CHAPTER 1 INTRODUCTION 1.1 INTRODUCTION TO TRAINING Training is a process of learning. Training is an organized procedure during which people learn knowledge and skill for the definite purpose. It is a short-term process utilizing a systematic and organized procedure in which non-managerial personnel learn technical knowledge and skills for a definite purpose. It refers to instruction in technical and mechanical operations like operation of a machine. It is for a short duration and for a specific job related purpose. Training is very difficult from education. Training is vocational where as education is general. Training is job-oriented whereas education is person-oriented. However, it is difficult in practice to differentiate between education and training because in many cases both of them occur simultaneously. The two are complementary and both involve development of talent and human potential. Generally, every level needs training. Training is not something that is done once to new employees; it needs to be done continuously. 1.2 IMPORTANCE OF TRAINING: Training leads to higher productivity. It leads to better quality of work. It leads to cost reduction. It leads to high motivation and morale of employees. The organizational climate gets improved. It leads to self-satisfaction of the employees. Supervision gets reduced. 1
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CHAPTER 1
INTRODUCTION
1.1 INTRODUCTION TO TRAINING
Training is a process of learning. Training is an organized procedure during which people learn
knowledge and skill for the definite purpose. It is a short-term process utilizing a systematic and organized
procedure in which non-managerial personnel learn technical knowledge and skills for a definite purpose. It
refers to instruction in technical and mechanical operations like operation of a machine. It is for a short
duration and for a specific job related purpose.
Training is very difficult from education. Training is vocational where as education is general.
Training is job-oriented whereas education is person-oriented. However, it is difficult in practice to
differentiate between education and training because in many cases both of them occur simultaneously. The
two are complementary and both involve development of talent and human potential.
Generally, every level needs training. Training is not something that is done once to new employees; it
needs to be done continuously.
1.2 IMPORTANCE OF TRAINING:
Training leads to higher productivity.
It leads to better quality of work.
It leads to cost reduction.
It leads to high motivation and morale of employees.
The organizational climate gets improved.
It leads to self-satisfaction of the employees.
Supervision gets reduced.
It leads to good cordial relation between employer and employee.
It leads to development of new skills in the employees.
1.3 SCOPE OF SUMMER TRAINING:
The summer training programs are designed for the students to master their technical skills. The summer
training should include the following objectives-
a) Correlate courses of study with the way industry or potential work place operates its business or work
using technology.
b) Work on implementing what has been learned in school or college.
The engineering and professional courses including MCA, B.E., B.TECH, BCA amongst other have
undergraduates needing internship in fields of computer science, electrical and electronics, mechanical,
civil, bio-informatics, etc. The students for professional programs are required as a part of courses to
undergo a few weeks (or months) training. 1
Summer training is a good strategy with variations suiting the individual’s tastes by improving their
experience and making them reach a good enough company or workplace just in time.This training can
result in learning of open source technology as a user of technology. That technology can be applied to
improve the college infra-structure. The objective of training in Modern Office Practice is to give a
perspective about the organization and functioning of all the areas of management in an industrial unit.
1.4 COMPANY PROFILE:
SKN-BENTEX group started operations 50 years back at Delhi, the capital state of India with
manufacturing of Electrical items. Chopra Brothers Mr. Satish Chopra, Mr. Kapil Chopra & Mr. Nishit
Chopra have promoted the group.
SKN-BENTEX” Group products are at the forefront of innovation in industrial and agricultural field
for protection and control of Electric Motor. It is the pioneers and leaders in the field with latest international
engineering products based on the world’s best technology since last four decades. “SKN-BENTEX” Group
has a rich history of success, which has been achieved through dedication, teamwork and visionary thinking
and sincere service of pride in result oriented performance. “SKN-BENTEX” Group has been continuously
restructuring to set up state-of-the-art electrical products manufactured at their own plants under strict
quality control standard. In this thrust, most of group companies adopted International Quality Standard and
have been certified for ISO-9001 Certification and products are also available on ISI-Marked. The SKN-
BENTEX Group of Companies engaged in wide range of products and has mainly three subgroups of
electrical product range such as “SKN”, “SKN” Bentex Linger “BENTEX-Linger” with their separate
products line and “SKN-BENTEX” Group is a collection of smaller company’s specialist in a specific range
of products. Besides this “SKN-BENTEX” group engaged in the field of, LPG Home Appliances, LPG
Regulators, Building Construction and Export Activities.
Home Appliances: LPG Gas Stove , Cooking Range (OTG & Oven), LPG Burner, LPG Regulator &
Adaptor, Gas Stove with Copper Brazed Cylinder, Hotel Equipments: Kitchen Equipments, Service
Trolleys, Deep & Vertical Freezers, India Railways: Water Tanks, Luggage Racks, Doors, Pantry
Equipments for Coaches.Electrical Appliances: MCB, MCCB, ELCB, Energy Meter, Motor Starters &
Complete Range of Electrical Products.
Mono Block Pump, Exhaust Fan, Auto LPG Conversion Kit with Cylinder, CNG Conversion Kit,
Building Construction Township Development, Hotel & Clubs, Retail Shopping Malls, LPG Dispensing
Station to undertake Turnkey Project for installation & Commissioning. Haryana City Gas to Undertake
Turnkey Project for distribution of Natural Gas to Domestic, Commercial, Industrial and Transport sector.
Firm Type
Nature of Business
Level to Expand
:Proprietorship
:Manufacturer,Export/Import
:International
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Today, with the above wide range of products SKN-Bentex group is a well-recognized name in
Indian Household. Group has already achieved turnover of USD 50.00 Mn and has employed more than
1000 employees in 8 manufacturing locations in National Capital region of Delhi and regional offices
supporting our business through- out the country. After making its presence felt in the domestic market,
Group has already spread wings in internationally n started exports to various countries through a separate
export division.
CHAPTER 2
ENERGY METER
2.1 INTRODUCTION
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An electric meter or energy meter is a device that measures the amount of electrical energy supplied
to or produced by a residence, business or machine. Electricity is a clean, convenient way to deliver energy.
The electricity meter is how electricity providers measure billable services.
The most common type of meter measures kilowatt hours. When used in electricity retailing, the
utilities record the values measured by these meters to generate an invoice for the electricity. They may also
record other variables including the time when the electricity was used.
Since it is expensive to store large amounts of electricity, it must usually be generated as it is needed.
More electricity requires more generators, and so providers want consumers to avoid causing peaks in
consumption. Electricity meters have therefore been devised that that encourage users to shift their
consumption of power away from peak times, such as mid-afternoon, when many buildings turn on air-
conditioning.
For these applications, meters measure demand, the maximum use of power in some interval. In
some areas, the meters charge more money at certain times of day, to reduce use. Also, in some areas meters
have relays to turn off nonessential equipment.
Providers are also concerned about efficient use of their distribution network. So, they try to
maximize the delivery of billable power. This includes methods to reduce tampering with the meters.
Also, the network has to be upgraded with thicker wires, larger transformers, or more generators if parts of it
become too hot from excessive currents. The currents can be caused by either real power, in which the
waves of voltage and current coincide, or apparent power, in which the waves of current and voltage do not
overlap, and so cannot deliver power.
Since providers can only collect money for real power, they try to maximize the amount of real
power delivered by their networks. Therefore, distribution networks always incorporate electricity meters
that measure apparent power, usually by displaying or recording power factors or volt-amp-reactive-hours.
Many industrial power meters can measure volt-amp-reactive hours.
