Engineering Practice Report

Name: Paul Soko Student Number: 08107917 School: Engineering

Programme: Electrical & Electronic Engineering, 3rd

Year Employer: Copperbelt Energy Corporation Period: 20th January to 30th April 2011

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)

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

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.

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 EMERGENCY POWER 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

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

5.0 Tasks Performed & Duties During my 14 weeks at Copperbelt Energy Corporation, I helped in undertaking the

following tasks:

5.1 The Engine Swap at Maclaren GTA site in Luanshya

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 .

5.2 Scrapping on Pinion Gear Box Bearing at Maclaren GTA site in luanshya

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 Checking of exciter diode assembly on Luano GTA1 in Chingola

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

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 The investigation of faulty fire protection systems (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.

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 The removal of the proximity sensors and thermocouples on the clutch assembly on

Luano GTA 1

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 fault diagnostics at Bancroft GTA site in 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.

5.7 Preventive and Routine Maintenance

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 Meetings and presentations

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

.

6.0 Photos

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

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.

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.