2 Normative references, definitions and symbols 2.1 Normative references A-dev ES.1 National normative regulations Royal Decree RD 223/2008, of 15th February 2008, approving the Regul
General
This NNA is applicable to any new line between two points, A and B, its modifications and extensions.
Field of application
(A-dev) ES.1 RD 223/2008, ITC-LAT 08, sub-clause 6.3.2
The design and construction of overhead lines with covered conductors and voltages greater than
45 kV shall respect the same electrical clearances as of overhead lines with bare conductors of the same voltage
2 Normative references, definitions and symbols
Normative references
(A-dev) ES.1 National normative regulations
Royal Decree (RD) 223/2008, of 15th February 2008, approving the Regulation on technical and safety conditions for high voltage electrical lines and its Supplementary Technical Instructions ITC-
Royal Decree (RD) 337/2014, of 9th May 2014, approving the Regulation on technical and safety conditions for high voltage power installations and its Supplementary Technical Instructions ITC-
Royal Decree (RD) 614/2001, of 8th June 2001, establishing the minimum health and safety requirements for the protection of workers against the electrical risk
Royal Decree (RD) 1955/2000, of 1st December 2000, regulating the activities of transmission, distribution, marketing and supply of electrical energy and the procedures for the authorization of installations
(ncpt) ES.2 National normative standards
UNE 207016 “HV and HVH type concrete poles for overhead electrical lines”
UNE 207017 “Lattice steel towers for distribution overhead electrical lines”
UNE 207018 “Plate metallic supports for overhead electrical lines”
Symbols
(ncpt) ES.1 Additional symbols asom minimum insulator set discharge gap, defined as shortest distance in straight line between live parts and earthed parts
AT wind exposed pole area projected in a wind direction perpendicular plane in m 2
CS minimum security factor defined for each element and load case
D clearance between same or different circuits’ phase conductors in metres
F maximum sag in metres, for load cases defined in sub-clause 3.2.3
K coefficient depending on the conductors’ wind oscillation, it shall be selected from Table
5.8/ES.1 K’ coefficient depending on overhead lines nominal voltage K’ = 0,85 for special category lines and K’ = 0,75 for other overhead lines
L suspension set length in metres For conductors attached to the pole with strain or post- insulator sets L = 0
VV reference wind velocity in km/h
Requirements of overhead lines
Reliability requirements
In emergency situations involving private overhead lines, a licensed technician, authorized by the line's owner, may implement provisional measures It is essential for the technician to promptly notify the relevant administrative body, which will then determine the timeline for restoring compliance with regulatory standards.
The minimum reliability level shall be 1 Actions for wind and ice are defined in section 4.
Strength coordination
Strength coordination is obtained by matching the security factors (CS) associated to each component and system of the overhead line.
Design values
Design value of an action
(A-dev) ES.1 Design value of an action
Actions shall not be affected by partial factors.
Design value of a material property
(A-dev) ES.1 Partial factor for a material property
The partial factor for a material property shall be:
X d is the design value of the material property
X K is the characteristic value of the material property
CS is the minimum security factor for each element and load case defined in sub-clause
Partial factor method and design formula
Basic design formula
(snc) ES.1 Basic design formula
When considering a limit state of rupture or excessive deformation of a component, element or connection, it shall be verified that:
This NNA is applicable to any new line between two points, A and B, its modifications and extensions
(A-dev) ES.1 RD 223/2008, ITC-LAT 08, sub-clause 6.3.2
The design and construction of overhead lines with covered conductors and voltages greater than
45 kV shall respect the same electrical clearances as of overhead lines with bare conductors of the same voltage
2 Normative references, definitions and symbols
(A-dev) ES.1 National normative regulations
Royal Decree (RD) 223/2008, of 15th February 2008, approving the Regulation on technical and safety conditions for high voltage electrical lines and its Supplementary Technical Instructions ITC-
Royal Decree (RD) 337/2014, of 9th May 2014, approving the Regulation on technical and safety conditions for high voltage power installations and its Supplementary Technical Instructions ITC-
Royal Decree (RD) 614/2001, of 8th June 2001, establishing the minimum health and safety requirements for the protection of workers against the electrical risk
Royal Decree (RD) 1955/2000, of 1st December 2000, regulating the activities of transmission, distribution, marketing and supply of electrical energy and the procedures for the authorization of installations
(ncpt) ES.2 National normative standards
UNE 207016 “HV and HVH type concrete poles for overhead electrical lines”
UNE 207017 “Lattice steel towers for distribution overhead electrical lines”
UNE 207018 “Plate metallic supports for overhead electrical lines”
(ncpt) ES.1 Additional symbols asom minimum insulator set discharge gap, defined as shortest distance in straight line between live parts and earthed parts
AT wind exposed pole area projected in a wind direction perpendicular plane in m 2
CS minimum security factor defined for each element and load case
D clearance between same or different circuits’ phase conductors in metres
F maximum sag in metres, for load cases defined in sub-clause 3.2.3
K coefficient depending on the conductors’ wind oscillation, it shall be selected from Table
5.8/ES.1 K’ coefficient depending on overhead lines nominal voltage K’ = 0,85 for special category lines and K’ = 0,75 for other overhead lines
L suspension set length in metres For conductors attached to the pole with strain or post- insulator sets L = 0
VV reference wind velocity in km/h
3.2 Requirements of overhead lines 3.2.2 Reliability requirements
In emergency situations involving private overhead lines, a qualified licensed technician, with the owner's permission, may implement provisional measures It is essential for the technician to promptly notify the relevant administrative authority, which will then determine the timeline for restoring regulatory compliance.
The minimum reliability level shall be 1 Actions for wind and ice are defined in section 4
Strength coordination is obtained by matching the security factors (CS) associated to each component and system of the overhead line
3.6 Design values 3.6.2 Design value of an action
(A-dev) ES.1 Design value of an action
Actions shall not be affected by partial factors
3.6.3 Design value of a material property
(A-dev) ES.1 Partial factor for a material property
The partial factor for a material property shall be:
X d is the design value of the material property
X K is the characteristic value of the material property
CS is the minimum security factor for each element and load case defined in sub-clause
3.7 Partial factor method and design formula 3.7.2 Basic design formula
(snc) ES.1 Basic design formula
When considering a limit state of rupture or excessive deformation of a component, element or connection, it shall be verified that:
E_d represents the total design value of the effects of actions, including internal forces or moments, or a representative vector of multiple internal forces or moments, as outlined in sub-clause 3.7.2 of the main body.
R d is the corresponding structural design resistance, as defined in sub-clause 3.7.2 of the main body
CS is the minimum security factor for each element and load case defined in clause
Introduction
Due to the lack, in general, of official statistical data, in Spain Approach 3 shall be used to stablish the numerical values of actions.
Permanent loads
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 3.1.1
Vertical loads on account of own weight of each element shall be taken into account: conductors, insulators, fittings, ground wires – if they exist –, poles and foundations.
Wind loads
Field of application and basic wind velocity
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 3.1.2
For wind load calculations, a minimum reference wind velocity of 120 km/h (33.3 m/s) is required, except for transmission lines operating at 220 kV or higher, or for lower voltage lines classified as part of the transmission grid, where the minimum reference wind velocity increases to 140 km/h (38.89 m/s).
This reference wind velocity (VV) shall mean horizontal, acting perpendicular to the areas concerned.
Wind forces on any overhead line component
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 3.1.2.4
In the case of a flat surface, the wind force, QWx, shall be at least:
V V is the reference wind velocity in km/h
A x is the area of the flat surface projected in a perpendicular plane to the wind direction, in m 2
(A-dev) ES.2 RD 223/2008, ITC-LAT 07, sub-clause 3.1.2.5
In the case of a cylindrical surface, the wind force, QWx, shall be, at least:
V V is the reference wind velocity in km/h
A x is the area of the cylindrical surface projected in a perpendicular plane to the wind direction, in m 2
(A-dev) ES.3 RD 223/2008, ITC-LAT 07, sub-clause 3.1.2.1
The wind force over conductors in a suspension pole, in the transversal direction of the line, for each conductor of the bundle shall be, at least, the following:
Where: q p is the wind pressure, with the following value:
The reference wind velocity, denoted as V, is measured in km/h, while d represents the diameter of the conductor or sub-conductor in meters When assessing combined wind and ice loads, it is essential to account for the thickness of the ice, with a recommended reference value of 7.500 N/m³ for the specific volumetric weight of ice.
L 1 , L 2 are the lengths of the adjacent spans, in m
Any possible shade effects between conductors, even in the case of phase bundle conductors, shall be neglected
For the wind forces over poles with angle, the influence of the direction change and the lengths of the adjacent spans shall be taken into account
(A-dev) ES.4 RD 223/2008, ITC-LAT 07, sub-clause 3.1.2.2
The wind forces over the insulator sets shall be taken into account The force value shall be, at least, the following:
V V is the reference wind velocity in km/h
A ins is the area of the insulator set projected horizontally in a vertical plane parallel to the axis of the insulator set
(A-dev) ES.5 RD 223/2008, ITC-LAT 07, sub-clause 3.1.2.3
The total force value of the wind over a lattice tower shall be, at least, the following:
V V is the reference wind velocity in km/h
A T is the area of the tower projected in a perpendicular plane to the wind direction, in m 2
E_d represents the total design value of the effects of actions, including internal forces or moments, or a representative vector of multiple internal forces or moments, as outlined in sub-clause 3.7.2 of the main body.
R d is the corresponding structural design resistance, as defined in sub-clause 3.7.2 of the main body
CS is the minimum security factor for each element and load case defined in clause
Due to the lack, in general, of official statistical data, in Spain Approach 3 shall be used to stablish the numerical values of actions
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 3.1.1
Vertical loads on account of own weight of each element shall be taken into account: conductors, insulators, fittings, ground wires – if they exist –, poles and foundations
4.3.1 Field of application and basic wind velocity
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 3.1.2
For wind velocity considerations, a minimum reference of 120 km/h (33.3 m/s) is required, except for transmission lines operating at 220 kV and above, or for lower voltage lines classified as part of the transmission grid, where the minimum reference wind velocity increases to 140 km/h (38.89 m/s).
