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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Therefore, the two items of equipment are dealt with separately. The tail length and the voltage across the resistance should be measured to determine the value of resistance to be used.
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The stored data in the memory of the digitizer, however, allows for any other presentation of the same recording by zooming in or uec at different time scales.
The basic waveform of the current corresponding to the cosine voltage wave is sinusoidal see figures 3b and B. Again it is possible to produce excessively high voltages to earth in parts of the winding.
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Q5 This standard meets my needs: Examples of such transfer function are given in figure B. Temperature rise Part 3: In order to benefit from additional ifc investigation tools, such as transfer function analysis see clause iedfor the examination of the test results, it is important that the same recording time for the recording of the impulse current and voltage is used.
Some possibilities have been identified in 9. For transformers, any part-winding 600764- turn-to-turn failure, disc-to-disc breakdown, or breakdowns in tapping windings will result in a flux blockage and will easily be detected by voltage and current records. L t is influenced by the connection of the non-tested windings. Refer also to IEC The IEC collaborates closely with the International Organization for Standardization ISO in accordance with conditions determined by agreement between the two organizations.
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However, in this case the effective transformer capacitance C t for the longer front time is equal to the effective winding earth capacitance C e. When testing reactors, both of the shunt and series types, items c and e are inapplicable; item d may be applied but only as an additional means of transient recording since it is likely to be less sensitive than when used in transformer testing.
In this case, the inductive loading of the generator is significantly increased and it may be difficult to achieve times to half-value set by irc tolerances. The real time recordings of voltage and current at the full impulse and the transfer function 6007-64 significant changes compared to the reduced full-wave impulse test.
In this case, T d and T z can only be determined from full test-level shots. Note changes in the superimposed high-frequency oscillations on the capacitively transferred current and changes in the voltage wave after chop.
BS 171-4:1978, IEC 60076-4:1976
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. On-line information is also available on recently issued publications, withdrawn and replaced publications, as well as corrigenda.
It varies between the leakage inductance L s for short-circuited terminals and L o for open-circuited terminals. Hence, in this standard, lightning impulse testing is covered by a common text for both transformers and reactors whilst switching impulse testing is dealt with separately for the two types of equipment.
Information is given on waveshapes, test circuits including test connections, earthing practices, failure detection methods, test procedures, measuring techniques and interpretation of results. For the wavetail, C t can be estimated as C B plus part of C edependent on the initial voltage distribution.
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INTERNATIONAL STANDARD IEC
For example, edition numbers 1. This waveshape should be characterized mainly by its frequency, determined by the reactor inductance and the generator capacitance, and the damping coefficient.
It should, however, be sufficiently long to ensure essentially uniform distribution of voltage. However, in order to improve the wavetail T 2resistance earthing of the non-tested windings may be advantageous see clause 5 and 7.
In general, both front and tail parameters are adjusted according to these principles applicable for purely capacitive loads. Responses from test object failures — A failure digital recording of a tap changer lead flashover between taps is shown in figure B.
In switching impulse jec, since the rates of change of the impulse voltages and currents are much reduced compared with those in a lightning impulse test and no chopping circuit is involved, the problems of potential gradients around the test circuit and with respect to the reference earth are less critical.
This configuration does not produce a sustained stress eic winding to earth, but it does stress the insulation within the winding. You may experience issues viewing this iex in Internet Explorer 9, ic or 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.
After any check has been made, it is essential that neither the measuring nor the test circuit is altered except for the removal of any devices for checking. However, practice has ie to specify reactor waveshapes as for transformers, that is, by T 1T d and T z see figures 3b and B.
The flux in these reactors cannot be directed through the windings on the non-tested limbs.