1. Engineering Practice Report
Name: Paul Soko
Student Number: 08107917
School: Engineering
Programme: Electrical & Electronic Engineering, 3
rd
Year
Employer: Copperbelt Energy Corporation
Period: 20th
January to 30th
April 2011
2. 1.0 Executive Summary
For a period of 12 weeks that I had been positioned at Copperbelt Energy Corporation’s
Emergency Power Department, Instrumentation Secession. During my period of
attachment I was given a range of tasks that proved them selves to be both interesting
and challenging. A select number of tasks I was involved in included:
The clutch scrapping at Maclaren GTA site in Luanshya
The engine swap at Maclaren GTA site in Luanshya
Checking of exciter diode assembly on Luano GTA 1 in Chingola
MPU fault diagnostics at Bancroft GTA site in Chililabombwe
The investigation of faulty fire protection systems (TYCO)
The removal of the proximity sensors and thermocouples on the clutch assembly
on Luano GTA 1
Attending of daily departmental meetings
As well as involvement in current projects, I also completed general tasks such as,
Good house keeping, Routine maintance, Preventive maintance, photocopying and
scanning of documents, mail running, and the retrieval / validating of data when
requested and safety and toolbox talks.
Over the past 14 weeks I have gained an invaluable insight into the operation of the
power distribution industry with a major emphasis on the operation, function and control
of Gas turbine alternator, am now proficient at reading system diagrams, in their various
formats, and cross correlating them with other data streams and also the identification
of electronic components and their workings. I have further developed my skill in the
use of electronic and mechanical calibration equipment these include the Multi-meter,
Tone Generator (cable tracer), Process calibrator (function calibrator) , Oscilloscope ,
Gas comparator , which are heavily implemented in the trouble shooting and calibration
of instrument controls of the GTA,s as well as other control and electronic circuits of
every day use equipment, which include air conditioners , power supplies etc. the
experience I have gained in this placement has proven invaluable and has put me in
good stead as I approach my fourth year , laying a solid foundation which will facilitate
development as many courses place an increased emphasis on Electrical & Electronic
Engineering ( control systems)
3. Table of Contents
1.0 Executive Summary ...................................................................................2
3.0 Introduction ...............................................................................................4
4.0 Background................................................................................................5
ROLE OF EMERGENCY POWER DEPARTMENT....................................5
5.0 Tasks Performed & Duties ..........................................................................7
5.1 The Engine Swap at Maclaren GTA site in Luanshya................................7
5.2 Scrapping on Pinion Gear Box Bearing at Maclaren GTA site in luanshya .8
5.3 Checking of exciter diode assembly on Luano GTA1 in Chingola .............8
5.4 The investigation of faulty fire protection systems (TYCO).......................9
5.5 The removal of the proximity sensors and thermocouples on the clutch
assembly on Luano GTA 1..........................................................................10
5.6 MPU fault diagnostics at Bancroft GTA site in Chililabombwe ...............10
5.7 Preventive and Routine Maintenance......................................................11
5.8 Meetings and presentations ....................................................................11
6.0 Photos......................................................................................................12
7.0 Experience Gained ...................................................................................14
8.0 Conclusion...............................................................................................15
4. 3.0 Introduction
From the 20th of January 2011 to the 30th of April 2011, I was employed by the
Copperbelt energy corporation to work in their Emergency Power Department were I
was assigned to the GTA (Gas Turbine Alternator) Instrumentation Secession.
During the course of my placement I was involved in a number of tasks and projects
which all proved to be quite interesting, while providing some unique chalenge . these
tasks some of which have been aforementioned , identified key issues that are
paramount to ensuring the successful operation of the Gas turbine alternator and thus
ensuring that emergency power is always available .These issues include , but are not
limited to , ensuring reliability and quality on the GTA controls , instruments but also the
safety of the GTA and work staff, while meeting these fundamental criteria an onus is
placed on the high level understanding of all three areas of the gas turbine alternator
which are the Electrical, Instruments and the Mechanical conscripts. This is due to the
Copperbelt energy cooperation high dependence on the GTA, s in the case of a Grid
outage or in events of peak looping.