This reference wind velocity (VV) shall mean horizontal, acting perpendicular to the areas concerned
4.3.5 Wind forces on any overhead line component
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 3.1.2.4
In the case of a flat surface, the wind force, QWx, shall be at least:
V V is the reference wind velocity in km/h
A x is the area of the flat surface projected in a perpendicular plane to the wind direction, in m 2
(A-dev) ES.2 RD 223/2008, ITC-LAT 07, sub-clause 3.1.2.5
In the case of a cylindrical surface, the wind force, QWx, shall be, at least:
V V is the reference wind velocity in km/h
A x is the area of the cylindrical surface projected in a perpendicular plane to the wind direction, in m 2
(A-dev) ES.3 RD 223/2008, ITC-LAT 07, sub-clause 3.1.2.1
The wind force over conductors in a suspension pole, in the transversal direction of the line, for each conductor of the bundle shall be, at least, the following:
Where: q p is the wind pressure, with the following value:
The reference wind velocity, denoted as V, is measured in km/h, while d represents the diameter of the conductor or sub-conductor in meters When assessing combined wind and ice loads, it is essential to account for the thickness of the ice, with a recommended reference value of 7.500 N/m³ for the specific volumetric weight of ice.
L 1 , L 2 are the lengths of the adjacent spans, in m
Any possible shade effects between conductors, even in the case of phase bundle conductors, shall be neglected
For the wind forces over poles with angle, the influence of the direction change and the lengths of the adjacent spans shall be taken into account
(A-dev) ES.4 RD 223/2008, ITC-LAT 07, sub-clause 3.1.2.2
The wind forces over the insulator sets shall be taken into account The force value shall be, at least, the following:
V V is the reference wind velocity in km/h
A ins is the area of the insulator set projected horizontally in a vertical plane parallel to the axis of the insulator set
(A-dev) ES.5 RD 223/2008, ITC-LAT 07, sub-clause 3.1.2.3
The total force value of the wind over a lattice tower shall be, at least, the following:
V V is the reference wind velocity in km/h
A T is the area of the tower projected in a perpendicular plane to the wind direction, in m 2
Wind forces on overhead line components
(snc) ES.1 Wind forces on overhead line components
In Spain, an alternative method known as Approach 3 is utilized to define wind forces on overhead line components, rendering the structural factors outlined in sub-clause 4.4 inapplicable.
Ice loads
Ice forces on conductors
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 3.1.3
In Spain the ice load per length of the conductor, I (in daN per linear metre), shall be, at least:
• In zones with an altitude over the sea up to 500 m, I = 0
• In zones with an altitude over the sea between 500 and 1.000 m, I = 1,8 √𝑑𝑑𝑑𝑑
• In zones with an altitude over the sea higher than 1.000 m, I = 3, 6 √𝑑𝑑𝑑𝑑
Where: d is the conductor diameter, in mm.
Temperature effects
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 3.2.1
In Spain, the following design situations shall be taken into account: a) Minimum temperature, without other climatic action:
Not relevant b) Extreme wind velocity at next temperature:
• In zones with an altitude over the sea less than 500 m, T = -5 ºC
• In zones with an altitude over the sea between 500 and 1.000 m , T = -10 ºC
• In zones with an altitude over the sea more than 1.000 m, T = -15 ºC c) Minimum temperature combined with a reduced wind velocity:
Not relevant d) Ice load at next temperature:
• In zones with an altitude over the sea between 500 and 1.000 m , T = -15 ºC
• In zones with an altitude over the sea more than 1.000 m, T = -20 ºC e) Ice load combined with a reference wind velocity of, at least, 60 km/h, at next temperature:
• In zones with an altitude over the sea between 500 and 1.000 m , T = -15 ºC
In areas situated at altitudes exceeding 1,000 meters above sea level, a temperature of -20 ºC should be considered This condition applies exclusively to overhead power lines operating at voltages of 220 kV and higher, as well as to lower voltage lines that are part of the transmission grid.
Security loads
General
The security loads shall be taken into account in Spain for lines of nominal voltage up to 45 kV.
Torsional loads
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 3.1.5
The breakage of one or more conductors or ground wires must be considered, applying the load at the most unfavorable point for any pole element, especially when the load is eccentric Additionally, for poles located at points where the line direction changes, the resultant load from the tension angle of conductors and ground wires should also be factored in.
• Conductor breakage in poles with suspension sets
One sided load shall be taken into account, corresponding to the breakage of just one conductor or ground wire
The load on suspension insulators can be minimized through the use of specialized devices and by considering the deviation of the insulator set Specifically, for one or two conductors per phase, the minimum load should be 50% of the broken conductor tension; for three conductors per phase, it should be 75%; and for lines with four or more conductors per phase, the load must account for 100% of the broken conductor tension.
• Conductor breakage in poles with strain sets
One sided load shall be taken into account, corresponding to the breakage of just one conductor or ground wire without any reduction of its tension
• Conductor breakage in anchor poles
In electrical lines with a single conductor per phase, the load due to the breakage of a ground wire or conductor must be considered without any tension reduction For bundled conductors, the load should account for the breakage of a ground wire or all conductors in the bundle, assuming a 50% reduction in tension, with no additional reductions applied.
• Conductor breakage in dead end poles
In electrical lines with a single conductor per phase, as well as in bundled conductor lines, the load resulting from the failure of a ground wire or conductor must be considered This applies without any reduction in tension for both scenarios.
• Conductor breakage in special poles
It shall be considered depending on the purpose of each circuit installed in the pole, considering the load producing the most unfavourable situation for any element of the pole.
Longitudinal loads
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 3.1.4
The unbalanced loads to be considered are applied in the conductor and ground wire attach point and shall take into account, therefore, the torsional loads that could be produced
Poles positioned at points where the line direction changes must consider the resultant load from the tension angles of both conductors and ground wires.
• Unbalance in poles with suspension sets
For lines with nominal voltage over 66 kV a longitudinal load equivalent to 15% the one sided tension of all conductors and ground wires shall be considered
For overhead lines with a nominal voltage of up to 66 kV, a longitudinal load equivalent to 8% of the one-sided tension of all conductors and ground wires must be taken into account This load can be distributed along the axis of the pole at the height where the conductors and ground wires are attached.
• Unbalance in poles with strain sets
For lines with nominal voltage over 66 kV a longitudinal load equivalent to 25% the one sided tension of all conductors and ground wires shall be considered
For overhead lines with a nominal voltage of up to 66 kV, a longitudinal load equivalent to 15% of the one-sided tension of all conductors and ground wires must be taken into account This load can be distributed along the axis of the pole at the height where the conductors and ground wires are attached.
A longitudinal load equivalent to 50% the one sided tension of all conductors and ground wires shall be considered
4.4 Wind forces on overhead line components
(snc) ES.1 Wind forces on overhead line components
In Spain, an alternative method known as Approach 3 is utilized to define wind forces on overhead line components, rendering the structural factors outlined in sub-clause 4.4 inapplicable.
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 3.1.3
In Spain the ice load per length of the conductor, I (in daN per linear metre), shall be, at least:
• In zones with an altitude over the sea up to 500 m, I = 0
• In zones with an altitude over the sea between 500 and 1.000 m, I = 1,8 √𝑑𝑑𝑑𝑑
• In zones with an altitude over the sea higher than 1.000 m, I = 3, 6 √𝑑𝑑𝑑𝑑
Where: d is the conductor diameter, in mm
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 3.2.1
In Spain, the following design situations shall be taken into account: a) Minimum temperature, without other climatic action:
Not relevant b) Extreme wind velocity at next temperature:
• In zones with an altitude over the sea less than 500 m, T = -5 ºC
• In zones with an altitude over the sea between 500 and 1.000 m , T = -10 ºC
• In zones with an altitude over the sea more than 1.000 m, T = -15 ºC c) Minimum temperature combined with a reduced wind velocity:
Not relevant d) Ice load at next temperature:
• In zones with an altitude over the sea between 500 and 1.000 m , T = -15 ºC
• In zones with an altitude over the sea more than 1.000 m, T = -20 ºC e) Ice load combined with a reference wind velocity of, at least, 60 km/h, at next temperature:
• In zones with an altitude over the sea between 500 and 1.000 m , T = -15 ºC
In areas situated at altitudes exceeding 1,000 meters above sea level, a temperature of -20 ºC must be considered This condition applies exclusively to overhead power lines operating at voltages of 220 kV and higher, as well as to lower voltage lines that are part of the transmission grid.
The security loads shall be taken into account in Spain for lines of nominal voltage up to 45 kV
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 3.1.5
The breakage of one or more conductors or ground wires must be considered, applying the load at the most unfavorable point for any pole element, especially when the load is eccentric Additionally, for poles located at points where the line direction changes, the resultant load from the tension angles of conductors and ground wires should also be factored in.
• Conductor breakage in poles with suspension sets
One sided load shall be taken into account, corresponding to the breakage of just one conductor or ground wire
The load on suspension insulator sets can be minimized through the use of specialized devices It is important to consider specific tension values based on the number of conductors per phase: a minimum of 50% for one or two conductors, 75% for three conductors, and 100% for four or more conductors.
• Conductor breakage in poles with strain sets
One sided load shall be taken into account, corresponding to the breakage of just one conductor or ground wire without any reduction of its tension
• Conductor breakage in anchor poles
In electrical lines with a single conductor per phase, the load resulting from the breakage of a ground wire or conductor must be considered without any tension reduction For lines with bundled conductors, the breakage of a ground wire or all conductors in the bundle is accounted for, assuming a 50% reduction in tension, with no additional reductions applied.
