INTERVIEW QUESTIONS

1. Purpose of batteries and auxiliary txf in a s/s.

 Batteries are used as emergency back-up supply when the s/s loses ac
 Batteries are used for supplying the protection relays, communication
panels, tap changer panel
 Charging coils after operation
 Supplying power for alarms and annunciations
 Auxiliary txf is used for s/s lighting, ac supply for general s/s works i.e.
welding, filter plant
 Battery charging
 Txf controls i.e. fan and motor operation, tap changing

2. Maintenance you carry on batteries.

 First aerate i.e. open all windows and doors and do not use a naked flame
 Always wear correct protective clothing i.e. acid proof work suit
 Test terminal voltage with charger on and record
 Remove/ isolate battery bank, wait for 5 minutes and test terminal voltage
and record
 Test individual cells and record
 Inspect individual cells for damage and remove sulphation formed on
battery terminals, clean the terminals and apply Vaseline on the terminals
 Check electrolyte level and first check using a hygrometer for the
determination of whether level of acidity is low or high, if low add acid
and if high add distilled water
 General battery room housekeeping
 Measure the terminal voltage from battery charger
 Measure the now voltage of the battery bank and individual cells after
maintenance before connecting to the charger and record
 Switch on the charger.
3. Line protection of a 33kv line.
 SEF (Sensitive Earth fault) or known as common bar protection which
protects line when a high resistance fault occurs i.e. live conductor falls on
rocky area and the breaker fails to trip or does not sense this as a fault
condition.
 EF (Earth Faults) when a live conductor comes into contact with earth
wire or falls to ground or when a tree falls on the line
 O/C (Overcurrent) when a phase to phase fault occurs and an overcurrent
condition arises and hence large fault currents flows back to the source
 ASC (Arc Suppression Coil) back up protection which is protection when
a fdr CB fails to trip and hence an inductance is introduced in form of a

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 coil which then counters the capacitive fault current and thereby trips the
whole s/s.
4. What do you do on commissioning a 10MVA txf?
 Commissioning is all the checks and tests carried out on plant and
equipment before being put to service for the first time.
 Checks
(a) Equipment spec and data ratings, operating voltages and frequency,
mode of operation must conform to requirements and suit the intended
function
(b) Electrical connection integrity
(c) Good workmanship i.e. work must be neat
(d) Wiring checks must be carried out to prevent maloperation of
equipment
 CT tests; current ratio, IR, magnetization curve and polarity tests done
 VT tests; IR, voltage ratio and polarity
 Power txf tests; TTR, IR, winding resistance, diverter continuity, ancillary
instruments (oil and winding, main tank, buccholz gas and surge, main
tank overpressure), manual and automatic cooler control, neutral earth
resistance
 Txf oil tests; dielectric, crackle and acidity
 Tests on cb and isolator; ducter tests, IR, timing tests and interlocking
 Dc supplies; on battery charger, test the charging modes output and
alarms. On battery bank cells test voltage, specific gravity, acidity, and
external resistance
 Relay tests; protection relays and voltage regulating relay tests
 Stability tests; on unit protection schemes like differential and REF
 Measurands; txf tap position indication, local, remote and supervisory,
alarms and indications, controls of CB’s and isolators local and remote
and supervisory must also be tested and confirmed
 Test LV and HV CB intertrip tests.
 On load tests are carried out after energization and loading of the txf
 Commissioning follow up must be done if applicable
 Commissioning schematics must be submitted to the drawing office for
production of the built schematic
5. How can an artisan be a cost to an organization?
 Incompetence, recklessness, abuse of company property which then
dilutes company profits
 Arriving at fault sites late prolonging off time
 Accepting bribes on disconnections

6. When an individual is involved in an accident, how does it cost the company?

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  The revenue lost in down time, investigating and then restoring i.e. buying new
plant and machinery to replace the burnt one
 Revenue lost in compensation, court hearings and fines
7. How does late fault attendance cost the company?
 Loss of revenue when customers are off for a long time
 Loss of customers who opt to use other alternatives for power
 Loss of customer confidence hence loss of future revenue
8. How do you deal with hostile workers?
 Stern reprimand
 If fails workers’ committee for amicable solution
 Approach Foreperson
 Report to manager and call for a hearing
9. Txf protection on a 200KVA txf
 Arcing horn gap protection
 Surge arrestors
 Lv mcb
 Fuse links
10. Procedure when you are changing an oil cb and putting on as sf6.

