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TRANSMISSION AND DISTRIBUTION LOSS MINIMISATION

PREM K. KALRA

DEPARTMENT OF ELECTRICAL ENGINEERINGINDIAN INSTITUTE OF TECHNOLOGY KANPUR

Electricity

n Think about the world without electricity:n Do bulbs glow?n Can we watch Olympic matches or movies on TV?n Our daily life is affected by electric power.

n Electricity should possess not only quantity but also quality and reliability.

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Distribution Systems

n Classical Electricity Distribution Networksn Reliability,n Availability,n Maintainability.

n Distribution Generation

n Call Centres for Consumer Caren Quality of Service

ISSUES

•Design: Centre of Gravity of Load, Conductor Size

•Operation: Three Phase balancing ,Harmonics

•Integrated Resource ManagementLocal vs. Global solutions

•Supply side and Demand side Management

•Consumer Participation

•Efficiencies: Tariff Structures, Planning

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Sources of Losses

n Ignorancen Uncertaintyn Upgradation of

Human Resourcesn Indisciplinen ABT

n Poor Tariff Structures

n Technical n JOINTSnNeutral Conductor Sizen Length Of the Line

n Energy Auditn Energy Managementn Energy Forecast

Electricity and India

n The frequent power cuts, less reliability and poor quality of supply result to great loss of economic and personnel growth.

n For the development of a country power is the key component.

n National goal is to provide reliable, affordable and quality power to all by 2012.

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Facts about Electricity

n Electric power can not be stored to a large extent.

n The demand of power varies through out the day and can not be predicted accurately.

n Electric power is the optimal choice of energy as it can be transmitted efficiently and can be converted into other forms as required.

n Electricity follows the path of least resistance.

Problems of Indian Power Sector

n Low plant load factorsn Lack of optimization of generationn Frequent load sheddingn BrownoutsnHigh T & D losses (technical and commercial

losses)n Poor quality of power supplyn Poor collection efficiency

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Electricity Losses

n Technical losses

n Transformer and line losses due to poor maintenancen Unbalanced loadingn Losses due to overloading and low voltagen Losses due to poor standard of equipmentsn Low power factor at off-peak hoursn Harmonics distortion

n Improper earthing at consumer endn Long single phase linesn Low HT/LT ratio

Losses…

nCommercial lossesnTapping (hooking) on LT linesnFaulty energy meters\ unmetered supplynErrors and delay in meter reading and billingnUneven revenue collection n

………………

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Problems in loss reduction

n No energy auditn No segregation of losses into technical and

commercial lossesn Political issuesn Lack of regular patrolling for checking the theft

and tempering of meteringn No transparency in meter reading and billingn Lack of adequate investment for system

modernization

Useful solutions

n Renewable energy sourcesn Distributed local generationn Availability Based Tariffn Improved Power qualityn Demand side managementn Information Technology applicationsn Benchmarking n Employee training n Consumer Training

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Renewable Energy Sources

n India is blessed with an abundance of renewable energy sources e.g. sunlight, water and biomass.

n Wind Superpower: India has the world’s largest program for renewable energy.

n Eco-friendly power: Solar photovoltaic electricity can contribute significantly to reductions in greenhouse gas emissions from the thermal power plants.

n Local generation: No need to construct grid or network, optimal choice for remote and rural areas

Distributed Generationn The cost of laying transmission lines in rural areas can not be recovered

due to less return.

n Low tariff in agriculture and domestic sector leave few resources to expand or maintain the quality of supply.

n Distributed Generation is very useful to supply power in rural and remote places where the long distribution lines results in high losses.

n DG can help to reduce congestion on the power lines and strengthen local area transmission and distribution reliability.

n DG reduces the likelihood and impact of large-scale power outages while smoothing output fluctuations from individual power systems.

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n The following benefits of DG to the T&D system and its customers are described below:n · Risk Managementn · Distribution Facility Deferral or Avoidancen · Line Loss Reductionn · Voltage and Stability Supportn · Ancillary Services.

Availability Based Tariff (ABT)

n It controls the frequency variations by penalty/reward mechanism for any deviations from the schedule.

n It helps to reduce the gap between supply and demand by scheduling of every 15 minutes block.

n It takes care of merit order dispatch.n Maximization of generation during peak load hours and load curtailment

equal to the deficit in generation.n Backing down of generation to match the system load reduction during

off peak hours, keeping the merit order of generation in view.

n It improves grid discipline and thereby reduce transmission losses.

