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Power Development DepartmentJammu & Kashmir Government

Presentation On Performance of Distribution

System

December, 2013

Introduction Consumer satisfaction is an important aspect of any Distribution Utility. Performance of a distribution system is determined from the reliability and the quality of the power it supplies. Both of these parameters are equally important for consumer satisfaction.

Quality of power supply is determined from the profile of voltage and frequency which are maintained by management of Reactive Power and Active Power respectively. Therefore the quality of supply is purely maintained by technical means.

Reliability of power supply needs not only the technical means like auto reclosure facilities in the network, it essentially requires mobilizing the man power to minimize the number of interruptions and to clear the interruptions as early as possible.

Reliability of power supply can be improved by meeting following objectives:

1. Reducing the occurrence of interruptions. 2. Reducing the duration of an interruption. In order to quantify these two objectives, J&K SERC

introduced certain performance indices in its ‘J&K (Distribution Performance Standards) Regulation’ 2006 on the pattern of distribution utilities of other states.

How to improve the system reliability

Reliability indices of distribution systemAmong various performance indices there are two main indices which are indicatives of supply reliability. These indices are: 1. System Average Interruption Frequency Index (SAIFI) and; 2. System Average Interruption Duration Index (SAIDI).

By definition, SAIDI is the total of interruption duration in minutes per year per customer experienced by customers for both planned and unplanned interruptions. A SAIDI of 200 minutes means that customers connected to the feeder or supply area being measured experience in average 200 minutes off supply in 12 months. Likewise, SAIFI is a measure of how often an average customer loses supply during one year. A SAIFI of 3 means that the average customers connected to the feeder or supply area being measured on average lost supply thrice during the past 12 months.

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SAIDI, is determined by the formula; n

SAIDI = ∑ (Bi x Ni) / Nt i=1

Where, Bi = Total duration of all sustained interruptions (each longer than 5 minutes) on ith feeder for the month.

Ni = Connected load of ith feeder affected due to each interruption

Nt = Total connected load at 11kV in the Distribution utility’s/licensee's supply area

n = Number of 11kV feeders in the utility’s/licensee’s supply area (excluding those serving predominantly agricultural load)

Similarly, SAIFI is determined by the formula,n

SAIFI = ∑(Ai x Ni) / Nt i=1 i=1 Where, Ai = Total number of sustained interruptions (each longer than 5 minutes) on ith feeder for the month and other parameters have same meaning as given above.

How to determine SAIFI & SAIDI quantitatively

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Approach for calculation of SAIDI & SAIFI

The reliability indices, SAIDI & SAIFI may be determined conveniently for any given EM&RE division. The indices can be determined from the information available as per the following table:

Name of Sub Transmission Division:……………………………Total number of 11kV feeders………………........Total connected Load for the division (MW)...

Based on this information, SAIDI and SAIFI can be determined by using the prescribed formulae.

S. No Name of 11kV feeder

Connected Load (MW)

No. of sustained interruptions (>5 min duration) for last three months (Ai)

Total duration of all the interruptions (> 5 min) on the feeder (Bi)

Connected Load (MW)

(Ni)

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IllustrationName of EM&RE Division: XTotal number of 11kV feeders: 5Total connected Load for the division (MW)= 20MW

S. No

Name of 11kV feeder

Connected Load (MW) Ni

No. of sustained interruptions (>5 min duration) for last three months (Ai)

Total duration of all the interruptions (> 5 min) on the feeder in minutes (From Log sheet) (Bi)

AixNi

BixNi SAIFI of the Feeder

SAIDI of the Feeder

1 A 4 15 80 60 320 3 16

2 B 6 8 58 48 348 2.4 17.4

3 C 3 12 84 36 252 1.8 12.6

4 D 5 5 42 25 210 1.25 10.5

5 E 2 7 52 14 104 0.7 5.2

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Illustration

From this information, Sum of AixNi= 183Sum of BixNi= 1234 SAIFI= 183/20 = 9.15SAIDI=1234/20 = 61.70It means that on an average there are more than nine interruptions experienced by the consumers of the division X and it has taken an average time of more than an hour for the staff to resume the supply.

The information shall be given separately for Rural and Urban Receiving Stations.

MONTHLY RURAL POWER SUPPLY POSITION

Month & Year:

Name of State

Number of Distribution

Companies in the State

Name of Distribution Company

Total electrified villages Average hours of power

supply to rural areas in the

month

Energy supplied to

rural areas in the month

(MU)No. of inhabitated villages

No. of electrified villages

Thanks to all the Officers for participation and wish everyone encouraging SAIFI & SAIDI figures for his

division.