BS/EN 3475-605-2018 pdf download.Aerospace series – Cables, electrical, aircraft use – Test methods Part 605: Wet short circuit test.
NOTE The needle wall thickness shall be selected such that the specified flow rate shall be delivered at
approximately six (6) drops per minute.
5.3 Test protocol
5.3.1 The procedure embraces copper cable sizes 001 to 051 (26 to 10) or copper clad 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 he deemed necessary in particular cases and values of prospective fault currents, the ratings of thermal breaker protection which are typical of aircraft use 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 b). The use of video recording for all tests is required.
5.4 Test rig set-u p
5.4.1 Install the rating of circuit breaker appropriate to the cable type and size to be tested (Table 3).
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 Prepare an electrolyte solution made by dissolving 3 % ± 0,5 % by weight of sodium chloride in distilled water.
5.4.4 Support the specimen in free air inclined at an angle of 100 to the horizontal with the electrical input connections at the higher end.
5.4.5 Position the delivery system so that the electrolyte contacts the loom from a height of (10 ± 2) mm above the uppermost cables in the loom at a point which shall position the droplets into the upper cut or no more than 2 mm towards the higher end of the specimen. Ensure that the drops strike the cables at the top centre of the circumference such that they fall into the crevice between cables Al and BI.
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 start the flow of electrolyte at a rate of (100 ± 10) mg/mm. Particular care shall be taken to ensure that the electrolyte flows between the damage sites as evidenced by steaming of the electrolyte and the development of scintillation. Shall this not occur, and failure of the cable to wet be determined, then the alternative surfactant described In 5.4.3 may be used.
6.1.3 Run the test continuously for a period of 2 h.
lithe circuit-breaker(s) of phases Al. A2. Bi, B2, Cl and C2 do not trip for a duration of 2 h. switch off the power supply and the electrolyte flow. Stop the test.
6.1.4 Following CB(s) tripping adopt the following procedure:
a) After not less than 3 mm, nor more than 10 mm, and with all thermal circuit breakers closed, reapply power to the specimen with no further flow of electrolyte.
b) Apply power for the time necessary for any fault condition to develop fully but do not reset the thermal circuit breakers.
6.1.5 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
EN 3197, can be used as a guideline to differentiate short-circuit and arc-tracking effects.
Noticeable damages may come from either:BS/EN 3475-605-2018 pdf download.
BS/EN 3475-605-2018 pdf download
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