Code of practice for Distribution Lines and Transformer centre, types of transformer centres - Pole mounted, plinth mounted, indoor and outdoor types. Determining the rating of Distribution Transformer. Write Specifications of the Distribution Transformer. Draw the SLD of a Transformer centre indicating the size of protective devices, Prepare the schedule of equipments /Materials with specifications for a 11KV/415V,100 KVA transformer centre and their estimates, 415 V LT line materials and specifications , method of calculating various LT line materials (only). Prepare the schedule of materials (only) for 3 phase 4 wire LT line, 11 KV HT Line-materials and their specifications, method of calculating various HT line materials and tapping structure, TOPO sheet and its use, Concept of combined estimates. Prepare the schedule of materials (only) for 11 KV single circuit HT line for Rural Electrification. (Note: HT lines over head type only)

1. 1
Prepared By:
Mr.Premanand Desai L/EE
B.L.D.E.A’s SHREE SANGANABASAVA
MAHA SWAMIJI POLYTECHNIC,
VIJAYAPUR-03
E-mail ID:ssmp.premananddesai@bldea.org
cell no : +91 7892881829
COURSE & CODE: ELECTRICAL ESTIMATION AND COSTING (15EE54T)
UNIT - 05
DISTRIBUTION LINES AND TRANSFORMER CENTRE

2. 2
COURSE & CODE: ELECTRICAL ESTIMATION AND COSTING (15EE54T)
UNIT - 05
DISTRIBUTION LINES AND TRANSFORMER CENTRE
5.0 Distribution Lines : A distribution line is a line or system for distributing power from a
transmission system to a consumer points.
Example : L .T line – 440V (3-Ø) , 230V (1-Ø) – 4 Wire System
H.T. Line : 11 KV, 22KV, 33KV – 3 wire system
5.1 Code of practice for Distribution Lines (11KV).
1. While preparing route map or toposheet following should kept in mind.
a. To facilitate easy transportation, maintenance and repair 11KV line is to be taken
all along the road.
b. As for as possible too many deviations should be avoided such that lines to be drawn
in straight path.
c. 11KV lines are not be taken on the hills and low lying areas.
d. Pole Should not be located on rocks of either soft or hard.
2. Guarding are to be provided in case of road , railway line and telephone line crossing , river or
Valley crossing.
3. Every tapping point or a dead end and angle of deviation requires a stay or strut.
4. As per I.E rules No.77 & 80 minimum clearance to the ground must be provided.
5. The D.P (Double Pole) Structure must be provided for each KM run of the line where anchoring
can be done.
6. A tapping structure is to be provided for newline which will have G.O.S (Gang/Group Operating
System) for disconnecting line mechanically and D.O.L.O (Drop out lift off) cut-outs for protection
of line.
5.2 Transformer centre
Type : 1. Indoor type
2. Outdoor type – a. Pole Mounted substation.
b. Foundation Mounted substation.
1.Indoor type substations : In such substation the apparatus are installed within the substation
building such substations are usually for a voltage up to 11KV but can be erected for 33KV and 66 KV
when surrounding atmosphere is contaminated with impurities.
2.Outdoor type Substations :
a. Pole Mounted Substations : Such substation are erected for distribution of power in localities. Such
as single stout pole or H-Pole are employed for transformer of capacity up to 25KVA , 125KVA and
more than 250KVA 4 pole structure with suitable platform is used.
b. Foundation mounted substations : For transformer of capacity above 250KVA the transformers are
to be too heavy for pole mounting such substations are usually for voltages of 33KV and above
foundation mounted transformer station are used particularly in city area where space is not available
for fixing guy sets.

