Transcript Document

Single Phase Transformers
in
H. V. Distribution Systems
1
Nature of Rural Loads
• Loads in rural India are predominantly
pumpsets used for lift irrigation
• These loads have low p.f., low load
factor
• Load density is low due to dispersal of
loads
• Existing system is to lay 11 KV lines,
employ 3 phase DTRs 11kv / 433 volts
and lay long LT lines
2
Nature 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 laid
• On each DTR 63 or 100 KVA 20 to 30
such pump sets are connected. If used
for domestic services about 100
consumers can be connected
• They run for about 1500 Hrs in an year
of 8760 hours.
3
Disadvantages experienced with LVDS
• Poor tail end voltages
• High quantum of losses
• Frequent jumper cuts and fuse blow outs
• Motor burn outs almost twice in each cropping
period of 100 days
• DTR failures due to frequent faults
• Loss of standing crops due to inordinate
delays in replacement of failed DTRs
4
Solution ? H V D S ?
To improve quality of supply and reduce
losses HVDS is recommended
• 11 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 line
• Aim at “LT less” system starting from “Less
LT”
• Unavoidable short LT lengths to be covered
by insulated wires like ABC (Aerial Bunched
Cables)
5
Technical Superiority of HVDS
• For the distribution of same power, the
comparison of voltage drop, losses etc., with
100 as base is illustrated below
Parameter
Single Phase 6.3
kv / 433 V HVDS
Conventional 3
phase LVDS
Current (A)
11
100
Losses (kw)
8.5
100
Voltage drop
12.7
100
6
Technical Superiority of HVDS
• Smaller size conductors can be employed
• Excellent voltage profile
• Reduced losses
• No frequent fuse blow outs
• Negligible transformer failures
• Two or three consumers get effected against
30 if DTR fails (even 100 domestic)
• Very easy and quick replacement
7
HVDS – Single phase - Irrigation
• Good quality single phase motors are
available
• High yield of water
efficiency is high
as
• Single phase motors are
start’ and ‘capacitor run’
pump
set
‘capacitor
• Starters not required
• Built in capacitor
8
Additional advantages of HVDS
• Unauthorised hooking of loads is not possible as
LT lines are short and insulated
• System power factor improves (0.95) causing
easy reactive power control
• As only two or maximum (3) pump sets are
connected on each DTR ; the consumers assume
ownership and responsibility
• High quality of power
consumer satisfaction
supply
earns
total
9
Questions & Critical issues
frequently faced on HVDS
A. Whether HVDS is for future areas to be
electrified or to convert existing LVDS?
B. Can HVDS & LVDS coexist in the same area?
C. What is the linkage between load density and
type of Distribution System
D. Economics & payback period
E. Policy on procurement
transformers
of
single
phase
10
A&B
• H.V.D.S. to be implemented straight away
where new villages are being electrified in
view of its technical superiority
• Where 3 phase pump sets are in use HVDS can
be implemented by converting existing LT
lines for 11 KV
• Even three Nos. smaller size single phase
transformers can be used for providing three
phase LT supply capacity (3Xindividual
capacity)
11
A&B
(Contd.)
• Single phase transformers 6.3 kv / 233
Volts can be manufactured with single
or two bushings
• Three single phase transformers can be
connected with HVs in star or delta
12
Star – Star Vs. Delta - Star
n
n
N
A
a
B
b
C
c
A
B
a
C
b
c
13
Comparison
Star – Star
Delta – Star
Vector group connections Vector group connections
outside
outside
Single HV bushing
Two 11 kv bushings
Graded insulation on HV
Entire HV winding to be
insulated for 11 kv
Current rating is high and Current in HV is less in
hence more copper
delta and hence less
copper
14
(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 LT
• In smaller urban areas, single phase
transformers can be employed selectively
for single phase as well as three phase
15
(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 erect
• In the case of 3 phase large capacity
transformers, entire unit is to be
replaced and down time is high
16
(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 hesitation
• Rural loads even village habitat portion
are too low and mostly single phase
• In villages getting electrified afresh;
the load densities are bound to be too
low
17
(D) Economics
• Cost
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 transformer
• There 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
18
(D) Economics
(Contd.)
• However current for same capacity is
too low at 11 KV compared to LT
• For 100 KVA current is 5 Amps at 11 KV
and 140 Amps at LT
• Line losses get reduced in the ratio
52:1402 (25:19600)
• Hence highly economical
19
(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
20
(E) Usage of three Nos. single phase against one
three phase transformer in urban localities
• This has many advantages as follows
• Capacities 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 KVA
• Single phase loads can be connected on
individual single phase transformers duly
dividing them.
21
(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.
22
(E) Usage of three Nos. single phase against one
three phase transformer in urban localities
• In 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 easily
• Transport, 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
23
PROS & 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 services
• Losses 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.
