Code of practice for Transmission lines and substations, transmission line materials and their specifications, types of Towers, ACSR conductors and Number of Disc insulators in suspension string, strain string, span and height of towers for 66 KV, 110 KV, 220 KV transmission lines, concept of single circuit and double circuit transmission lines, method of calculating the Quantity of transmission line materials, Prepare the schedule of materials (only) for 66 KV,110 KV and 220 KV single circuit transmission lines. 66KV/11KV, 5 MVA Substations- Single Line diagram, list of Electrical equipment's/ materials (only) and their specifications.

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 - 06
TRANSMISSION LINES AND SUBSTATIONS

2. 2
COURSE & CODE: ELECTRICAL ESTIMATION AND COSTING (15EE54T)
UNIT - 06
TRANSMISSION LINES AND SUBSTATIONS
6.0 Transmission line:
The line bringing electrical supply from generating stations to secondary substations is called
transmission lines.
Examples - 400KV, 220KV, 110KV, 66KV, etc.
6.1 Code of practice for Transmission lines:
1) Preliminary surveying is carried out with respect to the following aspects to plot the toposheet.
i) The transmission line is to be taken along the road as far as possible to facilitate easy
transportation, maintenance and repair.
ii) Transmission lines are not to be taken on hill top to avoiding lightning effect.
iii) Lines to be drawn in straight path as far as possible to avoid excess of materials.
2) Minimum clearance (6.096 Meter) from conductor to ground must be kept according to IE rules.
3) Double insulator strings and guarding are to be provided in case of road crossing crossings,
railway, telephone line, highway, canal and river crossings, etc.
4) Conductor should be having high tensile strength in order to withstand mechanical load.
5) Towers should be having high mechanical strength to withstand the weight of the conductor,
insulators and high velocity wind load.
6) Continuous wire should be run on top of the towers for earthing in order to protect the
transmission line against the lightning discharge.
7) Phase plates, number plates, anti-climbing devices and danger boards should be provided for
each tower.
6.2 Images of Transmission line materials
Armoring rods Vibration dampers
Phase Plate Jumpers Parallel groove clamps
Suspension clamps Tension clamps Anti-climbing devices Arching horns

3. 3
6.3 Transmission line materials
1. Towers : Lattice steel or painted or galvanised steel materials used for fabrication of towers. The
height of the line voltage length of the span and legs of the towers are set in special concrete
foundations.
Mainly there are two types of towers - 1.Tangent , 2.Anchor Towers.
1.Tangent Towers (suspension towers) :
These are straight line towers and are called as A type towers or suspension towers. The angle
of deviation is zero degree. They are withstanding vertical load.
2.Anchoring towers:
These are the deviation towers, starting or dead end towers. They are also called as B, C and
D type towers. Which are installed at an angle of deviation from 0 to 30 degree, 30 to 60
degree and 60 to below 90 degree respectively. These towers are withstanding the horizontal
load. Four pole structures are used at an angle exactly 90 degree deviation.
Extension Piece : Extension piece of fabricated steel structure of 3 meter or 6 meter may be used in
order to achieve the minimum clearance to ground as per I.E. rule.
Span Length:
1. 66KV line – 220m to 260m
2. 110KV line – 260m to 330m
3. 220KV line – 330m to 360m
Approximate height and weight of towers:
Sl.No. Line
Voltage
Height in
meters
Weight in Tons
Tangent Tower Anchor Tower
1 66KV 24 2 tons 3 tons
2 110KV 24 3.5 tons 4.5 tons
3 220KV 26 4 tons 5 tons
No. of 15KV disc insulators and their breaking strength:
Sl.No. Line
Voltage
No. of 15KV disc insulators Breaking
strength
Tangent Tower Anchor Tower
1 66KV 4Nos. 5 Nos. 70 KN
2 110KV 7Nos. 8 Nos. 90 KN
3 220KV 14Nos. 15 Nos. 120 KN
2. Types of conductor and their size:
Sl. No. Type of conductor size Application
1 Coyote Conductor 26/2.54mm + 7/1.9mm 66KV Line
2 Lynx Conductor 30/7/2.79mm 110KV Line
3 Drake Conductor 30/7/4.27mm 220KV Line
3. Armouring rods:
They consist of aluminium round rods of short length. These are wrapped around A.C.S.R conductors
at the point of support. It protects the A.C.S.R conductors from possible damage from vibration of
conductors due to high velocity wind action and tightening the clamps at the point of support.
4. Vibration dampers:
These are used to prevent occurrence of resonant vibration due to high velocity wind action.
Occasionally it has been found resulting in breaking of conductor strands at the point of support.