3. 3
5.3 Market Available - Specifications of the Distribution Transformer.
Output KVA : 25 , 50 , 63 , 100 , 200 , 250 , 300.
No. of Phase : Single or Three Phase.
Primary Voltages / Secondary Voltage: 11KV/430V , 22KV/11KV , 33KV/11KV ,110KV/11KV.
Connections : Delta-Star or Star-Delta.
Operating Frequency : 50Hz.
Type of Cooling : Oil immersed , Forced oil Cooled.
Type of Transformer : Core , Shell , Distribution.
5.4 Points to be considered to Determining the rating of Distribution Transformer.
1. Total Load to be Connected in Volt-Amperes.
2. Demand Factor :Maximum demand to the total connected load. It is always Less than one.
Demand factor of different loads or utilities
Sl. No Utility Demand Factor
1. Office , school 0.4
2. Hospital 0.5
3. Airports, Bank , Shop 0.6
4. Restaurant , Factory 0.7
5. Workshop, factory 24Hrs Shift 0.8
6. Arc Furnace 0.9
7. Compressor 0.5
8. Hand tools 0.4
9. Induction Furnace 0.8
3. Diversity factor : Sum of individual maximum demands of various sub circuits of a
system to the maximum demand of whole system.
Diversity factor =
𝐼𝑛𝑡𝑎𝑙𝑙𝑒𝑑 𝑙𝑜𝑎𝑑
𝑅𝑖𝑛𝑛𝑖𝑛𝑔 𝑙𝑜𝑎𝑑
>= 1.
5.5 Example on Transformer rating selection
Example 01 : Select a suitable Transformer for a industrial area. The Load conditions are as follows :
Available Voltage = 11KV, Required Voltage = 440/230 volts
Lighting Load = 10 KW, Industrial load = 50KW at 0.8 pf
Demand factor = 0.7 , Diversity factor = 1.46
Solution :
Total connected load = lighting load + Industrial load
=
10
1
+
50
0.8
= 10 + 62.5 = 72.5 KW
Maximum demand = Connected load × Demand factor
= 72.5 × 0.7 = 50.75 or Say 50 KVA
Required capacity of Transformer = Maximum / Diversity
= 50 /1.46 = 34.246 or say 34KVA
Allowance for Future expansion at 20% of required capacity.
=34 × 0.2 = 7 KVA
Hence capacity of the Transformer = 34+7 = 41 KVA
41 KVA , 11KV/440V , 3-Phase is not Available
Market Availability = 50KVA
Therefore A transformer of 50KVA , 11KV/440V , 3-Phase delta-star , 50Hz is Selected.

4. 4
5.6 S. L. D (Single Line Diagram) of a Transformer centre
On double pole structure transformer is to be mounted at a height of 3m from the
ground level. 11KV three lightening arresters at the top of the DP structures for the
protection of the transformer against lighting. Earth terminal of all the three
lightening arresters are joined together and connected to the earth provided for
lighting arresters.
11KV GOS is installed below the LA’s. The operating handle of the GOS is located on
one of the pole of the structure at a height of 1.25m from the ground level. By
operating this handle the transformer can be isolated from the 11KV supply whenever
necessary. The 11KV Horn Gap (HG) fuses are installed below the Group Operating
Switch (GOS) protects the transformer on the 11KV side. On the LT side of the
transformer four core LT cable is taken from LT bushing terminals to the LT
distribution box and from distribution box to outgoing LT feeders through PVC
conduit. This distribution box with fuse units provides isolation and protection of the
transformer against feeder faults. Anticlimbing devices, danger board, Spiral earth
electrodes are to be provided.

5. 5
5.7 Images of Transformer Centre

6. 6

7. 7
Example 02 : Prepare the schedule of equipment’s / Materials with specifications for a
11KV/415V, 100 KVA transformer centre. Also Prepare estimate of cost for the transformer
centre.
Sl.
No List of Materials with Specification
Quantity Required Rate /
Item
Amount
In `
Quantity Units
1. 8 Meter R.C.C Pole D.P Structure complete with Rails,
braces, Channels, nut bolt etc.,
01 Set 16,000=00 16,000=00
2. 100 KVA Distribution Transformer, 3-Phase , 50Hz,
11KV/440V with oil and Off load tap changer.
01 No. 1,50,000=00 1,50,000=00
3. Gang Operating Switch (G.O.S) 11KV class, 200Amps ,
Single Break.
01 Set 6,500=00 6,500=00
4. Drop Off Lift Out (D.O.L.O) cut-outs 01 Set 970=00 970=00
5. Horn gap Fuse unit 11KV Class 01 Set 2,150=00 2,150=00
6. L.T Distribution box 01 No. 1,500=00 1,500=00
7. 11 KV Pin insulator with pins and washers 03 No. 150=00 450=00
8. Disc insulator 11KV Class 45Kn 03 No. 300=00 900=00
9. 11KV Guy set complete 04 Sets 680=00 2,720=00
10. 40 mm dia. G.I Pipe, 3 mm thick 2.5 m long 12.5mm
holes drilled at 300mm distance with double mild steel
(M.S) bolt and nuts earthing sets.
04 Sets 1110=00 4,440=00
11. Lighting arrester 11KV class 03 Nos. 660=00 1,980=00
12. 95 sq.mm2
Aluminium PVC cable , 1.1KV grade for
incoming phase wires.
15 Meter 64=00 960=00
13. 70 sq.mm2
Aluminium PVC cable, 1.1KV grade for
incoming, neutral and outgoing Phase feeders.
53
Meter 55=00 2,915=00
14. 62.5mm PVC pipe 3mm thick 03 Meter 35=00 105=00
15. 62.5 mm PVC bends 3mm thick 04 Nos. 30=00 120=00
16. 50 mm PVC pipe 3mm thick 12 Meter 28=00 336=00
17. 50 mm PVC bends 3mm thick 08 Nos. 25=00 200=00
18. L.T protection Fuse Cut-outs. 01 set 1200=00 100=00
19. Anti-Climbing devices, Danger board, Bird Guard etc., Each one Set 900=00 900=00
20. Concreting material for guy sets 04 Nos 150=00 600=00
21. Miscellaneous Materials such as Nut bolts, Screws,
Charcoal, salts etc.,
Lumpsum 600=00 600=00
22. Transportation & Inspection Charges @5% -------- (1,80,046× 5%)
9,002=00
23. Labour Charge for fixing and erection of transformer
and other equipment’s. Lumpsum 9,323=00
24. Contingency @5% on above --------- 9,789=00
Grand Total ` 2,08,160=00
Total Estimate of cost is Rupees Two Lakh Eight Thousand one Hundred Sixty only.

