AT&C Loss Reduction in Electrical Distribution System by Implementation of HVDS 1 Bhausaheb Prakash Patil, 2 Shridhar S. Khule 1 PG Student and 2 Head of Department 12 Department of Electrical Engineering 12 Matoshri College of Engineering & Research Centre Eklahare, Nashik, Maharashtra, India. 12 Savitribai Phule Pune University, Pune Abstract This paper presents a methodology for improvement the distribution system by minimizing aggregate technical and commercial losses. In India, aggregate Technical & commercial losses have been officially indicated as 24.62% of electricity generated. Most of the utility companies in india are victims of major revenue losses due to technical and commercial energy losses. The commercial losses are like electricity theft, unauthorized connections, irregular billing and the technical losses are I2R power losses. These losses affect the quality of power supply in terms of voltage and more tariffs imposed on genuine customers. To solve the issues related to high losses in the distribution stage of power system for agricultural loads of rural areas, High Voltage Distribution System (HVDS) has been proposed. In HVDS many small number of distribution transformer are used instead of a large rated distribution transformer as use in case of LVDS. In HVDS scheme LV lines are replaced by High Voltage (HV) lines up to the Distribution Transformer (DTR). Maximum 2 or 3 no s of consumer service mains connected to directly DTR or through very short length of LT lines of AB cable (Aerial bunch cable). Hence unauthorized hooking of loads is impossible as LT lines are very short & insulated with AB cable. Keywords : AT&C- Aggregate Technical and Commercial, DTC Distribution Transformer Centre, HVDS High Voltage Distribution System, AGR Agriculture, LVDS Low Voltage Distribution System, DTR Distribution Transformer, AB cable- Aerial bunch cable I. INTRODUCTION As Electricity generated at 11kV is transmitted at higher voltages of the order 132kV or more hence losses are very low, but problem arises when this higher voltage is stepped down to 11kV or even lower voltages for distribute among the consumers at low voltage where current increases and causes line losses in the system. When the system uses 433V for distribution this is called as low voltage distribution system (LVDS). When this LVDS supplies power to agricultural consumer pump sets although supplied for 8-10Hrs. it incurs huge technical and non-technical losses. The losses prevailing in the power distribution system can be categorized into two types a) Technical losses b) commercial (Non-Technical losses). Technical losses on distribution system are due to current passing through conductors and magnetic losses in transformers resulting in heat dissipation. Technical losses occur during transmission and distribution involves lines, transformer, and substation related losses. The losses are due to energy dissipated in the conductors and transformers used for distribution of power. Commercial losses or the non-technical losses are power theft, insufficient metering and billing add heavily to the aggregate losses. Experience in many parts of the distribution sector demonstrates, that it is possible to reduce the losses in a reasonably short period of time and that such investments have a high internal rate of return. In the existing low voltage distribution network the voltage profile is poor; losses are high and on taps are also high. To improve the quality of supply recommendations is to implementation of HVDS with small capacity DOI:10.23883/IJRTER.2018.4355.Q81IW 49
distribution transformers. Under this system HV line i.e.,11 kv line is extended up to or near to the load as possible and erect small capacity distribution transformer, say 6.3, 10, 15 kva extend supply to the consumer through a short length of LV line preferably insulated overhead cable popularly known as Aerial Bunched Cable (ABC) A. Drawbacks of LVDS Due to running lengthy distribution lines at low voltage to feed the tail end consumer. Which draw large current. Due to frequent faults, more failures in distribution transformer and its maintenance and repair requires high expenditure. Due to delay in replacement of failed distribution transformers, there is a great loss in standing crops. Unauthorized hooking or tapping the bare conductors of low tension feeder or tampered service lines and monitoring of low voltage feeders is really very difficult. In case of any failure in three-phase large capacity distribution