Figure: 2.1 ENERGY METER
2.2 UNITS OF MEASUREMENT:
The most common unit of measurement on the electricity meter is the kilowatt hour, which is equal
to the amount of energy used by a load of one kilowatt over a period of one hour, or 3,600,000 joules. Some
electricity companies use the SI mega joule instead.4
Demand is normally measured in watts, but averaged over a period, most often a quarter or half hour.
Reactive power is measured in "Volt-amperes reactive", (varh) in kilovar-hours. A "lagging" or inductive
load, such as a motor, will have negative reactive power. A "leading", or capacitive load, will have positive
reactive power.Volt-amperes measures all power passed through a distribution network, including reactive
and actual. This is equal to the product of root-mean-square volts and amperes.
Distortion of the electric current by loads is measured in several ways. Power factor is the ratio of
resistive (or real power) to volt-amperes. A capacitive load has a leading power factor, and an inductive load
has a lagging power factor. A purely resistive load (such as a fillament lamp, heater or kettle) exhibits a
power factor of 1. Current harmonics are a measure of distortion of the wave form. For example, electronic
loads such as computer power supplies draw their current at the voltage peak to fill their internal storage
elements. This can lead to a significant voltage drop near the supply voltage peak which shows as a
flattening of the voltage waveform. This flattening causes odd harmonics which are not permissible if they
exceed specific limits, as they are not only wasteful, but may interfere with the operation of other equipment.
Harmonic emissions are mandated by law in EU and other countries to fall within specified limits.
2.3 TYPES OF METERS
Modern electricity meters operate by continuously measuring the instantaneous voltage (volts) and
current (amperes) and finding the product of these to give instantaneous electrical power (watts) which is
then integrated against time to give energy used (joules, kilowatt-hours etc). The meters fall into two basic
categories:
(a)Electromechanical Meters
(b)Electronic Meters.
CHAPTER 3
ELECTROMECHANICAL METERS
3.1 INTRODUCTION:
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The most common type of electricity meter is the Thomson or electromechanical induction watt-hour
meter, invented by Elihu Thomson in 1888. The electromechanical induction meter operates by counting the
revolutions of an aluminium disc which is made to rotate at a speed proportional to the power. The number
of revolutions is thus proportional to the energy usage. It consumes a small amount of power, typically
around 2 watts.
The metallic disc is acted upon by two coils. One coil is connected in such a way that it produces a
magnetic flux in proportion to the voltage and the other produces a magnetic flux in proportion to the
current. The field of the voltage coil is delayed by 90 degrees using a lag coil. This produces eddy currents
in the disc and the effect is such that a force is exerted on the disc in proportion to the product of the
instantaneous current and voltage. A permanent magnet exerts an opposing force proportional to the speed of
rotation of the disc. The equilibrium between these two opposing forces results in the disc rotating at a speed
proportional to the power being used. The disc drives a register mechanism which integrates the speed of the
disc over time by counting revolutions, much like the odometer in a car, in order to render a measurement of
the total energy used over a period of time.
FIGURE NO: 3.1 ELECTROMECHNICAL ENERGY METER
3.2 CONSTRUCTION:
The construction varies in details from one manufacturer’s product to the next. However, the
differences are very minor in nature.
There are four main parts of the operating mechanism:
1. Driving System 3. Braking System
2. Moving System 4. Registering System
1. Driving System
The driving system of the meter consists of two electromagnets. The core of the electromagnets is
made up of silicon-steel laminations. The core of one of the electromagnets is excited by the load current.
This coil is called the current coil. The coil of second electromagnet is connected across the supply and,
therefore, carries a current proportional to the supply voltage. This coil is called the pressure coil.
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Consequently the two electromagnets are known as series and shunt magnets respectively.
Copper shading bands are provided on the central limb. The position of these bands is adjustable. The
function of these bands is to bring the flux produced by the shunt magnet exactly in quadrature with the
applied voltage.
2. Moving System
This consists of an aluminium disc mounted on a light alloy shaft. This disc is positioned in the air
gap between series and shunt magnets. The upper bearing of the rotor (moving system) is a steel pin located
in a hole in the bearing cap fixed to the top of the shaft. The rotor runs on a hardened steel pivot, screwed to
the foot of the shaft. The pivot is supported by a jewel bearing. The pinion engages the shaft with the
counting or registering mechanism.
A unique design for the suspension of the disc is used in the floating shaft energy meter. Here the
rotating shaft has a small magnet at each end, where the upper magnet of the shaft is attracted to a magnet in
the upper bearing and the lower magnet of the shaft is attracted to a magnet in the lower bearing. The
moving system thus floats without touching either bearing surface, or the only contact with the movement is
that of the gear connecting the shaft with the gear of the train, thus the friction is drastically reduced.
3. Braking System
The permanent magnet positioned near the edge of the of the Aluminum disc forms the braking
system. The aluminium disc moves in the field of this magnet and thus provides a braking torque. The
position of the permanent magnet is adjustable, and therefore, braking torque can be adjusted by shifting the
permanent magnet to different radial positions.
4. Registering System
The function of a registering or a counting mechanism is to record continuously a number which is
proportional to the revolutions made by the moving system. By a suitable system, a train of reduction gears
the pinion on the rotor shaft drives a series of five or six pointers. These rotate on round dials which are
marked with ten equal divisions.
FIGURE NO: 3.2 DIMENSIONS DRAWING OF ELECTROMECHANICAL METER
3.3 OPERATION
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The supply voltage is applied across the pressure coil. The pressure coil winding is highly inductive
as it has very large number of turns and the reluctance of its magnetic circuit is very small owing to presence
of air gaps of very small length. Thus the current I through the pressure coil is proportional to the supply
voltage and lags it by a few degrees less than 90. This is because the winding has a small resistance and
there are iron losses in the magnetic circuit. Current produces a flux. This flux divides itself into two parts.
The major portion of it flows across the side gaps as reluctance of this path is small. The reluctance to the
path of flux is large and hence its magnitude is small. This flux goes across aluminium disc and hence is
responsible for production of driving torque. Flux is in phase with current I and is proportional to it.
Therefore flux is proportional to voltage V and lags it by an angle a few degrees less than 90. Since flux is
alternating in nature, it induces an eddy emf E in the disc which inturn produces eddy currents. The load
current I flow through the current coil and produce a flux. This flux is proportional to the load current and is
in phase with it. This flux produces eddy current Ies in the disc. Now the eddy current Ies interacts with flux
to produce a torque and eddy current interacts with flux to produce another torque. These two torques are in
opposite direction and the net torque is the difference of these.
3.3.1 Lag Adjustment Devices:
Meter will register true energy only if the angle is made equal to 90. Thus the angle between the
shunt magnet flux and the supply voltage V should be equal to 90. This requires that the pressure coil
winding should be so designed that it is highly inductive and has a low resistance and the iron losses in the
core are small. But even with this the phase of flux is not 90 wrt V but a few degrees less than 90. The
required mmf is obtained from a ‘lag coil’ which is located on the central limb of the shunt magnet close to
the disc gap and links with the flux that cuts the disc.
Some Important Readings
8
The arrangements for adjusting the mmf of the lag coil are:
1. Adjustable Resistance: A few turns of fairly thick wire are placed around the central limb of the
shunt magnet and the circuit is closed through a low adjustable resistance. The resistance of this
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circuit is altered to adjust the lag angles of flux. The resistance of the lag coil is so adjusted that angle
becomes equal to 90.
2. Shading Bands: In this, copper shading bands L are placed around the central limb of shunt magnet
instead of a lag coil with adjustable resistance. The adjustment can be done by moving the shading
bands along the axis of the limb. As the shading bands are moved up the limb, they embrace more
flux. This results in greater values for induced emf, current and mmf AT produced by the shading
bands and therefore the values of lag angle decreases. When the shading bands are moved down
limb, mmf AT decreases and the lag angle is reduced. The adjustment is so done that angle is equal
to 90 degrees.
