Metering systems

1. ACKNOWLEDGEMENTS
My deepest gratitude and appreciation goes to the Harare Depot metering staff that made sure
that I got hands on appreciation of all aspects of metering. I would like to thank Mr. Chisina,
Mr. P. Mfiri, Mr Nyoka, Mr Mutambayashata, Mr Mushambi, Mrs Tsomondo and all the
others.

2. EXECUTIVE SUMMARY
This report outlines the activities I appreciated whilst attached to Harare Meter Test depot.
The metering department is the cash cow of ZETDC.
Of special mention is the replacement of the conventional electromechanical meters with
modern digital prepaid meters. This move is meant to increase revenue collection and
eliminate non-payment of bills mainly by domestic customers. To date, the utility is owed
about US$500million by customers. Use of prepaid meters means customers can better
manage their electricity consumption and contribute to energy efficiency and ultimately
conservation.
I also present my understanding of maximum demand metering, also termed time of use
(TOU) metering. Enermax and Enermax-Plus meters are used. These are four (4) quadrant
meters with large memory, are fully user configurable and enable data profiling.
I present my report as follows;
1. Introduction
2. Components of a metering system
3. Single phase and three phase energy meters
4. Maximum demand metering
5. Statistical metering
6. Prepaid metering
7. Conclusion and recommendations

3. 1. INTRODUCTION
Metering is the integration of instantaneous values with respect to time. It is applied for
the following purposes;
 Revenue collection
 Statistics
ZETDC has two meter test depots namely;
 Harare Depot; services Eastern, Northern and Harare regions.
 Bulawayo Depot; services Southern and Western Regions.
Each Depot comprises two sections;
a) Workshop Support Services
These are responsible for;
 Testing and verification of meters to meet the laid down standards.
 Repair meters.
 Calibration and adjustments of meters for proper operation.
b) Field Support Services
These are responsible for;
 Installation and commissioning of maximum demand and statistical
meters.
 Maintenance of maximum demand and statistical meters.
 Consultancy services to customers with load management systems.
 Site tests for meters suspected to be faulty.
2. COMPONENTS OF A METERING SYSTEM
A metering system comprises one or more of the following;
a) Current transformer(CT)
A metering CT transforms current to a value that is safe for the meter and provides
electrical isolation of the meter from the high voltage primary system. Standard ratios
are; 500/1A, 600/1A, 300/5A, 30-60/1A etc. Metering CTs are manufactured to
accuracy classes 0.1, 0.2, 0.5 or 1 for currents upto 120% of rated current and are
governed by standard IEC60044-1. A measuring CT is should saturate when the
primary current exceeds the percentage of rated current specified as the upper limit to
which the accuracy provisions apply. This means that at these higher levels of primary
current the secondary current is less than proportionate. The effect of this is to reduce
the extent to which any measuring device connected to the CT secondary is subjected
to dangerous current

4. b) Interposing CT
Interposing CT’s are used when the ratio of transformation is very high. The ratio of
main CTs is reduced to a level required by the meter. e.g. 5/1A etc.
c) Summation CTs
When the currents in a number of feeders need not be individually metered but
summated to a single meter, a summation current transformer can be used. The
summation CT consists of two or more primary windings which are connected to the
feeders to be summated, and a single secondary winding, which feeds a current
proportional to the summated primary current. A typical ratio would be 5+5+5/ 5A,
which means that three primary feeders of 5 are to be summated to a single 5A meter.
d) Metering Unit
A metering constitutes CTs and VTs in a metal housing, normally containing
insulating oil. Typical VT ratios are 33000/110V and of class 0.5. The CTs can be of
ratio 30-60/1A and class 0.5.
e) Meter
The meter takes transformed values of current and voltage and computes the energy
consumed in kWh. Intelligent meters also compute Vars consumed, power factor etc.
Meters can be grouped according to construction, function or location.
There are mainly three types of meters used in the ZESA system for both three and
single phase namely; electromechanical (induction) type, digital type and
microprocessor based type.
(i) Compensating Meter
This type of meter is placed on the primary side of a transformer. As the name
implies, it compensates for the transformer losses and the customer is billed the actual
energy consumed.
3. SINGLE & 3-PHASE CONVENTIONAL ENERGY
METERS
These energy meters, now being phased out for the digital prepaid meters were
conventional meters used to bill customers.
3.1 Induction disc meter
It consists of the following;
 Voltage coil-many turns of fine wire connected across load.
 Current coil-few turns of thick wire connected in series with load.

