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.