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5.Arching horns:
These are placed near the ends of the insulator strings and connected to earth. This regulates the
potential gradient across the strings and takes care of the arc of the flash over. These are provided for
protection of insulators.
6. Numbering plates:
All the towers are fixed with number plate to find out the faulted place(distance) by means of
toposheet.
7. Phase plates:
These are fixed to each tower for indication the red yellow and blue phases.
8. Bolt and Nuts:
Standard bolt and nuts are used, common in size from 25mm to 225mm length and 16mm thickness.
9. Bird guards:
To avoid sitting of birds on supports, a stick of ebonite plate with zig zag cutting on top. It is fixed near
the insulator on the cross arms to prevent flash over between cross arm and conductor.
10.Parallel groove clamps:
These clamps are used for electrical connections between two conductors.
11. Suspension clamps:
These are used with arcing horns for holding insulator discs for suspension type or A type Towers.
12. Tension clamps:
These are provided with all types of anchoring towers (B,C and D type) to hold the group of disc
insulators with arching horns.
13. Danger boards:
A danger plate is provided for each tower as a warning measure indicating the working voltage, the
word DANGER and also bone and skull symbols. It is provided at a height of 3m from the ground level.
14. Anti-climbing devices:
GI Barbed wire is wrapped around the tower legs at a height of 2.5m from the ground level for at least
1m length. This is to prevent climbing of unauthorized persons.
15. Other accessories:
Such as Al paint, twisting joints, tubular compression joints, repair sleeves, etc.

5. 5
6.4 Single circuit and double circuit transmission lines.
In single circuit transmission line three conductors corresponding to three phases i.e., R Y B phases
are run on the transmission towers.
Where as in double circuit transmission line total six conductors are provided to make two different
transmission circuits. Each circuit consisting of three conductors corresponding to three phases. This
method of transmission enables the transfer of more power over a particular distance. It is cheaper
and requires less conductor materials less land.
Suspension type insulators Strain string insulators

6. 6
6.5 Method of calculating the quantity of transmission line materials:
1. Number of spans =
length of proposed line in meters
span length in meters
2. Total number of four legged fabricated steel structures = No. of spans +1
3. Number of anchoring towers=
Total number of towers
10
(assuming every 10th
tower is to be an anchoring)
4. Number of suspension towers = Total number of towers – Number of anchoring towers
5.Total weight of the towers= ( Total no. of suspension towers X weight of each
suspension towers) + ( Total no. of anchoring towers X weight of each anchoring towers)
6. Number of 15KV disc insulators
i. At suspension string for tangent towers
= Number of suspension towers X No of suspension strings/ tower X No of insulator/ suspension
string.
ii. At tension string for anchoring towers
= Number of anchoring towers X Number of tension strings/ tower X No of insulator / tension
string.
Total no. of disc insulators = (i+ii)
Add 5% breakage on total
7. Length of ACSR conductor allowing 3% sag = (total length of the line X No.of conductor) X 1.03
8. Length of the GI ground wire of size 7/3.15mm allowing 3% sag
= ( Total length of the line X no of ground wire) X 1.03
9. No. of suspension clamps for suitable conductor with arcing horns
= Total no of towers × No. of suspension strings/tower.
10. No of tension clamps for suitable conductor with arcing horns
= Total no of anchoring towers X No of tension strings/tower.
11. Armouring rods for suitable conductor = No of suspension clamps + No of tension clamps
12. PG clamps for suitable conductor
= No of anchoring towers X No of jumpers / tower X No of PG clamps / jumpers
13. Vibration dampers for suitable conductor = Total no of towers x 6 ( for single circuit)
14. Grounding materials including accessories = Total no of towers
15. Cement concrete for tower erection = Total no of towers X 12m3
16. Miscellaneous materials such as conductor accessories, ant climbing devices, danger
boards, phase plates, no. plates, bird guards, bolt nuts, and other unfortunate items.

