ASD-STAN PREN 3475-307-2011 Aerospace series Cables electrical aircraft use Test methods Part 307 Corona extinction voltage (Edition P 3).pdf

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1、ASD-STAN STANDARD NORME ASD-STAN ASD-STAN NORM prEN 3475-307 Edition P 3 November 2011 PUBLISHED BY THE AEROSPACE AND DEFENCE INDUSTRIES ASSOCIATION OF EUROPE - STANDARDIZATIONAvenue de Tervuren, 270 - B-1150 Brussels - Tel. 32 2 775 8126 - Fax. 32 2 775 8131 - www.asd-stan.orgICS: Supersedes editio

2、n P 2 of June 2009 and will supersede EN 3475-307:2010Descriptors: ENGLISH VERSION Aerospace series Cables, electrical, aircraft use Test methods Part 307: Corona extinction voltage Srie arospatiale Cbles, usage aronautique Mthodes dessais Partie 307 : Tension dextinction corona Luft- und Raumfahrt

3、Elektrischen Leitungen fr Luftfahrt Verwendung Prfverfahren Teil 307: Korona-Aussetzspannung This “Aerospace Series“ Prestandard has been drawn up under the responsibility of ASD-STAN (The AeroSpace and Defence Industries Association of Europe - Standardization). It is published for the needs of the

4、 European Aerospace Industry. It has been technically approved by the experts of the concerned Domain following member comments. Subsequent to the publication of this Prestandard, the technical content shall not be changed to an extent that interchangeability is affected, physically or functionally,

5、 without re-identification of the standard. After examination and review by users and formal agreement of ASD-STAN, it will be submitted as a draft European Standard (prEN) to CEN (European Committee for Standardization) for formal vote and transformation to full European Standard (EN). The CEN nati

6、onal members have then to implement the EN at national level by giving the EN the status of a national standard and by withdrawing any national standards conflicting with the EN. Edition approved for publication 1 November 2011 Comments should be sent within six months after the date of publication

7、to ASD-STAN Electrical Domain Copyright 2011 by ASD-STAN prEN 3475-307:2011 (E) 2 Contents Page Foreword 2 Introduction .3 1 Scope 4 2 Normative references 4 3 Terms and definitions .4 4 Applicability 4 5 Apparatus .5 6 Methods 5 6.1 General 5 6.2 Method A .5 6.3 Method B .6 7 Procedure .7 8 Require

8、ment .8 Foreword This standard was reviewed by the Domain Technical Coordinator of ASD-STANs Electrical Domain. After inquiries and votes carried out in accordance with the rules of ASD-STAN defined in ASD-STANs General Process Manual, this standard has received approval for Publication. prEN 3475-3

9、07:2011 (E) 3 Introduction For an electrical cable, the presence of partial discharges effects at operating voltage may result in a significant reduction of service life. Some insulation materials are more susceptible to such discharge damage than others. Evidence of partial discharges during operat

10、ion signifies for example: the insulation thickness is insufficient for the applied voltage; the quality of the insulation is inadequate possibly due to excessive size or quantities of internal cavities or voids; an overstress is present, resulting in a local reduction of the cable insulation proper

11、ties. Significant parameters may influence PDIV and PDEV such as pressure, temperature, humidity, previous electrification, input signal characteristics (sine wave, voltage rate, .). Attention shall be given to installation conditions in A/C, for example excessive bending or surface wrinkling of ins

12、ulation shall be avoided. Up to few tens of kHz frequency can be considered as non-significant parameter. prEN 3475-307:2011 (E) 4 1 Scope This test standard defines methods to cover the detection and measurement of partial discharge (corona) under an applied test voltage, including the determinatio

13、n of partial discharges (corona) inception and extinction voltages as the test voltage is raised and lowered, of electrical cables for aircraft use. It shall be used together with EN 3475-100. 2 Normative references The following referenced documents are indispensable for the application of this doc

14、ument. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 2235, Aerospace series Single and multicore electrical cables, screened and jacketed EN 3475-100, Aerospace series Cables, electri

15、cal, aircraft use Test methods Part 100: General EN 60270, High-voltage test techniques Partial discharge measurements ASTM D 1868, Standard Test method for Detection and Measurement of Partial Discharge (Corona) Pulses in Evaluation of Insulation Systems 1) 3 Terms and definitions For the purposes

16、of this document, the following terms and definitions apply. 3.1 Partial Discharge Inception Voltage PDIV lowest voltage at which continuous (steady state with a minimum of 1 detected Partial discharge per second) partial discharges occur as the applied voltage is increased 3.2 Partial Discharge Ext

17、inction Voltage PDEV highest voltage at which partial discharges no longer occur as the applied voltage is decreased from the inception voltage described before NOTE More precise information on the partial discharge phenomenon, such as definition, can be found in ASTM D 1868-07 or in EN 60270. 4 App

18、licability This test method is suitable for coaxial cables, high voltage cables and for thin wall insulated cables. Methodologies are proposed to cover: coaxial cables (Method A), wires used in altitude (Method B). 1) Published by: ASTM National (US) American Society for Testing and Materials http:/