24
PROS & CONS in Restructuring existing
LVDS to HVDS
• Power loss for transmission of equal load
in LVDS (415V) and HVDS (11000V) lines
are in ratio 13:1
• Maximum 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
25
PROS & 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
26
PROS & 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 60:1
• Unauthorised tapping of LV lines is simple
and rampant in LVDS whereas it is very
difficult in HVDS
• ABC cables with tough
indigenously available
insulation
are
27
PROS & CONS in Restructuring existing
LVDS to HVDS
3 Phase HVDS
The work involved in restructuring
distribution work are
• Conversion of existing low voltage lines to
single phase 2 wire HV lines
• Replacement of existing three phase
distribution
transformers
with
small
capacity single phase transformers
• Utilisation of existing three phase motors.
28
HIGH VOLTAGE DISTRIBUTION SYSTEM
IN
APSPDCL
29
30
Existing LT Distribution of KOTTUR - SS-I
39 Agl Services
3.6 km LT Line
31
Existing LT Distribution of Murakambattu - SS-II
24 Agl Services
3.0 km LT Line
32
Existing LT Distribution of Patnam – SS II
9 Agl Services
1 no Poultry Service
1.59 km LT Line
33
Existing LT Distribution of Bangaru Palem – SS IV
38 Agl Services
3.3 km LT Line
34
Existing 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 SYSTEM
•Lengthy 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.
35
Continue…
•Damage 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.
36
CALCULATION OF LT LINE LOSSES
•Electronic meters fixed on the LV Side of the
distribution transformers
•All 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…
37
ORIGINAL 100 KVA DTR VOLTAGE &LINE LOSS COMPARISON
Sl.No Particulars
Kottur-ss I
Murakkombattu –ss II
1
Crop pattern
Sugarcane,
paddy
Coconut , mango garden, paddy and part
of the land cultivated by sugarcane.
2
Length of LT
lines
3.6Km
3.0 Km
3
No. of Pump sets
39
24
4
Connected Loads
179.5 HP
130 HP
5
No. of days
13 days
14 days
6
Input
4290 units
3059 units
7
Output
3490.4 units
2638 units
8
Loss of units
799.6 units
421 units
9
% of line loss
18.63%
13.76%
38
ORIGINAL 100 KVA DTR VOLTAGE &LINE LOSS COMPARISON
Sl.No Particulars
Patnam-ss
Bangarupalem –ss
1
Crop pattern
Sugarcane90% paddy
&G.nut
Sugar cane,Paddy,Coconut,Mango
Garden
2
Length of LT
lines
1.59Km
3.3 Km
3
No. of Pump sets
9
38
4
Connected Loads
72.5 HP+2.25
KW
130 HP
5
No. of days
40 days
19 days
6
Input
17672 units
6152 units
7
Output
14700 units
5149 units
8
Loss of units
2972 units
1003 units
9
% of line loss
16.82%
16.30%
39
As 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.
40
Conversion of existing LT 3ph 4w Line into HT Line
Existing LT 3Phase 4 wire line
on support
Same support with HVD System
41
HVD SYSTEM
Original 3ph 100KVA Dist.Transformer replaced
with 11KV.CTPT set
3ph 15KVA Dist.Transformer erected
under HVDS to cater 2 to 3 services
42
H.T. and L.T Layout of HVD System.KOTURU-SS-I
39 Agl Services
3.6 km LT Line
2.6 km converted to HT
1.0 km LT Line
11 Nos 15 kVA DTR’s
43
H.T and L.T layout of HVD System Murakambattu SS I1
24 Agl Services
3.0 km LT Line
2.04 km converted to HT
0.96 km LT Line
10 Nos 15 kVA DTR’s
44
H.T. and L.T Layout of HVD System.Patnam SS-II
9 Agl Services
1.59 km LT Line
1.59 km converted to HT
8 Nos 15 kVA DTR’s
45
H.T and L.T layout of HVD System Bangaru Palem SS IV
38 Agl Services
3.3 km LT Line
2.5 km converted to HT
0.8 km LT Line
9 Nos 15 kVA DTR’s
46
HVD SYSTEM
Existing LT Lines converted into HV Lines by replacing
•L T 3-Phase crossarm by 11KV . V crossarm
•Replacement 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 .
47
Calculation Of HT Line Losses in HVD System
• 11 KV CT PT set erected in place of existing 100
KVA Distribution Transformer
•Readings taken simultaneously at CT PT set and at
all pump sets.
•Losses worked out.
