Technology for Generation, Transmission and Distribution -Status and Performance Indicators

7/28/2019 Technology for Generation, Transmission and Distribution -Status and Performance Indicators

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Prof S. N. Singh

Department of Electrical Engineering ,

IIT Kanpur

Department of Industrial and Management Engineering

Indian Institute of Technology Kanpur

3rd Capacity Building Programme for

Officers of Electricity Regulatory Commissions23 – 28 August, 2010

Technology for Generation,Technology for Generation,

Transmission and DistributionTransmission and Distribution --Status and Performance IndicatorsStatus and Performance Indicators

Forum of Regulators



Evolution of Power Systems

Late 1870s Commercial use of electricit

1882 First Electric power system ( Gen., cable, fuse,

load) by Thomas Edison at Pearl Street Station in

.

- DC system, 59 customers, 1.5 km in radius

- 110 V load, underground cable, incandescent

amps

1884

1886

Motors were developed by Frank Sprague

Limitation of DC become apparent

- High losses and voltage drop.

- Transformation of voltage required.

1889

developed by William Stanley of Westinghouse

First ac transmission system in USA between

, .

- 1- phase, 4000 V, over 21 km



Evolution of Power Systems (Contd.)

1888 N. Tesla developed poly-phase systems andhad patents of gen., motors, transformers, trans.

.

Westinghouse bought it.

s on roversy on w e er n us ry s oustandardize AC or DC. Edison advocated DC

and Westinghouse AC.

- Voltage increase, simpler & cheaper gen. andmotors

1893 First 3-phase line, 2300 V, 12 km in California.

ac was chosen at Niagara Falls ( 30 km)



1922

Early Voltage (Highest)

165 kV1923

1935

220 kV

287 kV

19531965

330 kV500 kV

1969

765 kV

Standards are 115, 138, 161, 230 kV – HV

345 400 500 kV - EHV

765, 1100 kV - UHV

Earlier Frequencies were

25, 50, 60, 125 and 133 Hz; USA - 60 Hz and

some has 50 Hz, Which Frequency is better?



1950s

ransm ss on ystem

Mercury arc valve

Got land island by cableLimitations of HVAC Transmission

1. Reactive Power Loss

2. Stability3. Current Carrying Capacity

4. Ferranti Effect

. o smoo con ro o power ow



Advantages of HVDC Transmission

Ground can be used as return conductor

Less corona loss & No reactive power loss

C eaper or ong stance transmss on

No skin & Ferranti effect

Asynchronous operation possible

No switching transient

No transmission of short circuit power control possible

Disadvantages of HVDC Transmission

os o ermna equpmen g¾Introduction of harmonics

¾Blocking of reactive power

¾Point-to-point transmission is possible



Key Drivers to Technological

Chan es in Power Sector • Development of New Materials - Polymeric,

Composite, Nano, Superconducting materials.

• Supply-demand gap and Environmental Concernsin Generation Sector

• Development of New Devices and Technologies

- Power Electronic Devices, DSP, Sensors, Information &

Communication Technology

• Maintaining Stable & Secure Operation of Large

Interconnected Transmission System• Increased losses and Poor Quality of Supply and

evenue o ec on n s r u on ec or

• Regulatory Changes in the Electricity Sector



• Hi h Volta e Overhead Transmission

– Voltage up to 1200 kV ac, ±800 kV DC– High EM radiation and noise

– High corona loss

– More ROW clearance• Gas Insulated Cables/Transmission lines

• HVDC-Light



Gas insulated Transmission Lines

– For the transmission of high power over long distances GITLsare a good technical solution as an alternative to O/H lines andinaddition to cables.

– If the diameter of outer shield is more compared to core, it iscalled gas insulated transmission lines. Normally tunnels areused in GITL.

– GITLs are used since more than 35 years for linking power

plants to transmission network. First was commissioned in1975 in German of about 700m.

