bosa theophilus ntshole report
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7/31/2015
WORK PLACE: DEBSWANA JWANENG MINE, EM 15
UNIVERSITY OF BOTSWANA
FACULTY OF ENGINEERING AND TECHNOLOGY
BACHELOR OF ELECTRICAL AND ELECTRONIC ENGINEERING (BENGE)
NATIONAL ID: 258018116
STUDENT ID: 201301848 | BOSA THEOPHILUS NTSHOLE
DEBSWANA
JWANENG
MINE MINING PROFICIENCIES
STATEMENT OF ORIGINALITY This report contains pure information about Debswana Jwaneng mine in the Engineering Department
of EM 15. An extension of associated information was found from other sources to aid in compiling
all the findings for this report.
ACKNOWLEDGEMENTS I would like to send my sincere gratitude to Mr Ernest Segale and Mr Njabulo Gilika for accepting my
request to be attached in Debswana Jwaneng Mine. I thank EM 15 section maintenance Engineer Mr
Kabo Ngwanaamotho for accepting me in his section and giving me specific objectives for my
research project on his section. I thank EM 15 section foreman Mr Bojosi Tonkope for providing me
with all the resources I needed for my research project. I would also like to thank Mr Lee Dintwa,Mr
Osego Moonwa, Mr Bakang Pedro, Mr Tiroyaone Molelekedi,Mr Noah Khutsafalo and Mr Tshiamo
Keagakwa for proving all the help and understanding I needed for my research project, these blessed
men were always there to help. I would like to extend my gratitude to EM 15 team for always being
there at all times, exposing me to many different working environments concerned with EM 15
section for me to acquire some knowledge.
Table of Contents
STATEMENT OF ORIGINALITY ........................................................................................................ 2
ACKNOWLEDGEMENTS .................................................................................................................... 2
LIST OF ABBREVIATIONS ................................................................................................................. 5
SYNOPSIS .............................................................................................................................................. 6
INTRODUCTION .................................................................................................................................. 7
DEBSWANA JWANENG MINE SAFETY STANDARDS ................................................................. 8
DEBSWANA JWANENG MINE’S COMMON GOAL OF ZERO HARM ..................................... 8
SHE POLICY...................................................................................................................................... 8
GENERAL ELECTRICAL SAFETY .................................................................................................... 9
ACTIVITIES CARRIED OUT AT EM 15 ............................................................................................. 9
SOIL RESISTIVITY TESTING ......................................................................................................... 9
Driven Rod Method .......................................................................................................................... 10
FAULT FINDING ON AN HT CABLE .............................................................................................. 10
COMMON HV CABLE FAULTS ................................................................................................... 11
1. CONDUCTOR PARALLEL FAULT .................................................................................. 11
2. SHIELD PARALLEL FAULT ............................................................................................. 11
3. FLASHING PARALLEL FAULT ........................................................................................ 11
4. SERIAL FAULT (OPEN, INTERRUPT) ............................................................................. 12
5. EARTH FAULTS (SHEATH FAULTS) .............................................................................. 12
DEBSWANA JWANENG MINE RETICULATION SYSTEM(MINING ONLY) ............................ 13
INTERPRETATION OF DEBSWANA JWANENG MINE’S MINING RETICULATION SYSTEM
.............................................................................................................................................................. 14
PROCESSES INVOLVED IN THE SAFE MAINTENANCE OF MINING RETICULATION
SYTEM ................................................................................................................................................. 14
1. PREPARATION OF THE JSA............................................................................................. 14
2. OBTAINING OF JOB TICKETS OR TAF .......................................................................... 14
3. PERMIT TO WORK ............................................................................................................ 14
4. IDENTIFICATION OF POWER SOURCE ......................................................................... 14
5. ISOLATION ......................................................................................................................... 15
6. DE-ENERGISING ................................................................................................................ 15
7. EARTHING .......................................................................................................................... 15
8. ISOLTATION TAGGING .................................................................................................... 15
9. LOCKING OUT ................................................................................................................... 15
10. DISSIPATION AND RESTRANING ENERGY SOURCES .......................................... 15
11. VERIFCATIONS OF EFFECTIVENESS OF THE ENERGY CONTROLS .................. 15
12. CARRYING OUT THE WORK ....................................................................................... 15
13. HANDING OVER OF AN ISOLATED SYSTEM .......................................................... 15
RECOMMENDATIONS ABOUT WAY FORWARD WITH RESPECT TO EM 15 WORPLACE
ISSUES ................................................................................................................................................. 16
CONCLUSIONS................................................................................................................................... 17
LIST OF ABBREVIATIONS EM 15- Engineering Mining 15
MQWMA- Mines Quarries Works and Machinery Acts
MCC- Motor Control Centre
BPC- Botswana Power Corporation
HT-High Tension
HV- High Voltage
KV-Kilovolts
TAF- Tagout Authorisation Form
SYNOPSIS This research project was basically about mining adroitness. It was based specifically on interpreting
Jwaneng Mine’s Safety Standards. This project was also based on the general familiarisation of the
legal requirements in the mine with respect to Electrical and Mines Quarries Works And Machinery
Acts(MQWMA) thus the understanding of Mines Quarries Works and Machinery Acts and the
general safety more especially 13.2 provisions. Also the understanding of processes that are involved
in the safe maintenance of the mining reticulation system was put into consideration not forgetting the
schematic of a diamond deposit and layout of mining operations interpretations.