11. Why choose an sf6 cb over an oil?
 SF6 gas is colorless, odorless, non-toxic and does not pollute the
environment.
 SF6 does not support combustion as compared to oil which after a number
of operation it loses its insulating properties
 Oil cb’s are being phased out as they are bulky and dirty to maintain
12. Procedure when working on high voltage equipment.
 Rule 14 of the safety rules book that no work is done on high voltage plant
and equipment unless the equipment has been made
 Dead – steps taken to de-energize the plant and equipment to be worked
on i.e. open of cb’s
 Isolated – opening of isolators, hot line taps, links, and locked off from all
points of supply which can make equipment live i.e. from all auxiliary
supplies
 Earthed – application of approved earth sets to safely discharge at all
times
 Screened- use of barricades and screens to minimize accidents
 Released – released for work with the appropriate safety documents
13. History of yourself concerning the job.
 So far underwent apprenticeship training for 4 years and was working
under the tutelage of experienced artisans, technicians and foreperson and
has gained substantial knowledge in the field raring to apply myself on the
job

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14. Why do you think you are the best candidate?
 Because I am the best, I have never played second fiddle in what I do
professionally with my colleagues and they know it too, however what
makes me the ideal candidate besides my superior knowledge is that I can
recognize contributions from those around further improving me as a team
player as well as my output.
15. Txf protection.
16. How do you treat contractors?
 Contractors contracted to do works on ZESA plant and equipment are
governed by the Safety Rules book (grey) of 1998, to which I will first
explain the procedures for work i.e. the relevant qualifications have been
met and the age of the working party as well as check if they have proper
T&E
 Explanation of what is required of the contractor in line with the works
whether he/she knows the nature of work
17. Grievance handling procedure.
18. How do you treat materials booked from stores that were not used or no longer needed?
19. Depot of your choice.
20. Can overtime be minimized.
21. How do you reduce outages to customers?
22. Code of conduct, some values of the company, mission statement, grievance handling
procedure.
(a) Mission statement--- to bring convenience to our valued customers through
the provision of adequate safe, reliable electricity and related services at
competitive prices
(b) Core values---Teamwork, Safety, Efficiency, Commitment, Corporate
governance, Entrepreneurship
23. Safety documents used in ZESA, accident reporting procedure.
24. What is meant by floating neutral
25. What do you understand by cost cutting?
26. Difference between overcurrent and overload
27. Purpose of health and safety meetings
28. Types of maintenance; statutory, routine, fault, planned and preventative maintenance
29. Zimasset
30. Procedure of a new connection
31. What is switching
32. Prepayment meter fault finding
33. IRBM – Integrated Results Based Management systems
34. Fire-drill
35. Significance of autorecloser in our system
36. Identify yourself- qualifications etc.
37. Duties and responsibilities of an artisan
 Carry out fault meter change and meter change program

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  Pulling up to 2 spans of LV and HV lines
 Doing cable jointing on HV and LV reticulation
 Carry out maintenance on authority’s system in accordance with laid down
procedure
 Replacing faulty ACB, MCB and load limiters
 Receiving faults from controllers, updating them on the nature of faults
and job completion times
 Issuing working documents for personnel working on the authority’s
equipment for voltages up to and including 33kv in accordance with safety
regulations
 Carry out switching up to 33kv
 Carry out s/s and equipment inspections
 Knowledge of operational procedures and safety regulations
38. Cost cutting -----i) overtime (planning and maintenance)
ii) telephone charges (use of emails)
iii) fuel (use shorter routes)
iv) safe keeping of T&E