• Conductor breakage in dead end poles
In electrical lines with a single conductor per phase, as well as in bundled conductor lines, the load resulting from the failure of a ground wire or conductor must be considered This applies without any reduction in tension for both scenarios.
• Conductor breakage in special poles
It shall be considered depending on the purpose of each circuit installed in the pole, considering the load producing the most unfavourable situation for any element of the pole
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 3.1.4
The unbalanced loads to be considered are applied in the conductor and ground wire attach point and shall take into account, therefore, the torsional loads that could be produced
Poles positioned at points where the line direction changes must consider the resultant load from the tension angles of both conductors and ground wires.
• Unbalance in poles with suspension sets
For lines with nominal voltage over 66 kV a longitudinal load equivalent to 15% the one sided tension of all conductors and ground wires shall be considered
For lines with a nominal voltage of up to 66 kV, a longitudinal load equivalent to 8% of the one-sided tension of all conductors and ground wires must be taken into account This load can be distributed along the axis of the pole at the height where the conductors and ground wires are attached.
• Unbalance in poles with strain sets
For lines with nominal voltage over 66 kV a longitudinal load equivalent to 25% the one sided tension of all conductors and ground wires shall be considered
For overhead lines with a nominal voltage of up to 66 kV, a longitudinal load equivalent to 15% of the one-sided tension of all conductors and ground wires must be taken into account This load can be distributed along the axis of the pole at the height where the conductors and ground wires are attached.
A longitudinal load equivalent to 50% the one sided tension of all conductors and ground wires shall be considered
For nominal voltages up to 66 kV, the load can be regarded as distributed along the axis of the pole, specifically at the height where the conductors and ground wires are attached.
• Unbalance in dead end poles
A longitudinal load equivalent to 100% the one sided tension of all conductors and ground wires shall be considered
• Very pronounced unbalance in poles
In poles with significant load imbalances between adjacent spans, it is essential to analyze the conductor tension under the most unfavorable conditions If this analysis yields results that are more adverse than previously established values, the new findings will take precedence.
When designing special poles, it is essential for the designer to evaluate the most unfavorable unbalanced load that conductors and ground wires may exert on the pole This assessment should consider the specific purpose of each circuit, and the load must be applied at the point that creates the most adverse conditions for any component of the pole.
Load cases
General
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 3.5.3
For suspension and angle poles with conductors rated over 66 kV and tensile strength below 6600 daN, torsional loads can be disregarded if two conditions are met: first, both conductors and ground wires must have a security factor exceeding 3; second, the security factor for poles and foundations in load case 5b should align with that of cases 1a.
2a and 3 c) Anchor poles are installed every 3 km (maximum).
Standard load cases
(snc) ES.1 Standard load cases
In Spain there are no climatic conditions associated to load cases 2b, 2c and 2d defined in Table
4.6 of the main body Therefore, reduction factors applied to ice load per length defined in sub- clause 4.12.2 may have the next values: α = 1; α1 = 1; α2 = 1; α3 = 1; α4 = 1
Partial factors for actions
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 3.5.4
Normal load cases shall be 1a, 2a, 2b, 2c, 2d, 3 and 4 defined in Table 4.6 of the main body
Abnormal load cases shall be 5a y 5b defined in Table 4.6 of the main body
The security factor CS of poles shall be, at least, the following:
• Metallic elements: the security factor to the yield stress shall not be less than 1,5 for normal load cases and 1,2 for abnormal load cases
• When the mechanical strength of complete poles is verified by a full scale test, the previous values may be reduced to 1,45 and 1,15 respectively
• Reinforced concrete elements: The security factor of poles and reinforced concrete elements shall be the mentioned in standard UNE 207016 In abnormal load cases the security factor may be reduced 20%
• Wooden elements: The security factors shall not be less than 3,5 for normal load cases and 2,8 for abnormal load cases
• Guys: The wires or bars used in guys shall have a security factor not less than 3 for normal load cases and 2,5 for abnormal load cases
(A-dev) ES.2 RD 223/2008, ITC-LAT 07, clause 5.3
In specific scenarios, such as crossings, parallel alignments with other lines, communication routes, or urban areas, it is essential to enhance safety measures To reduce accident risks and improve line security, the safety factors for normal load cases must be increased by 25% compared to those specified in clause 4.13/ES.1.
The enhanced security factor does not apply to transmission grid lines of 220 kV and above, or below 220 kV, as the mechanical strength of the poles is based on a minimum reference wind speed of 140 km/h and considers a combined load scenario of ice and wind.
Currents
Normal current
(A-dev) ES.1 RD 223/2008, ITC-LAT 07
The maximum current densities under permanent rating conditions shall not exceed the values indicated in the following table
If the project includes a study of temperatures attained in the conductors, taking into account climatological conditions and load line, different values may be acceptable
Table 5.2.1/ES.1 – Conductor current density
The values shown in the previous table refer to materials having the following values of resistivity at 20ºC:
For galvanized steel a resistivity of 0,192 Ω.mm 2 /m may be considered and for aluminium clad steel 0,0848 Ω.mm 2 /m.
For nominal voltages up to 66 kV, the load can be regarded as distributed along the axis of the pole, specifically at the height where the conductors and ground wires are attached.
• Unbalance in dead end poles
A longitudinal load equivalent to 100% the one sided tension of all conductors and ground wires shall be considered
• Very pronounced unbalance in poles
In poles with significant load imbalances between adjacent spans, it is essential to analyze the conductor tension under the most unfavorable conditions If this analysis yields results that are more adverse than previously established values, the new results will take precedence.
When dealing with special poles, designers must evaluate the most adverse unbalanced load that conductors and ground wires can exert on the pole, considering the specific function of each circuit This load should be applied at the point that creates the most detrimental condition for any component of the pole.
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 3.5.3
For lines with a nominal voltage exceeding 66 kV, torsional loads can be disregarded for suspension and angle poles with suspension and strain sets, provided that the conductors have a rated tensile strength below 6600 daN This is applicable when two conditions are met: first, the security factor for conductors and ground wires must be greater than 3; second, the security factor for poles and foundations in load case 5b should align with that of cases 1a.
2a and 3 c) Anchor poles are installed every 3 km (maximum)
(snc) ES.1 Standard load cases
In Spain there are no climatic conditions associated to load cases 2b, 2c and 2d defined in Table
4.6 of the main body Therefore, reduction factors applied to ice load per length defined in sub- clause 4.12.2 may have the next values: α = 1; α1 = 1; α2 = 1; α3 = 1; α4 = 1
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 3.5.4
Normal load cases shall be 1a, 2a, 2b, 2c, 2d, 3 and 4 defined in Table 4.6 of the main body
Abnormal load cases shall be 5a y 5b defined in Table 4.6 of the main body
The security factor CS of poles shall be, at least, the following:
• Metallic elements: the security factor to the yield stress shall not be less than 1,5 for normal load cases and 1,2 for abnormal load cases
• When the mechanical strength of complete poles is verified by a full scale test, the previous values may be reduced to 1,45 and 1,15 respectively
• Reinforced concrete elements: The security factor of poles and reinforced concrete elements shall be the mentioned in standard UNE 207016 In abnormal load cases the security factor may be reduced 20%
• Wooden elements: The security factors shall not be less than 3,5 for normal load cases and 2,8 for abnormal load cases
• Guys: The wires or bars used in guys shall have a security factor not less than 3 for normal load cases and 2,5 for abnormal load cases
(A-dev) ES.2 RD 223/2008, ITC-LAT 07, clause 5.3
In specific scenarios, including crossings, parallel alignments with other lines, communication routes, or urban areas, it is essential to enhance safety measures To minimize accident risks and improve line security, the safety factors for normal load cases must be increased by 25% compared to those specified in clause 4.13/ES.1.
The enhanced security factor does not apply to transmission grid lines of 220 kV and above, or below 220 kV, as the mechanical strength of poles is based on a minimum reference wind speed of 140 km/h and considers a combined load scenario of ice and wind.
(A-dev) ES.1 RD 223/2008, ITC-LAT 07
The maximum current densities under permanent rating conditions shall not exceed the values indicated in the following table
If the project includes a study of temperatures attained in the conductors, taking into account climatological conditions and load line, different values may be acceptable
Table 5.2.1/ES.1 – Conductor current density
The values shown in the previous table refer to materials having the following values of resistivity at 20ºC:
For galvanized steel a resistivity of 0,192 Ω.mm 2 /m may be considered and for aluminium clad steel 0,0848 Ω.mm 2 /m.
For aluminium-steel cables, the current density value should be based on the total cross section as if it were aluminium This value is then adjusted by a reduction coefficient that varies according to the cable's composition.
The resulting value will be applied to the entire cross section of the cable
For aluminium-steel alloy cables, the process is analogous, on the basis of the current density corresponding to aluminium alloy and using the same reduction coefficients depending on composition
For different cable types, the maximum allowable density can be calculated by multiplying the copper density value listed in the table for the corresponding cross section by a coefficient of 1.724.
Where: ρ is the resistivity at 20° C of the conductor in question, expressed in microohms/centimetre.
Insulation co-ordination
(A-dev) ES.1 RD 223/2008, ITC-LAT 07
Insulation coordination involves selecting the appropriate dielectric strength of materials based on the voltages present in the grid, while also considering ambient conditions and the features of available protective devices.
The dielectric strength of the materials is here considered in the standard insulation level sense
The principles and rules of insulation co-ordination are described in EN 60071-1 and EN 60071-2
The procedure for insulation co-ordination involves the selection of a set of standard withstand voltages which characterise the insulation
The minimum standard insulation levels corresponding to the highest voltage of the line, as this one is defined in clause 5.4, shall be those in Tables 5.3.1/ES.1 and 5.3.2/ES.1
The tables present the standard withstand voltages for ranges I and II, categorizing them by standard insulation levels that correspond to the highest voltage for equipment, denoted as Um.
In range I, the standard withstand voltages consist of power frequency and fast front withstand voltages, while in range II, they include low front and fast front withstand voltages.
