In order to evaluate the performance of sub-transmission and distribution system and ascertaining the benefits accrued out of various schemes implemented in Coimbatore Circle in quantifiable terms, a benefit analysis was carried out for the following works done as per scheme:
• Reconductoring of 11 kV feeders;
• Replacement of old equipment in substation;
• Installation of fixed LT capacitors on distribution transformer secondary; and
•Replacement of consumer EM meters with high quality electronic meters.
We first describe the methodology followed for the analysis for each work.
Methodology Followed
•Reconductoring of 11 kV Feeders
− Two sample 11 kV feeders were selected where reconductoring had been done.
− The list of all consumers was collected for both feeders.
− The period of reconductoring was obtained from the field offices.
− The benefit analysis period was chosen as 6 months before the start of reconductoring and 6 months after the completion of
reconductoring.
− Data on energy input at 11 kV side of the feeders and energy sales at the consumer was collected.
− Saving in energy was calculated as the reduction in loss. Energy loss before and after reconductoring was worked out based on
above.
Replacement of Old Equipment
•Reliability improvement and reduction of outages were carried out on two feeders to assess the benefit of replacement of old equipment:
− A primary substation where old equipment had been replaced was selected from where two 11 kV feeders were emanating.
− The periods of replacement of old equipment, e.g., VCB, CT and C&R panels, were ascertained from field offices.
− The benefit analysis period was chosen 6 months before the change and 6 months after the change of the old equipment.
− Feeder outage details were collected for the selected period from the field offices.
− The total number of consumers from 11 kV feeders was ascertained.
− Improvements in Consumer Interruption Frequency Index and Customer Interruption Duration Index were calculated for both the
periods.
− Results were compared to evaluate the benefits.
Installation of Fixed LT Capacitor at DTR Secondary
The aim was to assess the benefit of addition of LT capacitor banks at DTR secondary in quantifiable terms. For this purpose, it was proposed to take readings of different 11 kV feeders with capacitor banks in switched on and switched off conditions.
−Two 11 kV feeders were identified where LT capacitors were installed at all DTR secondaries.
− The names of primary substation and division were noted.
− The list of DTRs was collected for each 11 kV feeder.
− The total energy sent on 11 kV feeders was noted from respective PSSs on a particular day with capacitor banks in switched on
condition.
− Energy meter readings for each DTR were taken on the same day and approximately at the same time by different groups.
− Another set of readings of energy sent on 11 kV feeder and energy meter readings at DTR secondary were noted after a gap of
7 days.
− Another set of readings were noted on the same 11 kV feeder with capacitor banks in switched off condition with a gap of 7 days.
− From the readings, the total energy sent from primary substation and energy received at DTR secondary was worked out during the
two 7 day periods.
− Loss of energy in units was calculated for both the 11 kV feeders with and without capacitor banks.
− Reduction in loss with capacitor installation was worked out as the benefits accrued.
Replacement of Consumer EM Meters with High Quality Meters
Metering benefit analysis for change of meters was carried out on one 11 kV feeder.
− A sample of 131 consumers with various consumption patterns covering all the seven sectors of Somanur division was selected.
− Period of change of meter from EM type to High Quality type was noted from field offices.
− Energy consumption data was collected for 6 months before and 6 months after change of meters having the band in which meters
were changed.
− Increase in the metered consumption after change of meters was worked out as the benefit.
Pre-requisite of Site/Preparedness/Constraints
• S.E. Office of Coimbatore (S) involved concerned engineers in selection of
11 kV feeders for benefit analysis. Concerned field offices were visited andthe required information, e.g., length of 11 kV feeders, feeder lengths,number of DTRs, number of consumers, etc. was gathered through the field staff of TNEB.
• S.E. Office organized 6 to 7 groups of workforce to work in tandem for taking DTR meter readings simultaneously.
• DTR meter reading were taken within 30 minutes duration and the average of feeder meter readings at the start and finish of DTR meter readings was considered for the feeder reading.• The feeder was cut-off for 13 hours and 7 1⁄2 hours duration for general maintenance when the readings with capacitors were being taken.(During this period, alternate supply was not made available to consumers.)
