Tes p-122.01-r0 (2)

PAGE NO. 2 OF 20TEP122.01R0/MAA
TRANSMISSION ENGINEERING STANDARD TES-P-122.01, Rev. 0
Date of Approval: October 17, 2006
TABLE OF CONTENTS
1.0 PURPOSE
2.0 SCOPE
3.0 CODES, STANDARDS & REFERENCES
4.0 ORDER OF PRECEDENCE
5.0 SYSTEM PARAMETERS
5.1 Frequency
5.2 Voltage
6.0 INSULATION LEVELS
7.0 SYSTEM CONVENTIONS
7.1 Circuit Configuration
7.2 Phase Designation
7.3 Phasing Sequence
8.0 SHORT CIRCUIT RATING
9.0 STRUCTURAL SUPPORTS
10.0 INSULATORS
10.1 Creepage Distance
10.2 Insulators in the Coastal Zone
10.3 Insulators in the Inland Area

11.0 HARDWARE
12.0 ENVIRONMENTAL CONSIDERATIONS
12.1 Appearance
12.2 Public Safety
12.3 Polluted Environment
13.0 WEATHER CONDITIONS
14.0 DESIGN INFORMATION
14.1 Wind Velocities
14.2 Soil Conditions
15.0 OBSTRUCTION MARKING AND LIGHTING
15.1 Spherical Markers
15.2 Warning Lights
16.0 TRANSPOSITION
17.0 LINE IDENTIFICATION
17.1 Circuit Designation
17.2 Voltage Level Designation
17.3 Structure Numbering
17.4 Structure Identification
17.5 Phase Identification
18.0 LIGHTNING PERFORMANCE
18.1 Outage Rate Due To Lightning
18.2 Overhead Ground Wires
19.0 BIBLIOGRAPHY

1.0 PURPOSE
The purpose of this standard is to clearly define design philosophy and practices
adopted by SEC to enable the design engineer to develop cost effective designs of
SEC Transmission Lines.
This standard is intended to serve as a reference and to give guidelines to SEC
engineers for engineering, design, construction, operation and maintenance of
Transmission Lines in SEC system. It is understood that consulting engineers,
designers, manufacturers, lump sum turnkey contractors and such other agencies that
do business with SEC in various capacities shall use this standard.
2.0 SCOPE
This standard:
2.1 Covers transmission lines for 69 kV, 110kV, 115 kV, 132kV, 230 kV and 380
kV systems.
2.2 Generally deals with the design philosophy and design practices as adopted by
SEC based on management directives, policy guidelines and the operation and
maintenance experience gained by SEC over a period of time particularly in
the onerous environmental conditions experienced in SEC franchise area.
2.3 Lays down the system parameters and tolerance limits as have been enunciated
by SEC and indicates the design criteria for various systems such as wood
poles, lattice structures, steel poles etc., which have been adopted by SEC as a
result of studies conducted from time to time.
2.4 Indicates ratings for various equipment and hardware, which have so far been
standardized by SEC.
2.5 Gives certain basic concepts of design, engineering, general assumptions and
guidelines, methods of calculations, typical examples for transmission lines to
be designed for various voltage levels for SEC network.
2.6 Intends to minimize the frequent references by the design engineers to various
international standards, other texts or technical papers and intends to furnish
the minimum needed information at one place, for particular use in SEC
system.
2.7 Does not intend to replace the international or national standards or other
reference documents.
2.8 Does not specify the material standard specifications for various materials and
equipment, which are covered separately under SEC Transmission Materials
Standard Specifications (TMSSs).