19、www.astm.org/.prEN 3475-307:2011 (E) 5 5 Apparatus The equipment shall be capable of detecting partial discharges of five picocoulombs or less. The detection equipment, cautions and measurement procedures shall be equivalent to those described in ASTM D 1868 or in EN 60270. The frequency of the test

20、 voltage shall be between 48 Hz to 62 Hz. 6 Methods 6.1 General Two methods are proposed according to specific needs. Unless otherwise specified in the concerned product standard Method A applies. The minimum specimen length shall be chosen so that its capacitance is matched to the needs of the dete

21、cting equipment to permit observation of discharges of the level described in Clause 5. Use ASTM D 1868 for guidance to determine this length. In any case the minimum length under test shall not be less than 850 mm. It is particularly important that the ends of specimen to test and that the test ben

22、ch are corona free. WARNING Lethal voltage may be present during this test. It is essential that procedures and test apparatus are properly defined and used for safe operation. 6.2 Method A 6.2.1 Case of use This method is particularly dedicated to measure PDEV of coaxial cables, under ambient condi

23、tions. 6.2.2 Specimen preparation A suggested method for making the ends corona free is shown on Figure 1 to Figure 3. Step 1: If compatible with Clause 6 above, suggested length of cable specimen is 1 m. Step 2: Remove 75 mm of the jacket material from each end. Dimensions in millimetres Figure 1 p

24、rEN 3475-307:2011 (E) 6 Step 3: Roll back the braid over the jacket and trim as shown. Be careful to avoid breaking any strands. Trim the braid edges nearly to 25 mm lengths. Dimensions in millimetres Figure 2 Step 4: Trim one end of the specimen to the dimensions shown and cover the braid edge and

25、jacket with a plastic tube or adhesive tape or heat-shrink sleeve as shown. On the other end, wrap a gauge 20 coated copper grounding wire tightly over the braid or use an equivalent grounding method. Dimensions in millimetres Figure 3 6.3 Method B 6.3.1 Case of use This method is particularly dedic

26、ated to single wires, without screen, used in altitude (low pressure) in non-pressurized areas under particular temperature conditions. 6.3.2 Specimen preparation Specimens must be prepared as described in 6.2.2, with the addition of a braid, as close as possible to the wire insulation without any r

27、isk of superficial damage. Strip the two ends. Add a braid on the whole cable length as per EN 2235. Step 1: position the braid so that about 75 mm (depends of test bench) are not shielded on both sides so that no partial discharges are created between specimen and test bench. Step 2: bend the cable

28、 so that the bending radius is for four times the cable diameter. Maintaining of the loop shall not be source of crushing nor twisting. See Figure 4. Step 3: use heat shrinkable sleeves (or equivalent) on both extremities to stop the braid and avoid any partial discharge generation at this level. pr

29、EN 3475-307:2011 (E) 7 Step 4: join extremities of the braid, twist them, and join them to the extremity of the grounding method NOTE Temperature acceptable by additional materials shall be compatible with temperature called for this test by the concerned product standard. Measurements shall be made

30、 between joined ends of the wire and the end of the grounding method. Then each specimen shall be put in a vacuum chamber where required pressure and temperature can be obtained. Figure 4 7 Procedure Before to connect the cable test specimen to a voltage source, using the selected connection devices

31、, calibrate and measure the maximal PDIV of the bench test. This value shall be far beyond (around three times) the cable test specimen PDIV value. After cable preparation, connect the test specimen to the voltage source. For methods A, both ends may be immersed in insulating oil to prevent corona d

32、ischarge at the ends. For method B, the use of sharp gripping devices such as alligator chips is forbidden. Generally PDIV and PDEV tests shall be performed at room ambient conditions (Method A), except when specified in the concerned product standard with a specified altitude or equivalent reduced

33、pressure and temperature (Method B). Apply test voltage at a maximum rate of 50 V/s to specimens having a specified PDEV of 3 kV or less and 100 V/s for specimens having a specified PDEV above 3 kV, until the detector indicates a sustained corona discharge PDIV or reaches two times the specified cor

34、ona extinction voltage PDEV. NOTE A first rise of voltage is necessary to activate the electron form (important to engage the phenomenon of partial discharges), which occurs at a voltage level higher than PDIV. 75mm min. prEN 3475-307:2011 (E) 8 The cable test specimen shall be subjected to graduall

35、y increasing sinusoidal voltage until the detector indicates a sustained corona discharge. Take the value of the PDIV when the partial discharges are continuous during more than one second. If sustained corona discharge PDIV is indicated, the voltage shall then be decreased slowly until the corona e

36、xtinction point PDEV is observed. The corona extinction voltage PDEV is defined as the voltage at which sustained discharge ceases. If sustained partial discharges have not been observed at two times the specified partial discharges extinction level PDIV, the requirement is considered to have been satisfied. Unless otherwise specified in the concerned product standard, at least three different specimens shall be tested. 8 Requirement When required, PDEV and/or PDIV shall be within the limits indicated in the product standard.