high-voltage cables and cable systems; – guidance relates to cables with extruded insulation; – submarine cables are not covered but cables laid in water are covered; – operation of syst
Voltages pertaining to the cable and its accessories
NOTE Cables will henceforth be designated by U 0 /U (U m ) to provide guidance on compatibility with switchgear and transformers Table 1 gives this information
U 0 rated r.m.s power-frequency voltage between each conductor and screen or sheath for which cables and accessories are designed
U rated r.m.s power-frequency voltage between any two conductors for which cables and accessories are designed
Note 1 to entry: This quantity only affects the design of non-radial field cables and accessories
U m maximum r.m.s power-frequency voltage between any two conductors for which cables and accessories are designed
The highest voltage that can be maintained under normal operating conditions at any point in a system is defined, excluding temporary voltage fluctuations caused by fault conditions or the abrupt disconnection of large loads.
U p peak value of the lightning impulse withstand voltage (and switching, where applicable) between each conductor and screen or sheath for which cables and accessories are designed
Voltages pertaining to the system on which cables and accessories are to be
3.2.1 nominal voltage of system r.m.s phase-to-phase voltage by which the system is designated and to which certain operating characteristics of the system are related
3.2.2 highest voltage of three-phase system highest r.m.s phase-to-phase voltage which occurs under normal operating conditions at any time and at any point in the system
Voltage transients caused by system switching and temporary voltage variations resulting from abnormal conditions, such as faults or sudden disconnections of large loads, are not included in this entry.
Lightning overvoltage refers to the phase-to-earth or phase-to-phase overvoltage that occurs at a specific location in a system due to a lightning discharge or other causes For the purpose of insulation coordination, the wave shape of this overvoltage can be considered similar to that of a standard impulse.
Note 1 to entry: See 3.18.3 of IEC 60071-1:2006 and IEC 60071-1:2006/AMD1:2010 used for lightning impulse withstand tests
Note 2 to entry: Such overvoltages are usually unidirectional and of very short duration
Switching overvoltage refers to the phase-to-earth or phase-to-phase overvoltage that occurs at a specific location in a system as a result of a switching operation For the purpose of insulation coordination, the waveform of this overvoltage can be considered similar to that of a standard impulse.
Note 1 to entry: See 3.18.2 of IEC 60071-1:2006 and IEC 60071-1:2006/AMD1:2010 used for switching impulse withstand tests
General
To select the right cable system design for a specific project, it is essential to gather information about the service conditions Consulting the relevant IEC publications is crucial, as they address many of these service conditions.
Operating conditions
The operational conditions for the system include the nominal voltage, the highest voltage of the three-phase system, and considerations for lightning and switching overvoltages for systems with voltages of 300 kV or higher Additionally, the system frequency, type of earthing, and maximum permitted duration of earth fault conditions must be taken into account, especially when the neutral is not effectively earthed Lastly, screen bonding is also a critical factor in these conditions.
For single-core cables, the current-carrying capability depends largely on the screen bonding technique
Special bonding, including single point bonding and cross-bonding, is essential for achieving bulk transmission, as it significantly reduces losses in metal screens compared to solid bonding (refer to IEC 60287-1-1:2006, section 2.3) However, this method necessitates specialized equipment, such as surge voltage limiters to protect cable sheaths and accessories from transient overvoltages, as well as an earth continuity conductor along the cable route Additionally, when terminals are specified, it is crucial to provide the relevant environmental conditions.
– the altitude above sea level, if above 1 000 m;
– whether excessive atmospheric pollution is expected; according to IEC TS 60815-1; – termination in SF 6 switchgear; transformer or metal-clad system, with orientation; following IEC 62271-209;
When connecting cables to equipment such as transformers, switchgear, and motors, it is essential to specify the design clearance and surrounding insulation Additionally, the maximum rated current must be clearly defined to ensure safe and efficient operation.
– for emergency or overload operation, if any, without exceeding maximum allowed cable temperature
A load curve is crucial for determining conductor size, especially in scenarios involving cyclic loading, emergency situations, or overload operations It is important to consider the expected symmetrical and asymmetrical short-circuit currents that may occur during short-circuits, both between phases and to earth Additionally, the maximum duration for which these short-circuit currents can flow and the potential for operation with forced cooling must also be taken into account.
