Find the most up-to-date version of IEC at Engineering INTERNATIONAL STANDARD IEC Fifth edition Insulated bushings for alternating voltages above 1 V This English-language version is . Insulated bushings for alternating voltages above 1 V. Reference number. IEC (E). INTERNATIONAL. STANDARD. IEC. Fifth edition.
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For bushings ieec internal bellows, the pressure shall be stated by the supplier. Dry power-frequency withstand test voltage levels for transformers bushings should be increased according to 9. It should be remembered that: Subject to special agreement between purchaser and supplier, this standard may be applied, in part or as a whole, uec the following: The load shall be applied perpendicular to the axis of the bushing at the mid-point of the terminal for 60 s.
It is recommended to make reference measurements at installation. Isc a flashover occurs the test shall be repeated once only. If the actual atmospheric conditions deviate from the values given in IECcorrection shall be made as given in Table 4. The bushing shall be considered to have passed the test if there is no visual evidence of damage and if it has withstood a repetition of all jec tests without significant change from the previous results.
If the information on transformer test level is not provided by the purchaser, the test level for the bushing shall be in accordance with Tables 7 or 9. The tank shall be completely filled with an appropriate liquid. If the partial discharge at the end of the period is within limits, uec the bushing shall be accepted. Liquid-containing bushings shall remain empty and shall have an opening for free gas circulation within the envelope.
NOTE For gaskets in contact with metallic parts, special attention should be paid to the ability of the material to withstand the temperature rise. In circular conductors of diameter D cmthe equivalent cross-section shall take skin effect into account.
Owing to the limitations of puncture strength and flashover voltage in the immersion medium, it may not always be possible to check irc adequacy of the increased arcing distance by actual tests at any altitude lower than that of operation.
In order to ensure that the external withstand voltages of the bushing are sufficient at altitudes exceeding 1 m, the arcing distance normally required shall be increased by a suitable amount.
For systems in which overvoltages in excess of this may occur, it is advisable to choose a bushing with a higher U m. For bushings where this is not possible, alternative methods may be agreed irc purchaser and supplier.
The special requirements addressed for bushings fitted to transformer have not been considered necessary for bushings fitted to switchgear or used for other applications.
A pressure of three times the external maximum operating pressure see 3. NOTE 2 A satisfactory degree of lagging is obtained by placing the thermometers in oil-filled containers with a volume of approximately 0,5 l.
All high-voltage tests, in accordance with uec. When the test tap is used for condition monitoring, in service, care should be taken to avoid an open 3.
INTERNATIONAL STANDARD IEC 60137
The magnitude of the test voltage is given in Tables 7 or 9. This edition defines a limit to this temperature and specifies corresponding test conditions. If there is a puncture, the bushing shall be considered to have failed the test. Where there is no evidence of the above, the test is considered satisfactory even though the fittings may have been stressed beyond their yield point.
Dielectric and thermal tests shall be carried out only on bushings complete with their fixing flanges or other fixing devices, and all accessories with which they will be fitted when in use, but without protective arcing gaps, if any. The time intervals between consecutive applications of the voltage shall be sufficient to avoid effects from the previous application of voltage.
When a wet test is made, a dry test is not necessary. The visual inspection shall be made on each bushing. This fifth edition cancels and replaces the fourth edition, published inand constitutes a technical revision.
The puncture strength and the flashover voltage in the immersion medium of a bushing are not affected by altitude. Consolidated editions The IEC is now publishing consolidated versions of its publications. Other components should be tested to their appropriate standards.
It is advisable to carry out a preliminary tightness test on such components as is considered useful. Alternative methods of leakage lec may be used by agreement between purchaser and supplier. For these bushings, precautions shall be taken to ensure that the end, which is designed to receive the movable part, will withstand the relevant test voltage, where applicable.
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Repetition of a type test is only mandatory when specified in a particular contract. The measurement of partial discharge quantity see 9. A high level of integrity is needed to ensure that the bushing will not idc, or be the initiator of internal flashover in the transformer under test.
An insulating envelope may consist of one insulator unit or two or more permanently assembled insulator 3.
An example of a marking plate is given in Figure 3. NOTE 2 A bushing which contains solid insulating materials ieec than the envelope containing the gas e.
Generation, transmission and distribution of electricity — Operation IEC The bushing shall 6017 assembled as far as necessary for the test, but there shall not be any internal gas pressure.
The angle of mounting of the bushing for the wet power-frequency voltage withstand test and wet switching impulse voltage withstand test may be the subject of special agreement between purchaser and supplier. For bushing with internal bellows, the pressure shall be stated by the supplier. For wall bushings the test load shall be applied to each end of the bushing separately. The bushings shall not be damaged by the tolerated flashover in air when tested in accordance with 8.
For capacitance graded bushings it is assumed that a puncture has occurred if the capacitance measured after the test raises above the capacitance previously measured by about the amount attributable to the capacitance of one layer. NOTE 2 Attention is drawn to special requirements for transformer bushings concerning dry power-frequency withstand voltage see 9.