INTRODUCTION I am a student at University of Botswana who is currently doing second year on the programme of
Electrical and Electronic Engineering. I was offered a place in Debswana Jwaneng Mine for my
industrial training (ITB 200) as part of my assessment on progression of my studies. My industrial
training at Debswana Jwaneng Mine commenced on the 22nd
June 2015 and terminated on the 31st
July
2015. I was attached at EM 15 section which is mainly concerned with the safe maintenance of the
Jwaneng mine reticulation system. EM 15 workshop is located on the medium risk area of Jwaneng
mine known as the blue area, next to EM 13 and opposite ET 13 workshops. Some of EM 15 duties
include switching and isolation of electrically driven machinery mostly used at the mining pit, cable
repairing, earth resistance testing (also known as earth resistivity testing), substation inspections and
repairs, borehole inspections and maintenances, ground cable detections.
It was so important for me to be attached on EM 15 for my Industrial Training because EM 15 duties
helped me with grasping the practical and technical aspects of daily tasks that were performed
throughout my attachment period and also to improve myself on attributes that would make me a
professional engineer, develop such attitude to work with efficiency, being so responsible, being able
to communicate and being able to work in a team.
DEBSWANA JWANENG MINE SAFETY STANDARDS Debswana Jwaneng mine’s main focus is on safety, employee wellness, training and development.
Jwaneng mine applies productive, efficient and cost effective practices that have successfully
positioned them as a globally recognized, safety oriented and high performance organization in the
mining sector. Safety is a strategic priority at Jwaneng mine and the company has meticulous
standards and processes in place to prevent injuries.
All operations run initiatives to promote a common culture of Zero Harm and deploy processes to
facilitate hasty reporting and investigation of every incident to identify root causes, initiate
counteractive action, and to disseminate lessons learned. Below are the initiatives that were raised to
improve Jwaneng Mine’s safety standards;
DEBSWANA JWANENG MINE’S COMMON GOAL OF ZERO HARM Jwaneng mine’s common goal is to activate Zero Harm to employees, the environment, the broader
community, and to our product. This can be achieved through the effective management of safety and
health risks at all operations.
SHE POLICY It is one of the core values of Debswana Diamond Companies including Jwaneng Mine to conduct all
its operations in a manner that will minimize impact on the environment and uphold the safety and
health of our employees. Jwaneng mine therefore committed itself to the following
Conservation of all natural recourses like diamonds and other recourses as well
Continually improve employees’ safety, occupational health and environmental performance
Comply with all applicable laws, regulations and other commitments
Prevent work-related diseases, injuries and damages to property
Prevent pollution of the environment.
Treat the protection of safety, occupational health and the environment as the responsibility of
everyone working at Debswana Jwaneng mine.
The commitments of Debswana Jwaneng Mine stated above will be met by:
Integrating safety, occupational health and environmental considerations into all aspects of
the business process
Implementing formal safety, occupational health and environmental management
programmes
Providing appropriate training to all employees and contractors
Assigning responsibility for the coordination of the safety, occupational health and
environmental management programmes to appropriately skilled and experienced managers
Providing adequate resources and facilities to implement the requirements of this policy
Proactively engaging with the government, communities and other stakeholders on matters
related to safety, occupational health and the environment
Making public the company`s safety, occupational health and environmental policy and
performance.
