TES-P-122.09

CLEARANCES AND RIGHT OF WAY REQUIREMENTS, SEC (Saudi Electricity Company) STANDARD, Transmission Engineering Standard (TES)

The purpose of this standard is to highlight National Gird Saudi Arabia practices with respect to the clearances required for various paralleling and crossing facilities and Right of Way (ROW) requirements for the design of overhead transmission lines.

The designs of existing transmission lines may not in all cases meet the requirements set forth in this standard, therefore; those are excluded from the scope of this standard. However, taps from or extensions to these existing transmission lines are covered under the scope of this standard. Conductor Clearance to edge of Right-of-Way

  1. SCOPE

FIGURE TE-2209-0100-00    Clearance Requirement for Conductors of Same Circuit or Different

Circuit on the Same Support

FIGURE TE-2209-0200-01    Right-Of-Way (ROW) for Single Transmission Line

FIGURE TE-2209-0300-01    Right-Of-Way (ROW) for Two Parallel Transmission Lines (identical insulator string configuration)

FIGURE TE-2209-0400-01    Right-Of-Way (ROW) for Two Parallel Transmission Lines (different

insulator string configuration).

TES-P-122.09

  1. SCOPE

Method of StatesmenMethod Statement for construction of Access Road and Structure Pads

TES-P-122.09

Transmission line crossings shall be designed keeping in view the network reliability and the ease in routine maintenance/inspection operations.

  1. Crossing Below the Existing Transmission Lines

Gantry structures (single layer or double layer as applicable) with conductors in horizontal configuration shall be used for crossing below the existing transmission lines. The crossing arrangement shall be designed to provide full protection to the underneath transmission line from lightning using shield wires or other means. If required, optical fiber ground wire (OPGW) may be replaced with underground non- metallic fiber optic cable in concrete encased duct bank.

  1. Transmission Line Crossing (two lines of same voltage)

The security/importance/priority of the existing transmission line shall be decided by National Grid Saudi Arabia.

  1. Transmission Line Crossing (more than two lines of same voltage or higher/lower voltage)

The transmission line shall cross below the existing lines of the same or higher voltage but shall cross above the lower voltage line. If required, modifications to existing transmission line structures may be made to meet the clearance requirements.

For all cases where higher voltage transmission line shall cross below the lower voltage transmission line, approval of National Grid Saudi Arabia shall be mandatory.

National Grid Saudi Arabia will allow crossing above the existing 380kV transmission line only if it does not jeopardize the safety, security, and reliability of the existing lines.

National Grid Saudi Arabia may approve the design of a common supporting structure, which acts as a shared support for each transmission line and forms an integral part at the crossing point, where practical, for crossing two transmission lines of the same or different voltages.

Major highways are defined as any primary or secondary roads which are normally accessible to traffic with no restriction. These highways are the backbone of the road network providing fast, safe and efficient routes of travel between major cities/towns, connecting two or more regions and serve all international airports/seaports connections and military installations within the Kingdom of Saudi Arabia. Traffic on these highways is of primary importance. Minimum distance from transmission line center to the edge of zone of major highways for restricted and unrestricted ROW are given in Table 09-1. The edge of zone of major highway is defined as the fencing line or a point at 5 meters distance from the toe of slope, whichever is farther.

Table 09-1: Distance between Transmission Line and Major Highways

  Line Voltage, kVMinimum distance from transmission line center to the edge of zone of major highways, meters
Un-Restricted ROW (Notes 1 & 3)Restricted ROW (Notes 2 & 3)
69Maximum Height of Transmission Line Structure Plus 5 meters20
110/115/13230
23035
38050 (Note 4)

Notes to Table 09-1:

  1. Un-restricted ROW is that which imposes no or minimum restrictions on the land use.
  2. Restricted ROW is the area where land use is limited because of congestion due to other facilities and/or non-availability of land due to other reasons.
  3. In certain cases the owner of highways (Ministry of Transport – MOT or others) may require higher distances than those given in the above table. In all such cases, the concerned authorities shall be consulted to determine the exact requirements. Their approval shall be mandatory.
  4. Minimum distance from the conductors shall be maintained as 40 meters.

Where transmission line routes cross major highways, the angle of intersection shall be as close as possible to 90 degrees, but shall not be less than 45 degrees in any case. The distance from the center of transmission line structure to the edge of the zone of major highways shall be as per table 09-1

When paralleling and crossing roads other than major highways, especially in urban or rural areas, you must ensure that the minimum distance from the transmission line center to the edge of the road is at least 20 meters for 69kV to 132kV lines, 25 meters for 230kV lines, and 40 meters for 380kV lines, as long as public safety and the reliability of the lines are not affected.

If required, the transmission lines may be located in the medians of the two roads in the built-up areas subject to approval from owner of the roads and National Grid Saudi Arabia. Existing right of way of the roads shall be applicable in this case. You must maintain specified conductor clearances over the road surface, buildings, and other installations at the edge of the right of way, and protect structures with crash barriers.

TES-P-122.09

All line structures where foundations are located within a distance of 30 meters from the edge of travelled portion of roads (paralleling or crossing transmission line routes including major highways) shall be protected by providing crash barriers around them without jeopardizing access to the line for maintenance. These protective measures shall be considered individually on a project basis for their effectiveness. The general design of the crash barriers shall be as per Transmission Standard Drawing TB-800095.

transportation of very heavy equipment of extended height in the industrial areas.