39. Demand side management – how do you save power for customers and ZESA
40. S/S construction 1MVA – main and b/up protection…NEF, WR, OT, BEF,
Differential protection
41. How do you motivate workers – delegate duties to artisan assistants, carrying job
appraisals, teamwork promotes unity thereby motivating one another
42. Ways of revenue protection.
43. As an electrician at ZESA how can you make sure the public is protected from the
dangers of electricity
44. Procedure when changing a pg clamp on a 33kv line
45. What kind of protection do you expect to find on a 5MVA txf?
 NEF
 LV BEF
 WT, OTT
 OLT
 Buchholz
46. Procedure for NPS
 Customer applies using an E22 form
 Site visit by cso
 Customer fills a notification of commencement of wiring form E62 this form
includes the particulars of installation i.e. new installation, supply required,
number of circuits
 Customer fills a notice to authority upon completion of wiring form E38 this form
requires the details of the contractor who wired the installation and the number of
circuits

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  Inspection is done by the authority and an E1 is filled
 A customer profile is then created using 3e and a quotation is then prepared and a
pjob number is generated which Is the reference number for the customer profile
used throughout, for a standard customer gets an email or has one printed after 14
days but if non-standard it has to go for costing and an ACE is done using NDM
 Customer pays the quotation fee or rather the connection fee
 CSMS (Customer Supplied Meter Scheme) the customer uses pjob number to
purchase meter and comes with the receipt
 Meter goes to stores
 SCSO assigns job to an electrician and he uses a WEO (Work Execution Order)
with details of job, and materials to be ordered at stores
 Connection is done and a WOMI, Meter card, LOA, pre-task risk assessment
form, alongside the WEO is handed back to foreperson
 Foreperson in tandem with commercial officer commissions the job in the system
for customer to register and start purchasing power
47. Tell us about ICS, DCS and NDM
48. Inspections done on an NPS
 Earthing i.e. all extraneous conductive parts, door, sinks, tapes
 Correct size of wiring cables used
 Correct size of circuit breakers
 Proper conduit bends, saddling, circuit tags, according to set standards
 Connection integrity
 Proper earth termination i.e. spikes
49. Inspections done on a prepaid meter
 Cover intact
 Condition of connections whether bypassed or not, or tightness
 Condition of ciu, inclusive of lcd, buttons etc.
 Terminal seal still intact
50. Advantages of prepaid over conventional
 Enhanced revenue collection
 Meter is user friendly
 Gives power to customers to control their consumption
 Technological advancement from conventional
 Intelligent i.e. able to detect and protect customers from very high and very low
voltages, loose connections i.e. floating neutrals
 Able to detect temper
 Light
 Easy to diagnose a fault
 Effective cost cutting tool i.e. reduce running cost of meter reading and billing
 Ease of doing business as no need to bill customers
 Control power consumption of customers through the use of tariffs

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  Save customers from unexpected high bill and
51. Why should ZESA have metering
 Billing
 Come up with maintenance programs for plant and equipment
 Capture what we generate and distribute
 Help us note losses
 Determine upgrades and downgrades of plant and equipment
52. Acts of misconduct
53. Pmt construction and maintenance
54. Line construction and maintenance
55. Cable sizes

56. Importance of NEC (National Employment Council)
57. Purpose of a breather on a txf
 Release gasses e.g. Sulphur, hydrogen produced in the txf to the atmosphere
 Allow fresh moisture free air to circulate within the txf
58. Importance of OSHE committee

59. Types of tests done on txf oil
 Acidity
 Crackle
 Dielectric test
 Dissolved gas

60. Types of faults

 Transient- fault clears on its own i.e. switching surges, tree branch falling on line
and clearing
 Permanent – fault fails to clear on its own
 Symmetrical- fault occurs on all phases or is similar on all 3 phases e.g. 3 phase
o/c and e/f
 Asymmetrical- fault occurs on 2 or one phase but not all 3
61. Pmt inspection
 Check oil leaks
 Condition of mcb
 Meter condition, condition of lt mains
 General s/s condition, including paintwork, undergrowth,
 Lightning arrestor condition
62. Uses of txf oil
 Insulating medium
 Coolant
 Breather
 Checking condition of txf winding