For other values of the highest voltage not included in the table, standards EN 60071-1 and EN
For design lines operating at voltages exceeding those specified in the tables, the insulation levels must be determined in accordance with standards EN 60071-1 and EN 60071-2.
Table 5.3.1/ES.1 – Standard insulation levels for range I
Standard power frequency withstand voltage (effective) kV
Standard fast front withstand voltage (peak) kV
Note: If the values between brackets are not enough to probe the specific withstand voltages between phases are fulfilled, more additional withstand voltages between phases tests are required.
For aluminium-steel cables, the current density value should be based on the total cross section as if it were aluminium This value is then adjusted by a reduction coefficient that varies according to the cable's composition.
The resulting value will be applied to the entire cross section of the cable
For aluminium-steel alloy cables, the process is analogous, on the basis of the current density corresponding to aluminium alloy and using the same reduction coefficients depending on composition
For different cable types, the maximum allowable density can be calculated by multiplying the copper density value listed in the table for the corresponding cross section by a coefficient of 1.724.
Where: ρ is the resistivity at 20° C of the conductor in question, expressed in microohms/centimetre
(A-dev) ES.1 RD 223/2008, ITC-LAT 07
Insulation coordination involves selecting the appropriate dielectric strength of materials based on the voltages present in the grid, while also considering ambient conditions and the features of available protective devices.
The dielectric strength of the materials is here considered in the standard insulation level sense
The principles and rules of insulation co-ordination are described in EN 60071-1 and EN 60071-2
The procedure for insulation co-ordination involves the selection of a set of standard withstand voltages which characterise the insulation
The minimum standard insulation levels corresponding to the highest voltage of the line, as this one is defined in clause 5.4, shall be those in Tables 5.3.1/ES.1 and 5.3.2/ES.1
The tables present the standard withstand voltages for ranges I and II, categorizing them by standard insulation levels that correspond to the highest voltage for equipment, denoted as Um.
In range I, the standard withstand voltages consist of power frequency and fast front withstand voltages In range II, the standards include low front and fast front withstand voltages.
For other values of the highest voltage not included in the table, standards EN 60071-1 and EN
For design lines operating at voltages exceeding those specified in the tables, the insulation levels must be determined in accordance with standards EN 60071-1 and EN 60071-2.
Table 5.3.1/ES.1 – Standard insulation levels for range I
Standard power frequency withstand voltage (effective) kV
Standard fast front withstand voltage (peak) kV
Note: If the values between brackets are not enough to probe the specific withstand voltages between phases are fulfilled, more additional withstand voltages between phases tests are required.
Table 5.3.2/ES.1 – Standard insulation levels for range II
Standard slow front withstand voltage Standard fast front withstand voltage (Note 2) kV (peak)
Longitudinal insulation (Note 1) (peak) kV
Phase-Phase (relationship to Phase-Earth value)
Note 1: Value of the component of the slow front voltage test combined while the component of the power frequency in the opposite terminal reaches a value of Um √2/√3
Note 2: For the longitudinal insulation tests, EN 60071-1 shall apply
The minimum length of insulator sets is influenced by the permanent power frequency voltage and temporal overvoltages Additionally, the design of the insulators should be chosen based on the pollution zone through which the line traverses.
In grids with a defect factor of 1.3 or lower, it is typically sufficient to design insulators to handle the maximum phase-earth voltage However, for higher fault to earth factors, particularly in isolated neutral grids or those earthed by a compensation coil, it is important to take temporal overvoltages into account.
The withstand coordination voltage for permanent power frequency voltages matches the highest grid voltage for insulation between phases, and it is equivalent to that voltage divided by the square root of three for phase-to-earth insulation.
The slow front at power frequency withstand coordination voltage aligns with the representative temporal overvoltage when employing a deterministic method for insulation coordination studies, according to EN 60071-2.
The specific withstand voltage Urw shall be calculated using the coordination withstand voltage, taking into account a correction factor associated with the ambient conditions of the installation, as per EN 50341-1
In polluted environments, the performance of insulators under power frequency voltages can be significantly affected Insulators must be capable of enduring the maximum grid voltage under persistent pollution conditions while maintaining an acceptable risk of flashovers Consequently, it is essential to choose the appropriate type and length of insulator based on the pollution level in the area where the line operates.
Classification of voltages and overvoltages
Representative power frequency voltages
(A-dev) ES.1 RD 223/2008, ITC-LAT 07
The standard nominal voltages of the grid and the corresponding values of the highest voltages are included in Table 5.4/ES.1.
Table 5.3.2/ES.1 – Standard insulation levels for range II
Standard slow front withstand voltage Standard fast front withstand voltage (Note 2) kV
Note 1: Value of the component of the slow front voltage test combined while the component of the power frequency in the opposite terminal reaches a value of Um √2/√3
Note 2: For the longitudinal insulation tests, EN 60071-1 shall apply
The minimum length of insulator sets is influenced by the permanent power frequency voltage and temporal overvoltages Additionally, the design of the insulators should be chosen based on the pollution zone through which the line traverses.
In grids with a defect factor of 1.3 or lower, it is typically sufficient to design insulators to endure the maximum phase-earth voltage However, for higher fault to earth factors, particularly in isolated neutral grids or those earthed by a compensation coil, it is essential to take temporal overvoltages into account.
The withstand coordination voltage for permanent power frequency voltages matches the highest grid voltage for insulation between phases, and it is equivalent to that voltage divided by the appropriate factor for phase-to-earth insulation.
The slow front at power frequency withstand coordination voltage aligns with the representative temporal overvoltage when employing a deterministic method for insulation coordination studies, according to EN 60071-2.
The specific withstand voltage Urw shall be calculated using the coordination withstand voltage, taking into account a correction factor associated with the ambient conditions of the installation, as per EN 50341-1
In polluted environments, the performance of insulators under power frequency voltages can be significantly affected Insulators must be capable of enduring the maximum grid voltage under persistent pollution conditions while maintaining an acceptable risk of flashovers Consequently, it is essential to choose the appropriate type and length of insulator based on the pollution level of the area where the line operates.
The pollution levels for the area will be determined using Table 5.3.3/ES.1, which outlines four distinct levels Each pollution level includes a general description of various zones, detailing their typical ambient conditions and the minimum necessary air clearance.
Table 5.3.3/ES.1 - Recommended air clearances
Pollution level Typìcal environment examples
Specific minimum nominal air clearance mm/kV 1)
- No industry and low density of homes equipped with heating zones
- Low density of industry or homes with frequent wind or rains zones
- All this zones are situated less than 10 to 20 km from the sea and they are not exposed to direct winds from the sea 3)
- Zones with industry which does not produce specially polluting smoke and/or medium density of homes with heating zones
- Zones with high density of homes and/or industry but with frequent rain and/or wind
- Zones exposed to winds from the sea, but not to close to the coast (at least far away quite kilometres) 3)
- Zones with high density of industry and big city suburbs with high density of heating producing pollution
- Zones near the sea or in any case, exposed to frequent winds from the sea 3)
- Zones, generally of moderate extension, subjected to conductive dusts and industrial smoke which produces deposits particularly dense on conductors
- Zones, generally of moderate extension, very near the coast and exposed to saline pulverization or very strong and polluted winds from the sea
- Desert zones, with no rain during long periods of time, exposed to strong winds which run with sand and salt, and subject to regular condensation
1) Minimum air clearance of insulators between phase and earth related to highest grid voltage (phase- phase)
2) The use of fertilisers by inhalation or waste burn may come to a higher pollution level by wind dispersion
3) The distance from the coast depends on the coast orography and the extreme wind conditions
5.4 Classification of voltages and overvoltages 5.4.2 Representative power frequency voltages
(A-dev) ES.1 RD 223/2008, ITC-LAT 07
The standard nominal voltages of the grid and the corresponding values of the highest voltages are included in Table 5.4/ES.1.
Table 5.4/ES.1 - Nominal voltages and highest grid voltages
(*) Preferred voltages in electric company grids
Only in the case a line is an extension of an existing grid, the use of a different nominal voltage from the mentioned above may be permitted
From the above mentioned voltages, next ones are preferred:
20 kV, 66 kV, 132 kV, 220 kV and 400 kV
For voltages above 400 kV, the new proposed voltage step shall be properly justified, in agreement with the international technical bodies and with the bordering countries criteria.
Minimum air clearance distances to avoid flashovers
(A-dev) ES.1 RD 223/2008, ITC-LAT 07
Three types of electrical distances are considered:
To prevent flashovers between phase conductors and earth potential objects during both slow and fast overvoltages, it is essential to establish specific minimum insulation air clearance distances This includes internal clearances, which refer to the distance from the conductor to the tower structure, and external clearances, which pertain to the distance from the conductor to nearby obstacles.
To prevent flashovers between phase conductors during both slow and fast overvoltages, it is essential to maintain specific minimum insulation air clearance distances, known as Dpp Dpp refers to the internal distance required for safety Additionally, the minimum insulator set flashover distance, termed as asom, is defined as the shortest straight-line distance between live and earthed components.
To determine internal and external distances, several key considerations must be addressed First, the electrical clearance, Del, is essential for preventing flashovers between live and earthed parts under normal grid conditions, which include switching, lightning, and overvoltages from grid faults Additionally, the electrical clearance, Dpp, is crucial for preventing flashovers between phases during switching and lightning overvoltages An external clearance must be added to Del, along with an additional insulation clearance, Dadd, to ensure that minimum security clearances to the ground, electric lines, and surrounding areas are maintained, protecting people and objects from coming too close to electric lines Furthermore, the probability of flashover through the minimum internal clearance, asom, must always exceed the risk of flashover from any object or person Consequently, for long insulator sets, the risk of flashover must be greater than the internal clearance asom compared to clearances for external objects and individuals Therefore, the minimum security external clearances (Dadd + Del) should always be greater than 1.1 times asom.
