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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Please contact the Customer Service Centre see below for further information. This second edition cancels and replaces the first edition published in and amendment 2 If the post-set short circuit is used, the voltage shall not exceed 1,15 times the rated voltage of the winding, unless otherwise agreed between the manufacturer and the purchaser.
General requirements for basic safety and essential performance. IEC Series moving and fixed: It describes the calculation procedures used to demonstrate the thermal ability of a power transformer to withstand such overcurrents and both the special test and the 6006-5 method used to demonstrate its ability to withstand the relevant dynamic effects.
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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 fields. NOTE 2 Random gas-and-oil-actuated relay tripping may occur during ied tests due to vibration.
This increase in current should be taken into consideration when calculating the temperature rise of iev zigzag winding. Special testing circuits are often necessary in order to reproduce some of the fault events by means of tests.
For categories I and II three-phase transformers, the total number of tests shall be nine, i.
General requirements for basic safety and essential performance IEC Safety of power transformers, power supplies, reactors and similar products Part 1: The testing arrangements, the current values, the sequence and the number of tests are always subject to agreement between the manufacturer and the purchaser. In this case, provision should be made by the purchaser to limit the overcurrent to the 60076-55 value determined by the manufacturer and stated on the rating plate.
NOTE It may not be economical to design auxiliary windings to withstand short circuits on their terminals. These procedures and reactance limits are given in the following items a and b.
In the case of single-phase transformers connected to form a three-phase bank, the stabilizing winding shall be capable of withstanding a short-circuit on its terminals, unless the purchaser specifies that special precautions will be taken to avoid the risk of line-to-line short circuits. The oscillograph can be set to record the phase currents.
Ability to withstand short circuit YEAR. 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 It is recommended that the tolerance on the agreed test current values and the 60706-5 of the tests are in line with those prescribed for two-winding transformers and that the test sequence is selected 6076-5 to the expected increase of electrodynamic forces.
Safety of power transformers, power supply units and similar Part U and Z t are defined as follows: The manufacturer and the purchaser should agree which kind of short circuit is to be considered.
The short-circuiting of the winding may either follow post-set short circuit or precede pre-set short circuit the application of the voltage to the other winding of the transformer 4. The single-phase voltage during the test shall be equal to voltage between phases during the three-phase test. All International European Italian Selector: To make sure that we continue to meet your needs, your feedback is essential. For transformers of category III, an agreement between the manufacturer and the purchaser is always needed with regard to the number of tests and the position of the tap-changer.
NOTE The mounting of accessories having no influence on the behaviour during short circuit e.
However, in order to simulate as closely as possible the effects of repetitive short-circuit events likely to occur in service, to allow a better monitoring of the behaviour of the unit under test and to permit a meaningful judgement in connection with possible variations of the measured short-circuit impedance, it is recommended that the number of tests is as follows: Please, select your language.
NOTE 2 Generally, the 600765 reactance variation should show a tendency to diminish in the course of the tests.
A report containing the result of the routine isc shall be available at the beginning of shortcircuit tests. With regard to tap-changer position and test sequence, the same procedure as described for transformers of categories I and II is recommended.
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 06076-5 transformers see 3. Missing page numbers correspond to the Frenchlanguage pages. There may be also a certain change of reactance with time after the tests.
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International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. In this case, the factor k is found from oscillograms of the line ifc.
When a short-circuit test is selected, it shall be regarded as a special test, see 3. Reference number IEC Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with ic participate in this preparatory work.
Particular requirements and tests for auto transformers and power supply units incorporating auto transformers IEC Safety of power transformers, power supply units and similar Part Medical electrical equipment Part 1: