Telephone: +41 22 02 11 Telefax: +41 22 03 00 E-mail: [email protected] Web: INTERNATIONAL. STANDARD. IEC. Third edition. This part of IEC identifies the requirements for power transformers to sustain without damage the effects of overcurrents originated by external short. IEC. Second edition. This English-language version is As from 1 January all IEC publications are issued with a designation in the.
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The object of the IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic idc.
Account shall be taken of the different forms of system faults that can arise in service, for example line-to-earth faults and line-to-line faults associated with the relevant system and transformer earthing conditions; see IEC General requirements for basic safety and essential performance.
NOTE For auto-transformers and for transformers with short-circuit current exceeding 25 times the rated current, a short-circuit current duration below 2 s may be adopted by agreement between the manufacturer and the purchaser. On-line information is also available on recently issued publications, withdrawn and replaced publications, as well as corrigenda.
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In this case, the factor k is found from oscillograms of the line currents. Particular requirements and tests for safety isolating transformers and power supply units incorporating safety isolating transformers. All International European Italian Selector: However, the on-load tap-changer is not required to be capable of switching the short-circuit current.
In this case, a more detailed examination may lec required, including a dismantling of the unit as necessary to establish the cause of the deviation. Any divergence between the IEC Standard and the corresponding national or regional standard shall be clearly indicated in the latter. However, for transformers of category I, the repetition of the routine tests with the exception of the dielectric tests may be omitted.
INTERNATIONAL STANDARD IEC 60076-5
Ability to withstand short circuit YEAR. These procedures and reactance limits are given in the following items a and b. In these cases, the testing conditions shall be agreed between the purchaser and the manufacturer.
The test shall be carried out in accordance with the requirements in 4. Particular requirements for separating transformers for general use.
MBOX Series for construction site. These characteristics shall be specified by the purchaser in his enquiry. NOTE In the case of winding in zigzag connection, the single-line-to-earth fault current may reach values lec than the three-phase short-circuit current.
Please contact the Customer Service Centre see below for further information. This procedure requires that the voltage of the test supply is suitably adjusted with respect to the rated voltage of the transformer.
This aspect shall be taken into consideration when arranging the test 6076-5 for transformers of category I.
Table 2 — Short-circuit apparent power of the system Highest voltage for equipment, U m Short-circuit apparent power kV MVA Current European practice 7,2; 12; 17,5 and 24 36 52 and 72,5 and and 1 3 6 10 20 30 35 40 60 83 Current North American practice 1 5 15 15 25 30 35 40 60 83 NOTE If not specified, a value between 1 and 3 should be considered for the ratio of zero-sequence to positive-sequence impedance of the system.
For categories I and II three-phase transformers, the total number of tests shall be nine, i. To make sure that we continue to meet your needs, your feedback is essential. NOTE 1 At the end of the tests, if the windings are provided with tapping, the reactance must be measured for all the tapping positions at which the short-circuit tests have been carried out.
Delta-connected stabilizing windings of three-phase transformers shall be capable of withstanding the overcurrents resulting from different forms of system faults that can arise in service associated with relevant system earthing conditions. In order to consider the transformer as having passed the short-circuit test, the following conditions shall be fulfilled: In order to consider the transformer as having passed the short-circuit tests, the following conditions shall be fulfilled: The requirements apply to transformers as defined in the scope of IEC One of the methods of determining the factor k is by switching on during the preliminary adjustment tests at a maximum of the line-to-line voltage.
Consolidated editions The IEC is now publishing consolidated versions of its publications. NOTE 1 Additional means of detection may be used to obtain information and improve the evaluation of the test event, such as recording of the current between the tank insulated and earth, recordings of noise and vibrations, recordings of oil pressure variations occurring at different locations inside the tank during short-circuit current flow, etc.
However, before dismantling, it is suggested that additional diagnostic means are applied see note 1 of 4. The choice of method of demonstration to be used shall be subject to agreement between the purchaser and the manufacturer prior to placing the order.
Notice of any abnormal operation conditions expected in the system s shall be given by the purchaser to the manufacturer in advance. External short circuits are not restricted to three-phase short circuits; they include line-to-line, double-earth and line-to-earth faults. This second edition cancels and replaces the first edition published in and amendment 2 Nevertheless, if agreed between the purchaser and the manufacturer, it is permissible to test 60 Hz transformers with a 50 Hz power supply and 50 Hz transformers with a 60 Hz power supply provided that the prescribed test current values, as required in 4.
For categories I and II single-phase transformers, the number of 600776-5 shall be three. For other transformers with star-zigzag connection, the method of switching on is subject to agreement between the manufacturer and the purchaser.
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The winding closer to the core is to be short-circuited in order to avoid saturation of the magnetic core which could lead to an excessive magnetizing current superimposed on the short-circuit current during the first few cycles. Scame solutions for charging systems. NOTE 3 If, for star-connected windings, the power supply is insufficient for the single-phase testing described above and the neutral is available, the manufacturer and the purchaser may agree upon the use of single-phase power supply between line terminal and the neutral, provided that neutral is capable of carrying the relevant current.
In general, such conditions are of a more complex nature in comparison with the three-phase short circuit which can be considered the reference case for two-winding transformers see 3. Application guide IEC Safety of power transformers, power supplies, reactors and similar products Part 1: International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation.
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Information on the subjects under consideration and work in progress undertaken by the technical committee which has prepared this publication, as well as the list of publications issued, is also available from the following: Particular requirements and tests for control transformers and power supplies incorporating control transformers IEC Safety of transformers, reactors, power supply units and similar products for supply voltages up to 1 V Part The manufacturer and the purchaser should agree which kind of iex circuit is to be considered.
Documents Flashcards Grammar checker. If the pre-set short circuit is used for a transformer with single-concentric windings, the supply should preferably be connected to the winding further from the core.