3.3.2 Light Load or Friction Compensation:
Despite every care taken in the design of both the jeweled-pivot bearing, which forms the lower
bearing for the spindle, and of the simple sleeve pin-type bearing at the top of the spindle, friction errors are
liable to be serious particularly at light loads. In order to ensure accurate registration at low loads, it is
therefore necessary to arrange for small torque, practically independent of the load on the meter, which acts
in the direction of rotation and which is nearly as possible equal in magnitude to the friction torque. This is
usually obtained by means of a small shading loop situated between the centre pole of the shunt magnet and
the disc and slightly the one side of the centre-line of the pole.
3.4 CREEP:
In some meters a slow but continuous rotation is obtained even when there is no current flowing
through the current coil and only pressure coil is energized. This is called creeping. The major cause for
creeping is over-compensation for friction. If the friction compensating device is adjusted to give a driving
torque to compensate for starting friction which is bigger than the running friction
There is a tendency for the disc to run even when there is no current through the current coils because
the friction compensation torque is independent of the load current as the compensating device is voltage
actuated. The other causes for creeping are excessive voltage across the potential coil, vibrations, and stray
magnetic fields.
In order to prevent this creeping two diametrically opposite holes are drilled in the disc, the disc will
come to rest with one of the holes under the edge of a pole of the shunt magnet, the rotation being thus
limited to a maximum of half a revolution.
In some cases a small piece of iron is attached to the edge of the disc. The force of attraction exerted by
the brake magnet on the iron piece is sufficient to prevent creeping of disc.
Overload Compensation
It’s customary to add an overload compensating device. This usually takes the form of a magnetic
shunt for the series magnet core. The magnetic shunt approaches saturation and so its permeability decreases
at overloads. Thus at large currents the magnetic shunt diverts less of series magnet flux, so that a larger
portion of the flux appears in the disc air gap and contributes to driving torque.
Voltage Compensation
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A certain amount of variation is permitted in the declared voltage of supply. Therefore, energy meters
must be compensated for this variation. Voltage variations cause errors owing to two reasons:
1. The relationship between shunt magnet flux and the supply voltage is not linear owing to saturation
in iron parts;
2. The shunt magnet flux produces a dynamically induced emf in the disc which in turn results in a self-
braking torque which is proportional to square of the supply voltage.
Temperature Compensation
An increase in temperature is accompanied by a rise in resistance of all cooper and aluminium parts and
results in:
1 A small decrease in the potential coil flux and a reduction in angle of lag between V and flux.
2 A decrease in torques produced by all shading bands
3 An increase in the resistance of the eddy current paths
4 A decrease in the angle of lag of the eddy currents
3.5 ERRORS IN SINGLE PHASE ENERGY METERS:
The errors caused by the driving system are:
1. Incorrect magnitude of fluxes: This maybe due to abnormal values of current or voltage. The shunt
magnet flux maybe in error due to changes in resistance of coil or due to abnormal frequencies.
2. Incorrect phase angles: There may not be proper relationship between the various phasors. This
maybe due to improper lag adjustments, abnormal frequencies. Change in resistance with
temperature etc.
3. Lack of Symmetry in magnetic circuit: In case the magnetic circuit is not symmetrical, a driving
toque is produced which makes the meter creep.
The errors caused by the Braking system are:
1. Changes in strength of brake magnet
2. Changes in disc resistance
3. Self braking effect of series magnet flux
4. Abnormal friction of moving parts
3.6 ADJUSTMENT IN SINGLE PHASE ENERGY METERS
Some adjustments are carried out in energy meters so that they read correctly and their errors are within
allowable limits. The sequence of these adjustments are:
1. Preliminary Light Load Adjustment: The disc is so positioned that the holes are not underneath the
electromagnets. Rated voltage is applied to the potential coil with no current through the current coil.
The light load device is adjusted until the disc just fails to start.
2. Full Load Unit Factor Adjustment: The pressure coil is connected across the rated supply voltage and
rated full load current at unity power factor is passed through the current coils.
3. Lag Adjustment (Low Power factor adjustment): The pressure coil is connected across rated supply 11
voltage and rated full load current is passed through the current coil at 0.5 p.f. lagging. The lag
device is adjusted till the meter runs at correct speed.
4. With rated supply voltage, rated full load current and unity power factor, the speed of the meter is
checked and full load unity p.f. and low p.f. adjustments are repeated until the desired accuracy limits
are reached for both conditions.
5. Light Load Adjustment: This is done so that meter runs at correct speed.
6. Full load unity power factor and light load adjustments are again done until speed is correct for both
loads i.e. full load as well aslight load.
7. The performance is rechecked at 0.5 p.f. lagging.
8. Creep Adjustment
3.7 READING ELECTROMECHANICAL METERS
The aluminium 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 used. The dials may be of the cyclometer type,
an odometer-like display that is easy to read where for each dial a single digit is shown through a window in
the face of the meter, or of the pointer type where a pointer indicates each digit. It should be noted that with
the dial pointer type, adjacent pointers generally rotate in opposite directions due to the gearing mechanism.
The amount of energy represented by one revolution of the disc is denoted by the symbol Kh which is given
in units of watt-hours per revolution. The value 7.2 is commonly seen. Using the value of Kh, one can
determine their power consumption at any given time by timing the disc with a stopwatch. If the time in
seconds taken by the disc to complete one revolution is t, then the power in watts is
P = 3600. Kh/T
For example, if Kh = 7.2, as above, and one revolution took place in 14.4 seconds, the power is 1800
watts. This method can be used to determine the power consumption of household devices by switching
them on one by one.
Most domestic electricity meters must be read manually, whether by a representative of the power
company or by the customer. Where the customer reads the meter, the reading may be supplied to the power
company by telephone, post or over the internet. The electricity company will normally require a visit by a
company representative at least annually in order to verify customer-supplied readings and to make a basic
safety check of the meter.
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CHAPTER 4
ELECTRONIC METERS
4.1 INTRODUCTION
Electronic meters compared to traditional mechanical solutions in use offer several additional
advantages to the utility market. The metering utilities that can be replaced are gas, water and electricity.
The advantages are:
• Better reliability
• Better accuracy
• Ease of calibration
• Anti-tampering protection
• Automated meter reading
• Security
• Advanced billing
Of particular importance to the utility company is the tampering of meters. It is estimated that
millions of dollars are lost due to the tampering of these meters. Among the tampering are temporary meter
disconnect for a period of time before the readings are taken, the use of permanent magnets to saturate
current transformers and insertion of mechanical devices to slow down the mechanical turning of the disc.
Electronic energy meters are replacing traditional electromechanical meters in many residential, commercial
and industrial applications because of the versatility and low-cost afforded by electronic meter designs.
Single- and multi-chip meter designs are helping meter manufacturers and their customers realize these
benefits. Thanks to these continually evolving metering ICs, meter builders can implement many features
that were impractical with the older mechanical designs.
For example, an electronic design can protect against meter tampering and theft of service. It also can
measure and record energy usage at different times of the day, so utilities can bill customers for energy
based on time of usage. An electronic energy meter also can enable automatic meter reading (AMR),
whereby energy metering data is transmitted to the utility over an RF, power line or even infrared
communications link. Furthermore, electronic meters pave the way for “sub metering” of smaller operating
units (for example, metering each apartment rather than just the building).