I worked directly with the instrumentation secession of the GTA department under the
Secession Manager Engineer Y. Mwale, Secession Engineer, Engineer R.K.
Munungwe ,Mr. B Mubabe (foreman) , Mr. K. Mbindo (Snr Artisan), Mr. M.S .Nzima
(Artisan) ,Mr. P. Ngombe (technician) and fellow student David Kabanshi also a 3rd year
Electrical & Electronic Engineering student at the Copperbelt University. This
partnership allowed me to gain an insight into the operations of the controls and
instrumentation of Gas turbine alternators and to see how and appreciate the three
secessions of the department.
5. 4.0 Background
The Copperbelt Energy Corporation plc is an Electricity Utility Company operating on
the Copperbelt Province of Zambia with the main goal of Supplying of power to mines
and related industries. Its Infrastructure includes more than 835km of 220kV and 66kV
transmission lines, 36 major substations, 520km of fiber optic, 80MW of Gas turbine
generation and a very skilled dedicated workforce, apart from supplying the mines with
power the company has also engaged in the provision of fiber-optic based
telecommunications services, Power Transmission for ZESCO and SNEL (DRC) and
the development of a Renewable Energy fuel Plant and other various large scale
projects.
ROLE OF EMERGENCYPOWER DEPARTMENT
CEC customers are mainly involved in mining operations which require reliable and fail
safe power supplies to support continuity of their operations and safety of personnel
working underground. Gas Turbine Alternators are mainly used as;
i) Emergency standby power supply source to guarantee minimum supply
requirements for customers in the event of ZESCO supply and/or power
falling below minimum supply (MSL).
ii) Maximum demand control through peak lopping.
CEC guarantees Minimum Supply Limit (MSL) power to its customers to meet their
essential load requirements. This stands out as the bedrock of CEC existence without
which ZESCO or any other utility company could offer unchallengeable and competitive
alternative power supply to the mining industry. But because CEC has these emergency
power plants, there has been no comparable challenge. Out of the total installed
capacity of 80MW, 76.8MW is the total system Minimum Supply Limit (MSL). The
Minimum Supply Limit (MSL) is the minimum power necessary to keep the following
installations operating as per Power Supply Agreement (PSA);
i) Man winder- for hoisting of personnel from underground
ii) Onsite medical facilities
iii) Pumping – dewatering operations to prevent flooding of the mines
iv) Ventilation fans-to provide ventilation for personnel underground
v) Any other installations as may be agreed between CEC and customers
In the event of loss of power supply from ZESCO or available power falling below the
system MSL of 76.8MW, CEC would run GTAs as source of power to supply. Failure of
CEC to supply Minimum Supply Limit (MSL) would result in prohibitively high charges
for compensation and damages on behalf of customers. It is for this reason that CEC
6. should ensure that the Emergency power supply source is reliable. Fail safe power
supply is a must to support the operations of customers and contribute to the economy
of Zambia. Flooding of the mine for example would result in closure of the affected mine
and loss of revenue for CEC. Loss of supply would also result in possible loss of human
life as the man-winders would not operate to remove men from underground. All this
would be at a cost to CEC. In the last five years there has been no emergency situation
requiring of these plants.
However occurrence of emergency situation can not be completely ruled off. The
ZESCO 330KV power supply lines from southern part of the country where generation
is done to the Copperbelt all run in the same way leave and are susceptible to
vandalism or aircraft accidents etc. In 1989/90 when ZESCO generating station at
Kafue Gorge was damaged by fire, all the GTAs were continuously run to support the
system. In 1992 when there was a drought in the southern part of Africa the GTA plants
were run to support the system because ZESCO did not have enough water levels in
their dams to use for power generation. No emergency runs have been carried out in
the last five years however, simulation runs have been done.