Values of Del y Dpp, depending on the highest voltage of the line, US, shall be the ones described in Table 5.5/ES.1
Table 5.5/ES.1 Minimum insulation clearances, D el and D pp ,to avoid flashovers
Values given in the table above are based in an analysis of values generally used in Europe, which have been proved as sufficiently safe for people.
Load cases for calculation of clearances
Load conditions
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 3.2.3
The maximum sag of conductors and ground wires is determined based on specific hypotheses aligned with the overload zone classification outlined in clauses 4.4 and 4.5 The wind hypothesis considers the conductor's weight and a wind-induced overload of 120 km/h at 15 °C The temperature hypothesis accounts for the conductor's weight at the highest foreseeable temperature, with special category lines requiring a minimum of 85 ºC for phase conductors and 50 ºC for ground wires, while other lines must not fall below 50 ºC Lastly, the ice hypothesis evaluates the conductor's weight plus ice-induced overload for the respective zone at a temperature of 0 °C.
For overhead lines operating at voltages exceeding 66 kV, it is crucial to account for significant creep increases in conductors over their lifespan This consideration is essential for accurate sag calculations, influenced by the characteristics of the conductors and the conditions under which they are strung.
Internal clearances within the span and at the top of support
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 5.4.1
The spacing between phase conductors, whether from the same or different circuits, must be sufficient to prevent short-circuits between phases This consideration should account for conductor oscillations caused by wind and the potential dislodging of accumulated snow.
In this respect, the minimum separation between phase conductors will be determined in accordance with the following formula:
Table 5.4/ES.1 - Nominal voltages and highest grid voltages
(*) Preferred voltages in electric company grids
Only in the case a line is an extension of an existing grid, the use of a different nominal voltage from the mentioned above may be permitted
From the above mentioned voltages, next ones are preferred:
20 kV, 66 kV, 132 kV, 220 kV and 400 kV
For voltages above 400 kV, the new proposed voltage step shall be properly justified, in agreement with the international technical bodies and with the bordering countries criteria
5.5 Minimum air clearance distances to avoid flashovers
(A-dev) ES.1 RD 223/2008, ITC-LAT 07
Three types of electrical distances are considered:
To prevent flashovers between phase conductors and earth potential objects, it is essential to establish specific minimum insulation air clearance distances for both slow and fast overvoltages This includes internal clearances, which refer to the distance from the conductor to the tower structure, and external clearances, which pertain to the distance from the conductor to nearby obstacles.
To prevent flashovers between phase conductors during both slow and fast overvoltages, it is crucial to maintain the specific minimum insulation air clearance distance, known as Dpp This internal distance is essential for ensuring safety Additionally, the minimum insulator set flashover distance, referred to as asom, is defined as the shortest straight-line distance between live and earthed components.
To determine internal and external distances, several key considerations must be addressed First, the electrical clearance, Del, is essential for preventing flashovers between live and earthed parts under normal grid conditions, which include switching, lightning, and overvoltages from grid faults Second, the electrical clearance, Dpp, is crucial for preventing flashovers between phases during switching and lightning overvoltages Additionally, an external clearance must be added to Del, known as the additional insulation clearance (Dadd), to ensure that minimum security clearances to the ground, electric lines, and surrounding areas are maintained, protecting people and objects from coming too close to electric lines Furthermore, the probability of flashover through the minimum internal clearance (asom) must always exceed the risk of flashover involving any object or person Consequently, for long insulator sets, the risk of flashover must be greater than the internal clearance asom compared to clearances for external objects and individuals Therefore, the minimum security external clearances (Dadd + Del) should always be greater than 1.1 times asom.
Values of Del y Dpp, depending on the highest voltage of the line, US, shall be the ones described in Table 5.5/ES.1
Table 5.5/ES.1 Minimum insulation clearances, D el and D pp ,to avoid flashovers
Values given in the table above are based in an analysis of values generally used in Europe, which have been proved as sufficiently safe for people
5.6 Load cases for calculation of clearances 5.6.1 Load conditions
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 3.2.3
The maximum sag of conductors and ground wires is determined based on specific hypotheses aligned with the overload zone classification outlined in clauses 4.4 and 4.5 The wind hypothesis considers the conductor's weight and a wind-induced overload of 120 km/h at 15 °C The temperature hypothesis accounts for the conductor's weight at the highest foreseeable temperature, with special category lines requiring a minimum of 85 ºC for phase conductors and 50 ºC for ground wires, while other lines must not fall below 50 ºC Lastly, the ice hypothesis evaluates the conductor's weight plus ice-induced overload for the respective zone at a temperature of 0 °C.
For overhead lines operating at voltages exceeding 66 kV, it is crucial to account for significant creep increases in conductors over their lifespan, which may arise from the conductors' properties or stringing conditions, when performing sag calculations.
5.8 Internal clearances within the span and at the top of support
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 5.4.1
To prevent short-circuits between phase conductors, whether from the same or different circuits, it is essential to maintain a safe distance that considers the impact of conductor oscillations caused by wind and the potential dislodging of accumulated snow.
In this respect, the minimum separation between phase conductors will be determined in accordance with the following formula:
D = Separation between phase conductors of same or different circuits, in metres
K = Coefficient depending on the oscillation of the conductors with the wind, as per the table 16 of
K’= Coefficient depending on the nominal voltage of the line K’ = 0,85 for special category lines and K’ = 0,75 for other lines
F = Maximum sag in metres, as per sub-clause 3.2.3 of ITC-LAT 07
L = Length in metres of the suspension set In the case of conductors fixed to the support by strain sets or rigid insulators L = 0
D pp = Minimum specific aerial clearance to avoid flashover between phase conductors during slow and fast overvoltages Values of D pp are included in clause 5.2 of ITC-LAT 07
The tangent values of the oscillation angle for conductors are determined by the ratio of wind load to the conductor's weight, along with any applicable ice overload based on the zone and conductor length The initial wind load is calculated for a reference wind speed of 120 km/h Additionally, the K coefficient is provided in the accompanying table, based on these values and the line's nominal voltage.
Table 5.8/ES.1 - K coefficient based on the oscillation angle
Values of K Oscillation angle Nominal voltage lines over
30 kV Nominal voltage lines up to 30 kV
This minimum clearance shall not apply to distance between conductors in the same bundle
When selecting clearances for conductors arranged vertically, in a triangle, or hexagonal configuration, it is essential to validate the chosen values if they are smaller than previously determined For vertical conductors where galloping phenomena are not anticipated, a coefficient of K = 0 and K' = 1 can be utilized.
In zones in which particularly important ice accretions may be expected on conductors, special care shall be taken when analysing the risk of inadmissible approximations between conductors
For conductors with varying sag or different types, the separation distance should be calculated using the same formula, applying the largest K coefficient and the maximum F sag from both conductors If smaller clearances are utilized, the chosen values must be adequately justified.
The separation between conductors and ground wires will be determined analogously to the case of separation between different conductors, as per the previous paragraphs
If the ground wire anchor point within the tower is higher than the conductor’s, the ground wire sag shall be the same or smaller than the conductor’s sag
(A-dev) ES.2 RD 223/2008, ITC-LAT 07, sub-clause 5.4.2
The minimum separation between conductors and their accessories under voltage and poles shall not be less than Del, the minimum being 0,2 m
The values of Del are given in clause 5.5/ES.1 dependant on higher voltage of the line
For suspension sets, both conductors and insulator sets are deemed to be affected by a wind pressure equivalent to half that of a 120 km/h wind Additionally, conductors are evaluated under this wind pressure, along with specific temperature conditions: -5 ºC for Zone A, -10 ºC for Zone B, and -15 ºC for Zone C.
Counterweighs should not be used repeatedly along the line; however, they may be utilized in exceptional cases to minimize suspension set deviations In such instances, the designer must validate the deviation values and ensure clearances to the pole are maintained.
External clearances
General
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, clause 5.3
In areas where lines intersect with other roads or urban environments, enhanced security measures are necessary to minimize the risk of failure Therefore, specific requirements outlined in this section must be adhered to, in addition to general safety considerations.
Special requirements are not needed for crossings and parallel stretches with non-navigable water courses, bridle paths, trails, glens, and fences without buildings, unless an increase in the height of the conductors is necessary for the latter.
In specific line sectors that require enhanced security measures, alternative supports beyond those designated for their position will not be necessary, nor will there be restrictions on span lengths that would typically apply under general conditions.
In specific line sectors, special conditions apply: a) The rated tensile strength of conductors or earth wires must be at least 1,200 daN for lines with a rated voltage above 30 kV, and at least 1,000 daN for lines at or below 30 kV If the tensile strength is below this threshold, a suitable messenger cable with a tensile strength exceeding 1,000 daN may be used Conductors and earth wires must not have any joints in the crossing span, although one joint for repair purposes is permitted along the span's lifetime b) The use of wooden supports is prohibited c) The security factor must be increased as specified in section 4.13 ES.2 d) Conductors must be securely fixed to supports as outlined.
1 In the case of lines on rigid insulators, two insulators should be placed under every conductor, arranged perpendicular to the axis, in such a way that one of them give support to the conductor and the other give support to an additional conductor that extend along both direction a distance long enough to include inside an arc discharge in case it happens This cross over tie should be fixed in both sides to the conductor using anchors or fittings which will ensure an effective union Likewise, the anchors between the conductor and the cross over tie and their respective insulators should guarantee a high slip load
2 In the case of lines with insulator string, the fixing may be effected in one of the following ways: a Using two tension strings per conductor, one on each side of the support b Using a single suspension string in which the mechanical security factors for fittings and insulators are 25 per cent higher than those set out in chapters 10 and
11, or using a double suspension string In these cases one of the following additional considerations must be fulfilled:
1 Conductor must be reinforced using armor rods
2 Use of arcing horns or arcing rings which prevent direct arcing flashover on the conductor
D = Separation between phase conductors of same or different circuits, in metres
K = Coefficient depending on the oscillation of the conductors with the wind, as per the table 16 of
K’= Coefficient depending on the nominal voltage of the line K’ = 0,85 for special category lines and K’ = 0,75 for other lines
F = Maximum sag in metres, as per sub-clause 3.2.3 of ITC-LAT 07
L = Length in metres of the suspension set In the case of conductors fixed to the support by strain sets or rigid insulators L = 0
D pp = Minimum specific aerial clearance to avoid flashover between phase conductors during slow and fast overvoltages Values of D pp are included in clause 5.2 of ITC-LAT 07
The tangent values of the oscillation angle for conductors are determined by the ratio of wind load to the conductor's weight, along with any applicable ice overload, divided by the conductor length The initial wind load is calculated for a reference wind speed of 120 km/h Based on these values and the line's nominal voltage, the K coefficient is provided in the accompanying table.