Improved accuracy and lower power consumption are other benefits of electronic metering. With a
mechanical meter, the error in the basic energy usage measurement is on the order of 1%. But with an
electronic implementation, it is possible to reduce that error to less than 0.1%. Moreover, running the
mechanical meter with its continuously spinning dial may require hundreds of milliamps. That power
consumption can be reduced to a couple milliamps in an electronic energy meter, producing big power
savings for the utility. Electronic meter designs also change the economics of manufacturing energy meters.
A single hardware design may be customized for different customers and markets through changes in
software. In addition, calibrating the finished meter at the factory is much easier with an electronic meter
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design. Another consideration is the demand for mechanical-meter replacements that are as inexpensive as
possible. In parts of the developing world where many new customers are being connected to the grid, the
low cost of the electronic meter is its main attraction.
4.2 IC DEVELOPMENT:
Since the late 1990s, semiconductor vendors with mixed-signal and data conversion expertise have
been developing ICs for electronic energy metering applications.
In varying degrees, these components have integrated the energy measurement, calculation and
communication functions required to build electronic energy meters ranging from simple function,
mechanical-meter replacements to advance function all solid-state designs.
FIGURE NO: 4.1 IC DEVELOPMENTS
As in most areas of silicon development, the level of integration for these components grows with
time, so that newer ICs offer more functionality and/or less cost. Consequently, the cost of electronic
metering is coming down, which, in turn, is affecting the types of meters that are being built. As the
metering ICs evolve, there is also a trend to higher accuracy, which is reflected in the energy measurement
linearity of the new ICs.
The energy metering market is far from monolithic, so metering ICs target different applications.
One way to differentiate these chips is by the number of phases that must be measured. Some ICs target
single-phase applications, while others are crafted for multiphase (or poly-phase) applications. Within these
categories, the chips also are distinguished according to whether they target residential, commercial or
industrial applications. Another way to segment the energy metering ICs is according to the desired level of
meter functionality.
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FIGURE NO: 4.2 BLOCK DIAGRAM FOR POLYPHASE METER
4.3 CONSTRUCTION:
As in the block diagram, the meter has a power supply, a metering engine, A processing and
communication engine (i.e. a microcontroller), and other add-on modules such as RTC, LCD display,
communication ports/modules and so on.
The metering engine is given the voltage and current inputs and has a voltage reference, samplers and
quantisers followed by an ADC section to yield the digitized equivalents of all the inputs. These inputs are
then processed using a Digital Signal Processor to calculate the various metering parameters such as powers,
energies etc. The largest source of long-term errors in the meter is drift in the preamp, followed by the
precision of the voltage reference. Both of these vary with temperature as well, and vary wildly because
most meters are outdoors. Characterizing and compensating for these is a major part of meter design.
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The processing and communication section has the responsibility of calculating the various derived
quantities from the digital values generated by the metering engine. This also has the responsibility of
communication using various protocols and interface with other add-on modules connected as slaves to it.
RTC and other add-on modules are attached as slaves to the processing and communication section
for various input/output functions. On a modern meter most if not all of this will be implemented inside the
microprocessor, such as the Real Time Clock (RTC), LCD controller, temperature sensor, memory and
analog to digital converters.
4.4 WORKING:
Kilowatt-hour meter for determining, from voltage and current signals, the total energy passing
through an alternating electrical supply circuit comprises a clock signal generator for generating timing
signals at a frequency which is a multiple of the alternating supply frequency, the timing signals being
synchronized in phase with the incoming supply frequency, pulse sampling means controlled by said clock
signal generator and arranged to sample simultaneously the magnitude of the voltage on and the current in
said supply circuit at a predetermined time instant or instants in each cycle and digital data processing means
arranged to process the sampled data to determine energy consumption during successive predetermined
periods of time and to integrate the successive determinations of energy consumption.
Such an arrangement may be used with a three phase supply in which case the three phase voltages
and phase currents are separately sampled or it may be used with a single phase supply in which case only a
single voltage and current has to be sampled. The digital data processing means, which is typically a
microprocessor system, effects the required computations from the sampled values.
If a single phase supply is considered with the circuit carrying a current I at a voltage V and with a
phase lag (or phase lead) between the current and voltage of φ, then if the waveforms were sinusoidal, the
power consumption is VI cos φ. Conveniently, this can be measured by pulse sampling during the peak of
one of the waveforms. Preferably the measurement is made at the peak of the voltage waveform, so as to
determine the instantaneous peak value of V and of I cos φ. The r.m.s. product can be readily determined by
processing of this information. It may be preferred to average successive determinations of V and of I cos φ
separately over a number of cycles of the alternating supply frequency, typically a few hundred cycles,
before determining the product and hence the energy consumption during this period.
The output from the clock signal generator may be integrated, e.g. counted in a digital counter to
provide clock time. If a data link is provided, the aforementioned clock signal generator may be utilized to
provide clock timing for time-controlled operations, e.g. for example, the customer's data processing means
may compute monetary charges; to ensure correct clock time, the integrated output from the clock signal
generator may be periodically updated over the data link. It will be understood that such periodic updating is
required to correct the clock in the event of any interruption of the supply. Such a clock may be used, for
example, for effecting changes in the data processing related to absolute time; e.g. variation of charging rates
in accordance with time.
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FIGURE NO: 4.3 TESTING OF METER
4 .5 TESTING OF ENERGY METERS
The various tests performed on Energy meters are:
A. TEST OF INSULATION PROPERTIES
B. TEST OF ACCURACY REQUIREMENTS
C. TEST FOR MECHANICAL REQUIREMENTS
D. TEST OF ELECTRICAL REQUIREMENTS
E. TEST FOR ELCTROMAGNETIC COMPATABILITY
F. TEST FOR CLIMATIC INFLUENCES
A) TEST OF INSULATION PROPERTIES
1. Impulse Voltage Test
2. AC Voltage Test
3. Insulation Test
B) TEST OF ACCURACY REQUIREMENTS
1. Test on Limits of Error
2. Interpretation of Test Results
3. Test of Meter Constant
4. Test of Starting Condition
5. Test of No Load
6. Test of Ambient Temperature Influence
7. Test of Repeatability of Error
8. Test of Influence Quantities
C) TEST OF ELECTRICAL REQUIREMENTS
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1. Off power consumption
2. Test of Influence of Supply Voltage
3. Test of Influence of Supply Heating
4. Test of Influence of Heating
5. Test of Influence of Immunity to Earth Fault
D) TEST FOR ELECTROMAGNETIC COMPATIBILTY
1. Radio interference measurement
2. Fast transient burst test
3. Test of immunity to electrostatic discharges
4. Test of Immunity to Electromagnetic HF Field
(E) TEST FOR CLIMATIC INFLUENCES
1. Dry heat Test
2. Cold Test
3. Damp Heat Cyclic Test
(F) TEST FOR MECHANICAL REQUIREMENTS
1. Vibration Test
2. Shock Test
3. Spring Hammer Test
4. Protection against Penetration of dust and water
5. Test of Resistance to Heat and Fire
4.6 TAMPERING OF ENERGY METERS
4.6.1 TAMPERING METHODS
Tampering methods can be broadly categorized as
• Frauds related to meter installation/connections
• Frauds related to data
• Frauds related to meter installation/connections
Tampering methods generally employed to fraud the revenue meters can be categorized as
• Voltage circuit connection tampers
• Current circuit tampers.
• External tampers
• Alternate connections tampers
• Meter configuration change tampers
Tamper attempts are made to affect metering installation/connections. These are done at the metering
unit, cables, Test Terminal Blocks (TTBs) and meters. The tamper can be of a permanent nature, to steal the
energy continuously, or it may be through remote controlled devices, where the energy is stolen during the
period when the remote control device is activated. Such remote controlled tampering attempts are generally
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done in an intelligent manner, and it is difficult to locate such cases unless a vigilance team zeroes down on
the meters and carries out an installation audit.