Continue…
48
Sl.No
Particulars
Kotturu SS-I
Murakkambattu ss-II
1)
No 15KVA distribution
transformer erected
11 nos
10 nos
2)
No of days
15 days
13 days
3)
INPUT
5310 units
3926 units
4)
OUTPUT
5019.2 units
3712.2 units
5)
Losses
290.8 units
213.8 units
49
Continue…
Sl.No
Particulars
Kotturu ss-I
Murakambatt
u ss-II
6)
% of line losses 5.47%
on HVDS
5.44%
7)
% of line loss
on earlier LT
Distribution
System
18.63%
13.76%
8)
% Net
reduction in
line losses
13.16%
8.32%
50
Sl.No
Particulars
Patnam SS-II
Bangarupalem ss-II
1)
No 15KVA distribution
transformer erected
8 nos
9 nos
2)
INPUT
1299 units
334 units
3)
OUTPUT
1229 units
321.4 units
4)
Loss of units
69.7 units
12.6 units
51
Continue…
Sl.No
Particulars
Patnam ss-II
Bangarupalem
ss-II
5)
% of line losses on 5.30%
HVDS
3.77%
6)
% of line loss on
earlier LT
Distribution
System
16.82%
16.30%
7)
% Net reduction
in line losses
11.52%
12.53%
52
Comparison between LT System with HVD System
KOTTURU SS-I
Particulars
LT
HVDS
Length of HT
lines
-
2.6Km
Length of LT
lines
3.6 Km
1 Km
No of Distribution
100 KVA –1 no/..
transformers
15KVA- 11 no/..
Voltage at tail end
350 volts
420 volts
% line losses
18.63%
5.47%
53
Voltage at tail end
Voltage at tail end
440
420
420
400
380
360
350
340
320
300
Series1
Series2
Tail end Voltage in LT System
Tail end Voltage in HVD System
54
% Line losses
20.00%
18.63%
18.00%
% Line losses
16.00%
14.00%
12.00%
10.00%
8.00%
6.00%
5.47
4.00%
2.00%
0.00%
% line losses
% Line losses before
HVD System
% Line losses after HVD System
55
MURAKAMBATTU SS-II 100 KVA
Particulars
LT
HVDS
Length of HT
lines
-
2.04Km
Length of LT
lines
3.6 Km
0.96 Km
No of Distribution
100 KVA –1 no/..
transformers
15KVA- 10 no/..
Voltage at tail end
385 volts
430 volts
% line losses
13.76%
5.44%
56
Murakambattu SS II 100 KVA
Voltage at tail end
440
430
430
420
410
400
390
380
370
360
375
350
340
Voltage
Series1
at tail end
Series2
Tail end Voltage in LT System
Tail end Voltage in HVD System
57
% Line losses
Murakambattu SS II 100 KVA
16.00%
14.00%
12.00%
10.00%
8.00%
6.00%
4.00%
2.00%
13.76%
5.44%
0.00%
% line losses
58
PATNAM SS-II 63 KVA
Particulars
LT
HVDS
Length of HT
lines
-
1.59 Km
Length of LT
lines
1.59 Km
-
No of Distribution
63 KVA –1 no/..
transformers
15KVA- 8 no/..
Voltage at tail end
340 volts
420 volts
% line losses
16.82 %
5.30%
59
Patnam SS II 63 KVA
440
420
Voltage at tail end
430
420
410
400
390
380
340
370
360
350
340
Voltage
Series1
at tail end
Series2
Tail end Voltage in LT System
60
Patnam SS II 63 KVA
16.00%
16.82%
% Line losses
14.00%
12.00%
10.00%
8.00%
5.3%
6.00%
4.00%
2.00%
0.00%
% line losses
61
NEW 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.
62
Bangaru Palem SS-IV 100 KVA with reinforcement of
conductor and installing rated capacitors.
Particulars
LT
HVDS
Length of HT
lines
-
2.5 Km
Length of LT
lines
3.3 Km
0.8 Km
No of Distribution
100 KVA –1 no/..
transformers
15KVA- 9 no/..
Voltage at tail end
320 volts
430 volts
% line losses
16.30 %
3.77%
63
Bangaru Palem SS-IV 100 KVA.
Comparison between HVDS with existing conductor
and HVDS with reinforcement of conductor and
installing rated capacitors
HVDS with
existing
conductor
HVDS with
Reinforcement of
conductor and rated
capacitors
Voltage at tail
end
420 volts
430 volts
% line losses
5.31 %
3.77%
Particulars
64
Bangaru Palem SS IV 100 KVA
Voltage at tail end
440
430
430
420
410
400
390
380
370
360
320
350
340
Voltage
Series1
at tail end
Series2
Tail end Voltage in HVD System
Tail end Voltage in LT System
65
Bangaru Palem SS IV 100 KVA
16.00%
% Line losses
14.00%
16.30%
12.00%
10.00%
8.00%
3.77%
6.00%
4.00%
2.00%
0.00%
% line losses
66
ADVANTAGES 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…
67
Considerable 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.
68
Interaction with the consumers by CMD/APSPDCL& JMD
(vigilance)A.P. Transco on 01.10.2002 at Doddipalle
69
70
Interaction with the consumers by CMD/APSPDCL& JMD
(vigilance)A.P.Transco on 01.10.2002 at Murakambattu SSII
Consumers 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.
71
72