transformer, entire unit is to be replaced which consumes more time. High quantum of I 2 R losses. DTR failures due to frequent faults. High Rating Distribution Transformers are required to supply the Power to the consumers. As low Voltages are transmitting to large distances, the voltage profile at the load ends is decreasing. More resistive loss is present because of low voltage profile. Improper load management results in overloading of conductors and transformers. Monitoring of unauthorized hooking or tapping the bare conductors is of LT lines is more difficult. Nobody owns the transformer since everybody thinks that others will take care of the transformer. B. Analysis of Reasons of High Losses in LVDS The loss which occurs in distribution network is given by P = 3 I ^2 R L. The three factors having impact on loss are: 1. Current flowing through network. 2. Resistance of network. 3. Length of network. Another factor that has impact on losses is resistance of conductor used for supply of electricity. The resistance is directly proportional to resistivity of material used for design and inversely proportional to square of the cross sectional area. In existing system of LVDS GNAT type of conductor is used for which resistance constant is 1.1566 ohm/km at 40 degree centigrade. In this technique of conversion of LVDS to HVDS we are changing the type of conductor. In HVDS system WEASEL 0.03 is used for supplying electrical energy for which resistance constant is 0.977 ohm/km at 40 degree centigrade. C. Benefits of HVDS LV system losses can be minimized to the lowest level. Pilferage can be minimized by introducing this system. Comparative analysis of reconfiguration of existing LV distribution system with HVDS concepts. The registered customers will feel ownership and take responsibility. Failure will be minimal because of no over loading and no middling of LT lines. @IJRTER-2018, All Rights Reserved 50
In the event of equipment failure only limited number of customers will get affected instead of maximum customers in original system. Customer has sense of ownership. Prevention of unauthorized loads is more effective. Considerable reduction in the line losses are there and consequent there is savings in power purchase cost. No additional generation capacity is needed for giving new loads due to reduction in power drawls. Since the losses are reduced considerably, power can be supplied to additional loads without any further investment of infrastructure. Low ratings KVA Distribution Transformers are enough to supply loads. Voltage profiles at the loads will be improved, as the DTR s are near to the load centers. As High Voltage is transferred near to the loads, the power loss will be less. Agricultural Motor burnouts will be eliminated because of good Voltage profiles. Reliability of the system can be increased. High quality of power supply earns total consumer satisfaction. II. PROPOSED METHODOLOGY In this paper 11 KV AGR feeder originating from 33/11 KV Sub Station is converted in to HVDS as follows, Existing LT network on each DTC is reconfigure as High Voltage Distribution network i.e. 11 KV network. 11 kv line is taken as near to the loads as possible. LT power supply is fed by providing appropriate capacity transformer and minimum length of LT line. It consists of replacement of existing three phase distribution transformer with small capacity transformers. Long length LT mains are converted into 11 kv mains by using existing support and thereby installing the appropriate capacity distribution transformer as near as to the load. A. Case Study of LVDS To carry out one feeder located at Samangaon, Maharastra is considered. This 11 feeder is supplying power to 7 agricultural consumer through a 63KVA transformers is replaced by smaller capacity 6.3KVA, 10KVA & 15 KVA DTRs. The resistance of line is 0.544 Ω/KM. Calculations are not considering any uncertainty in parameters. Power loss Calculations: Primary voltage = 11KV, Secondary Voltage = 433V Capacity of DTR = 63KVA and P.F. = 0.8 Primary Current = 4.13A Secondary Current = 105A No. of loads connected on 63KVA DTR = 7Nos @IJRTER-2018, All Rights Reserved 51