5.  Aluminium disc acting as rotor
 Steel core acting as stator to concentrate flux.
 Rotor brake magnets
 Spindle with worm gear
 Cyclometer to display units in 1/10, 10,1 000, 10 000 or 100 000.
3.1.1 Principle of Operation:
The disc is acted upon by 2 coils; a voltage coil connected in parallel the load in such
a way that it produces a flux in proportion to the voltage and a current coil connected
in series with the load, which produces a magnetic flux proportional to the current.
The field of the voltage coil is delayed by 90º so that eddy currents are produced in
the disc. The effect is such that force is exerted in proportional to the product of
instantaneous voltage and current.
The meter operates by counting revolutions of the aluminium disc which is made to
rotate at a speed proportional to the power being consumed by a load. The number of
revolutions is thus proportional to the energy usage. It consumes a small amount of
power, typically around 2 watts.
A permanent magnet exerts a force proportional to the speed of rotation of the disc,
acting as brakes which stop the disc from spinning when power is no longer being
drawn. The equilibrium of these two opposing forces results in the disc rotating at a
speed proportional to the power being used.
The disc is supported by a spindle which has a worm gear which drives the register.
The register is a series of dials which record the amount of energy consumed. The
dials maybe of a cyclometer type where for each dial a single digit is shown through
the window in the face of the meter.
I repaired, tested and calibrated single and three phase induction disc energy meters at
Harare workshop. Some of single phase, 2 wire meters are listed in the table below;
Make Type Rating Class Standard(s) Constant
Actaris MLXL4V3SA 20(80)A, 230V,50Hz 2 BS5685/1979 270rev/kWh
ABB M4F5 20(80)A, 230V,50Hz 2 BS5685/1979 280rev/kWh
Fuji Dharma FA14AI1MJ 20(80)A, 225V,50Hz 2 BS5685/1979 225rev/kWh
Pafal A522m 20(80)A, 225V,50Hz 2 BS5685/1979 187.5rev/kWh
Eurostar HX12D 20(80)A, 225V,50Hz 2 IEC 521 150rev/kWh
Some 3phase energy meters are shown in the table below;
Make Type Rating Class Standard(s) Constant
Eurostar HX349 20(80)A,3x 220V,50Hz 2 IEC521 50rev/kWh
Risesun DT217 20-100A,3x 220V,50Hz 2 IEC521 36rev/kWh

6. Landis & Gyr ML12 3x
25(50)A,3x220/380V,50Hz
2 IEC521 75rev/kWh
3.2 Digital energymeter
The digital energy meter, unlike the induction disc meter measures energy consumed
by counting number of pulses equivalent to a unit of energy. These meters have
higher accuracy. Some of the digital meters are shown in table below;
Make Type Rating Class Standard(s) Constant
Elster A/100 3x20(100)A,3x
230/400V,50Hz
1 IEC62053-
21:2003
5Wh/pulse.
5000imp/kWh
Premier P3TA23 3x5-6A,3x 230V,50Hz 1s
3.3 Repairing, Testing and Calibration of Energy Meters
3.3.1 Induction Disc Meters
Repairing of induction disc meters involved the following;
a) Testing continuity of voltage and current coils with a multimeter.
b) Checking disc alignment
c) Checking the bottom bearing (jewelled or magnet) for integrity.
d) Cleaning the cyclometer with benzene and checking operation.
e) Cleaning the magnet with masking tape.
Testing and calibration involves;
a) Full load test at unity power factor.
Test carried out to ascertain the accuracy of the meter when full load current is
being drawn (although full load current for most meters is 80A tests are
carried out at 40A because of the capacity of the test benches) except the
Universal Test bench (EDI Universal). The error margin should be within
±2%. Most of these meters are manufactured to class 2;
This means that when taking a random sample from a population of these
meters, it can be said with 95% confidence level that no less than 97.5% of the
meters in the population have accuracy between 98% and 102% of the rated
value.
b) Full load test at 0.5 factor
c) Low load (5% full load) at unity power factor
3.3.2 Digital meters
These meters are only calibrated and not repaired. Faulty meters are discarded.