Installation data
General
When planning cable installations, it is essential to consider the length and profile of the route, as well as the specific laying arrangements, such as flat or trefoil configurations Additionally, the connection of metallic coverings to one another and to the earth must be detailed Special laying conditions, such as cables submerged in water, require careful attention to ensure safety and compliance Each installation should be evaluated individually to address these unique considerations.
Underground cables
When planning cable installations, it is essential to consider typical ambient temperatures throughout the year as per IEC 60287-3-1, along with specific installation conditions such as direct burial or mechanical laying This information aids in determining the appropriate composition of metallic screens or sheaths, the necessity of armor, and protective measures against corrosion or termites Additionally, the depth of laying, thermal resistivities, and soil types along the route—whether based on measurements or assumptions—must be evaluated, alongside meteorological data to assess soil drying risks It is also crucial to account for minimum, maximum, and average ground temperatures at the burial depth, as well as the proximity of other load-carrying cables and heat sources Furthermore, details regarding the lengths of troughs, ducts, or pipelines, including manhole spacing, and specifications of ductbanks, such as the number and internal diameter of ducts, spacing, and materials, should be documented Finally, assessing the risk of water ingress and corrosion is vital to ensure the selection of the right cable design.
Cables in air
When considering cable installations, it is essential to account for the minimum, maximum, and average ambient air temperatures The type of installation—whether direct laying on walls, racks, poles, or in boxes, as well as the grouping of cables and dimensions of tunnels, ducts, and vertical shafts—must be specified Additionally, details regarding ventilation for indoor cables or those in tunnels and ducts are crucial It is important to note if the cables will be exposed to direct sunlight or if they will have sun shields Lastly, any special conditions, such as fire risks, flame spread, and the presence of harmful gases and smoke, should be clearly outlined.
Cables in water
When considering cable installation, it is crucial to account for water depth and currents, as well as the chosen installation and laying techniques Additionally, there is a significant risk of mechanical damage from fishing equipment, ice, and abrasion, highlighting the need for effective armouring, fastening, and trenching Proper methods for fastening, protecting, and installing the cable at the shore, including clamping, trenching, and tubing, are essential Finally, selecting the appropriate cable design is vital to mitigate risks of water ingress and corrosion.
Introductory remark
The cable's rated voltage must align with the operating conditions of its application To aid in cable selection, systems are classified into three categories based on the duration they can function under earth fault conditions.
System categories
This category comprises those systems in which any phase conductor that comes in contact with earth or an earth conductor is disconnected from the system within 1 min – Category B
This category includes systems that operate with one phase earthed under fault conditions for a limited duration, typically not exceeding 1 hour, although longer periods may be permissible as outlined in the applicable cable standards.
This category comprises all systems which do not fall into category A or B
Reference should be made to the relevant cable standards choosing, for example, between those listed in Clause 2
In systems lacking automatic and timely isolation of earth faults, the additional stress on cable insulation can significantly shorten their lifespan For systems anticipated to operate frequently with a persistent earth fault, it is recommended to categorize the system as category C.
Selection of U m
U m should be chosen not less than the highest voltage of the three-phase system as defined in 3.2.2
Selection of U p
The selected value of U p must meet or exceed the lightning impulse withstand voltage, as well as the switching voltage when relevant, as specified in IEC 60071-1 This selection should consider the line insulation levels, system protective levels, surge impedance of overhead lines and cables, cable lengths, and the distance from the flashover point to the terminal.
6 Selection of the conductor size
When selecting conductor sizes for cable construction, it is essential to choose from the standard sizes outlined in the relevant standards In cases where no specific standard exists for the cable type, the conductor size should be selected from the standard sizes for class 2 conductors as specified in IEC 60228.
When selecting the appropriate conductor size, it is essential to consider the maximum permissible temperature of the cable during normal operation and under short-circuit conditions.