Table 5.8/ES.1 - K coefficient based on the oscillation angle
Values of K Oscillation angle Nominal voltage lines over
30 kV Nominal voltage lines up to 30 kV
This minimum clearance shall not apply to distance between conductors in the same bundle
When selecting clearances for conductors arranged vertically, in a triangle, or hexagonal configuration, it is essential to validate the chosen values if they are smaller than previously determined For vertically arranged conductors where galloping phenomena are not anticipated, a coefficient of K = 0 and K' = 1 can be utilized.
In zones in which particularly important ice accretions may be expected on conductors, special care shall be taken when analysing the risk of inadmissible approximations between conductors
For conductors with varying sag or different types, the separation distance should be calculated using the same formula, applying the largest K coefficient and the maximum F sag from both conductors If smaller clearances are utilized, the chosen values must be adequately justified.
The separation between conductors and ground wires will be determined analogously to the case of separation between different conductors, as per the previous paragraphs
If the ground wire anchor point within the tower is higher than the conductor’s, the ground wire sag shall be the same or smaller than the conductor’s sag
(A-dev) ES.2 RD 223/2008, ITC-LAT 07, sub-clause 5.4.2
The minimum separation between conductors and their accessories under voltage and poles shall not be less than Del, the minimum being 0,2 m
The values of Del are given in clause 5.5/ES.1 dependant on higher voltage of the line
For suspension sets, both conductors and insulator sets are deemed to be affected by a wind pressure equivalent to half that of a 120 km/h wind Additionally, conductors are evaluated under this wind pressure, along with specific temperature conditions: -5 ºC for Zone A, -10 ºC for Zone B, and -15 ºC for Zone C.
Counterweighs should not be used repeatedly along the line; however, they may be utilized in exceptional cases to minimize the deviation of suspension sets In such instances, the designer must validate the values of deviations and clearances to the pole.
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, clause 5.3
In areas like crossings, parallel alignments with other roads, or urban settings where line security is heightened to minimize failure risks, specific requirements outlined in this section must be fulfilled alongside general guidelines.
Special requirements are not needed for crossings and parallel stretches with non-navigable water courses, bridle paths, trails, glens, and fences without buildings, unless an increase in the height of the conductors is necessary.
In specific line sectors that require enhanced security measures, additional supports beyond the designated position on the line, such as suspension, tension, or anti-cascading systems, are unnecessary Furthermore, there will be no restrictions on span lengths that would typically apply under general conditions.
In specific line sectors, special conditions must be met: a) The rated tensile strength of conductors or earth wires must be at least 1,200 daN for lines with a rated voltage above 30 kV, and at least 1,000 daN for lines at or below 30 kV If the tensile strength is lower, a suitable messenger cable with a strength greater than 1,000 daN may be added Conductors and earth wires must not have any joints in the crossing span, although one joint for repair along the span is permitted b) The use of wooden supports is prohibited c) The security factor must be increased as specified in 4.13 ES.2 d) Conductors must be securely fixed to supports as outlined.
External clearances to ground in areas remote from buildings, roads, etc
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, clause 5.5
The special requirements defined in sub-clause 5.9.1 do not apply
The supports must be tall enough to ensure that, even with the maximum vertical sag as specified in clause 5.6, the conductors remain above any ground point or the surface of non-navigable water courses, maintaining a minimum height requirement.
Dadd + Del = 5,3 + Del in metres, with a minimum of 6 metres However, in places of difficult access the aforementioned distances may be reduced by one metre
The values of Del are given in Table 5.5/ES.1 depending on the highest voltage of the line
To ensure safety and prevent accidents involving water spraying and the movement of farm machinery, trucks, and other vehicles, it is essential that lines passing over closed farms or agricultural holdings maintain a minimum height of 7 meters.
When calculating the maximum sag under windy conditions, the distance should be set to one meter less than previously mentioned, taking into account the deviation caused by the wind on the conductor.
The safety distances to the ground between the maximum vertical sag position of the conductors and their position under wind conditions will be established using the envelope curve of distance circles These circles are plotted at each intermediate conductor position, with a radius that is linearly interpolated between the distances for the vertical position and the maximum deviation, depending on the angle of deviation.
(A-dev) ES.2 RD 223/2008, ITC-LAT 07, sub-clause 5.12.1, Forests, trees and wooded areas
The special requirements defined in sub-clause 5.9.1 do not apply
To prevent service interruptions and reduce the risk of fires caused by tree branches and trunks contacting power line conductors, it is essential to establish a protection zone around the power line This zone should be defined by the flying easement zone, with additional safety clearance on both sides of the projection, ensuring proper compensation for the establishment of this protective area.
Dadd + Del = 1,5 + Del in metres, with a minimum of 2 metres The values of Del are given in Table 5.5/ES.1 depending on the highest voltage of the line
The operator of the line must maintain a safe distance between the line conductors and trees within the crossing easement zone, while the landowner is required to facilitate these activities Additionally, the landowner must notify the relevant administrative body about any trees outside the easement zone that may threaten safety distances It is also essential to keep the ground beneath the line clear of any cleaning residues to prevent the risk of wildfires.
- In the event that the conductors stand over the trees, the safety distance is calculated considering the conductors with maximum vertical sag according to load cases in clause 5.6
To determine the safety distances between trees and the extreme conductors of the line, it is essential to consider the conductors and their insulator strings under the most unfavorable conditions outlined in this section.
Trees that pose a risk to the conservation of power lines must be removed This includes trees that could potentially reach the conductors if they bend or fall, whether accidentally or intentionally The assessment of risk depends on various factors, including the type and condition of the tree, the slope and condition of the terrain, and the tree's proximity to the power line, considering the temperature conditions outlined in clause 5.6.
Holders of the transmission and distribution networks must keep free of plants the ground under the line, in order to avoid the generation or spread of wildfires
New line maintenance contracts should incorporate specific clauses that address the selection of suitable plant species, the management of protection zones, and the cleaning and weeding of areas surrounding the lines to effectively prevent fire hazards.
External clearances to residential and other buildings
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 5.12.2, and RD 1955/2000
The special requirements defined in sub-clause 5.9.1 do not apply
Overhead power lines with bare conductors will not be used in urban areas or town centers unless authorized by the relevant administrative body This exception applies when requested by the installation owner and deemed necessary due to technical or economic factors.
High voltage overhead power lines can be installed in designated urban development areas, in accordance with legally approved ordnance surveys, or within industrial estates that have received partial approval for such surveys Additionally, these power lines may be placed on urban land outside the town center in municipalities lacking a complete survey.
According to RD 1955/2000, no buildings or industrial installations are permitted within the ground strip defined by the flying easement, which must be increased by the minimum safety distance on both sides.
Dadd + Del = 3,3 + Del in metres, with a minimum of 5 metres The values of Del are given in Table 5.5/ES.1 depending on the highest voltage of the line
Similarly no lines above buildings and industrial installation can be installed in the strip defined above
In cases of mutual agreement among the parties involved, the minimum distances required under the most unfavorable conditions between power line conductors and the buildings or structures below must be established.
- Over areas accessible to people:
Dadd + Del = 5,5 + Del in metres, with a mínimum of 6 metres
- Over areas inaccessible to people:
Dadd + Del = 3,3 + Del in metres, with a mínimum of 4 metres
Efforts must be made to uphold the specified horizontal distances between the conductors of the line and adjacent buildings or structures, even in the most challenging conditions.
3 Use of wire rod or steel supporting cable on both sides of the string above the conductor and long enough to protect the arcing zone The union of the supporting cable to the conductor will use anti sliding clamps
To effectively camouflage high voltage overhead line towers using green painting or other painted camouflage techniques, facility owners must obtain permits from relevant authorities for low-altitude aircraft flights intended for humanitarian and nature conservation purposes.
5.9.2 External clearances to ground in areas remote from buildings, roads, etc
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, clause 5.5
The special requirements defined in sub-clause 5.9.1 do not apply
The supports must be tall enough to ensure that, even with the maximum vertical sag as specified in clause 5.6, the conductors remain above any ground point or the surface of non-navigable water courses, maintaining a minimum height requirement.
Dadd + Del = 5,3 + Del in metres, with a minimum of 6 metres However, in places of difficult access the aforementioned distances may be reduced by one metre
The values of Del are given in Table 5.5/ES.1 depending on the highest voltage of the line
To ensure safety and prevent accidents involving water spraying and the movement of farm machinery, trucks, and other vehicles, it is essential that lines passing over closed farms or agricultural holdings maintain a minimum height of 7 meters.
When calculating the maximum sag under windy conditions, the distance should be set one meter less than previously mentioned, taking into account the deviation caused by the wind on the conductor.
The safety distances to the ground between the maximum vertical sag of conductors and their positions under wind conditions will be defined by the envelope curve of distance circles at each intermediate position This radius is interpolated between the distances for the vertical position and the maximum deviation, varying linearly with the angle of deviation.
(A-dev) ES.2 RD 223/2008, ITC-LAT 07, sub-clause 5.12.1, Forests, trees and wooded areas
The special requirements defined in sub-clause 5.9.1 do not apply
To prevent service interruptions and reduce the risk of fires caused by tree branches and trunks contacting power line conductors, it is essential to establish a protection zone around the power line This zone should be defined by the flying easement area, supplemented by additional safety clearances on both sides of the projection.