Emergency simulation runs with our customers have been successfully done. The
plants are run to supply power to selected loads consisting of underground water
pumps, ventilation fans and winders. During these exercises the customer personnel
are trained and given the opportunity to start the plants and apply loads.
Copperbelt Energy Corporation plc has six Gas Turbine Alternators (GTAs) strategically
located on the Copperbelt near customer load points. The plants use diesel fuel and
total installed capacity is 80MW.Details as shown in the table below.
Table 1 – Plant and Capacity
GTA Plant Year
Commissioned
location Capacity(MW)
Luano GTA 1 1969 Chingola 20
Luano GTA 2 1969 Chingola 20
Bancroft GTA 1 1971 Chililabombwe 10
Bancroft GTA 2 1971 Chililabombwe 10
Kankoyo GTA 1978 Mufulira 10
Maclaren GTA 1978 Luanshya 10
Total Installed Capacity 80
7. 5.0 Tasks Performed & Duties
During my 14 weeks at Copperbelt Energy Corporation, I helped in undertaking the
following tasks:
5.1 TheEngineSwapat MaclarenGTAsiteinLuanshya
It is routine for one of the nine Avon Rolls Royce engines owned by Copperbelt Energy
Corporation to undergo a Rahall once a year. Eight engines are used in the GTA sites
while the ninth engine is a spare. A rehalled engine had been returned from Scotland
were it was rehalled by ALBA power , and it was to be swapped with the engine at
Maclaren .As part of the instrumentation secession we are tasked with all GTA sensing
and control equipment. We facilitated the removal of all sensing equipment up to
terminal block level on the Avon side. After the engine was swapped we reconnected
the thermocouples (k) back onto the terminal block. Before the engine could be run , a
compressor wash was performed in which a mixture (1:3) of degreaser and distilled
water are sprayed into the air intake of the Avon engine while a dry crunk is in progress,
this is done to facilitate the cleaning of the seventeen (17) compressor chambers of the
Avon engine.
When the Avon was run for the first time the plant tripped on an “EGT failure” which
means that the PLC (programmable logic controller) was reading abnormal readings
from the thermocouples, after investigation it was revealed that:
1. The polarity of the thermocouples had been reversed.
2. The thermocouples on the Avon engine harness had been wrongly wired and
there wiring did not correspond with PLC and HMI (Human Machine Interface)
configuration.
After resolving the thermocouple problem the plant was run but it tripped due to a low
pressure on the fuel system, which brought insight to problems concerning the Unloader
on the Posi flow pump. The Unloader is a solenoid controlled valve on the Posi flow
pump which controls the pressure of the fuel while the Posi flow pump is an AC driven
pump which is controlled by varying the frequency. After many attempts to rectify the
low pressure problem it was decided that the Posi flow pump and Unloader be replaced.
After the replacement and carefully checking of all piping and rectification the plant then
become workable and run very smoothly.
This proved to be one of the most challenging tasks I had been involved in as it gave
me a broad understanding of problem detection and solving, and it helped me never to
over looking anything and to always question why things were being done no matter
who had undertaken the worked .
8. 5.2 Scrapping onPinionGearBoxBearingatMaclarenGTA siteinluanshya
System Control had reported that when they run Maclaren GTA site it would trip on
“high temperature on the Gearbox pinion bearing”. There were two possible causes to
this problem:
1. An Instrumentation problem in that the thermocouples were faulty.
2. A mechanical problem in that there was excess friction between the pinion and
the bearing or the alignment of the pinion had shifted.