8. 8
5.8 A.C.R.S conductor Table
For Example :
Squirrel (ACSR No.1) of 6/1/2.11mm
(6 Aluminium conductor and 1 Steel conductor of diameter 2.11mm)

9. 9
5.9 Images of Distribution line materials
R.C.C or P.C.C Pole 2- Pin Cross Arm 4- Pin Cross Arm
Guy Set Pin insulator
Strain insulators
A.C.S. R conductor Guarding wiring system Disc type Stain insulator
Danger board
Anti-Climbing device or wire
Double pole Structure
for Anchoring
V – Shaped Cross Arms Spiral Spring earthing Horn Gap (H.G) Fuse unit

10. 10
5.10 L .T lines (415V) - Materials with specifications.
L.T distribution system are of two types namely
1. Overhead distribution system.
2. Underground distribution system.
a. Pole :
Material used : Reinforced Cement Concrete (R.C.C) or Plain Cement Concrete (P.C.C).
Length of pole : 7.5 or 8 Meter.
Working load : 115 or 140 Kg
b. 2 Pin Cross Arm :
Name of the Material : M.S (Metal Sheet) angle of 510mm × 50m × 6 mm - Suitable for 1Ø
Line
c. 4 Pin Cross Arm :
Name of the Material : M.S (Metal Sheet) angle of 1200mm × 50m × 6 mm - Suitable for L.T
and H.T of 3-phase 4-wire lines.
d. Guy Sets :
Class : 1.1 KV
Stay wire used : 7 to 10 SWG standard stay wire wit Anchor and Anchor plate, 8 No. strain
insulator , 7/11 or 7/12 stay wire, stay clamp complete set.
e. Pin insulator:
Class : 1.1 KV
Material : porcelain
Size : 110mm dia, height 110mm with pin nut and washer.
f. Strain insulator :
Number : 8 No.
Voltage grade : 1.1 KV
g. Conductor :
Size : Squirrel (ACSR No. 1) of 6/1/2.11mm
(6 Aluminium conductor and 1 Steel conductor of diameter 2.11mm)
Weasel (ACSR No. 3) of 6/1/2.59 mm
L.T Line proposed route alignment of L.T line is to be done avoiding deviation as much as
possible in a suitable ground without hard rock.
The span of the line is usually 60 to 65 meter using 8 to 9 meter poles. At dead ends, deviations
and at anchoring points only R.C.C Poles are to be used and elsewhere PCC poles can be used.
Guys or Struts are to be provided for dead ends and also at deviation points to relieve the
strain. Anchoring (Breaking the line for stringing purpose) must be done for each 0.5KM by
providing double guy sets and having strain insulator on both sides of all the 4-wire.
Guarding’s are to be provided in case of crossing of the line with road , telephone line, railway
line , etc.,

