IEC Power transformers – Part 4: Guide to the lightning impulse and switching impulse testing – Power transformers and reactors. Edition Guide to the lightning impulse and switching impulse testing –. Power transformers and reactors. Reference number. IEC (E). INTERNATIONAL. Buy IEC Ed. Power transformers Part 4: Guide to the lightning impulse and switching impulse testing – Power transformers and reactors from SAI.
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Datasheet – Mouser Electronics. In switching impulse testing, however, because of the magnetically transferred voltage, a specified test level may only be obtained on one winding see IEC To meet the different requirements of the waveshape for lightning and switching iwc, due consideration has to be given to the selection of ifc impulse generator parameters, such as capacitance and series and discharge parallel resistances.
This is a skilled task and it is often difficult to decide the significance of discrepancies, even with considerable experience, because of the large number of possible disturbance sources. The requirement that 1,5 times the voltage between phase and neutral iecc be developed between phases cannot be met on shell-type and five-limb core-type transformers without delta-connected windings, as the flux cannot be directed through the windings on the nontested limbs.
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When specified, these recordings should be properly identified and arranged so that the necessary comparisons between full waves and chopped waves can be easily made. On-line information is also available isc recently issued publications, withdrawn and replaced publications, as well as corrigenda.
In these cases, the value of T 2 cannot directly be adjusted according to equation A. The value of the test voltage is determined according to the principles of IEC To show ied reversibility of any non-linear effects, the same reduced full-wave impulses should follow up the full-wave test voltage in a reversed way.
Similar considerations with respect to superimposed oscillations are valid also for singlephase auto-transformers. This configuration tends to change turn-to-turn and coil-to-coil stresses, the amount of change depending on the winding time constants. The intention of illustrating particular faults is to give general guidance only. This procedure includes reference to measures which may be taken to increase the impulse duration by delaying the possible onset of core saturation.
However, severe reduction of R s will result in excessive overshoot or superimposed oscillations at the crest of the impulse wave and also, as described earlier, in an excessive opposite polarity peak.
Here a higher resolution of the capacitive current flowing to earth, or a second current record 6076-4 tank currentmay be helpful. When resistive voltage dividers are used to check the voltage of the non-tested terminals, they should remain in the circuit because they represent a significant loading of the circuit. They comprise — the determination of the impulse voltage waveshape; — the application of one negative polarity reduced test level impulse; 600776-4 the application of three negative polarity impulses at the switching impulse 60076-44 level without any pre-magnetization measures.
Hence, the requirement in IEC that a phase-to-phase voltage of 1,5 U will occur when a voltage U is applied to one terminal, is valid only in principle. A parallel measurement of the peak voltage by a peak voltmeter according to IEC is highly recommended.
The appropriate limits may be established by transient analysis with a low-voltage recurrent surge generator.
Currents may increase or decrease and the direction of the change together with the method of fault detection will give guidance on the nature and location of the fault see figure B.
Q2 Please tell us in what capacity ies you bought the standard tick all that apply. Ability to withstand short-circuit Part 8: For large values of T 1the damping coefficient will be large thus resulting in a relatively short time T z. In the following a few example recordings, both for real time and transfer function analysis, are presented.
BS 171-4:1978, IEC 60076-4:1976
Accept and continue Learn more about the cookies we use and how to change your settings. Guide to the lightning impulse and switching impulse testing — Power transformers and reactors 1 Scope This part of IEC gives guidance and explanatory comments on the existing procedures for lightning and switching impulse testing ic power transformers to supplement 60076-44 requirements of IEC Major changes in current records such as amplitude and frequency changes normally indicate part winding breakdowns within the tested winding, between windings or to earth see figure B.
When oscillograms or digital recordings of the impulse response current are taken, it is preferable to employ the same sweep time or sampling time as used for the voltage record.
One pertinent recording see clause 11 is normally sufficient for acceptance tests. Therefore, during a test, the interphase voltages are likely to be higher than 1,5 U if no measures are taken at the non-tested terminals to suppress the oscillatory voltages by means of high ohmic impedance earthing. It should be long enough to ensure approximately uniform distribution throughout the tested winding.
When recording neutral or winding current, recording should continue at least until the inductive peak has been reached, thus permitting examination of the wave to determine if there has been any change in inductance caused by short-circuiting of turns as a 60076–4 of insulation failure.
In addition to the methods of waveshape adjustment in 7.
BS , IEC – Power transformers. Specification for tappings and connections
For wavetail adjustments, the test object can be represented by its effective inductance as indicated in figure A. Secondly, it should be checked that core earthing or any non-linear elements within the test object are not the source of the disturbances. To make sure that we continue to meet your needs, your ice is essential. Insulation levels, dielectric tests and external clearances in air IECReactors IECInstruments and software used for measurement in high-voltage impulse tests — Part 1: The number of the required pre-magnetizing impulses and their level depend on the level of test voltage aimed for.
This new technology represents a very powerful tool for the future, because it may also be used for on-line condition monitoring, both for dielectric defects and for mechanical defects after severe short-circuits.