CEB Distribution

7/29/2019 CEB Distribution

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Power DistributionPower Distribution

Electrical power is a little bit like the air youElectrical power is a little bit like the air youbreathe: You don't really think about it until itbreathe: You don't really think about it until itis missing.is missing.

Power is just "there," meeting your every need,Power is just "there," meeting your every need,

.. It is only during a power failure, you realizeIt is only during a power failure, you realize

how important power is in your daily life.how important power is in your daily life.Without it, life can get somewhat cumbersome.Without it, life can get somewhat cumbersome.

Power travels from the power plant to yourPower travels from the power plant to yourhouse through an amazing system called thehouse through an amazing system called thepower distribution gridpower distribution grid..


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V1 = 283Sin(x)

V2 = 283Sin(x-120)

V3= 283 Sin(x-240)

One voltage cycle of a threeOne voltage cycle of a three--phase system, labeled 0phase system, labeled 0to 360to 360 along the time axis. The plotted linealong the time axis. The plotted line

represents the variation of instantaneous voltage (orrepresents the variation of instantaneous voltage (orcurrent) with respect to time. This cycle will repeatcurrent) with respect to time. This cycle will repeat50 times per second.50 times per second.


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Voltage NomenclatureVoltage Nomenclature

Instantaneous VoltageInstantaneous VoltageIs the voltage measured at a given instant of the waveform.Is the voltage measured at a given instant of the waveform.

Peak VoltagePeak Voltages t e pea va ue o t e wave orm.s t e pea va ue o t e wave orm.

For 230V domestic system peak voltage is 283VFor 230V domestic system peak voltage is 283V

RMS (Root Mean Square) VoltageRMS (Root Mean Square) Voltage

VVrmsrms == VVpp / 1.414/ 1.414

Normally voltage (or current ) designated as 400V,Normally voltage (or current ) designated as 400V,11kV,33kV etc are11kV,33kV etc are rmsrms values.values.


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Phase Voltages and Line VoltagesPhase Voltages and Line Voltages

In a three phase system, the voltage is referredIn a three phase system, the voltage is referredbetween two phases and is some times calledbetween two phases and is some times calledthe line voltage (Vthe line voltage (VLL))

In a three phase system phase voltage is theIn a three phase system phase voltage is thevoltage between any of the phase conductorsvoltage between any of the phase conductorsand the neutral (or the ground) (and the neutral (or the ground) (VV

pp))

Mathematically VMathematically VLL= 1.732*= 1.732* VVpp


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Power Transmission and DistributionPower Transmission and Distribution Electric power transmissionElectric power transmission is one process in theis one process in the

delivery of electricity to consumers.delivery of electricity to consumers. It refers to the 'bulk' transfer of electrical power fromIt refers to the 'bulk' transfer of electrical power from

place to place.place to place.

Typically power transmission is between the powerTypically power transmission is between the power

lant and a substation in the vicinit of a o ulatedlant and a substation in the vicinit of a o ulated

area.area.

This is distinct from electricity distribution which isThis is distinct from electricity distribution which isconcerned with the delivery from the substation to theconcerned with the delivery from the substation to theconsumers.consumers.

Due to the large amount of power involved,Due to the large amount of power involved,transmission normally takes place at high voltage (132transmission normally takes place at high voltage (132kV or above).kV or above).


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Power DistributionPower Distribution

Electricity distributionElectricity distribution is the ultimateis the ultimateprocess in the delivery of electric power .process in the delivery of electric power .i.e.i.e.the part between transmission and userthe part between transmission and userpurchase from an electricity retailer.purchase from an electricity retailer.

It is generally considered to include mediumIt is generally considered to include medium--voltage (less than 50kV) power lines, lowvoltage (less than 50kV) power lines, low--

voltage electrical substations and polevoltage electrical substations and pole--mounted transformers, lowmounted transformers, low--voltage (less thanvoltage (less than1000V) distribution wiring and sometimes1000V) distribution wiring and sometimeselectricity meters.electricity meters.


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Distribution and TransmissionDistribution and Transmission

Voltages in Sri LankaVoltages in Sri Lanka TransmissionTransmission

132kV,220kV132kV,220kV

DistributionDistribution 33kV, 11kV, 400V33kV, 11kV, 400V

In a three phase system, the voltage is referred betweenIn a three phase system, the voltage is referred betweentwo phases and is some times called the line voltage (Vtwo phases and is some times called the line voltage (VLL))

In a three phase system phase voltage is the voltageIn a three phase system phase voltage is the voltagebetween any of the phase conductors and the neutral (orbetween any of the phase conductors and the neutral (orthe ground) (the ground) (VVpp))

Mathematically VMathematically VLL= 1.732*= 1.732* VVpp))


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It is necessary to transmit the electricity at high voltage toIt is necessary to transmit the electricity at high voltage toreduce the percentage of energy lost.reduce the percentage of energy lost.

For a given amount of power transmitted, a higher voltageFor a given amount of power transmitted, a higher voltagereduces the current and thus the resistive losses in thereduces the current and thus the resistive losses in theconductor.conductor.

Lon distance transmission is t icall done with overhead linesLon distance transmission is t icall done with overhead lines

Losses in Transmission and DistributionLosses in Transmission and Distribution

at voltages above 132kV.at voltages above 132kV. However, at extremely high voltages, more than 2000kVHowever, at extremely high voltages, more than 2000kV

between conductor and ground, corona discharge losses are sobetween conductor and ground, corona discharge losses are solarge as to offset the advantage of lower heating loss in the linelarge as to offset the advantage of lower heating loss in the lineconductors.conductors.

Transmission and distribution losses in Sri Lanka are estimatedTransmission and distribution losses in Sri Lanka are estimatedaround 18% while in the USA were estimated at 7.2% in , andaround 18% while in the USA were estimated at 7.2% in , andin the UK at 7.4%.in the UK at 7.4%.


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Transmission and Distribution EfficiencyTransmission and Distribution Efficiency

Transmission and distribution losses in Sri Lanka areTransmission and distribution losses in Sri Lanka areestimated around 18% while in the USA wereestimated around 18% while in the USA wereestimated at 7.2% in , and in the UK at 7.4%.estimated at 7.2% in , and in the UK at 7.4%.

Thus the efficiency of the National Grid in Sri Lanka isThus the efficiency of the National Grid in Sri Lanka is

.. The amount of energy lost is about 700 million kWhThe amount of energy lost is about 700 million kWh

The value of lost electricity is around 7000 million Rs.The value of lost electricity is around 7000 million Rs.

If the losses are reduced to 10% the saving would beIf the losses are reduced to 10% the saving would be

3000 million Rs per annum.3000 million Rs per annum.


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How the Losses HappenHow the Losses Happen

The losses includeThe losses include

Heat losses in the conductors.Heat losses in the conductors.

Losses due to Corona effect (Losses due to Corona effect (Corona is aCorona is aphenomenon that has the capability for degrading insulators,phenomenon that has the capability for degrading insulators,

and causing systems to faiand causing systems to fail.l...

PilferagePilferage


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How to Improve EfficiencyHow to Improve Efficiency

ByBy reconductoringreconductoring over loaded lines.over loaded lines.

By employing higher voltages for transmission.By employing higher voltages for transmission.

By employing optimum capacity transformers.By employing optimum capacity transformers.

By stopping electricity pilferage andBy stopping electricity pilferage and

unmetered sales.unmetered sales.

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