The IEC 60287 and IEC 60853 series outline calculation procedures for various load conditions, addressing mechanical loads on cables during installation and operation It is crucial to consider the electrical stress on insulation surfaces, particularly for accessories, as small diameter conductors can lead to excessive electric stress due to reduced cross-sectional area or thin insulation Additionally, optimizing cable economics involves evaluating initial investment costs alongside future energy loss expenses, as detailed in IEC 60287-3-2 For cables with large conductor cross sections (S > 1,600 mm²) used in bulk power transmission, selecting the appropriate conductor requires consideration of skin and proximity effects, along with conducting a.c measurements to verify calculated resistance values.
General
The design of accessories is influenced by the necessary power-frequency and impulse withstand voltages, which may differ from those needed for the cable Insulation levels for these voltages are selected based on the considerations outlined in Clause 5 and 7.2.2.
The accessories must endure all mechanical and electrodynamic forces encountered during normal operation, including short-circuit currents It is crucial to focus on the durability of connectors, clamping systems, and mechanisms designed to mitigate thermo-mechanical stresses.
Accessories designed for U m above 1 kV and up to 36 kV shall be tested in accordance with the requirements in IEC 60502
Accessories designed for U m above 36 kV shall be tested in accordance with the requirements in IEC 60840 and IEC 62067 as appropriate for the voltage level of the cable system
The effectiveness and durability of newly installed or replaced joints and terminations rely significantly on the expertise and craftsmanship of the jointers responsible for their installation in the field.
Systematic and compulsory training is required by all high-voltage jointers to acquire and confirm the necessary skills.
Terminations
General
The design of terminations depends upon the degree of exposure to atmospheric pollution (see IEC TS 60815-1) and the altitude at the position of the termination.
Atmospheric pollution
The degree of exposure to atmospheric pollution determines the minimum creepage distances and the type of insulators to be used for cable sealing ends.
Altitude
At high altitudes, air density decreases compared to sea level, leading to reduced electric strength and potentially inadequate air clearances While the puncture strength and oil flashover values of terminations remain unaffected by altitude, terminations that pass the impulse withstand test under standard conditions are suitable for altitudes below 1,000 m To meet requirements at higher altitudes, it is essential to increase the specified air clearances accordingly.
Joints
The type of conductor joint utilized is dictated by the joint design, with options including pre-molded, pre-fabricated, taped, or field molded joints The selection of the appropriate joint type is influenced by factors such as installation conditions, time constraints, and the mechanical, electrical, and economic properties, as well as material compatibility.
Special designs are used for cross bonding systems
Early consideration of environmental factors is crucial when planning a high-voltage cable connection Specific requirements should be communicated to designers from the outset of both system and product design to ensure informed decision-making.
Environmental aspects may cover, but are not limited to, the following items:
When selecting a high-voltage system, it is crucial to consider the general design principles in relation to its environmental location This includes assessing the system's impact on the surrounding landscape and local population, ensuring operational safety under both normal and fault conditions, and providing security against atmospheric influences Additionally, it is important to evaluate acceptable fault localization and repair times in the event of a malfunction, as well as the implications during the installation process.
– information about international, regional or national regulated substances so that those for which restrictions apply, can be avoided or reduced to a minimum within all parts and components of cable;
The production process prioritizes the elimination of hazardous raw materials, such as lead, and focuses on utilizing alternative technical solutions in construction components when available This approach ensures that the necessary product performance is achieved without the need for harmful substances.
Optimizing material consumption in product and system design involves avoiding excessive mechanical sizing based on operational environment conditions For instance, the necessity for armor should be determined by the actual risk of external failures rather than traditional assumptions.