• The energy readings were proportionately adjusted to match with the hours considered for without capacitor case.
• During LT capacitor benefit measurement, time duration of 7 days was considered for taking readings with and without capacitors so as to capture the effects changes in load pattern.
• In order to reduce time of measurement, the final reading with capacitor was considered to be same as the initial readings without capacitors.
• The rate of consumption of unmetered consumers, i.e., agricultural and hut services was kept constant before and after reconductoring.
Benefit Analysis
•Benefit of Reconductoring
The following feeders were taken for benefit analysis of reconductoring:
1. 11 kV Semmandapalayam Feeder from Somanur PSS, and
2. 11 kV Neelambur feeder from Arasur PSS.
We present the results in Table
• Reconductoring of 11 kV feeders;
• Replacement of old equipment in substation;
• Installation of fixed LT capacitors on distribution transformer secondary; and
•Replacement of consumer EM meters with high quality electronic meters.
We first describe the methodology followed for the analysis for each work.
Methodology Followed
•Reconductoring of 11 kV Feeders
− Two sample 11 kV feeders were selected where reconductoring had been done.
− The list of all consumers was collected for both feeders.
− The period of reconductoring was obtained from the field offices.
− The benefit analysis period was chosen as 6 months before the start of reconductoring and 6 months after the completion of
reconductoring.
− Data on energy input at 11 kV side of the feeders and energy sales at the consumer was collected.
− Saving in energy was calculated as the reduction in loss. Energy loss before and after reconductoring was worked out based on
above.
Replacement of Old Equipment
•Reliability improvement and reduction of outages were carried out on two feeders to assess the benefit of replacement of old equipment:
− A primary substation where old equipment had been replaced was selected from where two 11 kV feeders were emanating.
− The periods of replacement of old equipment, e.g., VCB, CT and C&R panels, were ascertained from field offices.
− The benefit analysis period was chosen 6 months before the change and 6 months after the change of the old equipment.
− Feeder outage details were collected for the selected period from the field offices.
− The total number of consumers from 11 kV feeders was ascertained.
− Improvements in Consumer Interruption Frequency Index and Customer Interruption Duration Index were calculated for both the
periods.
− Results were compared to evaluate the benefits.
Installation of Fixed LT Capacitor at DTR Secondary
The aim was to assess the benefit of addition of LT capacitor banks at DTR secondary in quantifiable terms. For this purpose, it was proposed to take readings of different 11 kV feeders with capacitor banks in switched on and switched off conditions.
−Two 11 kV feeders were identified where LT capacitors were installed at all DTR secondaries.
− The names of primary substation and division were noted.
− The list of DTRs was collected for each 11 kV feeder.
− The total energy sent on 11 kV feeders was noted from respective PSSs on a particular day with capacitor banks in switched on
condition.
− Energy meter readings for each DTR were taken on the same day and approximately at the same time by different groups.
− Another set of readings of energy sent on 11 kV feeder and energy meter readings at DTR secondary were noted after a gap of
7 days.
− Another set of readings were noted on the same 11 kV feeder with capacitor banks in switched off condition with a gap of 7 days.
− From the readings, the total energy sent from primary substation and energy received at DTR secondary was worked out during the
two 7 day periods.
− Loss of energy in units was calculated for both the 11 kV feeders with and without capacitor banks.
− Reduction in loss with capacitor installation was worked out as the benefits accrued.
Replacement of Consumer EM Meters with High Quality Meters
Metering benefit analysis for change of meters was carried out on one 11 kV feeder.
− A sample of 131 consumers with various consumption patterns covering all the seven sectors of Somanur division was selected.
− Period of change of meter from EM type to High Quality type was noted from field offices.
− Energy consumption data was collected for 6 months before and 6 months after change of meters having the band in which meters
were changed.
− Increase in the metered consumption after change of meters was worked out as the benefit.
