TransCo
Determination of
Minimum Right-ofWay (ROW) Width
for Overhead
Power
Transmission
Lines
Bienvenido D. Valeros
John C. Placente
ME TDSGA 2013, Bangkok, Thailand
May 2013
Objective
Study aims to:
1. Provide the technical basis of transmission line
right-of-way (ROW) width based on applicable
electrical and safety codes.
2. Determine opportunities on cost-savings by
paying only the ROW width that is needed by
TransCo.
ME TDSGA 2013, Bangkok, Thailand
2
TRANSMISSION LINE LENGTH
(in CKT-KM)
Luzon
As of CY2011
9,482
4,979
5,361
Visayas
PHILIPPINES
19,822
Mindanao
Mindanao
ME TDSGA 2013, Bangkok, Thailand
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Transmission Line Length
As of December 31, 2011
Voltage
(kV)
Luzon
(km)
Visayas
(km)
Mindanao
(km)
Total
(km)
500
491.15
0
0
491.5
350
214.79
259
0
473.79
230
3,136.07
171.92
0
3,307.99
138
0
1,296.24
2,269.50
3,565.74
115
209.45
0
0
209.45
69 & Below
2,632.90
2,148.47
2,076.55
6,857.92
ME TDSGA 2013, Bangkok, Thailand
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Right-of-Way (ROW)
is to provide
an access corridor for maintenance of
transmission lines, with consideration to
safety clearances and EMF exposure limits.
ROW Width
ROW Width
ME TDSGA 2013, Bangkok, Thailand
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ROW Width Determination
230 kV
12 m
40 Meters
ME TDSGA 2013, Bangkok, Thailand
Voltage
Level
(kV)
FIXED
Width
(m)
69
15
115
30
138
30
230
40
345
50
500
65
6
Proposed ROW Width Determination
230 kV
12 m
ROW= Design, EMF
ME TDSGA 2013, Bangkok, Thailand
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References for Determination
ME TDSGA 2013, Bangkok, Thailand
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Horizontal Clearance at Rest
Formula Above 36 kV, Altitude ≤ 1000 m
Philippine Electrical Code Rule 3.4.5.7(a)
WHCL R  WREST
 VLL  m

 0.01
 22
3


WHCL-R
is the effective horizontal clearance (@ rest), meters
WREST
is the horizontal clearance on PEC Table 3.4.5.3(a)(1)
for open supply conductors, 2.3 meters
VLL
is the line to line voltage, kV
m
is the maximum voltage multiplier;
1.05 (69-345kV) and 1.10 (500kV and above)
ME TDSGA 2013, Bangkok, Thailand
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Horizontal Clearance at Rest
(Computed)
Nominal
Voltage Level,
in kV
Maximum
Voltage Level,
in kV
Horizontal Clearance At
Rest, Altitude ≤ 1000 m,
in Meters
(Based on PEC)
69
72
2.50
115
121
2.78
138
145
2.92
230
242
3.47
345
362
4.17
500
550
5.26
ME TDSGA 2013, Bangkok, Thailand
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Horizontal Clearance,
Conductor Displaced by Wind
Formula for Above 36 kV, Altitude ≤ 1000m, Wind
Philippine Electrical Code Rule 3.4.5.3
WHCLW  WWIND
 VLL  m

 0.01
 22
3


WHCL-W
is the horizontal clearance requirement
when displaced by wind
WWIND
is the minimum wind clearance requirement as
listed in Table 3.4.5.2(a)(2); for overhead
conductor, 1.4 meters.
VLL
is the line to line voltage.
m
is the maximum voltage multiplier;
1.05 (69-345kV) and 1.10 (500kV)
ME TDSGA 2013, Bangkok, Thailand
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Horizontal Clearance When Conductor
is Displaced by Wind (Computed)
Nominal
Voltage Level,
Maximum
Horizontal Clearance With
in kV
Voltage Level,
in kV
Wind Displacement, Altitude ≤
1000 m,
in Meters
(Based on PEC)
69
72
1.60
115
121
1.88
138
145
2.02
230
242
2.57
345
362
3.27
500
550
4.36
ME TDSGA 2013, Bangkok, Thailand
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Conductor Swing Angle Calculation
IEC 60826, Philippine Electrical Code
2





/
2

C

V
1
C
R  GL  D  aW
C  tan 

m
g

a


C
ØC
ρ
CC
VR
GL
D
mC
g
aW
a
is the swing angle of the conductor blown by wind
is the air density (1.14-1.29, assumption: 1.16 kg/m3)
is the drag factor equal to 1.0 for stranded conductor
is the wind speed/velocity (meters/second)
is the span factor taking into account the effect of span
length (Values are 1.0 to 0.875 for 200 m to 600 m)
is the conductor diameter (meters)
is the conductor mass per unit length (kg/m)
is the gravitational acceleration constant (9.8 m/s2)
is the wind span
is the conductor span length (assumption: a=aW)
ME TDSGA 2013, Bangkok, Thailand
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Span Factor, GL
IEC 60826
Wind Span, aW
(meters)
200
250
300
350
400
450
500
550
600
ME TDSGA 2013, Bangkok, Thailand
Span Factor, GL
1.000
0.984
0.969
0.953
0.938
0.922
0.906
0.891
0.875
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Example
Condor (795 MCM), 270 KPH or 75 m/s
  / 2  CC  VR2  GL  D  aW 
C  tan 