Node Load in HP Load in KW International Journal of Recent Trends in Engineering & Research (IJRTER) TABLE I Calculation of low voltage side losses of 63KVA DTR Length of LT line from conn to conn Total Length LT line from conn to DTR Current of Each Pump Current in LT line in Amp Loss watt 1 10 7.4 0.24 0.24 12.98 68.13 1818.06 2 10 7.4 0.24 0.48 12.98 55.15 2382.61 3 5 3.7 0.18 0.66 6.49 42.17 1915.45 4 7.5 5.6 0.18 0.84 9.73 35.68 1745.22 5 7.5 5.6 0.3 1.14 9.73 25.95 1252.85 6 7.5 5.6 0.12 1.26 9.73 16.22 540.99 7 5 3.7 0.12 1.38 6.49 6.49 94.86 52.5 39 9750.04 Sample calculation of power loss Power loss = 3I 2 * Resistance per KM * Length of the line in KM LT Line Losses per annum: Agricultural loads are supplied for a period 8 Hrs. in Maharashtra. So I 2 R losses are calculated as So, per annum loads are supplied for 365*8=2920Hrs. Hence total power loss per annum =total power loss in LT Side*No. of hours power supplied to loads. =(2920*9750.04)/1000=28470.11 units LT Transformer Losses: TABLE II 63KVA TRANSFORMER LOSSES No Load Loss in Watts 290 Full Load Copper Loss in Watts 1250 No load loss per annum = (365*8*290)/1000 = 731units. Full load copper loss per annum = (365*8*1250)/1000 =3650 units. Total Transformer loss per annum=4381 units. Loss due to Pilferage: It is assumed that 10% of total load is stolen in the form of unauthorized connections. Total loss per annum due to theft =total load*8*365*0.10=11388 units. So net LT losses = 44239.11 units. B. Losses in HVDS HT Transformer losses: System is restructured by replacing 63KVA DTR with 7 no.10kva DTRs to supply the same number of consumers. For 10KVA DTR as per standards no load and full load loss are given below in the table. TABLE II 10KVA TRANSFORMER LOSSES No Load Loss in Watts 40 Full Load Copper Loss in Watts 225 in @IJRTER-2018, All Rights Reserved 52
HT transformer losses per annum =((265*10)*8*365)/1000=7738 units. Losses due to pilferage are almost nil as High voltage as well as aerially bunched cables are used. Total HT transformer loss=7738 units. HT Line loss: HT line is given by = (V2/V1) 2 LT line losses per annum = (433/11000) 2 LT line losses per annum =44.11units. Total HT Loss =7782.11 units. Net Reduction in loss after switching to HVDS is 44239.11-7782.11=36457 units If Cost per unit is Rs.7.35 then annual saving would be 6.50*36457 = Rs.236970.5 C. Investment on HVDS If a 10KVA Transformer costs Rs.90207 then for 7 nos DTRs total cost=rs631449/- Conversion cost for LT pole structure into HT pole Structure for HVDS scheme is Rs.94742 per km. Hence conversion cost = 1.38 94742 = 130743.96 Total Investment is Rs.762192.96 Payback Period = Investment on HVDS/ Annual Saving due to HVDS = 762192.96/236970.5 = 3.21 Years D. Comparison of LVDS with HVDS System Parameter LVDS in Units HVDS in Units Net savings in units Line Losses 28470.11 7782.11 20688 Transformer Losses 4381 7738-3357 Total Losses 32851.11 15520.11 17331 III. CONCLUSION In this paper, following conclusions are drawn; The conversion of LVDS into HVDS system results in increase in energy savings & reduction in losses. Losses in transformation stages are increases but it s quite low as compared to losses reduced in line. It will bring the commercial viability in the power distribution companies of state. REFERENCES I. S. SRIKANT, PRASANTA KUMAR JENA, AKHILESH TIWARI, KUMAR GOSWAMI, AN INTERVALARITHAMATIC BASED COMPUTATION OF LOSSES AND PAYBACK PERIOD IN HIGH VOLTAGE DISTRIBUTION SYTSEM, 2017 4 TH UTTAR PRADESH SECTION INTERNATIONAL CONFERENCE ON ELECTRICAL, COMPUTER AND ELECTRONICS(UPCON)GLA UNIVERSITY; MATHURA OCT 26-28,2017, PAGES: 124-129 (2017) II. III. N.THIRUPATAIAH AND N.SAIKRISHNAPRASAD, MINIMIZATION OF DISTRIBUTION LOSSES BY IMPLEMENTING HIGH VOLTAGE DISTRIBUTION SYSTEM IN REAL TIME APPLICATIONS, INTERNATIONAL JOURNAL OF EMERGING TRENDS IN ENGINEERING RESEARCH (IJETER), VOL. 3 NO.6, PAGES: 453-460 (2015 RITULA THAKUR AND PUNEET CHAWLA, HIGH VOLTAGE DISTRIBUTION SYSTEM (HVDS)-AN ALTERNATE FOR IMPROVEMENT OF VOLTAGE DROP, PROFILE INTERNATIONAL JOURNAL OF ENGINEERING TECHNOLOGY, MANAGEMENT AND APPLIED SCIENCES, JANUARY 2015, VOLUME 3 ISSUE 1. @IJRTER-2018, All Rights Reserved 53
IV. DEMBRA, AMIT, AND A. K. SHARMA. "HIGH VOLTAGE DISTRIBUTION SYSTEM FOR AGRICULTURAL FEEDERS IN DISTRIBUTION SYSTEM." INTERNATIONAL JOURNAL OF ENGINEERING RESEARCH AND REVIEWS ISSN (2014): 1-8. V. SPANDANA, K., L. NIKHITA, AND R. A. VARSHA. "HIGH VOLTAGE DISTRIBUTION SYSTEMS-FOR BETTER VOLTAGE PROFILE." PROCEEDINGS OF INTERNATIONAL ACADEMIC CONFERENCE ON ELECTRICAL, ELECTRONICS AND COMPUTER ENGINEERING (IRAJ JOURNAL). 2013. VI. GURPREET KOUR AND R. K. SHARMA, DIFFERENT TECHNIQUES OF LOSS MINIMIZATION IN DISTRIBUTION SYSTEM, INTERNATIONAL JOURNAL OF ENHANCED RESEARCH IN SCIENCE TECHNOLOGY & ENGINEERING VOL. 2 ISSUE 2, FEB.-2013. @IJRTER-2018, All Rights Reserved 54