Pre-requisite of Site/Preparedness/Constraints
• S.E. Office of Coimbatore (S) involved concerned engineers in selection of
11 kV feeders for benefit analysis. Concerned field offices were visited andthe required information, e.g., length of 11 kV feeders, feeder lengths,number of DTRs, number of consumers, etc. was gathered through the field staff of TNEB.
• S.E. Office organized 6 to 7 groups of workforce to work in tandem for taking DTR meter readings simultaneously.
• DTR meter reading were taken within 30 minutes duration and the average of feeder meter readings at the start and finish of DTR meter readings was considered for the feeder reading.• The feeder was cut-off for 13 hours and 7 1⁄2 hours duration for general maintenance when the readings with capacitors were being taken.(During this period, alternate supply was not made available to consumers.)
• The energy readings were proportionately adjusted to match with the hours considered for without capacitor case.
• During LT capacitor benefit measurement, time duration of 7 days was considered for taking readings with and without capacitors so as to capture the effects changes in load pattern.
• In order to reduce time of measurement, the final reading with capacitor was considered to be same as the initial readings without capacitors.
• The rate of consumption of unmetered consumers, i.e., agricultural and hut services was kept constant before and after reconductoring.
Benefit Analysis
•Benefit of Reconductoring
The following feeders were taken for benefit analysis of reconductoring:
1. 11 kV Semmandapalayam Feeder from Somanur PSS, and
2. 11 kV Neelambur feeder from Arasur PSS.
We present the results in Table
 |
| Benefits of Reconductoring |
•Reliability Improvement Benefit
1. Primary Substation 110 / 33-11 kV Somanur
2. 11 kV outgoing feeder Kombakkadu Semmandapalayam
3. No. of Consumers 4136 3466
4. Equipment changed on 28.10.02 09.05.03 (VCB, CT, Relay, Panel, etc.)
5. Benefit analysis period
Before April’02-Sept’02 April’02-Sept’02
After Oct’03-Mar’04 Oct’03-Mar’04
6. Consumer Interruption Frequency Index
(a) ∑ No. of consumers having no power supply in each interruption/Total no. of consumers served
1. Primary Substation 110 / 33-11 kV Somanur
2. 11 kV outgoing feeder Kombakkadu Semmandapalayam
3. No. of Consumers 4136 3466
4. Equipment changed on 28.10.02 09.05.03 (VCB, CT, Relay, Panel, etc.)
5. Benefit analysis period
Before April’02-Sept’02 April’02-Sept’02
After Oct’03-Mar’04 Oct’03-Mar’04
6. Consumer Interruption Frequency Index
(a) ∑ No. of consumers having no power supply in each interruption/Total no. of consumers served
(b) Benefit = 25 / month – 13 / month = 12 / month
7. Consumer Interruption (Duration)
(a)∑ No. of consumer having no power supply x duration of interruption/Total no. of consumers served
Before Replacement After Replacement 36 Hrs. 49 Min. / Month 15 Hrs. 58 Min. / Month
(b) Benefit = 36 Hrs. 49 Min. – 15 Hrs. 58 Min. = 21 Hrs.
(Reduction in Interruption duration)
•Benefit Analysis of Capacitor
Besides the power quality, reliability, performance and quantifiable/measurable ways of benefits assessment, and understanding the
performance indicators stated above, the power distribution engineers do have to think of reactive power control in distribution system for its efficient operation
DTRs of different capacity are installed from the range of 50 kVA to 750 kVA in Coimbatore (S).
Sample feeders taken for benefit analysis of capacitors are:
− 11 kV TSR layout feeder from Kumar Nagar PSS;
− 11 kV Muthian Koil feeder from Sandaipettai PSS.
7. Consumer Interruption (Duration)
(a)∑ No. of consumer having no power supply x duration of interruption/Total no. of consumers served
Before Replacement After Replacement 36 Hrs. 49 Min. / Month 15 Hrs. 58 Min. / Month
(b) Benefit = 36 Hrs. 49 Min. – 15 Hrs. 58 Min. = 21 Hrs.