– product information availability related to option to recycle used materials after their completed life time, either for further re-use or for energy waste processing without hazardous substances;
– option to use recyclable delivery materials, like returnable or recyclable cable drums and accessory packages;
– reference to an environmental management system, e.g ISO 14000, in component and system production requirements
Table 1 – Relationship between U 0 / U and ( U m ) and impulse voltages
Rated voltage of cables and accessories
Nominal system voltage Highest voltage for equipment Lightning impulse voltage for equipment
Switching impulse voltage for equipment
U 0 U U m U p U p kV kV kV kV kV
Other voltage levels may be used For such systems, the values of U, U 0 , U m together with impulse voltages should be clearly given, for instance 52/90 (100) – lightning impulse 450 kV
A high-voltage cable line may be monitored mainly for two purposes:
– for optimal or maximum applicable current-carrying capacity by measuring cable temperature along cable route;
– for cable system insulation condition investigation by PD measurements
Cable temperature measurement can be performed using an optical fiber embedded within the cable construction, such as in the metallic screen area, along with a monitoring computer equipped with suitable software to analyze the cable's temperature profile The need for a cable temperature monitoring system, when an optical fiber is included in the cable design, should be clearly outlined in the technical specifications for the specific cable type being ordered The decision to utilize this integrated temperature measurement optical fiber can be made at the initial stage or postponed for future requirements.
Monitoring the condition of cable and cable system insulation can be effectively achieved through partial discharge (PD) measurement technology, which identifies local defects For effective cable system monitoring, initial PD measurement results serve as a baseline, and subsequent measurements should be compared to these initial results to detect any significant changes.
An initial system PD measurement made directly after installation may not only give a basic value for further measurements, but also give an indication of the level of completed installation
A system monitoring approach is essential for assessing the optimal current-carrying capacity and evaluating the condition of cable systems through partial discharge (PD) measurements, emphasizing the significance of the cable line's importance.
IEC 60853 (all parts), Calculation of the cyclic and emergency current rating of cables
IEC TR 62602, Conductors of insulated cables – Data for AWG and KCMIL sizes
3.1 Tensions propres du câble et de ses accessoires 20
3.2 Tensions propres au réseau sur lequel le câble et ses accessoires doivent être utilisés 21
6 Choix de la section du conducteur 24
Annexe A (informative) Surveillance du réseau 28
Tableau 1 – Relation entre U0/U et (Um) et tensions de choc 27
LIGNES DIRECTRICES POUR LE CHOIX DE SYSTÈMES
DE CÂBLES À HAUTE TENSION EN COURANT ALTERNATIF
The International Electrotechnical Commission (IEC) is a global standards organization comprising national electrotechnical committees Its primary goal is to promote international cooperation on standardization issues in the fields of electricity and electronics To achieve this, the IEC publishes International Standards, Technical Specifications, Technical Reports, Publicly Available Specifications (PAS), and Guides, collectively referred to as "IEC Publications." The development of these publications is entrusted to study committees, which allow participation from any national committee interested in the subject matter Additionally, international, governmental, and non-governmental organizations collaborate with the IEC in its work The IEC also works closely with the International Organization for Standardization (ISO) under conditions established by an agreement between the two organizations.
The official decisions or agreements of the IEC on technical matters aim to establish an international consensus on the studied topics, as the relevant national committees of the IEC are represented in each study committee.
The IEC publications are issued as international recommendations and are approved by the national committees of the IEC While reasonable efforts are made to ensure the technical accuracy of the content, the IEC cannot be held responsible for any misuse or misinterpretation by end users.
To promote international uniformity, IEC National Committees strive to transparently implement IEC Publications in their national and regional documents Any discrepancies between IEC Publications and corresponding national or regional publications must be clearly stated in the latter.
The IEC does not issue any conformity certificates itself Instead, independent certification bodies offer compliance assessment services and, in certain sectors, utilize IEC conformity marks The IEC is not responsible for any services provided by these independent certification organizations.
6) Tous les utilisateurs doivent s'assurer qu'ils sont en possession de la dernière édition de cette publication
The IEC, along with its directors, employees, agents, and committee members, shall not be held liable for any injuries, damages, or costs arising from the publication or use of this IEC Publication or any other IEC Publication, including legal fees and expenses.
8) L'attention est attirée sur les références normatives citées dans cette publication L'utilisation de publications référencées est obligatoire pour une application correcte de la présente publication
It is important to note that some elements of this IEC publication may be subject to patent rights The IEC cannot be held responsible for failing to identify such patent rights or for not disclosing their existence.