GENERAL ELECTRICAL SAFETY According to the Mines Quarries Works and Machinery Acts (MQWMA), an electrical engineer
should appoint as many competent people to be subordinate engineers, electricians in charge or
electricians because their competency will maximize safety when carrying out electrical installations,
electrical examinations, testing and maintenance of electrical equipment. The following necessities
(13.2 provisions) should be in concurrence with the appointees competencies or should be able to
guide them;
All electrical apparatus shall be under the general charge of the electrical engineer
Every inferior engineer shall, to an extent at which shall be clearly definite in his/her letter of
appointment, have the same errands under these set of laws as the electrical engineer in
general charge.
Provided that the selection of such persons shall not be taken to replace the electrical
engineer appointed in agreement with sub regulations of any personal responsibility
under these regulations’.
The manger shall not assign himself as a competent person under the terms of sub regulation
except with the written acquiescence of the electrical engineer.
SUB PROVISION OF INTEREST
Provision 13.1- states that at every mine, quarry or works at which electricity is used and at a total
rating of all electrical apparatus installed threat exceeds 750KW, there shall be an appointed manager
in writing a competent person to be an electrical engineer.
ACTIVITIES CARRIED OUT AT EM 15
SOIL RESISTIVITY TESTING It is well known that the resistance of an earth electrode is heavily influenced by the resistivity of the
soil in which it is driven and as such, soil resistivity measurements are an important parameter when
designing earthing installations. Knowledge of the soil resistivity at the intended site like the mine
magazine, and how this varies with parameters such as moisture content, temperature and depth,
provides a valuable insight into how the desired earth resistance value can be achieved and maintained
over the life of the installation with the minimum cost and effort.
The purpose of resistivity testing is to obtain a set of readings which may be interpreted to yield an
equivalent model for the electrical performance of the earth, as seen by the particular earthing system.
However, the results may be incorrect or ambiguous if adequate investigation is not made prior to the
test or the test is not correctly undertaken. To overcome these problems, the following data gathering
and testing guidelines are suggested.
Figure 1
Driven Rod Method The driven rod method (or Three Pin or Fall-of-Potential Method) is normally suitable for use in
circumstances such as transmission line structure earths, or areas of difficult terrain, because of: the
shallow penetration that can be achieved in practical situations, the very localised measurement area,
and the inaccuracies encountered in two layer soil conditions.
FAULT FINDING ON AN HT CABLE Here in EM 15 when fault finding on an HT cable, a device called a thumper is used to identify a fault
on an HV cable. A thumper injects an alternating current voltage on a phase conductor that is being
tested, if there is a fault on that phase conductor there will be a pop sound produced where that fault is
as a sign of an open circuit. Below is a picture of a thumper.
Figure 2
COMMON HV CABLE FAULTS
1. CONDUCTOR PARALLEL FAULT
Connection between two or more conductors. The insulation resistance value of the fault can be
between 0 Ohms (low resistivity) or several M Ohms (high resistivity).Below is the figure showing a
conductor parallel fault:
Figure 3
2. SHIELD PARALLEL FAULT
Connection between Conductor and shield or Conductor/Conductor and shield. The insulation
resistance value of the fault can be between 0 Ohms (low resistivity) or several M Ohms (high
resistivity). Experience has shown that most faults are in this category. The diagram for shield parallel
fault is below:
Figure 4
3. FLASHING PARALLEL FAULT
Very high resistance fault. The cable can be charged. The flashover happens typically at some kV and
is very often located in Joints. The cable acts comparable to an arc gap, where the distance between
the electrodes determines the voltage. The insulation resistance of this fault is typically infinite up to
the breakdown voltage. The below figure illustrates what happens when there is a flashing parallel
fault.
Figure 5
4. SERIAL FAULT (OPEN, INTERRUPT)
Faults of this type can be very high resistive up to infinite (complete cut). Very often these type of
faults are a combination of serial and parallel insulation resistances. The reason for this being a
complete cut of the cable, or it is pulled out of the joint, which interrupts everything, but also permits
flashovers in all possible variations. If the conductor is partially burned off (Aluminium) we speak of
longitudinal faults.
