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Distribution System Reliability and SystemBenchmarking

12/02/08

11:00 12:30

Sallehhudin Yusof

Advanced Power Solutions (APS), Malaysia


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Scope of the Presentation

1) Distribution system reliability

2) Distribution system reliability benchmarking


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Contents

1) Introduction

2) Review of reliability indices

3) Reliability performance reporting

4) Reliability analysis in network planning and design

5) Fundamental of Benchmarking


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Introduction


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Determination of Distribution Reliability

Motivations/Objectives

a) To gauge/measure customer satisfaction

b) Improve system performance

c) Basis for network expansion planning

d) Comply with regulatory requirements

f) Maintenance scheduling and Resource allocation


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What is Reliability?

Reliability is the ability of the power delivery system tomake continuously available sufficient voltage, ofsatisfactory quality, to meet the consumers needs


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Electric Utility Reliability of Supply

1) What should be measured?

2) What level of performance should be promised?

3) How should performance be monitored?

4) How should performance standards be enforced?


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Review of Reliability Indices


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Reliability Indices

1) Reliability indices measure the performance of anentire utility or parts of its system;

2) Usually, such indices are evaluated on a monthly and

annual basis (Did we do better this year? or Worse?)


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Factors Typically Considered for Reliability Indices

1) The number of customers served and affected;

2) The connected load;

3) The duration of the interruption measured in, minutes,hours, or days;

4) The amount of power (kVA/kW) interrupted; and

e requency o n errup ons.


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Basic terms for Outages and Interruptions

1) Outage a failure of part of the power supply system for example a line down, transformer out of service, ora circuit breaker that opens when it shouldnt.

2) Interruption a cessation of service to one or morecustomers. An interruption is the result of one or morecomponent outages.


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Types of Outages

1) Forced outage. An outage that results from emergencyconditions directly associated with a component requiring that it betaken out of service immediately, either automatically or as soonas switching operations can be performed, or an outage caused by

improper operation of equipment or human error.2) Scheduled outage. An outage that results when a component is

deliberately taken out of service at a selected time, usually forur ose of construction, reventive maintenance, or re air.

3) Transient forced outage. An outage whose cause is immediatelyself-clearing so that the affected component can be restored toservice either automatically or as soon as a switch or circuitbreaker can be reclosed or a fuse replaced.


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Note: With permission of TNB Distribution


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Interruptions

1) Interruption duration. The period from the initiation of aninterruption to a consumer until service has been restored to thatconsumer.

2) Scheduled interruption. An interruption caused by a scheduled

outage.

3) Forced interruption. An interruption caused by a forced outage.

4) Momentary interruption. An interruption of duration limited to the

controlled switching operations or by manual switching at locationswhere an operator is immediately available.

5) Sustained interruption. Any interruption not classified as amomentary interruption. Any interruption longer than 1/5 minutes


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