The different methods for tampering are explained in following sections:
Voltage Circuit Tampers:
The different types of voltage circuit tampers are:
Phase and neutral interchange.
Looping of voltages
Phase association change between voltage and current circuits
Phase to phase interchange
Rotating phases in forward or reverse direction.
Voltage circuit disconnection (missing potential)
Disturbance on neutral.
Injection of high voltage DC
Injection of high frequency noise.
Shifting the neutral.
Voltage reduction
By injecting reverse voltage
Voltage circuit impedance changing
Neutral disconnection
Current Circuit Tampers:
The different types of current circuit tampers are:
Reversing current circuit (CT reversal)
Reverse current injection
Earthed loads
Current circuit open
Current circuit by-pass / shorting
Current imbalance
Rectifier load
CT saturation
CT secondary burden change
Over burdened CT secondary
Current circuits in series (3P3W meter)
Excessive burden
Higher CT rating
Wrong CT ratio
External Tampers:
External tampers are caused by:
Abnormal magnetic influence
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High temperature
Chemical injection
Burning the meter
Alternate connections tampers: These are caused by/at:
Mobile substations
Direct taping
Meter configuration change tampers:
These types of tampers are created by:
Adjusting the calibration
Changing the time of the meter
Resetting or altering energy registers.
Resetting or altering maximum demand and/or billing registers
Changing the values for meter’s CT and/or PT ratios
Changing meter configuration, DIP, kVA definition etc.
Frauds related to data:
Frauds related to data cover the following:
Noting meter readings incorrectly
Resetting Maximum Demand and/or making adjustments
Coffee shop reading
Unauthorized downloading of data from meter
Altering/modifying data at source or at the billing centre
Meter spoofing
4.6.2 TAMPER DETECTION AND REVENUE PROTECTION MEASURES
Metering technology has a seen sea change to suite the utilities requirements for revenue protection.
With the advent of electronic metering, it has been possible to detect various tampers. The technology is
keeping pace with the newer methods of tamper and various features are developed in electronic meters to
cater to these ever changing needs.
Various principles deployed for different tamper methods and are follows:
Prevention method
Here, steps are taken to make the metering installation secure from unauthorized access. This is done
by providing proper seals on meters, and a more effective method is to mount the metering equipment inside
a box or cubicle, which can be locked/ sealed.
Detection method
Technical methods to subject possible frauds to detection are now being programmed in intelligent
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electronic meters. These capabilities are built into the new generation of meters. More and more of such
detection methods have been possible as and when the meter industry has come to know of the newer
methods of tampering.
Connection frauds are basically detected by the position of the current and voltage vectors, where the
logic deployed is to detect illogical electrical conditions. Normal conditions are defined as set of electrical
conditions and tamper conditions are defined as set of electrical conditions beyond certain threshold limits.
Hence the change of electrical conditions beyond the designed threshold limits can be detected by the meter.
Transition from normal conditions to tamper condition and vice-versa, i.e. tamper conditions to normal
conditions, are detected as occurrence and restoration events for each type of tamper.
Method to create evidence
Creating an evidence for a tamper is one of the methods. For creating evidence, tampering attempts
are detected by the meter (based on tamper logics) and recorded in the meter memory together with a date
and time stamp. The occurrence and restoration events in form of snapshots are logged and a chronological
record is logged in the meter. This record can produce evidence for assessment of theft (known as
“assessment”) and deciding on penalties (known as “settlement”). Nearly all types of connection related
frauds are detected and logged in modern meters.
Isolation method
“Intelligent” electronic meters are designed to isolate some methods of tampering, like neutral related
tampering.
In the past, electronic meters invariably stopped when the neutral connection was removed. The new
generation meters are now designed to work on any two wires. If neutral is removed or one neutral and
phase wires are removed from the meter terminal, the meter will continue to function normally and record
the energy as per prevailing electrical conditions. The injection of external signals through the neutral wire
(like DC & high frequency signals which can affect the meter functioning) can now be detected by the meter
and the signals can be filtered by the meter to make it immune to such signal injection.
Deterrence method
Attempts to tamper with the electricity meters are basically by people with malafide intentions. The
entire effort is aimed at stealing energy so that they do not have to pay for it. Generally, when such attempts
are detected the consumers are penalized. An effective alternative is to discourage such attempts. In the
“deterrent method” the meter detects the tamper attempt and records higher energy than normal consumption
by self-introducing positive errors. This method is employed for magnet related tampers. Tamper evidences
are also produced along with excessive energy recording.
Deficiency metering
Certain types of connection frauds can be detected and “self-corrected” by the meter. By using this
self-correction feature, the meter can compute the loss of energy on line. In addition to this self correction,
the tamper attempt is also logged as an event to provide evidence.
In case of 3 Phase 4 Wire meters, one current circuit reversal can cause less recording of energy.
Electromechanical meters had reverse stop feature to prevent the meter to run in reverse direction under
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current reversal condition. Electronic meters can detect such reverse current flow and continue to record the
energy in forward direction.
Audits
Audits for the quality of installation and energy & revenue audits are other mechanisms to detect and
address tampering. This is a vast subject by itself.
4.6.3 REVENUE PROTECTION FEATURES
Unlike electromechanical meters, electronic meters have a number of hardware features for revenue
protection, based on the product type and application. These hardware features support the necessary
software features to provide evidence for tampers, and its necessary deterrence etc.
Revenue protection features in meters can be viewed as:
Hardware features
Software features
(A) Hardware features for revenue protection:
The hardware features generally provided for revenue protection can be examined for
a) Single phase meters.
b) Three phase meters.
a) Hardware features in Single Phase Meters:
Most of the connection related (or wiring related) frauds/tampering are taken care of in the hardware
design. Intelligent microprocessors used in electronic meters provide “deficiency metering” so that the meter
is capable of measuring the correct energy under certain types of “deficiencies” in the connections.
The hardware features provided for revenue protection for single phase meters are:
Double current sensors
Electronic Display
Optical reading
Features to deter magnetic field based frauds
Features to prevent breaking open the meter case
Each of these is explained below:
Double current sensors
Electronic meters are provided with two current sensors for meeting the requirement of normal
measurement and deficiency metering. Here, the current is measured in the phase circuit as well as in the
neutral circuit, and the higher of the two currents is internally used by the meter for calculating the power,
energy, etc. computation.
Most of the connection/wiring related frauds are taken care of by the above method. two current
sensors. The possible connections tamper conditions are shown in annexure 1.
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Electronic Display
Meters with counter type display are prone to display related errors and defects. Some electronic
meters use a stepper motor or impulse counter type display. These are easily influenced by external
influences like magnetic fields; bringing a magnet in close proximity to the meter will affect the functioning
of the display and altering the reading of meters is possible.
These problems are overcome by providing electronic display in the meters, like LED, LCD display.
Optical reading
One of the many causes of loss of revenue, and a significant cause, is errors or frauds in meter
reading (by meter readers). This problem can be eliminated in electronic meters by having a mechanism for
optical meter reading. Here, the meters are provided with an optical port for transferring meter data (i.e.
meter readings) to hand held electronic devices like hand a computers or CMRI (Common Meter Reading
Instrument). As the manual reading & noting of meter readings by a meter reader is eliminated, these types
of data errors or frauds can be eliminated.
Features to deter magnetic field based frauds
Normal magnetic fields do not affect the performance of a meter. However, if we subject the meter to
very strong magnetic fields (like bringing a powerful magnet close to the meter), the meter will
register/record a much lesser energy. Modern electronic meters can be made to record a much higher energy
(instead of a lesser energy) under such influence, thereby deterring such frauds.