11. 11
5.11 Method of calculating L.T line materials
1. No. of spans =
𝐿𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑙𝑖𝑛𝑒
𝑆𝑝𝑎𝑛
2. No. of Supports = No. of Spans + 1 (for tapping pole)
3. R.C.C Poles are used at starting , deviation points and anchoring points.
4. P.C.C poles are used at intermediate poles only.
5. No. of Crossarms
No. of 4-pin Crossarms = No. of Support + 1 (Tapping pole)
6. No. of pin insulators:
= 4 ((No. of Supports + No. of Deviations) – (one dead end + Anchoring point) )
7. No. of Strain insulators :
= 4 × (2(One for each Dead End) + 2(Number of anchorying points))
8. Length of the conductor required
(a) For Phase , A.C.S.R No.2 conductors are required = 3 × 1.03 = 3.09/KM.
(b) For Neutral , A.C.S.R No. 4 conductor is required = 1 × 1.03 = 1.03/KM.
9. The Number of guy sets = 2(One for each dead end) + 2(Anchorying point)+ Deviation
points.
10. Wherever guarding are to be provided two number of special cross arms with number of
guy sets and 15Kg, 8 S.W.G , G.I wire are to be used.

12. 12
Example 03 : Prepare the schedule of materials (only) for 3 phase 4 wire LT line
has to be extended for a length of 1 KM , for electrification of a factory. Assuming
an average span of 60 m.
Solution :
1. Number of span =
Length of line
span
=
1000
60
= 16.66 ≈ 17.
2. Total Number of supports = Number of span +1
= 17 + 1 =18Nos
3. Number of R.C.C poles
= One for tapping + One for Dead end + 1 (at 0.5KM anchoring)
= 1+1+1 = 03 Nos
4.Number of P.C.C poles = Number of Supports – R.C.C poles
= 18 – 3 = 15Nos.
5. Number of 4-pin Cross Arms = 18Nos.
6. Number of 1.1 KV class Guy sets
= 1 (Staring pole) + 1 (Terminating pole) + 02 (at 0.5 KM anchoring pole) = 04Sets
7. Number of pin insulator
= (Number of intermediate poles -2 (Staring pole + Terminating pole) ) × 4
= (18 - 2) × 4
= 16 × 4 = 64 Nos
8. Number of strain insulators
= 4 × (Starting pole + End pole + 2(Anchoring pole) )
= 4 (2+2) = 16 Nos.
9. Length of conductor
(a). A.C.S.R No. 2 weasel conductor for 3-Phase conductors with 3% sag
= 3 × 1KM × 1.03 = 3.09 KM
(b). A.C.S.R No. 4 Squirrel conductor for neutral with 3% sag
= 1 × 1KM × 1.03 = 1.03 KM
10. Miscellaneous materials such as Nuts, Bolts , Barbed wire , etc.,

13. 13
Example 04 : It is propose to supply power to an IP set of 5HP by extending overhead LT line
from distribution transformer centre for a distance of 300m. Prepare the schedule of
materials required for extension of LT line. Assume average span of 65 meters.
Solution :
Schedule of materials for L .T line extension
1.Number of Supports = Number of Span
Number of Span =
𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑖𝑛 𝑚
𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑠𝑝𝑎𝑛
=
300
65
= 4.6 ≈ 5 Nos.
2. Number of RCC pole for Dead end only = 01 No.
3. Number of PCC pole 5-1 = 04 Nos.
4. Number of 4 Pin Cross arms = 5+1 = 06 Nos.
5. Number of pin insulator = 4 × Number of PCC pole = 4 × 4 = 16 Nos.
6. Number of strain insulators = 2 (Staring & Dead End) × 4 = 8 Nos.
7. Length of A.C.S.R conductors allowing 3% sag
Distance × Number of Conductor × 1.03 sag = 0.3 × 4 × 1.03 = 1.236 Km
8. Number of Guy set for Staring & Dead End = 1+1 = 2 Set.
9. Miscellaneous Materials such as bolt, nuts , paint, sand , cement etc.,

14. 14
Example 05 : Prepare a list of materials with specification of L.T line to provide power supply
to a supply to a cluster of two number of I.P sets of 10 H.P each by extending overhead L.T
line for 500 Meter distance each from transformer centre.
Solution :
Schedule of materials for L .T line extension
1. Number of Span in each case =
𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑖𝑛 𝑚
𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑠𝑝𝑎𝑛
=
500
65
= 7.69 ≈ 8 Nos.
2. Number of Span = Number of Span × 2 = 8 × 2 =16 Nos.
3. Number of supports = 16 + 1 = 17 Nos.
4. Number of R.C.C poles = (1for tapping + 2 for dead ends ) = 03 Nos.
5. Number of PCC pole 17- 3 = 14 Nos.
4. Number of 4 Pin Cross arms = 18 Nos.
5. Number of pin insulator = 4 × Number of PCC pole = 4 × 14 = 56 Nos.
6. Number of strain insulators = 4 (2 Staring & 2 Dead End) × 4 = 16 Nos.
7. Length of A.C.S.R conductors allowing 3% sag
= Distance × Number of Conductor × 1.03 sag × Number of clusters
= 0.5 × 4 × 1.03 × 2 = 4.12 Km
8. Number of Guy set for 1- Staring & 2-Dead End =1+2 = 3 Sets.
9. Miscellaneous Materials such as bolt, nuts, paint, sand, cement etc.,