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  Temperature control in conjunction with CT, mercury switches and alcohol filled
capillaries
63. Cable fault location
 T&E required acoustic reflectometer, thumper (surge generator), ac generator,
extension cable, cable pre-locator, HT leads….
 Procedure
Nb know the rating of the equipment before testing i.e. the voltage, current, age,
length before injecting any current or pushing a voltage for the purpose of
testing and make sure earths are removed and everyone is clear from any plant
or equipment live or being tested…
 Step 1
Assess test equipment and test apparatus i.e. checking the condition and
connection integrity
 Step 2
Do an IR (insulation Resistance), this is done to check the faulted phase(s).

 Step 3
Use a fault pre-locator to check nature of fault whether it is an open or a short
circuit, the graph on the monitor will spike upwards for a short circuit and dip for
an open circuit, this also gives us a rough estimate of the position of the fault

 Step 4
Using a hi-pot thumper or a surge generator inject a surge impulse usually an
0.5seconds on the cable to the voltage level required or is applicable to the rating
and age of cable to avoid damaging it
 Step 5

With the surge generator still injecting a pulsating dc voltage, armed with an
acoustic cable reflectometer (listening set), using the monitor to follow the cable
which shows a pulsating magnetic field as this field is due to the field created by
the surge generator pulse and a corresponding arrow pointing in the direction of
the fault, then trace the cable up to a point where there is a thumping or knocking
sound as well as the arrow changes direction instantly and put a marker on that
point that is when the fault is located.

64. Procedure when working on an hv cable

 After isolation and earthing and fault has been located
 Issue LOA for exposing cable i.e. digging cable bay
 Cancel LOA and test for dead i.e. spike the cable if they are many at the point of
fault, or use a frequency generator set to detect the cable with a preset frequency
higher than the system 50Hz

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  Issue PTW for cut and open the cable for pressure test
 Cancel PTW and issue an SFT for pressure testing both ends as well as dead
phasing in
 Cancel SFT and issue PTW for joining the cable
 Cancel PTW and issue an SFT for pressure testing after joining
 Cancel SFT
 Get instructions to energize the cable
 Get instructions to do live phasing in
65. Operation of an AR in conjunction with a sectionaliser
 AR is an intelligent breaker able to sense and operate i.e. whenever a fault occurs
on the line, it can be a transient (tree falls on line and clears), overcurrent,
earthfault and SEF. A sectionaliser however is a switch which cannot operate on
its own and can only operate in the dead time of the AR. So an AR is put on the
line and in front of it a sectionaliser and for proper coordination of operation the
sectionaliser must be set at (n-1) counts of the AR, so if a fault occurs on the line
the sectionaliser senses but does not operate, the AR upstream senses the fault and
operates i.e. opens the contacts it is at this point that the sectionaliser opens its
contacts. When the AR recloses it energises the line the line voltage closes the
coil which closes and makes the contacts, if fault is still there it will repeat the
process until the sectionaliser has reached maximum set counts and locks out
66. Types of tariffs
 Domestic
 Commercial
 Street lighting
 Mining
 Agriculture
 Clinic and hospital
67. Types of leaves
 Occasional leave- 12 days per year, 3 max per month
 Vacational leave – 30 days per year
 Study leave – 12 days
 Special leave – 12 days
 Maternity leave – 90 days before and after giving birth
 Compassionate leave – 12 days
68. Acts of parliament which govern works conducted by ZESA
1. Electricity Act-----Relations between interconnected system, reporting
of accidents, controller in charge of loading, wayleave clearance,
safety clearances over road and rail.
2. Zimbabwe Labor Relations Act---Protection of employee rights to fair
labor standards, general offences and penalties
3. Factories and works act---machinery, and accidents. Inspection of
machinery, accident register and notification of accidents

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4. NSSA--- worker’s compensation act, worker’s health and safety act
5. SI 177 of 2018

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