2.9 Assumes that all materials and equipment that are used in the transmission line
meet the requirements specified in the respective TMSS.
2.10 Does not cover the construction requirements of the transmission line, which
are covered under SEC Transmission Construction Standards (TCSs).
3.0 CODES, STANDARDS AND REFERENCES
3.1 Applicable codes, standards and other reference materials have been indicated
in each chapter of this "Transmission Line Design Standards (TES-P-122)".
3.2 Items not specifically covered in this standard (TES-P-122) shall be in
accordance with the latest revisions of the referenced Industry Codes and
Standards.
3.3 It shall be the responsibility of the design engineer preparing the base design or
detailed design to be or become knowledgeable of the requirements of the
latest Industry Codes and Standards referred in TES-P-122. He shall bring to
the attention of SEC, any latest revisions of these Codes and Standards, which
may have an impact on the technical requirements of TES-P-122.
3.4 Whenever equivalent Codes and Standards are used, SEC approval to the same
shall be obtained before proceeding with the design. The equivalent Codes and
Standards shall be equal to or better than those specified in TES-P-122. Copy
of the equivalent Codes and Standards and the comparison with the specified
Codes and Standards shall be provided to SEC for review and acceptance.
4.0 ORDER OF PRECEDENCE
In case of any conflict between various documents and standards or specifications, the
order of precedence shall be as follows:
4.1 The Scope of Work and Technical Specifications (SOW/TS) for any project
4.2 SEC Transmission Materials Standard Specifications (TMSSs)
4.3 The Transmission Line Construction Standard TCS-P-122
4.4 This Transmission Line Design Standards (TES-P-122)
If there is any conflict between different chapters of TES-P-122, and/or TCS-
P-122 then the applicable chapter shall have the precedence over the other
chapters
4.5 Other applicable SEC Engineering Standards (TESs)
4.6 Applicable Industry Codes and Standards

5.0 SYSTEM PARAMETERS
5.1 Frequency
The nominal frequency for SEC system is 60 Hz and the permissible operating
frequency range is between 59.9 Hz and 60.1 Hz. The transient frequency
variations shall be between 58.5 Hz and 61.5 Hz.
5.2 Voltage
The standard nominal system voltages adopted by SEC are listed in Table 01-1.
The permissible operating voltage range is ± 5% under normal operating
conditions and ± 10%, for 30 minutes, under emergency operating conditions.
These are detailed in Table 01-1.
Table 01-1: Permissible Operating Voltage Ranges
Nominal
System Voltage
(kVrms)
Voltage Range
(Normal Operating
Condition), kVrms
Voltage Range
(Emergency Operating
Condition for 30 minutes),
kVrms
69 65.6-72.5 62.1-75.9
110 104.5-115.5 99-121
115 109.3-121 103.5-126.5
132 125.4-138.6 118.8-145.2
230 219-241.5 207-253
380 361-399 342-418
6.0 INSULATION LEVELS
The insulation levels for all equipment shall not be less than the values specified in
Table 01-2. For installations at an altitude higher than 1000 m, the insulation
requirements shall be calculated by multiplying the insulation value indicated in the
Table 01-2 below by the altitude correction factor as specified in IEC 60694 & IEC
60071-1.
Basic lightning impulse insulation levels (BIL) are specified with respect to a standard
1.2/50 μs wave shape and the basic switching impulse insulation level (BSL) is
specified for a 250/2500 μs impulse.

Table 01-2: Insulation Levels
Nominal
System Voltage
(kVrms)
Basic
Insulation
Level (BIL),
kVPeak
Power
Frequency
Withstand
Votage
*Dry/Wet,
(kVrms)
Basic
Switching
Impulse Level
(BSL), kVrms
69 350 160/140 -
110 650 275/275
115 650 275/275 -
132 750 325/325 -
230 1050 460/460 -
380 1425 620/620 1050
*Dry for 1 minute, wet for 10 seconds
7.0 SYSTEM CONVENTIONS
7.1 Circuit Configuration
Three-phase three wire (3φ-3W) circuit configuration shall be used throughout
SEC system for all voltage levels from 380 kV down to 69 kV.
7.2 Phase Designation
The phases shall be designated as R (Red), Y (Yellow) and B (Blue) for
untransposed lines, when viewed from East to West, from North to South, and
Top to Bottom. For transmission lines with delta configuration same phase
designation shall be applied when viewed from top to inner and inner to outer
phases. This convention shall be applied from the source substation.
7.3 Phasing Sequence
All 230 kV (vertical and delta configuration) and 380 kV (vertical
configuration) double circuit transmission lines shall have phase arrangement
of RYB-BYR i.e., the phases on the two circuits shall be located in a
completely reversed order to reduce line unbalance and induced ground wire
currents.