Figure 6
5. EARTH FAULTS (SHEATH FAULTS)
Faults between the metallic shield and surrounding soil in case of plastic insulated Cables. Faults
between the Conductor and surrounding soil on LV and plastic insulated cables. Especially for these
types of faults the highest precaution must be taken when using high voltage, this is of greatest
importance, since the voltage discharges directly to earth. Resulting an increased potential danger to
man and animal. Below is the diagram illustration of that fault;
Figure 7
After fault finding by thumping, an HV cable is then skinned where the fault is. It should be skinned
in such a way that there is allowance to fully scan through the phases and also to work easily when
repairing the cable. There are a number of tapes that are used in cable repairing, the likes of insulation
tapes, heat resistant tapes, semi conductors. All these tapes have purposes, insulation tapes are for
voltage resistivity and potential separation of conductors. The purpose of semi-conducting tapes is for
the prevention of partial discharges (PD) and high electrical fields inside the cable after repairing.
Semi conducting layers soften the electrical field which builds up around each single conductor strand
and avoids discharge which may occur due to increased electrical fields which may cause damage to
the cable. Heat resistance tape is mainly used for protecting the cable phases/conductors from burning
after the joint has been put in an oven. Below is a picture illustration of a well joined cable covered
with earth tapes on each phase:
Figure 8
DEBSWANA JWANENG MINE RETICULATION SYSTEM(MINING ONLY)
Figure 9
INTERPRETATION OF DEBSWANA JWANENG MINE’S MINING
RETICULATION SYSTEM Debswana Jwaneng mine gets its electricity from Botswana power Corporation. Electricity from BPC
arrives directly at Debswana Jwaneng mine’s green area (low risk area) substation having voltage of
132KV which will then be stepped down to 33KV. The 33KV that has been stepped down at the
substation will then travel to the splitter bin which splits the 33KV into two routes that will go all
around the mining pit. Some stepping down is there also at the splitter bin, 33KV is stepped down to
6.6KV which will then be transferred to the 6.6KV splitter bin which is located exactly opposite the
33KV splitter bin.
33KV having routed in two ways by the 33KV splitter bin will then reach the yards. There are only
three yards that are concerned with mining reticulation that are yard 5, yard 2 and yard 7. Yard 5 is
currently offline because of some maintenance going on there. Yard two steps down the 33KV from
the splitter bin to 6.6KV is fed to the breaker skids 15, 18 and 17 but right now breaker skid 15 which
fed the MCC is now offline. Breaker skid 18 which receives stepped down voltage 33KV/6.6KV from
yard 2 feeds shovel 205 6.6KV and drill 322 6.6KV. On the other hand the 6.6KV that was stepped
down at yard two also feeds breaker skid 17 which feeds shovel 209 6.6KV, drill 323 6.6 KV and
shovel 213 6.6 KV.
Also the 33KV from the splitter bin reaches yard 7 which steps the 33KV down to 6.6KV. The 6.6KV
from yard 7 is fed to the repeater station, the tailor dam, breaker skid 14 which replaced breaker skid
15 and also the goose neck is fed by yard 7.
PROCESSES INVOLVED IN THE SAFE MAINTENANCE OF MINING
RETICULATION SYTEM
1. PREPARATION OF THE JSA
The JSA is the job risk assessment book. This is where one records possible injuries that one can get
on his working environment and just in general. It also requires one to fill in the prevention
techniques, persons involved in the task and supervisor’s signature.
2. OBTAINING OF JOB TICKETS OR TAF
All work shall be accompanied by either job ticket/card for safe maintenance and service work or Tag
Authorisation Form for construction or project work.
3. PERMIT TO WORK
A permit to work is a piece of form of written declaration signed and given by the person legally
responsible for the plant to the person in charge of work to be carried out on machinery or equipment
that has been isolated, locked out and made safe.
4. IDENTIFICATION OF POWER SOURCE
An authorised worker/competent person intending to work on a plant shall personally identify all
sources of energy, coming into the plant because energy fed into the plant may have more than the
one in the source and supply line.