7. 7
6.6 Examples :
1. Prepare the quantity of materials required for running a 80km long 66kv single circuit
transmission line across a jungle terrain using four legged fabricated steel structures weighing
approximately 2 tones. Assume a span length of 300m. The conductor used is coyote ACSR.
Solution:
a) No. of spans =
length of proposed line in meters
span length in meters
=
80000
300
= 266.66 = 267 Nos.
b) Total no. of four legged fabricated steel structures = No. of spans +1
= 267+1=268 nos.
c) No. of anchoring towers, Assuming every 10th tower is to anchoring
=
Total No.of Towers
10
=
268
10
= 26.8 = 27 Nos.
Total No. of anchoring towers =27+1 at starting point = 28 nos.
d) No. of suspension towers = Total no. of towers – No. of anchoring towers
= 268-28 = 240 nos.
e) Total weight of the towers
= ( Total no. of suspension towers X weight of each suspension towers) + ( Total no. of
anchoring towers X weight of each anchoring towers)
= (240 X 2) + (28 X 2) = 536 Tones
f) No. of 15KV disc insulators, 70 KN grade,
i) At suspension string for tangent towers
= No.of suspension towers X No. of suspension strings/tower X No of insulator/suspension string.
= 240 X 3 X 4 = 2880 Nos.
ii) At tension string for anchoring towers
= No. of anchoring towers X No. of tension strings/tower X No of insulator/tension string.
= 28 X 6 X 5 = 840 nos.
Total no. of disc insulators= 2880+840 = 3720 nos.
Add 5% extra for breakage on total, i.e.,= 3720 X 0.05 = 186 nos.
Grand total = 3720 + 186 = 3906 nos.
g) Length of coyote ACSR conductor allowing 3% sag
= (Total length of the line in km X No. of conductor) X 1.03
= 80 X 3 X 1.03
= 247.2 = 248 kms
h) Length of the GI ground wire of size 7/3.15mm allowing 3% sag
= (Total length of the line in km X No.of ground wires) X 1.03
= 80 X 1 X 1.03 = 82.4 = 83 kms
i) Number of suspension clamps suitable for coyote conductor with arcing horns
= Total No. of suspension towers X No of suspension strings/tower.
= 240 X 3 = 720 sets
j) Number of tension clamps suitable for coyote conductor with arcing horns

8. 8
= Total no of anchoring towers X No of tension strings/tower.
= 28 X 6 = 168 sets.
k) Armoring rods suitable for coyote conductor
= No of suspension clamps + No of tension clamps
= 720 + 168 = 888 sets.
l) PG clamps suitable for coyote conductor
= No of anchoring towers X No of jumpers / tower X No of PG clamps / jumpers
= 28 X 3 X 2 = 168 nos.
m) Vibration dampers suitable for coyote conductor
= Total no of towers x 6 (for single circuit)
= 268 X 6 = 1608 nos.
n) Grounding materials including accessories = Total no of towers = 268 sets
o) Cement concrete for tower erection( 1:2:4) = Total no of towers X 12m3
= 268 X 12 = 3216 m3
p) Miscellaneous materials such as conductor accessories, ant climbing devices, danger boards,
phase plates, no. plates, bird guards, bolt nuts, and other unfortunate items.
2) Prepare a quantity of materials required for 60km, 110kv single circuit transmission line
across a jungle terrain using four legged fabricated steel structures.
Solution:
(Assuming Lynx ACSR conductor has to used and span length is 320m)
a) No. of spans=length of proposed line in meters/span length in meters = 60,000/320 = 188 nos
b) Total no. of four legged fabricated steel structures= No. of spans +1 = 188 + 1 = 189 nos.
c) No. of anchoring towers(Assuming every 10th tower is to be an anchoring)
= Total no.of towers /10
=189/10 = 19 nos
Total no of anchoring towers = 19 + 1 at starting point = 20 nos.
d) No. of suspension towers = total no. of towers – No. of anchoring towers
= 189 - 20 = 169 nos.
e) Total weight of the towers= ( Total no. of suspension towers X weight of each
suspension towers) + (Total no. of anchoring towers X weight of each anchoring towers)
= (169 X 3.5) +(20 X 4.5) = 682 Tons
f) No of 15KV disc insulators, 90 KN grade.
i) At suspension string for tangent towers=No of suspension towers X No of suspension
strings/tower X No of insulator / suspension string.
= 169 X 3 X 7 = 3549 nos.
ii) At tension string for anchoring towers=No of anchoring towers X No of
tension strings/ tower X No of insulator / tension string.
= 20 X 6 X 8 = 960 nos.