8.0 SHORT CIRCUIT RATING
The 3φ symmetrical interrupting (short circuit) current ratings of the various
transmission line equipment shall be as specified in Table 01-3.
Table 01-3: 3φ Symmetrical Interrupting Short Circuit Current
Ratings for Various Transmission Line Equipment
Transmission Line Nominal
Voltage Rating, kV
3φ Symmetrical Interrupting
Current, kArms
380 50/63*
230 50/63*
132 40
115 40
110 40
69 31.5/40*
* The design engineer shall select and specify in the SOW/TS the
appropriate value of short circuit rating applicable for the
area/location of the transmission line.
9.0 STRUCTURAL SUPPORTS
In SEC system wood poles are used for 69kV and 115kV system, steel monopoles for
69kV, to 230kV and lattice structures for 69kV to 380kV system.
10.0 INSULATORS
Cap and pin disc type porcelain/glass insulators (fog/aero form), Long Rod type
porcelain (aero form) and Composite insulators are used in the SEC system. The type
of insulators to be used for a particular project shall be specified in the relevant
SOW/TS.
10.1 Creepage Distance
All suspension and tension strings with porcelain or glass insulators shall have
a minimum leakage (creepage) distance of 50mm/kV (line to line nominal
system voltage) for transmission lines located in the Coastal Area (the area
located within a distance of 100 km and 50km from the sea coast line for
Consolidtaed Transmission Area and Developing Transmission Area
respectively).

All suspension and tension strings with porcelain or glass insulators shall have
a minimum leakage (creepage) distance of 40mm/kV (line to line nominal
system voltage) for transmission lines located in the Inland Area (the area
located beyond the above specified limits).
For the existing transmission lines in the Inland Area (SEC Central Operating
Area and SEC Southern Operating Area) where a creepage distance of
31mm/kV has been used and no problems have been encountered due to this,
the same creepage distance may be adopted for future transmission lines.
When Composite insulators are used, the creepage distance shall be kept as
40mm/kV both for suspension and tension strings. These types of insulators
may be used for transmission lines located in the Coastal Areas.
10.2 Insulators in the Coastal Area
When using fog type cap and pin disc insulators on transmission lines located
in the coastal zone, the number of units in each string (suspension and tension)
shall be as follows:
Table 01-4: Fog Type Cap and Pin Disc Insulators in the Coastal Area
(Based on 50 mm/kV Creepage Distance)
Line
Voltage
(kV)
String
Configuration
Number
of
Insulators
Insulator
String
Length
(mm)
Insulator Rating,
Leakage Distance,
and Spacing
(kN, mm, mm)
Suspension FI-8 1168 111, 432, 146
69
Tension FH-8 1248 160, 432, 156
Suspension FI-13 1898 111, 432, 146
110
Tension FH-13 2028 160, 432, 156
Suspension FI-14 2044 111, 432, 146
115
Tension FH-14 2184 160, 432, 156
Suspension FI-16 2336 111, 432, 146
132
Tension FH-16 2496 160, 432, 156
Suspension FI-22 3212 111, 545, 146
230
Tension FH-22 3422 160, 545, 156
Suspension FI/FV-35 5460 160, 545, 156
380
Tension FH-35 5950 222, 545, 170

When using Long Rod type insulators on transmission lines located in the
coastal zone, the insulators in the suspension and tension strings shall have the
ratings as follows:
Table 01-5: Long Rod Type Insulators in the Coastal Area (Based on 50
mm/kV Creepage Distance)
Specified Mechanical Failing Load (SFL)Nominal
System Voltage
(kV)
Creepage
Distance
(mm)
Suspension (kN) Tension (kN)
69 3450 120 160
110 5500 120 160
115 5750 120 160
132 6600 120 160
230 11500 120 160
380 19000 160 210
380 19000 160 330
Note: 1. While replacing insulators on the existing transmission lines
adequate conductor clearances to structure/ground must be
maintained.
2. A detailed study must be carried out to determine the proper
insulation requirements before insulation level is increased on the
existing 115 kV transmission lines in the coastal area, where no
surge arresters are installed at the substation entrance.
10.3 Insulators in the Inland Area
Transmission lines located in the inland area shall have Fog type insulators or
Aero-Form type insulators or Long Rod type insulators. When using aero form
type insulators on the existing structure designs adequate conductor clearances
to structure/ground must be ensured. A detailed techno-economic study must
be carried out when aero form type insulators are to be used for new
transmission lines employing new structure designs.
Long Rod type insulators on transmission lines located in the Inland Area shall
have the ratings as follows:

