Presentation on theme: "Single Phase Transformers in H. V. Distribution Systems"— Presentation transcript:
1Single Phase Transformers in H. V. Distribution Systems
2Nature of Rural LoadsLoads in rural India are predominantly pumpsets used for lift irrigationThese loads have low p.f., low load factorLoad density is low due to dispersal of loadsExisting system is to lay 11 KV lines, employ 3 phase DTRs 11kv / 433 volts and lay long LT lines
3Nature of Rural Loads (Contd.) To fetch a load of one pump set of 5 HP (4 kw) ; two or three L.T. spans are to be laidOn each DTR 63 or 100 KVA 20 to 30 such pump sets are connected. If used for domestic services about 100 consumers can be connectedThey run for about 1500 Hrs in an year of 8760 hours.
4Disadvantages experienced with LVDS Poor tail end voltagesHigh quantum of lossesFrequent jumper cuts and fuse blow outsMotor burn outs almost twice in each cropping period of 100 daysDTR failures due to frequent faultsLoss of standing crops due to inordinate delays in replacement of failed DTRs
5Solution ? H V D S ?To improve quality of supply and reduce losses HVDS is recommended11 KV lines are extended to as nearer to the loads as possible and erect small size single phase transformers 5, 10 or 15 KVA and release supply with NO or least LT lineAim at “LT less” system starting from “Less LT”Unavoidable short LT lengths to be covered by insulated wires like ABC (Aerial Bunched Cables)
6Technical Superiority of HVDS For the distribution of same power, the comparison of voltage drop, losses etc., with 100 as base is illustrated belowParameterSingle Phase 6.3 kv / 433 V HVDSConventional 3 phase LVDSCurrent (A)11100Losses (kw)8.5Voltage drop12.7
7Technical Superiority of HVDS Smaller size conductors can be employedExcellent voltage profileReduced lossesNo frequent fuse blow outsNegligible transformer failuresTwo or three consumers get effected against 30 if DTR fails (even 100 domestic)Very easy and quick replacement
8HVDS – Single phase - Irrigation Good quality single phase motors are availableHigh yield of water as pump set efficiency is highSingle phase motors are ‘capacitor start’ and ‘capacitor run’Starters not requiredBuilt in capacitor
9Additional advantages of HVDS Unauthorised hooking of loads is not possible as LT lines are short and insulatedSystem power factor improves (0.95) causing easy reactive power controlAs only two or maximum (3) pump sets are connected on each DTR ; the consumers assume ownership and responsibilityHigh quality of power supply earns total consumer satisfaction
10Questions & Critical issues frequently faced on HVDS Whether HVDS is for future areas to be electrified or to convert existing LVDS?Can HVDS & LVDS coexist in the same area?What is the linkage between load density and type of Distribution SystemEconomics & payback periodPolicy on procurement of single phase transformers
11A&BH.V.D.S. to be implemented straight away where new villages are being electrified in view of its technical superiorityWhere 3 phase pump sets are in use HVDS can be implemented by converting existing LT lines for 11 KVEven three Nos. smaller size single phase transformers can be used for providing three phase LT supply capacity (3Xindividual capacity)
12A&B (Contd.)Single phase transformers 6.3 kv / 233 Volts can be manufactured with single or two bushingsThree single phase transformers can be connected with HVs in star or delta
14Comparison Star – Star Delta – Star Vector group connections outside Single HV bushingTwo 11 kv bushingsGraded insulation on HVEntire HV winding to be insulated for 11 kvCurrent rating is high and hence more copperCurrent in HV is less in delta and hence less copper
15(C) Linkage with current density In Metro areas with high load densities as high as 20 MW per sq km due to rise multistoried complexes enough load can be met with practically no LTIn smaller urban areas, single phase transformers can be employed selectively for single phase as well as three phase
16(C) Linkage with current density (Contd.) Even if one limb fails, single phase loads on that phase can be distributed on the other two and the failed unit can be replaced very quickly as it is easy to transport and erectIn the case of 3 phase large capacity transformers, entire unit is to be replaced and down time is high
17(C) Linkage with current density (Contd.) In rural areas of low load densities HVDS using one or three Nos. single phase transformers can be employed without any hesitationRural loads even village habitat portion are too low and mostly single phaseIn villages getting electrified afresh; the load densities are bound to be too low
18(D) EconomicsCost of three Nos. single phase transformers of capacity ‘K’ is equal to a three phase transformer of capacity (3K)Cost of employing three single phase transformers is 1.3 times the cost of a 3 phase transformerThere is no difference in no load losses and full load losses between one 3 phase transformer of 3 K and three Nos. single phase transformer of K
19(D) Economics (Contd.)However current for same capacity is too low at 11 KV compared to LTFor 100 KVA current is 5 Amps at 11 KV and 140 Amps at LTLine losses get reduced in the ratio 52:1402 (25:19600)Hence highly economical
20(E) Usage of three Nos. single phase against one three phase transformer in urban localities The schemes being implemented in many rural areas are mostly such as “Kutir Jyothi” and “A Lamp for each house” do not need high capacity transformers.There are single 5, 10, 15 / 16 capacity transformers also which can be used advantageously in these light load areas
21This has many advantages as follows (E) Usage of three Nos. single phase against one three phase transformer in urban localitiesThis has many advantages as followsCapacities of single phase units can be so selected to avoid laying LT lines as these units are available in ratings from 5 KVA to 15 KVASingle phase loads can be connected on individual single phase transformers duly dividing them.
