sparks
ELECTRICAL NEWS
august
2013
16
Motor control centres and motor protection
INTENSE competition for amajor contract by Eskom for the
manufacture and supply of mediumvoltagemotors to replace
most of the aging units operating in its coal-fired power plants
was aroused globally when the utility invited tenders for the
contract inmid-2010.
The contract, dubbed theMotor Upgrade Programme
(MUP), is worth R130-million and encompasses design, manu-
facture and supply of a total of 125motors for 10 of Eskom’s
coal-fired power stations, namely Arnot, Komati, Camden,
Hendrina, Kriel, Matla, Duvha, Lethabo, Grootvlei and Kendal.
The company commenced deliveries of the newmotors in
R130-m Eskom power plants MV motors
replacement contract awarded
Mpho Motloung, a contracts engineer for ACTOM Electrical Machines, checks over some of
the motors produced for Eskom’s power stations.
November last year and is scheduled to complete them in
mid-2014.
Themotors, consisting of amix of ACTOMElectrical
Machines’well-known UNIBOX andMS4 series customised
units, range in power from200kW to 10MWand are for
use in awide variety of applications that include ID fans,
FD fans, PA fans, mills, conveyors, boiler feeds and cooling
water pumps.
TonyTeixeira, ACTOMElectrical Machines’general man-
ager, says an important factor forming part of the technical
qualifications that counted in the company’s favour in
being awarded the contract was the great
care that was taken by its engineering team in
ensuring completemechanical interchange-
ability between the newand the oldmotors.
“This is a key requirement of the contract,
for whichwe, as the supplier, carry the
responsibility. It involved a lot of painstaking
and time-consumingwork visiting all the sites
to confirm that our dimensions and other pa-
rameters for the existingmotors were correct
to ensure that the newones would be fully
interchangeablewith them,”he explains.
“We also had the advantage of having
produced and supplied themajority of the
original motors in conjunctionwith our
international technology partners at the time,
sowewere already familiar with their perfor-
mance and load characteristics.”
Enquiries: (011) 899-1081
IN order to keep a plant running optimally, New-
Elec’s MAmotor protection and control relay, when
connected to a PLC, can provide real-time diagnos-
tics of problem conditions by means of alarm flags
so that steps can be taken to avoid downtime.
The motor’s abnormal operating conditions or
faults can be detected at an early stage tominimise
shut-downs by initiating preventive measures prior
to tripping. The MA relay also provides an economi-
cal framework for upgrading older plants to full
automation due to the fact that its digital inputs can
accommodate voltages from 24 - 220V ac or dc.
A comprehensive range of protection features are
included in the MA relay such as three independ-
ent over-temperature inputs to protect bearings,
five digital inputs and two programmable outputs,
all at a competitive price. Additional protection
includes integrated earth leakage with harmonic
filtering, earth leakage core balance CT and current
sensing CTs up to 250A. Optional auto-restarting on
load loss tripping is possible, as well as automatic
co-ordination of associated trip functions for high-
energy fault interruptions.
The MA offers real time and date stamping
recorded by the relay for the last four trips, a record-
ing utility of actual RMS loads, thermal condition-
ing, mains phase voltage, line voltage, as well as
status of digital inputs and output contacts. The
user has the possibility of expanding the unit for
fieldbus communications via Profibus DP, Modbus
RTU and Canbus protocols.
Enquiries: (012) 327-1729
Optimising plant
production and
operation