Table 01-6: Long Rod Type Insulators in the Inland Area (Based on 40
mm/kV Creepage Distance)
Specified Mechanical Failing Load (SFL)Nominal
System Voltage
(kV)
Creepage
Distance
(mm)
Suspension (kN) Tension (kN)
69 2760 120 160
110 4400 120 160
115 4600 120 160
132 5280 120 160
230 9200 120 160
380 15200 160 210
380 15200 160 330
Number of Fog Type insulators in each string (suspension and tension) shall be
as follows:
Table 01-7: Fog Type Cap and Pin Disc Insulators in the Inland Area (Based
on 40 mm/kV Creepage Distance)
Line
Voltage
(kV)
String
Configuration
Number
of
Insulators
Insulator
String Length
(mm)
Insulator Rating,
Leakage Distance,
and Spacing
(kN, mm, mm)
Suspension FI-7 1022 111, 432, 146
69
Tension FH-7 1092 160, 432, 156
Suspension FI-11 1606 111, 432, 146
110
Tension FH-11 1716 160, 432, 156
Suspension FI-11 1606 111, 432, 146
115
Tension FH-11 1716 160, 432, 156
Suspension FI-13 1898 111, 432, 146
132
Tension FH-13 2028 160, 432, 156
Suspension FI-22 3212 111, 432, 146
230
Tension FH-22 3422 160, 432, 156
Suspension FI/FV-28 4368 160, 545, 156
380
Tension FH-28 4760 222, 545, 170

Table 01-8: Aero Form Type Cap and Pin Disc Insulators in the Inland Area
Line
Voltage
(kV)
String
Configuration
Number
of
Insulators
Insulator
String Length
(mm)
Insulator Rating,
Leakage Distance,
and Spacing
(kN, mm, mm)
Suspension AI-9 1314 111, 335, 146
69
Tension AH-9 1404 160, 335, 156
Suspension AI-14 2044 111, 335, 146
110
Tension AH-14 2184 160, 335, 156
Suspension AI-14 2044 111, 335, 146
115
Tension AH-14 2184 160, 335, 156
Suspension AI-16 2336 111, 335, 146
132
Tension AH-16 2496 160, 335, 156
Suspension AI-28 4088 111, 335, 146
230
Tension AH-28 4368 160, 335, 156
Suspension AI/AV-46 7176 160, 335, 156
380
Tension AH-46 7820 222, 335, 170
Table 01-9: Aero Form Type Cap and Pin Disc Insulators in the Inland Area
Line
Voltage
(kV)
String
Configuration
Number
of
Insulators
Insulator
String Length
(mm)
Insulator Rating,
Leakage Distance,
and Spacing
(kN, mm, mm)
Suspension AI-7 1022 111, 335, 146
69
Tension AH-7 1092 160, 335, 156
Suspension AI-11 1606 111, 335, 146
110
Tension AH-11 1716 160, 335, 156
Suspension AI-11 1606 111, 335, 146
115
Tension AH-11 1716 160, 335, 156
Suspension AI-13 1898 111, 335, 146
132
Tension AH-13 2028 160, 335, 156
Suspension AI-22 3212 111, 335, 146
230
Tension AH-22 3432 160, 335, 156
Suspension AI/AV-36 5616 160, 335, 156
380
Tension AH-36 6120 222, 335, 170

Where:
FI = Suspension Insulator string in vertical position (fog type
insulators)
FV = Suspension Insulator string in diagonal position (fog
type insulators)
FH = Suspension Insulator string in horizontal position (fog
type insulators)
AI = Suspension Insulator string in vertical position (aero
form type insulators)
AV = Suspension Insulator string in diagonal position (aero
AH = Suspension Insulator string in horizontal position (aero
11.0 HARDWARE
11.1 The ratings of line hardware shall equal or exceed the Mechanical and
Electrical strength ratings of the insulator or the ultimate load it shall support
and as specified in the relevant TES/TCS and SOW/TS. The range of hardware
fitting used in SEC transmission system shall be as per relevant TMSS.
11.2 The line hardware on suspension and tension strings shall be suitable for
removal and/or replacement of insulators and fittings by tools designed for hot-
line/live-line working/maintenance operations. On double insulator strings for
both suspension and tension, yoke plate must have the same shape and
thickness so that the same tool can be used for maintenance.
12.0 ENVIRONMENTAL CONSIDERATIONS
12.1 Appearance
12.1.1 Load growth has brought the need to transmit bulk power to areas of
thick population resulting in the increasing contact with these
transmission lines. Therefore transmission lines are to be designed
taking into account impact of electromagnetic fields, aesthetic design
and impact of physical location.