Table 09-2: Vertical Clearances for Roads and Terrain Crossings

  Category  Type of CrossingTransmission Line Voltage (Line to Line) kV
69/110-132 (m)230 (m)380 (m)
A.Designated High Clearance Roads (Note 1)14.018.018.0
B.Expressways & Highways12.015.015.0
C.City Streets, Alleys Driveways, Parking Lots & Other Areas Traversed by Vehicles, Paved or Unpaved12.015.015.0
D.Open Terrain, Desert Areas, etc. (Notes 2 & 3)7.58.010.0
  ERailroad (non-electrified) (Note 4)15.518.018.0
Railroads (electrified) Top of contact wire/feeder of electrified rail (Note 5)  1.4  2.0  3.0
F.Ground Facilities, Pipelines (Oil, Water, Gas), Communication lines9.59.513.5
G.Extra High Clearance (Module-Paths)404040
H.Top of Trees, Plants & Hedges etc. capable of supporting a ladder or being climbed. (Note 6)4.05.06.0
I.Transmission Line Crossings with Gantry Structures (Note 7)55.77

Notes to Table 09-2:

  1. Roads categorized as “A” are those specifically designated by National Grid Saudi Arabia Asset Maintenance Department as roads requiring vertical clearance in excess of clearances listed in Category “B” and “C”. Vehicle traffic is expected to exceed 5.5 meter height and the transmission lines need not normally be removed from service.
  2. For transmission lines when located in open terrain within 15km and 5km from the boundary limits of metropolitan cities and other cities/towns/villages respectively, the required clearances listed under Category “D” shall be increased to that required under Category B or C.
  3. When transmission lines are located in desert area affected by shifting sand dunes, the clearance listed in Category “D” shall be increased by a minimum of two (2) meters in the spans indicating shifting sand dunes.
  4. Assumed height of the rail car (non-electrified) is 6 meters.
  5. Additional margins of 1.0 m and 2.0 m (total 3.0 m) shall be added to account for design errors and wind induced dynamic conductor movement/safety during maintenance operations respectively.
  6. As a general practice, trees and plants etc. are not allowed within transmission line ROW. The clearances mentioned above are under exceptional cases when these cannot be removed.
  7. The clearances listed under category I shall only be applicable when clearances under category D are not possible to achieve / maintain and shall only be considered if crossing area is properly fenced as per Company Standard and no access is allowed to the general public .
  8. The clearances shall be increased @ 3 % for each 300m in excess of 1,000m altitude above mean sea level.
  9. A margin of 0.6 m clearance specified in TES-P-122.07 to account for plotting profile errors etc. shall be in addition to the values mentioned in Table 09-2 above.
  1. Table 09-3 provides the minimum distance from the center of the transmission line to the edge of the railroad track for restricted and unrestricted rights of way. The edge of the railroad track is defined as either the fencing line or a point 5 meters from the toe of the slope, whichever is farther.

Whenever the required crossing angle is not satisfied, the Engineer responsible for base design/detailed engineering shall perform an induced voltage study and recommend possible steps to be taken to reduce any adverse effects.

Table 09-3: Distance between transmission line and Railroad

  Line Voltage, kVMinimum distance from transmission line center to the edge of railroad track, m
Unrestricted ROWRestricted ROW
69/110/115/1324030
2304535
3805550 (Note 1)

Note 1: Minimum distance from the conductors shall be maintained as 40 meters.

You must follow the guidelines listed below for all customer requests involving metallic facilities, such as pipelines, railroads, communication cables, cathodic protection systems, etc., whether overhead, above ground, or underground, to cross or run in close proximity to National Grid Saudi Arabia transmission lines. Apply these guidelines to all facilities in a single location if the request involves more than one facility.

  1. Accepts full liability and any consequential damages due to the electrical interference (induced/conductive voltage) effects and satisfies conditions given in Clause 3.3.1 and 3.3.2 below (for crossing only).

3.1.3 below and satisfies the conditions given in Clause 3.3.1 and

3.3.2 below (for crossing only).

Conditions                           Limits

Continuous Voltage             12 V

Continuous Current             10 mA

Vtouch

= 116 + (0.17r)

Where:

r = Surface soil resistivity in ohms-meters

t = Fault duration in seconds. This shall be taken as 0.5 seconds or backup clearing time whichever is higher.

Therefore, for 500 ohm-meter top soil resistivity and 0.5 second fault clearing time, the safe touch voltage limit is 284 V.

Following minimum horizontal spacing between the transmission line center and above grade or below grade metallic facility shall be maintained.

Table 09-4: Spacing between Parallel Transmission Lines and Metallic Facility

Line Voltage, kVLength of metallic facility in parallel with transmission line, kmMinimum horizontal spacing, m
230 and belowless than 1.640
380less than 1.650
69 – 380more than 1.6150

In case of spacing less than that given above, induced voltage study shall be performed to verify the requirements of Clause 3.1.2 & 3.1.3 and case shall be referred to National Grid Saudi Arabia for review / and approval.

If angle is within the limits, no induced voltage study is required. However, in cases where the angle requirement cannot be met, induced voltage study shall be performed to verify the requirements of Clause 3.1.2 & 3.1.3. If the induced voltages are within the allowable limits, no further action is required other than to meet the minimum spacing requirements per Table 09-4 above. In case, the induced voltages are not within the limits, appropriate mitigation measures shall be adopted and submitted to National Grid Saudi Arabia for review and acceptance.

3.2 above. If the metallic facility is crossing below the grade and changing its direction at a distance less than 150 meters from crossing, the facility shall be grounded at the point where the direction is changing.

If the metallic facility is crossing above the grade, the facility shall be grounded up to 100 meters along the length of the facility in both directions from the crossing point. If the facility is changing its direction at a distance greater than 100 meters but less than 150 meters from the crossing point, additional grounding shall be provided at the point where the direction is changing. The grounding of the metallic facility shall be to the satisfaction of the concerned party.

Following minimum horizontal spacing between center of 69kV to 380kV transmission lines and edge of main oil facilities shall be provided for safe operation and maintenance of both.

Table 09-5: Spacing between Transmission Lines and Main Oil Facilities

Oil FacilitySpacing, m
Oil & Gas Wells and GOSPs200
Oil Trunk / Burn Pits and Ground Flares150
Elevated Flare Stacks, Oil-Water Separators and Skimming Ponds, Oil Process Areas, Gasoline Stations, Chemical & Pressure Storage Vessels, Booster & Shipping Pump area / LPG Rack, Low and High Flash Stocks etc.  60

Conductors attached to fixed supports shall have horizontal clearances from each other not less than the larger value required by equations given below:

  1. Conductors of the Same Circuit
  1. H = 300+10 (U-8.7)                                                                (Eq.09-1)
    1. F = 7.6 (U) +8                                                                (Eq.09-2)
  2. Conductors of Different Circuits
    1. H = 715+10 (Uo-50)                                                                (Eq.09-3)
    1. F = 7.6 (Uo) + 8                                                                (Eq.09-4)

Where:

H = Basic horizontal clearance between conductors in mm.