15. 15
5.11 Materials used in 11KV HT line

16. 16
5.12 Materials with specifications 11KV HT line
R.C.C Poles:
Materials : RCC
Length : 8,9,10,and 11m
Working load : 150 kg
Cement concrete of proportion : 1:2:3 with 10 to 12mm MS round rods
Cross section at top : 125 X 100mm, 125X105mm
Cross section at bottom : 210X140mm, 210X145mm
Cross arm :
Material : GI or MS
Type : V – type, Horizontal with or without single top support, pole
clamp, bolt Nuts, washers etc.
No. of pins : 2 pins, for V -type , 3 pins for Horizontal
Size : 50 X 50 X 6mm, angle shape
Length : 1.2m, 1m, 0.9m
Insulators:
Materials : Porcelain
Voltage grade : 11KV
Type : Pin insulators with pin, nut and washer
No. 15 Strain insulators or 11KV Disc insulators
Conductors:
Material : Al
Type : ACSR
Weasel conductor : 6/2/2.59mm, N0-2 ACSR Rabbit conductor : 6/1/3.55 mm,
A.C.S.R Coyote conductor : 26/2.54mm + 7/1.9 mm,
Gang operating Switch (G.O.S) :
Operating voltage : 11KV or 13.2KV
No. of Break : Single or Double
Current Rating : 200 or 400Amps
Operating handle with locking arrangement.
Spiral earth electrode :
Materials : 8 SWG G.I wire
Size : 150mm dia, 450mm long with 115 tuns.
Wound spirally from top of the pole to the ground and buried 1.5 m below the ground at bottom of
pole.
Anticlimbing devices :
Anticlimbing devices such as barbed wire are to be wound on all H.T pole above the height of 1.5m
so that ignored persons does not climb the pole and meet with accident.
Danger board or caution board :
Size of plate : 200mm×150mm × 1.6mm thick
Colour : Red letters in white back ground or white letters in red back ground.

17. 17
Earth guard stirrup (EGS) :
Material : M.S flat of size : 25m × 6mm , Length 2.74 m
Double inverted V Shaped flat forming a net of 8 SWG G.I wire for conductors. If the line snaps it will
hit earth GI wire and gets earthed.
Double pole structure :
Type of pole : P.C.C or R.C.C
Height of pole : 8 M or 9 M - with cross arms braces, clamps bolt , nuts with two number
of 8 Meter RCC pole a complete set.
Bird guards :
Material : MS sheet of 1.6mm thick
Size : saw type with suitable arrangement for fixing in to cross arms , etc.,
Primary cutout :
Type : Drop out lift off (D.O.L.O )
Material : Porcelain
Voltage rating : 8 , 11 and 15 KV class.
Lightening Arrestors :
Type : Electrolytic multigap , oxide film, Tyrite etc.,
Voltage rating : 6, 11, 13.2 KV etc.,
Enclosure materials : Porcelain with suitable top and bottom terminal for connection.

18. 18
5.13 Method of calculating various HT line materials.
1. No. of spans =
𝐿𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑙𝑖𝑛𝑒
𝑆𝑝𝑎𝑛
2. Total no. of 9m long R.C.C poles = No. of spans +1
3. Total No. of DP structures, R.C.C 9m long = 1 at Starting + 1 at deviating + 1
at ending + Assuming every 10th pole is to be an anchoring.
4. Total no. of 9m long SP structure = Total no. of poles – Total no. of DPstructures
5. No. of Cross arms ‘V’ Type with single top support or Horizontal 2 pin type with
single top supports = No. of SP structures
6. Insulators:
a. Pin type 1.1 KV class = (3 X No. of SP structures)+ (3 X No of deviations)+(3X No of
anchoring poles)
b. Strain insulators No.15 = 6 at starting + 6 at deviation + 6 at ending + 12 at
anchoring & Add 5% on total for breakage
7. No. of ordinary guy sets with break insulators = 1 at starting + 1 at ending + 2 at
deviation + 2 at anchoring.
8. Length of A.C.S.R conductor with 3% sag
= Length of proposed line X 3 conductors X 1.03
9. Concreting materials for pole bases = No of SP structures + (2 X No of DP structures)
10. Concreting materials for guy sets = No. of guy sets
11. No. of spiral earth electrodes = Total No of poles
12. No. of earth guard stirrups = No of SP structures
13. Consider if any guarding for the road & Telephone line crossing etc.
14. Miscellaneous materials such as danger boards, anti-climbing devices, pole
clamps, bolt nuts and other unfortunate items
5.14 Tapping structure:
When tapping proposed HT line from an existing HT line at appoint of support. The first pole
of the proposed line is called as tapping structure. It is DP structure with protective devices
like G.O.S, H.G fuses and D.O.L.O cut-outs are to be provided. Two guy sets are provided for
balance the DP structure and also provide spiral earth electrode.

