Do you need a multi-user copy? Our prices are in Swiss francs CHF. We accept all major credit cards American Express, Mastercard and Visa , PayPal and bank transfers as form of payment. IEC specifies the characteristics and tests for insulated bushings. This standard is applicable to bushings, as defined in Clause 3, intended for use in electrical apparatus, machinery, transformers, switchgear and installations for three-phase alternating current systems, having highest voltage for equipment above 1 V and power frequencies of 15 Hz up to and including 60 Hz.
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This fifth edition cancels and replaces the fourth edition, published in , and constitutes a technical revision. The committee has decided that the contents of this publication will remain unchanged until For bushings operating in air-insulated ducting, locally high ambient air temperatures have a significant effect on their current rating. This edition defines a limit to this temperature and specifies corresponding test conditions. This change is in line with other equipment standards.
Gas-insulated and gas-impregnated bushings have become a mature technology, for use in gas insulated switchgear. Limiting values for temperature rise and dielectric dissipation factor have therefore been introduced. 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 high level of integrity is needed to ensure that the bushing will not fail, or be the initiator of internal flashover in the transformer under test.
Dry power-frequency withstand test voltage levels for transformers bushings should be increased according to 9. Extension of the range of application of lightning impulse and switching impulse tests, included in IEC , is not considered technically or commercially justified for bushing routine or type tests.
The dynamic current withstand test is not mentioned in the text, because insufficient experience has so far been collected to design a realistic test. This standard is applicable to bushings, as defined in Clause 3, intended for use in electrical apparatus, machinery, transformers, switchgear and installations for three-phase alternating current systems, having highest voltage for equipment above 1 V and power frequencies of 15 Hz up to and including 60 Hz.
Special requirements and tests for transformer bushings in this standard apply also to reactor bushings. This standard is applicable to bushings made and sold separately. Bushings which are a part of an apparatus and which cannot be tested according to this standard, should be tested with the apparatus of which they form part. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document including any amendments applies.
The means of attachment flange or fixing device to the partition forms part of the bushing [IEV , modified] NOTE 1 The conductor may form an integral part of the bushing or be drawn into the central tube of the bushing. 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 2 A resin-bonded paper bushing can be provided with an insulating envelope, in which case the intervening space can be filled with an insulating liquid or another insulating medium.
An insulating envelope may consist of one insulator unit or two or more permanently assembled insulator 3. NOTE 2 If high-resistance coating is applied to parts of the insulating part of an insulator, such parts are considered to be effective insulating surfaces and the distance over them is included in the creepage distance.
NOTE 2 circuit. When the test tap is used for condition monitoring, in service, care should be taken to avoid an open 3. NOTE 2 This tap can also be used for the measurement of dissipation factor, capacitance and partial discharge.
The above series of currents are in accordance with the values indicated in IEC In the case of transformer bushings with the conductor drawn into the central tube, the supplier shall indicate the value of the cross-section, and the material of the conductor which correspond to I r in accordance with 4.
For bushings with I r equal to or greater than 4 A, I th shall always be kA. For transformer bushings, t th shall be 2 s, unless otherwise stated, with reference to IEC In such a case, the operating current and cross-section should conform with the requirements of 8. The transformer manufacturer should stipulate such requirements in the bushing ordering information see 6.
Level I is normal load and shall be generally applied, unless a purchaser specifies a heavy load of Level II. Any other angle of mounting shall be subject to agreement between purchaser and supplier. A bushing operating at any other angle is considered a tilted bushing see 6. If artificial pollution tests are required, they shall be performed in accordance with IEC NOTE 2 4. In the case of other insulating materials, the temperature limits shall be stated by the supplier.
For bushing terminals and connections, the temperature rises are also given in Table 2. Bushings used as an integral part of apparatus, such as switchgear or transformers, shall meet the thermal requirements for the relevant apparatus.
For transformer bushings, reference shall be made to 4. NOTE For gaskets in contact with metallic parts, special attention should be paid to the ability of the material to withstand the temperature rise.
The standard values of insulation level of a bushing having U m equal to or greater than kV shall be chosen from values given in Table 8. Other values of test tap capacitance to earth may be agreed between purchaser and supplier. The bushing shall not incorporate substantial capacitances to earth which may divert the partial discharge current and so give rise to incorrect or misleading partial discharge measurements on the transformer.
For systems in which overvoltages in excess of this may occur, it is advisable to choose a bushing with a higher U m. 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. It is not necessary to adjust the radial thickness of insulation or the clearance of the immersed end. The puncture strength and the flashover voltage in the immersion medium of a bushing are not affected by altitude.
Owing to the limitations of puncture strength and flashover voltage in the immersion medium, it may not always be possible to check the adequacy of the increased arcing distance by actual tests at any altitude lower than that of operation.
In such a case the supplier shall demonstrate, by the amount of increase of the arcing distance, that the bushing is adequate. Consideration should be given to the operating conditions of completely immersed bushings and bushings operating in air-insulated ducting. Moisture condensation on the surface of the indoor part of the bushing is to be prevented, if necessary by ventilation or heating.
Attention shall be drawn to any features including tests of the completed apparatus which may affect the design of the bushing see 7. For bushings of U m equal to or less than kV, markings indicated g are sufficient.
Markings for bushings according to Clause 10 are specified in For examples of marking plates, see Figures 1 and 2. NOTE Capacitance and dielectric dissipation factor measurements made on site may differ from factory values given on the nameplate.
It is recommended to make reference measurements at installation. Tests on insulating envelopes of ceramic material shall be carried out in accordance with IEC Tests on insulators of composite material shall be carried out in accordance with IEC All high-voltage tests, in accordance with 8.
The supplier shall provide a detailed type test certificate at the request of the purchaser. The tests shall have been carried out on bushings of a design that does not differ from that offered to the purchaser in any way that may improve the features to be checked by a type test. Repetition of a type test is only mandatory when specified in a particular contract. At the request of the purchaser, the supplier shall furnish any information concerning the minimum clearances to earthed parts in the operating arrangement.
The values of the applicable withstand test voltages for newly manufactured bushings are indicated in Tables 7, 8 and 9. The bushings shall not be damaged by the tolerated flashover in air when tested in accordance with 8. 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 For other bushings, tests to check dielectric, thermal and mechanical properties of bushings comprise the following tests.
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. Test taps and voltage taps shall be either earthed or held near earth potential. Liquid-filled and liquid-insulated bushings, according to 3.
Gas-filled, gas-insulated and gas-impregnated bushings, according to 3. Partly or completely immersed bushings, according to 3. Other media shall be agreed between purchaser and supplier. In particular, in the case of bushings intended for use on gasinsulated switchgear and transformers, tests may be required with simulation of adjacent metal parts on the GIS or transformer side.
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INTERNATIONAL STANDARD IEC 60137