5. ISOLATION
Isolation is the method of blocking liquid gas, electric current or other stored energy so as to ensure
harmless access for check-ups and maintenance. Isolation provides confident protection and is
achieved by the use of locking device.
6. DE-ENERGISING
To de-energise is to remove effectively all potential sources of energy from the electrically driven
item, system process or area.
7. EARTHING
To earth means to connect general mass of earth in such a manner to make sure that at all times the
instant discharge of electrical energy without danger.
8. ISOLTATION TAGGING
A tag is placed on an isolation point by the person who is responsible that the isolation requirements
for the task have been met. Putting the isolation tag also prohibits all use, operation or start-up of
plant or equipment. The person who puts the tag is the same person who removes it from an isolated
area.
9. LOCKING OUT
Locking out mean to put a personal lock on an equipment in such a way that it is impossible to
connect, switch on or start and energising the equipment without removing the lock.
10. DISSIPATION AND RESTRANING ENERGY SOURCES
After tags/locks are applied to energy isolating devices, relieving disconnections, restraining should
be done making safe that all the potentially hazardous stored or residual energy.
11. VERIFCATIONS OF EFFECTIVENESS OF THE ENERGY CONTROLS
The competent person shall personally verify the effectiveness of the isolation, dissipation and
restraint of energy sources.
12. CARRYING OUT THE WORK
If the verifications show effective isolation then the work (maintenance and inspections) should be
carried out with no caution.
All people shall be prohibited from attempting to operate energy isolation.
After the work is being done, authorised workers should remove his/her locks and tags and clear
his/her tools (housekeeping). Before removing last isolation tags and locks, a competent person
involved should check if the plant is clear of tools.
13. HANDING OVER OF AN ISOLATED SYSTEM
The competent person should leave the work and hand over to the work relief person. Their lockouts
should be changed as part of their handing over.
RECOMMENDATIONS ABOUT WAY FORWARD WITH RESPECT TO EM
15 WORPLACE ISSUES Even though I had a very wonderful time here in EM 15 exploring, learning and adopting/appreciating
how EM 15 workers operate, there are some few suggestions I would like to add that I believe they
would wake EM 15’s daily works easier. I strongly suggest that EM 15 workers should at all times
wear switching suits when called out for switching or maintenance and also make use of remote
controlling switching to be at lower chances of injuries when switching.
I would also like to add suggestions on cable towers that are EM 15’s duty in terms of their making
and maintenance. I suggest that these cable towers should be fitted with hydraulic jacks of working
loads of 50 tonnes at the top of each so that the tower can be elevated and lowered to cater for the
930E trucks which are currently a hazard when passing under cable towers, the cable towers are of
less height as compared to those huge trucks. It would really benefit EM 15, not being called time and
again for cable damages due to these trucks.
Another suggestion is that the breaker skid panels should alternate with their respective feeder cables
connected. We find that the auxiliary transformer panel does not have its feeder cable that’s
alternating with it, electricity for auxiliary transformer just flows from the income to the transformer
which is in the breaker skid itself. This is hazardous to someone who is not aware of such set up. So I
suggest that ABB as the main supplier could make sure that the auxiliary transformer panel is made
different (could be in colour) in order for the person who will be doing the switching to keep
reminded that the feeder cable for auxiliary transformer is not where other feeder cable are.
I also recommend that the feeder cables (machine cables) that are leaving the breaker skid should be
labelled for effectiveness. I strongly suggest that the cable heads and slots that are made of aluminium
should be changed to rubber because these aluminium ones break off easily. EM15 should start
ordering rubber heads and slots instead of aluminium ones.
CONCLUSIONS Debswana Jwaneng Mine’s reticulation system was generated with such extreme intelligence, we find
it that the splitter bins split or route the electricity in two ways to make sure that there is always
electricity on the mine. The bus section is there in the splitter bins to make sure that whenever there is
a fault on the other side of the bus section, say a transmission line, a bus section will be closed to feed
the other one. There is no how Debswana Jwaneng Mine could black out because EM 15 is there to
make sure that there is always electricity in the mine by carrying out inspections and maintenances.
Each and every electrician and artesian in EM15 knows the interpretation of the mine’s mining
reticulation system, as EM 15 it is mandatory for us to make sure that all the sub stations are up to
date in terms of their maintenance and cleanliness and also ensure that the mining pit is all powered
up.
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