22(E) Usage of three Nos. single phase against one three phase transformer in urban localities In respect of extremely few three phase loads with connected loads of 4 kw or above (very rare in rural areas) three single phase transformers of smaller capacities can be employed.The loads are too small that they cannot contribute to high unbalances.
23Transport, replacement is very easy and can be done much faster. (E) Usage of three Nos. single phase against one three phase transformer in urban localitiesIn the event of one phase unit giving trouble, the loads can be distributed on the other two phase units and the defective unit can be taken out easilyTransport, replacement is very easy and can be done much faster.In fact a rolling stock of 4% can be maintained at each distribution section office for faster replacement
24PROS & CONS in Restructuring existing LVDS to HVDS 99.99% customers avail supply at 415 / 240 Volts thus operational performance of LV network is key to customer servicesLosses in Indian Power System are around 20%. LV system is responsible for high loss scenario as LV line losses are 6 times of target limit and 3 times maximum tolerable limit. Switchover to HVDS alone can bring losses to international norms.
25PROS & CONS in Restructuring existing LVDS to HVDS Power loss for transmission of equal load in LVDS (415V) and HVDS (11000V) lines are in ratio 13:1Maximum permissible voltdrop between DSS and customer premises is 10%. Hence compliance with IE rule. 56 on voltage drop is difficult and very expensive in LVDS whereas it is simple in HVDS
26PROS & CONS in Restructuring existing LVDS to HVDS The investigation of typical LV feeders in LVDS indicate that 75% of LV feeders have voltdrop above 5% and is the cause of high losses whereas in HVDS losses on LV line are insignificant.The current for distribution of same power in L.V.D.S. is high and existing conductors get loaded beyond economic loading limits. It can be avoided by switch over to HVDS
27PROS & CONS in Restructuring existing LVDS to HVDS The monitoring of feeders in LVDS is difficult compared to HVDS as number of feeders to be monitored is in ratio of 60:1Unauthorised tapping of LV lines is simple and rampant in LVDS whereas it is very difficult in HVDSABC cables with tough insulation are indigenously available
28PROS & CONS in Restructuring existing LVDS to HVDS 3 Phase HVDSThe work involved in restructuring distribution work areConversion of existing low voltage lines to single phase 2 wire HV linesReplacement of existing three phase distribution transformers with small capacity single phase transformersUtilisation of existing three phase motors.
31Existing LT Distribution of KOTTUR - SS-I 39 Agl Services3.6 km LT Line
32Existing LT Distribution of Murakambattu - SS-II 24 Agl Services3.0 km LT Line
33Existing LT Distribution of Patnam – SS II 9 Agl Services1 no Poultry Service1.59 km LT Line
34Existing LT Distribution of Bangaru Palem – SS IV 38 Agl Services3.3 km LT Line
35Existing LT Distribution Network Present LT Distribution system consists of 3 phase distribution transformer with a capacity of 100 KVA in rural areas which feeds supply to all the consumers through 3 phase 4 wire LT network.DISADVANTAGES OF EXISTING SYSTEMLengthy LT Lines.Voltage drop at the consumer end.High I2R losses .Frequent motor burn-outs due to low voltage and consequent expenditure on repairs.Transformer failures-expenditure towards repairs and inconvenience to the consumers.Continue…
36Damage to standing crops, due to delay in replacement of failed distribution transformers. Fluctuations in voltages due to more number of consumers connected under this transformer (say 25 to 30 consumers).Nobody owns the transformer since everybody thinks that others will take care of the transformer.