We first began by removing the pinion bearing and there associated thermocouples. A
thermocouple is a temperature transducor which is formed when to metals or alloys are
joined to from a junction. When this junction is exposed to a temperature change a
milivolt is induced in the conductors the millivolt is converted to a current which is
interpreted by the programmable logic controller as a temperature, the thermocouples
employed by Copperbelt energy corporation are TYPE K meaning it is constructed from
chromel {90 percent nickel and 10 percent chromium} and alumel) (Alumel consisting of
95% nickel, 2% manganese, 2% aluminum and 1% silicon)
After checking the thermocouples with use of the Process Calibrator and the Heater
Block it was confirmed that the thermocouples were in perfect working order. The pinion
bearing was then scrapped, in which a layer of the bearing was scrapped off to reduce
the friction between the pinion and the bearing, after a desired works man-ship was
achieved the bearing and thermocouples were placed back.
The plant was run but it again failed on a “high temperature on the Gearbox pinion
bearing”. It was resolved that the further investigation be carried out. The works of the
day allowed me to understand the workings of thermocouples, compensation cables
and scrapping.
5.3 CheckingofexciterdiodeassemblyonLuano GTA1inChingola
The changing of the clutch on Luano GTA 1 provided the unique opportunity for
extraordinary works which can not be carried out during routine or preventive maintance
to be undertaken due to the timely timeframe of the job. I had the privilege of working
with the Electrical secession of the department. We opened the Exciter to expose the
Diode rectifier assembly. The diodes are used to provide a rectified Dc voltage to the
Generator field windings. On inspection of the diodes it was apparent that most of the
diodes were blown but they could not be replaced due to the lack of spares as the
model of diodes was no longer manufactured .The works of the day helped me to
understand how the Generator works, its parts (Permanent Magnet Exciter, Automatic
Voltage Regulator, Main Exciter Field, Main Exciter Armature, Diode Assembly Rectifier
, Field Discharge Resistor , Generator Field windings, Neutral Earth Switch and the
9. Generator Windings)and how it is controlled through feedback to the Automatic Voltage
Regulator. The Permanent Magnet Exciter is a DC generator which provides the
Automatic Voltage Regulator with a DC voltage which it controls the amount it sends to
the Main Exciter Field windings depending on the output feedback it receives from the
Voltage Transformers. The Main Exciter Armature is star wound with its output feed to
the Rectifier Assembly which is in parallel with the Field Discharge Resistor and the
Generator Field. Luano GTA 1 is capable of outputting 11000 Volts at 20 Mega Watts.
5.4 Theinvestigationoffaultyfireprotectionsystems(TYCO)
The recently completed Bancroft Central Substation had been equipped with a state of
the art fire detection and protection system (TYCO).The system is state of the art in that
all components on the system are addressable which eliminates the need of a
‘DOUBLE NKOCK’ from two separate Zones to confirm a fire. The works had been
done by a Contractor and before he could hand over the equipment it is protocol that
the completed works be examined and observed for a period of time. During the time of
observation the fire detection and prevention system suffered major faults from standby
battery faults, detection sensor faults to the damaged Control Unit Faults. All the
problems were rectified and were necessary modules were replaced.
Fire protection systems are employed to detect and extinguish fires or excessive heat
so that minimal damage can occur to equipment. Regardless of the complexity all fire
detection and prevention systems will consist of the four (4) main components which
include the Detectors, Control Unit, Warning Devices and the Extinguishing Unit.
The Control Unit is the heart of the system which is in charge off all the sub units/
modules basically the system works on the principle of LOGIC GATES with the AND
Gate at the heart of the system in order to obtain an output. Warning Devices are used
to indicate the presence of a fire, extinguishant realsed or the state of the system these
include sirens, beacons, bells etc. Manual Call Points are used to manually order the
control unit to perform a certain function or task. Extingushants are used to put out fires
by making the environment unfavorable for combustion this is achieved by the use of
various chemicals or gases depending on the equipment or apparatus being
considered. The Detectors are the sensing components of the system which translate a
fire condition into an electrical signal there are mainly three types these include Smoke
Detectors (optical or ionization), Heat Detectors (Rate of rise detectors or Fixed
temperature heat detectors) and Hybrid Multisensory Detectors, but it is common to find
Linear Heat detectors, Flame Detectors, Beam detectors and Aspiration detectors in
special application.