12.1.2 The insulation of line, air gap, and insulator strings shall be designed
to withstand switching surges, fault initiated over voltages and
lightning impulses. Tower dimensions are affected by the number of
insulators, type of string for insulators, type of insulator and
clearances.
12.1.3 Transmission line shall consider nearby airports and aeronautic
corridors (if any), as they are usually restricted on the maximum
height.
12.1.4 Transmission lines shall be designed taking into consideration
acceptable level of radio noise, television interference, audible noise
and ozone generation. Proper considerations shall be given to
conductor diameter.
12.2 Public Safety
12.2.1 Transmission lines shall be safe for people who have occasion to be
near them.
12.2.2 Primary means of ensuring public safety is by providing anticlimbing
device approximately 4 meters above ground, wherever transmission
lines are accessible to public or within one (1) km of residential or
public areas. Steel monopoles shall also require anticlimbing devices.
12.2.3 Appropriate warning signs shall be provided on transmission line
supports per relevant TCS. Whenever necessary crash barriers shall
also be provided for safety of the supports.
12.3 Polluted Environment
12.3.1 The areas through which SEC transmission lines run are characterized
by extreme atmospheric pollution with various degrees of sand, dust
and salt. Due to low rainfall in the area, the natural washing of
insulators is insufficient to control insulator contamination,
accumulation and flash over may occur.
12.3.2 The insulators specified in 15-TMSS-02 to 15-TMSS-05 standards
are intended to withstand an ESDD (Equivalent Salt Deposit Density)
of at least 0.3 mg/cm² in inland area and 0.55 mg/cm² in coastal area.
13.0 WEATHER CONDITIONS
The environment in Saudi Arabia can best be characterized by intense summer heat
and frequent strong winds. However, heavy rains and sand storms occasionally occur
in this desert climate. The atmosphere is highly corrosive, particularly near the coastal
line.

All transmission line equipment/materials shall be suitable for operation at their
standard ratings under the usual service conditions in the inland desert or coastal areas
environment of Saudi Arabia as specified in 01-TMSS-01.
14.0 DESIGN INFORMATION
The transmission line shall be designed taking into consideration the basic parameters
such as the size of conductor, conductor configuration, length of line, nominal voltage,
fault current, load requirement and transposition.
14.1 Wind Velocities
Conductors, structures and all poles are to be designed for a wind velocity of
150km/hr. Funneling of winds may occur where there is a natural flow of air
from an unrestricted area through a restricted area, such as a mountain pass and
the wind velocity may gets accelerated. The design engineer shall study the
effect of wind funneling in such areas and take into account, the increased
loadings, if the wind velocity is greater than that specified above.
14.2 Soil Conditions
14.2.1 Surface conditions include salt flats (sabkhah), marl, aeolian sand and
rock. Sabkhah areas shall be avoided as far as possible.
14.2.2 Ground water table varies from near surface in the coastal zone to
several meters below grade in inland areas.
14.2.3 Areas of sand and marl presents the problem of shifting of the over
burden due to wind action. This problem can be alleviated to some
extent by elevating the soil surface at each foundation and stabilizing
the elevated surface with crude oil. This practice tends to prevent the
depositing of windborne sand at the foundation. This practice
prevents surface sand moving away from the foundation.
14.3 Conductor Clearances
Transmission lines shall be designed based on phase to phase, phase to ground
and other clearances as specified in the Engineering Standard TES-P-122.09.
15.0 OBSTRUCTION MARKING AND LIGHTING
Transmission lines located near the ends of the airport runways shall require warning
lights and sphere marking to warn pilots of potential collision with the structures and
conductors. The design engineer responsible for the detailed design shall arrange to
contact the aviation authorities to determine the requirements and ensure compliance
to the same.