19. 19
5.15 - Quantity of materials required for tapping structure:
1) 9m long RCC, DP structure = 1 set
2) No.15, 11KV class strain insulators = 6 Nos.
3) 11KV class GOS, 200A, single blade with operating handle = 1 set
4) Guy set with brake insulator = 2 sets
5) 11KV class pin insulators = 3 Nos.
6) Spiral earth electrode = 1 set
7) Anti climbing devices = 2 sets
8) Danger board = 1 No.
9) Concreting materials for pole bases = 2 sets
10) Concreting materials for guy sets = 2 sets
11) Miscellaneous materials such as pole clamps, bolt nuts and other unfortunate items
5.16 TOPO sheet and its use.
It is the sheet showing the plan of the area where the line is proposed to be drawn. Such sheet
is prepared after conducting the survey. The Toposheet represents the route of the proposed
line indicating the length, deviations, highway crossings, railway crossings, telephone line
crossings, river, water tank, stone quarry etc.
Hence Topo sheet provides detailed geographical picture for preparing the estimation of
cost for the proposed line.
For Example :

20. 20
5.17 Examples on H.T lines
Example : 06 - A Toposheet given below shows 15 km route of a proposed 11KV rural feeder
providing terminal structures, rural guards. Assuming average span length of 80m , Calculate
the materials required for the feeder.
Solution :
Assuming anchoring at 0.5 KM and D.P for each KM run
1) a) No. of spans between A &B =
𝐿𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑙𝑖𝑛𝑒
𝑆𝑝𝑎𝑛
=
7000
80
= 88 nos.
b) No. of spans between B &C =
𝐿𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑙𝑖𝑛𝑒
𝑆𝑝𝑎𝑛
=
4000
80
= 50 nos.
c) No. of spans between C &D =
𝐿𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑙𝑖𝑛𝑒
𝑆𝑝𝑎𝑛
=
4000
80
= 50 nos.
Total No. of spans = 88+50+50 = 188 Nos.
2) Total Number of supports = No. of spans + 1 = 188+1=189Nos.
3) Total Number of D.P structures, RCC 9m long
=
𝑁𝑜.𝑜𝑓 𝑆𝑢𝑝𝑝𝑜𝑟𝑡𝑠
10
=
189
10
= 18.9 ≈ 19 Nos. + 1 at Starting + 1 at deviating
= 19 + 1+(2x1) = 22 Sets
4) Total no. of 9m long SP structure, RCC 9m long
= Total no. of poles – Total no. of DP structures
= 189 – 22 = 167 Nos.
5) No. of V type Cross arms Horizontal type 2 pin type with single top supports
= No. of SP structures
= 167 Sets
6) Insulators:
a) Pin type 1.1 KV class
= (3 X No. of SP structures)+ (3 X (No of DP structures- 1 Dead end DP))
= (3 X 167) + (3 X (22 -1))
= 564 Nos
Add 5% on total for breakage i.e., Total No = 564 X 1.05 ≈ 592 Nos.
b) Strain insulators No.15
= 3 (1 (starting) +2 (anchoring ) + 2 (Intermediate DP) + 1 (Dead end DP)
= 3 (1 + (2×15) + (2×21) + 1 ) = 222 Nos.
Add 5% on total for breakage i.e., Total No = 222 X 1.05 ≈ 233 Nos

