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BS EN 3475-604:2018 – TC:2020 Edition

BS EN 3475-604:2018 – TC:2020 Edition

$134.27

Tracked Changes. Aerospace series. Cables, electrical, aircraft use. Test methods – Resistance to dry arc propagation

Published By Publication Date Number of Pages
BSI 2020 35
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This European standard specifies a method for appraising the behaviour of cable insulation when an electric arc is initiated and maintained by two powered cables rubbing against a blade. This European Standard shall be used together with EN 3475 100. The primary aim of this test is: — to produce, in a controlled fashion, continuous failure effects which are representative of those which may occur in service when a typical cable bundle is damaged by abrasion such that electrical arcing occurs, both between cables and between cables and conductive structure, and — to examine the aptitude of the insulation to track, to propagate electric arc to the electrical origin. Originally defined for 115 Vac network, this test also proposes conditions for 230 Vac network. Unless otherwise specified in product standard, only 115 Vac conditions shall be satisfied. Six levels of prospective fault current have been specified for concerned cable sizes (see Clause 7). It is generally agreed that larger sizes need not be assessed since the short-circuit phenomenon becomes dominant at low line impedances. Unless otherwise specified in the technical/product standard sizes 002, 006 and 020 cable shall be assessed.

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PDF Pages PDF Title
19 undefined
23 1 Scope
2 Normative references
3 Specimen requirements
24 4 Preparation of specimen
4.1 Cut seven (7) separate lengths of approximately 0,5 m consecutively from one length of cable, and strip each of the ends of insulation to permit electrical connection. Clean each length of cable with a clean cloth moistened with propan-2-ol (isopropyl alcohol) fluid.
4.2 Lay up the seven (7) cables as follows:
25 5 Apparatus
5.1 Electrical equipment
26 5.2 Test equipment
29 5.3 Test protocol
5.3.1 The procedure embraces copper cable sizes 001 to 050 (26 to 10) or aluminium cable sizes 002 to 090 (24 to 8), and for each cable size six (6) values of prospective fault current have been defined. Performance of a cable size at a given fault intensity shall be determined by testing three (3) samples. Thus 18 samples are required for every cable size.
5.3.2 For the purposes of cable qualification at least sizes 002, 006 and 020 shall be tested. Additional testing of other sizes may be deemed necessary in particular cases and values of prospective fault currents, the ratings of thermal breaker protection which are typical of aircraft use and the blade form to be employed have been included in this specification.
5.3.3 It is emphasised that electrical arcing tests are essentially destructive and can be hazardous to personnel. Therefore tests shall be undertaken with all observers shielded from direct physical and visual exposure as noted in 5.2 i). The use of video recording for all tests is required.
5.4 Test rig set-up
5.4.1 Install the rating of circuit breaker appropriate to the cable type and size to be tested (Table 3). Fit a blade to the reciprocating head of the test rig of the appropriate type shown in Figures 3a and Figure 3b.
5.4.2 Heavy duty electrical shorting connections shall be fitted in substitution of a test sample to enable prospective fault currents to be set by adjustment of resistances Rf. Because these currents would trip the thermal breakers very rapidly these shall be shunted to permit the pulsing of current until the desired value is obtained. Re-instate the thermal protection.
5.4.3 With electrical power removed adjust the test apparatus to give the correct conditions of blade stroke, frequency and downwards force. Ensure that the test fixture is correctly positioned and that the method of holding the specimen provides satisfactory restraint.
5.4.4 Modify a verification sample by removing a section of cables A1 and B1 in the test zone. Adjust the blade depth stop such that the final blade position is at least half the conductor diameter of A1 or B1, from wires A2, B2 and C1, as shown by Figure 1.
6 Method
6.1 Test procedure
6.1.1 Install a test specimen with electrical connections as shown in Figure 1 and with Rf set, as in 5.4.2 above, to give the required current from Table 1 or Table 2.
6.1.2 Apply electrical power to the specimen and gently make contact with the blade. Arm the automatic blade lifting circuit, if used, and start the abrading action.
30 6.1.3 Actuation of the abrader shall create failure effects which shall be processed as follows:
6.1.4 Repeat the test to obtain three (3) samples and then reset the circuit for the next highest current overload until all 18 samples have been tested.
6.2 Examination
32 6.3 Test report
7 Requirements

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BS EN 3475-604:2018 - TC
$134.27