Dadd + Del = 1,5 + Del in metres, with a minimum of 2 metres The values of Del are given in Table 5.5/ES.1 depending on the highest voltage of the line
The operator of the line must maintain a safe distance between the line conductors and the trees within the crossing easement zone, while the landowner is required to facilitate these activities Additionally, the landowner must notify the relevant administrative body about any trees outside the easement zone that may pose a safety risk It is also essential to keep the ground beneath the line clear of any cleaning residues to prevent the risk of wildfires.
- In the event that the conductors stand over the trees, the safety distance is calculated considering the conductors with maximum vertical sag according to load cases in clause 5.6
To determine the safety distances between trees and the extreme conductors of the line, it is essential to consider these conductors and their insulator strings under the most unfavorable conditions outlined in this section.
Trees that pose a risk to the conservation of power lines must be removed This includes trees that could potentially bend or fall, whether accidentally or intentionally, and reach the conductors in their normal position, considering the temperature conditions outlined in clause 5.6 The decision to cut down these trees will depend on their type, condition, the slope and state of the terrain, and their proximity to the power line.
Holders of the transmission and distribution networks must keep free of plants the ground under the line, in order to avoid the generation or spread of wildfires
External clearances to crossing traffic routes
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, clause 5.7, Crossings with roads
Special requirements defined in sub-clause 5.9.1 apply, being modified as follows:
Condition a): Regarding crossing with local and neighborhood roads, the existence of a joint per conductor in the crossing span for the lines over 30 kV rated voltage is allowed
The minimum clearance from the conductors to the surface of the road will be:
Dadd + Del in metres, with a minimum clearance of 7 metres The values of Del are given in Table 5.5/ES.1 depending on the highest voltage of the lines
Where: Dadd = 7.5 for special category lines
Dadd = 6.3 for lines of other categories
(A-dev) ES.2 RD 223/2008, ITC-LAT 07, clause 5.9, Crossings with electrified railways, tram and trolley bus lines
Special requirements defined in sub-clause 5.9.1 apply
In crossings involving power lines and electrified railways, trams, and trolleybuses, it is essential to maintain a minimum vertical distance from the power line conductors This distance should account for the maximum vertical sag of the conductors, as specified in clause 5.6, ensuring safety in relation to the highest conductor of all power lines, telephone lines, and telegraph lines.
Dadd + Del = 3,5 + Del in metres, with a minimum of 4 metres The values of Del are given in Table 5.5/ES.1 depending on the highest voltage of the lines
For railways, trams, and trolley buses with trolley systems, power line conductors must be installed at a height that ensures, even when the contact arrangement is disconnected and positioned unfavorably, they do not come closer than the specified safety distance.
(A-dev) ES.3 RD 223/2008, ITC-LAT 07, sub-clause 5.11, Crossings with navigable rivers and canals
Special requirements defined in sub-clause 5.9.1 apply
In crossovers involving navigable rivers and canals, the conductors must maintain a minimum height above the water's maximum level, accounting for the maximum vertical sag as specified in clause 5.6.
G + D add + D el = G + 3,5 + D el in metres,
G + Dadd + Del = G + 2,3 + Del in metres, where G is the clearance or headroom The values of Del are given in Table 5.5/ES.1 depending on the highest voltage of lines
If no such clearance were defined, this shall be considered equal to 4,7 metres
(A-dev) ES.4 RD 223/2008, ITC-LAT 07, clause 5.10, Crossings with rope ways
Special requirements defined in sub-clause 5.9.1 apply
The crossing of a power line with ropeways or cableways must always be made above them, except for very reasonable justified cases expressly authorized
The minimum vertical clearance between power line conductors, considering maximum sag under load conditions as specified in clause 5.6, and the highest point of ropeways, must account for normal operational fluctuations in their wires and potential uplift due to load reduction during an accident.
Dadd + Del = 4,5 + Del in metres, with a minimum of 5 metres The values of Del are given in Table 5.5/ES.1 depending on the highest voltage of the line
The minimum horizontal distance required between the closest section of the ropeway and the power line support in the crossing span must adhere to the value derived from the specified formula.
The ropeway must be grounded at two points, one on each side of the crossing, in accordance with the requirements of paragraph 6
(A-dev) ES.5 RD 223/2008, ITC-LAT 07, clause 5.8, Crossings with non-electrified railway lines
For the Installation of supports, both in the case of parallelism as in the case of crossings, the following considerations will be taken into account:
A boundary building line is established on both sides of railway lines within the railway network of general interest, prohibiting any building work, refurbishment, or extension from this line to the railway line.
The boundary line of the building is established 50 meters from the outer edge of the earthwork, measured horizontally and perpendicular to the railway's outer lane Support installations are prohibited within the area impacted by the building's boundary line.
To ensure the safety of railway lines, it is essential to obtain the necessary authorization from the relevant administrative bodies before placing support within the protection zone This protection zone is defined as extending 70 meters horizontally from the outer edge of the earthwork, measured perpendicularly to the outer lane of the railway.
- In crossings, supports cannot be installed at a distance lower than one and a half times the height of the support from the outer edge of the earthwork
- In exceptional topographical circumstances and after technical justification and Administration approval, the placement of support for distances less than those set may be allowed
The minimum distance from the conductors of the power line to the top of the rails will be the same used for crossings with roads
Special requirements defined in sub-clause 5.9.1 do not apply in case of parallelism.
External clearances to adjacent traffic routes
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 5.7, Distance to adjacent roads
Special requirements defined in sub-clause 5.9.1 do not apply in case of parallelism
To install supports in crossings and parallelism, specific guidelines must be followed For the State Highways Network, supports should be placed behind the building limit line, which is 50 meters from the road's outer edge on motorways, highways, and freeways, and 25 meters on other state roads, with a distance greater than one and a half times their height For roads outside the State Roads Network, the installation must adhere to the regulations set by the respective Autonomous Community.
5.9.4 External clearances to crossing traffic routes
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, clause 5.7, Crossings with roads
Special requirements defined in sub-clause 5.9.1 apply, being modified as follows:
Condition a): Regarding crossing with local and neighborhood roads, the existence of a joint per conductor in the crossing span for the lines over 30 kV rated voltage is allowed
The minimum clearance from the conductors to the surface of the road will be:
Dadd + Del in metres, with a minimum clearance of 7 metres The values of Del are given in Table 5.5/ES.1 depending on the highest voltage of the lines
Where: Dadd = 7.5 for special category lines
Dadd = 6.3 for lines of other categories
(A-dev) ES.2 RD 223/2008, ITC-LAT 07, clause 5.9, Crossings with electrified railways, tram and trolley bus lines
Special requirements defined in sub-clause 5.9.1 apply
In crossings involving power lines and electrified railways, trams, and trolleybuses, it is essential to maintain a minimum vertical distance from the power line conductors This distance should account for the maximum vertical sag of the conductors, as specified in clause 5.6, ensuring safety in relation to the highest conductor of all power lines, telephone lines, and telegraph lines.
Dadd + Del = 3,5 + Del in metres, with a minimum of 4 metres The values of Del are given in Table 5.5/ES.1 depending on the highest voltage of the lines
For railways, trams, and trolley buses with trolley systems, power line conductors must be installed at a height that ensures, even when the contact arrangement is disconnected and positioned in the least favorable manner, they do not come closer than the specified distance to the ground.
(A-dev) ES.3 RD 223/2008, ITC-LAT 07, sub-clause 5.11, Crossings with navigable rivers and canals
Special requirements defined in sub-clause 5.9.1 apply
In crossovers involving navigable rivers and canals, the minimum height of conductors, considering the maximum vertical sag based on load cases outlined in clause 5.6, must be maintained above the water's surface at its highest level.
G + D add + D el = G + 3,5 + D el in metres,
G + Dadd + Del = G + 2,3 + Del in metres, where G is the clearance or headroom The values of Del are given in Table 5.5/ES.1 depending on the highest voltage of lines
If no such clearance were defined, this shall be considered equal to 4,7 metres
(A-dev) ES.4 RD 223/2008, ITC-LAT 07, clause 5.10, Crossings with rope ways
Special requirements defined in sub-clause 5.9.1 apply
The crossing of a power line with ropeways or cableways must always be made above them, except for very reasonable justified cases expressly authorized
The minimum vertical clearance between power line conductors, considering maximum sag under load conditions as specified in clause 5.6, and the highest point of ropeways, must account for normal operational fluctuations and potential uplift due to load reduction during an accident.
Dadd + Del = 4,5 + Del in metres, with a minimum of 5 metres The values of Del are given in Table 5.5/ES.1 depending on the highest voltage of the line
The minimum horizontal distance required between the closest section of the ropeway and the power line support in the crossing span must adhere to the value calculated using the specified formula.
The ropeway must be grounded at two points, one on each side of the crossing, in accordance with the requirements of paragraph 6
(A-dev) ES.5 RD 223/2008, ITC-LAT 07, clause 5.8, Crossings with non-electrified railway lines
For the Installation of supports, both in the case of parallelism as in the case of crossings, the following considerations will be taken into account:
A boundary building line is established on both sides of railway lines within the railway network of general interest, prohibiting any building work, refurbishment, or extension from this line to the railway line.
The boundary line for building construction is set 50 meters from the outer edge of the earthwork, measured horizontally and perpendicular to the railway's outer lane Support installations are prohibited within the area impacted by this boundary line.
To ensure the safety of railway lines, it is essential to obtain the necessary authorization from the relevant administrative bodies before placing support within the protection zone This protection zone is defined as extending 70 meters horizontally from the outer edge of the earthwork, measured perpendicularly to the outer lane of the railway.
