Concepts and Principles (2)

7/31/2019 Concepts and Principles (2)

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Concepts and Principles of Distribution LossReduction

T Raghunatha

Joint Director

Central Power Research Institute

Bangalore

Best practices in Distribution loss reduction


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Installed

Capacity=182689 MW

T&D Losses:25.47 A &TC Losses: 28.44%

Peak Shortage: 12.7%Per Capita Consumption : 733.54units

IndianPower SceneIndian Power Scenario


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Frequency fluctuations 2 HzVoltage fluctuations 10% - 40%

Statistical non-availability About 200-800 hours per

year

Technical transmission

and distribution losses

Estimated 30% from 220

kV to 220V

Commercial losses >20%

From a technical point of view the story was not different as

reflected in the Grid performance.

IndianPower SceneIndian Power Scenario


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PERCENTAGE TRANSFORMATION, T&D

TECHNICAL LOSSES IN DEVELOPING COUNTRIES

0

5

10

15

20

25

30

35

40

45

R

EP.OFKOREA

CHINA

BARBADOS

BELIZE

THAILAND

TUNISIA

EL-SALVADOR

FR

ENCHGUIANA

BRAZIL

ZIMBABWE

GUATEMALA

PHILIPINES

SRILANKA

INDIA@

PAKISTAN

NICARAGUA

HONDURAS

MYANMAR

%

... Where does India stand globally


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Loss Scenario in India

Sl No SystemSegment

Existing% Level

Target%Level

Tolerable% Level

1 Trs. System 4.5 2.00 3

2 Sub Trs.System

4.0 2.25 3

3 Primary (HV)

Distn

7.0 3.00 5

4 Secon (LV)

Distn

7.5 1.00 4

5 Total 23% 8.25 15


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ACS v/s ARRIndian

Power Scene

ACS ARR

2001-02 246 181

2002-03 238 195

2003-04 239 203

2004-05 254 209

2005-06 258 221

2006-07 276 227


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All India T&D and AT&C Losses

T&D Losses

AT&C

Losses

2002-03 32.54 32.54

2003-04 32.53 34.78

2004-05 31.25 34.33

2005-06 30.42 33.02

2006-07 28.65 30.59

2007-08 27.2 29.24

2008-09 25.47 28.44


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T&D and Revenue Loss

The total of Technical and Commercial losses are

called Distribution losses

In addition to the above, revenue loss occurs on

account of non realization of billed demand


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Technical Losses

Every element in a power systema linea transformer etc

consume some energy while performing their expected duty.

Cumulative energy consumed by all these elements

constitute technical losses.


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AT&C Losses

Example:

Units Input 100 MU Units sold 70 MU

Losses 30 MU

T&D Loss 30%

If Revenue collections are

90% of demand.

Out of 70 MU of sales revenue

is realized for 63 MU.

AT & C losses are 37%.

AT & C is abbreviation for Aggregate Technical& Commercial Loss


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LOSSES DEPENDS IN ANY SYSTEM ON

Pattern of Energy Used

Intensity of Load Demand

Load Density

Capability and configurations of T & D system


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State-wise T&D Loss (%)


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AT & C Loss

Loss in Revenue due to Non Realization of Billed Demand

Input EnergyEnergy Realized x 100Input Energy

or

1Billing Efficiency x Collection Efficiency

Energy Realized = Units Billed x Collection Efficiency

Technical Loss + Commercial Loss + Revenue Loss due to Non

Realization of total Billed Demand

Ex: Units Input = 100MU Units Input = 100MU

Units (Output) Sold = 70 MU Units Realized = 63 MU,

(90% of 70 MU)T & D Loss = 30 MU AT & C Loss = 37 MU


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Causes for Technical Losses

Wrong location of DTCs

DTCs are not located centrally and farthest consumersface low voltages

For every 10% voltage drop losses increase by 21% andfor every 20% voltage drop losses increase by 44%

DTCs to be relocated at load center to minimise losses


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Over rated DTCs

Under loaded DTCs are a source for high avoidable

Iron losses

Taking village as a unit the loads can be readjusted

among all DTCs in the village for optimal use of

installed capacity


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Low voltage pockets

Where as the permissible LT voltage variations are +/-

6% the voltages at some points go below 10% and in some

cases even more

Full load current drawn by motors go up by 15% for

every 10% drop in voltage

On load tap changers are not made use of due to certaininhibitions


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Low power factor In majority of Distribution circuits the pf is between 0.65

& 0.75

Low pf contributes to high distribution losses

When shunt capacitors of adequate rating are fixed atload end, experiments showed

10% Improvement in voltage

20% reduction in current

6% overall reduction in energy


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Bad workmanship

Bad joints are a source of power loss

Proper jointing techniques should be adopted for firm

connection

Connections at line jumpers, transformer bushingrods, drop-out fuses, isolators, LT switch etc shall beperiodically inspected.