La Norme internationale IEC 60183 a été établie par le comité d'études 20 de l’IEC: Câbles électriques
Cette troisième édition annule et remplace la deuxième édition, parue en 1984, et son Amendement 1 (1990) La présente édition constitue une révision technique
Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
– le domaine d'application a été modifié pour traiter des câbles et systèmes de câbles à haute tension en courant alternatif;
– les lignes directrices sont relatives aux câbles avec isolation extrudée;
– les câbles sous-marins ne sont pas couverts, mais les câbles posés dans l'eau sont couverts;
– l'exploitation des systèmes avec connexion spéciale de l'écran est couverte;
– des directives relatives aux accessoires sont fournies;
– les aspects environnementaux sont traités
Le texte de cette norme est issu des documents suivants:
Le rapport de vote indiqué dans le tableau ci-dessus donne toute information sur le vote ayant abouti à l'approbation de cette norme
Cette publication a été rédigée selon les Directives ISO/IEC, Partie 2
Tensions propres du câble et de ses accessoires
NOTE Les câbles seront désormais désignés par U 0 /U (U m ) pour donner une information sur la compatibilité avec l'appareillage et les transformateurs Le Tableau 1 donne cette information
U 0 tension assignée efficace à fréquence industrielle, entre chaque âme et l'écran ou la gaine, pour laquelle le cõble et ses accessoires sont conỗus
U tension assignée efficace à fréquence industrielle, entre deux quelconques des âmes conductrices, pour laquelle le cõble et ses accessoires sont conỗus
Note 1 à l'article: Cette grandeur ne présente d'intérêt que pour les câbles à champ non radial et les accessoires
3.1.3 tension la plus élevée du réseau
U m tension maximale efficace à fréquence industrielle, entre deux quelconques des âmes conductrices, pour laquelle le cõble et ses accessoires sont conỗus
The maximum voltage value that can be sustained under normal operating conditions at any moment and in any part of the network is defined This value does not account for temporary voltage fluctuations caused by fault conditions or the sudden removal of significant loads.
3.1.4 crête de la tension aux choc
The peak withstand voltage for lightning and switching surges, when applied between each core and the screen or sheath, is specified for which the cable and its accessories are designed.
Tensions propres au réseau sur lequel le câble et ses accessoires doivent être utilisés
3.2.1 tension nominale du réseau valeur efficace de la tension entre phases pour laquelle le réseau est établi et à laquelle sont relatives certaines conditions de service
The highest voltage in a three-phase network refers to the maximum effective voltage that can occur between phases under normal operating conditions, at any moment and at any point within the network.
Note 1 to the article: It excludes transitional tension regimes (such as those caused by maneuvers) and temporary variations due to abnormal operating conditions (such as those resulting from faults or the sudden removal of significant loads).
Lightning overvoltage, whether phase-to-ground or phase-to-phase, occurs at a specific point in a network due to a lightning strike or another cause The waveform of this overvoltage can be regarded, for insulation coordination purposes, as similar to that of a standardized shock wave.
Note 1 à l'article: Voir 3.18.3 de l'IEC 60071-1:2006 et de l'IEC 60071-1:2006/AMD1:2010 utilisée pour les essais de tenue aux chocs de foudre
Note 2 à l'article: De telles surtensions sont en général unidirectionnelles et de très courte durée
3.2.4 Maneuver overvoltage refers to the phase-to-ground or phase-to-phase overvoltage at a specific location in a network caused by a maneuver within the system This overvoltage waveform can be regarded, for insulation coordination purposes, as being similar to that of a standardized shock wave.
Note 1 à l'article: Voir 3.18.2 de l'IEC 60071-1:2006 et de l'IEC 60071-1:2006/AMD1:2010 utilisée pour les essais de tenue aux chocs de manœuvre
Généralités
To identify the most suitable cable system for a specific project, it is essential to gather information about the service conditions Relevant IEC publications should be consulted, as they address several of these service conditions.
Conditions de fonctionnement
The following operating conditions apply: a) nominal network voltage, b) maximum voltage of the three-phase network, c) lightning overvoltage and switching overvoltage for higher voltage levels (U m ≥300 kV) of the networks (refer to Table 1), d) network frequency, e) grounding type, and when the neutral is not effectively grounded, the maximum allowable duration for earth fault conditions at any time and their total annual duration, f) screen connection.