7. 3.4 EDI Universal TestBench
The EDI system is computerized so as to achieve high levels of precision
Standard procedure is to load the meters and carry out five distinct tests
a) Hardware test-hardware circuit status including short/ open circuits etc.
b) Eye Test-alignment, pulse averaging
c) Full Load Test- 80A at pf 1.0
d) 0.5 Power Factor – 80A @ 0.5 pf
e) Low Load.- 5% of full load current
If any meter is faulty it can easily be picked up by the software and necessary
adjustments are done on the meter depending on the test failed.
4. MAXIMUM DEMAND(MD) METERING
Customers with installations rated 300kVA and or above 500A and above are categorised
under MD customers. The Electricity Act (Chapter 13:19) provides for this category
under subsection (8) of section 53. It reads, “Notwithstanding paragraph (d) of subsection
(3), in fixing or approving prices and tariffs the Commission may differentiate among
consumers on the basis of differences in total electricity consumption, the time periods
on which electricity is consumed, load factor, power factor, voltage levels, and other
such criteria as affect the cost of providing a service”.
The metering can be done from the HV side or LV side of the transformer depending on
the metering unit available. A metering unit comprise CTs, VTs, fuses and links housed
in one unit.
Three phase meters (MD) are rated (standardized) at 1A or 5A current and voltage coils at
110V or 230-380V rating.
4.1 MeterTypes
Strike Technologies have two meters being used in ZETDC;
 Enermax
 EnermaxPlus
These meters have the following powerful features;
 4 quadrant power and energy measurement.
 Fully user configurable.
 Large memory
 Time of use (TOU) metering.ie. A tariff that has different energy rates for
different time periods and seasons. Peak, standard and off-peak rates can be
programmed.
 Powerful data profiling i.e. a customer can study their load profile hourly.
 Multifunction input/outputs; output relays can be programmed to give out
energy pulses to an energy management system for a plant at programmed
interval.
 Audit facilities.

8. 4.2 Wiring
The various meter models can measure energy and demand in 3 or 4 wire systems,
and should be wired accordingly. Particular attention should be paid to differences
between voltage ratings for 3 or 4 wire systems, i.e. L-L and L-N respectively.
EnermaxPlus meters have standard type numbering that reference a wiring system.
This is illustrated below;
Character Description
E Enermax Plus equipment
+
M Meter
A Version with M16 memory, 3 I/O, Optical port, LCD
-
X 6 => 3x63.5V L-N; 50/60Hz; 4 wire
1 => 2x110V L-L; 50/60Hz; 3 wire
4 => 3x230V; L-N; 50/60Hz; 4 wire
5 => 3x380-550V; L-L; 50/60Hz; 3 wire
7 => 2/3 x100-400V L-L; 57.5-230V L-N; 50/60Hz; 3 or 4 wire
X 5 => CT range 1(2)A or 5(10)A; DIP switch selectable; Class 0.5
7 => Direct range 40(100)A; class 1.0
9 => Direct range 40(160)A; class 1.0
X 3 => Calibrated for class 0.5; 3 wire only
4 => Calibrated for class 0.5; 4 wire only
7 => Calibrated for class 0.5; 3 and 4 wire
0 Future Use
0 Future Use
0 Future Use
Typical wiring configurations are shown below;
a) 3 phase, 4 wire, direct voltage connection
b) 3 phase, 4 wire, voltage connection via VTs.
c) 3 phase, 3 wire, voltage connection via VTs.
I did maintenance of 3 phase, 3 wire MD point at Cohcoh factory in Graniteside. The
meter power is tapped from either red or blue phases voltage inputs and the grounded
yellow phase voltage.
4.3 ElectricalParameters
The table below shows some of the electrical parameters to be specified for EnermaxPlus
meters;

