reliability of distributed system

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TECHNICAL SEMINAR PRESENTATION-2011

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Yogesh Ranjan Mishra

Presentation

On

Reliability of Distribution system

Under the guidance of

Mr. Ch Murthy

By

Yogesh Ranjan Mishra Roll # EIE200720073



INTRODUCTION


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• Electric system reliability is a measure of the system’s ability to

meet the electricity needs of customers.

• The reliability of the electric system depends on the reliability of thatsystem’s component parts, including, for example, power plants,

transmission lines, substations, and distribution feeder lines.

• My objective is to present what is reliability in distribution systems.



DISTRBUTION SYSTEMS


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•That part of power system which distributes electric power for local

use is known as “distribution system”.

•It mainly consists of three parts.

- feeders

- distributor

- service mains

•Requirements of a good distribution system :

- Proper voltage- Availability of power on demand

- Reliability




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RELIABILITY

• Definition: -

“Reliability is the ability of the power delivery system to provide

uninterrupted service to the customers”.

• This definition is true for electric power systems, generally, andelectric power distribution systems, in particular.

• Reliability concerns are often split into three categories:

- Adequacy

- Security

- Quality



HOW TO MEASURE RELIABILITY ?


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•Reliability measures dealing with interruptions, address three

factors: frequency, duration, and extent or severity.”

•The extent is the number of customers or load affected, which isdetermined by the layout of the distribution system.

•When assessing reliability, all three factors should be considered.

•In order to measure the reliability, there are many reliability

indices.

•Each reliability index may be important for a different purpose.



RELIANILITY INDICES


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•There are over forty reliability indices.

•The most commonly used ones are described below.

1. SAIFI2. SAIDI

3. CAIFI

4. CAIDI

5. ASAI

•SAIFI and SAIDI are called system-oriented indices.

•CAIFI, CAIDI, ASAI are called customer-oriented indices.



SAIFI


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•It is called “System average interruption frequency index”.

•Definition: - it is defined as total number of customer interruptions

divided by total number of customer served.

‘λι’ is the failure rate, ‘Ni’ is the number of customers at load

point ‘i’. R is the set of load points in the system.




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SAIDI

•It is called “System average interruption duration index”.

•Definition: - it is defined as sum of customer interruption duration

divided by total number of customer.

‘Ui’ is the annual outage time.




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CAIFI

•It is called “Customer average interruption frequency index”.

•Definition: - it is defined as total number of customer interruptions

divided by total number of customers interrupted.

‘CN’ is the number of customers interrupted.



CAIDI


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•It is called “Customer average interruption duration index”.

•Definition: - it is defined as sum of customer interruption duration

divided by total number of customer interruption.



ASAI


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•It is called “Average service availability index”.

•Definition: - it is defined as customer hours of available service

divided by customer hours demanded.



CONCLUSION


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•Understanding how to correctly apply the IEEE standard reliability

indices is the first step in measuring the reliability of an electric

distribution system.

•The most difficult part of using reliability indices is to know how to

interpret the data and understanding what the performance indices

are really saying about the system performance.

•Finally, I conclude that if the values of these indices are closer to ‘1’,

then it is realized that the reliability of the distribution system is

increased.



REFERNCES


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[1] R.H.Lasseter, “Control of Distributed Resources”, Proceedings of

Bulk Power Systems Dynamics and Control IV, organized by IREP and

National Technical University of Athens, Santorini, Greece, Aug, 1998,

pp323-329.

[2] F. V. Edwards, G.J.Dudgeon, J.R.McDonald and W.E.Leithead ,

“Dynamics of Distribution Networks with Distributed Generation”,

Proceedings of the IEEE PES summer meeting 2000, pp.1032-1037.

[3] T. Ackermann, G. Andersson and L. Soder “Distributed

Generation: A definition” Electric Power System Research, Vol. 57, 2001

pp.195-204.




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