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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An insulating envelope may consist of one insulator unit or two or more permanently assembled insulator 3.
The actual temperature during the measurement shall be stated in the test report. If a vertical bushing is to be tested horizontally, then the test load can be reduced in the same manner.
INTERNATIONAL STANDARD IEC 60137
Tests — Test Q: To avoid destruction of the insulation in the case of bushings with the conductor embedded in the insulating material, the temperature of the hottest spot may, by agreement between purchaser and supplier, be determined as follows: For transformer bushings operating in air-insulated ducting, the air side shall be enclosed in an appropriate chamber. The test shall be a type test only in the case of bushings with gaskets of which the final placing is not carried out by the supplier, for example the top cap gasket of draw-through conductor transformer bushings.
ifc Definitions, principles and rules IEC In such a case, the operating current and cross-section should conform with the requirements of 8.
The ambient air temperature shall be measured with lagged thermometers placed around the bushing at mid-height and at a distance of 1 m to 2 m from it. The dry switching impulse withstand test for transformer bushings of U m less than kV switching impulse may be applied subject to agreement. 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.
The load shall be applied perpendicular to the axis of the bushing at the mid-point of the terminal for 60 s. It is permissible, after changing polarity, isc apply some impulses of minor amplitude before the application of the test impulses. The above series of currents are in accordance with the values indicated in IEC Please assess the standard in the following categories, using the numbers: The bushing shall be assembled as far as necessary for the test, but there shall not be any internal gas pressure.
The insulator shall be completely filled with an appropriate medium. An example of a marking plate is given in Figure 3.
The test duration shall be 60 s, independent of frequency. If a tilted or horizontal bushing is to be tested vertically, then an equivalent force should be added to achieve the bending moment at the flange, caused by the weight of the bushing in its operating position.
For wall bushings the test load shall be applied to each end of the bushing separately. The concentration of gas in the air inside the envelope shall be measured twice at an interval equal to or greater than 2 h.
The bushing shall be enclosed in an envelope, for example a plastic bag. For bushings of U m equal to or less than kV, markings indicated g are sufficient. A pressure of three times the external maximum operating pressure see 3.
INTERNATIONAL STANDARD IEC
An appropriate number of thermocouples or other measuring devices shall, as far as possible, be placed along the bushing conductor, central tube and other current-carrying parts, as well as possibly on the flange or other fixing device, so as to determine the hottest spot of the bushing metal parts in contact with insulating material with reasonable accuracy.
Moisture condensation on the surface of the indoor part of the bushing is to be prevented, if necessary by ventilation or heating. 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. The gas shall be maintained at a temperature agreed upon between purchaser and supplier. Gas-filled, gas-insulated and gas-impregnated bushings, according to 3.
The visual inspection shall be made on each bushing. Test taps and voltage taps shall be either earthed or held near earth potential.
The committee has decided that the contents of this publication will remain unchanged until The point of maximum conductor temperature lies at distance L M from the cooler end. One method is to wrap a resistive insulated wire around a conductor dummy and to feed it by a suitable supply. If a flashover occurs, the test shall be repeated once only. NOTE 2 This tap can also be used for the measurement of dissipation factor, capacitance and partial discharge. The object of IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields.
NOTE 2 The bushing may be of the types as prescribed in 3. NOTE 2 A bushing which contains solid insulating materials other than the envelope containing the gas e. NOTE 1 The daily mean temperature of the immersion medium should be calculated by averaging 24 consecutive hourly readings.
At the request of the purchaser, the supplier shall furnish any information concerning the minimum clearances to earthed parts in the operating arrangement.
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.