9. Specification Description
Accuracy Active energy –class 0.5 (IEC62053-22)
Reactive energy-class 2 (IEC62052-23)
Nominal Frequency 50/60Hz ±5%
Measurement Starting
thresholds
Starting voltage 45V for voltages: 57V, 110V and 230V
Starting current 0.1% In
CT Nominal Current(In) –IEC62053-8.3.3
Dip select In Imax Isc Over range 20A
1A 0…..2A 200% 0.5sec at 20.Imax For 60minutes
5A 0…..10A 200% 0.5sec at 20.Imax For 60minutes
Line Nominal Voltages
Range 100..400V 57….230V Operating voltage range
4 wire Line-Line Line-Neutral 80-----115%
3 wire ------------- Line-common 80-----115%
4.1 Maintenance of MD points
During maintenance of these points, the following are checked;
a) The Enermax and EnermaxPlus meters operation occurs in the two quadrants, 1
and 4. Once this configuration, the total active power consumed is determined by
the 2 wattmeter method;
𝑃 𝑇𝑜𝑡 = 𝑃𝑅 + 𝑃𝐵
Where PT = total active power consumed; PR= active power in red phase; PB =
active power in blue-phase.
This is done by checking the following;
 Active power measurements as measured in Red and Blue should
algebraically add to total active power.
 Current and voltage phasors or vectors on the vector representation, which
must take any of the two configurations;
(i) In clockwise direction, the Red-phase current vector comes first, followed by red
–phase voltage vector, then Blue-phase voltage vector and Blue-phase current
vector. In this configuration, red-phase is metered in quadrant 1 whilst blue-phase
is metered in quadrant 4.

10. (ii) In clockwise direction, the Blue-phase current vector comes first, followed by
Blue –phase voltage vector, then Red-phase voltage vector and Red-phase current
vector. In this configuration, Blue-phase is metered in quadrant 1 whilst Red-
phase is metered inn quadrant 4.
If the vector representation does not conform to any of the two graphical
representations, the two wattmeter relationship becomes invalid. To correct this swap
the Red and Blue phase CT inputs and observe vector diagrams again.

11. 4.2 Installation of MD points
To fully appreciate installation of MD metering points, I assisted to install an MD point at
Springvale Girls High in Marondera. The installation had the following equipment;
4.2.1 Equipment
a) Transformer Details
 315kVA, 33000/400V, 5.51/454.67A, 50Hz, Dny11.
b) Metering Unit Details
 Make: Electroresin
 Type designation: 9303
 BIL: 36/70/170kV
 Creepage distance: 25mm/kV
 VTs: 33000/110V, 50Hz, 100VA/phase, Class 0.5, BS3941
 CTs: 30-60/1A, 10VA/phase, Class 0.5, Isc = 13.1kA for 0.5sec
c) MD Meter Details
 Make: Strike Technologies
 Type: EnermaxPlus, EM153000. (3 phase, 3-wire wiring).
 3 phase, 3 wire.
 1(2)-5(6) A, 100-160V, 50Hz.
d) Auxiliary Equipment
 10 core, 2.5mm2 cable, black.
 3 Fuses for VT inputs.
 13 port test terminal block.
 2.5mm2 single black cable roll.
 Earthing bolt.
 100cm x 100cm 8mm thick asbestos board.
 Hand drill and bits.
 Utility seals.
 Personal computer with working EmanPlus software tool.
4.2.1 Configuration with EmanPlus
After all hardware has been installed, the meter was commissioned with EmanPlus tool.
The following setup templates were written into the meter;
a) Meter (Customer) details
 Location e.g. Marondera
 Name of point e.g. Springvale
b) Engineering Date
 CT ,VT ratio,
 Integrating periods (interval),

12.  Pulse weight,
 Pulses required for power usage.
 Reset mode
 Display options.
c) Tariff data
 Rate
 Time(season)
 Public holiday
 Defining the time slots for normal, peak and off peak periods.
We also checked the phasor rotation and it showed power measurement in
quadrants 1 and 4.
5. STATISTICAL METERING
This metering facilitates the following;
a) Loss reduction
b) Improvement in network planning.
c) Operation of generation, transmission and distribution business units.
d) Improved customer relations.
The figure below shows layout of a statistical metering monitoring losses on a feeder
connecting two substations A and B. The energy measured at A is more than that at end
B, suggesting that losses occurred on the feeder.
Losses are divided into two groups, technical and non-technical;
a) Technical Losses
Technical losses are caused by flaws in design and configuration of the system. This
manifests in the following forms;