F = horizontal clearance due to sag between conductors in mm. U = maximum operating voltage phase to phase over 8.7 kV

Uo= Maximum operating voltage between line conductors of different circuits which shall be the greater of the phasor difference between the conductor involved, or the phase-to-ground voltage of the higher voltage circuit. For circuits having the same phases and nominal voltage, either circuit may be considered to be the higher voltage circuit.

S = Final unloaded sag based on computed ruling span at every day conductor temperature, no wind, in mm.

A margin of 0.6m shall be added to the calculated values to account for design errors.

The clearances shall be increased @ 3 % for each 300m in excess of 1,000m altitude above mean sea level.

Where suspension insulators are used and are not restrained from movement, the clearance shall be increased so that one string of insulators may swing transversely through a range of insulator swing up to its maximum design swing angle without reducing the values given in equations 09-1 to 09-4 and 09-11 to 09-20. The maximum design swing angle shall be based on wind pressure to be calculated corresponding to a wind speed of 140km/h explained:

Wind speed of 170km/h as specified for the design of structures is a 3-second gust wind associated with 50 years return period at 10 meter height above ground in flat and open country terrain (Exposure Category “C” defined as open terrain with scattered obstructions having heights generally less than

9.1m per ASCE Manual # 74 “Guidelines for Electrical Transmission Line

Structural Loading” third edition-2009). However, gust winds of short duration (such as 3-second) will neither affect the swing angles nor the force acting on the structures (CIGRE Technical Brochure 348-2008). Only sustained winds (averaged over sufficiently long period of time such as 1- minute) can affect the swing angle and produce offset of the conductor sag. Based on gust wind speed of 170km/h, sustained wind corresponding to 1- minute average time is estimated 140km/h with resulting wind pressure of 927 N/m2. This shall be used to determine swing angle and right of way requirements.

  1. The insulator swing shall be calculated as follows:

For maximum angle of swing:

ê  
ú  

f = Arc Tané 2T Sin (q/2)+ (HS x Pc )ù

(Eq.09-5)

ë     (VS x Wc )+ Wi /2     û

For minimum angle of swing:

f =  

é2T Sin (q / 2) – (HS x Pc )ù

Arc Tan

(Eq.09-6)

ê      (VS x W ) + W / 2      ú

ë

Where

c                i                   û

f = angle with the vertical through which the insulator string swings

q = line angle in degrees

T = conductor tension at the temperature and wind loading for which the clearance is specified, in Newton

HS = horizontal span, which is 1/2 the sum of adjacent spans, in meters VS = vertical span, which is the distance between the low point of sag

in adjacent spans, in meters

Pc = wind load per unit length of conductor (conductor diameter times wind pressure), in Newton/meter

Wc = weight per unit length of bare conductor, in Newton/meter

Wi = weight of insulator string divided by number of conductors per phase, in Newton

Where: f is the maximum swing angle calculated per equation 09-5.

  1. The clearances specified in equations 09-1 to 09-4 and equations 09-5 and 09-6 may be reduced for circuits with known switching surge factors but shall not be less than the clearances derived from the equation below:

éU      (SSF)a ù1.667

Min. clearance (H) =1000ê  L-L                     ú       ´ b

(Eq.09-7)

ë      500k       û

Where:

UL-L = Maximum alternating current crest operating voltage between different circuits. If the voltages are of the same phasor and magnitude, one conductor shall be considered grounded.

SSF = Maximum switching surge factor expressed in per unit peak operating voltage between different circuit. (SSF value shall be obtained from Transmission Asset Planning Department).

a = 1.15, the allowance for three standard deviations

b = 1.03, the allowance for nonstandard atmospheric conditions. k = 1.4, the configuration factor for a conductor-to-conductor gap

The clearance shall be increased @ 3 % for each 300m in excess of 450m above mean sea level.

All conductors located at different levels on the same supporting structure of the same or different circuits for the same sag, shall have vertical clearances not less than required by the equations given below:

  1. Vs = 830+10 (U-50)                                                                            (Eq.09-8)

Where:

Vs = Basic vertical clearance phase-to-phase, in mm

U = Maximum operating voltage phase-to-phase, over 50 kV

Table 09-6: Vertical Clearances between Line Conductors for same Circuit on the same Structure

Line Voltage, kVVertical Clearance between Phases of the same Circuit on the same Structure, m
691.10
110/1151.60
1321.80
2302.90
3804.60

Notes to Table 09-6:

  1. A margin of 0.15m shall be added to account for design errors.
    1. The clearances at the supporting structures shall be increased to compensate the reduction in span clearances caused by jumping of conductors in the longer spans.
      1. The clearances shall be increased @ 3 % for each 300m in excess of 1,000m altitude above mean sea level.
  1. Vc = 830+10[(U01+U02)-50]                                                                            (Eq.09-9)

Where:

Vc = Basic vertical clearance between circuits in mm

U01 = Maximum phase-to-ground voltage of circuit at upper level, over 50 kV

U02 = Maximum phase to ground voltage of circuit at lower level, over 50 kV

When the circuits have the same nominal voltage, either circuit may be considered to be the higher voltage circuit.

Table 09-7: Vertical Clearance between different Circuits on the same Structure for different Voltages

Nominal Circuit Voltages, kVVertical Clearance between different circuits on the same structure, m
69/691.20
110/1101.75
115/1151.80
132/1322.0
230/2303.25
380/3805.15

Notes to Table 09-7:

  1. A margin of 0.15m shall be added to account for design errors.
    1. The clearances at the supporting structure shall be so adjusted that the clearances at any point in the span shall not be less than the values given in the table when measured with upper conductor at final unloaded sag at the maximum temperature for which the conductor is designed to operate and the lower conductor at final unloaded sag under the same ambient conditions and without electrical loading.
      1. The clearances shall be increased @ 3 % for each 300m in excess of 1,000m altitude above mean sea level.