Features to prevent breaking open the meter case
Opening the case (or cover) of a meter and making modifications inside the meter, tampering with
the hardware/implanting radio controlled switches, adjusting the calibration etc. are known methods of
tampering. These tampers are hard to detect, as there is not external evidence of tampers.
A method to deter such tampering is to make the meter case in such a manner that anyone who tries
to tamper cannot open the meter case without damaging the meter. Ultrasonic welding of meter, with base
and cover with snap fit arrangements in meter case, is an effective method to prevent this type of fraud. In
case someone tries to break open the meter case, the meter cover/body will show damage marks and provide
physical evidence that the meter has been tampered.
b) Hardware features in three phase meters
The hardware features provided for revenue protection for three phase meters are described below.
These cover all types of three phase meters namely LT whole current meters, LT CT meters, and HT meters
(i.e. CT/PT connected meters)
The hardware features provided for (or linked to) revenue protection for three phase meters are:
Two wire operation features
4th current sensor for LT meters
Phase to phase protection
Features for Real Time Clock
Magnetic influence detection
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Optical reading port
Transparent terminal block covers
Front sealing
These are explained below:
Two wire operation features
In two wire operation features, the meter is made to function as along as any two live wires are
connected to the meters. That is the meters will function even if any phase or neutral is missing from the
meters. This may not make accurate energy recording possible, but the meter will remain powered to log the
tamper event with date/time stamp, and the electrical snapshot as evidence.
4th current sensor for LT meters
Three sensors are used for energy measurements for 3 element meters (i.e. 3 phase 4 wire meters).
Generally three sensors are used, with one sensor for each of the three phases. However, to detect current
circuit tampers, advanced electronic meters have a fourth sensor used in neutral circuit.
Current circuit tampers like CT reversals can be detected with three current sensors. But in case we
rely on only three current sensors, there can be a zone of operation possible which may not be due to tamper
conditions but will appear to be a tamper. This makes it difficult to detect genuine tampers, and ignore
conditions that are not really tampers. Hence the 4th sensor helps in arriving at unambiguous tampers.
The principle of operation for the 4th sensor based hardware, is explained in later sections. Use of
correct installation practices are necessary for 4 sensor meters, to prevent false tamper alarms, which may
came about in case a consumer uses phase to ground loads (in place of phase to neutral load). It is worth
noting that load unbalance conditions can be distinguished from current circuit tampers by use of the 4th
sensor.
Phase to phase protection
There are enough reasons to damage the meters intentionally by making wrong connections. This is
true particularly with LT meters where phase and neutral is swapped and meters get damaged. The
protection eliminates such possibility and avoids damage due to system faults.
Features for Real Time Clock
The Real Time Clock (RTC) provided in electronic meters is used to record the date/time stamp for
occurrence & restoration of tamper conditions, thereby providing time-base evidence.
The RTC is otherwise an essential part of electronic meters as it provides the time reference to the
meter. The meter is able to provide various time based features like billing data, Maximum Demand
registers, tamper event logging with date and time, recording load survey etc.
Magnetic influence detection
Magnetic material used in meters can be affected by abnormal external magnetic influences, and this
will affect proper functioning of the meter. For example, the CTs used in meters (for sensing currents) are
affected by magnetic influence. The effect is either change in magnitude of primary or secondary current,
which in turn can introduce large errors in measurement. Magnet sensors provided in modern electronic
meters can detect the presence of abnormal magnetic fields and provide evidence by logging it as a tamper.
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Optical reading port
The optical port enables the data transfer electronically and eliminates the possibility of data frauds,
as explained for single phase meters.
Transparent terminal block covers
Making the terminal block cover of a transparent material is one of the ways to keep connections
“visible”. This meter reader or vigilance team can observe connection/wiring related frauds without the need
for opening the terminal cover.
Front sealing
The rear side sealing arrangement of a meter is generally difficult to check. It is recommended that
electronic meters should be provided with front side sealing arrangements, so that the seals are clearly
visible, easily accessible and periodically auditable.
(B) Software features for revenue protection
Software features programmed in electronic meters enhance the capabilities of electronic meters.
Revenue protection related software features make the meter more versatile. The various software features
are described below:
Billing data with billing date
Load survey
Tamper event logging
Tamper event type
The details are given below:
a) Billing data with billing date
Adjustments in minimum charges and false resetting of the MD (Maximum Demand) potential
tamper possibilities in meter reading. It is difficult to spot such errors by energy audit methods as
simultaneous readings of all meters connected to a feeder are never read at the same time.
This problem can be addressed by incorporating logic in the meters so that the MD of all meters is automatic
reset on a pre-programmed date/time of a month. Here, there is a copy operation too, where the energy
reading is copied to a billing registers on the predefined date(s). With these arrangements, the meter reader
can take the reading any time (between two consecutive billing dates) and obtain the billing parameters
pertaining to the pre-defined date.
Apart from the meter billing data, history of previous billing data can also be stored in the meter
memory. Six or twelve history data can be stored for future reference and settlements. This is a useful
feature and is at times used by utilities in case last billing data has been lost/corrupted while transferring the
meter data to billing centres.
A month by month energy comparison is possible with these features and deviation in energy
consumption from predefined limits (or abnormal change in consumption trends) can be found at billing
station for investigating tamper possibilities.
b) Load survey
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Profiling of the average load values over the time of day, at pre-decided intervals of time is called
load survey data. The average load for the interval duration is recorded on a real time basis. This interval
duration for the load survey data, is referred to as Survey Integration Period (SIP) and energy or other
averaged parameters are recorded for each SIP. Typically the Survey Integration Period is ½ hour, but SIP of
¼ hour (i.e. 15 minutes) is also used. In earlier days, some meters logged the load survey parameters on an
hourly basis. This SIP may or may not coincide with the Demand Integration Period (DIP) used for the MD
& other purposes, though generally most SIPs are same as the DIPs.
Load survey parameters are averaged quantities like active energy, reactive energy, average voltage,
average power factor, etc. or instantaneous parameters like voltage, current, frequency etc. at a predefined
instant during the SIP interval. These load survey parameters can be configured in the field, but through
proper authentication and sufficient software security arrangements.
The load survey data is utilized for a number of purposes like assessing pilfered energy (in case of
tampers), identifying the number times the MD has been violated, day-wise, week-wise & month-wise
energy accounting or computations, identifying the power ON/OFF events and comparing with other
consumers on the same feeders, arriving at power quality like voltage conditions at consumer-end etc.
Experience has shown that load survey information has been a very useful feature of electronic meters for
utilities.
c) Tamper event logging
Frauds/tampers related to the way the meter is wired (i.e. connection related frauds) are detected by
electronic meters and logged as an event in the meter’s memory. Once an event is detected, not only the
occurrence of event is logged, but the restoration of the event back to normal conditions is also logged
together. The number of such events that can be logged by a meter is generally limited by the memory sector
allocated for the purpose. Hence there is a need to clear the event logs (i.e. record of such events) on a
periodic basis – typically during the next meter reading, so as to make space for newer events.
Various options/features are provided for event logging. These are:
Event logging type
Compartment wise events
Snapshots of electrical parameters
Event logging type
Two types of event logging are generally implemented. One type is a “stay put” type, and the other
type is a “rollover” type.
In the “stay put” type, events are logged in memory until the memory is full. Once the memory is filled up,
in the “stay put” logic, the new events are not recorded.
“Stay put” type event logging is less preferred since the tamper logs need to be reset after the memory is
full. Another reason why the “Stay put” type is not preferred is that in this type of logic the entire tamper
data can be lost when reset, thereby removing all evidences of tampers.