13.  Copper losses on feeders.
 Iron losses in transformers
 Copper losses in transformers
 Usage losses
b) Technical Losses
These losses are not associated with technical aspects of the system, but rather on the
following factors;
 Wrong wiring of the meter installation.
 Tampering of meter connections.
Types of Statistical meters
In ZETDC we have the following types of statistical meters installed in transmission,
sub-transmission and distribution substations;
 Apex meters-mostly on 33kVand 11kV outgoing feeders.
 Enermax meters –on national grid and sub-transmission transformers.
 Schlumberger meters-on Songo Interconnector and national grid transformers.
 L & G meters-on 110kV Revue interconnector, 33kV feeders, and transformers.
Some of the circuits are not metered due to some of the following;
 Faulty units
 Unavailability of instrument transformers.
 No meters installed.
6. REPAID METERING
As part of efforts to improve revenue collection from customers, ZETDC is installing
prepaid meters in domestic and industrial installations. Other benefits to the customer and
utility are;
 Customer’s ability to manage own consumption.
 Increased customer satisfaction.
 Reduced load shedding through energy conservation.
 Reduced billing and administration costs to the utility.
 Working capital savings through earlier receipt of payments.
 Reduction in bad debts.
Prepaid meters are available in single phase, 2 wire DIN and BS types. Three phase types are
also available. The table below summarises the allocation of single phase and three phase
meters by sub-contractor contracted by ZETDC.
Single Phase BS Single Phase DIN Three Phase
Nyamezela X
Solarhart X
ZTE X

14. Finmark X X X
These meters are of split type, that is to say a combination of a measurement control unit
(MCU) and a customer interface unit (CIU) or user interface unit (UIU. The following type
designations are being installed;
Make Type(s) Single/3-phase DIN/BS
Clou CL730S1 3-phase
Inhemeter DDZ1513 Single phase DIN
DTZ1513 3-phase BS
Hexing HXP100D1 Single phase DIN
Cashpower 10PL022 Single phase BS
5.1 MCU
The MCU contains the measuring unit, the load switch, real time clock and communication
functions such as IR or RS485. The live and neutral wires from the supply pass though the
MCU load switch. The MCU can be installed indoors, in a centralized meter box or on a
telegraph pole. The single phase meters are rated for maximum working current of 80A at
50Hz.
For Clou and Cashpower meters, the MCUs have keypads and display whilst for Hexing and
Inhemeter, the MCUs neither have keypads nor display.
The MCU calculates the following;
 Energy consumed and credit remaining.
 Rate of energy consumption.
 Power factor
 Vars consumed
 Credit Status.
 Load switch status.
5.2 CIU or UIU
The CIU has display and control functionality. Connection to the MCU is via power line
carrier (PLC) communication technology using the household wiring. The CIU is plugged
into one of the sockets. Phase shift keying (PSK) modulation technique can be applied, using
frequencies like 132 kHz. This conforms to IEC61334-4-41 standard. Reliable
communication is guaranteed during commissioning.
5.3 Technical Specifications for prepaid meters

15. For guaranteed satisfactory performance, the prepaid meters should meet the following
specifications;
Specification Description
Meter type e.g. Single-phase two wire direct connect, DIN rail mounting, split
energy meter, with PLC communication CIU;
Active energy
metering direction
Detect reverse energy with alarm; Forward and reverse consumption
will be added to total active accumulated energy;
Rated operating
voltage (Un)
e.g. 230V
Working voltage
range
e.g. 0.7Un – 1.2Un-Within this range, certainly will the meter work
normally.
Limit operating
voltage range:
0Un～1.90Un-Within this range, prepayment meter will not be
damaged; meter will indicate normally, but it’s not guaranteed that
the accuracy class as well as load control equipment’s normal
operation.
Working frequency 50±5Hz
Active metering
accuracy
Class 1-conforms to IEC62053-21
Basic current（Ib） e.g. 5A
Maximum working
current
e.g. 80A
Starting current e.g. ≤ 20mA (0.4% of Ib)
Meter’s current
measurement range
e.g. 20mA- 100A
Limit current for
accurate metering
e.g. 100A
Short-time over
current
e.g. 3kA
Power consumption e.g. Voltage circuit: 1.5W (or < 4VA) at 240V
Current circuit: <0.2VA at basic current.
Meter impulse
constant
e.g. 1000imp/kWh
Working
temperature
e.g. -25℃～+75℃
PLC communication
mode
e.g. Power line carrier modulation mode: PSK Frequency: 132kHz;
Comply with: IEC61334-4-41,
PLC Communication
distance
150m
Insulation
performance
e.g. Class II insulation envelope protection instruments, protection
grade 2 , double insulation
Pulse voltage e.g. 6kV-according to IEC62053-21(1.2/50μs)
AC withstand e.g. 4kV (5mA) between live and earth -IEC60060; 2kV (5mA)

