IEC 60331-1:2009 pdf free download – Tests for electric cables under fire conditions – Circuit integrity
5.2Test ladder and mounting
The test ladder shall consist of a steel framework as shown in Figure 1.The two central verticalelements of the ladder shall be adjustable in order to accommodate different sizes of cableunder test. The test ladder shall be (1 200 ±100) mm long and (600 ± 50) mm high, and thetotal mass of the test ladder shall be (18±1) kg.Ballast, if required,shall be placed on thesteel supports.
NOTE 1 Angle iron approximately 45 mm wide and 6 mm thick，with suitable slots cut to allow for fixing of thebolts or saddles, has been found to be a suitable material for construction of the ladder.
Each horizontal element shall have a mounting hole not more than 200 mm from each end, theexact position and diameter being determined by the particular supporting bush and supportingframework used. The test ladder shall be fastened to a rigid support by four bonded rubberbushes of hardness 50-60 Shore A fitted between the horizontal steel elements of the ladderand the support framework,as shown in Figures 1 and 2 so as to allow movement underimpact.
NOTE 2 A typical rubber bush, which has been found to be suitable, is shown in Figure 4.
6.2Test specimen mounting
The test specimen shall be bent to form an approximate arc of a circle. The internal radius ofthe bend shall be the manufacturer’s declared minimum bending radius.
The test specimen shall be mounted centrally on the test ladder, as shown in Figure 7, usingmetal clips which shall be earthed.Two U-bolts on the upper horizontal element of the ladderare recommended, but P-clips made of metal strip (20 ±2) mm wide for cables from 20 mm upto 50 mm in diameter，and (30 ± 3) mm wide for larger cables shall be used on the centralvertical elements.The P-clips shall be formed so as to have approximately the same diameteras the test specimen under test.
lf the test specimen is too small to be mounted on the central vertical elements when in theposition shown in Figure 7, the vertical elements shall be equally moved towards the centre sothat the specimen may be mounted as shown in Figure 8.
specifically identified as intended for use as a neutral or a protective conductor，as shown inthe circuit diagram in Figure 9. Where a metallic sheath,armour or screen acts as a neutral orprotective conductor,it shall be connected, as shown in the circuit diagram in Figure 9,as fora neutral or protective conductor.
For single-,twin- or three-phase conductor cables，connect each phase conductor to aseparate phase of the transformer(s) output with a 2 A fuse or circuit-breaker with equivalentcharacteristics in each phase.
For multicore cables that have four or more conductors (excluding any neutral or protectiveconductors), the conductors shall be divided into three roughly equal groups，ensuring thatadjacent conductors are, as far as possible, in different groups.
For multipair cables， the conductors shall be divided into two equal groups,ensuring that thea-core of each pair is connected to one phase and the b-core of each pair is connected toanother phase (L1 and L2 in Figure 9).Quads shall be treated as two pairs.
For multi-triple cables，the conductors shall be divided into three equal groups，ensuring thatthe a-core of each triple is connected to one phase, the b-core of each triple to another phaseand the c-core of each triple to the third phase of the transformer(L1,L2 and L3 in Figure 9).
Connect the conductors of each group in series and connect each group to a separate phase ofthe transformer output with a 2 A fuse or circuit-breaker with equivalent characteristics in eachphase.
NOTE1 The above test procedure connects the neutral conductor to earth. This may not be appropriate if thecable is designed for use on a system where neutral is not earthed. lf required by the cable standard,it ispermissible for the neutral conductor to be tested as if it were a phase conductor. Where a metallic sheath,armouror screen acts as a neutral conductor, it shall always be connected to earth.Any such variations in methodologyshould be included in the test report.
NOTE2 For cable constructions not specifically identified above, the test voltage should be applied, as far as ispracticable, 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 bepossible to apply a test voltage between conductors and from conductor to earth equal to the rated voltagesimultaneously. in such cases, either the test voltage between conductors, or the test voltage from conductor toearth shall be equal to the rated voltage, such that both the test voltage between conductors and the test voltagefrom conductor to earth is equal to or higher than the rated voltage.