37CALCULATION OF LT LINE LOSSES Electronic meters fixed on the LV Side of the distribution transformersAll Agricultural Services provided with electronic energy meters.Energy sent out from the transformer measured.During the same period energy consumed by the Agricultural consumers measured .Losses worked out.Continue…
38ORIGINAL 100 KVA DTR VOLTAGE &LINE LOSS COMPARISON Sl.NoParticularsKottur-ss IMurakkombattu –ss II1Crop patternSugarcane, paddyCoconut , mango garden, paddy and part of the land cultivated by sugarcane.2Length of LT lines3.6Km3.0 Km3No. of Pump sets39244Connected Loads179.5 HP130 HP5No. of days13 days14 days6Input4290 units3059 units7Outputunits2638 units8Loss of units799.6 units421 units9% of line loss18.63%13.76%
39ORIGINAL 100 KVA DTR VOLTAGE &LINE LOSS COMPARISON Sl.NoParticularsPatnam-ssBangarupalem –ss1Crop patternSugarcane-90% paddy &G.nutSugar cane,Paddy,Coconut,Mango Garden2Length of LT lines1.59Km3.3 Km3No. of Pump sets9384Connected Loads72.5 HP+2.25 KW130 HP5No. of days40 days19 days6Input17672 units6152 units7Output14700 units5149 units8Loss of units2972 units1003 units% of line loss16.82%16.30%
40As seen from the previous table results the LT line losses are more in LT distribution network. To overcome this,HVD 3Ph system is introduced by A.P.S.P.D.C.L to maintain better voltages and reliability of supply.
41Conversion of existing LT 3ph 4w Line into HT Line Same support with HVD SystemExisting LT 3Phase 4 wire line on support
42HVD SYSTEMOriginal 3ph 100KVA Dist.Transformer replaced with 11KV.CTPT set3ph 15KVA Dist.Transformer erected under HVDS to cater 2 to 3 services
43H.T. and L.T Layout of HVD System.KOTURU-SS-I 39 Agl Services3.6 km LT Line2.6 km converted to HT1.0 km LT Line11 Nos 15 kVA DTR’s
44H.T and L.T layout of HVD System Murakambattu SS I1 24 Agl Services3.0 km LT Line2.04 km converted to HT0.96 km LT Line10 Nos 15 kVA DTR’s
45H.T. and L.T Layout of HVD System.Patnam SS-II 9 Agl Services1.59 km LT Line1.59 km converted to HT8 Nos 15 kVA DTR’s
46H.T and L.T layout of HVD System Bangaru Palem SS IV 38 Agl Services3.3 km LT Line2.5 km converted to HT0.8 km LT Line9 Nos 15 kVA DTR’s
47HVD SYSTEM Existing LT Lines converted into HV Lines by replacing L T 3-Phase crossarm by 11KV . V crossarmReplacement of 3 number L T pininsulators with 3 number 11KV pin insulators.Replacement of 3 number LT shackles with 3 number 11KV strain insulators .Erection of additional supports where ever clearances are inadequate.Erection of smaller capacity 3 phase distribution transformer of 15 KVA capacity for every 2 to 3 pumpsets.Connection of existing pumpsets from the newly erected 15KVA distribution transformers with airbunched cable .