- In crossings, supports cannot be installed at a distance lower than one and a half times the height of the support from the outer edge of the earthwork
- In exceptional topographical circumstances and after technical justification and Administration approval, the placement of support for distances less than those set may be allowed
The minimum distance from the conductors of the power line to the top of the rails will be the same used for crossings with roads
Special requirements defined in sub-clause 5.9.1 do not apply in case of parallelism
5.9.5 External clearances to adjacent traffic routes
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 5.7, Distance to adjacent roads
Special requirements defined in sub-clause 5.9.1 do not apply in case of parallelism
To install supports in crossings and parallelism, several key considerations must be met For the State Highways Network, supports should be placed behind the building limit line, at least 1.5 times their height from the road's outer edge, with the limit line set at 50 meters for motorways and 25 meters for other roads For roads outside the State Roads Network, installations must adhere to the regulations of the respective Autonomous Community Additionally, regardless of the road's classification, appropriate authorization from the competent administrative bodies is required for placing supports within the affected area.
Motorways, highways, and freeways require a minimum distance of 100 meters from the outer edge of the earthwork, while other roads in the State Road Network need a distance of 50 meters However, under exceptional topographical conditions and with the necessary technical justification and administrative approval, supports may be placed closer than these specified distances, and parallel routes may exceed the established lengths.
(A-dev) ES.2 RD 223/2008, ITC-LAT 07, clause 5.9, Distance to railways, tram and trolley bus lines
Special requirements defined in paragraph 5.9.1 do not apply in case of parallelism
To install supports near railway lines, several key regulations must be observed: a boundary building line is established 50 meters from the outer edge of the earthwork, prohibiting any construction within this area Additionally, support installations within the protection zone, which is 70 meters from the earthwork, require authorization from relevant administrative bodies In crossings, supports must be placed at least one and a half times their height away from the earthwork However, under exceptional topographical conditions and with proper justification, closer installations may be permitted with administrative approval.
(A-dev) ES.3 RD 223/2008, ITC-LAT 07, clause 5.11, Distance to navigable waterways
Special requirements defined in paragraph 5.9.1 do not apply in case of parallelism
To install supports in crossings and parallelism, it is essential to adhere to specific guidelines: supports must be placed 25 meters apart and at least 1.5 times their height from the river channel's edge, corresponding to the maximum flood flow Shorter distances may be permitted with prior authorization from the competent administration Additionally, under exceptional topographical conditions, supports can be installed closer together with appropriate technical justification and administrative approval.
External clearances to other power lines or overhead telecommunication lines
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 5.6.1, Crossings
The line owner must promptly provide essential data, such as conductor type, cross-section, and voltage, to the requesting entity for the crossing This information is crucial for accurate calculations and to prevent errors caused by insufficient data.
Special requirements defined in sub-clause 5.9.1 apply, with the following modifications:
- Condition a): On lines exceeding 30 kV nominal voltage, one joint per conductor may be acceptable on the crossover span
- Condition b): Wooden supports may be used as long as they are fixed to the ground by metallic or concrete stringers
In power line crossovers, the higher voltage line must be installed at a greater height If both lines are of similar voltage, the last line installed should be the higher one Additionally, if it becomes necessary to increase the height of an existing line, the responsibility for modifying that line falls to the new contractor.
Efforts will be made to position the crossover near one of the supports of the upper line, ensuring that the gap between the lower line's conductors and the closest parts of the upper line's supports is maintained at a minimum distance.
D add + D el = 1,5 + D el in metres, with a minimum of:
- 2 metres for lines with nominal voltage up to 45 kV,
- 3 metres for lines exceeding 45 kV and up to 66 kV nominal voltage,
- 4 metres for lines exceeding 66 kV and up to 132 kV nominal voltage,
- 5 metres for lines exceeding 132 kV and up to 220 kV nominal voltage,
For lines with a nominal voltage exceeding 220 kV and up to 400 kV, a clearance of 7 meters is required, taking into account the conductors at their maximum deflection due to wind, as specified in clause 5.6 The allowable values are detailed in Table 5.5 / ES.1, based on the highest voltage of the lower line.
The minimum vertical clearance between the conductors of both lines in the most unfavorable conditions, shall not be less than:
Applying to Dadd the values listed in Table 5.9.6/ES.1
Table 5.9.6/ES.1 – Additional clearances, D add , to other overhead power lines or overhead telecommunication lines
Dadd (m) Distance from the support of the higher line to the crossing point ≤ 25 m
Distance from the support of the higher line to the crossing point > 25 m
Dpp values are listed in Table 5.5 / ES.1 depending on the highest voltage of the line
The minimum vertical clearance between the conductors of the upper line and the ground cables or optical-ground cables (OPGW) of the lower line must not be less than the specified standards.
The equation \$Dadd + Del = 1.5 + Del\$ in meters indicates the relationship between additional distance and existing distance It is essential to obtain the necessary authorization from the relevant administrative bodies for the placement of supports within the affected area, regardless of whether the road is part of the State Highway Network For roads within the State Highway Network, the affected area is defined by a specific distance.
Motorways, highways, and freeways require a minimum distance of 100 meters from the outer edge of the earthwork, while other roads in the State Road Network need a distance of 50 meters However, under exceptional topographical conditions and with the necessary technical justification and administrative approval, supports may be installed closer than these specified distances, and parallel routes may exceed the established lengths.
(A-dev) ES.2 RD 223/2008, ITC-LAT 07, clause 5.9, Distance to railways, tram and trolley bus lines
Special requirements defined in paragraph 5.9.1 do not apply in case of parallelism
To install supports near railway lines, several key regulations must be observed: a boundary building line is established 50 meters from the outer edge of the earthwork, prohibiting any construction within this area Additionally, support installations are not allowed within the boundary line of the building surface For supports in the protection zone, which is 70 meters from the outer edge of the earthwork, authorization from the relevant administrative bodies is required In crossings, supports must be placed at least one and a half times their height away from the outer edge of the earthwork However, under exceptional topographical conditions and with proper justification and administrative approval, supports may be installed closer than these specified distances.
(A-dev) ES.3 RD 223/2008, ITC-LAT 07, clause 5.11, Distance to navigable waterways
Special requirements defined in paragraph 5.9.1 do not apply in case of parallelism
To install supports in crossings and parallelism, it is essential to adhere to specific guidelines: supports must be placed 25 meters apart and at least 1.5 times their height from the river channel's edge, corresponding to the maximum flood flow Shorter distances may be permitted with prior authorization from the competent administration Additionally, under exceptional topographical conditions, supports can be installed closer together with appropriate technical justification and administrative approval.
5.9.6 External clearances to other power lines or overhead telecommunication lines
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, sub-clause 5.6.1, Crossings
The line owner must promptly provide essential data, such as conductor type, cross-section, and voltage, upon request from the entity planning the crossing This information is crucial for accurate calculations and to prevent errors caused by insufficient data.
Special requirements defined in sub-clause 5.9.1 apply, with the following modifications:
- Condition a): On lines exceeding 30 kV nominal voltage, one joint per conductor may be acceptable on the crossover span
- Condition b): Wooden supports may be used as long as they are fixed to the ground by metallic or concrete stringers
In power line crossovers, the higher voltage line must be installed at a greater height If both lines are of similar voltage, the last line installed should be the higher one Additionally, if it becomes necessary to increase the height of an existing line, the responsibility for modifying that line falls to the new contractor.
Efforts will be made to position the crossover near one of the supports of the upper line, ensuring that the gap between the lower line's conductors and the closest components of the upper line's supports is maintained at a minimum distance.
D add + D el = 1,5 + D el in metres, with a minimum of:
- 2 metres for lines with nominal voltage up to 45 kV,
- 3 metres for lines exceeding 45 kV and up to 66 kV nominal voltage,
- 4 metres for lines exceeding 66 kV and up to 132 kV nominal voltage,
- 5 metres for lines exceeding 132 kV and up to 220 kV nominal voltage,
For lines with a nominal voltage exceeding 220 kV and up to 400 kV, a clearance of 7 meters is required, taking into account the conductors at their maximum deflection due to wind, as outlined in hypothesis a) of clause 5.6 The allowable values for clearance are specified in Table 5.5 / ES.1, based on the highest voltage of the lower line.
The minimum vertical clearance between the conductors of both lines in the most unfavorable conditions, shall not be less than:
Applying to Dadd the values listed in Table 5.9.6/ES.1
Table 5.9.6/ES.1 – Additional clearances, D add , to other overhead power lines or overhead telecommunication lines
Dadd (m) Distance from the support of the higher line to the crossing point ≤ 25 m
Distance from the support of the higher line to the crossing point > 25 m
Dpp values are listed in Table 5.5 / ES.1 depending on the highest voltage of the line
The minimum vertical clearance between the conductors of the upper line and the ground cables or optical-ground cables (OPGW) of the lower line must not be less than the specified standards.
Dadd + Del = 1,5 + Del in metres, with a minimum of 2 metres Del values are listed in Table 5.5 / ES.1 depending on the highest voltage of the line
The minimum vertical clearance between the phase conductors of two crossing lines, or between the upper line's phase conductors and the lower line's guard wires, must be verified This verification considers the upper line's phase conductors at maximum sag as specified in the Project Specifications, and the lower line's phase conductors or ground cables at minimum temperature without overload, which is -5°C in zone A, -15°C in zone B, and -20°C in zone C.
External clearances to recreational areas (playgrounds, sports areas, etc.)
(A-dev) ES.1 RD 223/2008, ITC-LAT 07, clause 5.12, and RD 1955/2000
For overhead lines with bare conductors, the flying easement refers to the area of land determined by the ground projection of the outermost conductors, taking into account the conductors and their insulator strings under the most adverse conditions, without factoring in any extra clearance.
The most adverse conditions occur when conductors and their insulator strings are at their maximum deviation, specifically under the influence of their own weight and a wind load equivalent to a wind speed of 120 km/h at a temperature of 15 ºC.
High voltage overhead lines must meet RD 1955/2000 in all matters regarding limitations on the constitution of crossing easement