reliability indices for dhbvn

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Reliability indices for DHBVNSAIFI and SAIDI

Submitted through: Sambitosh Mohapatra, Executive Director

27 January 2012

Reliability indices for DHBVN Draft

Table of Contents

Introduction 3

Importance 3

Reliability of Power Supply and Consumer Satisfaction 3

Objective 3

Reliability Evaluation Criteria 4

SAIFI (System Average Interruption Frequency Index) 4

SAIDI (System Average Interruption Duration Index) 4

Limitations in Assessment of Consumer Supply Reliability 5

Factors Reckoned For Reliability Analysis 5

Computations 5

Conclusion 6

Data Table 7

PricewaterhouseCoopers Private Limited


Introduction

ImportanceThe distribution reforms have been identified as the key area for putting the power sector on the right track. The strategies identified are aimed at improving financial viability, reduction of sub T&D losses, improving customer satisfaction, increasing reliability and quality of power supply and adopting systems approach with MIS. Customer satisfaction is one of the objective under Restructured Accelerated Power Development & Reform Programme, a Government of India assistance cum loan intervention aiming at improvement of sub-transmission and distribution system in the country. Investment to the tune of Rs. 50,000 crores is proposed to be made by the Government of India towards IT implementation and distribution infrastructure strengthening.

Indirectly or directly customer satisfaction is concerned with improving and modernization of the T&D network. Customer satisfaction can be improved through providing better quality power in terms of voltage and frequency fluctuations and reliability by reducing outages. These necessarily call for technical intervention in, firstly, ensuring that the assets already created are maintained in proper working condition and secondly through augmenting the system. Further customer complaint redressal mechanism are to be made more responsive and proactive through building transparent and reliable system with the help of computerization. The system should be capable enough to meet the growing demand of information conscious customers.

When the expectation of the customer is more than the fulfillment there is resentment and the customer is reluctant to pay the bils. On the other hand when his expectations are met the customer is satisfied and he may be less reluctant to share marginal increase in the tariff.

Reliability of Power Supply and Consumer SatisfactionReliability of service needs to be always given primary importance by electricity distribution utilities. Consumer is least interested about the availability of power sources, grid conditions but he must be ensured a power supply, which is most reliable and qualitative. Reliability to a consumer means that power made available to him is fault free and the outage or interruptions are tolerable and do not disturb his normal life.

Reliability and quality of supply were rarely an issue till recent past and little or no attention was paid to the reliability and quality of power supply. But a change in attitude has been observed in the supplier as well as takers of energy and a customer friendly definition of reliability and benchmarking of performance has been laid down.

A reporting system for the reliability analysis to log type of consumer's interruption duration, number of consumer affected and reason for interruption with an aim to improve the reliability through adequate measures has become essential. Reliability analysis requires large amount of data regarding consumer interruption such as number of consumers affected, duration of interruption and the type of power cut viz. scheduled or unscheduled. The analysis can be made through a computer based software tool by measuring past performance, comparing with that of envisaged new system and predicting future performances. Creation of comprehensive up to date consumer index and system data basis on computerized environment is essential for efficient commercial and technical operation and management of any distribution system.

The R-APDRP programme has focused on this basic need and creation of such data base which is a prerequisite to reliability monitoring so as to identify the troublesome consumer and system element. Continuing reforms in the distribution sector with emphasis on consumer satisfaction there would be a time when customer will be compensated for poor performance of the utility



and utility will be awarded for their better performance through performance based tariff. Thus utility has to be more vigilant to improve its performance.

ObjectiveThe objective of reliability monitoring is manifold and is as follows:

Furnish management with performance data regarding the quality of customer service on the electrical system as a whole and for each voltage level and operating area.

Provide data for analysis to determine reliability of service in a given area (geographical, political, operating, etc) to determine how factors such as design differences, environment or maintenance methods, and operating practices affect performance.

To identify substations and feeders with substandard performance and to ascertain the causes and to take remedial measures accordingly.

Reliability Evaluation CriteriaAs per HERC (Standards of Performance for Distribution Licensee) Regulations 2004, the Commission has prescribed SAIDI, SAIFI and MAIFI as indices to monitor reliability of the distribution licensees in the state of Haryana. Both the distribution utilities are required to calculate these indices and report to the Commission on monthly/ quarterly basis. However, in our report we emphasise on SAIFI and SAIDI.

SAIFI (System Average Interruption Frequency Index)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.

