IEC 60840:2020 pdf free download – Power cables with extruded insulation and their accessories for rated voltagesabove 30 kV(Um = 36 kV) up to 150 kV(Um= 170 kV)-Test methods and requirements
10.2 Frequency of tests
The sample tests in items a) to h) and k) of 10.1 shall be carried out on one length from eachbatch (manufacturing series) of the same type and cross-section of cable, but shall be limitedto not more than 10 % of the number of lengths in any contract, rounded to the nearest wholenumber.
The frequency of the tests in items i) and j) of 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 greater than 20 km.
10.3 Repetition of tests
lf the sample from any length selected for the tests fails in any of the tests in 10.1, 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. If both additional samples pass the tests, theother cables in the batch from which they were taken shall be regarded as having complied withthe requirements of this document. lf 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, or the declaredconstruction, shall be checked by inspection and measurement when practicable.
10.5Measurement of electrical resistance of conductor and metal screen
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 can be measured on a sample of conductor or metal screen, conditioned for atleast 1 h in a temperature-controlled liquid bath.
The DC resistance of the conductor or metal screen shall be corrected to a temperature of 20 °cand 1 km length of cable in accordance with the formulae and factors given in IEC 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.
The corrected Dc resistance of the conductor at 20 °C shall not exceed the appropriatemaximum value specified in lEC 60228 or, when a value for maximum DC conductor resistanceis declared in Clause 6 d), then the corrected DC resistance of the conductor at 20 °C shall notexceed the declared value.
The corrected DC resistance of the metal screen at 20 °C shall not exceed the declared value.10.6Measurement of thickness of cable insulation and oversheath
10.6.1 General
The test method shall be in accordance with lEC 60811-201 for the insulation.For theoversheath the test method inaccordance with IEC 60811-202:2012 andIEC 60811-202:2012/AMD1:2017 shall be applied, except that for sheaths where the underlyingsurface is not irregular the measurement may be made with a micrometer having a ball noseradius of 2,5 mm to 3 mm.The accuracy of the micrometer shall be +0,01 mm.
Each cable length selected for the test shall be represented by a piece taken from one end afterhaving discarded, if necessary, any portion that may have suffered damage.