The clearances specified in equations 09-8 and 09-9 may be reduced for circuits with known switching surge factors, but shall not be less than the clearances required by the equation below:

é(U (SSF) + U )aù1.667

Min. Clearance (V) = 1000ê

ë

H                            L

500k

ú       ´ bc

û

(Eq.09-10)

Where:

UH = Higher voltage circuit maximum crest operating voltage to ground UL = Lower voltage circuit maximum crest operating voltage to ground

SSF = Higher voltage circuit maximum switching surge factor expressed in per-unit peak voltage to ground. (SSF value shall be obtained from Transmission Asset Planning Department).

a = 1.15, the allowance for three standard deviations

b = 1.03, the allowance for nonstandard atmospheric conditions.

c = 1.2, the margin safety

k = 1.4, the configuration factor for conductor-to-conductor gap

The clearance shall be increased @ 3 % for each 300m in excess of 450m above mean sea level.

Clearance ‘T’ = 330mm+5mm (U-50)                                                                                (Eq.09-11) Where, U = Maximum operating voltage phase-to-phase, over 50kV

Minimum clearances of conductor to its own supporting structure were calculated based on the above equation and tabulated below:

Table 09-8: Clearance of Conductor to its own Support

  Line Voltage, kVClearance of Conductor from its own Support Arm and Structure, m
No WindMaximum Wind
690.690.45
110/1151.300.60
1321.500.65
2302.100.85
3803.501.30

Notes to Table 09-8:

  1. For clearances under no wind condition, a margin of 0.15m shall be added to account for design errors.
  2. The clearances under maximum wind shall be maintained when the insulator strings and conductors swing transversely up to maximum design swing angle.
  3. The clearances under no wind condition shall be increased @ 3 % for each 300m in excess of 1,000m altitude above mean sea level.

The clearances specified in Eq.09-11 may be reduced for circuits with known switching surge factor but shall not be less than the clearances derived from the equation shown below:

éU      (SSF)aù1.667

Min. Clearance (T) = 1000ê  L-G                     ú       ´ b

(Eq.09-12)

ë      500k       û

Where:

UL-G = Maximum alternating current crest operating voltage to ground

SSF = Maximum switching surge factor expressed in per-unit peak voltage to ground

a = 1.15, the allowance for three standard deviations with fixed insulator supports

a = 1.05, the allowance for one standard deviation with free swinging insulators

b = 1.03, the allowance for nonstandard atmospheric conditions k = 1.2, the configuration factor for conductor-to-tower window

The clearance shall be increased @ 3 % for each 300m in excess of 450m above mean sea level.

8. The maximum insulator swing angle shall be determined as outlined in equation 09-5.

  1. Basic Clearance

The horizontal clearance between adjacent conductors carried out on different supporting structures shall not be less than required by the equation below:

Clearance = 1500mm+10mm [(U01+U02)-22]                                                                            (Eq.09-13)

Where:

U01 = Maximum Phase-to-Ground Voltage in kV of Line #1 U02 = Maximum Phase-to-Ground Voltage in kV of Line #2

The clearance shall be maintained when one insulator string swings up to its extreme position while the string of adjacent conductors remains at rest.

A margin of 0.6m shall be added to the calculated values to account for design errors.

The clearance shall be increased @ 3 % for each 300m in excess of 1,000m above mean sea level.

The clearances specified in equation 09-13 may be reduced for circuits with known switching surge factor but shall not be less than the clearances derived from the equation 09-7.

  1. Basic Clearance

The vertical clearance between any crossing or adjacent conductors carried on different supporting structures of the same or different nominal voltages shall not be less than that shown in Table 09-9 or as required by the following equation, whichever is larger.

Clearance = 600mm+10 [(U01-22)+(U02-22)]                                                                            (Eq.09-14)

Where:

U01 = Maximum phase-to-ground voltage of Line at upper level, over 22 kV

U02 = Maximum phase-to-ground voltage of Line at lower level, over 22 kV

Table 09-9: Minimum Vertical Clearance between Conductors where the Conductors of one Line cross over the Conductors of another

Lower Level ConductorUpper Level Conductor
  Type of CrossingTransmission Voltages (Line to Line)
69kV (m)110kV (m)115kV (m)132kV (m)230kV (m)380kV (m)
69kV Transmission Lines1.10–1.40–2.103.10
110kV Transmission Lines–1.60–––3.30
115kV Transmission Lines1.40–1.70–2.403.40
132kV Transmission Lines–––1.90–3.50
230kV Transmission Lines2.10–2.40–3.204.10
380kV Transmission Lines3.103.303.403.504.105.10
Distribution Lines (34.5kV and below) / Electrified Railroads contact wires0.901.201.301.402.053.02
Overhead Ground Wire/ OPGW/Guys/Span Wires1.401.701.701.802.503.40
Communication Lines2.02.202.302.503.104.10

Notes to Table 09-9:

  1. Additional margins of 1.0 m and 2.0 m (total 3.0 m) shall be added to account for design errors and wind induced dynamic conductor movement/safety during maintenance operations respectively. The above mentioned margin of 2.0 m may be reduced to 1.0 m if the cross-over is quite away from the mid-points of the spans thereby limiting the conductor movement.
  2. The clearances shall be maintained under the conditions, when upper level conductors are at the final unloaded sag at maximum design temperature of conductor and lower level conductors are at the initial sag at the minimum design temperature of conductor or at final unloaded sag under the same ambient condition without electrical loading whichever results in larger difference.
  3. The clearances shall be increased @ 3 % for each 300m in excess of 1,000m altitude above mean sea level.

The clearances specified in equation. 09-14 may be reduced where the higher voltage circuit has a known switching surge factor but shall not be less than the clearances derived from the equation 09-10.

Conductors of one line passing near a lighting support, traffic signal support, or a supporting structure of a second line, without being attached thereto, shall have clearance from any part of the structure not less than calculated by the equation below:

Where U0 is the maximum operating voltage phase-to-ground, in excess of 50kV.

Minimum horizontal clearance of a line conductor to a rigid supporting structure, other than its own, based on the above equation was calculated and tabulated in Table 09-10.