In the absence of consumer indexing in the state of Haryana, it is difficult to have a correct no. of consumers connected to a particular feeder in a sub-division. HERC has therefore modified the formula for calculation of SAIDI as Standards of Performance for Distribution Licensee Regulations 2004.

SAIFI= ∑1N

(A i∗N i)

N t

Ai = Total no. of sustained interruptions (each longer than 5 minutes) on the ith feederfor the month

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

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

n = No. of 11kV feeders in the licensed area of supply (excluding those serving predominantly agricultural connections)

SAIDI (System Average Interruption Duration Index)SAIDI is more commonly known as "average customer minutes off supply" and is generally reported over a one-year period. It 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.

SAIDI= ∑1N

(B i∗N i)

N t

Bi = Total duration of all sustained interruptions on ith feeder for the month

Limitations in Assessment of Consumer Supply Reliability The limitations in measurement of these reliability indices is mainly due to the absence of IT based management information system and data reporting formats.

No Consumer Indexing No Computerised Based Trouble Call Management System No Data Base Of Consumers and System Lack of Awareness Of Utility Staff

Factors Reckoned For Reliability AnalysisThe reliability indices can be evaluated considering the following factors:

33 kV breakdowns 11 kV breakdowns Incoming supply failure at 66 kV, 132 kV or 220 kV substations. Daily rostering of 11 kV rural feeders. Failure of distribution transformers.

The following factors, which affect reliability indices, shall also be considered subject to availability of data:

Momentary interruptions on 33kV and 11kV feeders. Momentary incoming supply failures Pre-arranged shutdowns on lines and feeders Breakdown on LT feeders Blowing of transformer fuses both HV and LV individual fuse off calls



ComputationsFor computation of the reliability indices, two sub-divisions of urban, industrial and rural categories each shall be chosen in DHBVN’s area of supply. Data from these sub-divisions may be collected on daily basis as per the data sheet attached at the end of this report. It is to be noted that for computations of these reliability indices, feeders serving predominantly agricultural connections in urban and industrial sub-divisions are to be excluded.

The following sub-divisions have been chosen for calculation of reliability indices:

Civil lines s/div, Hisar (Urban) DLF s/div, Gurgaon (Urban) KCG Division, Gurgaon (Industrial) Industrial s/div, Ballabhgarh (Industrial) Sub urban s/div, Sirsa (Rural) Ateli s/div, Narnaul (Rural)It is pertinent to mention that the data from the sub-divisions shall be collected and SAIFI and SAIDI will be calculated on daily basis. However, for the purpose of analysis, the monthly value of SAIFI and SAIDI shall be considered.

ConclusionIn our country maintaining of power supply has gained momentum and utilities have started monitoring through the above indices. The reporting process of reliability indices must begin with monthly submission of these indices to the State Regulatory Commissions for publishing in the newspaper etc. These indices must be displayed in each work location. This process will reinforce the point that reliability issues at the work location do impact the overall utility programme and all efforts will be made to improve the same with a target bound programme.

Statistical approach to reliability monitoring will also assist the regulators to set more optimum performance standards so that the consumers are compensated for poor performance of the utility and the utillity is incentivised for more than expected performance. Reliability is a random process. It is to be seen how often these standards are violated and what corrective actions are taken to bring them within limits.



Data Table

Dakshin Haryana Bijli Vitran Nigam

Name of Sub-division

Type of Sub-division Rural Agri/Rural Domestic/Urban/Industrial

Date

Month

Year

S. No. Name of Feeder

Name of feeding sub-

station

Connected load of

Feeder (kW)

Interruptions above 5 minutes

Interruptions of 5 minutes & below

No. of Interruptions

Duration in minutes

No. of Interruptions

Duration in minutes

1 Feeder 1

2 Feeder 2

3 Feeder 3

4 Feeder 4

5 Feeder 5

6 Feeder 6

7 Feeder 7

8 Feeder 8

9 Feeder 9

10 Feeder 10

11 Feeder 11

12 Feeder 12

13 Feeder 13

14 Feeder 14

15 Feeder 15

16 Feeder 16

17 Feeder 17

18 Feeder 18

19 Feeder 19

20 Feeder 20

Total

Note: Breakdowns/ shutdowns/ trippings on voltage levels of 33kV, 66kV, 132kV and 220kV should be included to calculate the frequency and duration of interruptions for each 11kV feeder affected due to such interruptions

Total Connected load of Sub-division (kW)


reliability indices for dhbvn

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