15.1 Spherical Markers
15.1.1 Daylight spherical markers shall be installed on the shield wire per
12-TMSS-03. The color of spherical markers shall be aviation
Orange. The spherical marker shall be equally spaced along the span
conforming to the requirements of the aviation authorities.
15.1.2 The markers shall be recognizable in clear weather from a distance of
1219m (4000 ft) for an object to be viewed from the air and 305 m
(1000 ft) for an object to be viewed from the ground in all directions
in which an aircraft is likely to approach.
15.1.3 To retain the general definition of the object being marked, markers
shall be displayed in conspicuous positions, i.e. shall be spaced
equally along the wire at an interval of not more 61 m (200 ft). This
interval in critical areas near airport runway end shall be in the range
of 10 to 15 m.
15.1.4 Spherical markers shall be placed on the highest wire and where there
are two wires at the same height; they may be installed alternately
along each overhead ground wire only and not on composite optical
fiber ground wire (OPGW) to facilitae easy maintenance of OPGW.
The distance between the adjacent markers shall be maintained as
above. This method shall allow the weight and wind loading to be
distributed.
15.1.5 In order to protect the damage of conductor/shield wire strands at
sphere clamp due to aeolian vibrations, each spherical marker shall be
equipped with at least one Stockbridge type vibration damper, the
placement distance to be determined by the damper manufacturer
through analytical vibration damping study. Preformed aluminum
alloy armor rods shall be installed on the shield wire before installing
the spherical markers to protect the strands from any damage.
15.2 Warning Lights
15.2.1 Conductor Warning Lights
Nighttime warning lights shall be installed on the phases of overhead
lines per 12-TMSS-03.
The complete light assembly when installed on the conductor shall
not be affected by the vibrations transmitted by the conductor. To
eliminate the risk of deterioration, each phase conductor light
assembly shall be equipped with two Stockbridge vibration dampers,
the placement of which shall be determined by the damper
manufacturer through analytical vibration damping study.

15.2.2 Tower Warning Lights (Beacons)
Nighttime warning lights shall be required on the towers per 12-
TMSS-03. The power requirement for beacon light shall be decided
in consultation with SEC.
Self-illuminated spherical marker may also be used (if practicable) in
place of tower beacon lights. The diameter of marker shall be in the
range of 510 mm to 610 mm. The power source for these markers
shall be the magnetic field surrounding the phase conductors.
16.0 TRANSMISSION LINE UNBALANCE AND TRANSPOSITION
The degree of unbalance over a set of three-phase transmission line is produced by
asymmetrical placement of line conductors above ground plane. This unbalanced
condition leads to generation of negative and zero sequence voltage and currents,
which may have adverse effect sufficient to require line transposition.
Line transposition shall be made for the purpose of reducing the electrostatic and
electromagnetic unbalance among the phases, which can result in unequal voltages for
long lines. Line transposition is changing the position of phase conductors so that
within a specified length of a line, each conductor occupies the position of all the three
phase conductors for the same length.
All 230 kV and 380 kV transmission lines greater than 90 km in length shall be
transposed, whereas, transmission lines less than 90 km in length may not require any
transposition. The transposition shall be done at equal intervals along the line at points
having L/3 distance (L being the length of transmission line between two terminal
stations). After transposition, the relative phasing sequence on double circuit lines
shall be kept in a reversed order as described in Clause 7.3.
In case of inductance interference with parallel communication lines due to
untransposed line, system interference can be prevented by transposition of telephone
line or installing buried telephone much more economically and it is always necessary
to transpose a power line only.
17.0 LINE IDENTIFICATION
17.1 Circuit Designation
17.1.1 On single circuit wood pole or latticed steel structures; circuit
designation plates “A” or “B” shall be installed on all structures
facing the tap off point or source. These plates shall be mounted on
the transverse faces of the structure approximately three (3) meters
above the ground level.