(Reduction in Interruption duration)
•Benefit Analysis of Capacitor
Besides the power quality, reliability, performance and quantifiable/measurable ways of benefits assessment, and understanding the
performance indicators stated above, the power distribution engineers do have to think of reactive power control in distribution system for its efficient operation
DTRs of different capacity are installed from the range of 50 kVA to 750 kVA in Coimbatore (S).
Sample feeders taken for benefit analysis of capacitors are:
− 11 kV TSR layout feeder from Kumar Nagar PSS;
− 11 kV Muthian Koil feeder from Sandaipettai PSS.
 |
| Energy Savings |
In Table , we present the energy savings accruing from these measures.
•Benefit for Change of Consumer EM Meter to High Quality Electronic Meter
Metering benefit analysis for change of consumer meters was done in Somanur Division (Table).
•Benefit for Change of Consumer EM Meter to High Quality Electronic Meter
Metering benefit analysis for change of consumer meters was done in Somanur Division (Table).
 |
| Metering Benefit Analysis |
% Savings (benefit)
= Savings in units/Total energy before change of meter
= 13.4%
Software tools were applied to calculate the result of load flow studies.
= Savings in units/Total energy before change of meter
= 13.4%
Software tools were applied to calculate the result of load flow studies.
 |
| Result of Load Flow Studies |
Constraints of Benefit Evaluation
The system conditions change continuously so the benefits estimates are to be ascertained in given operating conditions. Otherwise they will not be exactly reflected at the time of measurement. Some of the conditions which affect the benefits are:
loading pattern;
voltage profile;
season of the year;
connectivity of the distribution network; and
accuracy of metering system, i.e., CT, PT, Meters; and
installation workmanship.
Even though savings in energy loss are observed due to the implementation of the envisaged corrective actions through schemes, the monetary benefits may not be achieved equivalent to the cost of energy saved in the financial performance of the circle. Some of the extraneous factors such as the role of regulator in tariff fixation, the policies followed by the government with regard to supply of power to BPL rural, agricultural consumers, etc. and other factors affect the overall AT&C losses and hence costs and savings.
In the above case study, we have described the benefits accrued from four steps, viz., reconductoring, replacement of old equipment, capacitor installation and Electronic Metering.On the basis of this information, you can draw the turnkey specifications and demand such benefits from turnkey contractors upon project implementation.This requirement / acceptance of concept of turnkey bidding will take considerable time for Utilities to impose and Contractors to accept. Meanwhile, individual turnkey contracts for each of these activities are already under way in various utilities. This case study has been specifically included in this unit so that utilities could initiate new endeavours along these lines in the decades to come and facilitate the changes coming up in the power generation – distribution system of the 21 st Century.
List the specifications for turnkey contracts for all four steps mentioned above.
You would agree that power distribution companies should understand and be responsible for their performance. You will learn about the performance benchmarks and the features that the consumers, electricity authorities and regulators are demanding from power utilities While shifting to the turnkey contracts and scheme implementation, the utilities haveto consider the key performance indicators that they are responsible for as well as to the extent these could be achieved through better contracts in future. The Indian power distribution industry is continuously evolving and all the stakeholders have to apply their collective wisdom to achieve the aimed objectives. The turnkey contracts will definitely reduce the burden of implementation that prevails in unit rate contracts and utilities can divert their efforts for meeting the challenges that are being encountered by the power distribution sector in India.
The distribution operators are expected to carry out their responsibilities at minimum cost but greater efficiency. However, the service quality is interdependent. The generating stations play a key role in active voltage management. The distribution network operator’s role lies in reactive support and load curtailments (through demand side management options).The concept of turnkey contracts will primarily make the bidders,manufacturers, suppliers and all those who contribute in erection and maintenance of distribution network to be part of the system. In unit rate contract system, most of the organizations have been operating as “Outsiders” to utilities. Therefore, although the concept of turnkey contract may seem quite complex at present in the years to come, all stakeholders will have to be performance oriented in the regulatory regime and the turnkey contracts would be a better option. The skill and competence of the utility lie in drawing up the “Turnkey Specifications “. This exercise has to be done with clarity making demands on the equipment quality, timely delivery and system performance. The reform process obviously has a long way to go!
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