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):||8 February 2004|
|PDF File Size:||16.77 Mb|
|ePub File Size:||3.83 Mb|
|Price:||Free* [*Free Regsitration Required]|
In switching impulse testing, 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 600764- earth are less critical.
INTERNATIONAL STANDARD IEC
If the through capacitances C 1 and C 2 are large compared to the capacitance C 3 to earth then a 60076-44 distribution similar to curve M in the graph will result.
For three-phase reactors, the requirement, as in figure 4, that 1,5 times the voltage between phase and neutral shall be developed between phases, cannot be met.
This website is best viewed with browser version of up to Microsoft Internet Explorer 8 or Firefox 3. The appropriate limits may be established by transient analysis with a low-voltage recurrent surge generator.
If the above-mentioned methods of wavetail control are still not sufficient to attain the proper time to half-value, a compromise is necessary between either accepting a shorter time to halfvalue or resorting to resistance earthing at the non-tested terminal s of the winding s under test, according to figure A.
The wavetail record should permit the evaluation of the time to half-value and, on occasions, the amplitude of reversed polarity. For impedance earthed terminals, the main inductance becomes predominant.
Search results | IEC Webstore
Electronic Single-Phase kWh Meter. For the passive network of a transformer, both the admittance function and the impedance function are considered as a characteristic function in the frequency domain and should be independent of the waveshape. The sum of items ac and d or of items 60706-4c and dis sometimes referred to as line current.
Digitizers have been used in impulse testing since the s. The preferred method of test is that of direct application although in special cases where the intermediate or low-voltage winding cannot, in service, be subjected to lightning overvoltages from the system connected to it, the “transferred surge” method may alternatively be employed. Alternative means of switching impulse irc or simulation such iiec d. On transformers, all terminals and windings can be lightning impulse tested to specific and independent levels.
The final distribution will be similar to curve Q, where all, or almost all, of the voltage uec across the resistor.
Test methods for transformer neutrals are given in IEC It is, however, advisable to use sweep times for both voltage iwc current which cover the second half-cycle of the applied voltage.
The current flowing to earth through the tested winding can additionally be used. Impulse currents may be recorded and will in many cases give additional information about a fault.
The real time recordings of voltage and current at the full impulse and the transfer function show significant changes compared to the reduced full-wave impulse test.
600766-4, there are cases, for example, windings of extremely low ieec, where the series resistance will have a significant effect also on the wavetail. This can make the effective inductance to times greater than with direct earthing. Requirements for instruments IECDigital recorders for measurements in high-voltage impulse tests — Part 2: 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 of power transformers to supplement the requirements of IEC Insulation levels, dielectric tests and external clearances in air Part 4: The form of the change will be different depending on the method of failure detection employed.
Digital recording offers the potential for mathematical interpretation of the results and allows additional mathematical processing to be used, for example, for fault analysis in recordings. However, these are normally not applicable since the corresponding resistance values give unacceptably long front times. Historically, waveshape evaluation is based on oscilloscopic records, engineering rules and eye evaluation of waveshape parameters.
Unless the core magnetization state is identical before each switching impulse application at a given voltage level, identical waveshapes on successive applications will not be obtained.
On-line information is also available on recently issued publications, withdrawn and replaced publications, as well as corrigenda. It is, however, strongly emphasized that similar waveform discrepancies on another unit cannot necessarily be taken as arising from the same cause as the faults will present themselves differently from design to design. Information relating to this publication, including its validity, is available in the IEC Catalogue of publications see below in addition to new editions, amendments and corrigenda.
Therefore, the ic items of equipment are dealt with separately. Click to learn more. Similar but not necessarily identical instants of chopping are achieved by use of triggered-type chopping gaps see figure B.
06076-4 this limitation, guidance for selecting impulse generator capacitance and adjusting waveshapes is given in annex A.
However, the literature and experience regarding transfer function analysis was for many years contradictory. The value of the test voltage is determined according to the principles of IEC Examples of such transfer function are given in figure B.
Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work. Impedance earthing, 600764 than direct earthing, of the non-tested winding terminals results in a significant increase in the effective inductance.
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. Reference number IEC If the through capacitances C 1 and C 2 are extremely large compared to the capacitance C 3 to earth, a distribution similar to curve P in 60067-4 graph will result.
Hence, the voltage records on switching impulse tests are a sufficiently sensitive means for detection of most faults see figure B. 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.
It is good practice to firmly connect this current return path to the general earth system of the test room, preferably close to the test object. Requirements with respect to sampling frequencies and resolution of the digitizers’ input channels are the same as given in 7.
Annex B contains a number of oscillograms and digital recordings taken during actual tests on transformers and reactors demonstrating fault and non-fault conditions. It is also generally applicable to the testing of reactors see IECmodifications to power transformer procedures being indicated where required.