PREFACE

This report comprises of all the sessions of training, I have been through in the duration of four weeks during vacations.

I visited MPMKVV Co. ltd.(Madhya Pradesh Madhya Kshetra Vidyut Vitran), a govt. undertaking company dedicated to distribution of Power and Tariffing .The City Circle is divided in four zones and its one of the premier company of MPSEB (Madhya Pradesh State Electricity Board ), which focuses ob providing the best services to the consumers that include quality and reliable supply of power, quicker attention to fuse-off calls and billing related problems.

There are one 220/132KV substation, three 132/33KV substations, twelve 33/11KV substations in City circle (west zone). Substations of each category were visited where I was made aware of all the equipments installed there, their controlling and the distribution system functioning. I also had one week visit of Transformer repairement unit, Energy meter testing lab of MPMKVV Co. ltd. were informative knowledge about the devices was given.

We also were made familiar with the general way of conduct with the consumers of the company, how to handle their problems and entertain up to the possible satisfactory level.

The overall experience was very informative.

ACKNOWLEDGEMENTS

Practical training is an important aspect of an engineering curriculum as it enables to understand the practical application of the theoretical concepts that were learned during academics. It acquainted the student with the latest advancement in the field of technology & engineering.

To get this training completed we are thankful to Mr. K.K. Dubey (EE,Training cell) ,Mr. Amrit Tiwari (AEE) ,Mr. Manoj Kelkar (AEE), Mr. Shivram Solanki (Supervisor,Transformer repairment unit) and all the employees if MPMKVV Co. Ltd. who shared their knowledge zealously. We are thankful to Prof. K.S. Sandhu (H.O.D.,Electrical Dept.) for providing us opportunity to undergo this training session during vacations at MPMKVV Co. Ltd.

I want to convey my sincere note of thanks to all Professors and lecturers of Electrical Dept. NIT Kurukshetra , for being a key guide and kind support.

CONTENTSForwarding letterPrefaceAcknowledgements

1. Electrical Energy Meters

Introduction

Types of meterso Electromechanical meters

o Mechanism of electromechanical meters

o Solid state electronic meters

Testing and calibration

Domestic and Industrial energy meters

2. Electrical Substations

Introduction

Transmission substations

Distribution Substations

Switching Function

Equipments installed

Capacitor bank Charging unit

Tasks performed by substation staff

3. Transformer testing and repairment

Introduction

Basic Principle

Induction law

Practical considerations

Effect of frequency

Energy losses calculations

General faults

Transformer oil testing

Instrument transformers

Accessories of transformers

4. Functions and tasks performed by MPMKVV Co. Ltd.

Introduction

Electrification of new localities

Load surveys

Tariffs

Action against electricity theft

Minimization in transmission losses

ELECTRICAL ENERGY

METERS

INTRODUCTION

An electric meter or energy meter is a device that measures the amount of electrical energy consumed by a residence, business or an electrically powered device.

Electric meters are typically calibrated in billing units, the most common one being the kilowatt hour. A periodic reading of electric meters establishes billing cycles and energy used during a cycle.

In settings when energy savings during certain periods are desired, meters may measure demand, the maximum use of power in some interval. In some areas, the electric rates are higher during certain times of day, to encourage reduction in use. Also, in some areas meters have relays to turn off nonessential equipment.

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.

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. By convention, a "lagging" or inductive load, such as a motor, will have positive reactive power. A "leading", or capacitive load, will have negative reactive power.

TYPES OF METERS

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.). Meters for smaller services ( such as small residential customers) can be connected directly in-line between source and customer. For larger loads, more than about 200 amps of load, current transformers are used, so that the meter can be located other than in line with the service conductors. The meters fall into two basic categories, electromechanical and electronic.

Current transformers being used with meters

ELECTROMECHANICAL METERS

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 energyused over a period of time.

The type of meter described above is used on a single-phase AC supply. Different phase configurations use additional voltage and current coils.

The aluminum 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. 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 . 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 . Where the meter reader reads the meter, the reading may be supplied to the power company by records, post or over the internet. The electricity company will normally require a visit by a company representative at least monthly in order to verify customer-supplied readings and to make a basic safety check of the meter.

In an induction type meter, creep is a phenomenon that can adversely affect accuracy, that occurs when the meter disc rotates continuously with potentialapplied and the load terminals open circuited. A test for error due to creep is called a creep test.

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energy meters

MECHANISM OF ELECTROMECHANICAL ENERGY METERS

The key point: metering is based on the product of two electrical entities, current I and voltage V; power is the product of these two entities, V and I. Energy is calculated integrating over time (that is adding together time after time) the V*I products. It is energy what we are paying for. Within electromechanical meters V and I feed two coils: the voltage coil (which is in parallel tothe line) requiring low power and a current coil (in series with the line) made of thick copper wire. Metering can be stopped or started interrupting the connection to the voltage coil.

Internal assembly of a electromechanical energy meter

The meter has two coils in it, one responsive to voltage, the other to current. They are arranged so that the torque they apply to the disc is proportional to the voltage times the current times the cosine of the phase angle so that the disc only responds to active power (kWh) and not to reactive power (kVAR). The device works upon induction principle with current coils and the torque is produced in the aluminium disc and the dials records the energy consumed.

SOLID STATE OR ELECTRONIC ENERGY METERS

Electronic meters display the energy used on an LCD or LED display, and can also transmit readings to remote places. In addition to measuring energy used, electronic meters can also record other parameters of the load and supply such as maximum demand, power factor and reactive power used etc. They can also support time-of-day billing, for example, recording the amount of energy used during on-peak and off-peak hours.

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 digitalised 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.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 addon 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.

Electronic meter possess a microprocessor and interfaced by a Programmable Periphral Device which receives its Input from Two CT's, one is on the phase & the other is on the neutral,the PPI recieves signals from both CT,s but it reads whichever the current is greater & a V.T. is positioned in the casing of Energy meter of which outputs is fed to PPI so the proceessor reads V from V.T.,I(depends on Power Factor) from C.T. so their product is seen on the

digital screen of the Meter.