16. voltage between auxiliary terminals.
Current impulse e.g. Service rating 5kA 8/20μs;Withstand rating 30 kA, 4/10μs
Electromagnetic
compatibility-
IEC62053-21
requirements
Electrostatic
Discharge Immunity
Contact discharge – 8kV
Air discharge- 15kV
HF electromagnetic
field immunity
80MHz-2GHz
30V/m
Fast transient burst 4KV/2.5KHz
Radio interference test Equipment of CISPR 22 B class
Surge immunity 4kV
Immunity to
conducted
disturbances, induced
by radio-frequency
fields
150kHz － 80MHz
10V
Cover and terminal
layout
e.g. Comply with DIN rail mounting, top terminal is incoming
line(L,N), below terminal is out coming line (L); for BS meter, wiring
is LNNL.
Cover material e.g. Fire retardant, flame resistant, anti-thermal-deformation
engineering plastic PC + GF
Fire retardant test: comply with 960°C glowing filament test
(IEC60695-2-1）
Flammability test: UL94-V0 rated @1.5mm. No toxic gases emitted:
Green material
Terminals: e.g. Main terminal uses pressure plate moving cage terminal, each
terminal has one sealable antirust cable fixing screw. Hole Diameter :
9mm, Maximum cable size: 30mm2
Seal e.g. Meter is equipped with 1 sealing unit: 3 wires with seals to fasten
screws
Weight About 350g
Dimensions e.g. 46mmX87mmX138mm (W X D X H)
5.4 Standard Transfer Specification(STS)
In prepayment metering, STS is a secure message system for carrying information between a
point-of-sale and a meter. Developed by South Africa under 3 specification documents;
NRS009-6-6:2002; NRS009-6-7:2002 and NRS009-6-9:1997, it is yet to pass official IEC
publication under IEC 62055 parts -41 and -51.
STS addresses security of the prepayment system as well as interoperability of equipment
amongst different manufacturers.
a) Security
 Fraudulent generation of tokens from hit and miss attempts at entering the correct
number;
 Fraudulent generation of tokens from a stolen vending station;
 Fraudulent generation of tokens from legitimate vending stations outside of the
utility's area;
 Fraudulent use of tokens which have already been used;

17.  Tampering of legitimate tokens e.g. to change the value
To achieve security STS provides the facility of generating tokens which can only be used by
the intended meter, and furthermore in the case of credit tokens, can only be used once in that
meter. This is achieved by;
 Use of advanced encryption techniques, which are at all times hidden from the
consumer -the system is easy to use.
 Use of very secure key management procedures, including the manner in which keys
are generated and transported.
 Required functionality at both the vending station and the meter.
b) Interoperability
STS is an open system specification which defines transfer tokens which may be generated at
a vending system from any supplier and used in STS compliant meters from any supplier.
The functionality at the vending station and the response of meters to certain transfer
numbers is also specified in order to achieve inter-operability. This allows utilities to mix and
match equipment from suppliers of their choice.
This is ensured by:
 Ensuring that manufacturing members make encryption keys available to other
manufacturers at the request of the utility using the equipment;
 Accrediting and maintaining a list of equipment test laboratories which ensure correct
STS functionality of equipment;
 Ensuring consistent manufacturer identity codes and meter serial numbers.
STS and Proprietary Vouchers:
STS vouchers have 20-digit numbers.
Voucher Type Function
Electricity credit Meter-specific
voucher
Transfers a variable quantity of credit to the
meter.
Set 1st dispenser key Meter-specific
voucher
-changes the key to maintain security of a
pre-payment system. Meter and vending
machine to operate on same key.Set 2nd dispenser key Meter-specific
voucher
Clear tamper Meter-specific
voucher
-restores normal operation after locks out due
to tampering.
-resets power fail counter and significant
power reverse flag
Set maximum power load or
power limit level
Meter-specific
voucher
-sets the power limit level for the meter
Set current credit levels Meter-specific,
proprietary voucher
-sets the appropriate high and low credit
levels