21. 21
7) No. of ordinary guy sets with break insulators
= 4 at Starting + (4 × Intermediate DP) + 2 at Dead end + 2 at guarding
= 4 + (4×21) + 2 + (2 X 3) = 96 Sets
8) Length of A.C.S.R conductor with 3% sag
= Length of proposed line X 3 conductors X 1.03
= 15 X 3 X 1.03
= 46.35 km
9) Concreting materials for pole bases = No. of SP structures + (2 X No. of DP structures)
= 167 + (2 X 22)
= 211 Sets
10) Concreting materials for guy sets = No. of guy sets = 96 Sets
11) No. of spiral earth electrodes = Total No. of supports = 189 Sets
12) No. of earth guard strirrups = No. of SP structures = 167 Sets
13) Number of G.O.S = 1 Set.
14) Primary cut-out D.O.L.O type 11KV class = 1 Set
15) Guarding for Railway crossing , Highway crossing, Telephone line crossing = 3 Set
(8 SWG G.I wire for guarding = 20 Kg / Guard) = 3 × 20 = 60 KG
16) Miscellaneous materials such as danger boards, anti-climbing devices, pole clamps, bolt
nuts and other unfortunate items.
Example : 07 – Prepare the Schedule of materials required for running a 11KV feeder for a
distance of 4km having a deviation at mid-point. Assuming a span of 0.04km. Specify all the
materials.
Solution :
1) a) No. of spans between A &B =
𝐿𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑙𝑖𝑛𝑒
𝑆𝑝𝑎𝑛
=
2000
40
= 50 nos.
b) No. of spans between B &C =
𝐿𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑙𝑖𝑛𝑒
𝑆𝑝𝑎𝑛
=
2000
40
= 50 nos.
Total No. of spans = 50+50 = 100 Nos.

22. 22
2) Total no. of Supports = No. of spans + 1 = 100+1=101Nos.
3) Total No. of DP structures, RCC 9m long = 1 at Starting + 1 at deviating + 1 at ending
= 1+1+1 = 3 Sets.
4) Total no. of 9m long RCC SP structure = Total no. of poles – Total no. of DP structures
= 101 – 3 = 98 Nos.
5) No of Cross arms V type 2 pin type with single top supports = No. of SP structures
= 98 Sets
6) Insulators:
a) Pin type 1.1 KV class = (3 X No. of SP structures)+ (3 X No of DP structures)
= (3 X 98) + (3 X 3)
= 303 Nos
Add 5% on total for breakage i.e., Total No = 303X 1.05 = 319 Nos.
b) Strain insulators No. 5 = 6 at starting + 12 at deviation + 6 at ending + 12 at anchoring
= 6+ (12 X 1) + 6 + (12 X 8)= 120 Nos.
Add 5% on total for breakage i.e., Total No = 120 X 1.05 = 126 Nos
7) No. of ordinary guy sets with break insulators
= 1 at starting + 1 at ending + 2 at deviation + 2 at Anchoring
= 1 + 1 + (2 X 1) + (2 X 8)
= 20Sets
8) Length of ACSR conductor with 3% sag = Length of proposed line X 3 conductors X 1.03
= 4 X 3 X 1.03 = 12.36 km
9) Concreting materials for pole bases = No of SP structures + (2 X No of DP structures)
= 98 + (2 X 3) = 104 Sets
10) Concreting materials for guy sets = No. of guy sets = 20 Sets
11) No. of spiral earth electrodes = Total No of poles = 101 Sets
12) No. of earth guard stirrups = No of SP structures = 98 Sets
13) No. of GOS or DOLO cutout 11KV class = 1 Set
14) Miscellaneous materials such as danger boards, anti-climbing devices, pole clamps, bolt
nuts and other unfortunate items