– First mixed GITL in the world successfully completed its fieldtrials with an endurance test in 1999.

– , , .transport power of 300 MVA.

– The cost of GITL is 8-10 times those on overhead power lines.



Gas insulated Transmission Lines

those used in laying pipelines.

• Simplification and standardization of individual.

• Use of SF6 (20%) and N2 (80%)gases mixture.

• Basic Design

– Enclosing tube is made of aluminum alloy and designed tobe a pressure vessel as well as carrying mechanical load

of conductors.

– Enclosing tube is also used for carrying the inductivereturn current which is same as rated current.

– The inner conductor is an aluminum tube held in place by

bushings spaced at 100 m.– Sliding-contact plugs and sockets accommodate the

thermal expansion of the conductor.

– GITLs are installed in segments.





• Benefits of GITL

– ow res s ve osses re uce y ac or

– Low capacitive losses and less charging current

–

– No correction of phase angle is necessary even

for long distance transmission– No cooling needed

– No danger of fire

– Short repair time– No aging

– .



HVDC-Light

• Classical HVDC technology

– Mostly used for long distance point-to-pointtransmission

– Requires fast communication channels between two

– Large reactive power support at both stations

– Th risto valves are used.

– Line or phase commutated converters are used.

• HVDC-Light

– Power transmission through HVDC utilizing voltagesource converters with insulated gate bipolar

more faster and with less energy loss than GTOs.



HVDC-Light

– It is economical even in low power range.

– Real and reactive power is controlled independentlyin two HVDC light converters.

– Controls AC voltage rapidly.

– .

– No contribution to short circuit current.

–converter stations.

– Operates in all four quadrants.

– PWM scheme is used.

– Opportunity to transmit any amount of current of .



HVDC-Light

– Low complexity-thanks to fewer components

–

– Useful in windmills

–

• First HVDC-Light pilot transmission for 3 MW, ±10kV

in March, 1997 (Sweden)• First commercial project 50 MW, 70 kV, 72 km, in

1999.



• Transmission system limitations:

– System Stability

•Transient stability

•Dynamic Stability

•

•Frequency collapse

•Sub-synchronous resonance

– Loop flows

– Voltage limits

– Thermal limits of lines– High short-circuit limits

FLEXIBLE AC TRANSMISSION SYSTEM (FACTS)



• Develo ments in Generation side– Powerformer Energy System

–

•Wind Power (upto 6 MW)•Fuel Cells

•Biomass etc.

– Combined Cycle Power Plants



Powerformer Energy System



TM

• Hi her erformance availabilit overload

• Environmental improvement• Lower wei ht

• Less total space requirement

• Lower cost for Civil Works• Less maintenance

• Reduced losses

• Lower investment• Lower LCC



Electrical Field Distribution

E-field

non-uniform

Bar Cable

3kV/mm

E-field

uniform

6-9kV/mm

/ m m )

E ( k



Conductor (1), Inner semi-conducting layer (2),-



Distributed Generation/Dispersed Generation

DG includes the application of small generations in, ,

throughout a power system

generators whether located on the utility system at

the site of a utility customer , or at an isolatedsite not connected to the power grid.

By contrast, dispersed generation (capacity

ranges from10 to 250 kW), a subset of distributedgeneration, refers to generation that is located at

.



DG includes traditional -- diesel, combustion

turbine combined c cle turbine low-head h droor other rotating machinery and renewable -- wind,

solar, or low-head hydro generation.

The plant efficiency o most existing large central

generation units is in the range of 28 to 35%.

to small fuel cells and to various hi-tech gas turbineand combined cycle units suitable for DG

.

Part of this comparison is unfair . Modern DG utilizeprefect hi-tech materials and incorporating advanced

and include extensive computerized control thatreduces operating labor.

