RELIABILITY OF DISTRIBUTION SYSTEM

[seminar class]

presented by:
Yogesh Ranjan Mishra

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TECHNICAL SEMINAR PRESENTATION-2011
INTRODUCTION
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 that system’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
• 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, and electric power distribution systems, in particular.
• Reliability concerns are often split into three categories:
- Adequacy
- Security
- Quality
HOW TO MEASURE RELIABILITY ?
• 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 is determined 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
• There are over forty reliability indices.
• The most commonly used ones are described below.
1. SAIFI
2. SAIDI
3. CAIFI
4. CAIDI
5. ASAI
• SAIFI and SAIDI are called system-oriented indices.
• CAIFI, CAIDI, ASAI are called customer-oriented indices.
SAIFI
• 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.
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.
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
• 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.