Pour les câbles à un seul conducteur, le courant admissible dépend fortement de la technique de connexion de l'écran
A special connection, either single-point grounding or permutation, is typically employed for large-scale transport to significantly reduce losses in metal screens compared to direct connections (refer to IEC 60287-1-1:2006, section 2.3) However, this method requires specialized equipment, such as surge voltage limiters to protect cable sheaths and accessories from transient overvoltages, or a grounding conductor to be installed along the cable route Additionally, when terminations are planned, environmental conditions must be specified.
– altitude au-dessus du niveau de la mer, si elle est supérieure à 1 000 m;
– risque de pollution atmosphérique excessive; selon l’IEC TS 60815-1;
– extrémité en appareillage sous SF 6 ; transformateur ou système recouvert de métal, avec l'orientation;selon l’IEC 62271-209;
The article discusses the spacing and insulation requirements for connecting cables to equipment such as transformers, devices, and motors It emphasizes the importance of specifying the necessary clearances and additional insulation Additionally, it addresses the maximum rated current for these connections.
– en régime de surcharge ou de dépannage, s'il y a lieu, sans dépassement de la température maximale autorisée du câble
A load diagram is crucial for accounting for periodic variations in load, overload, or troubleshooting when determining the conductor size It is important to consider both predictable symmetrical and asymmetrical short-circuit currents that may occur between phases and between a phase and ground Additionally, the maximum duration of short-circuit currents must be assessed, along with the potential for operation with forced cooling.
Conditions d'installation
Généralités
The following data applies: a) Length and profile of the route b) Details of cable installation methods (such as flat or trefoil arrangements) and the connection modes of metallic coverings to each other and to the ground c) Special installation conditions, such as cables submerged in water Specific installations require a dedicated study.
Câbles souterrains
The following data is essential for cable installation: a) Typical ambient temperatures throughout the year (refer to IEC 60287-3-1) b) Installation conditions, such as direct burial, conduit placement, or mechanical installation, which influence the choice of screen or metallic sheath, armor type (if required), and external mattress type (e.g., anti-corrosion or anti-termite) c) Burial depth d) Thermal resistivity and soil type along the route (e.g., sand, clay, fill material); specify if these details are based on measurements or assumptions Meteorological data is needed to assess soil drying risk (see IEC 60287 series) e) Minimum, maximum, and average soil temperatures at the cable burial depth f) Proximity to other energy transport cables or heat sources, especially when multiple parallel circuits are involved g) Lengths of ducts, conduits, or pipes, including distances between junction chambers, if applicable h) Details of multi-tubular pipelines, if any: number of conduits or tubes, inner diameter, spacing between them, and material composition i) Risk of water ingress or corrosion, necessitating the selection of the appropriate cable type.
Câbles à l'air
The following data applies: a) Accepted minimum, maximum, and average temperatures for ambient air b) Installation methods, such as direct placement along walls, on shelves, on poles, or within boxes, as well as cable grouping, tunnel dimensions, conduit sizes, and vertical trees c) Ventilation details for cables located inside buildings, in tunnels, or conduits d) Potential direct exposure to sunlight or the presence of a sunshade e) Special conditions, including fire risk, fire spread, harmful gases, and smoke.
Câbles dans l'eau
The following data is essential for installation: a) water depth and currents; b) installation techniques; c) potential mechanical damage during service caused by fishing equipment, ice, abrasion, etc., highlighting the need for shielding, anchoring, and burial; d) methods for securing, protecting, and installing the cable at the shoreline, including tightening, burial, tubing, and the necessity of armor; e) risks of water ingress or corrosion, emphasizing the importance of selecting the correct type of cables.
Remarques introductives
The assigned tension of the cable for a specific application must be suitable for the operating conditions of the network in which it is utilized To simplify cable selection, networks are classified into three categories based on the duration they can operate under ground fault conditions.