Table 09-10: Horizontal Clearance      of                                  Conductor from other Supporting Structure

Nominal Voltage (kV)Minimum Horizontal Clearance of Conductor from other Supporting Structure, m
691.50
110/1151.75
1321.85
2302.50
3803.50

Note: A margin of 0.6m shall be added to account for design errors and the clearances shall be increased @ 3 % for each 300m in excess of 1,000m altitude above mean sea level.

  1. The maximum insulator swing angle can be determined by equation 09-5.
  1. The maximum design swing angle shall be based on a 927 N/m2 wind on the conductor, final sag at every day temperature. The conductor swing shall be calculated as follows:

f = Arc Tan (Pc/Wc)                                                    (Eq.09-16) Where: Pc and Wc are defined in equation 09-6.

The horizontal swing of conductors due to wind can be obtained from the equation:

C = Sc x sin f                                                                (Eq.09-17)

Where: Sc is the conductor sag, which shall be final sag based on computed ruling span at every day temperature, with 927 N/m2 wind.

Min. Clearance = 1700 mm + 10 mm (U0-50)                                                                                     (Eq.09-18)

Where: U0 = Maximum operating Voltage Phase-to-Ground, in excess of 50kV.

Minimum vertical clearance of a line conductor to a rigid supporting structure, other than its own, was calculated based on the above equation and given in Table 09-11.

Table 09-11: Vertical Clearance of Conductor from other Supporting Structure

Nominal Voltage, kVMinimum Vertical Clearance of Conductor from other Supporting Structure, m
691.70
110/1151.95
1322.05
2302.70
3803.70

Note: A margin of 1.0m shall be added to account for design errors and the clearances shall be increased @ 3 % for each 300m in excess of 1,000m altitude above mean sea level.

The clearances specified in equations 09-15 and 09-18 may be reduced for

circuits with known switching surge factors but shall not be less than the values derived from the following equations.

  1. Min. horizontal clearance in mm

é U      (SSF)aù1.667

= 1500 + 1000ê

ë

L-G

500k

ú       ´ bc

û

(Eq.09-19)

é U      (SSF)aù1.667

= 1800 + 1000ê

ë

L-G

500k

ú       ´ bc

û

(Eq.09-20)

Where:

UL-G = The maximum crest operating voltage to ground

SSF = Maximum switching surge factor expressed in per-unit peak voltage to ground (SSF value shall be obtained from Transmission Asset Planning Department).

a = 1.15, the allowance for three standard deviations

b = 1.03, the allowance for nonstandard atmospheric conditions

c = Margin of safety, 1.2 for Vertical clearances and 1.0 for horizontal clearances

k = 1.15, the configuration factor for Conductor-to-Plane gap

The clearances shall be increased @ 3 % for each 300m in excess of 450m above mean sea level.

The horizontal and vertical clearances of line conductors from other structures such as tall buildings, signs, chimneys, TV masts, lighting poles, monuments in the round- about etc., shall be established as required, taking into consideration all local conditions and the latest government and owner regulations.

Minimum clearances of wires, conductors and cables passing by, but not attached to building and other installations, shall not be less than those given in the following table. The horizontal clearance mentioned in the table shall be maintained when the conductor swings up to the design swing angle.

Table 09-12: Minimum Clearance of Conductors Adjacent to but not attached to Buildings and other Installations except Bridges (see notes 5, 6 and 7)

  Clearance ofCommunication Cables and Grounded GuysConductors Voltage, kV
69110- 132230380
Buildings (Horizontal Clearance) m
To wall and projections (Note 3)1.402.552.953.64.55
To unguarded windows (Note 4)1.402.552.953.64.55
To balconies and areas accessible to pedestrians (Note 1)1.402.552.953.64.55
Buildings (Vertical Clearance) m
Above or below roof or projection not accessible to pedestrians (Note 1)0.904.054.505.106.10
Above or below balconies and roofs accessible to pedestrians (Note 1)3.204.354.805.406.35
Above roofs accessible to vehicles but not subject to truck traffic3.204.354.805.406.35
Above roofs accessible to truck traffic (Note 2)4.705.856.306.907.85
Signs, Chimneys, radio and television antennas, lighting poles, monuments in the round-about tanks and other installations not classified as buildings m
Horizontal0.902.552.953.64.55
Vertical above or below0.902.703.103.704.70

Notes to Table 09-12:

  1. A roof, balcony or area is considered accessible to pedestrians if the means of access is through a doorway, ramp, stairway or permanently mounted ladder.
  2. For the purpose of this rule, trucks are defined as any vehicle exceeding 2.45 m in height.
  3. This clearance may be reduced to 75 mm for the grounded portions of guys.
  4. Windows not designed to open may have the clearances permitted for walls and projections.
  5. A margin of 1.0 m shall be added to account for design errors.
  6. The clearances shall be increased @ 3 % for each 300 m in excess of 1,000 m altitude above mean sea level.
  7. As a general practice, buildings and other installations are not permitted within the transmission line ROW. The clearances mentioned here are under exceptional cases when these cannot be removed. Under such cases it shall be ensured that no part of the buildings is exposed to electric fields in excess of 5kV/m (IEEE Standard C95.6) including outer walls, balconies and roofs.

The clearance specified in Table 09-12 may be reduced for circuit with known switching surge factors but shall not be less than the values derived from equations 09-19 and 09-20.

The separation between the overhead ground wire and the top conductor is a function

of the actual structure footing resistance, wind speed, the number of insulators in the insulator string, type of insulator, the span length and the acceptable number of outages per 100 km per year.

Table 09-13: Mid-Span Clearance between Conductors and OGW/OPGW

Span, mMid-Span Clearance (between conductors and OGW/OPGW), m
91 – 2133.5
2444.5
3056.0
3506.8
3667.0
4007.8
4278.5
4509.1

Note: Applicable for all altitude levels.

To maintain adequate clearances the air gap distance between any conductor and structure shall be correlated to the insulation levels considering each of the three types of voltage stresses (lightning impulse, switching surge and power frequency) under the condition at which each is likely to govern and given in the following table.

Table 09-14: Air Gap Requirement for Shielded Lines

Line Voltage, (kV)Air Gap, (m)
690.69
110/1151.30
1321.50
2302.1
3802.60

Note: The clearances shall be increased @ 3 % for each 300m in excess of 1,000m altitude above mean sea level.

