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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A bushing operating at any other angle is considered a tilted bushing see 6. Normally, GIS and transformer bushings are tested in the vertical position, with the flange earthed or held near to earth potential. It is eic, after changing polarity, to apply some impulses of minor amplitude before the application of the test impulses.
For wall bushings the test load shall be applied to each end of the bushing separately. An example of a marking plate is given in Figure 3. As the dielectric routine tests see 7. The test may be omitted for transformer bushings fitted with a one-piece metal flange, provided the flange has been subjected to a preliminary tightness test, and the bushing has passed the type test in accordance with 8.
NOTE 2 Attention is drawn to special requirements for transformer bushings concerning dry power-frequency withstand voltage see 9.
To simulate service conditions, the bushing shall be mounted on an earthed plane, radially extended from the axis of the bushing at least 0,4 L in every direction, L being the dry arcing distance of the bushing. Moisture condensation iiec the surface of the indoor part of the bushing is to be prevented, if necessary by ventilation or heating. For test conditions, 8. In the case of bushings for gas-insulated switchgear, special test requirements for chopped lightning test may be agreed upon between purchaser and supplier to cover the behaviour of the bushing concerning very fast transient voltage.
The object of IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. The test shall not be started until thermal equilibrium between the oil and the eic has been reached.
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Subject to agreement between manufacturer and purchaser, the standard oil temperature rise of 60 K may be reduced to reflect the real transformer 601137 oil temperature. The external part of the bushing shall be enclosed in an envelope, where necessary.
For bushings operating in air-insulated ducting, locally high ambient air temperatures have a significant effect on their current rating. For these bushings, precautions shall be taken to ensure that the end, which is designed to receive the movable part, will 601137 the relevant test voltage, where applicable.
For further information reference should be made to IECTable 6. Level I is normal load and shall be generally applied, unless a purchaser specifies a heavy load of Level II.
INTERNATIONAL STANDARD IEC 60137
The value for emergency duty is in accordance with 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 In circular conductors of diameter D cmthe equivalent cross-section shall take skin effect into account. When the test tap is used for condition monitoring, in service, care should be taken to avoid an open 3.
Liquid-containing bushings shall remain empty and shall have an opening for free gas circulation within the envelope. While all reasonable efforts are made to ensure that the technical content of IEC Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any misinterpretation by any end user. For transformer bushings operating in air-insulated ducting, the air side shall be enclosed in an appropriate chamber.
For gas-immersed bushings, the tank shall be filled with gas at maximum operating pressure at ambient temperature. The load shall be applied perpendicular to the axis of the bushing at the mid-point of the terminal for 60 s. For bushings with internal bellows, the pressure shall be stated by the supplier. It is not necessary to adjust the radial thickness of insulation or the clearance of the immersed end.
The test duration is 60 s, independent of frequency. This edition defines a limit to this temperature and specifies corresponding test conditions. The time intervals between consecutive applications of the voltage shall be sufficient to avoid effects from the previous application of voltage. If the actual atmospheric conditions deviate from the values given in IECcorrection shall be made as given in Table 4.
The magnitude of the test voltage is given to Table 8. At the request of the purchaser, the supplier shall furnish any information concerning the minimum clearances to earthed parts in the operating arrangement.