In the “rollover” type, events are logged in memory until the memory is full (i.e. similar to above), but
with a difference. The different is that once the memory is full, the new events are recorded by over-writing
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the oldest records. In his type the recent tamper events are not completely lost.
Apart from logging the “events” a count of the tamper events is also maintained by the meter. This
tamper count is based on the occurrence of similar events, and there can be different counters for different
types of events. The billing data tamper count values can be utilized to identify the total number of tamper
attempts made in the previous month/billing period.
Compartment wise events
Different memory compartments are allocated for different types of tampers, so that a few frequently
occurring tampers will not over-crowd the memory and over-write other types of tampers.
For example, suppose a missing potential tamper or a current circuit reversal has been recorded as an
event by the meter, corresponding to a genuine tamper event. Suppose there were no separate memory
compartments for different types of tampers, there will be a possibility that these tampers information will be
over-written by the Power ON/OFF events or current imbalance events if these latte happen too frequently.
By having different compartments for different types of tampers, and by allocating fixed memory (or
number of each type of events the meter can record), we can cater to such eventualities. It is very desirable
to keep a record of each type of event the meter has encountered, while allowing for logging latest events.
Each compartment is of a “roll over” type, and thus maintains latest and important information about
attempts to tamper.
Snapshots of electrical parameters
The tamper events are supported by a snap shot of electrical parameters. Instantaneous value of
electrical parameters at the time of detecting occurrence or restorations is called as snapshot. The electrical
parameters are voltage, current and power factor with appropriate sign are logged as snap shot.
Energy values are also logged at the time of event logging.
The electrical snap shot is used for assessment of theft, vector analysis of tamper condition etc.
d) Tamper event type
Various tamper conditions are identified by examining the electrical conditions, and each abnormal
type of electrical conditions is stated to be a tamper.
Threshold values are used by the meter to define a tamper, or an abnormal electrical condition.
Careful specification of these threshold limits is an art, and effective tamper identification is dependent on
how thoughtfully these threshold values have been arrived at. The threshold values are needed at the
manufacturing stage.
The following types of events (tampers) are dealt with in this paper:
Missing potential
Invalid voltage
Voltage imbalance
Current reversal
Current circuit bypassed
Current imbalance
Magnetic influence
Neutral disturbance
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Current circuit open Power On/Off
The tamper type and related logic for each of the above is described below:
Missing potential
In this type of tamper, the voltage component in is made zero. Accordingly the power computed by
the measuring element becomes zero, and the energy recording is less by one phase.
This is a common connection fraud usually deployed in meters. Dropping the potential links in the
whole current meters, removing the potential leads from meter terminal, TTB or metering equipment
terminal fall under this tamper type.
The logic steps to detect this type of tamper are explained below:
If voltage is absent and current is present, the logic senses a possible tamper condition, and examines the
next possibility to re-confirm itself
If current and voltage both are missing than this could also be a system condition, and hence not
recorded as a tamper
If however voltage is less than Vth (Where Vth is the threshold value of voltage set for the tamper), and
line current is more than Lth. (Where Lth is the threshold value of the line current), the condition is
recognized as a tamper, but it is logged as a tamper only if it passes the next logic step
If this tamper condition persists for a pre-defined persistence time, the event is finally logged as a
tamper. Once this tamper is logged, the corresponding tamper count is incremented.
The tamper is restored when voltage restores to more than the preset restoration threshold value.
The normal voltage value (i.e. the restoration voltage value) is now monitored, and if it remains above this
value for a predefined persistence time, the tamper is considered as restored
Invalid voltage
When one voltage is fed to all voltage terminals or two voltages are shorted and connected to one
voltage input, the condition is different from missing voltage, but yet it is a tamper because the voltage
angles are no more valid. In tamper logics, this condition is detected and classified as “invalid voltage
input”.
The logic steps to detect this type of tamper are explained below:
If Voltage is more than Vth.
And if, Voltage angles are not valid
And if, the condition persists for more than persistence time, the event is recorded as a tamper
Once this tamper is logged, the corresponding tamper count is incremented
The tamper is restored when voltage angles have being restored to their logical values for more than the
preset restoration threshold value
Voltage imbalance
Voltages are normally balanced. However there may be some unbalance due to loading conditions
which may not be a tamper.
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But, by tinkering with electronic components, or making a wrong connection like swapping the phase
wire with neutral wire etc. one may cause a voltage imbalance being recorded by the meter.
Compute voltage imbalance with respect to maximum voltage
Check if Imbalance is more than V imbalance is more than the threshold value set for V imbalance
.Monitor the condition for persistence time and log tamper event & increment in tamper count
The restoration logic is similar to that defined for other types of tampers – i.e. restoration of normal
conditions for a persistence time
Current reversal
Under normal loading conditions and connections, current vector cannot move beyond 90 lag or lead
with respect to voltage vector. However due to some system conditions the current vector may go beyond
90. As most electricity consumers do not generate electricity (or if backup generator is installed they do not
operate it in synchronism with utility supply system), the net active power cannot be negative.
However, if someone tampers with the connections and reverses the current polarity (in one of the
terminals), it is possible that the current vector will move beyond 90 with respect to voltage vector.
This vector position is used by the meter to identify a “current reversal” tamper. As system
conditions may overlap with reverse current condition, to eliminate the possibility of system conditions a 4th
sensor in form of an internal CT is used inside the meter to sense a neutral imbalance current. Now, under
these circumstances the vector sum of three phases and one neutral current determines the abnormality in
current circuit.
Complex logics are used to detect whether this is a tamper (or not), and this is done by examining the
current vector in pre-defined zones to detect whether the current has been actually reversed.
The logic steps to detect this type of tamper are explained below:
Check normal three phase voltage
Check if any current has a negative polarity (from vector position)
Then check If line current is more than Lth (line current threshold)
Check if the 4th CT flag has been set
Check if power factor is more than 0.1
Check whether these conditions persist for persistence time
Log occurrence of event as a tamper and Increment tamper count
If the current now becomes positive once again for the pre-defined persistence time, than log restoration
of the event.
Current circuit open
This is a new method of tampering the current circuit. The current is bypassed or secondary circuit is
made open in such a way that current is flowing in the load circuit but does not flow into the meter circuit.
As genuine no load conditions are not really tampers, the condition has to be recognized by the meter
for detecting this tamper. A 4th sensor (4th CT in neutral) is necessary for detecting this type of tamper.
The logic steps to detect this type of tamper are explained below:
Normal three phase voltage are present
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Now, if vector sum of currents is not zero
And, difference current is more than Lth
Then, the 4th CT flag is internally set by the meter
Check if none of the current is negative (from vector position)
Check whether line current is less than Lth open.
Check whether this condition persists for persistence time, then record “current open” occurrence event
Increment the tamper count for “current open”
For restoration, check if the 4th CT flag is reset
Check whether average line current is more than Lth
Check if these restoration conditions persists for the pre-defined persistence time
Log the event as a “current open” restoration event
Current circuit bypassed
While tampering with this method, consumers put a small shorting link across the meter current
circuit. The shorting can be made any where in the current circuit like in the primary circuit of CTs,
secondary circuit, inside the meter etc. While doing so some amount of current is flowing in the meter is
measured, but a substantial part of current is by passed and does not flowing into the meter. Thus the meter
will record less energy.
The 4th CT is essential to detect this type of tamper. Delta connected HT systems which use 3 phase
3 wire metering (2 element metering) and therefore take currents from two phases are incapable of detecting
this type of tamper. Only in case of 3 phase 4 wire metering (where 3 CTs or 3 current paths are externally
available) can support this type of tamper recording.