For unshielded lines the following criteria shall be used to specify clearances of conductor to structure. Further the minimum conductor to structure and conductor to conductor clearances shall not be less than Eq. 09-1 to Eq. 09- 20 or by the correlated air gap clearances to insulation levels, the larger value shall be used, for various situations. Basic clearances shall be based on the maximum system voltage under emergency conditions.

  1. For the “no wind” or normal position of the insulator, the conductor clearance to structure shall be the air gap equivalent of the insulator string impulse flashover value plus ten (10) percent.
    1. For the 430 N/m2 wind position, the conductor clearance to structure shall be the air gap equivalent of the insulator string impulse flashover value.

Transmission line Right-of-Way is a strip of land that is used to construct, operate, maintain and repair transmission line facilities. The line is normally centered in the right-of-way.

  1. Basic Clearance

= 2300 mm + 10 mm (U0-22)                                                                            (Eq.09-21)

Where:

U0 = Maximum operating voltage phase-to-ground over 22 kV.

A = Distance from centerline of structure to insulator attachment in mm.

f1 = Angle of maximum swing for suspension insulator string. It is preferred to use the f1 as 45° swing.

If 45° swing is used, it will include most conditions for structures currently being used with the insulator string at maximum blowout or structure design limitations.

If the minimum right-of-way is required to be obtained for a special area control then the actual conditions or f1 may be calculated for the worst conditions of the line under consideration.

B = Offset due to insulator swing for suspension insulators equal to length of insulator string plus hardware length times Sin f1

f2 = Angle of maximum swing for conductors is determined by multiplying the conductor diameter in meters by the wind pressure in N/m2 on conductor and dividing by the conductor unit weight in Newton per meter.

Tan f = Conductor Dia x Wind Pressure

(Eq.09-22) TES-P-122.09

2                     Unit Weight

C = Offset due to conductor sag x Sin f2. Conductor sag shall be the final sag based on computed ruling span at every day temperature with 927 N/m2 wind

D = Horizontal clearance from conductor to edge of right-of-way at maximum swing calculated for conditions established for structure to be used (see Clause 6.2.2)

E = Total distance each side, from centerline to edge of right-of-way.

The horizontal clearance between conductor of one line to conductor of another line shall meet the following conditions: (a) both conductors displaced by a 927 N/m2 wind at every day temperature, final sag; (b) if insulators are free to swing, one shall be assumed to be displaced by a 927 N/m2 wind while the other shall be assumed to be unaffected by the wind (see Figure TE-2209-0300-01).

F = Clearance between conductors of parallel transmission lines as determined by equation 09-3 and 09-4 for phases of different circuits.

The horizontal clearance of a conductor of one line to the supporting structure of another when the conductor and insulator are displaced by a 927 N/m2 wind at every day temperature final sag.

G = Clearance of conductor from other supporting structures, as determined by the equation 09-15.

  1. Dimension ‘A’

A ≃ 7.60 m derived from the drawing for “Latticed Steel Vertical Configuration 380kV Double Circuit Suspension (Tangent) Type Tower S1N. Dimension ‘A’ depends on tower structure design and configuration.

Assume f1 = 45° for I-Strings

f1 = 0° for V-Strings (no deflection)

Length of Insulator String (including hardware) = 7.5 m B = Length of Insulator String x Sin f1

= 7.5 m x sin 0 = 0 m (for V-String case)

Angle of maximum swing for conductors:

f2 = Arc Tan æ 27.72 mm /1000 x 927

ö = 60.86 ° say 610

è  
ø  

ç            14.32 N/m            ÷

Sag for 400m ruling span ≃ 13m at 25°C, final with 927 N/m2 wind Offset due to conductor swing:

C = 13 m x sin 610 = 11.37 say 11.40m

Offset due to conductor swing for bundled conductor:

Cl = 11.40 m + 0.45 x Cos 61∘ = 11.50 m

2

Horizontal clearance to edge of right-of-way

D = 2300mm +10mmæ 418 – 22ö

ç               ÷

è               ø

D     = 2,300 mm + 2,193 mm = 4,493 mm, say 4.50m

Distance each side of centerline to edge of right-of-way

E = A+ B+ C+ D = 7.60 + 0 + 11.50+ 4.5 = 23.60, say 24 m

Therefore, total width of right-of-way required shall be: 2 x E = 2 x 24 m = 48 m, say 50 m

To keep margin for variation in sag and cross arm structure configuration etc., 50m width is standardized for 380kV.

Tower configurations are the same as in clause 6.5.2. The separation between two parallel 380kV steel tower lines shall be calculated by the two equations shown below and greater value shall be considered:

Items A, B, C, D, and E to be calculated as in clause 6.5.2

  1. Horizontal Clearance between different phases of different circuits according to conductor sag per equation 09-3 & 09-4

F = 7.6mmé U1 + U2 ù + 8

Where:

U1 = U2 = 380kV x 1.1 = 418kV

S = Sag at 25°C, final with 927 N/m2 wind F = 7.6mm [242 + 242]+ 8

= 3,678 + 1,328 =5,006 mm, say 5.0 m

G = 1500mm +10æ U1 – 50ö

ç              ÷

è              ø

= 1500 + 10(242 – 50)

= 1500 + 1920 = 3,420 mm, say 3.5m

F = 5m is larger than G, therefore, it is to be considered

Total right-of-way width shall be: E + A + B + C + F + A3 + E

= 23.60+7.60+0+11.50+5.0+13.70+ 23.60= 85 m

Table 09-15: Sample Data for Right-Of-Way Calculation

Sr. No.DescriptionCircuit No. 1 & 2
1Maximum Line Voltage380kV
2Type of StructureLattice Steel (vertical configuration)
3Drawing for Tower Type S1NET-905431
4Distance, tower center to V-String center, m7.60
5Number of Insulators in V-String46 X 2
6Insulator String length (including hardware), m7.5
7ConductorACSR/AW Condor
8Stranding54/7
9Weight per unit, kg/m1.461
10Diameter, mm27.72
11Ruling span, m400
12Sag at 25° with 927 N/m2 wind, m13.0 (approximate)