Catégories de réseaux
This category includes networks where any phase conductor that comes into contact with the ground or a ground conductor is disconnected from the system within a maximum of 1 minute.
This category includes networks that, in the event of a fault, operate with a ground phase for a limited time Typically, this operation should not exceed 1 hour; however, a longer duration may be permitted if specified in the applicable standard for the type of cable in question - Category C
Cette catégorie comprend tous les réseaux qui ne tombent ni dans la catégorie A ni dans la catégorie B
Il convient de faire référence aux normes applicables au type de câble considéré en les choisissant, par exemple, parmi celles énumérées à l'Article 2
In a network where a ground fault is not isolated quickly and automatically, the additional stresses on cable insulation during the fault duration can significantly reduce the cables' lifespan If the network is expected to frequently operate with a permanent ground fault, it is advisable to classify this network as category C.
Choix de U m
Il convient que la valeur U m soit choisie supérieure ou égale à la tension la plus élevée du réseau triphasé telle que définie en 3.2.2
Choix de U p
The value of U p should be selected to be greater than or equal to the lightning impulse withstand voltage (and, if applicable, the switching impulse withstand voltage) specified by IEC 60071-1, taking into account the line insulation levels, network protection levels, wave impedance of overhead lines and cables, cable lengths, and the distance from the struck point to the end.
6 Choix de la section du conducteur
It is essential to select the conductor cross-section from the standardized sections specified in the applicable cable standard If no standard exists for the type of cable to be used, the conductor cross-section should be chosen from the standardized sections for Class 2 conductors as outlined in IEC 60228.
When selecting the conductor cross-section, it is essential to consider the following factors: a) the maximum permissible temperature in the cable under normal operating conditions (refer to section 4.2 h) and during short-circuit events.
The IEC 60287 and IEC 60853 series provide detailed calculation procedures for various load conditions Mechanical stresses imposed on cables during installation and service, as well as electrical stress on the surface of the insulation (especially for accessories), are critical considerations A small diameter conductor resulting from a low cross-section or thin insulation can lead to unacceptable high electrical stress within the insulation Economic optimization of cables must account for initial investment costs and future energy loss expenses over the cable's lifespan, as outlined in IEC 60287-3-2 For cables with very large conductor cross-sections (S > 1,600 mm²) used for bulk energy transport, the most suitable conductor must be selected based on appropriate skin and proximity effect values, and AC measurements should be conducted to verify calculated resistance values.
Généralités
The design of accessories is influenced by the required voltage withstand levels for industrial frequencies and shock conditions, which may differ from those needed for the cable itself The isolation levels for industrial frequency and shock voltages will be determined after analyzing the factors outlined in Article 5 and section 7.2.2.
Accessories must withstand all mechanical and electrodynamic forces that may occur during normal operation, as well as short-circuit currents Special attention should be given to connectors, clamping systems, and mechanisms to manage thermomechanical stresses.
Les accessoires conỗus pour fonctionner à des valeurs de U m supộrieures à 1 kV et à 36 kV doivent être soumis à essai conformément aux exigences de l'IEC 60502
Accessories designed to operate at voltage levels exceeding 36 kV must undergo testing in accordance with the requirements of IEC 60840 and IEC 62067, depending on the cable system's voltage level.
The quality and performance of any new connections or replaced joints and outlets heavily rely on the skill, expertise, and craftsmanship of the installers responsible for their proper installation in field conditions.
Une formation systématique et obligatoire est requise par tous les poseurs de haute tension pour acquérir et confirmer les compétences nécessaires.
Extrémités
Généralités
La conception des extrémités dépend du degré d'exposition à la pollution atmosphérique (voir l'IEC TS 60815-1) et de l'altitude ó se trouve la position de l'extrémité.
Pollution atmosphérique
Le degré d'exposition à la pollution atmosphérique détermine les lignes de fuite minimales et le type d'isolateur à utiliser pour les extrémités des câbles
Air density decreases at high altitudes compared to sea level, leading to a reduction in the dielectric strength of air Consequently, distances that are adequate at sea level may be insufficient at higher altitudes However, the puncture resistance values of insulators and the tracking resistance of end oils remain unaffected by altitude End fittings that pass the required shock wave test under standardized atmospheric conditions are suitable for altitudes below 1,000 meters To ensure adequate performance at higher altitudes, it is essential to increase the specified air distances by an appropriate amount.
