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.
|Published (Last):||6 March 2004|
|PDF File Size:||8.94 Mb|
|ePub File Size:||14.47 Mb|
|Price:||Free* [*Free Regsitration Required]|
Guide to the lightning impulse and switching impulse testing — Power transformers and reactors This English-language version is derived from the original bilingual publication by leaving out all French-language pages. Iiec inductance of such windings may irc so low that the resulting waveshape is oscillatory. 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.
When the indirect method is used, i. They comprise — the determination of the impulse voltage waveshape; — the application of one negative polarity reduced test level impulse; — the application of three negative polarity impulses at the switching impulse withstand level without any pre-magnetization measures. 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.
Enter the exact number of the standard: This results from the slightly different times at which the maxima of applied U and induced 0,5 U voltages occur.
This series and sometimes also 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. 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.
The other terminal of this phase winding should be earthed. The principles of how to control waveshapes in lightning impulse testing of transformers are indicated by means of the simplified diagrams given in figures A.
For impedance earthed terminals, the main 600764- becomes predominant. IEC specifies a 9-bit, 60 MHz digitizer as the minimum resolution of the digitizer for the registration of impulse voltage and current waveshapes.
This procedure includes reference to measures which may be taken to increase the impulse duration by delaying the possible onset of core saturation. Guide to lightning impulse and switching impulse testing — Power transformers and reactors Part 5: When digital recorders are used as straight-forward measuring instruments for recording of voltage and current waveshapes, without the purpose of mathematical processing see clause 10 of the recorded data, they are to be regarded as technically advanced analogue instruments.
You may find similar items within these categories by selecting from the ifc below:. The requirements for eic digitizer as mentioned in 7. Electronic Single-Phase kWh Meter. With the non-tested windings short-circuited and earthed usual connectionL t is the leakage inductance of the transformer. Annex B contains a number of oscillograms and digital recordings taken during actual tests on transformers and reactors demonstrating fault and non-fault conditions.
The flux in these reactors cannot be directed through the windings on the non-tested limbs.
Significant changes occur in all real time and transfer function records. The difference in the T 2 parameter is not explainable. Your basket is empty. Fort Hood Sentinel Advertisement.
INTERNATIONAL STANDARD IEC
Search all products by. The voltage measuring circuit, which is a separate loop of the test object carrying only the measuring current and not any major portion of the impulse current flowing through the windings 60706-4 test, should also be effectively connected to the same reference earth. The value of the test voltage is determined according to the principles of IEC A significant increase, combined with a change in superimposed frequency in a neutral 6076-4 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.
The preferred method of test is that of direct application although in special cases where the intermediate or low-voltage 600764 cannot, in service, be subjected to lightning overvoltages from the system connected to it, the “transferred surge” method may alternatively be employed.
For diagnostic purposes, however, the software of the system offers the possibility to examine the wave over the entire sampling time, or part of the wave as all information is stored in the computer memory.
The basic waveform of the eic corresponding to the cosine voltage wave is sinusoidal see figures 3b and B. This, in fact, represents a guideline for the arrangement of the chopping circuit and may entail the introduction of additional impedance Z c in this circuit to meet the limit see figure 1. It should be remembered that in multi-stage generators, differences in the firing times of the individual stages may give rise to minute changes in the amplitude of current records with high-frequency initial oscillations without changing the basic frequency.
INTERNATIONAL STANDARD IEC 60076-4
For large values of T 1the damping coefficient will be large thus resulting in a relatively short time T z. This International Standard cancels and replaces IEC published in and constitutes a technical revision of that document.
Therefore, the selection of a proper reference earth is important. For undated references, the latest edition of the referenced document including any amendments applies. In this case, T d and T z can only be determined from full test-level shots. They need to be subdivided into two major aspects: The intention of illustrating particular faults is to give general guidance only.
Information on types of voltage dividers, their applications, accuracy, calibration and checking is given in IEC This configuration relies on a transfer of energy to the inductor from the impulse generator during the front portion of the wave and a transfer of energy from the inductor to the winding during the tail portion of the wave. It should, however, be pointed out that the effective transformer capacitance C tincluded in the values of C, is a different physical quantity for front and tail considerations.
A fault from the tested winding to an adjacent winding will show an instantaneous increase in amplitude in the same polarity sense and a change in basic frequency.
It is essential, in acceptance testing, to record at least one of these transients in 60067-4 to the applied test voltage: It is determined by the effective winding capacitance, any load capacitance and iwc series resistances.
The sensitivity of this measurement is higher than that of the applied voltage. For windings of small series capacitance, that is, exhibiting essentially travelling wave 60067-4, it may be possible to identify the source of disturbances by evaluating the time difference between the arrival at the neutral of the capacitive and the travelling wave disturbances.
It should, however, be sufficiently long to ensure essentially uniform distribution of voltage.
GSO IEC – Standards Store – GCC Standardization Organization
Provided that the time resolution is sufficiently high, a more iiec analysis of discrepancies is possible. 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.
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.