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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Capacitively transferred current will, for faults in the tested winding or to earth, show an instantaneous change in polarity.
A significant increase, combined with a change in superimposed frequency in a neutral current is indicative of a fault within the tested winding whilst a decrease indicates a fault from the tested winding to an adjacent winding or to earth.
It is equally important to use 6076-4 raw data for non-standard waveshape evaluation. However, this sensitivity is accompanied by ieec possibility of the recordings indicating a number of effects not directly associated with failure.
The time to half-value T 2 is, for lightning impulses, primarily determined by the generator capacitance, the inductance of the test object and the generator discharge resistance or 600764- other parallel resistance. It is more important to try to obtain the required voltage level by means of termination resistors of sufficiently high value.
Temperature rise Part 3: The magnitude of the voltage is determined by the initial charging voltage, the number of capacitors in series at discharge, and the regulation of the circuit.
While the applied voltage is uniquely defined, the choice of the other characteristic to be recorded is dependent on the selection of the method of failure detection. Before a test, an overall check of the test circuit and the measuring system may be performed at a voltage lower than the reduced voltage level.
These are listed a to e below. Different transients can be recorded and used separately or in combination, as shown in figure 2. Hence, the normal impulse test procedures as used for lightning impulse tests are required. Item 3 in figure A. This test configuration is very suitable for current measurements since there is no increase in the circuit resistance and the circuit therefore has good response to high-frequency disturbances.
Special attention should be given to the amount of overswing to opposite polarity of lightning impulses. By their very nature, non-linear protection devices connected across the windings may cause uec between the reduced full-wave and the full-wave impulse oscillograms or digital recordings.
The waveshape is determined largely by the capacitances and resistances of the generator and the impedance of the load. The voltage measuring circuit, which is a separate loop of the test object carrying only the measuring current and not any major portion 600766-4 the impulse current flowing through the windings under test, should also be effectively connected to the same reference earth. Protection of the sensitive electronic devices in the digital recording system, the entire processing equipment and its power supply against these fields iwc required.
To make sure that 660076-4 continue to meet your needs, your feedback is essential. Transferred voltage recordings 600076-4 also indicate the above-mentioned faults. For transformers, any part-winding defect 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.
INTERNATIONAL STANDARD IEC
You may experience issues viewing this site in Internet Explorer 9, 10 or For wave analysis, it is important to take samples over the complete waveshape until the wave is completely damped, using the maximum available memory of the digitizer. Information on the subjects under consideration and work in progress undertaken by the technical committee which has prepared this publication, as well as the list of publications issued, is also available from the following: Datasheet – Mouser Electronics.
The stored data in the memory of the digitizer, however, allows for any other presentation of the same recording by zooming in or out at different time scales.
The appropriate limits may be established by transient analysis with a low-voltage recurrent surge generator.
You may find similar items within these categories by selecting from the choices below:. Historically, waveshape evaluation is based on oscilloscopic records, engineering rules and eye evaluation of waveshape parameters.
Annex B contains a number of oscillograms and digital recordings taken during actual tests on transformers and reactors demonstrating fault and non-fault conditions. This series and sometimes isc discrepancies after the peak, which may also originate from the with multiple parallel stage operation, if the discharge circuits are not coincident in may require new setting of the discharge gaps on generators which have both parallel gaps.
Generally speaking, traces recorded from the same channel, under the same test conditions and using the same test circuit constants, should be identical except in the case of non-linear devices. In such cases, higher resolution recording to cover the time to peak and to the opposite polarity of the applied cosine wave is recommended.
Special attention should be given to the effect of magnetic saturation of the core and the possibility of clipping of voltage and current recordings because of saturation of the input amplifiers of the digitizer. This configuration tends to change turn-to-turn and coil-to-coil stresses, the amount of change depending on the winding time uec.
Therefore, uec selection of 60076-44 proper reference earth is important. Search all products by. Impedance earthing, rather than direct earthing, of the non-tested winding terminals results in a significant increase in the effective inductance. Provided that the time resolution is sufficiently high, a more 6006-4 analysis of discrepancies is possible.
A brief explanation of the principles of waveshape control is given in annex A. Please download Chrome or Firefox or view our browser tips. Likewise, incipient faults at or near the terminal under test may also give only small indications on the oscillograms or digital recordings.