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Power Quality Problems

n The quality of power at distribution level is very bad in India (voltage deviations are more than 25% and frequency deviations >5%).

n Voltage stabilizers at consumer’s premises result in incremental losses and require additional capital cost.

nHarmonics has not been focused though it also increases the loss and distorts the power factor.

Harmonics

n In non-linear loads, the current is of complex waveform due to dynamic characteristics of the load. The component of the complex waveform can be described as superposition of waveforms, called harmonics, having frequencies from 0 to infinity.

n For distribution systems which must handle a large percentage of non-linear loads, the percentage of harmonic currents can be very high.

n switch-mode power supplies, PWM converters, voltage source converters, fluorescent lighting with electronic ballasting, computers are the major sources of harmonics current.

n About 58% of all power used can have harmonic currents overloading transformers, capacitors and other components on the distribution system.

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Harmonics…

n The additional current will increase losses in wire, bus bars, transformers and power factor correction capacitors used in the distribution system.

n The additional heating caused by each of the harmonic currents of high frequencies.

n Harmonic current will cause voltage distortion and low power factor.

n Due to harmonic current the use of line filters before a drive will add more losses to the electrical system and could create line ringing and large voltage transients.

Reduction of Harmonics

n Preventive solutions

n Phase cancellation or harmonic control in power convertersn Developing procedures and methods to control, reduce of

eliminate harmonics in power system equipment

n Remedial solutionsn Use of filtersn Circuit detuning which involves reconfiguration of feeders or

relocation of capacitor banks to overcome resonance.

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Demand Side Management

n Systematic utilization of energyn Maximizing efficiencyn Balancing supply and demand at consumer leveln Improve economic developmentn Involve environment friendly power and reduce energy

billsn Energy conservationn Energy audit

DSM by consumer training

nConsumer can be trained fornShifting of energy use to off-peak hoursnEnergy conservationnEfficient choice and utilization of electric

appliancesnStandards, quality and performance

evaluation of domestic electric equipments

nEnergy audit

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IT Applications

nIntegrated inventory and billing system nCustomers profilingnData miningnLoad survey data and network analysis of

HT systemsnGeographical Information System (GIS) and

Customer Relationship Management (CRM)

Benchmarking

n Benchmarking is a collaborative learning process among a group of companies to nfocus on specific operating practices,ncompare measures and resultsn identify improved processes n within their organizations

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Benefits of Benchmarking

nPromoting competitionnPerformance evaluation nCoordinated tariffnImproving power quality and productivitynMaximizing efficiency

Employee Training

n Employees training should be conducted on a regular basis to upgrade their knowledge.

n Survey of UP Discoms shows that there is a pressing need for training of employees at all level and in all fields of the electric distribution company.

n Employees also have much interest in IT applications in power sector.

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Employee Training…

n Employees can be taught for

n Overview of the electric system operations including engineeringcriticality and quality.

n Awareness of Reforms program- APDRP n Simulation toolsn Energy auditn Energy management systemn Management information system

n IT applicationsn Finance and Accounts

Government Initiatives

nAccelerated Power Development and Reform Programme (APDRP)nFull metering, energy audit and

MIS, control of theft.nIncrease in transformation capacity.nIncrease in HT/LT ratio. Systems

analysis and reconfiguration.nReduction of technical losses.

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Initiatives by Andhra Pradesh

n Technological reformsnHigh Voltage Distribution System (HVDS)n Spot billingn Customer Analysis Tool (CAT)nGeographic Information System (GIS)

n Customer caren Trouble call management (TCM)n Customer profiling

Initiatives by Delhi (BSES and NDPL)

n Installation of electronic meters at sub-transmission and distribution level.

n Replacement of faulty metersn Computing Aggregated technical and commercial (ATC)

losses n Consumer indexingn Improving billing and payment mechanismn Introducing an LT less distribution systemn Improving quality of power n Customer care centresn Training employees

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Voltage Sag

Phase current did not increase during the sag which suggests that the start up of a major downstream load did not occur and the origin of the sag is probably upstream.

Possible cause: Upstream load or utility fault clearing.

Typical solution: Line conditioner, UPS.

Equipment affected: Computers, motors, and electronic drives.