DG “ Wins” Not Because It is Efficient, But Because It Avoids T&D Costs



pera ona anges



• Power System Restructuring

– But not only Privatization

• Deregulation is also known as

– Competitive power market

– Re-regulated market– pen ower ar e– Vertically unbundled power system–



Horizontal se aration

GenerationBusiness

or Vertical cut

Transmission

Business

Verticalseparation

Horizontal separation

DistributionBusiness



• Why Restructuring of Electric Supply

n us r es– Better experience of other restructured market

, , ,

airlines, etc.– Com etition amon ener su liers and

wide choice for electric customers.

• Why was the electric utility industryregulated?

– Regulation originally reduced risk, as it was

perce ve y ot us ness an government.– Several important benefits:

• .



• It gave util ities recognition and limited support

.easements.

• It assured a return on the investment, regulated as

that might be.

• It established a local monopoly in building the

.

• Simplified buying process for consumers.

• Electricity of new and confusing to deal with theconfl icting claims, standards and offerings of

different power companies.

.• Meeting social obligations

•



• Forces behind the Restructuring are

– g ar s an over s a ng– Global economic crisis

–

– Political and ideological changes–

– Lack of public resources for the future

develo ment– Technological advancement

– Rise of environmentalism

– Pressure of Financial institutions– Rise in public awareness

– Some more …….



• Reasons why deregulation is appealing

No longer necessary The primary reason for regulation,to foster the development of ESI

.

Electricity Price may drop Expected to drop due to innovationand competition.

usomer ocus w mprov xpece o resu n w ercustomer choice and more attention

to improve serviceEncourage innovatio Rewards to risk takers an

encourage new technology andbusiness approaches,

Augments privatization In the countries where Govt. wishesto sell state -owned utilities,dere ulation ma rovide otentialbuyers and new producers.



• What will be the transformation ?

– Vertically integrated => vertically unbundled

– Regulated cost-based ==> Unregulated price-based

– Monopoly ==> Competition

– service ==> commodity– consumer ==> customer

– privilege ==> choice

– EngineersÎ Lawyer/Manager



• A number of questions to be answered

– Is a Restructuring good for our society?

– What are the key issues in moving towards therestructurng

– What are the implications for current industrypar c pan s

– What type of new participants will be seen and

– What should be structure of market and

– What might an electricity transaction of future



• Electricity Market is very risky

– Electricity is not storable in bulk quantity

– End user demand is typically constant

– Trading is directly related to the reliability o the grid

– Demand and supply should be exact

–volatile market participants.

– Cost of continuity is more than cost of electric.



Electric Power

Electricity must be

conom ca

Secure

Stable

Reliable Good quality

" problem manifested in voltage, current,and/or fre uenc deviations that results in the failure and/or mal-operation of end

user’s equipment.



Quality of Supply?

• Supply Reliability: relates to the availability of

.

• Voltage Quality: relates to the purity of the

the absolute voltage level and frequency.

QoS= “Uninterru ted su l of ower withsinusoidal voltage and current waveform atacceptable frequency and voltage magnitude.”

Quality of Service = Quality of Supply +



Voltage or Power Quality

• Due to Disturbances e.g. transients (switching/, . ,

swell, oscillatory and impulsive waveform,

• Due to Steady State Variations e.g. nonlinear

characteristics of loads furnace/inductionheating loads, switching of converters etc.(resulting in harmonics, notching and noise).



ÂPossible effects of oor ower ualit are:

ªMaloperation (of control devices, mains signalingsystems and protective relays)

ªMore loss (in electrical system)

ªFast a in of e ui ments.ªLoss of production

Radio TV and tele hone interference

ªFailure of equipments



PQ Disturbances and their causes

PQ Disturbances Main causes of oor PQÂ Transients

Â Short Duration Voltage Variations

ªNonlinear loads

ª Adjustable-speed drives

Â Long Duration Voltage Variations

Â Interruptions

ª Traction drives

ª Start of large motor loads

Â Voltage Fluctuation (flicker)

