IEC TR 61901-2005 pdf – Development tests recommended on cables with a longitudinally applied metal foil for rated voltages above 30 kV (U m = 36 kV)

IEC TR 61901-2005 pdf – Development tests recommended on cables with a longitudinally applied metal foil for rated voltages above 30 kV (U m = 36 kV).
1 Scope This technical report details the tests recommended for use when cables with a longitudinally applied metal foil are being developed. The tests in this technical report are grouped as follows: – tests on cable components (see Clause 2); – first set of tests on completed cables (see Clause 3); – second set of tests on completed cables (see Clause 4); – third set of tests on completed cables (see Clause 5). 2 Tests on cable components Specimens for control measurements should be removed from cable samples before any tests. Specimens should also be removed from cable samples after the following tests: – bending test (see 3.2); – heating cycle test (see 3.3); – water penetration test (see 3.4); – corrosion test (see 3.6); – short-circuit test (see Clause 4); – sidewall pressure test (see 5.2). The adhesion strength and the peel strength of the overlapped metal foil should be measured using the procedures of IEC 60840, G.2.1 and G.3.1 respectively. 3 First set of tests on completed cables 3.1 Test sequence The sequence of tests is summarised in Figure 1 below.
3.2 Bending test The bending test should be performed in accordance with IEC 60840, 1 2.3.3. A 1 m sample should then be taken from the cable length and subjected to a visual inspection (see 3.7). 3.3 Heating cycle test The test should be performed in accordance with IEC 60840, 1 2.3.6, except that no voltage is applied to the cable. A 1 m sample should then be taken from the cable length and subjected to a visual inspection (see 3.7). 3.4 Water penetration test This test should be performed in accordance with IEC 60840, 1 2.4.1 8, when applicable. The sample should then be subjected to a visual inspection (see 3.7).
One impact should successively be made at five different points along the cable, the distance between two impact points should be at least 1 00 mm. Two samples should be subjected to the test: − one for a corrosion test (see 3.6); − one for visual inspection (see 3.7). 3.6 Corrosion test A 1 m sample should be placed in a solution of 1 % NaCl, 1 % Na 2 SO 4 with NaOH added to adjust the pH of the solution to (8,5 ± 0,5). The solution should be maintained at (70 ± 3) °C during the test. The cable with both ends sealed should be immersed at a depth of at least 0,5 m. The cable sample should be removed from the solution after 3 000 h immersion and the metal foil inspected (see 3.7).
3.7 Visual inspection A 1 m sample should be dissected and visually examined. Examination of the samples with normal or corrected vision without magnification should reveal no cracks or separation of the metal foil of laminated protective coverings or damage to other parts of the cable. After the corrosion tests (see 3.6), there should be no signs of corrosion of the metal foil. 4 Second set of tests on completed cables 4.1 Test sequence The sequence of tests should consist of a short-circuit test followed by inspection (see 3.7). 4.2 Short-circuit test The short-circuit test should be performed on a cable at least 1 5 m long. The metal foil should be connected to the metallic screen, if any, as in service. The short-circuit current should be applied to flow through the cable conductor and return through the metal foil and the metallic screen. The maximum duration should be 2 s so that the temperature of the metallic screen should reach the temperature specified in IEC 61 443, Table 2. The application of short-circuit current should be repeated five times on the same sample. The interval between short-circuits should be long enough to allow the metallic screen to cool to a temperature less than 20 K above its temperature prior to the first short-circuit. 4.3 Visual inspection A 1 m sample should then be subjected to a visual inspection (see 3.7). There should be no signs of overheating. 5 Third set of tests on completed cables 5.1 Test sequence The sequence of tests is summarised in Figure 3 below.