Table 09-16: Single Transmission Lines Right-of-Way Width Requirements

Line Voltage, (kV)StructureConductorRuling Span, mNormal ROW Width, m
    380Lattice Steel Towers, D/C (Vertical, V-String)                    ACSR/AW Condor40050
Lattice Steel Towers, D/C (Vertical, I-String)40050*
Lattice Steel Towers, S/C (Horizontal, V-String)40056
    230Lattice Steel Towers, D/C (Vertical, I-String)35044
Lattice Steel Towers, D/C (Delta, I-String)35057
Steel Monopole, D/C (Vertical, I-String))20032
    110/115/132Lattice Steel Towers, D/C (Vertical, I-String)35034
Lattice Steel Towers, D/C (Delta, I-String)35042
Steel Monopole, D/C (Vertical, I-String))20025
  69Lattice Steel Towers, D/C (Vertical, I-String)30028
Steel Monopole, D/C (Vertical, I-String))20020

Notes to Table 09-16:

  1. ROW marked with * applicable in the Inland Area for existing transmission lines where creepage distance is 31mm/kV
  2. ROW values indicated in the above table are based on some specific structures and their cross-arm configurations and may increase/decrease with respect to distance between center of structure and center of insulator string.
  3. For transmission lines located in the median of the roads, existing ROW of the roads shall be applicable. Specified conductor clearances over road surface, to buildings and other installations at the edge of right of way shall be maintained and structures shall be protected with crash barriers.
  4. ROW calculations are based on ACSR/AW Condor conductor. For other conductors the values shall be established based on the actual span length and the conductor data.

Table 09-17: Parallel Transmission Lines Right-of-Way Width Requirements

Line Voltage, (kV)StructureConductorRuling Span, mLine Center to Center, mNormal ROW Width, m
  380Lattice Steel Towers, D/C (Vertical, V-String)                                              ACSR/AW Condor  400  37  85
Lattice Steel Towers, D/C (Vertical, V-String)
  380Lattice Steel Towers, D/C (Vertical, I-String)  400  39  96*
Lattice Steel Towers, D/C (Vertical, I-String)
  380Lattice Steel Towers, S/C (Horizontal, V-String)  400  45  100
Lattice Steel Towers, S/C (Horizontal, V-String)
  380Lattice Steel Towers, D/C (Vertical, V-String)  400  40  92
Lattice Steel Towers, S/C (Horizontal, V-String)
  380/230Lattice Steel Towers, D/C (Vertical, V-String)400  30  75
Lattice Steel Towers, D/C (Vertical, I-String)350
  380/230Lattice Steel Towers, D/C (Vertical, V-String)400  36  88
Lattice Steel Towers, D/C (Delta, I-String)350
  380/230Lattice Steel Towers, D/C (Vertical, V-String)400  28  68
Steel Monopole, D/C (Vertical, I-String)200
  380/230Lattice Steel Towers, S/C (Horizontal, V-String)400  34  84
Lattice Steel Towers, D/C (Vertical, I-String)350
  380/132Lattice Steel Towers, D/C (Vertical, V-String)400  26  66
Lattice Steel Towers, D/C (Vertical, I-String)350
  380/115Lattice Steel Towers, D/C (Vertical, V-String)400  28  70
Lattice Steel Towers, D/C (Vertical, I-String)350
  380/115Lattice Steel Towers, D/C (Vertical, V-String)400  30  74
Lattice Steel Towers, D/C (Delta, I-String)350
  380/69Lattice Steel Towers, D/C (Vertical, V-String)400  26  63
Lattice Steel Towers, D/C (Vertical, I-String)300

* Applicable in the Inland Area for existing transmission lines where creepage distance is 31mm/kV.

Table 09-17: Parallel Transmission Lines Right-of-Way Width Requirements (Continued)

Line Voltage, (kV)StructureConductorRuling Span, mLine Center to Center, mNormal ROW Width, m
  380/69Lattice Steel Towers, D/C (Vertical, V-String)                                                  ACSR/AW Condor400  25  58
Steel Monopole, D/C (Vertical, I-String)200
  380/69Lattice Steel Towers, S/C (Horizontal, V-String)400  30  71
Lattice Steel Towers, D/C (Vertical, I-String)300
  380/69Lattice Steel Towers, S/C (Horizontal, V-String)400  30  67
Steel Monopole, D/C (Vertical, I-String)200
  230Lattice Steel Towers, D/C (Vertical, I-String)  350  28  72
Lattice Steel Towers, D/C (Vertical, I-String)
  230Lattice Steel Towers, D/C (Delta, I-String)  350  41  98
Lattice Steel Towers, D/C (Delta, I-String)
  230Steel Monopole, D/C (Vertical, I-String)  350  21  53
Steel Monopole, D/C (Vertical, I-String)
  230Lattice Steel Towers, D/C (Vertical, I-String)  350  34  85
Lattice Steel Towers, D/C (Delta, I-String)
  230Lattice Steel Towers, D/C (Vertical, I-String)350  27  65
Steel Monopole, D/C (Vertical, I-String)200
  230Lattice Steel Towers, D/C (Delta, I-String)350  34  78
Steel Monopole, D/C (Vertical, I-String)200
  230/132Lattice Steel Towers, D/C (Vertical, I-String)350  25  64
Lattice Steel Towers, D/C (Vertical, I-String)350
  230/115Lattice Steel Towers, D/C (Vertical, I-String)350  25  60
Steel Monopole, D/C (Vertical, I-String)200
  230/115Lattice Steel Towers, D/C (Delta, I-String)  350  35  84
Lattice Steel Towers, D/C (Delta, I-String)
  230/115Lattice Steel Towers, D/C (Delta, I-String)350  32  73
Steel Monopole, D/C (Vertical, I-String)200

Table 09-17: Parallel Transmission Lines Right-of-Way Width Requirements (Continued)