48Calculation Of HT Line Losses in HVD System 11 KV CT PT set erected in place of existing 100 KVA Distribution TransformerReadings taken simultaneously at CT PT set and at all pump sets.Losses worked out.Continue…
49No 15KVA distribution transformer erected 11 nos 10 nos Sl.NoParticularsKotturu SS-IMurakkambattu ss-II1)No 15KVA distribution transformer erected11 nos10 nos2)No of days15 days13 days3)INPUT5310 units3926 units4)OUTPUTunitsunits5)Losses290.8 units213.8 unitsContinue…
50Sl.No Particulars Kotturu ss-I Murakambattu ss-II 6) % of line losses on HVDS5.47%5.44%7)% of line loss on earlier LT Distribution System18.63%13.76%8)% Net reduction in line losses13.16%8.32%
51No 15KVA distribution transformer erected 8 nos 9 nos Sl.NoParticularsPatnam SS-IIBangarupalem ss-II1)No 15KVA distribution transformer erected8 nos9 nos2)INPUT1299 units334 units3)OUTPUT1229 units321.4 units4)Loss of units69.7 units12.6 unitsContinue…
52Sl.No Particulars Patnam ss-II Bangarupalem ss-II 5) % of line losses on HVDS5.30%3.77%6)% of line loss on earlier LT Distribution System16.82%16.30%7)% Net reduction in line losses11.52%12.53%
53Comparison between LT System with HVD System KOTTURU SS-IParticularsLTHVDSLength of HT lines-2.6KmLength of LT lines3.6 Km1 KmNo of Distribution transformers100 KVA –1 no/..15KVA- 11 no/..Voltage at tail end350 volts420 volts% line losses18.63%5.47%
54Tail end Voltage in LT System Tail end Voltage in HVD System
56MURAKAMBATTU SS-II 100 KVA ParticularsLTHVDSLength of HT lines-2.04KmLength of LT lines3.6 Km0.96 KmNo of Distribution transformers100 KVA –1 no/..15KVA- 10 no/..Voltage at tail end385 volts430 volts% line losses13.76%5.44%
57Tail end Voltage in LT System Tail end Voltage in HVD System
59PATNAM SS-II 63 KVAParticularsLTHVDSLength of HT lines-1.59 KmLength of LT linesNo of Distribution transformers63 KVA –1 no/..15KVA- 8 no/..Voltage at tail end340 volts420 volts% line losses16.82 %5.30%
62NEW VERSION OF HVDS SYSTEM Bangaru Palem SS-IV 100 KVA The New version of HVDS system is an extension of HVDS work executed at previous locations.The H.T line losses in previous systems is 5.3%. An effort has been done to further reduce the H.T line losses by adopting following methods.1. Reinforcement of existing LT net work of 7/2.59 ACSR conductor with 55 sqmm conductor.2.Providing of required rated capacitors at each agricultural services.
63Bangaru Palem SS-IV 100 KVA with reinforcement of conductor and installing rated capacitors. ParticularsLTHVDSLength of HT lines-2.5 KmLength of LT lines3.3 Km0.8 KmNo of Distribution transformers100 KVA –1 no/..15KVA- 9 no/..Voltage at tail end320 volts430 volts% line losses16.30 %3.77%
64Bangaru Palem SS-IV 100 KVA. Comparison between HVDS with existing conductor and HVDS with reinforcement of conductor and installing rated capacitorsParticularsHVDS with existing conductorHVDS with Reinforcement of conductor and rated capacitorsVoltage at tail end420 volts430 volts% line losses5.31 %3.77%
65Tail end Voltage in LT System Tail end Voltage in HVD SystemTail end Voltage in LT System
67ADVANTAGES OF HVD SYSTEM The registered customers will feel ownership and take responsibility and not allow others to meddle with the L.T. Network.Prevention of unauthorized loads by the consumers themselves since the distribution transformer may fail if loaded beyond its capacity.Failure will be minimal because of no over loading and no meddling of L.T Lines.In the event of equipment failure only 2 or 3 customers will get affected instead of 25 to 30 customers in original system.High quality of supply since there is practically no voltage drop.Less burnouts of motors because of good voltage and less fluctuations.Continue…
68Considerable reduction in line losses and consequent savings in power purchase cost Since Losses are reduced considerably ,Power can be supplied to additional loads without any further investment on infrastructure.No additional generation capacity needed for giving new loads due to reduction in power drawals.Accidents due to touching of snapped conductors reduced due to the fact that the breaker trips at substation since the line is at 11 KV potential.
69Interaction with the consumers by CMD/APSPDCL& JMD (vigilance)A. P Interaction with the consumers by CMD/APSPDCL& JMD (vigilance)A.P. Transco on at Doddipalle
71Interaction with the consumers by CMD/APSPDCL& JMD (vigilance)A. P Interaction with the consumers by CMD/APSPDCL& JMD (vigilance)A.P.Transco on at Murakambattu SSIIConsumers opined that…The motors are drawing less current and hence life span of motor has increased.The rate of motor burnouts are also reduced.The motors running smoothly without hissing noise.The transformer failures are almost avoided.Theft of energy eliminated since the consumers will not allow others to pilfer from their Distribution Transformer.Interruptions have been minimized and quality of supply assured.Due to reliability of supply ,2 crops can be raised and can increase the productivity.