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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The above series of currents are in accordance with the values indicated in IEC For bushings of highest voltages for equipment equal to or less than 52 kV, made of ceramic, glass or inorganic materials, resin or composite insulation, see Clause This edition defines a limit to this temperature and specifies corresponding test conditions. Liquid-containing bushings shall remain empty and shall have an opening for free gas circulation within the envelope.
For gas-insulated bushings according to 3. The load shall be in the direction which will cause the highest stress at the critical parts of the bushing in normal operation.
In such a case, the operating current and cross-section should conform with the requirements of 8. For further information reference should be made to IECTable 6.
Insulation levels, dielectric tests and external clearances in air IEC NOTE 2 This tap can also be used for the measurement of dissipation factor, capacitance and partial discharge. Reference number IEC For bushings with more idc one air side terminal, it is generally sufficient to apply the load to one terminal only.
INTERNATIONAL STANDARD IEC 60137
Tests on insulators of composite material shall be carried out in accordance with IEC For bushings of U m equal to or less than kV, markings indicated g are sufficient. The time intervals between consecutive applications of the voltage shall be sufficient to avoid effects from the previous applications of voltage.
For transformer bushings, reference shall be made to 4. Normally, GIS and transformer bushings are tested in the vertical position, with the flange earthed or held near to earth potential.
INTERNATIONAL STANDARD IEC
Tests — Test Q: It is not necessary to adjust the radial thickness of insulation or the clearance of the immersed end. The test shall not be started until thermal equilibrium between the oil and the bushing has been reached.
The object of IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. NOTE 2 By agreement between purchaser and supplier, other temperature ranges may be adopted.
Generation, transmission and distribution of electricity — Operation IEC Voltage records shall be made for each impulse.
The committee has decided that the contents of this publication will remain unchanged until For systems in which overvoltages in excess of this may occur, it is advisable to choose a bushing with a higher U m. For capacitance graded bushings it is assumed that a puncture has occurred if the capacitance measured after the test rises above the capacitance previously measured by about the amount attributable to the capacitance of one layer.
Bushings with a conductor drawn into the central tube shall be assembled with an appropriate conductor, the cross-section of which shall conform with I r. Extension of the range of application of lightning impulse and switching impulse tests, included in IECis not considered technically or commercially justified for bushing routine or type tests.
NOTE 4 For bushings where upper and lower insulating envelopes are assembled by clamping force on the central fixing conductor, it is recommended to choose the cantilever test load, taking into account the thermal expansion of the conductor due to the rated current flow. If a flashover occurs the test shall be repeated once only.
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For bushings operating in air-insulated ducting, locally high ambient air temperatures have a significant effect on their current rating. The resistance of the wire and the current shall be adjusted in a such a way as to produce the same losses as the final conductor.
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.
For transformer bushings operating in air-insulated ducting, the air side shall be enclosed in an appropriate chamber.