17.1.2 On double circuit tower structures, an “A” or “B” shall be installed on
the respective side of the tower to correctly identify which side of the
tower carries which line.
17.2 Voltage Level Designation
Transmission system voltage level shall be shown on the structure
identification plates.
17.3 Structure Numbering
17.3.1 On all radial feeders and tap lines, the structure numbering shall begin
at the line origin and shall increase toward line destination. The line
name designation shall be determined by the destination of the line
rather than the name of the main lines.
17.3.2 On other transmission lines, the structure numbering shall begin with
structure one from south to north or west to east. This geographical
direction is dependent on the location from transmission line to
transmission line and not the direction of the line at any point. The
line name designation shall be according to the station name at each
end of the line with the first name listed dependent on the same
geographical directions listed above; i.e., the Abqaiq-Qurayyah line
shall be designated by AB-QU.
17.3.3 Re-numbering of transmission line structures for re-routing or
introduction of additional structures shall begin at the origin and shall
increase towards line destination. Approval of SEC Lines
Maintenance shall be obtained if the affected nearest structure is used.
17.4 Structure Identification
17.4.1 All structures shall have their respective structure numbers on them
but the aerial line identification plates shall be installed on every tenth
structure, the first structure, the last structure and on both structures
adjacent to a crossing highway, rail road and access road.
17.4.2 Structure identification plates for aerial inspection shall be installed
on top transverse face of the structure. Two plates shall be installed
per structure one on ahead of the line and one on the back.
17.4.3 Physical layout of the markings on structure identification plates for
aerial inspection shall include Voltage Level, Source Substation
Name, Ending Substation Name and Structure Number.
17.4.4 Structure identification plates for ground inspection shall be installed
on the transverse face of every structure three (3) meters above the
ground level when viewed in the direction of increasing structure
numbers. However, if structure identification plates installed in the

normal position will not be readily visible from the access road, they
shall be installed on the structure faces best exposed to view from the
access roads.
17.4.5 Physical layout of the markings on structure identification plates for
ground inspection shall include Circuit Designation, Voltage Level,
Source Substation Name, Ending Substation Name and Structure
Number.
17.5 Phase Identification
17.5.1 All transmission lines in the SEC power system, which do not require
transposition, shall have the phases identified per clause 7.2.
17.5.2 In transposed lines, the correct phasing shall be indicated on
transposition structures whenever the conductor phasing changes and
shall be marked “TRANSPOSED LINE”.
17.5.3 Phase identification plates shall be installed next to the structure
identification plates and phasing shall be indicated wherever the
phasing configuration changes.
17.5.4 The structures requiring phase marking shall be indicated on the Plan
and Profile drawings by the symbol “φ“ and shall be marked
“TRANSPOSED” next to the structure numbers.
18.0 LIGHTNING PERFORMANCE
18.1 Outage Rate Due To Lightning
Overhead ground wires are provided in transmission lines as shielding
protection against lightning. The outage due to lightning is based upon the
number of strokes terminating on the overhead ground wires; which result in
structure flashovers and mid span overhead ground wire flashover. The outage
rate due to lightning shall not be more than 0.62 per 100 km per year for an
isokeraunic level as specified in 01-TMSS-01.
18.2 Overhead Ground Wires
18.2.1 The overhead ground wire requirements on transmission lines are
specified below:
a. On all wood pole transmission lines, overhead ground wires
shall be provided, unless otherwise specified in the Project
Technical Specifications.
b. Due to the higher conductor elevation of all latticed and steel
monopole transmission lines, continuous overhead ground wires

of sufficient strength shall be provided to shield the line
conductors from direct lightning strokes.
c. Overhead ground wires shall be adequately bonded to each steel
structure or wood pole structure grounding. Whenever there are
two overhead ground wires on a wood pole structure, they shall
be tied together at the top of each structure to reduce the
impedance to ground.
18.2.2 Shield Angle
For 380kV transmission lines, the shielding angle shall be 20 degrees
or less whereas for all other transmission lines (69 kV to 230 kV) the
shielding angle may be kept up to 30 degrees maximum. However, in
each case the outage rate due to lightning shall not exceed the
maximum value specified in Clause 18.1 above.
19.0 BIBLIOGRAPHY
19.1 Electric Transmission and Distribution Reference Book, Westinghouse.
19.2 Design Manual for High Voltage Transmission Lines, Rural Electrification
Administration (US Department of Agriculture).
19.3 Transmission Line Reference Book 345 kV and Above, Electric Power
Research Institute.

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