mC g  a


1
C

kg 
2
  1.16 3 
m

m


1.0 75  0.9840.0277m  aW


2

s 





 tan1  
kg
1km 
m



1523
 9.8 2   a
km 1000m 

s 















Assumption: conductor span, a is assumed equal to
wind span, aW; therefore,
C  80.5
ME TDSGA 2013, Bangkok, Thailand
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Conductor Swing Angles Per KPH
Philippine Electrical Code 2, 2009
Condor (795 MCM) @ Span = 250 m
Wind
Speed
Zone
Swing
Angle
270 KPH
75 m/s
Zone 1
80.5O
240 KPH
67 m/s
Zone 2
78.2O
160 KPH
44.45m/s
Zone 3
64.5O
ME TDSGA 2013, Bangkok, Thailand
240
KPH
160
KPH
270
KPH
Example
The 230 kV double circuit
overhead conductors are
supported by two towers with
dimensions as shown. The two
towers are on same elevation
and the span between them is
250 meters. Surveyed data
from the field indicates that the
total insulator length and
conductor sag amounts to 6.0
meters. Conductor is in Zone 1
(270 KPH).
Recommend a minimum rightof-way (ROW) based on
clearances of conductors at rest
and under wind displacement.
ME TDSGA 2013, Bangkok, Thailand
TOWER
‘A’
TOWER
‘B’
250 m
1.5 m
1.5 m
4.5 m
NOT TO SCALE
FOR ILLUSTRATION ONLY
17
A. Compute for the Horizontal
Clearance at Rest
 230  1.05

 2.3  0.01
 22
3


 230  1.05

WHCL W  1.4  0.01
 22
3


5.92 m
80.5o
ME TDSGA 2013, Bangkok, Thailand
Clearance
At Rest
4.5 m
3.5 m
1.5 m
Clearance
With Wind
WHCLW  2.57 m  2.6 m
WHCL R  3.47 m  3.5 m
2.6 m
WHCL R
B. Compute for the Horizontal
Clearance, with Wind
18
Illustration #1
29.2 m
ME TDSGA 2013, Bangkok, Thailand
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2.6
2.6
5.92
2.42
5.92
3.5
ME TDSGA 2013, Bangkok, Thailand
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3.5
2.6
2.42
HORIZONTAL CLEARANCE, WITH WIND DISPLACEMENT
HORIZONTAL CLEARANCE AT REST
HORIZONTAL CLEARANCE, WITH WIND DISPLACEMENT
Illustration #2
2.6
29.04 m
20
ROW WIDTH ESTIMATES
Voltage Level
CURRENT
PROPOSED*
(kV)
(Fixed)
(Design Dependent)
69
15
6-12
115
30
11-26
138
30
11-26
230
40
20-32
345
50
23-38
500
65
33-53
ME TDSGA 2013, Bangkok, Thailand
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LATEST EMF EXPOSURE LIMITS
General Public, 60 Hertz, 2010 ICNIRP*
*International Commission on Non-Ionising Radiation Protection
PARAMETER
VALUE
Electric Field
4.17 kV/m
Magnetic Field
2000 milliGauss*
*1998 Value = 833 mG
ME TDSGA 2013, Bangkok, Thailand
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Limits: Electric Field = 4.17 kV/m
Magnetic Field = 2000 mG
Calculated EMF Levels
Information:
230 kV, Bundle of 4, 820 Amps Per Cond, Double Ckt
Distance from
Conductor
Centerline
(m)
0
2.5
5
7.5
10
12.5
15
17.5
20
Electric Field
(kV/m)
0.172
0.451
0.796
1.048
1.177
1.185
1.1
0.959
0.796
Magnetic Field
(mG)
186.44
184.06
177.71
167.53
154.09
138.43
121.88
105.68
90.69
Measured EMF Levels @ 5 m from Conductor Centerline
Transmission Line
Electric Field
Magnetic Field
Sucat-Araneta-Balintawak 230 kV
0.04
3.15
ME TDSGA 2013, Bangkok, Thailand
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Benefits
Reduction of area
acquisition cost of
28-32%.
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Way Forward
1. Status. Completed 10 Consultation meetings
with distribution utilities and other power
experts. Preparing for 2 more technical
consultations and then legal consultations.
2. Board Approval. Seek final
approval/recommendation from management
team.
3. Program Development. Create a software
and database system (tower design data, sag,
span) which will compute for ROW acquisition.
ME TDSGA 2013, Bangkok, Thailand
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FOR COMMENTS
Email:
MR. BIENVENIDO D. VALEROS
bdvaleros@transco.ph
MR. JOHN C. PLACENTE
jcplacente@transco.ph
MS. SHELYMAR F. AURIGE
sfaurige@transco.ph
MS. DIVINA I. CUSTODIO
dicustodio@transco.ph
ME TDSGA 2013, Bangkok, Thailand
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