Line Voltage, (kV)StructureConductorRuling Span, mLine Center to Center, mNormal ROW Width, m
  230/115Steel Monopole, D/C (Vertical, I-String)                                  ACSR/AW Condor  200  19  48
Steel Monopole, D/C (Vertical, I-String)
  230/115Lattice Steel Towers, D/C (Vertical, I-String)  350  26  67
Lattice Steel Towers, D/C (Vertical, I-String)
  230/115Lattice Steel Towers, D/C (Delta, I-String)  350  33  80
Lattice Steel Towers, D/C (Vertical, I-String)
  230/115Steel Monopole, D/C (Vertical, I-String)200  20  55
Lattice Steel Towers, D/C (Vertical, I-String)350
  230/69Lattice Steel Towers, D/C (Vertical, I-String)350  24  60
Lattice Steel Towers, D/C (Vertical, I-String)300
  230/69Lattice Steel Towers, D/C (Vertical, I-String)350  24  56
Steel Monopole, D/C (Vertical, I-String)200
  230/69Lattice Steel Towers, D/C (Delta, I-String)350  31  73
Lattice Steel Towers, D/C (Vertical, I-String)300
  230/69Lattice Steel Towers, D/C (Delta, I-String)350  30  69
Steel Monopole, D/C (Vertical, I-String)200
  230/69Steel Monopole, D/C (Vertical, I-String)  200  18  44
Steel Monopole, D/C (Vertical, I-String)

Note: Wherever ROW is restricted and not possible to maintain and accommodate above clearances and/or structure pads/access road per TES-P-122.11, National Grid Saudi Arabia shall review the case to determine appropriate clearances and ROW.

Table 09-17: Parallel Transmission Lines Right-of-Way Width Requirements (Continued)

Line Voltage, (kV)StructureConductorRuling Span, mLine Center to Center, mNormal ROW Width, m
  132Lattice Steel Towers, D/C (Vertical, I-String)                                                  ACSR/AW Condor  350  20  54
Lattice Steel Towers, D/C (Vertical, I-String)
  115Lattice Steel Towers, D/C (Delta, I-String)  350  27  69
Lattice Steel Towers, D/C (Delta, I-String)
  115Lattice Steel Towers, D/C (Vertical, I-String)  350  23  60
Lattice Steel Towers, D/C (Vertical, I-String)
  115Lattice Steel Towers, D/C (Vertical, I-String)  350  25  64
Lattice Steel Towers, D/C (Delta, I-String)
  132/69Lattice Steel Towers, D/C (Vertical, I-String)350  19  50
Lattice Steel Towers, D/C (Vertical, I-String)300
  115/69Lattice Steel Towers, D/C (Vertical, I-String)350  21  53
Lattice Steel Towers, D/C (Vertical, I-String)300
  115/69Lattice Steel Towers, D/C (Vertical, I-String)350  20  49
Steel Monopole, D/C (Vertical, I-String)200
  115/69Lattice Steel Towers, D/C (Delta, I-String)350  23  57
Lattice Steel Towers, D/C (Vertical, I-String)300
  115/69Lattice Steel Towers, D/C (Delta, I-String)350  23  53
Steel Monopole, D/C (Vertical, I-String)200
  115/69Steel Monopole, D/C (Vertical, I-String)  200  14  37
Steel Monopole, D/C (Vertical, I-String)
  69Lattice Steel Towers, D/C (Vertical, I-String)  300  16  43
Lattice Steel Towers, D/C (Vertical, I-String)
  69Steel Monopole, D/C (Vertical, I-String)  200  12  31
Steel Monopole, D/C (Vertical, I-String)
  69Lattice Steel Towers, D/C (Vertical, I-String)300  15  39
Steel Monopole, D/C (Vertical, I-String)200

Table 09-18: Wood Poles Transmission Lines Right-of-Way Width Requirements

Line Voltage, (kV)StructureConductorRuling Span, mMaximum Span, mNormal ROW Width, m
Single Transmission Lines Right of Way Width Requirements
  115Wood Monopole, H-Frame, S/C    ACSR/AW260-27532030
Wood Monopole, S/C & D/C80-100110-12015
  69Wood Monopole, H-Frame, S/C260-27532025
Wood Monopole, S/C & D/C80-12014015
Parallel Transmission Lines Right of Way Width Requirements
  115H-Frame Wood, S/C                                ACSR/AW260-275320  60
H-Frame Wood, S/C260-275320
  115H-Frame Wood, S/C260-275320  38
Wood Pole, S/C80-100110-120
  115Wood Pole, S/C80-100110-120  23
Wood Pole, S/C80-100110-120
  115/69H-Frame Wood, S/C260-275320  45
H-Frame Wood, S/C260-275320
  115/69H-Frame Wood, S/C260-275320  37
Wood Pole, S/C80-100110-120
  115/69Wood Pole, S/C80-100110-120  21
Wood Pole, S/C80-100110-120
  69H-Frame Wood, S/C260-275320  42
H-Frame Wood, S/C260-275320
  69H-Frame Wood, S/C260-275320  23
Wood Pole, S/C80-100110-120
  69Wood Pole, S/C80-100110-120  20
Wood Pole, S/C80-100110-120

Note: Wherever ROW is restricted and not possible to maintain and accommodate above clearances and/or structure pads/access road per TES-P-122.11, National Grid Saudi Arabia shall review the case to determine appropriate clearances and ROW.

The minimum horizontal distance between the route center line and other parallel transmission lines, telecommunication lines or other obstacles such as buildings, trees etc. shall not be less than that given in Table 09-19.

Table 09-19: Horizontal Distance between other Parallel Transmission Lines and other Obstacles

  Transmission Line/ Obstacles etc.Distance (in meters) of selected line route to objects for:
380kV230kV132/115/110kVBelow 110kV
380kV50404040
230kV40404040
132/115/110kV40404025
Below 110kV40404020
Telecommunication Lines40402520
Buildings, Trees etc.35252520
Renewable Energy Source: 
Wind Farms3 times the rotor diameter of wind turbine
Solar Farms (Note 2)100

Notes to Table 09-19:

  1. The distances mentioned in the above table shall generally be applicable when the transmission line route is passing through un-restricted areas. However, in restricted areas when it is not possible to maintain these distances, lesser values per Table 09-17 may be applied.
  2. National Grid Saudi Arabia shall review the case to determine the appropriate spacing.

U.S. Department of Agriculture, 2015 Edition

H. Farr

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