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Total no. of disc insulators = 3549 + 960 = 4509 nos.
Add 5% extra for breakage on total i.e., = 4509 X 0.05 = 225nos
Grand total no. of disk insulator = 4509 + 225 = 4734 nos.
g) Length of lynx ACSR conductor allowing 3% sag = (total length of the line in km X
no of conductor) X 1.03
= 60 X 3 X 1.03 = 185.4 km = 186km
h) Length of the GI ground wire of size 7/3.15mm allowing 3% sag = (total length of the
line in km X no of ground wire) X 1.03
= 60 X 1 X 1.03 =61.8 = 62km
i) No of suspension clamps suitable for Lynx conductor with arcing horns = Total no of
suspension towers X No of suspension strings/tower.
= 169 X 3 = 507 sets
j) No of tension clamps suitable for Lynx conductor with arcing horns = Total no of
anchoring towers X No of tension strings/tower.
= 20 X 6 = 120 sets
k) Armoring rods suitable for Lynx conductor = No of suspension clamps + No of tension
clamps
= 507 + 120 = 627 sets
l) PG clamps suitable for Lynx conductor = No of anchoring towers X No of jumpers /
tower X No of PG clamps / jumpers
= 20 X 3 X 2 = 120
m) Vibration dampers suitable for Lynx conductor = Total no of towers x 6 ( for single
circuit)
= 189 X 6 = 1134 sets
n) Grounding materials including accessories = Total no of towers = 189 sets
o) Cement concrete for tower erection = Total no. of towers X 12m3
= 189 X 12 = 2268 m3
p) Miscellaneous materials such as conductor accessories, ant climbing devices, danger
boards, phase plates, no. plates, bird guards, bolt nuts, and other unfortunate items.

10. 10
3) Prepare a detailed quantity of materials required for running a 120km, 220kv single circuit
transmission line across a jungle terrain using four legged fabricated steel structures. Assuming
average span length of 330m and conductor used is Drake ACSR.
Solution:
a) No. of spans = length of proposed line in meters/span length in meters
=120,000/330 = 363.6 = 364 nos.
b) Total no. of four legged fabricated steel structures = No. of spans +1
= 364 + 1= 365 nos
c) No. of anchoring towers(assuming every 10th tower is to be an anchoring)
= Total no. of towers /10
= 365/10 =36.5 nos = 37 nos
Total no of anchoring towers = 37 + 1 at starting point = 38
d) No. of suspension towers = Total no. of towers – No. of anchoring towers
= 365 – 38 = 327 nos.
e) Total weight of the towers= ( Total no. of suspension towers X weight of each
suspension towers) + ( Total no. of anchoring towers X weight of each anchoring towers)
= (327 X 4) +(38 X 5) = 1308 + 190 = 1498 Tons
f) No of 15KV disc insulators
i) At suspension string for tangent towers
=No of suspension towers X No of suspension strings/ tower X No of insulator / suspension string.
= 327 X 3 X 14 = 13734 nos.
ii) At tension string for anchoring towers
= No of anchoring towers X No of tension strings/ tower X No of insulator / tension string.
= 38 X 6 X 15 = 3420 nos.
Total no. of disc insulators=(13734 + 3420) = 17154 nos.
Add 5% extra for breakage on total, i.e.,=17154 X 0.05 = 858 nos.
g) Length of ACSR conductor allowing 3% sag
= (Total length of the line in km X no of conductor) X 1.03
= 120 X 3 X 1.03 = 371 km.
h) Length of the GI ground wire of size 7/3.15mm allowing 3% sag
= (Total length of the line in km X no of ground wire) X 1.03
= 120 X 1 X 1.03 = 124 km.
i) No. of suspension clamps suitable for Drake conductor with arcing horns
= Total no of suspension towers X No of suspension strings/tower.
= 327 X 3 = 981 sets.
j) No. of tension clamps suitable for Drake conductor with arcing horns
= Total no of anchoring towers X No of tension strings/tower.
= 38 X 6 = 228 sets.

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k) Armoring rods suitable for Drake conductor
= No of suspension clamps + No of tension clamps
= 981+228= 1209 sets.
l) PG clamps suitable for Drake conductor
= No of anchoring towers X No of jumpers / tower X No of PG clamps / jumpers
= 38 X 3 X 2 = 22 nos.
m) Vibration dampers suitable for Drake conductor
= Total no of towers x 6 ( for single circuit)
= 365 x 6 = 2190 sets.
n) Grounding materials including accessories = Total no of towers = 365 sets.
o) Cement concrete for tower erection = Total no of towers X 12m3
= 365 X 12 = 4380 m3
p) Miscellaneous materials such as conductor accessories, ant climbing devices, danger boards,
phase plates, no. plates, bird guards, bolt nuts, and other unfortunate items.

12. 12
6.7 SUB STATION:
A substation receives electrical power from generating stations through incoming transmission
lines and delivers electrical power through outgoing transmission lines. The electrical substation
is the part of a power system in which the voltage is transformed from high to low or low to high
for transmission, distribution, transformation and switching. The power transformer, circuit
breaker, bus-bar, insulator, lightning arrester are the main components of an electrical
substation.
6.7.1 - Single line diagram of 66/11KV, 5 MVA substation:
6.7.2 - Materials required for 66/11kV, 5MVA substations with specifications:
Example : Prepare a quantity of materials required for establishing a substation of capacity
5MVA, 66/11kv transformer. Assuming current market rates and as per K.P.T.C.L procedure.
Solution:
(Assuming two incoming lines as in above single line diagram)
Equipment’s on primary (66kv) side:
a) Lightning arresters metal oxide type, 66kv class
= 4 sets ( 2 for bus coupler and 2 for transformer)
b) Potential transformers 66kv class = 4 sets ( 2 for line and 2 for Bus bars)
c) Current transformers 800:1 ratio = 5 sets ( 2 for i/c line, 2 for o/g line, 1 for bus coupler) &
Current transformers 200:1 ratio = 2 sets ( 1 for each transformer)
d) Upright Isolators (G.O.S) double blade 800A, 66kv class with earth switch
= 4 sets (2 for i/c and 2 for o/g line)

13. 13
e) Upright Isolators (G.O.S) double blade 800A, 66kv class without earth switch
= 14 sets (2 for bus coupler and 12 for bus bars)
f) Circuit breakers SF6 type, 66kv class
= 7 sets (2 for i/c line, 2 for o/g line, 2 for Transformers and 1 for bus coupler)
g) Bus bars expansion type using ACSR conductor = 2 sets.
h) Transformers 5MVA, 66/11kv, with OLTC and all accessories = 2 sets
i) Control and Relay panels for 66kv lines = 4 sets ( 2 for i/c line and 2 for o/g line)
j) Control and Relay panels for Transformers = 2 sets ( 1set for each transformer)
k) Control and Relay panels for bus coupler = 1 set.
l) Power and control cables in between different equipment’s and control and relay panels
= lump sum in meters
m) G.I mounting structures for mounting different equipment’s = lump sum in metric tonnes
Equipment’s on secondary side (11kv):
a) 11kv , 1200A outdoor switch gear with breaker, CT, PT etc., = 6 sets
b) G.O.S 11kv, 400A double blade = 6 sets (for outgoing 11kv lines)
c) Lightning arresters 11kv, thyrite type = 6 sets (for outgoing 11kv lines)
d) Distribution transformer for station auxiliary supply 100 KVA, 11KV / 440V = 1 set
e) Underground cable of size 1X1000mm2 from transformer to 11kv switch gear
= lumpsum in meters
f) Underground cable of size 3X250mm2 from outdoor switch gear take off structure
= lumpsum in meters
g) Take off structures 9m long double pole structure = 6 sets
h) 110V, 60AH, batteries with batteries charger = 2 sets
i) Earth mat including pipe earthing and plate earthing = lump sum
j) LT AC panel board indoor type =1 set
k) Outdoor type AC distribution boards = lumpsum
l) DC distribution board indoor type = 1 set
m) Miscellaneous materials such as ACSR conductors, 15kv disc insulators, stain insulators,
different types of clamps, bolt nuts, fire extinguishers, name plates, danger boards and other
unfortunate items.