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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INTERNATIONAL STANDARD IEC 60076-5
NOTE At the zigzag connected windings, the short-circuit current for a single-line-to-earth fault may reach considerably higher values than at the three-phase fault. In order to consider the transformer as having passed the short-circuit test, iev following conditions shall be fulfilled: In this case, provision should be made by the purchaser to limit the overcurrent to the maximum value determined by the manufacturer and stated on the rating plate.
Any divergence between the IEC Standard and the corresponding national or regional standard shall be clearly indicated in the latter. 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 iex a ied Hz power supply provided that the prescribed test current values, as required in 4.
Another method for determining the phase current in a delta-connected winding is by suitably interconnecting the secondary windings of the current transformers measuring the line currents. The oscillograph can be set to record the phase currents. 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.
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. Annex B forms an integral part of this standard.
Table of physical and chemical constants — Kay and Laby — 15 edition, Longmans, 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.
In these cases, the testing conditions shall be agreed between the purchaser and the manufacturer.
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The testing arrangements, the current values, the sequence and the ifc of tests are always subject to agreement between the manufacturer and the purchaser. General requirements and tests IEC Safety of power transformers, power suply units and similar Part 2: Please contact the Customer Service Centre see below for further information. Safety of power transformers, power suply units and similar Part 2: However, parties to agreements based on this part of IEC are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below.
NOTE 2 In case of single-phase units connected to form a three-phase bank, the value of rated power applies to three-phase bank rating.
In such cases, the overcurrent level must be limited by appropriate means, such as series reactors or, in some instances, fuses. The choice of the test duties to be performed should be made, as a rule, on the basis of the analysis of 60067-5 results of calculations of electrodynamic forces occurring in all possible fault cases. Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work.
INTERNATIONAL STANDARD 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. NOTE Equations 4 and 5 are based on adiabatic conditions and are valid for only a short time duration, not exceeding 10 s.
However, these high values are limited, in the two limbs concerned, to a half of the coil and furthermore the currents in the other star-connected winding are lower than for a three-phase short circuit. Particular requirements for isolating transformers for the supply of medical locations IEC Safety of power transformers, power supplies, reactors and similar products Part However, for transformers of category I, the repetition of the routine tests with the exception of the dielectric tests may be omitted.
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 IEC shall not be held responsible for identifying any or all such patent rights. For example, edition numbers 1.
Care must be taken to guard against faults in the zone between the transformer and the protective apparatus. Safety of power transformers, power supply units and similar Part International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. General requirements and tests. 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: The IEC collaborates closely with the International Organization for Standardization ISO in accordance with conditions determined by agreement between the two organizations.
Particular requirements for separating transformers for general use.