18. Clear credit Meter-specific,
proprietary voucher
- clears any remaining credit to zero and
opens the load switch, thus interrupting the
electricity supply to the customer.
Initiate dispenser test Non-meter-specific,
voucher
- meter executes all the tests that are
embedded in that particular voucher. e.g.
HMI test, display tamper state, display power
limit level, display tariff index etc.
Commissioning voucher Meter-specific,
proprietary voucher
-assists meter installation personnel by
ensuring that the load remains disconnected
and the tamper detect sensing switch function
disabled (meter decommissioned). Once
installation is complete and the number
entered, the load switch closes and the tamper
detect sensing switch function is enabled.
Commissioning voucher Non-meter-specific,
proprietary voucher
Decommissioning voucher Meter-specific,
proprietary voucher
- meter opens the load switch (load
disconnected) and disables the tamper detect
sensing switch function
Set credit-metering mode Meter-specific,
proprietary voucher
- on accepting a set credit metering mode
voucher, the meter commences operation.
Set prepayment-metering
mode
Meter-specific,
proprietary voucher
- on accepting a set prepayment metering
mode voucher, the meter commences
operation
5.5 Anti-tamper facility
On installation, the meter cover is fitted to the meter with a single terminal cover screw. The
screw is then sealed with utility-sealed wire seals to ensure that there is a visible sign of
tampering from the front of the meter.
a) Anti-Tamper Switch
The tamper facility automatically detects if the meter terminal cover is removed. This
condition will set the tamper state thereby causing the meter to disconnect power to the
household – it will remain in the tampered state when the cover is re-fitted to the meter.
The tamper detect function may be enabled or disabled during production, or by means of a
Set Options Register token.
b) Reverse Energy Detection
The meter includes a Significant Reverse Energy (SRE) detection feature. If the line and load
wires are swapped during installation, the meter will continue to operate and decrement
credit. However, the meter can be factory-programmed to tamper and disconnect the load
should SRE be detected.

19. c) Resetting a Tamper Condition
Before resetting a tamper condition, care must be taken to remove the cause of the condition,
e.g. ensure that the meter is wired correctly and that the terminal cover is securely fitted to
the meter and that the tamper switch is closed.
Once the terminal cover is fitted to the meter, check that the tamper switch is fully depressed
by checking the tamper switch status in the meter state registers. If a meter has been
tampered, normal operation can only be restored by entering a clear tamper voucher.
5.6 ProjectProgress
The project is being done in 2 phases;
a) Phase 1
Phase 1 involves installation of 22 000 meters in Harare and Bulawayo. This is a pilot
scheme.
b) Phase 2
Phase 2 involves installing meters in the rest of the country. A total of 580 000 meters will be
installed countrywide.
5.6 Challenges
The following challenges have been encountered during installation of prepaid meters;
 Access to premises
 Contractor misinforming customers about prepaid meters.
 Bypass meter connections by ZETDC staff.
 Impact of load shedding on installation and inspections.
7. CONCLUSION & RECOMMENDATIONS
a) Recommendations
The table below shows some challenges I have observed. I have also included
recommendations to mitigate these challenges;
Challenge Mitigation
Mete tampering is inherent with
customers. e.g. changing of tariff
codes
1. Monitoring meter activity from a
central point by using modems, analyse
and act on inconsistencies.
2. Applying load limiters for domestic
customers

20. .
b) Conclusions
I would like to thank the Meter Test personnel for introducing and teaching me all aspects
of metering. Of special mention is theory of maximum demand (MD) metering and prepaid
metering. The latter is an essential project to ZETDC with regards to collecting revenue as
the utility is owed close to US$500million by various customers-agricultural, residential,
industrial and commercial.
END