IEC 62067:2011 pdf free download – Power cables with extruded insulation and their accessories for rated voltagesabove 150 kV(Um= 170 kV) up to 500 kV(Um =550 kV)-Test methods andrequirements
10.2Frequency of tests
The sample tests in items a) to h) and k) in 10.1 shall be carried out on one length from eachbatch of the same type and cross-section of cable,but shall be limited to not more than 10 %of the number of lengths in any contract, rounded to the nearest whole number.
The frequency of the tests in items i) and j) in 10.1 shall be in accordance with agreed qualitycontrol procedures. In the absence of such an agreement, one test shall be made for contractswith a cable length between 4 km and 20 km and two tests for contracts with longer cablelengths.
10.3 Repetition of tests
lf the sample from any length selected for the tests fails in any of the tests in Clause 10, furthersamples shall be taken from two further lengths of the same batch and subjected to the sametests as those in which the original sample failed. lf both additional samples pass the tests, theother cables in the batch from which they were taken shall be regarded as having compliedwith the requirements of this standard. If either fails, this batch of cables shall be regarded ashaving failed to comply.
10.4 Conductor examination
Compliance with the requirements of lEC 60228 for conductor construction shall be checked byinspection and measurement when practicable.
10.5 Measurement of electrical resistance of conductor and of metal screen/sheath
The cable length，or a sample thereof，shall be placed in the test room，which shall bemaintained at a reasonably constant temperature for at least 12 h before the test. If there is adoubt that the conductor or metal screen temperature is not the same as the room temperature,the resistance shall be measured after the cable has been in the test room for 24 h.Alternatively，the resistance may be measured on a sample of conductor or metal screen,conditioned for at least 1 h in a temperature-controlled liquid bath.
The d.c. resistance of the conductor or metal screen shall be corrected to a temperature of20 °C and a 1 km length in accordance with the formulae and factors given in lEC 60228.Forscreens other than copper or aluminium, temperature coefficients and correction formulae shallbe taken respectively from Table 1 and 2.1.1 of lEC 60287-1-1:2006.
10.7.1.1 strip method
The measurement shall be made with a micrometer with plane faces of 4 mm to 8 mmdiameter and an accuracy of ± 0,01 mm.
The measurement shall be made on a test piece of lead sheath about 50 mm in lengthremoved from the complete cable.The piece shall be slit longitudinally and carefully flattened.After cleaning the test piece,a sufficient number of measurements shall be made along thecircumference of the lead sheath and not less than 10 mm away from the edge of the flattenedpiece to ensure that the minimum thickness is measured.
10.7.1.2 Ring method
The measurements shall be made with a micrometer having either one flat nose and one ballnose, or one flat nose and a flat rectangular nose 0,8 mm wide and 2,4 mm long. The ball noseor the flat rectangular nose shall be applied to the inside of the ring.The accuracy of themicrometer shall be 土 0,01 mm.
The measurements shall be made on a ring of the lead sheath carefully cut from the sample.The thickness shall be determined at a sufficient number of points around the circumference ofthe ring to ensure that the minimum thickness is measured.