Jonctions
The design of the joint dictates the type of conductor connection to be utilized Factors such as installation conditions, time required for setup, mechanical, electrical, and economic properties, as well as material compatibility, influence the choice of joint—whether it be pre-molded, prefabricated, ribbon, or field-cast.
Des types spéciaux sont utilisés pour les systèmes à permutation
It is essential to consider the environmental aspects related to the planned connection of high-voltage cables early in the network definition stage Specific and well-defined requirements should be provided to designers from the initial phase of network and product design to promote informed decision-making.
Les aspects environnementaux peuvent couvrir les éléments suivants, sans que cela soit limitatif:
When designing high-voltage networks, it is essential to consider a general principle that relates to the network's location within its environment This includes assessing its impact on the landscape and nearby populations, ensuring operational safety under normal and fault conditions, and addressing safety concerns related to atmospheric influences Additionally, the design must account for acceptable locations and durations for repairs of potential faults, as well as the overall impact during installation.
Information regarding substances regulated at international, regional, or national levels is essential to ensure that those subject to restrictions are minimized or avoided in all parts and components of the cable.
To prevent the use of hazardous raw materials in production, such as lead, it is essential to adopt alternative technical solutions when available or when these materials are not necessary to achieve the required product performance.
Optimizing material consumption in product and system design involves avoiding unnecessary mechanical over-sizing based on environmental operating conditions; for instance, the need for reinforcement should be determined by the actual risk of external failure rather than traditional practices Additionally, it is crucial to provide information about products and the recycling options for materials used after their lifecycle, facilitating future reuse or energy recovery from waste without hazardous substances.
– option pour utiliser les matériaux de livraison recyclables, comme les tourets de câbles restituables ou recyclables et les emballages d'accessoires;
– référence à un système de management environnemental, par exemple ISO 14000, dans des exigences relatives à la production des composants et des systèmes
Tableau 1 – Relation entre U 0 / U et ( U m ) et tensions de choc
Tension assignée des câbles et accessoires
Tension nominale du réseau Tension la plus élevée pour l'équipement
Tension de choc de foudre pour l'équipement
Tension de choc de manœuvre pour l'équipement
U 0 U U m U p U p kV kV kV kV kV
D'autres niveaux de tension peuvent être utilisés Pour de tels réseaux, il convient de donner clairement les valeurs de U, U 0 , U m accompagnées des tensions de choc, par exemple: 52/90
Une ligne en câbles à haute tension peut être surveillée principalement pour deux objectifs:
– la valeur maximale ou optimale du courant admissible applicable en mesurant les températures des câbles le long du chemin de câbles;
– l'investigation de l'état de l'isolation du réseau de câbles par des mesures de décharges partielles (DP)
The temperature measurement of a cable can be achieved using an optical fiber embedded within the cable's construction, such as in the metallic shielding area, along with a monitoring computer equipped with the appropriate software to read the thermal profile of the line It is essential to specify the requirement for a temperature monitoring system in the technical specifications for the type of cable to be ordered if an integrated optical fiber is included The decision to incorporate such an integrated optical fiber for temperature measurement during actual operation can be made at the initial stage or deferred for future needs.
The condition of cable insulation and cable systems can be monitored using partial discharge (PD) measurement technology to identify local defects For effective cable system monitoring, initial PD measurement results are essential as a baseline Subsequent measurements should be compared to these initial results to determine if significant changes have occurred An initial PD measurement taken immediately after installation not only provides a baseline for future assessments but also indicates the level of completion of the installation.
It is essential to establish a monitoring system for optimal allowable current or to assess the condition of cable networks through DP measurements, based on the significance of the cable line.
IEC 60853 (toutes les parties), Calcul des capacités de transport des câbles pour les régimes de charge cycliques et de surcharge de secours
IEC TR 62602, Âmes des câbles isolés – Informations relatives aux sections exprimées en AWG et KCMIL