Timely replacement of deteriorated wires, worn outclamps etc


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Inadequate conductor size.

Main consideration for selection of conductor is voltagedrop

Approved voltage regulation in distribution lines is +/-8% for 11kV and +/-6 % for LT .

Current carrying capacity at ambient temperatures is also

a consideration. Voltage regulation is

(ES-ER)/ ER

ES - Sending end voltage

ER - Receiving end voltage


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Standards for 11kV Lines

Length of 11kV line corresponding to different loads

Size of

conductor

kVA-km for

8% voltage

drop at 0.8pf

Max of

length of

line (km)

Load that

can be

connected

(kW)

Rabbit 10,650 30 355

Weasel 7,200 20 360

Squirrel 5,120 15 341

The figures are for a conductor temperature of 600C. For a conductor

Temperature of 500C, the above figures shall be about 3% higher and for a

temperature of 700

C about 3% lower.


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Standards for LT Lines

Length of 415V line corresponding to different loads

Size of

conductor

kVA-km for 6%

voltage drop at

0.8pf

Max of length

of line (km)

Load that

can be

connected

(kW)

Rabbit 11.76 1.6 7.35

Weasel 7.86 1.0 4.86

The figures are for a conductor temperature of 600C. For a conductor

Temperature of 500C, the above figures shall be about 3% higher and for a

temperature of 700C about 3% lower.


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Way to reduce Technical Losses

By proper planning of system configuration by using

Computer Analysis, LT Lines (Radialy laid) can be

reduced & HT can be increased

Running Express Lines for bifurcation & load sharing

Adding Additional DTCs to Network based on load

growth & locating them near load centers

Judicious selection of DT matching with Maximum

KVA Demand @ good pf


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Use of On load Tap Changers in Power Transformer atHigh Voltage 66/11Kv substation

To compensate for the voltage drop at transformer

terminal resulting in poor regulation

Providing switched capacitors & Automatic

voltage regulators on 11 Kv feeders

Use of Off load Tap Changers in DTCs to

compensate Voltage drop due to Agriculturalpump sets, which may draw more current and

hence double line losses



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i) 11 kV Lines

PF KVA Current Line Losses

Kw

Before 0.7 428 38.9 27.2

After 1.0 300 27.2 13.4

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Improving PF by Series and Shunt Capacitors installed at33/11 kV Secondary Side of Power Transformer

ii) LT Lines

Optimum Rating of Capacitor Bank = 2/3rd of KVAR requirement of that

distribution Network

Optimum Location: 2/3rd Length of Main Distributor from transformer

end



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1) Use of Best Possible Workmanship

2) Use of Minimum joints and proper techniques like PG

Clamps and Wedge Clamps

3) Avoiding Loose connections to Transformer bushing

stem, Dropout Fuse, Isolator, LT Fuse Kit to preventsparking and heating of contacts

4) Periodical inspection of all joints/connections

5) Replacement of deteriorated wires/services/Materials

timely to avoid any cause of Leaking and Loss of Power

6) Adhering to O & m Schedule for all equipments /

Switchgears

7) Outsourcing and franchising of feeders/Substations



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System Planning to reduce Technical losses

Develop SLD for all 11kV Feeders

Collect feeder loadings Calculate the Technical losses for all feeders

Categorize the feeders on their loading and loss levels

Suggest the improvement required for each feeder

Prioritize the feeders based on the benefit to cost ratio To start with pick high loss/heavily loaded feeders and

execute improvement work on them

Have an improvement investment plan for at least 3 to 5

years up front and cover all feeders.


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Comparison of 11kV & LT line Losses

Contrary to popular belief, HT line losses in rural 11kVfeeders are often higher than LT line losses.

