IEC 60076-5 PDF
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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For transformers having more than two windings, auto-transformers, booster transformers and transformers directly associated with other apparatus, the overcurrents are calculated in accordance with 3. 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.
For example, edition numbers 1. If the short-circuit apparent power of the system is not specified, the values given in table 2 shall be used. NOTE 2 When insulation systems other than thermal class A are employed in oil-immersed transformers, different maximum values of temperature may be allowed by agreement between the manufacturer and the purchaser.
Delta-connected stabilizing windings of idc transformers shall be capable of withstanding the iiec resulting from different forms of system faults that can arise in service associated with relevant system earthing conditions. All International European Italian. Protection accessories, such as a gas-and-oil-actuated relay and pressure relief device, shall be mounted on the transformer during the test. General requirements and tests. NOTE Equations 4 and 5 are based on adiabatic conditions and are valid for only a short time duration, not exceeding 10 s.
NOTE In the case of winding in zigzag connection, the single-line-to-earth fault current may reach values higher than the three-phase short-circuit current. In order to avoid injurious overheating, an appropriate time interval shall occur between successive overcurrent applications. NOTE In connection with the economical impact of the cost of iwc 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.
For delta-connected windings, the single-phase supply is provided between two corners of the delta and the voltage during the test has to be the same as the voltage between phases during a three-phase test. This second edition cancels and replaces the first edition published in and amendment 2 The single-phase voltage during the test shall be equal to voltage between phases during the three-phase test.
Enter the exact 600765- of the standard: 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 lec that special precautions will be taken to avoid the risk of line-to-line short circuits.
Electrodynamic hazard to the winding assembly may be higher either at three- or single-phase short circuit depending on the winding design.
Particular requirements and tests for isolating transformers and power supply units incorporating isolating transformers.
For star-connected windings, the singlephase voltage is supplied between one line terminal and the other two line terminals connected together.
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 In case of single-phase units connected to form a three-phase bank, the value of rated power applies to three-phase bank rating. NOTE 2 For 60076-55 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 auto transformers and power supply units incorporating auto transformers.
INTERNATIONAL STANDARD IEC 60076-5
However, the lightning impulse test is not required at this stage. Safety of power transformers, power supply units and similar Part NOTE 2 Generally, the short-circuit reactance variation should show a tendency to diminish in the course of the tests.
International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. In this case, provision should be made by the purchaser to limit the overcurrent to the maximum value determined by the manufacturer and 60067-5 on the rating plate.
Particular requirements for separating transformers for general use. NOTE 1 For star-connected windings, the maximum asymmetry is obtained by switching on when the phase voltage passes through zero. The oscillograph can be set to record 6076-5 phase currents. Notice of any abnormal operation 60076–5 expected in the system s shall be given by the purchaser to the manufacturer in advance.
NOTE 3 Temporary sparks over tank joints may occur at the energizing stage and internal 600776-5 at the frame joints at the energizing and short-circuit stages. U and Z t are defined as follows: In order to consider the transformer as having passed the short-circuit tests, the following conditions shall be fulfilled: 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.
The requirements apply to transformers as defined in the scope of IEC In this ieec, the factor k is found from oscillograms of the line currents.
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. This aspect shall be taken into consideration when arranging the test circuit for transformers of category I.
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Missing page numbers correspond to the Frenchlanguage pages. This time shall be defined by agreement between the manufacturer and the purchaser. Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work.
Reference number IEC General requirements for basic safety and essential performance.
Annex A is for information only. During the tests, winding temperature may increase owing to the circulation of the shortcircuit current. Guidance for the identification of a similar transformer is given in annex A.