23. 23
Example : 08 - Prepare the schedule of materials required for erection for Extension of
11KV feeder line from Substation foe a distance of 8 Km. The line crosses highway and
telephone line in route and the line has two deviations. Assume average span of 80 meters
and every 10th pole to be anchored.
Solution :
1. No. of span =
𝐿𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑙𝑖𝑛𝑒
𝑆𝑝𝑎𝑛
=
8 ×1000
80
= 100 Nos.
No. of Supports = No. of Span + 1 = 100 +1 = 101Nos.
2. No. of Double Pole (D.P) =
𝑁𝑜.𝑜𝑓 𝑠𝑢𝑝𝑝𝑜𝑟𝑡
10
=
101
10
= 10.1 ≈ 10 Nos.
3. No. Of R.C.C pole = No. of supports – No. of D.P = 101 – 10 = 91 Nos.
4. No. of Cross arms with High Top support = No. of RCC pole + No. of deviation
= 91 + 2 = 93 set.
5. No. of pin insulators with pin = 3 × No. of RCC pole + 3 × (No. of DP – 1 Dead End DP)
= (3×91) +(3×9) = 300 Nos.
6. No. of Disc insulators = 3 for tapping pole + (6 × Intermediate DP ) + 3 for Dead end DP
= 3 + (6×8) + 3 = 54 Nos.
7. No. of Guy sets
= 4 for Tapping DP + (4× No. of Intermediate DP + 2 for dead end DP + (2× No. of guarding)
= 4 + (4×8) + 2 + (2×2)
= 42 Set.
8. Length of ACSR conductor allowing 3% sag
Distance in KM × No. of Conductor × 1.03 = 8 × 3 × 1.03 = 24.72 KM
9. No. of Spiral earth electrode = No. of Supports = 101 Nos.
10. No. of Earth guard Stirrups = No. of Single Pole (R.C.C) = 91 Set.
11. No. of Anti Climb Device = (1× Single Pole) + (2 × DP) = (1×91)+(2×10) = 111 Nos.
12. No. of danger boards = No. of Supports = 101 Nos.
13. No. of Cross arms for guarding = 2 × No. of Guarding = 2 × 2 = 4 Set
14. 8 SWG G.I wire for guarding = 20 Kg/Guard = 20 × 2 = 40 Kg
15. No. of G.O.S & D.O.L.O cut outs = 1 set
16. Miscellaneous materials , Such as bolt , Nut, paint, sand cement etc.

24. 24
5.18 Concept of Combined estimates:
It is the combination of more than one part of estimation is called combined estimation. It is
the estimation of different works like interior wiring and service connection or 11KV
distribution line and transformer centre with LT extension etc.
Example 01 :
A 11KV line is tapped and extended to a distance of 7km for a rural electrification.
Prepare the list of materials required for -
a) Tapping structure
b) Extending a 11KV line assuming a span of 85m
Solution:
a) Tapping structure :
1) 9m long RCC, DP structure = 1 set
2) No. – 15, 11KV class strain insulators = 6 Nos.
3) 11KV class GOS, 200A, single blade with operating handle = 1 set
4) Guy set with brake insulator = 2 sets
5) 11KV class pin insulators = 3 Nos.
6) Spiral earth electrode = 1 set
7) Anti climbing devices = 2 sets
8) Danger board = 1 No.
9) Concreting materials for pole bases = 2 sets
10) Concreting materials for guy sets = 2 sets
11) Miscellaneous materials such as pole clamps, bolt nuts and other unfortunate items.
b) Extending a 11KV line assuming a span of 85m
1) No. of spans between =
𝐿𝑒𝑛𝑔𝑡ℎ 𝑜𝑓 𝑙𝑖𝑛𝑒
𝑆𝑝𝑎𝑛
=
7000
85
= 82.35 nos.= 82 Nos.
2) Total No. of 9m long RCC poles = No. of spans = 82 Nos.
3) Total No. of D.P structures, RCC 9m long = 1 at ending = 1 Set
4) Total No. of 9m long SP structure
= Total no. of poles – Total no. of DP structures + 82-1 = 81 Nos.
5) No. of Cross arms V type 2 pin type with single top supports = No. of SP structures
= 81 Sets

25. 25
6) Insulators:
a) Pin type 1.1 KV class = (3 X No. of SP structures) + (3 X No of DP structures)
= (3 X 81) + (1 X 3) = 246 Nos.
Add 5% on total for breakage i.e., Total No = 246X 1.05 = 258 Nos.
b) Strain insulators No.15 = 3 at ending + 6 at anchoring
Assuming every 10th pole is to be an anchoring = 3 + (6 X 7) = 45 Nos.
Add 5% on total for breakage i.e., Total No = 45 X 1.05 = 47 Nos.
7) No. of ordinary guy sets with break insulators = 2 at ending + 2 at Anchoring
= 2 + (2 X 7)= 16 Sets.
8) Length of A.C.S.R conductor with 3% sag = Length of proposed line X 3 conductors X 1.03
= 7 X 3 X 1.03 = 21.63 km
9) Concreting materials for pole bases = No of SP structures + (2 X No of DP structures)
= 81+ (2 X 1) = 83 Sets.
10) Concreting materials for guy sets = No. of guy sets = 16 Sets
11) No. of spiral earth electrodes = Total No of poles = 82 Sets
12) No. of earth guard stirrups = No of SP structures = 81 Sets
13) No. of GOS or D.O.L.O cutout 11KV class = 1 Set
14) Miscellaneous materials such as danger boards, anti-climbing devices, pole clamps, bolt
nuts and other unfortunate items.