10. Working on the TYCO fire protection system help me understand the ins and outs of fire
protection and prevention systems and how they can be applied to insure the safety and
wellbeing of the of the workforce and equipment.
5.5 Theremoval ofthe proximitysensorsandthermocouplesontheclutchassemblyon
Luano GTA1
During the clutch removal on Luano GTA1 it was convient that the Proximity Sensor and
clutch Thermocouples be removed to lever the Mechanical Secession with adequate
room they require in removing the clutch i was privileged to help undertake this task
were I worked under the watchful eye of Mr. Montifort Nzima.
The Proximity Sensors is a type of switch which works with the aid of induction, it sends
a signal wheater the clutch is engaged or not.
The works of the day helped me understand the practicality of proximity sensors and
their operation.
5.6 MPU faultdiagnosticsatBancroftGTAsitein Chililabombwe
It had become common for Bancroft GTA 2 PLC to flag an MPU (magnetic pickup unit)
fault, and thus we were tasked to finding a permanent solution to the problem. The MPU
is a DC generator coupled on the turbine shaft which sends an electrical pulse after
every revolution these pulses are converted into electrical signals by the MPU card and
translated into Revolutions per Minute which represent the running speed of the Avon
engine and turbine.
After inspection of the MPU Card it was found to be in good working condition, the
problem was suspected to be in the Field Lines which were coming under attack from
spurious currents. A Field Termination Resistor and Capacitor were added at the end of
the field lines, the resistor and capacitor helps in minimizing the amount of current
flowing to the MPU Card as they act as a filter.
The works of the day helped me to understand and appreciate the MPU on the GTA,
shielding techniques of transmission lines and filters.
11. 5.7 PreventiveandRoutineMaintenance
Preventive maintenance involved the checking of GTA instruments and
transducers to see if the readings or indications the display or output collaret with
predefined values, the values are recorded but no corrections are made to the
instrument or transducer.
Routine maintenance involved having the GTA isolated in order for recalibration ,
repairs to components of the GTA these may include, transducers, instruments
,PLC components etc
5.8 Meetingsandpresentations
It was order to attend daily departmental meetings at 08 hours in which works of the
previous and current day were discussed and works of the presented day were issued.
The meetings helped me gain confidence in public speaking and how to conduct myself
.
13. Photos (top left to right) improving my knowledge on the use of an oscilloscope and
signal generator, gathering information during a Preventive maintenance at Luano GTA
site, learning to use the PLC simulator in the instrumentation Workshop at CSS, Avon
Gas Generator at Maclaren during the Avon swap, Luano GTA1 during the clutch
removal, working on the TYCO fire system control unit in the instrumentation workshop
at CSS
14. 7.0 Experience Gained
This placement provided an invaluable experience in witnessing the sort of work
performed by professional engineers in the Power Industry. Throughout the 12 weeks,
the importance of team work in achieving project/task goals was continually reiterated to
me both in the projects I was involved in, and by witnessing the work practices of my
colleagues. Part of this teamwork involves fully utilizing the company’s personal /
material resources in order to minimize the work required to achieve an acceptable
outcome.
An additional key point I picked up upon during my employment was the importance of
safety. This avoids the unfortunate situation of incurring injury to ones self, workmates
or machinery.
The position gave an insight into the office environment and provided an opportunity for
me to implement the engineering knowledge and skills acquired throughout my course
on real world problems.
15. 8.0 Conclusion
During my twelve weeks at Copperbelt Energy Corporation I feel that I have gained a
valuable learning experience. I have a developed a better understanding of the issues
paramount to Power Engineering and have become competent in a variety of tools /
techniques widely implemented by electricity distributors. The tasks I have performed
have re-enforced existing knowledge while forcing additional learning in a number of
areas.
I have thoroughly enjoyed the position and the people I have worked alongside for the
best part of three months. I’d like to thank the Copperbelt Energy Corporation, and Miss
Masozi Mhango, for providing me with such an opportunity.
