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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. 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

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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

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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

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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

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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

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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.

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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.

REFERENCE

WWW.SKNBENTEX.COM

WWW.4SHARED.COM

WWW. WIKIPEDIA.ORG

WWW.SCRIBED.COM

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