cranage nor a workshop facility.
However the technicians coped admirably and under very ardu-
ous conditions and provided a best practice service with only four
containers to house tools and equipment. Every single tool used by
the teamwas shipped up from Johannesburg.The logistical planning
and controls were extremely complex with spares and components
coming from a number of different parts in the world crossing several
borders to reach the site.
Marthinusen & Coutts’ understanding of local conditions in Africa
and specifically the DRC meant that it was possible to readily deploy
the team to site.The entire operation was staffed with skilled techni-
cal personnel from the company’s centre of excellence in Cleveland,
Johannesburg. Work began in April 2012 with the removal of the old
stator bars. No company in the southern hemisphere could manufac-
ture a set of quality stator coils, and Marthinusen & Coutts engaged
with one of the company’s technical partners, National Electric Coil
in the USA, to manufacture the stator bars. Thereafter Marthinusen
& Coutts was responsible for the winding.
Following an assessment of the condenser by Marthinusen &
Coutts, the full rehabilitation required:
• A full on site stator rewind
• Removing two faulty salient pole coils from the rotor and refitting
coils removed from unit 2
• Transport the two failed coils toM&C Cleveland to be re-insulated
to be kept as spares
• The manufacture and replacing of the complete damper bars and
quadrants
• Mechanical repairs
• New coolers had to be manufactured and fitted.
• Re-insulation in South Africa of the slips rings and the subsequent
refitting on site with the brush gear which was also completely
overhauled in South Africa
• Re-metaling of the bearings and manufacture of new brass oil
rings
• On site balancing of the rotor and the assembling of the entire
machine
• Monitoring the onsite running and operating conditions for a
month following the commissioning of the condenser
The rotor components were ordered through the OEM and after
cleaning and testing the core, testing the connection bus andmapping
the PT100 winding temperature indicators, the Marthinusen & Coutts
team commenced with the installation of the new components. The
final machining and balancing was done within the condenser’s own
bearing pedestal, outside the machine.
Enquiries: Richard Botton.Tel. 011 607 1700 or email richardb@mandc.
co.za.
Getting SNEL back on track
Drives, motors and switchgear
Fitting of the brush gear onto the field frame for the 8 250 kW AEI mine winder. Skilled technician connecting the halving joint.
Electricity+Control
July ‘13
12
