Second edition. This English-language version is derived from the original bilingual publication by leaving out all French-language pages. Missing. IEC pdf. Transféré par dkoutso Droits d'auteur: Attribution Non- Commercial (BY-NC). Téléchargez comme PDF, TXT ou lisez en ligne sur Scribd. IEC Edition INTERNATIONAL. STANDARD. NORME. INTERNATIONALE. Guidance for the selection of high-voltage A.C. cable systems.
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IEC Guide to the selection of high-voltage cables. IEC Conductors of insulated cables. IEC Tests on cable oversheaths which have a. 20//CDV ® Project number Numéro de projet IEC/TC or SC: Submitted for parallel voting in CENELEC Soumis au vote parallèle au. download your copy of IEC as a PDF download or hard copy directly from the official BSI Shop. All BSI British Standards available online in.
Environmental aspects are mentioned at the level they may influence the selection of high-voltage cables and their application.
For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document including any amendments applies.
It is the highest voltage that can be sustained under normal operating conditions at any time and at any point in a system.
Table 1 gives this information. Note It excludes voltage transients such as those due to system switching and temporary voltage variation due to abnormal system conditions such as those due to fault conditions or sudden disconnection of large loads.
Note Such overvoltages are usually unidirectional and of very short duration. Reference should be made to the relevant IEC publications which deal with many of the following service conditions.
For single-core cables, the current carrying capability depends largely on the screen bonding technique. Special bonding single point bonding or cross-bonding is generally used where bulk transmission has to be achieved, since the amount of losses in metal screens is significantly reduced, compared to solid bonding 2.
However they require special equipments such as surge voltage limiters to protect cable sheaths and accessories from transient overvoltages or earth continuity conductor to be laid along the cable route.
For example, clearance and surrounding insulation should be specified. NOTE A load curve is essential if cyclic loading is considered when determining conductor size. The expected symmetrical and asymmetrical short-circuit currents which may flow in case of short circuits, both between phases and to earth. Maximum time for which short-circuit currents may flow. Individual installations require special consideration. Meteorological data to evaluate risk of soil drying see IEC series e Minimum, maximum and average ground temperature at the depth of burial.
Internal diameter of ducts and pipes. Spacing between individual ducts and pipes, if more than one. Material of ducts or pipes. Cables in air 4. To facilitate the selection of the cable, systems are divided into three categories according to the duration of time the system can be operated under earth fault conditions. This period should, in general, not exceed 1 h, but a longer period can be tolerated as specified in the relevant cable standard.
This category comprises all systems which do not fall into Category A or B. Category A: Category B: Category C: Reference should be made to the relevant cable standards choosing for example between those listed in Clause 2. NOTE It should be realized that in a system where an earth fault is not automatically and promptly isolated, the extra stresses on the insulation of cables during the earth fault reduce the life of the cables to a certain degree.
If the system is expected to be operated fairly often with a permanent earth fault, it may be advisable to classify the system in Category C. U m should be chosen not less than the highest voltage of the three-phase system as defined in 3. Where a standard does not exist for the type of cable to be used, the conductor size should be selected from one of the standard sizes for Class 2 conductors given in IEC In the selection of conductor size, the following factors should be taken into account: a The maximum allowed temperature in the cable under the normal operation see 4.
A small diameter conductor arising from the use of a small cross-sectional area or a thin insulation may result in unacceptably high electric stress in the insulation.
Furthermore appropriate a. Insulation levels for power frequency and impulse voltages will be chosen after consideration of the factors given in Clause 5 and 7. The accessories shall withstand all mechanical and electrodynamic forces that can occur during normal operation and short circuit currents.
Special attention has to be taken for connectors, clamping and systems to restrain thermo mechanical stresses. Accessories designed for U m above 36 kV shall be tested in accordance with the requirements in IEC and IEC as appropriate for the voltage level of the cable system. The quality and performance of any new link or replaced joints and terminations are highly dependent on the skills, competence and workmanship of the jointers who would ensure the proper installation of these accessories under field conditions.
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Wear a smile and have friends; wear a scowl and have wrinkles.The accessories shall withstand all mechanical and electrodynamic forces that can occur during normal operation and short circuit currents. While all reasonable efforts are made to ensure that the technical content of IEC Publications is accurate.
The object of IEC is to promote international co-operation on allquestions concerning standardization in the electrical and electronic fields. Home IEC Ed.
Med Tis. Insulation levels for power frequency and impulse voltages will be chosen after consideration of the factors given in Clause 5 and 7.
Flag for inappropriate content. Cables in air 4. Part 2.
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