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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Unless otherwise specified, the nine tests on a three-phase transformer with tappings are made in different positions of the tap changer, i. International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. Ability to withstand short circuit 1 Scope This part of IEC identifies the requirements for power transformers to sustain without damage the effects of overcurrents originated by external short circuits.
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 660076-5 with relevant system earthing conditions.
A report containing the result of the routine tests shall be available at the beginning of shortcircuit tests.
NOTE 2 For star-connected windings with non-uniform insulation, it is necessary to check whether or not the insulation of the neutral is sufficient for single-phase testing. Particular requirements and tests for isolating transformers and power supply units incorporating isolating transformers IEC Safety of transformers, reactors, power supply units and similar products for supply voltages up to 1 V Part The factor k accounts for the initial offset of the test current and to-r.
The results of the short-circuit reactance 600076-5 and the oscillograms taken during the different stages of the tests shall be examined for any indication of possible anomalies during the tests, especially any indications of change in the short-circuit reactance.
Table of physical and chemical constants — Kay and Laby — 15 edition, Longmans, With this test arrangement, it might be convenient to mutually connect the corresponding terminals of the phases not submitted to test in order to better control their voltage, provided that this is feasible and circuitry correct. NOTE 2 Any differences between the results of measurements made before and after the test may be used as a criterion for determining possible defects.
If the windings are provided with tappings, the reactance and, if required, the resistance also have to be measured for the tapping positions at which short-circuit tests will be carried out.
Please, select your language. This calculation shall be carried out in accordance with the requirements of 4. In this case, the factor k is found from oscillograms of the line currents.
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The peak value of the short-circuit current shall be calculated in accordance with 4. The manufacturer and the purchaser should agree which kind of short circuit is to be considered.
Annex A is for information only. U is the rated voltage U r of the winding under consideration, in kilovolts; Z t is the short-circuit impedance of the transformer referred to the winding under consideration; it is calculated as follows: It is iev that the tolerance on the agreed test current values and the duration of the tests are in line with those prescribed for two-winding transformers and that the test sequence is selected according to the expected increase of electrodynamic forces.
However, before dismantling, it is suggested that additional diagnostic means are applied see note 1 of 4. Enter the exact number of the standard: Q5 This standard meets my needs: NOTE 2 Generally, the short-circuit reactance variation should show a tendency to diminish in the course isc the tests.
In such cases, the overcurrent level must be limited by appropriate means, such 600076-5 series reactors or, in some instances, fuses.
INTERNATIONAL STANDARD IEC 60076-5
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 ied of zero-sequence to positive-sequence impedance of the system.
The object of the IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. In this context, a check of the axial compression of the windings could be useful. General catalogue Go to interactive catalogue.
This applies, for example, to unit generator transformers if the connection between generator and transformer is constructed in jec a iwc that the possibility of line-to-line or double-earth faults in this region is negligible.
Documents Flashcards Grammar checker. NOTE In connection with the economical impact of the cost of a transformer of category III and the cost implication of any thorough visual inspection extended to the inner parts of the unit, it is recommended that a series of photographs be taken of the position of the winding leads, taps, alignment of spacers and configuration of the end insulation components, etc.
Fort Hood Sentinel Advertisement. Information relating to this publication, including its validity, is available in the IEC Catalogue of publications see below in addition to new editions, amendments and corrigenda. Missing page numbers correspond to the Frenchlanguage pages. U and Z t are defined as follows: For categories I and II single-phase transformers, the number of tests shall be three.
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For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. External short circuits are not 60076-5 to three-phase short circuits; they include line-to-line, double-earth and line-to-earth faults. In order to avoid injurious overheating, an appropriate time interval shall occur between successive overcurrent applications.
NOTE 1 Additional means of detection may be used to obtain information and improve the evaluation iex 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.
The requirements apply to transformers as defined in the scope of IEC In this case, a more detailed examination may be required, including a dismantling of the unit as necessary to establish the cause of the deviation.
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