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Transients:

Transients:

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Transients:

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Short Duration Voltage Variations

Short Duration Voltage Variations

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Long Duration Voltage Variations

Long Duration Voltage Variations

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Interruptions

Waveform Distortion

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Waveform Distortion

Waveform Distortion

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Voltage Fluctuation

Frequency Variation

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Non-rectangular rms variation

February 20, 1994 at 12:52:52 LocalPhase A Vol tageRMS Var ia t ion Trigger

0 0 .25 0.5 0 .75 1 1 .25 1.5 1 .75 2

02 04 06 08 0

1 0 01 2 01 4 0

T ime (Seconds )

% Vo l ts

0 2 5 5 0 7 5 1 0 0 1 2 5 1 5 0 1 7 5 2 0 0

-150-100

- 5 00

5 01 0 01 5 0

T i m e ( m S e c o n d s )

% Vo l ts

Duration0.633 Sec

Min 0.166Ave 75.50Max 138.8Ref Cyc le

43760

Illustration of “Specified Voltage” characterization

of rms variation phase measurements

MeasurementEvent #1

0

20

40

60

80

100

120

140

0.000 0.167 0.333 0.500 0.667 0.833 1.000 1.167 1.333 1.500 1.667Time (seconds)

%V

olts

T80%

T50%

T10%

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A Model of Electricity Sector Reforms

Accountability of The Regulatory Authority

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Electricity Supply Quality:The Main Determinants

Steady state voltage Waveform in the Time Domain

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Steady state voltage Waveform in the Frequency Domain

Trend of Voltage Total Harmonic Distortion Demonstrating Daily Cycle for One Week

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Tools to Guarantee andPromote Commercial Quality

UPS Internal Topology

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UPS Internal Topology

UPS Internal Topology

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UPS Internal Topology

A Software Module for Assessment of Reliability/Availability and Maintenance Scheduling

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Software Module for Excess Capacity Computation

Power System of a Data Center

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Summary of Power Quality Variation Categories

Example current waveforms for various nonlinear loads.

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Methods for Measuring Voltages and Currents with Multi-Meters

ANALYZING POWER QUALITYMEASUREMENT DATA

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Three Dimensional RMS Variation Bar Graph

Input and Output Voltages of aTypical Motor Voltage Controller

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The New Wave of SensitiveEquipment

Perfect quality power delivered at voltage, V, and frequency of 60 cycles per second (60 Hz)

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TYPES OF POWER QUALITYDISTURBANCES

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Effect of increased loading on voltage and current waveforms

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Typical Building Power Distribution Scheme

Harmonic Producing Equipment in Office Buildings Harmonic

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Harmonic Related Problems in Buildings

Typical Current Waveforms of Appliances

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Typical Current Waveforms of Appliances. Contd.

Typical Current Waveforms of Appliances. Contd.

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Typical Current Waveforms of Appliances. Contd.

Effect of Triplen Harmonics in Neutral Conductors Effect

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Harmonic Effects on Transformers

Passive Approach for Neutral Current Reduction Passive

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Zig-Zag Transformer for Neutral Current Reduction

T-Connected Transformer for Neutral Current Reduction

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Star-Delta Transformer forNeutral Current Reduction

Zig-Zag Transformer for Neutral Current Reduction

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Active Neutral Current Filtering Scheme Active

Active Neutral Current Filtering Scheme Active

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Active Neutral Current Filtering Scheme Active

Active Neutral Current Filtering Scheme: Functional Block Diagram

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Active Neutral Current Filter

Active Neutral Current Filter:Features

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Active Neutral Current Filter:Connection

Active Neutral Current Filter:Connection

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Filter Specifications

Filter Specifications: Contd.

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Conclusions

What is power quality?

nPower quality refers to variations in voltage flowing into and through your home. Fluctuations in the electrical flow, which can vary from one or two volts to thousands, can damage electronic equipment, either instantaneously or gradually.

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What is a power surge?

nA power surge is a variation in electrical voltage caused by conditions both outside and inside your home. Surges can travel through your electric, phone and cable TV lines.nIn a typical year, the average home has

over 2,000, with more than 50 percent originating from inside the house. The majority of power surges go unnoticed.

What causes power surges?

nMost people commonly associate power surges with lightning, but surges are more often linked to other types of uncontrollable events including tornadoes, ice storms, animals on power lines, tree limbs, etc. n And over half of all power surges are created

within the home when devices with motors shut off or start up, diverting energy to and from other appliances. Common culprits of internal surges are power tools, refrigerators, printers and hair dryers.

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How do I know if I have had a power surge?

nIt is not always easy to detect if you have had a power surge. Large power surges, such as lightning, can instantly ruin your TV, computer and other electronics.nBut not all power surges instantly cause

this extent of damage. Smaller surges can slowly destroy your expensive electric appliances - this is called "electronic rust".

Isn't Alliant Energy responsible for power surges?

nAlliant Energy is responsible only for surges that occur due to failure of our equipment. Most surges are caused by factors outside of the control of telephone, cable and electric utilities. nWe are not responsible for surges caused

by lightning, animals, tree limbs, faulty wiring or surges created within your home.

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Won't a circuit breaker protect my equipment from surges?

nThe speed at which a surge travels can range from 1/100th-1/1000th of a second. Circuit breakers take approximately 17/100 of a second to respond to excess current. Electrical surges can come and go before the circuit breaker can react.

Why do I need protect my home from surges?

n The average home today has over 25 motor driven appliances and several thousand dollars worth of sensitive electronic equipment - all of them vulnerable to the damaging effects of power surges. n Exposure to surges of all sizes can shorten the

life and reduce the operating efficiency of your sensitive electronics and appliances.

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What is the best way to prevent power surge damage?

n The best way to protect valuable electronics and appliances frompower surges is to use a two-step defense system.

n The first part of this system involves use of a “whole-house” surge suppressor installed at your electrical meter or service panel to protect against external surges that travel through the incomingelectrical line. Only a qualified electrician should install a service panel-based suppressor; meter-based units may be available from your utility company.

n The second part of the system involves use of individual point-of-use surge protectors to prevent damage from surges originating within the home and those that travel through cable and telephone lines.

What are the characteristics of a good quality point-of-use surge protector?

Good point-of-use surge suppressors should have the following characteristics:

n UL-1449 rating to ensure adequate testing by Underwriters Laboratories. Look for a specific UL rating, not just a label that says "UL Listed".

n A clamping voltage of 330. This is the level at which the surge protector begins to block the surge - the lower the clamping voltage, the better.

n A joule rating of at least 400 is good; 600 is better. This a measure of the surge protector's ability to absorb surges.

n A response time of 10 nanoseconds or less. n Protection between all three wire combinations: L-G (line-to-ground), N-G

(neutral-to-ground) and L-N (line-to-neutral). n A warranty against defects in workmanship and parts. n Connected equipment coverage that will guarantee to replace any

connected equipment that becomes damaged in the unlikely event t hat a suppressor does not resist the surge. Dollar amounts of this guarantee will vary, so choose the one the equals or exceeds the price of the connected equipment you want to protect.

n Enough connections to protect all components of a system, including telephone, cable and satellite.

n An on/off switch allowing you to shut off power to every connected component.

n An indicator light or audible alarm so you know a high-level surge has occurred.

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What's the difference between a power strip and a surge protector?

n A power strip and surge bar can look very similar, but they perform very different functions.

n The main purpose of a power strip is to provide multiple outlets for you to plug-in anything that requires electricity. They are generally priced under $10.

n A surge protector can provide multiple outlets, but their main purpose is to provide protection from power surges; some have phone and cable jacks.

n Point-of-use surge protectors are generally priced between $20-$170, depending on the level of surge suppression the unit can provide and the time it takes for the unit to react to a surge, as well as other factors.

What's a ground and why do we need to check it?

n A ground is a way to provide excess current an alternative path around the electrical system of your home or workplace by intentionally connecting the system to the earth.

n The electrical grounding system serves the purpose of protecting personnel health and safety, as well as, protecting equipment and buildings from physical loss. The National Electric Code requires your home's electric system be connected to the earth.

n Surge suppressors route excess current through the ground wire preventing damage to connected equipment. No surge suppressor, no matter how expensive, will work if there is a problem with your home's grounding system.

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How can I tell if my home is properly grounded?

nIf your home contains two-prong outlets, the electrical system is not grounded. Three-prong outlets should be properly grounded, but that is not always a guarantee that they are performing properly. nIf you suspect a grounding problem, the

best solution is to contact a licensed electrician for an evaluation.

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