AS NZS IEC 60331.2:2017 pdf free download – Tests for electric cables under fire conditions- Circuit integrity
6.2 Test specimen mounting
The test specimen shall be bent to form an approximate “U” shape. The internal radius of each bend shall be the manufacturer’s declared minimum bending radius and the overall distance between the vertical portions of the cable shall be (475 ± 1 0) mm as shown in Figure 7. The test specimen shall be mounted centrally on the wall using metal clips which shall be earthed. The lower edge of the cable shall be (200 ± 1 0) mm below the top of the test wall. P- clips made of metal strip (1 0 ± 1 ) mm wide shall support the test specimen at either end of the radiused section and in the centre as shown in Figure 7. The P-clips shall be formed so as to have approximately the same diameter as the cable under test.
7.2 Electrical connections
At the transformer end of the test specimen, earth the neutral conductor and any protective conductors. Any metal screens, drain wire or metallic layer shall be interconnected and earthed. Connect the transformer(s) to the conductors, excluding any conductor which is specifically identified as intended for use as a neutral or a protective conductor, as shown in the circuit diagram in Figure 8. Where a metallic sheath, armour or screen acts as a neutral or protective conductor, it shall be connected, as shown in the circuit diagram in Figure 8, as for a neutral or protective conductor.
For single-, twin- or three-phase conductor cables, connect each phase conductor to a separate phase of the transformer(s) output with a 2 A fuse or circuit-breaker with equivalent characteristics in each phase. For multicore cables that have four or more conductors (excluding any neutral or protective conductors), the conductors shall be divided into three roughly equal groups, ensuring that adjacent conductors are, as far as possible, in different groups. For multipair cables, the conductors shall be divided into two equal groups, ensuring that the a-core of each pair is connected to one phase and the b-core of each pair is connected to another phase (L1 and L2 in Figure 8). Quads shall be treated as two pairs. For multi-triple cables, the conductors shall be divided into three equal groups, ensuring that the a-core of each triple is connected to one phase, the b-core of each triple to another phase and the c-core of each triple to the third phase of the transformer (L1 , L2 and L3 in Figure 8.). Connect the conductors of each group in series and connect each group to a separate phase of the transformer output with a 2 A fuse or circuit-breaker with equivalent characteristics in each phase.”
NOTE 1 The above test procedure connects the neutral conductor to earth. This may not be appropriate if the cable is designed for use on a system where neutral is not earthed. If required by the cable standard it is permissible for the neutral conductor to be tested as if it were a phase conductor. Where a metallic sheath, armour or screen acts as a neutral conductor it shall always be connected to earth. Any such variations in methodology should be included in the test report.
NOTE 2 For cable constructions not specifically identified above, the test voltage should be applied, as far as is practicable, to ensure that adjacent conductors are connected to different phases.
NOTE 3 In certain cases, for example when testing a control cable using a three-phase transformer, it may not be possible to apply a test voltage between conductors and from conductor to earth equal to the rated voltage simultaneously. In such cases, either the test voltage between conductors, or the test voltage from conductor to earth shall be equal to the rated voltage, such that both the test voltage between conductors and the test voltage from conductor to earth is equal to or higher than the rated voltage.