The logic steps to detect this type of tamper are explained below:
The meter first checks if normal three phase voltages are present
The current vectors are summed, and the meter checks if the difference is more than Lth
The meter first checks all logics for current reversal and current open tampers. If they are not, then….
If the condition persists for persistence time the event is logged as a “current bypass” tamper & the
tamper count is incremented
When the occurrence condition is restored, the restoration event is logged after persistence time has
elapsed
Current imbalance
The traditional method of detecting the current open or by pass tamper was to measure current
imbalance. As some current imbalance is always there in the system, current imbalance tampers, which can
be caused by partial bypassing of current, is difficult to detect.
Certain intelligent logics have been developed to detect this type of tamper. This method is generally
used for 3 phase 3 wire meters only, as for 3 phase 4 wire meters the current bypass logic is sufficient.
The logic steps to detect this type of tamper are explained below:
The meter first checks if normal three phase voltages are normal
The meter checks if line current is more than Lth (for imbalance)
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If the Current imbalance is more than Imbth
If the conditions persist for the persistence time, the event is logged as a current imbalance tamper event
and the tamper count is incremented
When current imbalance becomes is less than threshold value and remains for the persistence time, the
event is restored
Magnetic influence
Magnetic effect on metering equipment was studied by various utilities. It was seen that strong
permanent magnets are available in the market, and over a period of time even stronger magnets are now
available. Today, even strong AC electromagnets are being used for tampering meters.
Meters use magnetic material in voltage and current measurement circuits. The power supply also uses small
transformers which are susceptible to magnetic fields. Functioning of sensors or power supply components is
affected under abnormally high magnetic fields. The effect is generally to saturate the core of the sensors or
distort the flux in the core so that output is erroneous. The net effect is less energy recording.
Counter type electronic meters using impulse counter or stepper motor type counters are seriously
affected by strong magnetic fields. These can either be stopped or rotated in any direction to change the
energy register values.
The effect of magnetic fields can be suppressed or substantially reduced by increasing the gap
between the sensors and magnet, or by shielding the sensors.
New generation electronic meters have capability to detect the presence of abnormal magnetic field
in the vicinity and log the event as a “magnet tamper”. To deter the consumer from magnet related
tampering, a method now used is to increasing the energy recording by the meter under these conditions.
Thus, once the purpose of tampering is defeated and consumer does not attempt tampering with this method.
Neutral disturbance
Neutral related tampering is often done by consumers by tampering with the neutral at source side
i.e. before the meter. Disturbances like DC voltage or HF signals are superimposed on neutral wires causing
disturbance to the metering process. This tampering may reduce the energy recording or stop the meter
functioning altogether.
Electronic meters are now designed to detect such disturbances and isolate the neutral connection
internally in the meter, and continue to record normally by creating an artificial neutral.
As this condition can be sensed by the meter, as a deterrent the meter can be made to run at the
Imaximum current, together with an event record that the meter has been tampered in the neutral.
Power On and Off
Meters are powered Off by removing all the voltage connections or by other means. To make such
information available to the utility, the meter records power failure and power up condition as power OFF
and ON events.
These events can be compared with power failure records from the substation or feeder meter data
(or by comparing with neighbouring consumers). The event date and time logging is enough to identify these
abnormal power failures and its duration.
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4.7 SYSTEM CONDITIONS
The detectable and undetectable tampers need to be dealt carefully. Software and hardware logics
work to certain extent to declare the conditions as a tamper. However, due to a variety of field conditions,
not all cases of tampering can be detected with certainty. The unambiguously identifiable tamper conditions
are called detectable tampers.
Some system conditions may reflect as tamper conditions and vice versa. Most of the system
conditions are taken care by intelligent tamper logics and by carefully selecting the tamper threshold limits.
Tamper threshold limits also depends on installation practices, system conditions and conditions which need
to be defined as tamper. Like fore example, single phasing conditions or 2/3 connections on HT side are the
system conditions and need not to be detected as tampers. Some of the installations have PT primary side
fuses. There may be PT primary fuse failures which are not really tamper but cause revenue leakage.
Connection (i.e. wiring) related tampers are intended to reduce the recording or stop it altogether.
These are detected by software logics vector positions and thresholds. The vector positions are very much
dependent on system conditions are well as the combination of various tampers.
The system conditions and configurations which are responsible for overlapping with tamper conditions (and
hence difficult to detect) are as follows:
Source transformer
Secondary Star
Secondary Delta
Source neutral grounded
Source neutral ungrounded
Line fuse failure
2-by-3 connections
Single phasing
Metering PT
Star-Star
Delta- Delta
Star point grounded
Star point ungrounded
Type of Metering
3 Phase 3Wire
3Phase 4Wire
PT primary fuse failure.
Load / distribution transformer
Star - Star
Delta - Star32
Delta - Delta
Load condition
Inductive load like welding transformers
Balanced
Unbalanced
Capacitive load
Faulty capacitor
Capacitor fuse failure
Phase to phase loads
Earthed load
Combination of all above system conditions
4.8 AUTOMATIC METER READING (AMR)
4.8.1 What is Automatic Meter Reading?
Automated Meter Reading (AMR) refers to the technology used for automating collection of water
and energy (electricity or gas) consumption data for the purposes of real-time billing and consumption
analysis. At any given time, the AMR system gathers real-time data and transfers the information gathered to
the central database through networking technology.
This advance mainly saves utility providers the expense of periodic trips to each physical location to
read a meter. Another advantage is billing can be based on near real time consumption rather than on
estimates based on previous or predicted consumption. This timely information coupled with analysis, can
help both utility providers and customers better control the use and production of electric energy, gas usage,
or water consumption.
AMR technologies include handheld, mobile and network technologies based on telephony platforms
(wired and wireless), radio frequency (RF), or power line transmission
4.8.2 Issues with Stand Alone Meter Reading:-
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• Highly Person dependant.
• Human errors cannot be avoided.
• Accessibility of meters in rural/ Agricultural zones.
• Energy Audits performed based on bill collection which is highly inaccurate.
• Billing done mainly on estimated/ monthly average basis
• Inability to monitor and control discrete loads
• Billing cycle requires excessive time.
• Meter data used only for billing, cannot help in analysis like demand analysis, energy audit etc.
CONCLUSION
Electronic meters are capable of dealing with a very wide range of tampers. To enable proper tamper
logging, it is worth having 3 phase 4 wire meters (3 element meters) wherever possible, as this will enable
the 4th sensor to identify a range of tampers. Special care need to be taken for selecting the threshold limits,
as effectiveness of tamper logics depends to a reasonable extent on these threshold values.
Tamper recording features need to be backed with (i) suitable mass data and tamper data analysis
software, and (ii) feeder-wise& distribution transformer wise energy audits. These will help in filtering out
temporary conditions (which might have been caused due to system conditions. The energy audits will fill in
the gaps. Energy audits together with tamper logics in meters is a must, and this will help provided the
system (feeder) meter & distribution transformer meter functional specifications have been carefully selected
to support energy audit & correlated tamper analysis. Correlation of the tamper events, mass tamper & load
survey data analysis and energy audits only when considered together will provide a comprehensive revenue
protection to the utility.
SUMMARY
During this complete training, I got well versed with various electrical devices and circuits. Besides
this, I did a deep study about the various methods of theft of electricity and also the techniques used to
control such theft, the various latest trends in technology used for energy meters to get an accurate energy
measurement.
Once the Energy meters were deeply studied, I gained knowledge about various other products
manufactured by the company like MCB’s, Monoblock Pumps, Ceiling Fans and Motor Starters etc.
All in all this training has been really beneficial for me in gaining vital practical knowledge about
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various devices and circuits in the field of Electrical and Electronics.