Arc urnaces

ªIntermittent loads transients

Â Harmonics

ªSwitching, transients

Faults



Some typical PQ disturbances

Voltage sags

Major causes: faults, starting of lar eloads and

Capacitor switching transients

Major causes: a power factorcorrection method

Harmonics

Major causes: powerelectronic e ui ment arcin

Major consequences: shorts,

Major consequences: insulation

breakdown or sparkover,semiconductor device damage,shorts accelerateda in lossof

transformer saturation

Major consequences:e ui ment overheatin hi h

Voltage Sag Capacitor Switching Harmonics

accelerated aging, loss of data orstability, process interrupt, etc.

data or stability voltage/current, protective

device operations

Major causes: lightning strikes

(One of the most difficult power systemprotection problems)

Major consequences: insulationbreakdown or sparkover,semiconductor device damage,

Major causes: fallen conductors, trees (failto establish a permanent return path)

Lightning Strike High Impedance Fault (RMS)s or s, acceerae agng, oss o aaor stability

,personal safety



Service reliability indicators

Reliability of supply can be defined as the ability

of the power system to deliver electrical power tof the power system to deliver electrical power to

a given consumer over a specified period of time.

For a given customer, the reliability of supply can

usually be assessed by two parameters:sua y be assessed by o pa a e e s – The number of Interruption during a year

– The average duration of an interruption



Indicators based on system performance

SAIDI S t A I t ti D ti I d• SAIDI: System Average Interruption Duration Index(Minutes/ customer . year)

Customersof no. Total

• SAIFI: System Average Interruption Frequency Index

(Interruptions/ customer. year)

Customersof no. Total

onsinterruptiof no.annual Total

• ASAI: Average Service Availability Index (% or pu)

onsinterru tiCustomersallof Duartion)8760CustomersNo.of ( −×

8760Customersof no. Total ×



• ASAI: Average Service Unavailability Index =1-ASAI

• AENS: Average Energy Not Supplied

( cus omer.year

Customersof Number

SuppliedNotEnergy=

• Indicators related to individual customer

• CAIDI: Customer Average Interruption Duration IndexNumber (Minutes/ year)

onsInterruptiof no. Total

onsnerrupusomersaouar on=

• CAIFI: Customer Average Interruption Frequency IndexNumber

onsinterru tiof no.annual Total

affectedCustomersof No.=



• CTAIDI: Customer Total Average Interruption DurationIndex (Minutes/ year)

affectedCustomersof no. Total

onsinterruptiCustomersallof Duartion∑=

• MICIF: Maximum Individual Customer InterruptionFrequency (occurrences /year)

.during the period

• MICID: Maximum Individual Customer InterruptionICID: Maximum Individual Customer InterruptionDuration (occurrences /year)

= max. total interruptions time experienced by any

• MAIFI : Momentary Average Interruption Frequency Index

relates to momentar interru tions of < 3 . 5 min duration



Reliability index monitoring in India

Reliability monitoring is based on the following parameters:

• No. of outages of 11 kV feeders.

• Duration of outages of 11 kV feeders.

Feeder Reliability

− B

B = Outage duration in minutes

Future Technologies - Intelligent Grid



Future Technologies Intelligent Grid

ee or n us on o n e gence n e r or :

¾ Knowing the state of the Grid

¾ Take corrective actions accordingly so as to protect the grid Features of Intelligent Grid

¾ adoptive islanding,

¾ self-healing

¾ demand/generation management etc.

To Accomplish, need for Wide Area Monitoring System (WAMS).

-

synchronized phasor measurement units (PMUs) along with asystem monitoring centre and take corrective action through

a vance so ware an con ro sys em



Intelligent Grid - WAMS

Leader not a follower



Present Power System Future Power System

- Heavily relying on fossil fuels

- Generation follows load

- ore use o , c ean

coal, nuclear power

- Load follows generation

- Limited ICT use-

use



Thankhank

Y ?ou .. ?

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