Currents stepped up by a factor of 25 in a 11000/433Vtransformer, does not necessarily imply larger LT losses.

Losses depends on how many DTCs exist and how many

LT feeders are taken out directly from the secondary ofthe transformer.

Let us assume there are n number of DTCs ,

An average two feeders directly come out of thesecondary of the Transformers.

Let I be the 11kV line current.For simplicity

assume that the loads are the same and branch out equally,then the branch currents on the LTs are 25I/2n


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The primary and secondary conductors are of the samecross-section and the LT to HT ratio 4:1,

HT and LT line losses are equal, when

[I x 25/2n]2 x 4R = I2R,

Then, n=25

This indicates that the LT and 11kV line losses will beapproximately same when the number of TCs is 25

With 2 LT Circuits on DTC Secondary, for n>25, LTlosses would be less than HT losses.


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If the secondary current flows only in one LT feeder fromeach DTC, the equation will be modified into[I x 25/n]2 x 4R = I2R, where n=50

And for n>50, the LT losses would be less than HT losses.

In Rural 11kV feeders,Inmost cases two or more LT feeders branch out of thesecondary of the transformer.

Rural feeders often have more than 50 TCs,

Hence in majority of rural feeders LT line losses arelikely to be less than HT losses.

In Urban feeders, however, the number of TCs aresignificantly less and the reverse would be true.



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Commercial Losses.

Occur on Account of

Non performing meters

Under performing meters

Meters not read

Application of lower multiplication factors

Defects in CT/PT circuitry

Pilferage by manipulation

Theft by direct tapping etc.

W t R d C i l L


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Way to Reduce Commercial Losses.

DTC wise energy audit

Use quality meters

Strengthen Vigilance squad

Proper consumer indexing

Computerized billing


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1) Accurate Metering

2) Use of appropriate range of meter w.r.t connected load

3) ETV meters with TOD, tamper proof data and Remote

reading facility for HT and High valued services

4) Energy Meters housed on a separate Box sealed and

inaccessible to consumer

5) Multicore PVC Cable used for Service Mains

6) Providing potentials link inside body of Energy Meterrather than inside thermal cover


d l


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1) Integrated of MBC software along with CAT & MAT

softwares to improve collection efficiency and easy

implementation of A. T. Law

2) Eradication of theft by implementation of ATL and

constant intensive inspection by vigilance squad

3) Implementation of IT measures as BEST PRACTICES

adopted by DISCOMs

4) Outsourcing & Franchising of Meter, Billing and

collection and Energy Auditing and Accounting



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Anti Power Theft Initiatives

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Vigilance Activity has been intensified to reducecommercial losses

11 Police Stations are functioning

Special Courts at District Headquarters have been set upexclusively for speedy disposal of Electricity related cases

Apart from Vigilance Inspections by O & M staff havebeen intensified

Periodical and surprise inspections are being carried out

Meter Testing Division and Vigilance wing


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MILESTONES ACHIEVED

57

ESCOMs has achieved the following milestones during the last two yearsMilestones:

Any Time Payment Kiosk

Transformer Information Management System

Business Plan (07 -10)

Training to ESCOM Personal

Real Time Remote Automatic Meter Reading (RRAMR) Rural Load Management System

DTC wise Energy Audit

Modernization of Central Complaint system

Energy Saving Initiatives ( Demand Side Management)

Insurance Cover

Customer Interaction Meets

Grama Vidyuth Pratinidhi

Prepaid Metering on Experimental basis


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Conclusions

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Reduction in AT & C loss calls for

DTC wise Energy Audit

System Improvement works

LT Reconductoring works Rural Load management System

Introducing HVDS System of distributions

APDRP Works

Rating and Calibration of installations on a regular basis

Reducing the overloaded conditions of existing DTCs byestablishing new DTCs at Load centers

C l i


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Bringing in fresh investments both long term capitaland working capital

Reduction of political interference in day to dayworking

Bringing effective regulatory Mechanisms

Bringing Competition both at generation anddistribution levels

Strict enactment of Antitheft Law in accordance withElectricity act 2003

IT initiatives in Power Sector

Professional Management and change in work culturein Power Sector

Conclusions


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THANK YOU

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Concepts and Principles (2)